This PDF file contains the front matter associated with SPIE Proceedings Volume 11043, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists.

Luminescent compounds and materials have numerous uses. The emission properties, whether of a fast decay rate fluorescent material or a slow decay rate phosphorescent material, are defined by the chemical composition and the physical structure of the luminescent material. The crystal field that is determined by the environment in the host material in combination with the various dopant ions with the correct valence state can be used to obtain emissions from the Ultra violet (UV) to the infra-red (IR) wavelength ranges. With the development of flat panel displays and light emitting diodes, phosphor materials became an integral part of our life style. Luminescent compounds and materials also have numerous other uses such as temperature sensors, radiation dosimeters, optical probes, storage phosphor imaging, medical imaging, microscopy techniques, homeland security, detecting tools of biological structures and can possibly be used as efficient improvement of solar cells. Examples of the uses of the phosphor materials are given to emphasise the importance of these materials in our daily life.

Key issues for flexible electronics are low temperature processing, cost-efficient semiconducting and dielectric materials, and sufficient performance of the integrated TFT devices. To achieve high performance flexible circuits, contact resistances of today’s transistors must be reduced. Additionally, the parasitic overlap capacitances between the transistor’s electrodes need to be minimized. The inverted staggered transistor setup with self-aligned gate fulfills these requests. Nevertheless, the integrated devices suffer on poor AC characteristics due to limited performance of the common gate dielectric layers. The gate voltage has no direct access to the semiconductor surface, either due to rechargeable surface states and polarization effects or because of low-k values. Consequently, new flexible high-k dielectrics must be implemented in TFT device integration.

We report on the characterization of an epitaxial layer of InAs_0.94Sb_0.06 grown on semi insulating GaAs by metal organic vapour phase epitaxy (MOVPE). Transmission electron microscopy, x-ray diffraction, photoluminescence and photoconductivity spectroscopy were used to characterize the layers in terms of its structural and luminescent properties, with emphasis on residual stress/strain, extended defects like dislocations, band gap energies and impurity states. Temperature dependant Hall measurements were also performed. The composition of the layer as well as strain relaxation was confirmed by High resolution X-ray diffraction. Photoluminescence produced a broad emission peak which was shown to be a convolution of extrinsic recombination and band-to-band transitions. A comparison between photoluminescence and photoconductivity results confirmed this analysis. The absorption edges, determined from photocurrent spectroscopy measurements at different temperatures, were fitted with an Einstein single oscillator model, yielding a 0 K band gap energy of 355 meV. Hall mobility results showed a peak mobility of 9.5 × 10³ cm² /V.s at 115 K; results were fitted with a two-layer Hall model yielding a bulk peak mobility of 22.4 × 10³ cm² /V.s at 88 K, with a majority donor carrier concentration of roughly 5 × 10^-15 cm^-3. These results continue to show that InAs_1-xSb_x has great potential for use within mid-wave infrared detectors, however further improvement in deposition growth is still needed for final device manufacture.

The silicon avalanche-mode light-emitting diode (AMLED) opens a route for on-chip opto-electronic applications in standard CMOS, both due to its relatively broad spectral overlap with the spectral responsivity of silicon photodiodes and due to its high speed capability. This work presents closed form models for the key figures of merit (FOMs) of AMLEDs, namely, current (or power) density, cut-off frequency, radiative efficiency, and specifically for optical data communication energy cost per photon. Their derivations are based on one-dimensional analyses of an abrupt single-sided (p⁺n or n⁺p) junction and of a p-i-n diode. TCAD simulations for optimized device structures, including the recently reported superjunction (SJ) LED, were performed to validate the model. Measurements on single-sided abrupt junctions and SJ diodes are shown to validate some of the modelled trends. The results show that a p-i-n or an SJ diode is favorable to a conventional single-sided junction diode for the AMLED design. In addition, as confirmed for conventional AMLEDs by earlier reports, the results indicate that for a yet higher efficiency the carrier supply should be increased. For this a combination of a separate minority carrier injector and SJLED is proposed, referred to as the injection-avalanche CMOS SJLED. However, more experimental optical data (e.g., absolute photon flux) are needed for a more accurate model validation.

The light emission from silicon PureB photodiodes was investigated in both forward- and avalanchemode operation and correlated to the presence of process-dependent defects that influence the reverse IV characteristics. As opposed to “defect-free” diodes with low dark currents and abrupt breakdown behavior, the diodes with defects had higher current levels and light-emitting spots appearing at voltages far below the breakdown voltage otherwise set by the implemented doping profiles. The role of such defect-related behavior for the application of the photodiodes as single-photon avalanche diodes (SPADs) and avalanche-mode light-emitting diodes (AMLEDs) is assessed in connection with the recent demonstration of these basic devices as both the light-emitting and light-detecting elements in optocoupler circuits integrated in CMOS for data transmission purposes.

Light emission in silicon LEDs that operate in the avalanche mode of operation, was analyzed by appropriate modelling, including the silicon energy band structure, available carrier energy spread, and available carrier momentum spread. These mechanisms play key roles in the realization of light emitting, using standard silicon processing procedures. The analyses indicate that appropriate doping and controlling the energized specifically electrons, carrier energy and carrier density by field manipulation, and controlling carrier momentum through appropriate impurity scattering technology, show great potential to enhance these emissions. Particularly, development work conducted on the p+np+ mono-silicon LED and the N+PN+PN+ Poly silicon LED show that field control, impurity and defect scattering and balancing the carrier type and carrier density has a profound influence on the optical emission intensity in Si AMLEDs. Furthermore, a much clearer understanding of the mechanisms responsible for optical emissions in Si Av LEDs has been obtained and can proceed with further improved device designs and applications.

Si LEDs that operate in the reverse avalanche mode (Si AM LED) and forward bias (Si FB LED), offer various possibilities for realizing nano and micro biosensors directly on chip. The LEDs operate in 450 - 1100nm wavelength range, can emit up to 100nW of optical power, and can be fabricated in micro and nano dimensions. The dispersion characteristics has been studied for a Si AM LED source that is positioned one micron below silicon surface. Subsequently, a fluidic channel sensor device has been designed using the dispersion characteristics. Hence transmittance and absorption spectra studies of species that flow in a fluidic channel can be studied. Similarly, a waveguide-based sensor device has been designed where a receptor layer is fabricated on a waveguide on chip between a Si AM LED and a Si p-i-n detector. The receptor layer binds preferentially with a defined pathogen, and couples with the evanescent radiation of the waveguide.

A novel silicon SiGe edge light emitting diode (SiGe ELED) was realized in standard RF bipolar SiGe technology process that uses a p-n junction either in reverse and forward bias mode configurations. A vertical cubical columnar SiGe/Si HBT like structure was used. The light emitting process in the reverse bias mode is by means of an avalanche breakdown process. The reverse biased device emits light in the wavelength range of 450–650 nm, with operating voltage and current of 1.3 V and 8 mA respectively, while the forward biased mode emitted at about 850nm. In the forward biased mode, it operates in a two junction mode with the first n+p junction emitting low energy electrons into a lowly doped p region. The SiGe ELED is intended to be implemented in an optical interconnect with an external detector via a lateral optical waveguide coupling. Because the LED emit in a broad spectrum, localizing the emission source point is of paramount importance. Two techniques were used to attempt to realise this objective. Optical Probe measurement and Optical Power Meter Mapping technique. Localization of the emission source point process was performed through scanning a lensed fiber coupled to an optical power meter, over the edge surface profile of the diced device. The side edge of the diced device structure was interface with the lens fibre in other to ascertain the maximum emission point and the nature of light emitting process. This was done using a smooth dicing of the LED device close to its emitting edge and scanning its edge surface through a multimode lensed fiber coupled to an optical power meter. The mapping area scanned was 40μm x 40μm and 60μ x 60μ to localize the emitting source point region. A total emitted optical power as measured from the Led was 2.86nW as measured by the optical power meter connected to the lensed optical fibre. This was confirmed with a light-current-voltage (LIV) characteristics power measurement curve obtained from the device by means of the edge mapping techniques. A rough estimated localization of the source point was approximately 0.3mW optical power with a current of 8mA was realized with this technique. These results can be used to design accurate electro-optical conversions in integrated photonic circuitry as well as designing well coupled optical interconnects from the chip to the environment.

The focal plane array in an MWIR camera should be configured optimally in terms of readout mode, stare time and gain setting to achieve the best (minimum) noise levels and/or maximal usable dynamic range under variable environmental conditions. In a long-range observation system noise is normally dominated by the environment, with optical contributions due to ambient illumination, target and background radiance, atmospheric transmission, path radiance, optics transmission and optics radiance. This optical signal is then detected according to the FPA spectral responsivity, which, combined with electronic contributors such as read noise, amplifier noise, clock noise, and quantization noise, eventually result in a digital output signal. A complete radiometric system modelling approach is used to predict the system NETD under a variety of representative environmental conditions and target ranges, which can then be used to inform decisions regarding the selection of the detector readout mode and gain mode, as well as setting the stare time for best operational performance. Results are presented demonstrating the effects of the various environmental factors and system parameters on NETD.

With the emergence of Shortwave Infrared (SWIR) InGaAs detector arrays, designers of electro-optical imaging systems can take advantage of the reduced Rayleigh scattering of the SWIR band when compared to visible, resulting in higher contrast images through haze, mist, rain, fog and challenging atmospheric conditions. Furthermore, from a military standpoint, SWIR is invisible to the human eye, thus enabling covert operations and is a good choice for targeting with laser rangefinders and designators that transmits between 1060 nm and 1570 nm. A SWIR sensor can also be used in night vision applications taking advantage of an atmospheric phenomenon called night sky radiance (or night glow) that emits five to seven times more illumination than starlight, nearly all of it in the SWIR wavelengths. In a typical airborne application a sensor’s performance is mechanically constrained by the space/volume available and the aperture size limit. This paper describes a model based trade-off methodology to select the optimal Field of View (FOV) for an aperture limited SWIR sensor. This method balances the influences FOV has on sensitivity and resolution. The SWIR sensor’s performance is optimized within mechanical constraints and for the intended application scenarios. In the SWIR band the analysis is expanded to include night time scenarios and laser “see-spot” performance. This model is also adapted for input variable compliance with the industry standard NV-IPM range performance model1 enabling cross-correlation between the two model’s results. An example of a SWIR sensor analysis applying this design model is presented, highlighting the performance advantages that can be gained by maximizing the aperture utilization and choosing the optimal FOV for an imaging sensor when used in airborne targeting applications.

In this paper, a CMOS image detector array is presented that can convert a photocurrent generated by light falling onto a photodiode to a measurable output frequency. The designed array consists of 64 pixels, each containing an n⁺ -p⁺ /psubstrate photodiode along with all signal-to-frequency conversion circuitry. The 8x8 array was designed using the ams 350 nm process, with each individual pixel occupying an area of 30×30 μm² . Measurements on the fabricated array show that a dynamic range of 10 - 15 dB can be achieved with a maximum output frequency of 125 kHz. Work was done to increase the output driving capability of the array to increase the dynamic range of the pixel in simulations to 54 dB. Further research will also investigate ways of implem

Inkjet-printing supports environmentally friendly manufacturing of printed electronics and enables rapid prototyping with low material waste. In this work, inkjet-printed conductive tracks on ethyl 2-cyanoacrylate (superglue) is compared to tracks printed on paper. This work will provide solutions for disposable biosensing, where the biocompatibility of versatile superglue is important. The emphasis throughout the work is on developing a biocompatible device. Dog-bone structures with different line widths were printed on paper and superglue, providing comparative results obtained from dimensional and electrical characterisation. On average the tracks printed on superglue have a 2.6 times higher resistivity than those printed on paper, but are acceptable for printed electronics networks. When considering a lumped component ac model, the 500 μm tracks on superglue have a series inductance of 2.6 nH, while the 4-point Kelvin probe characterisation of the 100 μm and 250 μm tracks printed on superglue show a capacitive equivalent impedance with capacitance values of 2.8 μF and 2.6 μF respectively. The 100 μm, 250 μm and 500 μm tracks printed on paper have inductance values of 1.20 nH, 11.30 nH and 14.8 nH, respectively. All printed tracks have linear frequency operational ranges larger than 1 MHz. A biocompatibility test was performed with Escherichia coli (E. coli) O157:H7. The silver nanoparticle ink proved to be antibacterial, while paper, superglue and gold nanoparticle ink was biocompatible. These results provide information assisting the design process for bio applications that require conformal and multi-substrate printing.

A Metal-Insulator-Metal (MIM) capacitor was inkjet-printed, using a dielectric ink (Ink-Epo-XP from MicroResist) based on SU-8 photo-resist, as well as silver nanoparticle ink (Harima NPS-J) for conductive features, which was integrated into a microsystem power supply. It was discovered that printing MIM capacitors on photo-paper had the most promising results in terms of acceptable capacitance density and flexibility, when compared to transparency and glass substrates. A core aspect considered in this project was the discovery of the workflows best suited to print MIM capacitors, which included using oxygen plasma treatment and the printing of various layers. Capacitors with values ranging between 10 and 50 pF were integrated into AC-DC and DC-DC converters. The AC-DC converter had a power output of up to 8.75 W with an output voltage of 5 V, whereas the DC-DC converters had outputs of up to 200 mW at voltages ranging between 1.8-3.3 V. The converters realised reached efficiencies of 80.77 % (AC-DC) and 70-92 % (DC-DC) respectively.

This paper presents the development of design software for inkjet-printed resistor structure layout, which con- tributes to rapid prototyping of good quality printed electronics circuits. The synthesis software was implemented using the Java SE Development Kit 8 and provides a GUI front end and automated design of resistive structures for ease of use. Several layout configurations synthesized for inkjet-printed nanosilver resistors were validated over a range of 1 Ω to 200 Ω. In doing so, Harima NPS-JL silver nanoparticle ink was characterized for sheet resistance and TCR. The software was able to synthesize resistive structures with a worst-case error of 19%, and thus, has the potential to produce practical structures for use in real world applications, such as a printed heating element for a thermal petri dish incubator.

Inkjet-printed capacitive circuits on different substrates will be investigated. This work will contribute towards rapidly prototyping electronic systems for smart ubiquitous biosensors. These biosensors require sensitive and robust signal readout with low power consumption and wireless connectivity while also being inexpensive. Capacitors were printed on different substrates, including glass and overhead projector film, to characterize an inkjet-printed dielectric. A Fujifilm Dimatix DMP2831 was used to print different functional inks, including Harima silver nanoparticle ink and InkEpo-XP ink. The silver nanoparticle ink was used to print the conductive features of the capacitors while the InkEpo-XP was used as the dielectric material. Different test patterns were printed with silver ink on the dielectric material; these patterns were used to establish a printing protocol for successful printing of silver on the dielectric material. Different test patterns were also printed with dielectric ink on silver to create a printing protocol for successfully printing dielectric on silver. Metal-insulator-metal capacitors were successfully inkjet printed on glass and overhead projector film with silver and dielectric inks. The metal-insulator-metal capacitors were used to characterize the dielectric material at different frequencies. The circuit modelling of the capacitors is discussed, and validated against experimental results. A design procedure is presented for reliably printing capacitive networks with feature dimensions between 1 mm and 2 mm on glass and overhead projector film.

This paper presents a printed paper-based origami electrochemical sensor for the detection of heavy metals in water. Heavy metal contamination in water has significant health risks and environmental complications. The detection is typically performed in a laboratory with lengthy result turnaround times. Paper-based detection provides an ideal platform on which to develop solutions to address these challenges, particularly for under-resourced settings, as it is inexpensive, disposable, and can be deployed at the point-of-need to provide rapid results for environmental and disease control. The paper-based origami device was successfully fabricated using wax printing techniques to print the hydrophobic barriers and screen printing techniques to print the three-electrode electrochemical sensor on chromatography paper. An origami design enables enhanced fluidic control to be achieved, as the porous paper structure facilitates flow, and filters out all potential debris in the sample before reaching the sensor. Vertical as well as horizontal fluidic flow is realized using the folding origami design, allowing for better filtering of debris. The results demonstrate the filtering of debris from dirty water and the detection of parts per billion levels of lead and cadmium ions in buffer solution on a single two-dimensional electrochemical sensor printed on chromatography paper. The detection results of lead and cadmium ions on chromatography paper were compared to commercially available screen-printed ceramic electrochemical sensors. The proposed paper-based origami electrochemical sensor device with fluidic handling capabilities demonstrates a simple, low-cost, disposable paper device suitable for the detection of heavy metals in water samples.

The internet of things (IoT) has resulted in accelerated development of intelligent and connected devices. Important modules include those for monitoring of environmental parameters and sensors for health diagnostic applications. Flexible, low-cost implementations are desirable towards free-form, customizable and disposable solutions for sensing and wireless connectivity. This work presents a flexible, low-cost, printed wireless temperature logger, utilizing a sensing radio frequency identification (RFID) integrated circuit (IC). The temperature logger devices were screen printed and assembled on low-cost, flexible vinyl adhesive substrates for ease of mounting on to a variety of surfaces and objects, and were tested with both coin cell batteries and screen printed primary batteries designed and manufactured in-house. The SL900A RFID IC (AMS, Austria) has internal features to monitor temperature and battery voltage. The chip was set up to log the battery voltage and the temperature over different time frames in controlled temperature environments to test the reliability of the temperature readouts. In addition, logging of the battery voltage levels enabled the performance of the printed batteries to be assessed. The results showed accurate readings over 4 days for both coin cell and printed batteries without limiting the data logging capabilities. The printed wireless temperature logger shows promise towards all-printed, low-cost solutions for environmental monitoring using an integrated and connected device approach with on-board power.

Paper-based biosensors are used in the field for their low cost and disposability. Their results are often Boolean, however quantitative results would improve derived outcomes. Devices exist which use colorimetry or spectroscopy to extract this data, however they are often bulky, expensive, and specific to the type of assay being performed. The aim of this project was to design a low-cost, portable, and easy to use image-sensing device to optically capture and log results from activated paper-based assays. Markings printed on the assays aid with detection of the assay type. This provides a system extensible to assays of various shapes and sizes. New assays can easily be created and uploaded to the device. Measurements can be taken from up to 30 cm away from the sensor. Once captured, the reaction areas are identified, and the colour intensities are measured to a resolution of 7 bits. Calibration curves are then used to convert these intensities to appropriate units.

The development of an on-chip sensor module using CMOS floating-gate transistor (FGT) technology which can be heterogeneously integrated onto existing microsystem sensor platforms was performed. The device sensitively transduces signals from functionalised sensing electrodes, which provides a customisable platform for advances in selective sensor systems. This project further presents the process development of integrating CMOS chips into flexible printed electronics microsystems sensor modules, which provide reliable electrical chip connections, as well as functionality for liquid sample usage. On-chip CMOS microsystems integrated with printed electronics enables cost sensitive point-of-care systems. The integrated microsystems sensor module answers to the steady rise in demand towards manufacturing costeffective miniaturised systems with smart features.

This paper presents inductor design via ink-jet printing techniques for planar and multi-planar inductors while considering flexible substrates. These inductor designs can be adapted for use in high frequency filtering and power transfer in microelectronics. For these inductor designs, silver nanoparticle ink (Harima MPS-JL) was ink-jetted and cured on photo paper using a Dimatix DMP-2850 printer in order to construct spiral as well as meander printed inductors. The spiral inductor designs constructed consider both planar and multi-planar formats for both square and circular geometries whereas the meander inductor designs are strictly planar. The operational bandwidth of these inductors were limited to 10 MHz in order to compare design outputs such as quality factor, inductance and impedance. Subsequent testing, in order to demonstrate both high frequency filtering as well as power transfer, using auxiliary circuits was done.

A two junction micro p+-np+ Silicon Avalanche based Light Emitting Device (Si AM LED) structure was analyzed in terms of dispersion emission characteristics, resulting in different wavelengths of light (colors) being emitted at different angles from the structure. Si AM LEDs can be integrated in on-chip bipolar RF integrated circuitry at micron and even submicron dimensions and have furthermore modulation frequencies into the GHz rang. As a first analyses, the optical propagation mechanisms were modelled by developing a custom designed EXCEL Progressive Ray Tracing Design Tool. (EPRTDT), whereby the positioning of the optical source, the initial launch direction of a particular optical wave fronts, and the subsequent refraction of planar ray fronts into subsequent layers of different refractive indices, in the structure could be progressively modelled. Subsequently, more exact simulations could be obtained by using an existing advanced simulation tool, RSOFT, as is generally available on the free market. The specific approach enabled the design of basic optical microstructures in a silicon 0.35 micron RF bipolar process, determining the dispersion behavior of propagation at different wavelengths, coupling of radiation into adjacently lying waveguides, determining propagation behavior into different type of waveguides, studying interaction with secondary regions of different refractive index, as well as design specific structures that could propagate radiation vertically out of the micro-structures into free space. The analyses have important applications for the realization of wavelength dispersers, couplers of SiAMLEDs into waveguides, realization of optical link structures on silicon chip, as well as micro vertical emitters of radiation out of the chip.

Although optical sensors incorporating grating inscribed and etched fibres are now sufficiently mature and well established in the market, however, designs based on more exotic nanowires and photonic crystal fibres are becoming increasingly important and showing much improved sensitivity by accessing a larger evanescent field. Similarly, novel planar design concepts, such as the silicon slot guide-based design is showing even greater promise, allowing the exploitation of well-developed CMOS fabrication technologies for potentially low-cost sensor elements. In compact Integrated Optic format, dielectric slots, plasmonic slots, Mach-Zehnder interferometer, and ring resonators are also emerging as novel photonic sensors. However, high index contrast also makes the modes in such sensing structures fully hybrid in nature and in such a case, full-vectorial rigorous numerical approaches will be necessary for their design optimization. Some selected results for silicon based compact photonic sensors will be presented illustrating the value and potential of the computationally efficient finite element method in such designs.

ZnO thin films were produced by the spin-coating sol-gel method on which the nanorods were grown by chemical bath deposition. The morphology of the thin films and nanorods were studied using field emission scanning electron microscopy (SEM), and the structure of the ZnO was determined by X-ray diffraction. It was found that the thin films comprised of randomly orientated particles (~57 nm in size) which covered the entire surface, although there were some voids visible in the films. The nanorods were found to have preferred orientation along the (002) direction, and this was confirmed by the SEM images which also indicated that the nanorods were of uniform size and height. Raman spectroscopy showed that both the thin films and the nanorods contained defects. The electrical properties of the thin films were studied before and after alpha particle irradiation.

In this study, we present the development of a doctor blade system for the deposition of thin semiconducting films by solution casting. The developed system allows a low-cost production of thin-film transistors (TFT) on large-area substrates. The deposition parameters like the velocity of the doctor blade and the temperature of the substrate affect the layer thickness and process quality directly and should be analyzed to improve the deposition quality. The developed system is operated by a microcontroller, which is responsible for adjusting the motor velocity and controlling the substrate temperature. The control system allows setting the velocity between 1 and 500 μm/s and the substrate temperature from 20 to 100°C. The implemented LCD display with control elements provides the user interface and allows setting up and controlling the process parameters. The high quality step motor drives the linear actuator with the attached substrate and realizes the relative movement of the doctor blade over the substrate. The micro-step control algorithm provides the high resolution and smooth movement of the substrate. The heating system is realized by a self-adhesive heating film and sensor element, mounted on the substrate. Additionally, an ultrasonic excitation of the doctor blade realized by an attached ultrasonic transducer can be used to improve the layer quality.

During electro-deposition of a TiO₂ film on titanium foil, an etching agent supplies ionic species that create the desired morphology by chemical dissolution of the oxide layer. The etchant ions attack both titanium ions and the oxide film to form hexafluorotitanate complexes, water and hydroxyl species. In this study, an attempt was made to reduce the duration of a TiO₂ film electro-deposition process by increasing the chemical dissolution rate. Two 127 μm-thick titanium foil substrates were anodised for different durations in an anhydrous polar organic solvent containing different amounts of an etchant. This yielded 9 μm-long nanotubes. Anodisation current density measurements for a two hour process showed slow chemical dissolution when the amount of etchant was low. In an attempt to speed-up the electro-deposition process, the amount of etchant was increased and anodisation carried out for only an hour. This yielded films (consisting of nanotube arrays) that are equal in thickness to that obtained in the two hour process. However, scanning electron microscopy revealed un-etched regions of the film between the tubes when the etchant concentration is high. These fragments are dimensional irregularities in an otherwise uniform tubular structure and hence are defect sites that could reduce charge transport efficiency. The study shows that the nanotube array quality is reduced when the duration of the anodisation process is shortened by an increased etch rate, without further optimisation of the anodisation parameters.

Structural, morphological and optical studies of rutile-phase TiO₂ rods, grown on F:SnO₂-coated glass substrates, using hydrothermal chemical bath deposition, are reported. The methods used to determine the optical properties of a semiconductor-on-substrate two-medium system have been successfully applied to the following three-medium structure: vertically well-aligned rods of TiO₂, an F:SnO₂ (FTO) conducting thin film and a glass substrate. Reflectance fringe measurements yielded the thickness of the TiO₂ layer to be d = 4.2 μm, which agreed well with the length of rods observed using SEM. The F:SnO₂ thickness of 569 nm measured from reflectance fringe spacings also agreed with SEM measurements. A room temperature absorption edge of E_g = 2.90 eV was obtained for the top layer of TiO₂ rods, which is similar to other values reported for TiO₂. A room temperature absorption edge of E_g = 3.56 eV was determined for the conducting F:SnO₂ layer.

We present development and first measurement with new ionizing radiation sensors with silica optical fibers. Our research is focused to merge silica optical fibers and some scintillation materials. The ionizing radiation has a minimal effect to silica optical fibers in comparison with plastic optical fibers which are usually used to these measurements. In combination with the right scintillation materials we created first set-up of sensor to measurement beta and gamma radiation. Our sensors are prepared for the most types of scintillation materials structures. The structure can be in liquid, powdered or crystalline state. The advantages of each type of structure are presented with focus to type of ionizing radiation measurement.

Astronomical, astrometric and geodetic observations by mm-Wave Very Long Baseline Interferometry (VLBI) are adversely affected by precipitable water vapour (PWV) in the troposphere. Current water vapour radiometers (WVRs), such as that deployed at the Large Millimeter Telescope (LMT) site, are difficult to install and maintain, and are prohibitively expensive for surveying promising new sites for telescopes or for wide-spread deployment for a priori calibration. We report here on initial progress towards a Planar Integrated Low-Cost H₂O Atmospheric Radiometric Detector (PILCHARD), which aims to reduce the cost of 22 GHz WVRs for site surveys, whilst eliminating the need for moving antennas. It is found that the required tip curve can be generated by a static antenna using multiple pencil beams from a multi-feed, non-traditional offset reflector, while the necessary system receiver temperature is easily achievable using planar integrated off-the-shelf components alone.

Satellite remote sensing of inland water bodies has great potential for ensuring water quality and for obtaining reliable data which can be used for decision making. This is a rapidly evolving technology that is now widely utilized throughout the globe for providing a broad as well as detailed perspective on earth-system status and change. Inland water processes, such as eutrophication, may have a major impact on human life and can lead to environmental disasters. This study investigates the optical effect of atmospheric aerosols on remote sensing of the water-leaving radiance (L_w) at Roodeplaat dam. An in-situ measurement field campaign was performed at Roodeplaat dam (Pretoria) during the 2016 winter season, in relation to calibration and validation of Sentinel 2 and Sentinel 3 satellite data. In-situ measurements were performed simultaneously with the satellite overpasses at the dam. In-situ measurements included Aerosol Optical Thickness (AOT), water vapor column and downwelling spectral irradiance as well as the remote sensing spectral reflectance of the dam, R_rs. A radiative transfer code (Modtran) was used to predict the radiance at the Top of Atmosphere (TOA), compared to actual measurements from Sentinel 2 and 3. Sensitivity analysis demonstrated that retrieval of water-leaving radiance at small water bodies such as Roodeplaat dam was sensitive to aerosol optical properties as well as total column.

The intention in this work was to generate and store adequate energy to power a natural ambient room cooling system. A major problem that the automatic air-conditioning industry is facing today has to do with too much power consumption in that the heat and ventilation air conditioning (HVAC) systems are currently using about 50% of all produced electricity. The latter also does not consider the peak time of use, where the desired ambient temperature of an air-conditioned room is greatly affected by the activities of the occupants at a given time. As part of the power management system, the concept of charging a battery to full capacity is explored of exploiting the excess energy available surrounding a cooking pot after, even after the heat source is removed. Thermoelectricity (TE) is used to capture wasted heat from the pot, and the reclaimed thermal energy is optimized for conversion into the electrical power. This is in short what I did. These are my results in summary.

A low-cost heat exchanger system was developed that enable the realization of high pressure, low pressure isolated solar water heating systems in Africa. Africa countries are mostly located mid equatorial and has superfluous resources of solar and thermal energy. The design comprised of a copper coil based heat exchange system that can replace the normal heating element and thermostat in a conventional household geyser. The circulation in the system is performed by a small separate photovoltaic panel and circulation pump. The exchanger allows for isolation of the high pressure and low pressure sections of a normal household geyser system and enable the utilization of very large, low cost solar heat absorber platforms. This feature remarkably increasing the heat collection capacity of the system. An integrated switch allows the system to alternate between conventional electrical heating and solar water heating, according to prevailing weather conditions. A smart sensor system monitor absorber and ambient temperatures continuously, and controls switch on times and circulation rates according to prevailing weather conditions, and in order to optimize thermal energy collection. The system can be installed at approximately 10 000 -12 000 SA Rand. Calculations show that the system can provide hot water to a household in South Africa at approximately 0. 12 SA rand per kWh, implying a saving to current customer that uses grid electricity at approximately R600 per month (weather depending). The accumulated saving to the household owner is of the order of 200 000 SA Rand over a ten year lifetime period for the product. The system offers numerous new business opportunities and job creation opportunities in South Africa. It is believed that the technology can be supplied and products can be provided to other international countries outside of South Africa. In this case the international countries can draw advantage from the technology as developed in South Africa, and can import products at reduced (very low costs ) drawing on the advantageous of an extreme favorable exchange rates, reduced import levies, while providing dire job opportunities in an developing African countries.

Reduction in size and improvement of sensitive margins in modern semiconductor devices make them increasingly susceptible to stress and subsequent damage caused by the overvoltage. A fast responding and a higher energy absorbing overvoltage protection is desired. A hybrid solution is proposed. A moderate energy absorbing device is connected in parallel with a fast responding device to complement each other. Nonlinear current-voltage (IV) characteristics of these devices enable them to least interfere with the performance of the precision ac measurement system while reducing the effects of transient overvoltage. In this paper, the causes of transient overvoltage in ac-dc measurement system are analysed and a hybrid voltage limiting solution is proposed.

Structured laser beams have numerous applications, for example mode division multiplexing, optical tweezers and even astronomy. Spatial Light Modulators are typically used to display digital holograms, however they have a low refresh rate, only work with a single polarisation and operate on a limited range of wavelengths. Digital Micro-mirror Devices are able to spatially modify the amplitude of incident light as opposed the the phase and are increasing in popularity due to their high refresh rate, polarisation and wavelength invariance and they are able to work as digital holograms with the right encoding. We describe how these devices may be used in a laboratory environment for modal decomposition as well as some of their disadvantages. We describe a method to accurately measure the flatness of a DMD, which is one of the major issues with the devices.

Visible Light Communications (VLC) as well as Mode Division Multiplexing is a research area that is currently receiving significant interest which is beginning to migrate from proof-of-principle demonstrations towards optimized engineering. The ability to easily transmit and receive arbitrarily encoded and modulated optical signals is critical to prototyping in a lab environment. Software defined radios enable cost-effective development and testing of almost any coding scheme and modulation format with a significant bandwidth, if required. We present our experiences with using software defined radios and other platforms to drive LEDs and laser diodes and subsequently receive the transmitted signals.

We present the development of new methods and techniques of splicing and forming optical fibers with focusing on the development of new ionizing radiation sensors. Optical fiber-based ionizing sensors can be prepared by the combination of scintillation material and optical fibers. The type of optical fibers forming depends on the scintillation material structure. The type of scintillation material to ionizing radiation sensor preparation which can be used primary depends on the efficiency of ionizing radiation to scintillation radiation conversion. The standard types of optical fibers with different core diameters can be used for the powdered or crystalline structure of scintillation material. On the other side, the liquid scintillation material can be used in combination with microstructure fiber mainly. We prepared techniques for splicing and closing special hollow-core Photonic Crystal Fibers (PCF) and theirs cross splicing methods with standard optical fibers to using with this liquid scintillation materials. To powdered scintillation materials we prepared forming technology to optical fibers narrowing, etching etc. These techniques of fibers forming are presented.

For advanced technology nodes, device engineering efforts are focused on high mobility designs for performance enhancement, such as channel designs with Ge. Considering reliability, bias temperature instability (BTI) is among the major concerns. It is therefore mandatory to proper understand, characterize and model BTI in these technologies. It has been reported that SiGe pMOSFETs with a buried channel show improved BTI robustness. It was shown that the Si cap thickness plays a significant role on BTI behavior. The threshold voltage shift (ΔVth) of the FET was found to be made up by individual charge trapping events, and thinner Si caps significantly improve the reliability. This behavior is here discussed in the framework of charge trapping model, showing that it is consistent with the assumed parameters, such as the distribution of trap amplitude, and a trap energy distribution that is minimum at the band gap center and maximum close to the valence band. Besides analytical analysis, Monte Carlo simulations are performed, highlighting that the modeling framework is applicable to compact modeling of BTI in nanoscale SiGe MOSFETs.

This study focuses on the integration of copper oxide nanoparticles forming inorganic p-channel thin-film transistors (TFTs). The used CuO nanoparticles have a diameter of 25-55 nm and are dispersed in a water-based solution providing the opportunity of low-cost and large-scale integration processes. First investigations were realized using an inverted coplanar TFT architecture due to the low chemical and physical stresses the semiconductor has to withstand. Therefore, a gate electrode consisting of 50 nm aluminum followed by 7 nm titanium was integrated on a Si/SiO2 substrate. As gate dielectric a high-k organic-inorganic nanocomposite was deposited by spin-coating resulting in a layer thickness of 150- 180 nm. For the drain and source electrodes gold and nickel were examined. For both metallizations the influence of an electrode treatment with a self-assembling monolayer (2,3,4,5,6 Pentafluorothiophenol, PFBT) was investigated. The gate metallization as well as the drain/source electrodes were evaporated via e-beam and structured by photolithography followed by wet-etching processes and lift-off technique, respectively. In the last step, the CuO nanoparticle layer was applied by doctor blade process followed by evaporating the solvent in a convection oven under ambient conditions. The maximum temperature during the integration process was 115°C so that a compatibility to glass and foil substrates is given. The influence of the drain/source material on the electrical characteristics was explored as well as the impact of the electrode treatment. Besides single TFTs inorganic inverter circuits in complementary technique were analyzed.

The digitalization is one of the main driving force for technologic developments in the area of low-cost electronics. Sensors and RFID tags should be integrated possibly at low-cost to easily upgrade everyday objects with new functionalities. Key elements of such upgrading objects are often thin-film transistors (TFTs). In this article we analysed two different commercially available, high-k nanocomposites ino®flex Z3 and ino®flex T3 regarding their frequencydependent dielectric constant and surface properties. TFTs using either ino®flex Z3 or ino®flex T3 as gate dielectric were fabricated using common photolithographic integration methods and subsequently electrically analysed. For further device optimization a self-aligning integration technique was used utilising the nanocomposite ino®flex T3 as gate dielectric. For all integrated TFTs, dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT) was used as active semiconductor.

The Internet of Things (IoT) is a main driving force for research efforts in the area of low-cost electronics. Low-cost solutions for the upgrade of already existing everyday objects by sensors or RFID tags are needed. Key elements of such upgrading technologies are often thin-film transistors (TFTs). In this article we analysed the structurability of the commercially available, high-k dielectric ino® flex T3 by means of common used optical photolithographic techniques and wet-etching processes and its influence on the TFT performance. Furthermore, the impact of an alkanethiol treatment of the drain and source contacts on the charge carrier injection from the metal into the semiconducting layer was investigated. As active semiconductor a dithienothiophene (DTT) derivate was used.

Thin-film transistors (TFTs) are the pivotal elements driving electrical current in innovative systems. These applications emerge adding new functionalities to every-day products; therefore, new challenges are faced. Electric components in flexible displays, RFID tags, or electronics skin for health monitoring are subjected to a high degree of mechanical deformation. Nonetheless, the systems have to operate properly despite external influences. In this study, a brief review of the mechanical deformation on the electrical characteristics of nanoparticle-based TFTs is presented Conjointly, a case-of-study considering low-cost ZnO nanoparticle-based TFTs on PET substrate is analyzed. The TFTs were integrated on a freestanding substrate replicating a more realistic scenario for a later large-scale production. Fabrication steps with a maximum temperature of 120°C were employed availing the integration process to a wider range of substrates. As gate dielectric, a spin-on highk nanocomposite was selected in order to favor the mechanical stability of the layer as well as its permittivity. Moreover, the integration routine was adapted in order to reduce parasitic overlapping capacitances in the transistors. The TFTs were electrically characterized either in a flat state or under mechanical deformation, employing different bending directions as well as deformations parallel or perpendicular to the transistor channel.

Semiconductor metal oxide (SMO) sensors have been utilized as oxygen sensors in industry and research for decades. Oxygen molecules adsorb to the SMO surface which leads to a measurable increase of resistivity [1]. Those sensors are valued for their high accuracy, but they operate at high temperatures [2]. Therefore, heating circuits inside the sensors are required, increasing size and power consumption of the sensors. This paper investigates the applicability of zinc oxide nanoparticle (ZnO) structures as low-cost oxygen detectors for measurements at room temperature. The main advantage of ZnO nanoparticle-based electronics is their low production cost since the nanoparticles can be deposited by cheap process techniques like spray-coating, spin-coating, inkjet-printing or the doctor blade process. Furthermore, they provide a high surface area to volume ratio which leads to higher sensitivity to oxygen. The most critical disadvantage is the high inhomogeneity of particle size and shape which causes nanoporous ZnO layers with low conductivity and nonuniform electrical characteristics. Therefore, gate structures were integrated into the sensors, so that the ZnO nanoparticle conductivity can be adjusted by applying a gate voltage. ZnO nanoparticle transistors with different electrode geometries and channel length were manufactured and analyzed. In different oxygen concentrations ZnO layer resistance, dependent on the applied gate voltage, was measured. Based on the results, a new layout for low-cost sensors without heating structures was developed. Since this work is part of a project, in which a low-cost water quality sensor is developed, the sensors are designed for oxygen concentration measurements in liquids as well.

Ultraviolet solar-blind cameras are used for inspection and research within the High Voltage domain. The current research in the field is compared with each other, considering image processing and radiometry (energy). From this comparison and research experience, the aspects for the relation between optical and electrical energy are identified. These aspects include Ultraviolet camera selection, characterization, calibration, saturation and processing. Furthermore, the electrical aspects also highlighted are test configurations, partial discharge, atmospheric conditions and test standards. Practical examples are presented.

The paper presents a laboratory methodology for determining the space environmental effect on the focus of an objective lens for an earth imaging payload on a small satellite. Components used in space applications should undergo rigorous screening and testing, including thermal-vacuum (TVac) testing. These tests reduce risk and can provide critical information leading to risk mitigation strategies contributing to mission success. The global value and market for CubeSats for both commercial and scientific applications is fast growing and this has led to the demand for environmental test equipment. Existing facilities around the globe for satellite TVac testing are typically expensive and difficult to access and also oversized for nanosat applications. As a result, CSIR Optronic Sensor Systems embarked on developing a laboratory test procedure and a small scale TVac chamber based on commercial off-the-shelf (COTS) components. The specific purpose was to quantify the defocus of a COTS imaging lens under vacuum and over a specific operating temperature range. The TVac defocus is caused by variation of the refractive index of air with pressure and variation of the refractive index of glass with temperature. Temperature-related dimensional changes also contribute. The tests provided repeatable measurements leading to a TVac model for the defocus behaviour of the lens. The model allows for setting of a compensatory or “preemptive” defocus before launch.

The CSIR is currently involved in the research and development of an optical gas imaging camera to detect and locate hazardous industrial gasses specifically sulphur hexafluoride and volatile organic compounds. The ability to see very faint and small concentrations of gas is difficult due to the noise equivalent delta temperature of the detector. Extensive post image processing is required to improve the visibility of the gas. Various image processing techniques, including non-uniform correction, contrast, image subtraction and optical flow, will be investigated and compared to find the best method for optical gas detection.

With the launch of the ZACube-2 nanosatellite, a new technique of wildfire detection and monitoring from space will be evaluated. Potassium is an essential plant macronutrient and all vegetation biomass fires exhibit characteristic spectral “K-line” emissions in the near infrared (NIR), which can be isolated and observed with suitable optical filtering. However, as a new technique, the effectiveness of this kind of sensor from a space platform is unknown. The magnitude of the K-line emission signal seen from space is contingent on many factors, including the concentration of potassium in the biomass fuel, fire size and intensity as well as atmospheric state. The architecture and preparation of the flight model K-line sensor hardware is described, together with the approach to verification and validation of the sensor characteristics and performance on-orbit.

A tracking sensor system for precise telescope time realization called the Karoo Telescope Time (KTT), for next generation precision radio astronomy is described in this article. This is a key enabler for precision timing science like transients, pulsar search and pulsar timing. A Mark I real time sensor called KTT-GNSS was already implemented and verified and needs to ensure receptor timing below the <30ns level. Some aspects and design and algorithm testing for a Mark II post facto sensor called KTT-UTC which has the goal of <5ns is described herein. The Mark II sensor also has accurate daily intermediary sensors, based on past data, and is not based on any extrapolations like the Mark I sensor is.

Water being used for any purpose needs to adhere to a certain quality standard. Performing tests to ensure water quality can be done in an analytical laboratory with high precision using a wide range of techniques and equipment. There is a growing need, however, for low-cost point-of-need (PON) solutions that would be able to serve a larger portion of earth’s population. One of the techniques, Impedance Spectroscopy (IS), measures the impedance of a water sample across a wide range of frequencies in order to analyse some frequency dependent properties of a sample. The problem addressed in this project is to develop an inexpensive, PON, system that can perform Impedance Spectroscopy on water samples. The impedance spectroscopy system is being developed in CMOS using the 0.35um ams AG process and will produce an impedance spectrum with frequencies ranging from 1 Hz to 10 MHz. The system interfaces with water samples through a standard three-point electrode, with voltage signals being maintained between the reference and working electrode. The analog front end for measurement as well as the digital control circuitry is included in the CMOS design.