This PDF file contains the front matter associated with SPIE Proceedings Volume 7217, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

Semiconductor nanoparticles are attractive candidates for future large-area light emitting devices that are both costeffective and robust. We demonstrate a ZnO nanoparticle light emitting device realised without organic support layers. Tight layers with subμm thickness were fabricated using commercially available ZnO nanoparticles from the gas phase and fluorine-doped tin oxide glass as a substrate. After evaporation of a top electrode, a non-linear I-V characteristic was obtained. At room temperature, the device operates at voltages of only few Volts and shows electroluminescence in the visible spectral range and a pronounced UV peak related to near-band emission of the ZnO.

ZnO nanostructures were grown on Si (111) substrates using: Pulsed Laser Deposition. The impact of growth temperature (Ts) and Ar pressure (PAr) on the morphology, crystal structure and photoluminescence was investigated. Various types of ZnO nanostructures were obtained. Self-forming arrays of vertically-aligned nanorods and nanocones with strong c-axis crystallographic orientation and good optical response were obtained at higher Ts. The nanocone, or "moth-eye", type structures were selected for LED development because of their graded effective refractive index, which could facilitate improved light extraction at the LED/air interface. Such moth-eye arrays were grown on p-type Si (111) substrates to form heterojunction LEDs with the n-type ZnO nanocones acting as an active component of the device. These nanostructured LEDs gave rectifying I/V characteristics with a threshold voltage of about 6V and a blueish-white electroluminescence, which was clearly visible to the naked eye.

This paper discusses the effect of order and disorder on the electrical and optical performance of ionic oxide semiconductors based on zinc oxide. These materials are used as active thin films in electronic devices such as pn heterojunction solar cells and thin-film transistors. Considering the expected conduction mechanism in ordered and disordered semiconductors the role of the spherical symmetry of the s electron conduction bands will be analyzed and compared to covalent semiconductors. The obtained results show p-type c-Si/a-IZO/poly-ZGO solar cells exhibiting efficiencies above 14%, in device areas of about 2.34 cm². Amorphous oxide TFTs based on the Ga-Zn-Sn-O system demonstrate superior performance than the polycrystalline TFTs based on ZnO, translated by ION/IOFF ratio exceeding 107, turn-on voltage below 1-2 V and saturation mobility above 25 cm²/Vs. Apart from that, preliminary data on p-type oxide TFT based on the Zn-Cu-O system will also be presented.

The use of ZnO template layers grown Pulsed Laser Deposition (PLD) has been seen to produce dramatic improvements in the surface morphology, crystallographic quality and optical properties of ZnO layers grown on c-sapphire substrates by Metal Organic Chemical Vapor Deposition. This paper provides complementary details on the PLD-grown ZnO template properties.

Electrodeposition is a versatile method for the synthesis of ZnO thin films. Various nanostructures can be prepared in a controlled manner. The formation of ZnO nanowire arrays is observed in a deposition bath depleted in zinc salt precursor. Compared to dense ZnO films, the ZnO nanowire arrays present a high UV near band edge PL emission due to a better structural quality with lower structural defects. Recent works assign the formation of ZnO nanowires to the increase in the interfacial pH during the growth. At high pH, zinc ions are complexed by hydroxide ions and are negatively charged. This leads to the quenching of the lateral growth and the slowdown of the vertical growth rate. Mesoporous ZnO films can be prepared by electrodeposition by using a structure directing agent. Results obtained with eosin Y dye are interesting : after optimizing of the dye concentration, a maximum porosity of more than 62% and a maximum of specific surface area of 75 m².cm^-3 is obtained. These films are promising for photocatalysis and solar cell applications.

In this paper we report the use of a sheet of cellulose fiber-based paper as the dielectric layer used in oxide based semiconductor thin film field-effect transistors (FETs). In this new approach we are using the cellulose fiber-based paper in an "interstrate" structure since the device is build on both sides of the cellulose sheet. Such hybrid FETs present excellent operating characteristics such as high channel saturation mobility (>30 cm²/Vs), drain-source current on/off modulation ratio of approximately 10⁴, near-zero threshold voltage, enhancement n-type operation and sub-threshold gate voltage swing of 0.8 V/decade. The cellulose fiber-based paper FETs characteristics have been measured in air ambient conditions and present good stability. The obtained results outpace those of amorphous Si TFTs and rival with the same oxide based TFTs produced on either glass or crystalline silicon substrates. The compatibility of these devices with large-scale/large-area deposition techniques and low cost substrates as well as their very low operating bias delineates this as a promising approach to attain high-performance disposable electronics like paper displays, smart labels, smart packaging, RFID and point-of-care systems for self analysis in bio-applications, among others.

Homoepitaxial ZnO thin films doped with phosphorus (0.01% to 1% P) and/or alloyed with magnesium (1% to 4% Mg) show pseudomorphic growth with compressive or tensile strain in dependence on the dopant concentration. The structural quality of the used O-face ZnO(001) substrates was inspected by the rocking curves of the symmetric (002) and the skew-symmetric (101) peaks. Preselection of the substrate batches by the supplier decreased the twist dislocation density and increased the structural homogeneity within the batches considerably. TEM cross sections show increasing density of c-plane defects with increasing phosphorus concentration in the films. ZnO(002) rocking curves of MgZnO:P films on ZnO were as narrow as 27 arcsec with a FWHM of the substrate peak of 23 arcsec. The in-plane lattice match was confirmed for all dopant concentrations by HR-XRD triple axis scans of the (002) and (101) peaks. The results show the balance between tensile strain induced by Mg and compressive strain by P in ZnO. Two-dimensional growth with terrace-like surface structure is most prominent for the Mg-alloyed films without P. High electron mobilities up to 190 cm²/Vs at 300K and up to 800 cm²/Vs at 70 K were found in the homoepitaxial MgZnO:P thin films.

Hybrid green light-emitting diodes (LEDs) comprised of n-ZnO/(InGaN/GaN) multi-quantum-wells/p-GaN were grown on semi-insulating AlN/sapphire using pulsed laser deposition for the n-ZnO and metal organic chemical vapor deposition for the other layers. X-ray diffraction revealed that high crystallographic quality was preserved after the n- ZnO growth. LEDs showed a turn-on voltage of 2.5 V and a room temperature electroluminescence (EL) centered at 510 nm. A blueshift and narrowing of the EL peak with increasing current was attributed to bandgap renormalization. The results indicate that hybrid LED structures could hold the prospect for the development of green LEDs with superior performance.

ZnO epitaxial layers were plasma etched using BCl₃/SF₆ gas mixtures in an Oxford Instruments System 100 ICP 180. Etch rates were studied as a function of gas composition, pressure, ICP coil power and RF power. The ZnO etch rate in pure BCl₃ at a pressure of 10 mTorr, RF power of 350W, and ICP power of 1000W was ~1175 Å/min (-1000V bias). The etch rate increased with increasing SF₆ percentage in the flow, and for the same conditions in pure SF₆ the etch rate was ~1350 Å/min (-820V bias).

The flexible organic-inorganic thin film transistors (OITFTs) were fabricated with the structure of Al/ZnO/PVP/Al on PES [polyether sulfone] flexible substrate. PVP [poly-4-vinylphenol] organic gate insulator was coated on Al/PES film by the spin coating method. ZnO active channel layer was deposited on PVP/Si substrate by using atomic layer deposition (ALD) at various temperatures from 80 ~ 140 °C. The structural and electrical properties of ZnO films were analyzed by X-ray diffraction (XRD) and hall-effect measurement system. The carrier concentration and resistivity of ZnO film deposited at 100 °C were found to be about 10¹⁷ and 37.7Ω•cm, respectively. The field effect mobility (μ) and threshold voltage (V_TH) of the prepared OITFT were about 0.01 cm²/V•s and 12 V, respectively. The I _on/off switching ratio was about 10⁴.

Zinc oxide is a promising transparent conductive oxide (TCO) and there is unceasing interest in its optical and electrical properties for the last decades. In this paper, ZnO thin films modified by various additives such as erbium, vanadium and aluminum were fabricated using a sol-gel process and their electrical resistivity and surface morphology were investigated in terms of annealing conditions. Stable ZnO solutions containing different additives were synthesized by using 2-methoxyethanol as a solvent and monoethanolamine as a stabilizer. The electrical resistivity of ZnO films was found to be controlled by both doping concentration and annealing condition. Relatively lower electrical resistivity was achieved for the ZnO films doped with ~ 0.3 mol% Er, 0.3mol% Al or 0.03~0.1 mol % V after a post-annealing at 550 oC for 1 h in N₂/H₂. All the films deposited on glass exhibited very high transmittance of 90~97% within the visible wavelength region. This work was mainly focused on the overall pictures about the relationship between the electrical and optical performances and the processing variables such as doping species and concentrations.

We have studied the effects of thermal annealing in air on photoluminescence of bulk ZnO crystals grown by hydrothermal technique and nominally undoped ZnO layers grown by molecular beam epitaxy on sapphire. Annealing of the samples in air at temperatures above 600°C resulted in a dramatic enhancement of the Cu-related green luminescence (GL) band peaking at 2.45 eV and having characteristic fine structure. The GL band quenched at temperatures above 300 K due to escape of holes from the excited state of the Cu_Zn acceptor to the valence band. SIMS profiles revealed moderate increase of Al concentration and significant increase of Cu concentration in annealed samples. Exciton bound to hydrogen-related donor (the 3.363 eV line) quenched after annealing the sample at temperatures above 750ºC.