The integration of graphene and 2D materials into device technologies requires a detailed understanding of how intrinsic and extrinsic forces impact their properties, as well as the development of engineering strategies to vary their properties for a specific response. In this paper we describe and review our efforts for hybridizing graphene in different ways so as to modify or enhance a range of properties. This hybridization comes in the form of chemical or electronic modification for use in applications ranging from chem/bio sensors to nanoelectronics. We discuss results on exploiting chemistry and defects in graphene for chemical vapor sensing, on hybridizing graphene with fluorine atoms for potential use in nanoelectronics, and on electronically hybridizing graphene in multilayer stacks that give rise to new optical and surface properties.
KEYWORDS: Metamaterials, Composites, Nanolithography, Lithography, Electron beam lithography, Video, Current controlled current source, Visible radiation, Fabrication, Laser systems engineering
Metamaterials designed for the visible or near IR wavelengths require patterning on the nanometer scale. To achieve this, e-beam lithography is used, but it is extremely difficult and can only produce 2D structures. A new alternative technique to produce 2D and 3D structures involves laser fabrication using the Nanoscribe 3D laser lithography system. This is a direct laser writing technique which can form arbitrary 3D nanostructures on the nanometer scale and is based on multi-photon polymerization. We are creating 2D and 3D metamaterials via this technique, and subsequently conformally coating them using Atomic Layer Deposition of oxides and Ag. We will discuss the optical properties of these novel composite structures and their potential for dual resonant metamaterials.
Novel ternary nanostructures (ZnO-Ga2O3 nanobrushes, SnO2-Ga2O3 heterostructures and Sn-doped Ga2O3 nanowires)
are excellent materials for gas sensing applications due to their large surface areas and structural defects. Also, these
nanostructures consist of different materials with different degrees of crystallinity and defect densities thus broadening
their gas sensing capabilities. Gas sensing devices, developed in our laboratory based on room temperature capacitance
measurements, were first fabricated by standard photolithography and lift-off techniques to pattern platinum (Pt) pads
and interdigitated fingers acting as conducting paths. The nanostructures, which were characterized by electron
backscatter diffraction (EBSD), transmission electron microscopy (TEM), and photoluminescence (PL), were then
incorporated by the catalyst-assisted growth directly onto the devices. The most efficient devices were those with high
yield of nanostructures and with low-resistivity of the Pt pads. To achieve that, different catalysts (nickel, Ni; copper,
Cu, and gold, Au) were used for different nanostructures. For example, the best catalyst for the device fabrication of Sn-doped
Ga2O3 nanowires was Ni whereas for nanostructures with high Sn content Cu was the best catalyst. Challenges
and successes of device fabrication for capacitance-based gas sensing devices are discussed in this work together with
some sensing results for such analytes as acetone, acetic acid, isopropanol, dichoropentane, nitrotolouene and
nitromethane.
Gene Array technology has allowed for the study of gene binding by creating thousands of potential binding sites on a single device. A limitation of the current technology is that the effects of the gene and the gene-derived proteins cannot be studied in situ the same way, thousand site cell arrays are not readily available. We propose a new device structure to study the effects of gene modification on cells. This new array technology uses electroporation to target specific areas within a cell culture for transfection of genes. Electroporation arrays will allow high throughput analysis of gene effects on a given cell's response to a stress or a genes ability to restore normal cell function in disease modeling cells. Fluorescent imaging of dye labeled indicator molecules or cell viability will provide results indicating the most effective genes. The electroporation array consists of a microelectronic circuit, ancillary electronics, protecting electrode surface for cell culturing and a perfusion system for gene or drug delivery. The advantages of the current device are that there are 3200 sites for electroporation, all or any subsets of the electrodes can be activated. The cells are held in place by the electrode material. This technology could also be applied to high throughput screening of cell impermeant drugs.
Biological macromolecules (such as proteins, DNA, and RNA) are the machinery of biological processes. Sensors enabling quantitative, real-time detection of these objects promise an enhanced understanding and management of disease and illness, with obvious application to medicine and public health. Ideally, these such biosensors would be useable in the field, at medical point of care, or even in vivo, all of which places where sample preparation would be minimal and use of labeling reagents (e.g., fluorescently labeled antibodies) not practical. In a collaboration between the Electronics Science and Technology Division and the Center for Bio/Molecular Science and Engineering we have developed a microelectronic biosensor capable of label-free detection of a variety of biological macromolecules. When fully realized and implemented as elements in an array format, this biosensor may enable low cost, simultaneous, real-time detection of thousands of target macromolecules from small sample volumes (10's of ?liters) or even in vivo. We describe here the construction and performance of an example sensor based on conventional siliconbased technology, as well as future applications.
Dean Scribner, Mark Humayun, Brian Justus, Charles Merritt, Richard Klein, J. Grant Howard, Martin Peckerar, F. Keith Perkins, Lee Johnson, W Bassett, P Skeath, J Weiland, Eugene de Juan, James Finch, Roger Graham, Walter Trautfield, Scott Taylor
An important new area of biomedical engineering is the development of neural prosthesis particularly in the area of cochlear and retinal devices. An intraocular retinal prosthesis test device is currently under development at NRL/JHU. The microelectronic device has an image format of 80 x 40 unit cells interfaced to the retinal surface via an array of microwires in a glass matrix. The system architecture and technology development issues are discussed as well as the topic of biocompatibility. This test device will enable acute human experiments in an operating room environment to demonstrate a massively parallel interface between retinal tissue and a microelectronic array.
Pattern placement errors are a problem in the manufacture of masks for proximity X-ray lithography. Many of these errors are attributable to long term drifts in beam position relative to external fiducials. To address this we have developed a technique based on through-the-membrane monitoring of the electron beam position. This uses a solid state detector with high bandwidth and gain mounted near the back surface of the target membrane. An accurately patterned overlayer on the detector provides the fiducial reference. The overlayer is designed to modulate the electron-hole pair current generated in the diode by absorbing the incident beam. Position information is obtained by analyzing the image created from recording the diode current during patterning. The phase in a Fourier transform of the data at the spatial frequency of the patterned absorber gives a measure of the position of the incident beam. Changes in the observed phase from one frame to the next can then be used to correct position errors of the beam in real time. We report results from tests of various components of this system. Early indications are that the system will be sufficiently fast and accurate for proximity X-ray mask pattern placement correction.
We have developed a technique based on use of a novel e-beam detector to enhance pattern placement accuracy of high-performance e-beam tools in the patterning of membrane masks. The detector consists of a reverse biased Schottky diode whose area coincides with that of the membrane, and which is placed immediately behind the membrane/-absorber/resist multilayer. An accurately patterned absorber overlayer covers the detector surface. The overlayer absorbs a fraction of the incident electrons, modulating the detector signal as the beam passes over the membrane. We have studied and modeled the performance of prototype detectors covered with 16 micrometers period gratings over an incident energy range of 5-50 keV. The combination of Schottky diode and patterned overlayer has been used to improve electron scattering models. We have observed excellent SNR with a 40 nC/cm2 dose at 50 kV, and spatial resolution better than 0.1 micrometers of a beam transmitted through a membrane. More accurate position information can be obtained by taking a Fourier transform of the diode current waveform created as the incident beam traverses several grating periods. In a poor operating environment, we have observed phase accuracy in 100 micrometers fields of +/- 4 degrees. We have developed an algorithm capable of processing pattern-based data sets at high speeds and low information storage requirements. This technique can be easily implemented with little overhead and little modification of existing systems.
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