Nanopore covered microporous silicon conductometric gas sensors have been produced via electrochemical etching and standard microfabrication techniques. Reversible and sensitive gas sensors working at room temperature have been fabricated. Sensing of NH3, NOx and PH3 at or below the ppm level have been achieved. The porous silicon (PS) surface has been modified using selective coatings including electroless tin, gold, nickel and copper solutions to increase the response to NOx, NH3, and PH3 respectively. The diffusion of the analyte species has been investigated in the nanopore and micropore regimes by numerical analysis. Comparing the response time of the hybrid porous sensor surface with numerical diffusion calculations on the pores, it has been observed that Knudsen diffusion time scales dominate the sensor response. A transduction model is proposed based on nanopore limited gas diffusion and the experimental response and recovery data.

In this work, an individual Ge island on top of silicon dioxide layer has been charged by a conductive EFM tip and quantitatively characterized at room temperature. Electrons or holes were successfully injected and were trapped homogenously in the isolated nano-scale Ge island. In order to quantitatively study these trapped charges, a truncated capacitor model was used to approximate the real capacitance between the tip and island surface. The analytical expression of the quantity of trapped charges in isolated Ge island as a function of the EFM phase signal was deduced. Applying a tip bias for -7V during 30 seconds leads to an injection about 800 electrons inside an individual Ge island.

Savannah River Site Defense Waste Processing Facility (DWPF) Sludge Batch 4 (SB4) high level waste (HLW) simulant at 55 wt % waste loading was produced in the demountable cold crucible and cooled to room temperature in the cold crucible. Appreciable losses of Cs, S and Cl took place during the melting. A second glass sample was subjected to canister centerline cooling (CCC) regime in an alumina crucible in a resistive furnace. X-ray diffraction (XRD) study showed that the glass blocks were composed of vitreous and spinel structure phases. No separate U-bearing phases were found.

The second order nonlinear optical (NLO) properties of two different ionic selfassembled multilayer (ISAM) films combined with Ag nanoparticles have been investigated. The plasmon resonances in the Ag particles concentrate the incident light, markedly increasing in the NLO efficiencies of the films. We find that the efficiency enhancement is significantly larger in conventional ISAM films compared to films made using a hybrid covalent ISAM technique (HCISAM), even though the intrinsic bulk second order non-linear susceptibility (χ (2)) is much larger for HCISAM films. We attribute this to the interfaces in HCISAM films being much easier to disrupt by external perturbations such as the metal deposition by which the nanoparticles are fabricated. We conclude that because the plasmon decay length is very short, the plasmonic enhancement of NLO effects primarily occurs at and near the film-particle interface. To discern the importance of the interfaces, we surrounded thin ISAM and HCISAM films with NLOinactive buffer layers, which confirmed this hypothesis, particularly in the case of HCISAM films.

Hydrolytically polymerized poly(methyl-co-vinyl)siloxane is cross-linked by radically and dehydrolytically at elevated temperature. Peroxide-type thermal radical generator is found to cross-link the polymer at the vinyl and methyl pendant groups. In parallel, free silanol (Si-OH) end groups in the polymer also contribute to cross-linking by dehydrolytic polycondensation. By use of these two-fold cross-linking mechanisms, we were able to deposit highly cross-linked siloxane polymer film which provides excellent optical and electrical properties. Cured film of 500 nm thickness exhibited the pencil hardness of 9H on glass with > 95% visible light transmittance. These excellent features are applied to optical hard coating for flexible displays and touch panels. The cured film also exhibited excellent electric properties. The leakage current of the film is as low as that of CVD dielectric film, and the break down field is exceeded 3 MV/cm, which enabled the film to be applied to insulator in thin film transistor. We carried out analyses of the polymer in film and powder form with 13C- and 29Si-NMR MAS, FT-RAMAN and FTIR-ATR methods to investigate curing mechanism. The analysis results clearly indicated that the cured film contains unique Si-(CH)n-Si bonds generated by radical crosslinking, and all the Si-OH bonds are consumed by hydrolytic polycondensation as well. The Si-(CH)n-Si bonds are more rigid and less polar than Si-O-Si bond, which should be the major reasons that radical condensation remarkably reinforced the film. This radically and thermally cured poly(methyl-co-vinyl)siloxane film was applied to Mo-gate thin film transistor fabricated on glass as the gate insulator. The I-V characteristics from the transistor were equivalent to those made using CVD-SiN insulator.

This paper presents the implementation of indium gallium arsenide field-effect transistors (InGaAs FETs) as non-volatile memory using lattice-matched II-VI gate insulator and quantum dots of GeOx-cladded Ge as the floating gate. Studies have been done to show the ability of II-VI materials to act as a tunneling gate material for InGaAs based FETs, and GeOx-cladded Ge quantum dots having the ability to store charges in the floating gate of a memory device. Proposed structure of the InGaAs device is presented.

This work is about the production of hybrid coatings of the system SiO2-PMMA (PMMA, polymethylmethacrylate). These materials have interesting mechanical and chemical properties useful for anticorrosive and wear resistance applications. SiO2-PMMA hybrids were obtained by the sol-gel traditional process, using tetraethylorthosilicate (TEOS) and methylmethacrylate (MMA) by Aldrich Co, as starting reagents. The SiO2:PMMA ratio was varied from 0:1 to about 1:1 at air atmosphere deposition. The coatings were obtained on acrylic sheets and silicon wafers. A diversity of coatings with chemical composition ranging from SiO2 and PMMA to obtain the SiO2-PMMA hybrids were obtained. Infrared (IR) and atomic force microscopy (AFM), were performed to determinate structural and morphological behavior.

In this work, we study the replication of nanotextures used in thin film silicon solar cells to enhance light trapping onto inexpensive substrates such as glass or polyethylene naphtalate (PEN). Morphological analysis was carried out to asses the quality of these replicas. Moreover, single and tandem a-Si:H solar cells were deposited on top of the master and replica structures to verify their suitability to be used as substrates for solar cells in n-i-p configuration. We find stabilized efficiencies around 8% which are similar for tandem cells on masters and PEN replicas.

With the aim of inducing the β modification in isotactic propylene (iPP), three industrial processes were tested, and calcium carbonate with a particulate size of 0.7 microns was used as the nucleating agent. A surface modification was carried out as a part of the calcium carbonate with stearic acid and it was used; however, the other part was used without surface modification. They were made from master batches using TSE. Dilutions in cast film were made from master batches using single screw extruder (SSE). Finally, annealed films were made with a heating press. So, β phase content of the TSE sample, SSE sample, and the annealed sample were measured by X-Ray diffraction (XRD) and their thermal behavior was measured by Differential Scanning Calorimetry (DSC). The β spherulites where also observed by Product Lifecycle Management (PLM).

Although conventional floating gate (FG) Flash memory has already gone into the sub-30 nm node, the technology challenges are formidable beyond 20nm. The fundamental challenges include FG interference, few-electron storage caused statistical fluctuation, poor short-channel effect, WL-WL breakdown, poor reliability, and edge effect sensitivity. Although charge-trapping (CT) devices have been proposed very early and studied for many years, these devices have not prevailed over FG Flash in the > 30nm node. However, beyond 20nm the advantage of CT devices may become more significant. Especially, due to the simpler structure and no need for charge storage isolation, CT is much more desirable than FG in 3D stackable Flash memory. Optimistically, 3D CT Flash memory may allow the Moore's law to continue for at least another decade. In this paper, we review the operation principles of CT devices and several variations such as MANOS and BE-SONOS. We will then discuss 3D memory architectures including the bit-cost scalable approach. Technology challenges and the poly-silicon thin film transistor (TFT) issues will be addressed in detail.

Tritiated amorphous and crystalline silicon is prepared by exposing silicon samples to tritium gas (T2) at various pressures and temperatures. Total tritium content and tritium concentration depth profiles in the tritiated samples are obtained using thermal effusion and Secondary Ion Mass Spectroscopy (SIMS) measurements. The results indicate that tritium incorporation is a function of the material microstructure rather than the tritium exposure condition. The highest tritium concentration attained in the amorphous silicon is about 20 at.% on average with a penetration depth of about 50 nm. In contrast, the tritium occluded in the c-Si is about 4 at.% with a penetration depth of about 10 nm. The tritium concentration observed in a-Si:H and c-Si is higher than reported results from post-hydrogenation experiments. The beta irradiation appears to catalyze the tritiation process and enhance the tritium dissolution in silicon material.

Zinc oxide (ZnO) is an emerging optoelectronic material in large area electronic applications due to its various functional behaviors. We report on the fabrication and the characterization of ZnO nanorods. The ZnO nanorods were synthesized using sol-gel hydrothermal technique on oxidized silicon substrates. Different annealing temperatures were explored in the sol-gel hydrothermal synthesis of the ZnO nanorods. In order to investigate the structural properties, the ZnO nanorods were measured using X-ray diffractometer (XRD). The optical properties were measured using ultraviolet-visible (UV-Vis) spectroscopy. The influence of the annealing treatment on the structural and optical properties of the ZnO nanorods will be revealed and discussed in this paper.

The electrical resistance on the crystallization process of sputtered-deposited Ge1Cu2Te3 film was investigated by two-point probe method. It was found that the amorphous Ge1Cu2Te3 film crystallizes into a single Ge1Cu2Te3 phase with a chalcopyrite structure, which leads to a large resistance drop. The crystallization temperature of the Ge1Cu2Te3 amorphous film was about 250 °C, which is about 70 °C higher than the conventional Ge2Sb2Te5 amorphous film. The activation energy for the crystallization of the Ge1Cu2Te3 amorphous film was higher than that of the Ge2Sb2Te5 amorphous film. The Ge1Cu2Te3 compound with a low melting point can be expected to be suitable as the phase change material for PCRAM.

We report on a direct comparison of the effect of the atmospheric contaminants on a-Si:H and μc-Si:H p-i-n solar cells deposited by plasma-enhanced chemical vapor deposition (PECVD) at 13.56 MHz. Nitrogen and oxygen were inserted by two types of controllable contamination sources: (i) directly into the plasma through a leak at the deposition chamber wall or (ii) into the process gas supply line. Similar critical concentrations in the range of 4-6×1018 cm-3 for nitrogen and 1.2-5×1019 cm-3 for oxygen were observed for both a-Si:H and μc-Si:H cells for the chamber wall leak. Above these critical concentrations the solar cell efficiency decreases for a-Si:H solar cells due to losses in the fill factor under red light illumination (FFred). For μc-Si:H cells the losses in FFred and in short-circuit current density deteriorate the device performance. Only for a-Si:H the critical oxygen concentration is found to depend on the contamination source. Conductivity measurements suggest that at the critical oxygen concentration the Fermi level is located about 0.05 eV above midgap for both a-Si:H and μc-Si:H.

Silicon carbide is a semiconductor with desirable material properties, such as a wide bandgap and high thermal conductivity. It is an excellent material for constructing power switching devices operating in harsh environments where conventional semiconductors cannot adequately perform. One example of such a power device is a bipolar junction transistor (BJT). While the potential of the SiC BJT is recognized, appropriate techniques for producing devices is lacking due to its difficulty.

For example, in order to achieve a high voltage 4H-SiC BJT switch with nanosecond switching time, the device must have a low base resistance. The simulation results indicate that for an emitter width of 2.0 μm and a base width of 1.2 μm the distance between the two should be 0.4 μm or less to meet the requirement for base resistance. To produce the above-described geometries and spacing, it is desirable to construct the device in a self-aligned manner. Self-alignment in this context means that the relative spacing of features of the device, such as contacts, is automatically controlled by the processing sequence and process parameters, rather than by the careful alignment prior to exposure of a photo sensitive layer. For this purpose, we developed a novel self-aligned process for SiC BJT devices, that enables the fabrication of the design with high yield, as standard silicon self-aligned technique are not applicable.

The newly developed process starts with the deposition of the emitter contact metal, which provides the metal mask for the etching of the emitter ridges. Next, the wafer is planarized with photoresist and etched, so that only the emitter contacts are exposed. Electroless plating is then used to enlarge the contacts, and after removal of the resist, the plating provides an overhang, suitable for lift-off of the base contact metal. After the base contact metal deposition, the structure is planarized and etched, this time with a silicon dioxide layer, again exposing the plated emitter contacts and the lift-off step is the wet etching of the plated metal. The emitters are then all connected with a blanket wiring level, which also forms the base contact pad. This process is simpler and more robust than the process we developed to date. The main difference is the inclusion of a sacrificial lift-off overhang, created by electroless plating. It enables a well controlled overhang independent of steepness of the SiC ridge profile and the height of the emitter mesa. We successfully fabricated the overhang structure on 4H-SiC substrates.

In conclusion, we report the demonstration of a new self-aligned process, which provides a self-aligned emitter contact, a self-aligned base contact and eliminates the need for via holes smaller than the emitter stripe widths. We consider this new process a major improvement over existing processes to fabricate SiC BJT devices.

The optical properties of an InAsP/InP quantum well grown on a SrTiO3(001) substrate are analyzed. At 13K, the photoluminescence (PL) yield of the well is comparable to that of a reference well grown on an InP substrate. Increasing the temperature leads to the activation of non-radiative mechanisms for the sample grown on SrTiO3. The main non-radiative channel is related to the thermal excitation of the holes to the first heavy hole excited state, followed by the non-radiative recombination of the carriers on twins and/or domain boundaries, in the immediate vicinity of the well.

A series of arrays consisting of Permalloy stripes with dimensions of 100 nm × 300 nm × 1500 nm was fabricated using electron beam nanolithography and magnetron sputtering followed by the lift-off process. In order to elucidate the effect of magnetostatic interactions among nanosized stripes on magnetic properties of the arrays, the separation between the stripes in different arrays was varied in the range between 100 nm and 2000 nm.Magnetic hysteresis loopsof the arrays were measured using SQUID magnetometer for different orientations of the applied field with respect to the arrays. Magnetic anisotropy of the arrays was determined based on ferromagnetic resonance measurements at 9.8 GHz using EPR spectrometer. The measurements were carried out for different directions of in-plane magnetic bias filed. The angular dependence of the resonance field of the main resonant peak indicated presence of the uniaxial magnetic anisotropy due to elongated shape of the stripes. Comparison between angular curves of resonant fields for different arrays leads to the conclusion that increasing strength of magnetostatic interactions among the stripes leads to a suppression of the uniaxial anisotropy. The stripes separated by 2000 nm behave almost like non-interacting objects, but the effect of interactions becomes particularly significant for separations smaller than 600 nm. The properties of the arrays with the smallest separations resembled those of continuous films. Magnetostatic modes have been observed in the FMR spectra in addition to the main resonant peak. These modes are believed to result from dimensional confinement of lateral spinwaves in the magnetic stripes. No such modes were observed in the reference samples of solid Py films, with the in-plane applied magnetic field.

Dynamic local structural change of Pd nanoparticles on alumina surface during hydrogen absorption process was directly observed by x-ray absorption fine structure spectroscopy with dispersive mode. Main four parameters of x-ray absorption spectroscopy were determined even in the case of 50 Hz observation. It is clearly revealed that Pd nanoparticles directly change to the hydride phase in 50 ms at 200 kPa of hydrogen pressure. Although large lattice expansion was observed, significant structural distortion was not investigated in the results of the change of Debye-Waller factor.

An in-depth study of the structural and electrical properties of silicon (Si) films deposited by a novel low temperature technique at temperatures less than 400°C in a 13.56 MHz RF PECVD reactor is reported. The method is based on substrates having to undergo some initial preparatory steps (IPS) before the deposition of Si films in the PECVD chamber. The optical band gap of Si films deposited using this novel technique narrowed to 1.25 eV from 1.78 eV using the traditional a-Si:H deposition recipe. No annealing of any form was performed on the films to attain this band gap. Furthermore, photosensitivities for these films under various deposition conditions were of order 100 compared to 104 for a-Si:H films deposited under like conditions. Using metal-insulator-semiconductor devices, the Si films grown by this novel technique exhibit charge storage and memory behaviour unlike their amorphous counterparts. However, device endurance has been found to be inadequate, probably due to the presence of some contaminants - notably interstitial oxygen - which has been found elsewhere to have adverse effects on the electrical characteristics of Si films. If well harnessed, we suggest Si structures grown by this novel growth technique could be well-suited for flash memory applications, particularly 3-D flash which requires process temperatures to be less than 400 °C.

Cu2ZnSnS4 (CZTS) is an alternative material to Cu(In,Ga)Se2 (CIGSe) for use in thin film photovoltaic absorber layers composed solely of commodity elements [1,2]. Thus, if similar material quality and performance can be realized, its use would allow scale-up of terrestrial thin film photovoltaic production unhindered by material price or supply constraints. Here we report on our research on the deposition of CZTS by RF sputtering from a single CZTS target and co-sputtering from multiple binary sources on Mo-coated glass. We find some samples delaminate during post-sputtering furnace annealing in S vapor. Samples on borosilicate glass (BSG) delaminate much more frequently than those on soda-lime glass (SLG). We investigate the influences of the formation of frangible phases such as MoS2 at the CZTS/Mo interface and residual and thermal mismatch stress on delamination. We implicate fracture in a layer of MoS2 as the mechanism of delamination between the Mo and CZTS layers using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Wafer curvature measurements show significant (˜400 MPa) deposition stress for minimally optimized Mo deposition; however nearly stress-free Mo layers with good adhesion can be deposited using a multi-step Mo deposition recipe. Co-sputtering CZTS adds 100 MPa of stress on both BSG and SLG, however delamination is nearly absent for samples deposited on low-stress Mo layers. We investigate metallic diffusion barrier layers to prevent the formation of MoS2 at the interface. Lastly we discuss the importance of removing Mo oxide by sputter etching before CZTS deposition and its effects on adhesion and series resistance.