Amorphous Silicon

Recent experiments on hydrogenated amorphous silicon using infrared absorption spectroscopy have indicated the presence of mono- and divacancy in samples for concentration of up to 14\% hydrogen. Motivated by this observation, we study the microstructure of hydrogen in two model networks of hydrogen-rich amorphous silicon with particular emphasis on the nature of the distribution (of hydrogen), the presence of defects, and the characteristic features of the nuclear magnetic resonance spectra at low and high concentration of hydrogen. Our study reveals the presence of vacancies, which are the built-in features of the model networks. The study also confirms the presence of various hydride configurations in the networks that include from silicon monohydrides and dihydrides to open chain-like structures, which have been observed in the infrared and nuclear magnetic resonance experiments. The broad and the narrow line widths of the nuclear magnetic resonance spectra are calculated from a knowledge of the distribution of spins (hydrogen) in the networks.

The oxidation behavior of polymer-derived amorphous SiAlCNs was studied in the temperature range of 900°–1200°C. The results revealed that while at 900°C the oxidation of the SiAlCNs follows typical parabolic kinetics, at higher temperatures the oxidation rates of the ...

Digital imaging systems for medical applications use amorphous silicon thin-film transistor (TFT) technology due to its ability to be manufactured over large areas. However, TFT technology is far inferior to crystalline silicon CMOS technology in terms of the speed, stability, noise susceptibility, and feature size. This work investigates the feasibility of integrating an imaging array fabricated in CMOS technology with an a-Se detector. The design of a CMOS passive pixel sensor (PPS) array is presented, in addition to how an 8×8 PPS array is integrated with the 75 micron thick stabilized amorphous selenium detector. A non-linear increase in the dark current of 200 pA, 500 pA and 2 nA is observed with 0.27, 0.67 and 1.33 V/micron electric field respectively, which shows a successful integration of selenium layer with the CMOS array. Results also show that the integrated Selenium-CMOS PPS array has good responsivity to optical light and X-rays, leaving the door open for further research on implementing CMOS imaging architectures going forward. Demonstrating that the PPS chips using CMOS technology can use a-Se as a detector is thus the first step in a promising path of research, which should yield substantial and exciting results for the field. Though area may still prove challenging, larger CMOS wafers can be manufactured and tiled to allow for a large enough size for certain diagnostic imaging applications and potentially even large area applications like digital mammography.

There is significant interest in harvesting ocean energy for powering the autonomous vehicles that can conduct surveillance for long durations. In this paper, we analyze the applicability of solar cells as a power source for medusa-inspired biomimetic vehicles. Since these vehicles will be operating under ocean waters and may need to dive at various depths, a systematic investigation was conducted to determine the variation of output power as a function of depth and salinity levels. We modeled solar energy harvested by flexible amorphous solar cell coated jellyfish vehicles by considering the variables bell diameter, turbidity, depth, and fineness ratio. Low fineness ratio shapes were found to be better for solar energy powered vehicles. Study of three representative species, Aurelia aurita (AA), Mastigias sp., and Cyanea capillata indicates that harvested power was proportional to bell diameter. Optimum power can be harvested by tilting the vehicle axis to face refracted sunrays. Depending on a swimming pattern, power harvested in charging mode and in propulsion mode could vary significantly. The model indicates that, under some circumstances, amorphous silicon solar cell may be a cost-effective way to power autonomous underwater vehicles (AUVs) operating in shallow-water conditions with large lateral travel distances.