The field of phononic-engineered amorphous silicon is introduced. Specifically the construction of devices and waveguides for information conveyance and manipulation via phonons are considered. Typically the phononic properties of a given material are immutable and the phonons have such a limited diffusion length (nanometers) as to be unsuitable for engineering purposes. Crystalline silicon on the other hand has a reasonably large thermal conductivity and phonon diffusion length at sufficiently low temperatures. Phonon diffusion lengths can measure up to centimeters (e.g., crystalline SiO2) at temperature less than 10K but drop to sub microns at room temperature. Amorphous silicon, owing to the inherent scattering structures and owing to localization (of at least some phonon bands), has an anomalously large phonon lifetime [1]. This lifetime maybe indicative of a large phonon diffusion length and/or a fast phonon hop rate from one domain to the next and/or an indication that more than the typical three phonons (umklapp process) are involved in phonon scattering (e.g., see [1]&[2]). Techniques involving small-scaled devices and phonon bands to control umklapp phonon-phonon scattering are described. The potential to exploit inherent amorphous silicon structure as well as the engineering (post film deposition) of di-hydride distributions to induce phonon forbidden bands for significantly reduced multi-phonon scattering is explored. The indirect optical band gap of small domain (and possibly amorphous) silicon [3] provides the physical basis for the transduction of phonon and optical energies. Experimental methods for the post-deposition introduction of phonon scattering structure, the transduction of phononic information to optical information, and experimental approaches including the use of micro-Raman to probe phonon spectra and transport are described. The prospects of a fully integrated phononic, photonic, electronic amorphous silicon technology have been described.

We propose a pre-electrical bias aging to reduce threshold voltage (Vth) shift of hydrogenated- amorphous silicon thin-film transistor (a-Si:H TFT) for AMOLED display. The quantity of Vth shift in the sample subjected to a bias-aging is reduced due to the reduction of created dangling bond density, compared with a sample without a bias-aging. When an identical stress duration of 50,000 sec is applied to a-Si:H TFT with or without a pre-electrical bias-aging, the created dangling bond density (ΔNDB) after a pre-electrical bias-aging is decreased from 1.38 × 1011/cm2 to 0.685 × 1011/cm2. Our experimental results indicate that after the pre-electrical bias aging, a newly created dangling bond during an electrical stress is decreased because a weak bond density and hydrogen diffusion may be decreased.

To investigate the relationship between the thermal conductivity and the cooling rate, we have performed molecular-dynamics (MD) simulations based on a combination of the Langevin and Newton equations to deal with a heat transfer from l-Si to c-Si. The thermal conductivity of c-Si was measured by the direct method. In order to deal with finite-size effects, different cell sizes perpendicular to the direction of the heat current were used. The values of the thermal conductivity of 58 W/mK and 35.7 W/mK in the Tersoff potential were obtained at 1000 K and 1500 K, respectively. A MD cell with a length of 488.75 ¡Ê in the direction of a heat flow was used for estimating the natural cooling rate. The initial c/l interface systems were obtained by setting the temperatures of the MD cell at 1000 K and 1500 K, respectively, for Z <= 35 ¡Ê and 3800 K for Z > 35 ¡Ê. During the natural cooling processes, the temperature of the bottom 10 ¡Ê of the MD cell was controlled. The cooling rates of 7.4 × 1011 K/sec for 1000 K and 5.9 × 1011 K/sec for 1500 K were obtained, respectively.

Microcrystalline silicon was deposited by hot-wire chemical vapor deposition (HWCVD) using a graphite filament with and without a thin 50 nm microcrystalline silicon seed layer. Increasing silane concentration diluted in H2 led to a decrease in crystalline fraction as well in a decrease in dark conductivity and photo-conductivity. In addition, films deposited with a seed layer were found to have higher dark conductivity and photo-conductivity than those without a seed layer but deposited at slower growth rates. However, Raman spectroscopy showed that use of a seed layer resulted in only a small increase in crystalline fraction at the surface of the films which had thicknesses between 250-400nm. TEM measurements confirmed the crystalline nature of deposited films showing average grain sizes of 25 nm.