Amorphous silicon

About: Amorphous silicon is a research topic. Over the lifetime, 26777 publications have been published within this topic receiving 423234 citations.

Silicide precipitation and silicon crystallization in nickel implanted amorphous silicon thin films

Abstract: The nucleation and growth kinetics of NiSi2 precipitation in amorphous silicon thin films ion implanted with nickel was investigated using scanning transmission electron microscopy. It was found that the nucleation rate could be approximately described by a delta function at time t = 0 when the films were annealed between 325 and 400 °C. The growth kinetics of the precipitates at these temperatures were described by r ∝ tn, where r was the average radius and n was about 1/3. This behavior is consistent with models for growth of three-dimensional particles in a two-dimensional diffusion field. It was also found that the implanted amorphous films displayed an enhanced rate of single crystal silicon formation, apparently catalyzed by migrating silicide precipitates.

Structure of As‐Deposited LPCVD Silicon Films at Low Deposition Temperatures and Pressures

Abstract: In this work we studied the effect of the deposition temperature, total pressure, source gas dilution, and deposition rate on the structure of the as‐deposited silicon films. Depositions were performed by low pressure chemical vapor deposition (LPCVD) in the temperature range of 530 to 600°C and in the pressure range of 2 to 300 mTorr. For a fixed deposition temperature a phase transition from polycrystalline to amorphous silicon was shown to occur when the deposition rate exceeded a critical value. The critical value for the deposition rate was found to depend only upon the deposition temperature and to decrease as the temperature was decreased. By controlling the rate, as‐deposited polycrystalline silicon was obtained by conventional LPCVD at temperatues as low as 530°C. A relationship between the deposition rate and the partial pressure of the source gas was established via a kinetic model for the decomposition of silane and used to provide a simple model for the dependence of the structure of the as‐deposited silicon films upon the deposition parameters. This model was subsequently used to provide guidelines for both the expected structure of the as‐deposited films and the grain size of the as‐deposited polycrystalline silicon films over an extensive range of deposition conditions.

A novel preparation technique for preparing hydrogenated amorphous silicon with a more rigid and stable Si network

Abstract: A novel preparation technique, termed ‘‘chemical annealing,’’ was developed with the aim of making a stable and rigid Si network structure. The hydrogen content (CH) in the films and the optical gap could be reduced gradually without any change in substrate temperature by alternating deposition of a hydrogenated amorphous silicon layer several tens of A thick and treatment with atomic hydrogen. These films showed CH of 1.5–10 at. %, and exhibited high photoconductivities in the level of 10−5–10−4 S/cm. In the films with CH of 3 at. % or less, in particular, improvement was observed in stability against illumination with light. Their photoconductivity remained at about 65% of the initial value even after illumination with white light (AM1, 100 mW) for 60 h. In addition, time‐of‐flight experiments revealed a significant enhancement in hole drift mobility to a value of 0.2 cm2/V s at 300 K.

Real-time monitoring and process control in amorphous∕crystalline silicon heterojunction solar cells by spectroscopic ellipsometry and infrared spectroscopy

Abstract: In amorphous∕crystalline silicon heterojunction solar cells, we have performed real-time thickness control of hydrogenated amorphous silicon (a‐Si:H) layers with a precision better than ±1A by applying spectroscopic ellipsometry (SE). A heterojunction solar cell fabricated by this process shows a relatively high conversion efficiency of 14.5%. At the amorphous∕crystalline interface, however, infrared attenuated total reflection spectroscopy (ATR) revealed the formation of a porous a‐Si:H layer with a large SiH2-hydrogen content of 27 at. %. Based on SE and ATR results, we discuss the growth processes and structures of a‐Si:H in heterojunction solar cells.

Surface reaction and recombination of the SiH3 radical on hydrogenated amorphous silicon

Abstract: Mercury photosensitized decomposition of SiH4 is used to study surface reactions of SiH3 on hydrogenated amorphous silicon (a‐Si:H). The method involves modeling of gas phase production, reaction and diffusion to the walls of reactive species, in a parallel plate reactor, combined with measurements of surface reflection coefficient of SiH3, spatial density profile of SiH3, and a‐Si:H deposition rate. The reaction probability of SiH3 on a‐Si:H varies from 0.1 up to 0.2 in the 40–350 °C temperature domain. However, a large fraction (≥60%) of adsorbed SiH3 recombine on the surface, instead of being incorporated in the film.