Harumi Hikita

Model of the light-induced creation of two types of dangling bonds in a-Si:H

We present a new model of the light-induced creation of two types of dangling bonds in a-Si:H. The numerical calculation on the rate equation based on the model accounts for differences in the presence of two types of dangling bonds between high-quality samples and low-quality samples and also the observed kinetics of light-induced dangling bond densities in a-Si:H.

Light-Induced Annealing of Dangling Bonds in a-Si:H

We have investigated the kinetics of light-induced defect (dangling bond) creation and annealing processes in a-Si:H containing a large amount of hydrogen at 300 K and 77 K using the ESR technique. We have obtained direct evidence for the light-induced annealing of dangling bonds at 300 K. A model, in which nonradiative recombination of electrons and holes at hydrogen-related dangling bonds is taken into account, is presented to interpret the experimental results.

Deconvolution of ESR Spectra and Their Light-Induced Effect in a-Si:H.

It is shown that ESR spectra of dangling bonds in a-Si:H for glow discharge samples are deconvoluted into two components due to normal dangling bonds and H-related dangling bonds. The component for H-related dangling bonds has anisotropic g -values and anisotropic hyperfine coupling constants of 1 H. The distance between the dangling bond site and hydrogen site is estimated to be 2 A, using a tight binding theory. The normal dangling bonds constitute about 60% of the total spin density, while the H-related dangling bonds give about 40% for glow discharge samples. The glow discharge samples were also illuminated by a xenon lamp with 600 mW/cm 2 at room temperature. The normal dangling bonds and H-related dangling bonds are created almost equally by illumination.

Light-induced defect creation under pulsed subbandgap illumination in hydrogenated amorphous silicon

We have observed that pulsed subbandgap illumination creates dangling bonds with a density of about 10 18 cm m 3 in high-quality hydrogenated amorphous silicon films. Such a light-induced creation of dangling bonds can be accounted for in terms of a model in which self-trapping of holes in weak Si-Si bonds adjacent to a Si-H bond plays an important role. The kinetics of thermal annealing of the light-induced dangling bonds have been examined, in which half of the defects are annealed out at temperatures above 180C, but half of them remain.

Light-induced creation and annihilation of two types of dangling bonds in a-Si:H: their relative densities during illumination

We present a new model of light-induced creation of two types of dangling bonds, i.e. normal dangling bonds and hydrogen-related dangling bonds, in a-Si:H. We can account for the result that main dangling bonds are normal dangling bonds in high-quality samples, while both types of dangling bonds exist in low-quality samples containing a large amount of hydrogen.

Self-trapping of holes and related phenomena in a-Si:H

Abstract Self-trapping of holes at specific weak SiSi bonds in a-Si:H is considered on the basis of an extrinsic mechanism of self-trapping suggested by experimental evidence. The nature of the hole wave function is elucidated from a tight-binding approach on the basis of optically detected electron-nuclear double resonance experiments. Phenomena related to self-trapping of holes and excitons are discussed.

Light-induced defect creation under intense optical excitation in hydrogenated amorphous silicon

A model of light-induced creation of dangling bonds under intense illumination in hydrogenated amorphous silicon is presented. Numerical calculations on the density of light-induced dangling bonds are compared with the observed results obtained by Ogihara et al. under pulsed illumination for high-quality hydrogenated amorphous silicon. Good agreement between calculations and experiments is obtained for the density of light-induced dangling bonds and its dependence on illumination time.

The structure of dangling bonds having hydrogen at a nearby site in a-Si:H

We have deconvoluted the dangling bond ESR spectra into two components, one due to normal dangling bonds and the other to hydrogen-related dangling bonds in glow-discharge a-Si:H samples. The isotropic and anisotropic hyperfine interaction constants due to a hydrogen nucleus are estimated from the deconvolution. It is found that they are mutually related through a simple theoretical expression. The distance between the dangling bond site and hydrogen in the hydrogen-related dangling bond and relative densities of the above two types of dangling bonds are also estimated and discussed in correlation with the hydrogen content.

Electron Spin Resonance Study of Light-Induced Annealing of Dangling Bonds in Glow Discharge Hydrogenated Amorphous Silicon: Deconvolution of Electron Spin Resonance Spectra

We analyze the electron spin resonance (ESR) spectra of dangling bonds in a-Si:H samples before and after strong illumination which gives rise to the phenomenon of light-induced annealing of dangling bonds. The spectra are deconvoluted into two components, that due to normal dangling bonds and that due to H-related dangling bonds. Both before and after prolonged illumination, the normal dangling bonds constitute about 60% of the total spin density, while the H-related dangling bonds constitute about 40%. However, the photoannealed densities of the two types of dangling bonds are found to be different after strong illumination. In addition, we analyze the ESR spectra of dangling bonds observed after weak illumination.

Anisotropic magnetic centers and conduction electrons in hydrogenated microcrystalline silicon

Abstract Electron spin resonance of anisotropic magnetic centers (dangling bonds) and conduction electrons in hydrogenated microcrystalline silicon (μc-Si:H) prepared by plasma-enhanced chemical vapor deposition (PECVD) has been observed at room temperature. The anisotropic g -shifts of dangling bonds in μc-Si:H are discussed in terms of tight-binding approaches and in comparison with those of dangling bonds in μc-Si:H prepared by hot-wire CVD and hydrogenated amorphous silicon (a-Si:H), P b centers at the Si–SiO 2 interface and defects in crystalline silicon (c-Si). The spin densities of anisotropic magnetic centers and conduction electrons were measured as a function of gas-dilution ratio of SiH 4 into H 2 in mixture gas used in PECVD and are discussed.