Zhang Fangqing

Study of influence of annealing on defects in diamond films with ESR and IR measurements

Abstract The defects in diamond films, synthesized by dc arc discharge plasma CVD and hot filament CVD, were studied using ESR and IR measurements, and the effects of annealing on defect states were investigated for the first time. The results showed that the films exhibited ESR signals produced by carbon dangling bonds of diamond and graphite. The g values of them were the same, g = 2.0027, the peak-to-peak line widths were 3.6 and 12.5 G respectively, and the spin density ( N s ) of the sample as-deposited was about 1.3 × 10 17 cm −3 . H atoms in the diamond films saturated the C dangling bonds, forming Cz.sbnd;H bonds. After annealing at different temperatures, Cz.sbnd;H bonds broke and H atoms escaped, and as a result, N s varied.

A study of phase transformation between diamond and graphite in P-T diagram of carbon

Abstract The phase transformation between diamond and graphite has been studied by calculating the transiting probability of the carbon atoms over a potential barrier. For the first time, the boundaries of the proposed metastable regions of diamond and graphite have been estimated theoretically, and the currently used characteristic paths of pressure-temperature for synthesizing diamond using a high pressure and high temperature (HPHT) method can be understood.

Infrared and Raman spectra of reactively sputtered amorphous GeNxH film

Abstract Infrared and Raman spectra of hydrogenated amorphous germanium nitride (a-GeN x H) are presented for the first time. A-GeN x H films were prepared by r.f. reactive sputtering of a poly-Ge target using a mixture of ArN 2 H 2 gases. The influence of the incorporated nitrogen atoms and r.f. power on the IR and Raman spectra of hydrogenated amorphous GeN x alloys is discussed further.

Study on the structural properties of a-Si1−xSnx: H films prepared by rf sputtering

Abstract The structure of hydrogenated amorphous silicon-tin alloy films has been systematically investigated as a function of substrate temperature Ts. X-ray diffraction, ir absorption and other characterization measurements were performed. It is shown that most of the Sn atoms go into substitutional Si sites at Ts

Adsorbate and light-induced effects on the conductivity in GD a-SixC1 - x: H

Abstract The effects of water adsorbate on dc dark conductance of GD a-Si x C 1 - x : H films are presented in this paper. The experiments have shown that adsorbed H 2 O acts as electron donor and increases the intrinsic or n-type sample conductance, while it decreases the conductance for p-type samples. It has been found that GD a-Si x C 1 - x : H films show weak Staebler-Wronski effects

Optical and electrical properties of a-SixC1−x:H films prepared by glow discharge from SiH4 and C2H4

Abstract Optimal technology conditions, infrared absorption (IR) spectra, variation of optical gap ( E opt ) with x , measurement results of ESCA and ESR of a-Si x C 1− x :H films prepared by glow-discharge decomposition of silane-ethane mixtures have been studied. Preliminary discussions about these experimental results have been made in this paper.

An investigation of the optical constants of GD a-SixC1−x:H films by the ellipsometric spectra

Abstract In this work, we mainly report the experimental results of the optical constants of GD a-Si x C 1−x :H(B) films, using the method of ellipsometric spectra. The relations between the refractive index n, imaginary part of the dielectric constants e 2 and the wavelength have been measured in visible light range (4000–7000A), respectively. It was found that a smooth peak appeared for both n and e 2 and the values of n and e 2 decrease with the increase of carbon content. A preliminary discussion is present.

Effects of annealing on the optical properties of hydrogenated amorphous carbon films

Abstract The effects of annealing on the optical properties of hydrogenated amorphous carbon films were determined. Infrared (IR) spectra, absorption coefficients, optical energy gap and band tail widths were obtained. The results show that increasing thermal annealing temperature, T a , reduces the hydrogen content, lowers the energy gap and increases the width of the absorption tail.

An investigation of the behavior of plasmon in GD a-SixC1−x:H films by XPS

Abstract XPS studies of the GD and RS a-Si x C 1−x :H films have been made. The chemical shifts of Si 2p and C is levels, valence-electron plasmon energy and the atomic density with alloy composition x are reported. Some differences etween GD and RS a-Si x C 1−x :H samples were observed and discussed preliminarily.

A study on surface morphologies of diamond films

Abstract The surface morphologies of polycrystalline diamond films deposited by the chemical vapor deposition (CVD) technique usually exhibit regular changes with increasing substrate temperature from ball-like amorphous carbon-hydrogen to polycrystalline diamond with predominant facets {100}, followed by {111} facet formation with finally, formation of microcrystalline graphite-rich deposits. We have calculated the temperature dependence of surface energies of the chemical vapor deposited diamond crystals during the preparation process using a model in which a fraction of carbon dangling bonds on the growth surface is saturated by hydrogen. The results can be used to interpret the regular changes of the surface morphologies of CVD diamond films.