He De-Yan

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

Abnormal Crystallization of Silicon Thin Films Deposited by ICP-CVD

Silicon thin films are deposited by inductively coupled plasma chemical vapour deposition (ICP-CVD) at a low temperature of 350°C using a mixture of SiH4 and H2. The structures of the films are characterized by x-ray diffraction and Raman spectra. Under the optimum experimental conditions, we observe that the crystallinity of Si films becomes more excellent and the preferred orientation changes from (111) to (220) with the decreasing dilution of SiH4 in H2. Such an abnormal crystallization is tentatively interpreted in term of the high density, low electron temperature and spatial confinement of the plasma in the process of ICP-CVD.

Semi-quantitative study on the Staebler--Wronski effect of hydrogenated amorphous silicon films prepared with HW-ECR-CVD system

The method of numerical simulation is used to fit the relationship between the photoconductivity in films and the illumination time. The generation and process rule of kinds of different charged defect states during illumination are revealed. It is found surprisingly that the initial photoconductivity determines directly the total account of photoconductivity degradation of sample.

Influence of substrate temperature on the structure of sputtered a-Si1-xSnx:H alloys

X-ray diffraction, SEM and XPS were used to detect the structure of sputtered a-Si1-xSnx:H alloys. It is verified that the types of Sn site in the alloys depend on substrate temperature Ts. Most of the Sn atoms are substituted for Si at Ts<220°C, whereas a larger fraction of β-Sn clusters are formed at Ts 220°C.

Light induced microstructure transformation in a-Si:H films

A series of a-Si:H films are deposited by hot wire assisted microwave electron cyclotron resonant chemical vapour deposition (HW-MWECR-CVD), subsequently exposed under simulated illumination for three hours. This paper studies the microstructure change during illumination by Fourier Transformation Infrared (FTIR) spectra. There are two typical transformation tendencies of microstructure after illumination. It proposes a model of light induced structural change based on the experimental results. It is found that all samples follow the same mechanism during illumination, and intrinsic structure of samples affect the total H content.

Al-Induced Crystallization Growth of Si Films by Inductively Coupled Plasma Chemical Vapour Deposition

Polycrystalline Si (poly-Si) films are in situ grown on Al-coated glass substrates by inductively coupled plasma chemical vapour deposition at a temperature as low as 350°C. Compared to the traditional annealing crystallization of amorphous Si/Al-layer structures, no layer exchange is observed and the resultant poly-Si film is much thicker than Al layer. By analysing the depth profiles of the elemental composition, no remains of Al atoms are detected in Si layer within the limit (<0.01 at.%) of the used evaluations. It is indicated that the poly-Si material obtained by Al-induced crystallization growth has more potential applications than that prepared by annealing the amorphous Si/Al-layer structures.

Reduction of insertion loss after annealing of silicon oxynitride optical waveguides

The insertion losses of silicon oxynitride (SiON) waveguides have been measured in the 1550 nm wavelength region. The waveguide structure consisted of a 2.0µm SiON waveguide core with a refractive index of 1.50, a 0.5µm SiO2 upper cladding and a 5.0µm SiO2 lower cladding with a refractive index of 1.45. It was found that the wavelength-dependent insertion losses of the waveguide were greatly reduced by annealing and the loss was decreased more than 5.7 dB/cm at 1550 nm after annealing at optimum conditions. The former was attributed to the reduction of the absorption caused by N-H and Si-H vibration modes and the latter was due to the improvement of the interface roughness and homogeneity in the waveguides after annealing.

Eels investigation on Rs A-SixC1-x:h alloy film

EELS Technique is used to analyze the amorphous silicon-carbon-hydrogen alloy film deposited by RF sputtering method (RS a-SixC1-x:H). It is further verified that a structural change occurs at 1-x ≥ 0.40 in the alloy film.

Study On The Electrical And Optical Properties Of A-Si1-x Sn X:H Films Prepared By Sputtering

Hydrogenated amorphous silicon-tin alloy (a-Si1_xSnx:H) films were prepared by simultaneous rf sputtering of polycrystalline silicon and tin in a H2- Ar gas mixture. The optical gap E0 of the films depends on alloy composition x and preparation conditions. As tin content increases, the optical gap of the films becomes narrower linearly, but the dark conductivity increases exponentially. For films at lower substrate temperature and target power density, the optical gap becomes wider.