Characterization of polymorphous silicon thin film and solar cells

Polymorphous silicon (pm-Si:H) films have been prepared by a new regime of plasma enhanced chemical vapour deposition in the region adjacent of phase transition from amorphous to microcrystalline state. Comparing to the conventional amorphous silicon (a-Si:H), the pm-Si:H has higher photoconductivity (sigma(ph)), better stability, and a broader light spectral response range in the longer wavelength range. It can be found from Raman spectra that there is a notable improvement in the medium range order. There are a blue shift for the stretching mode of IR spectra and a red shift for the wagging mode. The shifts are attributed to the variation of the microstructure. By using pm-Si:H film as intrinsic layer, a p-i-n junction solar cell was prepared with the initial efficiency of 8.51% and a stabilized efficiency of 8.01% (AM1.5, 100mw/cm(2)) at room temperature (T-R).

Microstructure of the silicon film prepared near the phase transition regime from amorphous to nanocrystalline

A kind of hydrogenated diphasic silicon films has been prepared by a new regime of plasma enhanced chemical vapor deposition (PECVD) near the phase transition regime from amorphous to nanocrystalline. The microstructural properties of the films have been investigated by the micro-Raman and Fourier transformed Infrared (FT-IR) spectra and atom force microscopy (AFM). The obtained Raman spectra show not only the existence of nanoscaled crystallites, but also a notable improvement in the medium-range order of the diphasic films. For the FT-IR spectra of this kind of films, it notes that there is a blueshift in the Si-H stretching mode and a redshift in the Si-H wagging mode in respect to that of typical amorphous silicon film. We discussed the reasons responsible for these phenomena by means of the phase transition, which lead to the formation of a diatomic hydrogen complex, H-2* and their congeries.

Wavelength tunable electroabsorption modulated DFB baser with thin film heater

　

Applications of dielectric thin film by electron cyclotron resonance plasma chemical vapor deposition for semiconductor photoelectronic devices

The paper reports a method of depositing SiO2, SiNx, a:Si, Si3N4 and SiOxNy dielectric thin films by electron cyclotron resonance plasma chemical vapor deposition (ECR CVD) on InP, InGaAs and other compound semiconductor optoelectronic devices,and give a technology of depositing dielectric thin films and optical coatings by ECR CVD on Laser's Bars. The experiment results show the dielectric thin films and optical coatings are stable at thermomechanical property,optical properties and the other properties. In addition, the dielectric thin film deposition that there is low leakage current is reported for using as diffusion and ion implatation masks in the paper. In the finally, the dielectric film refractive index can be accurately controlled by the N-2/O-2/Ar gas flow rate.

The diphasic nc-Si/a-Si : H thin film with improved medium-range order

A series of silicon film samples were prepared by plasma enhanced chemical vapor deposition (PECVD) near the threshold from amorphous to nanocrystalline state by adjusting the plasma parameters and properly increasing the reactions between the hydrogen plasma and the growing surface. The microstucture of the films was studied by micro-Raman and Fourier transform infrared (FTIR) spectroscopy. The influences of the hydrogen dilution ratio of silane (R-H = [H-2]/[SiH4]) and the substrate temperature (T-s) on the microstructural and photoelectronic properties of silicon films were investigated in detail. With the increase of RH from 10 to 100, a notable improvement in the medium-range order (MRO) of the films was observed, and then the phase transition from amorphous to nanocrystalline phase occurred, which lead to the formation of diatomic hydrogen complex, H-2* and their congeries. With the increase of T-s from 150 to 275 degreesC, both the short-range order and the medium range order of the silicon films are obviously improved. The photoconductivity spectra and the light induced changes of the films show that the diphasic nc-Si/a-Si:H films with fine medium-range order present a broader light spectral response range in the longer wavelength and a lower degradation upon illumination than conventional a-Si:H films. (C) 2004 Elsevier B.V. All rights reserved.

Study on optical band gap of boron-doped nc-Si : H film

The optical band gap (E-g) of the boron (B)-doped hydrogenated nano-crystalline silicon (nc-Si:H) films fabricated using plasma enhanced chemical vapor deposition (PECVD) was investigated in this work. The transmittance of the films were measured by spectrophotometric and the E-g was evaluated utilizing three different relations for comparison, namely: alphahnu=C(hnu-E-g)(3), alphahnu=B-0(hnu-E-g)(2), alphahnu=C-0(hnu-E-g)(2). Result showed that E-g decreases with the increasing of Boron doping ratio, hydrogen concentration, and substrate's temperature (T-s), respectively. E-g raises up with rf power density (P-d) from 0.45W.cm(-2) to 0.60w.cm(-2) and then drops to the end. These can be explained for E-g decreases with disorder in the films.

Improvement of thin silicon on sapphire (SOS) film materials and device performances by solid phase epitaxy

The increased emphasis on sub-micron CMOS/SOS devices has placed a demand for high quality thin silicon on sapphire (SOS) films with thickness of the order 100-200 nm. It is demonstrated that the crystalline quality of as-grown thin SOS films by the CVD method can be greatly improved by solid phase epitaxy (SPE) process: implantation of self-silicon ions and subsequent thermal annealing. Subsequent regrowth of this amorphous layer leads to a greater improvement in silicon layer crystallinity and channel carrier mobility, evidenced, respectively, by double crystal X-ray diffraction and electrical measurements. We concluded that the thin SPE SOS films are suitable for application to high-performance CMOS circuitry. (C) 2000 Elsevier Science S.A. All rights reserved.

Strain-induced morphological evolution and preferential interdiffusion in SiGe epitaxial film on Si(100) during high-temperature annealing

Strain relaxation in initially flat SiGe film on Si(1 0 0) during rapid thermal annealing is studied. The surface roughens after high-temperature annealing, which has been attributed to the intrinsic strain in the epilayers. It is interesting to find that high-temperature annealing also results in roughened interface, indicating the occurrence of preferential interdiffusion. It is suggested that the roughening at the surface makes the intrinsic strain in the epilayer as well as the substrate unequally distributed, causing preferential interdiffusion at the SiGe/Si interface during high-temperature annealing. (C) 1999 Elsevier Science B.V. All rights reserved.

Aluminum induced crystallization of strongly (111) oriented polycrystalline silicon thin film and nucleation analysis

A polycrystalline silicon thin film was fabricated on glass substrate by means of aluminum induced crystallization (AIC). Al and alpha-Si layers were deposited by magnetron sputtering respectively and annealed at 480A degrees C for 1 h to realize layer exchange. The polycrystalline silicon thin film was continuous and strongly (111) oriented. By analyzing the structure variation of the oxidation membrane and lattice mismatch between gamma-Al2O3 and Si, it was concluded that aluminum promoted the formation of (111) oriented silicon nucleus by controlling the orientation of gamma-Al2O3, which was formed at the early stage of annealing.

Fluorescence Hydrogen Peroxide Probe Based on a Microstructured Polymer Optical Fiber Modified with a Titanium Dioxide Film

A highly sensitive microstructured polymer optical fiber (MPOF) probe for hydrogen peroxide was made by forming a rhodamine 6G-doped titanium dioxide film on the side walls of array holes in an MPOF. It was found that hydrogen peroxide only has a response to the MPOF probe in a certain concentration of potassium iodide in sulfuric acid solution. The calibration graph of fluorescence intensity versus hydrogen peroxide concentration is linear in the range of 1.6 x 10(-7) mol/L to 9.6 x 10(-5) mol/L. The method, with high sensitivity and a wide linear range, has been applied to the determination of trace amounts of hydrogen peroxide in a few real samples, such as rain water and contact lens disinfectant, with satisfactory results.

Cellulose acetate polymer film modified microstructured polymer optical fiber towards a nitrite optical probe

A novel microstructured polymer optical fiber (MPOF) probe for nitrites (NO(2)(-)) detection was made by forming rhodamine 6G (Rh 6G)-doped cellulose acetate (CA) on the side wall of array holes in a MPOF It was found that the MPOF probe only have a response to nitrites in a certain concentration of sulfuric acid solution The calibration graph of fluorescence intensity versus nitrites concentration was linear in the range of 2.0 x 10(-4) g/ml-5.0 x 10(-3) g/ml. The method possesses case of chemical modification, low cost design, and potential for direct integration with existing instrumentation, and has been applied to the determination of nitrites in real samples with satisfactory results. (C) 2010 Elsevier B.V. All rights reserved