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N type silicon-rich nanocrystalline-SiN(x) ∶ H films were prepared by plasma enhanced chemical vapor deposition technique by changing NH3 flow rate. The effect of nitrogen incorporation on the microstructure and photoelectric properties of the thin films were characterized by Raman, Fourier transform infrared spectroscopy, ultraviolet-visible absorption spectra, and Hall effect measurement. The results indicated that with the increasing NH3, a phase transition from microcrystalline to amorphous silicon occured. Transmission electron microscope observation revealed that the size of silicon quantum dots could be adjusted by varying the flow rate of NH3. The microstructure order of the films reduced with increasing the flow rate of NH3, while the optical band gap increased, and the optical band tail became narrow. Meanwhile, Si—N bonds density increased and P doping was blocked. I-V testing results showed that with increasing NH3, the conductivity of films first decreased compared with nanocrystalline-Si and then increased. These behaviors reveal a competition in the mechanisms controlling the conductivity. However, with further increasing NH3, the conductivity decreased significantly due to rapid carrier recombination on the amorphous net structure.

Phosphorus (P) doped Si-quantum-dots/SiO 2 multilayer films have been deposited by plasma enhanced chemical vapor deposition (PECVD) technique, and Si quantum dots (Si-QDs) are obtained by the following annealing treatment. Raman and transmission electron microscopy (TEM) results show that P doping prevents the growth of Si-QDs. The photoluminescence (PL) intensity can be enhanced by proper P doping, and a maximal PL intensity is obtained when the doping flow ratio of phosphine and silicane is 0.75%. The resistivity of the films is reduced by P doping, and proper doping leads two orders of magnitude lower than that of the intrinsic films. Analysis shows that proper P doping in the multilayer films could fill the carrier capture center in interface and suppress the non-radiative recombination of carriers.

The authors prepared nc-SiOx: H thin films using plasma enhanced chemical vapor deposition methods (PECVD) and investigated the influence of oxygen incorporation on the microstructure and band gap properties of the films. The results indicated that with the increase in oxygen mixing ratio (CO2/SiH4), the grain size of the nanocrystal-silicon grain as well as the crystallinity of the film reduced, and the surface tensile stress of the nanocrystal-silicon grain first increased and then decreased. Fourier infrared absorption spectra analysis indicated that, with the increase in oxygen mixing ratio, the intensity of the oxygen rich Si--O bond increased while that of the silicon rich Si--O bond decreased and the structure factor reduced in the meantime accompanied by the improved order degree of thin films. The structure factor increased when the oxygen mixing ratio exceeded 0.08, which shows that the order degree of thin films dropped. In addition, the optical gap increased and the band tail width first increased and then decreased as a result of the incorporation of the oxygen. As a result, the microstructure and band gap properties of the films can be controlled by incorporating oxygen. And the crystallinity and optical gap of the material was high, and the microstructure of the films was improved at the same time when the oxygen mixing ratio was 0. 08, so it can be used as intrinsic layer of the thin-film solar cells.

Graduation Project is a significant step for undergraduate students to practice their knowledge learned in universities. Due to many reasons, e.g., there are no tools to support total quality control process for the entire graduation project management, the completion quality of graduation project is not as good as the authorities expected. To address this issue, we implemented a graduation project management information system based on B/S model by using ASP & SqlServer to monitor, manage and control those which participate in the graduation project processes. It is driven by total quality control method and is supported by workflow technology. This system has been deployed and used in our department for 6 years. By this system, the management of graduation project becomes easy and efficient and the completion quality of graduation project as well as the graduation paper is improved a lot in our department.

Relevance feedback is an iterative search technique to bridge the semantic gap between the high level user intention and low level data representation. This technique interactively determines a user's desired output or query concept by asking the user whether certain proposed 3D models are relevant or not. For a relevance feedback algorithm to be effective, it must grasp a user's query concept accurately and quickly. In this paper, we propose the use of biased support vector machine active learner for conducting relevance feedback for 3D model retrieval. The algorithm selects the most informative 3D models to query a user and quickly learns a boundary that separates the 3D models that satisfy the user's query concept from the rest of the dataset. Experimental results show that this algorithm achieves higher search accuracy than traditional query refinement schemes.

Amorphous silicon oxide containing nanocrystalline silicon grain (nc-SiOx:H) films are prepared by a plasma-enhanced chemical vapor deposition technique at different negative substrate bias voltages. The influence of the bias voltage applied to the substrate on the microstructure is investigated. The analysis of x-ray diffraction spectra evidences the in situ growth of nanocrystalline Si. The grain size can be well controlled by varying the substrate bias voltage, and the largest size is obtained at 60 V. Fourier transform infrared spectra studies on the microstructure evolutions of the nc-SiOx:H films suggest that the absorption peak intensities, which are related to the defect densities, can be well controlled. It can be attributed to the fact that the negative bias voltage provides a useful way to change the energies of the particles in the deposition process, which can provide sufficient driving force for the diffusion and movement for the species on the growing surface and effectively passivate the dangling bonds. Also the larger grain size and lower band gap, which will result in better photosensitivity, can also be obtained with a moderate substrate bias voltage of 60 V.