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Research Of Doped Nanocrystalline Silicion Film Based On Liquid Crystal Light Valuve Photosensitive Layer

Posted on:2017-04-26Degree:MasterType:Thesis
Country:ChinaCandidate:X Y LianFull Text:PDF
GTID:2308330485988269Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
Doped nanocrystalline amorphous silicon thin film is superior to the conventional amorphous silicon and microcrystalline silicon in electrical, optical and stability. Especially as a photosensitive layer of liquid crystal light valve, it not only has high absorption coefficient and photosensitivity, also has broadband gap and light stability. It is an ideal material to photosensitive detection.In this dissertation, Boron doped(B-doped) nc-Si:H thin films was prepared by RF magnetron sputtering. The effeets of boron content, substrate temperature and the hydrogen flow rate, on the microstructure and photoelectronic properties of nc-Si:H films, have been investigated by means of many modern characterization methods. Furthemore, a-Si1-x (CdTe) x:H thin films were put forward for the first time. The microstructures and photoelectronic properties were researched deeply.High resolution transmission electron microscopy(HRTEM) and Raman spectroscopy results show that when C(B)=0.16%, crystallization rate is 31.7%, grain size is 2.13 nm and grain growth along (111) direction. However, crystallization rate and grain size decrease with the increase of the B-doped. FTIR results indicate that B-doped of the film has close relationship with hydrogen flow rate. UV-vis transmission spectra find that transmittance is decreased, visible light absorption is enhanced and optical band gap (Eopt) is increased with the increased amount of boron doped. Because local density of states near Fermi level of B-doped films is low, the doping effect is obvious, so the conductivity can be controlled easily and can reach 10-4cm-1Ω-1, while the photosensitivity gradually reduced with the increase of B-doped. The study also found that the higher the temperature of the substrate, the less of defect density in the film, while hydrogen level in the membrane descended significantly with the increase of the temperature. With the increase of H2 flow, the density of hanging key in membranes decreased, but hydrogen level in the membrane do not increase significantly with the rising of H2 flow.The images of HRTEM,X-Ray Diffraction(XRD),and raman spectroscopy of Si1-X (CdTe) x:H films indicate that the samples surrounded by CdTe nanoparticles in amorphous silicon thin films, the CdTe grain size is about 5 nm, and the growth direction is along (111). the X-ray photoelectron spectroscopy(XPS) and Energy Dispersive X-ray Detector(EDX) results demonstrate that the elements of Te and Cd in the thin films don’t grow at a ratio of 1:1, the contents of Te is obviously higher than the Cd counterpart. With the augment of contents of CdTe, the film’s refractive index and absorption coefficient ascended evidently, while Eopt reduced from 2.01 eV to 1.75 eV. The dark conductivity of a-Si1-x (CdTe) x:H films which rising with the increase of CdTe doped, exceeds to three or for orders of magnitude compared to general a-Si:H films, while the light sensitivity lowers. The microstructure of thin film has been greatly changed after annealing process, The films change from as-prepared to the crystalline states, the crystalline grain size ranges from 50 nm to 100 nm and the shape is irregular, on top of that, CdTe in thin film is along different lattice planes, including (100), (220) and (111).
Keywords/Search Tags:liquid crystal light valve, nanocrystalline amorphous silicon, boron doped, cadmium telluride
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