Papers by Author: Yang Ping Li

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Authors: Yang Ping Li, Zheng Tang Liu
Abstract: Long-wave infrared windows and domes used under harsh conditions always suffer sand abrasion and raindrop erosion. GaP thin film has proved to be effective LWIR protective coating for zinc sulphide window. In this article, the GaP films have been deposited on 5-mm-thick thermo-pressed planar ZnS substrates by RF magnetron sputtering in high pure Ar gas, with a single crystalline GaP disc as the target. The maxima of the GaP/ZnS transmission spectra curve are less than the corresponding transmissivities of ZnS substrates, which indicates that the GaP films are of absorption. SEM results show that the films are very compact and their surfaces are glazed. XPS analysis shows that gallium content is more than phosphor content in the films, and oxygen is the main impurity. The more the gallium content is, the more absorption the film is of. The absorption does not vary greatly with oxygen content. So the absorption of the film is caused mainly by the overfull metal component, which increases the conductivity and causes the charge carrier absorption. Low absorption GaP film with the thickness more than 10 µm has been deposited, in which the Ga:P ratio is nearly 1:1.
Authors: Li Ping Feng, Zheng Tang Liu, Qi Jun Liu, Yang Ping Li
Abstract: The convex surface of the infrared dome is exposed to the harsh environment of the outside world, and therefore requires a coating which not only increases transmission but is able to withstand rain erosion so as to enhance system performance. This paper deals with the techniques that were developed to deposit a uniform thick SiO2 coating for sapphire dome by radio frequency magnetron sputtering. Results show that average transmission increment in wavelength range from 3 to 5um for the sapphire dome coated on convex surface was more than 4.0%. The transmission non-uniformity over the convex surface of the coated sapphire dome was less than 1.7%.
Authors: Yang Ping Li, Zheng Tang Liu, Feng Yan, Wen Ting Liu
Abstract: Germanium carbon films were prepared on ZnS substrates by reactive RF magnetron sput- tering of a Ge target in Ar and CH4 mixtures for IR antireflective and protective purposes. IR transmit- ttance spectra of the specimens were measured, with which H content in the films was investigated. The C and Ge contents and the atomic binding state were studied by X-ray photoelectron spectroscopy. The results show that H involved in the films combine mainly with C at low substrate temperatures. IR absorption peaks caused by the C-H bonds decrease with increasing temperature, indicating the drop of the C-H bonds content in the film. At relatively low temperature the film is high in C content and low in refractive index; at high temperature the film is low in C content and high in refractive index. Both C-Ge and C-C bonds exist in the film and O impurity combines mainly with Ge.
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