We report a photoluminescence (PL) study of nanometer Si-based films deposited by Pulse Laser Deposition (PLD).The surface appearance and microstructure of the films were characterized by Atomic Force Microscope (AFM), X-Ray Diffraction (XRD) and Raman scattering spectroscopy (Raman).The effects of several experimental parameters such as gas pressure, atmosphere and anneal temperature on the luminescence properties of the films were studied. The mechanism of PL property of the Si-rich Si0<sub>2</sub> films was discussed, we suggest that the PL is derived from quantum confinement effect of Si nanometer grains and the non-bridge oxygen vacancy defects of silica.
Nanometer TiO<sub>2</sub> thin films are prepared by a sol-gel method and the effects of preparation technique on the microstructure and surface morphology of the obtained materials are studied using X-ray Diffraction [XRD,IR spectrum[IR], UV-VIS spectrum [UV-VIS,AFM and X-ray photoelectron spectroscopy[XPS]. The results show that the TiO<sub>2</sub> thin films are of anatase and rutile phase structures when annealed in a temperature range from 450°C to 600°C. When heated up to 700°C, the structure of TiO<sub>2</sub> film changed into rutile completely. In the TiO<sub>2</sub> thin films, there is some residual carbon from the starting organometallic components and a small amount of sodium ions diffused from the glass substrates. During heat-treatment, the absorption peak of water become weak gradually and the organic groups are disappeared completely at 500°C. Optimum film layers are obtained for the UV absorbance index. AFM result shows that the rough morphology of surface [RMS] of films is about 2-3nm or so.
In the paper, appearance and composition of an optical interference multi-layer coatings derived by sol-gel process were introduced. In particular, it is given that the distribution function of micro particles diameter size and the variety situation of porousness and graininess, as well as the influence of heat-treated temperature on optical quality of coatings. A lot of measurement result is supported by ESCA, AES, SEM and AFM and so on.
In this paper, Xe and He-Ne atomic lasers and CO<SUB>2</SUB> molecular lasers excited by 30 MHz approximately 2 GHz frequency have been studied, and then put forward the key of getting high efficiency is how to control the electron energy of discharge space. In the mobility-dominated discharge space of Xe laser, the product of gas pressure and input power is constant. In He-Ne laser, the product of gas pressure and power supply frequency is a constant in plasma discharge space of the glass tube under the optimum laser output. As to the slab waveguide CO<SUB>2</SUB> laser, the center of discharge space is quasi-Faraday dark region. But to the high power CO<SUB>2</SUB> laser (flow gas) the discharge space is plasma. Since there demand much lower electron energy, and high density for CO<SUB>2</SUB> laser, only in discharge structure there are several designing schemes can be referenced.
In this paper, we think that in rf discharge carbon-dioxide lasers there are only cathode space and quasi-Faraday dark region but not plasma area. The electron motive equation in the cathode space and quasi-Faraday region of the rf discharge space are given. We use the ponder motive force to calculate the electron energy in these spaces as well as the size of the quasi-Faraday dark region. At last, some problems of the high power carbon-dioxide laser are discussed.