Phosphors are a class of materials which emit visible light when impacted by either electrons or photons. Phosphors are the critical material in all self-emissive displays. The major display technologies which depend on phosphors are cathode ray tubes, flat cathode ray tubes (especially, field emission displays), thin film electroluminescent displays, and gas discharge plasma displays. Each of these technologies started with phosphors prepared in powder form, sprayed or screen printed onto a faceplate suitable for viewing. Electroluminescent displays have largely converted to thin film phosphors. It can be expected that, for many applications, the other competing technologies will also come to rely on more robust, high definition, thin film phosphors. Presently, full color displays must utilize several deposition and etching procedures to prepare the red, green, and blue pixels. Ion implantation of color centers is now paving the way for producing full color displays in a single host phosphor. We shall discuss the present limitations that compromise full color self-emissive displays, and present state-of-the-art solutions based on thin films and ion implantation.
The success of crystalline GaN as an optical and electronic material has motivated an enormous effort to explore all aspects of the material. Little is known and reported about the amorphous phase of this semiconducting wide band gap material. In this paper, we report on the properties of amorphous GaN (a-GaN) grown on p-Si at 443K using electron cyclotron resonance (ECR) plasma-assisted metalorganic chemical vapor deposition (MOCVD). Silicon is a potential alternative to sapphire due to its high quality and readily available as a large diameter and low cost substrates. The film was analyzed by a variety of methods, including scanning electron microscopy (SEM), atomic force microscopy (AFM) and x-ray diffraction (XRD). The current-voltage characteristics of a-GaN/Si heterojunction were measured from room temperature to 363K. Rectification behavior and photovoltaic effect were observed for this anisotype heterojunction. The electrical characteristics of Ni Schottky barriers on a-GaN were also investigated.
Effect of high magnetic fields on the threshold of laserinduced gas breakdownExperimental measurements of the pressure and magnetic field dependence of the threshold energy of CO2-laser-induced gas breakdown have been made in hydrogen, helium, nitrogen, and argon gases. These measurements clearly exhibit the effects of diffusion, laser pulse length, and elastic and inelastic energy losses. A simplified phenomenological theory of laser-induced gas breakdown which takes these effects into account is outlined. The predictions of this theory are compared with experimental results. The theory correctly predicts all of the qualitative trends in the data, and in the case of helium a quantitative fit is obtained.
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