ABSTRACT
This chapter restricts the definition of Thin Film Transistors to those devices deposited on a thick SiO2 substrate such as glass or quartz. This technology, which allows the fabrication of millions of TFT's on a large, transparent glass or quartz substrate, has resulted in some entirely novel products. The most eye-catching are today's high-performance colour liquid crystal displays (LCD), which rival the quality of cathode ray tubes at only a fraction of their weight. The properties of the poly-Si TFT are determined by the density of states which exist in the forbidden gap due to the presence of grain boundaries and intragrain defects. When this material is annealed, the amorphous material will crystallise, and a poly-Si film is obtained by Solid Phase Crystallisation (SPC). An alternative to solid phase crystallisation is the use of a laser beam which heats an a-Si (or poly-Si) layer until the melting point.
