PICOSECOND ENERGY TRANSPORT IN AMORPHOUS MATERIALS

摘要

High-power, short-pulse lasers in the picosecond and subpicosecond range are finding increasingly widespread use in materials processing and diagnostics. These lasers interact with a wide range of noncrystalline, or amorphous, materials including materials which are critical to the microelectronics industry such as silicon dioxide, silicon nitride, and amorphous silicon. Fractal theory is applied to examine energy transport in these materials in short time-scale applications, such as high-frequency, short-pulse laser-material interactions. It is shown that on this time-scale anomalous diffusion occurs, since carriers travel a distance on the order of the characteristic length of disorder in the material. In this case, by assuming normal diffusion in the anomalous diffusion region, the temperature increase can be under-predicted by a factor of nearly two.