Microacoustic investigations of different structural forms of silicon

Abstract
Silicon in its different structural forms is the most widely element in all modern microtechnological fields and in near future nanotechnological applications. Despite the great deal of interest in electronic, magnetic, and optical properties of all these types, only very little work is reported on their elastic properties. In this context, we determine the acoustic parameters: longitudinal, transverse and Rayleigh velocities as well as their corresponding acoustic impedances. Then, using angular spectrum model, we calculate their reflectance function and the acoustic materials signatures of these types of semiconductors. It is found that all V(z) signatures show an oscillatory behavior due to constructive and destructive interferences between different propagating surface acoustic wave modes. The values of wave velocities are found to change according to atomic arrangements as well as to defect density in different Si types. Similar variations are also noticed for their impedances as well as their elastic moduli.