ESTIMATION OF THE PHYSICAL CONSTANTS OF A POLYDIMETHYLSILANE CRYSTAL AND ITS EVAPORATED FILM

The lattice parameters and density of the polydimethylsilane crystal, and the stiffness constants of the film prepared by the evaporation of the source polydimethylsilane powder, have been estimated using the x-ray diffraction technique and the surface acoustic wave, respectively. In the former case, the experimental x-ray diffraction patterns are compared with the theoretical pattern.s. As a result, it is found that the crystallographic structure of the polydimethylsilane crystal is monoclinic, with the lattice parameters a = 0.745 +/- 0.001 nm, b = 0.724 +/- 0.001 nm, c = 0.389 +/- 0.001 nm and gamma = 67.1 +/- 0.1-degrees. In the latter case, the stiffness constants are estimated froin the velocity of the surface acoustic wave propagating along the evaporated film/piezoelectric substrate structure. The values obtained on the assumption that the film is isotropic are c11 = (5.9 +/- 0.9) x 10(10)) N m-2, c12 = (3.5 +/- 0.9) x 10(10) N m-2 and c44 = (1.2 +/- 0.3) x 10(10) N m-2.