STRUCTURE, DIELECTRIC, AND AC CONDUCTION PROPERTIES OF AMORPHOUS-GERMANIUM THIN-FILMS

Al-Ge-Al (MSM) capacitors are formed by vacuum evaporation under a vacuum of 2.66 x 10(-3) Pa. The thicknesses of the films (Ge) are measured by multiple beam interferometer technique (MBI). From X-ray diffraction studies, the structure of the germanium film (d = 247 nm) is found to be amorphous in nature. Aging, annealing, dielectric, and ac conduction studies are made for these films. The dielectric constant for a film of thickness 47.5 nm at 1 kHz and at room temperature is calculated to 16.5 and its value was found to increase gradually with the thickness of the films. AC conduction studies reveal that the conduction mechanism is due to hopping of electrons. The activation energies are calculated from the relaxation process and using the plot of log conductance versus the inverse absolute temperature. Cole-Cole diagrams are drawn and from these diagrams the spreading factor, beta, and relaxation time, tau(a), are determined.