ELECTRICAL-RESISTIVITY OF EPITAXIAL MOLYBDENUM FILMS GROWN BY LASER-ABLATION DEPOSITION

The results of electrical resistivity measurements at room and low tem peratures, and also of reflection high energy electron diffraction ana lysis of thin (less than 110 nm) Mo films, grown by laser ablation dep osition are presented. The films deposited under ultrahigh vacuum cond itions on sapphire ((1) over bar 012) substrates at temperatures of 20 -750 degrees C are monocrystalline, with a [001] axis perpendicular to the substrate. It is shown that the ratio of room temperature to resi dual resistance which characterizes structural perfection, is in the r ange 12-32 for the films 70 nm thickness. It increases abruptly at fil m growth temperatures of 200-370 degrees C and changes weakly at furth er temperature increase. The analysis of data on the size (thickness) effect of the Mo films deposited at 750 degrees C revealed that the ef fective electron mean free path is in the range 0.1-1 mu m for the fil ms 15-110 nm thickness. Surface scattering was found to be the basic c hannel of electron scattering at helium temperatures, with the specula r coefficient q similar to 0.3 and residual bulk electron mean free pa th similar to 100 mu m. At low temperatures T<25 K, the temperature de pendent part of the resistance is approximated by rho(T) -rho(0) = AT( n). The power degree smoothly varies from 3.2 in high quality films de posited at 750 degrees C, where the effective electron mean free path exceeds film thickness to 4.5 in the films deposited onto cold unannea led substrates, where the effective electron mean free path is compara ble with film thickness. (C) 1997 American Institute of Physics.