Pulsed laser deposition of lanthanum monosulfide thin films on silicon substrates

Thin films of lanthanum monosulfide (LaS) have been successfully deposited on Si substrates by pulsed laser deposition. The values of deposition parameters (chamber pressure, substrate temperature, substrate-to-target separation, laser energy, repetition rate, and spot size on the target) leading to a successful growth of films in their cubic rocksalt structure are identified. The films are golden yellow in appearance with a mirror-like surface morphology and possess a sheet resistance around 0.1 Omega/square. X-ray diffraction analysis of thick films (several microns) leads to a lattice constant of 5.863(7) Angstrom, which is close to the bulk LaS value. High-resolution transmission electron microscopy reveals the films to be comprised of nanocrystalline regions separated by amorphous ones. The root-mean-square variation of film surface roughness measured over a 1 mum x 1 mum area is found to be 1.74 nm by atomic force microscopy. These films have potential for semiconductor, vacuum microelectronics, and optoelectronics applications. (C) 2005 American Vacuum Society.