THE PREPARATION OF EPITAXIAL PLATINUM FILMS BY PULSED LASER DEPOSITION

A systematic study of the effects of ambient deposition pressure P(d) and substrate temperature T(s) on the morphology and crystal structure of platinum films deposited onto [100] MgO by pulsed laser deposition (PLD) is presented. Depositions were performed over a T(s) range of 20-650-degrees-C and a P(d) range of 10(-5)-1 Torr of O2. Different crystallographic orientations and a dramatic change in morphology were observed as a function of P(d) and T(s). For depositions performed at room temperature and for pressures greater than 10(-5) Torr, the films were comprised of mostly platinum oxide. At T(s) of 350-500-degrees-C and at all pressures studied, the platinum films were very smooth and oriented. At T(s) > 500-degrees-C. deposited films were characterized by islands whose average diameter varied from several nanometers to over a micrometer depending on the average film thickness; islands were prevalent P(d) greater-than-or-equal-to 0.05 Torr. Over the broad range of conditions examined, the film crystal structure varied from (100) epitaxy with a rocking curve width of less than 0.2-degrees, to films of mixed (100) and (111) preferred orientations. At a given T(s), the deposition rate per laser shot was found to depend on P(d). In general, the deposition rate was found to increase monotonically from about 0.1 angstrom per shot at 10(-5) Torr to a maximum of about 0.16 angstrom per shot near 0.05 Torr, then decrease to a minimum of about 0.08 angstrom per shot near 0.3 Torr and then increase again at pressures greater than 0.3 Torr. These effects can be explained in terms of a combination of gas dynamic processes and gas-surface interactions which occur between the platinum atoms and the oxygen molecules during deposition.