Optical properties of pulsed laser deposited bismuth films

Bismuth films are grown at room temperature onto Si substrates by pulsed laser deposition (PLD). Some films are deposited by de sputtering (DCS) for comparison. PLD films are smooth and show micron-sized laminar grains as opposed to DCS films which are rough and show nanometer-sized columnar grains. The optical properties of the films have been studied by means of spectroscopic ellipsometry in the 300-800 nm wavelength interval over a period of six months. The results show that the refractive index of PLD Bi films is independent of the film thickness, thus providing reliable data of the optical constants of Bi films. In addition, it is shown that PLD films exhibit an improved stability to oxidation probably related to their favorable microstructural properties. The thickness dependence of the refractive index in DCS films is related to their surface roughness, the results being improved by pulsed laser melting of these films. (C) 1996 American Institute of Physics.