Optical properties of laser-deposited a-Ge films: a comparison with sputtered and e-beam-deposited films

Optical properties of amorphous semiconductor films are usually strongly dependent on deposition conditions. To the best of our knowledge, this is the first publication on optical properties of amorphous Ge films that are grown by laser-assisted deposition and measured by means of spectroscopic ellipsometry over a wide spectral range (1.43-4.59 eV). Optical properties of dc magnetron-sputtered and e-beamdeposited films are also included. Effective medium modeling is used to analyze the void fraction and the film homogeneity through the thickness. The results show that laser-deposited films and dc magnetronsputtered films are similar, both being denser, more homogeneous, and more stable than e-beamdeposited films. Transmission electron microscopy analysis shows that the results of the optical study are correlated to the film structure. These results are discussed in terms of the kinetic energy of the species involved in each deposition technique and some conclusions related to the laser-assisted deposit on process are reported.