Characterization of Ge15Sb85 phase change material grown by pulsed laser deposition

Abstract

The phase change material eutectic binary compound Ge15Sb85 thin films were prepared, for the first time, by pulsed laser deposition technique. Various parameters were changed to obtain amorphous thin films in very good quality. X-ray diffraction, scanning electron microscope and electrical measurements were used to test the quality of the deposited films. The parameters that were changed are: chamber atmosphere (from vacuum to 4 × 10−4 mbar argon gas pressure), target–substrate distance (from 6 to 8 cm), deposition frequency (from 5 to 20 Hz) and laser energy (from 130 to 210 mJ). Our results showed that the influence of the plume on the temperature of the substrate is very critical. Less is the temperature of the substrate better is the quality of the film and more amorphous it is. The increase in the substrate temperature increases the chance of forming small crystallites within the deposited film as was shown in most of the samples. Best results were obtained using the following deposition conditions: laser energy of 130 mJ, frequency of 10 Hz, distance of 6 cm and vacuum chamber (no argon gas was present). Under these conditions, completely homogeneous amorphous films with very close stoichiometry to the source target (Ge∼16Sb∼84), a phase transition temperature of around 215 °C and an energy band gap of 0.6 eV were obtained.