Thermal stability of the Ti-Zr-Cu-Pd nano-glassy thin films

Abstract

Nano-glassy thin films consist of nanometer-sized glassy regions (clusters) with a structure corresponding to melt-quenched glasses and amorphous interfacial regions characterized by a reduced density, or locally enhanced free volume, and in many cases a modified chemical composition. Ti-Zr-Cu-Pd nano-glass thin films were synthesized by using direct current (DC) magnetron sputtering on Si substrates. The influence of the sputtering conditions (sputtering power and Ar gas pressure) on the nano- and microstructure of deposited films and on their thermal behavior was analyzed. The thin films were noted to exhibit a homogeneous amorphous structure when sputtered at low Ar pressure (0.2 Pa) and a nano-glass structure with various sizes of the glassy cluster at higher Ar pressures (0.5–0.8 Pa). By raising the Ar pressure, the average size of the glassy clusters was noted to decrease corresponding to an increase of the volume fraction of the interfacial regions. The glass transition and crystallization temperatures were determined by using differential scanning calorimetry (DSC) at heating rates up to 40 Kmin−1. The thermal stability of the thin films was studied by annealing at temperatures above the glass transition and crystallization temperatures. The microstructure of the thin films was studied by means of X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy. The results obtained indicate that the nano-glassy thin films exhibit higher thermal stability than homogeneous glassy thin films. The fact that an increase of the volume fraction of the interfacial component in nano-glassy thin films results in an ultra-stable thermal behavior is indicating that the presence of nano-glassy interfaces impedes crystallization.