Densities of Ge–Sb–Te Alloys

Ge–Sb–Te chalcogenide alloy has been widely investigated due to its applications in phase change random access memory (PCRAM). The density of Ge–Sb–Te alloy is a key factor for PCRAM applications. In this chapter, the densities of Sb2Te3 and Ge2Sb2Te5 chalcogenide alloys in solid and molten states have been determined as a function of temperature by the sessile drop method. The density at room temperature was also determined by the Archimedean method to verify the reliability of data obtained by the sessile drop method. The density of solid alloys decreases linearly with increasing temperature and there is a discontinuous density decrease at the melting temperature due to the phase change. In the molten state, the density continues to decrease with increasing temperature. The molar volume of both chalcogenide alloys increases by about 4% from room temperature to just below the melting temperature and by 6% at the melting temperature from the solid to molten state, which may cause large stress for PCRAM devices.