Nano-Scanning Calorimetry Applied to Phase Change Processes in GeTe Thin Films

Abstract

The parallel nano-scanning calorimeter (PnSC) is a device for calorimetric measurement of nanoscale materials. Compared with traditional scanning calorimetry of bulk materials, PnSC has a faster heating rate and higher sensitivity when testing small masses of samples. Here, nano-scanning calorimetry is used to investigate the phase transition behavior of germanium telluride (GeTe). Amorphous GeTe is deposited on the heating element of PnSC, and the sample is analyzed in the process of heating crystallization. At a heating rate of approximately 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\text{3}}$</tex-math> </inline-formula> K/S, the amorphous deposited GeTe changes to rhombic GeTe at 185 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> C and to cubic GeTe as the temperature continues to rise to 412 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> C. The phase change process of GeTe was also determined using conventional differential scanning calorimetry (DSC). The obtained phase change enthalpies and phase change temperatures were compared with those determined by nano-scanning calorimetry. The composition of the low and high-temperature phases was determined by X-ray diffraction and Raman spectroscopy.