Ferroelectric properties of Ge2Sb2Te5 phase-change films

The aim of this work is to investigate the NaCl-type to a hexagonal phase transition in Ge2Sb2Te5 films using impedance and piezoresponse force microscopy (PFM) measurements. The temperature dependence of the capacitance shows an abrupt change with a maximum at the temperature of 259 °C, which corresponds to the end from a NaCl-type to a hexagonal transition. In addition, the reciprocal capacitance for temperatures above 259 °C shows the Curie–Weiss dependence, which is typical for ferroelectric materials. Application of the external electrical field increases the degree of polarization in the NaCl-type Ge2Sb2Te5 films which allowed observing the ferroelectric domains in PFM measurements.