Cr-doped Sb2Te materials promising for high performance phase-change random access memory

Abstract

Transition metal doping is an effective strategy to improve the properties of phase-change random access memory (PCRAM), while the underlying mechanism remains to be sufficiently investigated. Herein, a Cr-doped Sb2Te film is fabricated by co-sputtering and the enhancement mechanism of Cr-doping is deeply investigated by experiments and first-principles calculations. The CrxSb2Te film exhibits excellent performances involving high crystallization temperature (238.9 °C) and good data retention (10 years @161.7 °C) for Cr0.56Sb2Te, low density change rate (3.8%) and high reversible switching speed (5 ns) for Cr0.29Sb2Te, providing a variety of options for different applications. The calculated results show that Cr atoms preferentially substitute the Sb1 site and the CrTe bonds display a stronger ionic bond character in contrast to the covalent bonded SbTe, thus improving the crystalline phase stability and crystallization temperature. Moreover, ab initio molecular dynamics simulations demonstrate that in the amorphous phase Cr atoms locate in defective octahedral coordination. Meanwhile, the homopolar SbSb wrong bond increased with Cr doping and the Cr atoms tend to form tight cluster in the amorphous phase which could benefit for the fast phase-change speed. Our present findings of Cr0.29Sb2Te PCRAM device clearly reveal the enhancement mechanism by Cr doping which provides guidance for developing high-performance PCRAM devices.