Improved thermal stability of C-doped Sb2Te films by increasing degree of disorder for memory application

• The amorphous C atoms exist at grain boundaries and suppress the grain growth.
• The amorphous C phase increases the Tc, and Rc by the increase in disorder.
• The C-Sb-Te films exhibit a single hexagonal Sb2Te phase without phase separation.
• C37.4(Sb2Te)62.6 exhibits a reversible phase transformation behavior.
• The melting point of C37.4(Sb2Te)62.6 is only 353 °C, far smaller than Sb2Te (545 °C).

The structural stability of carbon (C) incorporated Sb2Te films was investigated during crystallization process. Variations in the transition temperature for the as-deposited films during crystallization show that these films exhibit their enhanced amorphous stability due to C incorporation, while more C content will lead to a difference in the degree of disorder in the crystalline state. XPS data reveals that C atoms do not bond with Sb and Te atoms and only present in the form of CC bonds. According to XRD and TEM results, C atoms presents amorphous and this can increase the degree of disorder in the crystalline films. The Sb2Te nanocrystals were surrounded by an amorphous C phase. A subsequent Raman analysis further provides the direct evidence of improvement in the degree of disorder in the crystalline state. The laser-induced crystallization process of C37.4(Sb2Te)62.6 reveals that the degree of disorder in the crystalline state is relatively high and the reliability during the repetitive laser melt-quenching cycles is confirmed with fast crystallization as well as a low melting point of only 353 °C. Increasing degree of disorder in the Sb2Te films by C addition can improve the phase-change behavior and make this film suitable for data storage applications.