Supporting Information Development of Sb phase change memory thin films with high thermal stability and low resistance drift by alloying with Se

Sb86.6Se13.4, and Sb98.3Se1.7 thin films were verified by XRD as shown in Fig. S1. As for pure Sb2Se3 thin film (Fig. S1(a)) no peaks appear in the diffractogram of the 150 and 200 ℃-annealed samples. This indicates that these films are still amorphous. Orthorhombic Sb2Se3 (o-Sb2Se3) phase with space group 62 (Pnma) was found in the film annealed at 250 ℃ and above. However, Sb79.9Se20.1 thin films shows formation of trigonal Sb (t-Sb) structure with space group 166 (R-3m) in addition to this o-Sb2Se3 phase at 250 ℃ (Fig. S1 (b)). With temperature increase to 300 ℃, peak intensity increases, indicating that both phases gradually grow. The phase formation behavior of Sb86.6Se13.4 thin films slightly differs from the Sb79.9Se20.1 thin films (Fig. S1(c)). At 250 {degree sign}C, only the formation of crystalline t-Sb phase was observed in the Sb86.6Se13.4 thin films (Fig. S1(c)), while o-Sb2Se3 phase was formed at 300 {degree sign}C, in addition. Furthermore, there seems to be a slightly preferred orientation present in the o-Sb2Se3 of the Sb79.9Se20.1 and Sb86.6Se13.4 thin films, as the (112) reflection is the strongest peak. In the case of disordered crystallites, however, the (212) would be the strongest followed by the (112). However, as the Sb concentration further increases (Fig. S1 (d)), the phase formation process completely changes in Sb98.3Se1.7 thin film. It was found that the formation of crystalline o-Sb2Se3 was completely suppressed and only t-Sb phase was formed. In addition, Fig. S1(d) reveals the formation of highly textured Sb98.3Se1.7 thin film with strong (001) texture. The grain size was estimated by the Scherrer formula1: （1） where Dhkl is the average thickness of the grain perpendicular to the sample surface (also known as the grain size), β is the full width at half maximum (FWHM) value in radian, λ is the wavelength of Cu Kα, and θ represents the Bragg diffraction angle.2 The FWHM of the diffraction peak is inversely related to the average crystallite size. The estimated average grain size of Sb grains is 16.85 nm and of Sb2Se3 grains is 9.84 nm.