Multiple phase transitions in Sc doped Sb2Te3 amorphous nanocomposites under high pressure

Abstract

Subnanosecond switching speed from an amorphous state with stable crystal precursors to the crystalline state was recently achieved in amorphous Sc-doped Sb2Te3 (a-SST) phase change materials (PCMs), which is about two orders of magnitude faster than that in the well-studied Ge2Sb2Te5 and Ge1Sb2Te4 PCMs. However, the phase change mechanism and phase stability of a-SST remain unknown. Here, we prepared amorphous Sc0.3Sb2Te3 nanocomposites within a minute amount of face-centered-cubic (FCC) type nanograins embedded in the amorphous matrix. Using in situ high-pressure synchrotron X-ray diffraction, we found that nanograins were frustrated under high pressure and gradually dissolved into the matrix around 11.0 GPa. Beyond 11.0 GPa, the a-SST matrix transformed into a uniform high density metallic like amorphous state with a five orders of magnitude drop in electric resistivity compared to the pristine materials. When further compressed to 23.97 GPa, the high density amorphous (HDA) phase switched into a body-centered-cubic (BCC) high-pressure structure, a different phase from the ambient pressure crystalline structure. Upon decompression back to ambient pressure, a pure amorphous phase was sustained. The present study provides additional insight into the phase change mechanism of amorphous nanocomposites.

The Effect of Carbon Doping on the Crystal Structure and Electrical Properties of Sb2Te3

“…Sb 2 Te 3 has a fast reversible phase transition, which is due to its rich Te and vacancies in the face-centered cubic (FCC) phase [ 11 ]. Sb 2 Te 3 is considered one of the most advantageous candidate materials for PCRAM, but its thermal stability is poor [ 12 , 13 , 14 ]. In order to improve thermal stability while maintaining the advantages of its high crystallization speed, doping is a feasible means to improve the thermal stability of Sb 2 Te 3 [ 15 ].…”

Sb2Te3/TiTe2‐Heterostructure‐Based Phase Change Memory for Fast Set Speed and Low Reset Energy

“…[ 12–15 ] Second, the doping method is a method of improving device performance by adding dopants such as Ti, Ta, Sc, C, and N to the existing phase change memory material. [ 16–20 ] Finally, Sb 2 Te 3 /GeTe, crystalline Sb 2 Te 3 /TiTe 2 , GeTe/C, Ge 8 Sb 92 /Ge, C/Sb, Zn 15 Sb 85 /Ga 30 Sb 70 , and Cr 7 Ge 33 Te 60 /Hf 16 Ge 6 Sb 78 are constructed using two different materials to improve performance using two different properties. [ 21–35 ]…”