摘要
The phase evolution of Bi 2 Se 2.1 Te 0.9 driven by the applied external pressure at ambient temperature was investigated in-situ with pressure up to 30.0(2) GPa using angle-dispersive X-ray diffraction (ADXRD) and Raman scattering spectroscopy. ADXRD measurements revealed that starting from the ambient rhombohedral structure (phase I), new forms of crystal structures are found to sequentially emerge with increasing externally applied pressure. Namely a seven-fold monoclinic structure (phase II), then an eight-fold monoclinic structure (phase III), a body-centered structure (BCC, phase IV), and finally a body-centered tetragonal structure (BCT, phase V) was observed at pressures of ~10.5(3) GPa, ~18.8(1) GPa, ~23.0(1) GPa, and ~28.0(2) GPa, respectively. The Raman scattering spectroscopy consistently showed that the pressures at which the corresponding phase appeared at ~10.2(2) GPa, ~18.9(1) GPa, and ~26.1(2) GPa, respectively. Moreover, the rhombohedral phase exhibited an even more pronounced signature of electronic topological transition in low-pressure regime, as compared with those previously observed in pristine Bi 2 Te 3 and Bi 2 Se 3. It appears that the alloying of Bi 2 Se 3 with Bi 2 Te 3 has led to more profound effects in the electronic and structural properties of the resultant system than that expected from the Vegard's law.