Abstract
The structural, vibrational and electronic properties of ZnSe under different pressure environments up to ∼40.0 GPa were investigated using a diamond anvil cell in conjunction with ac impedance spectroscopy, Raman spectroscopy and high–resolution transmission electron microscopy. Under the non–hydrostatic condition, ZnSe exhibited a structural phase transition from a zinc–blende to a cinnabar structure at ∼4.9 GPa, indicated by the obvious splitting of the transverse optical mode in the Raman spectra and a noticeable variation in the slope of the electrical conductivity. With increasing pressure, metallization appeared at ∼12.5 GPa, which was characterized by the high–pressure Raman spectroscopy and temperature–dependent electrical conductivity results. When the pressure was increased up to ∼30.0 GPa, another phase transition was identified by the appearance of a new peak in the Raman spectra. Compared to the non–hydrostatic condition, a roughly 2.0 GPa delay of transition pressure for ZnSe was observed at the hydrostatic condition. However, the structural phase transformation was found to be irreversible only under the non–hydrostatic condition. The unique properties displayed by ZnSe under different pressure environments may be attributed to the constrained interlayer interaction owing to the presence of the pressure medium.
Highlights
The pressure–induced phase transitions for some ZnX (X=O, S, Se and Te) types of semiconductors have become a fundamental topic in condensed matter physics owing to their extensive applications in the fields of optoelectronic devices.1–5 Zinc selenide (ZnSe) is a typical semiconductor with a direct band gap, and crystallizes into a zinc–blende (ZB) structure at ambient conditions
We report three phase transitions for ZnSe under both non–hydrostatic and hydrostatic conditions at pressures up to ∼40.0 GPa using a diamond anvil cell (DAC) in conjunction with impedance spectroscopy, Raman spectroscopy and high resolution transmission electron microscopy (HRTEM)
At 0.3 GPa, two prominent Raman peaks attributed to the transverse optical (TO) and the longitudinal optical (LO) phonon modes were observed at 204.9 and 251.6 cm−1, respectively, which was in good agreement with previous studies
Summary
The pressure–induced phase transitions for some ZnX (X=O, S, Se and Te) types of semiconductors have become a fundamental topic in condensed matter physics owing to their extensive applications in the fields of optoelectronic devices. Zinc selenide (ZnSe) is a typical semiconductor with a direct band gap, and crystallizes into a zinc–blende (ZB) structure at ambient conditions. Itkin et al have investigated the high pressure electrical property of ZnSe at 0–20 GPa using temperature–dependent electrical resistivity experiments, and further confirmed that ZnSe undergoes a metallization process from a semiconducting four–fold coordinated ZB structure to a six–fold coordinated metallic rock structure at pressures higher than 13.5 GPa.. Itkin et al have investigated the high pressure electrical property of ZnSe at 0–20 GPa using temperature–dependent electrical resistivity experiments, and further confirmed that ZnSe undergoes a metallization process from a semiconducting four–fold coordinated ZB structure to a six–fold coordinated metallic rock structure at pressures higher than 13.5 GPa.11 In addition to these experimental results, some theoretical calculation studies of the high pressure phase stability of ZnSe have been reported, and remain controversial. The high pressure phase stability of ZnSe under different pressure environments is discussed in detail
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