Pressure-induced phase transition and bandgap collapse in the wide-bandgap semiconductor InTaO4

TL;DR

This study investigates how high pressure induces a phase transition and causes a bandgap collapse in InTaO4, combining experimental techniques and ab-initio calculations to understand structural and electronic changes.

Contribution

It reveals a pressure-induced phase transition in InTaO4 with detailed structural, vibrational, and electronic property analysis using combined experimental and computational methods.

Findings

Phase transition occurs beyond 13 GPa with a volume collapse.

Bandgap collapses during the phase transition.

A band crossing occurs near 7 GPa in the low-pressure phase.

Abstract

A pressure-induced phase transition, associated with an increase of the coordination number of In and Ta, is detected beyond 13 GPa in InTaO4 by combining synchrotron x-ray diffraction and Raman measurements in a diamond anvil cell with ab-initio calculations. High-pressure optical-absorption measurements were also carried out. The high-pressure phase has a monoclinic structure which shares the same space group with the low-pressure phase (P2/c). The structure of the high-pressure phase can be considered as a slight distortion of an orthorhombic structure described by space group Pcna. The phase transition occurs together with a unit-cell volume collapse and an electronic bandgap collapse observed by experiments and calculations. Additionally, a band crossing is found to occur in the low-pressure phase near 7 GPa. The pressure dependence of all the Raman-active modes is reported for both phases as well as the pressure dependence of unit-cell parameters and the equations of state. Calculations also provide information on IR-active phonons and bond distances. These findings provide insights into the effects of pressure on the physical properties of InTaO4.