High-pressure behavior of superconducting boron-doped diamond

TL;DR

This study explores how high pressure affects the structure and properties of superconducting boron-doped diamond, revealing phase changes and correlations with superconducting transition temperature.

Contribution

It provides new insights into the high-pressure structural behavior and electronic vibrational changes in boron-doped diamond using Raman and x-ray techniques.

Findings

Irreversible phase change at 14 GPa in grain boundaries

Correlation between vibrational mode shifts and $T_{c}$ pressure coefficient

High bulk modulus of 510 GPa for BDD film

Abstract

This work investigates the high-pressure structure of freestanding superconducting ($T_{c}$ = 4.3\,K) boron doped diamond (BDD) and how it affects the electronic and vibrational properties using Raman spectroscopy and x-ray diffraction in the 0-30\,GPa range. High-pressure Raman scattering experiments revealed an abrupt change in the linear pressure coefficients and the grain boundary components undergo an irreversible phase change at 14\,GPa. We show that the blue shift in the pressure-dependent vibrational modes correlates with the negative pressure coefficient of $T_{c}$ in BDD. The analysis of x-ray diffraction data determines the equation of state of the BDD film, revealing a high bulk modulus of $B_{0}$=510$\pm$28\,GPa. The comparative analysis of high-pressure data clarified that the sp$^{2}$ carbons in the grain boundaries transform into hexagonal diamond.