Structural, optical and mechanical properties of Cr doped \b{eta}-Ga2O3 single crystals

TL;DR

This study investigates how chromium doping affects the structural, optical, and mechanical properties of beta-Ga2O3 single crystals, revealing increased hardness, specific optical absorption features, and evidence of Cr substitution at the atomic level.

Contribution

It provides detailed insights into the effects of Cr doping on beta-Ga2O3 single crystals, including structural defects, optical behavior, and mechanical strength, using various characterization techniques.

Findings

Cr doping introduces structural defects and alters optical absorption.

Cr doped crystals show increased hardness and decreased indentation modulus.

Evidence of Cr3+ substituting Ga3+ at octahedral sites confirmed by Raman and photoluminescence.

Abstract

Undoped and Cr doped \b{eta}-Ga2O3 (100) single crystals are grown by optical floating zone method. The full width at half maximum of rocking curve is found to be 106 arcsec for undoped Ga2O3 crystals whereas the 100 and 200 ppm of Cr doped Ga2O3 crystals display multiple rocking curves with large peak widths indicating the presence of structural defects. Raman measurements reveal broadening in the vibrational mode of ~ 350 cm-1 with a shoulder peak indicating the Cr3+ dopants preferentially substitute for Ga3+ at the octahedral sites. Further, the Cr doped Ga2O3 crystals display strong optical absorption bands about 420 and 597 nm in the UV-Vis spectroscopy. Moreover, the observation of sharp characteristic photoluminescence emission lines at 690 and 697 nm also confirms the Cr substitution in the doped crystals. The indentation hardness increases nearly linear from 13.0 to 17.9 GPa whilst the indentation modulus decreases from 224.9 to 202.4 GPa upon Cr doping of 200 ppm in \b{eta}-Ga2O3. The structural defects caused by the Cr doping interrupt the movement of indentation induced dislocations that results in the increase of hardness of the Cr doped \b{eta}-Ga2O3 (100) single crystals.