Correlation between crystal purity and the charge density wave in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>1</mml:mn><mml:mi>T</mml:mi><mml:mo>−</mml:mo><mml:msub><mml:mi>VSe</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>
C. J. Sayers, L. S. Farrar, S. J. Bending, M. Cattelan, A. J. H. Jones, N. A. Fox, G. Kociok-Köhn, K. Koshmak, J. Laverock, L. Pasquali, E. Da Como
Abstract
We examine the charge density wave (CDW) properties of $1T\ensuremath{-}{\mathrm{VSe}}_{2}$ crystals grown by chemical vapor transport (CVT) under varying conditions. Specifically, we find that upon lowering the growth temperature (${T}_{g}<{630}^{\phantom{\rule{0.16em}{0ex}}\ensuremath{\circ}}\mathrm{C}$), there is a significant increase in both the CDW transition temperature and the residual resistance ratio (RRR) obtained from electrical transport measurements. Using x-ray photoelectron spectroscopy, we correlate the observed CDW properties with stoichiometry and the nature of defects. In addition, we have optimized a method to grow ultrahigh-purity $1T\ensuremath{-}{\mathrm{VSe}}_{2}$ crystals with a CDW transition temperature ${T}_{\mathrm{CDW}}=(112.7\ifmmode\pm\else\textpm\fi{}0.8)$ K and maximum residual resistance ratio $\mathrm{RRR}\ensuremath{\approx}49$, which is the highest reported thus far. This work highlights the sensitivity of the CDW in $1T\ensuremath{-}{\mathrm{VSe}}_{2}$ to defects and overall stoichiometry and the importance of controlling the crystal growth conditions of strongly correlated transition metal dichalcogenides.