Correlation between crystal purity and the charge density wave in 1<i>T</i>-VSe₂

We discuss the charge density wave (CDW) properties of 1T-VSe₂ crystals grown by chemical vapour transport (CVT) under varying conditions [1]. We find that by lowering the growth temperature (T_g < 630°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 (XPS), we correlate the observed CDW properties with stoichiometry and the nature of defects. In addition, we have optimized a method to grow ultra-high purity 1T-VSe₂ crystals with T_CDW = (112.7 ± 0.8) K and maximum RRR value ∼ 49. Our work highlights the importance of carefully controlling the crystal growth conditions of strongly-correlated transition metal dichalcogenides.

[1] C. J. Sayers et al. Phys. Rev. Materials 4, 025002 (2020)