Atomic Composition's Impact on TMD Alloy Properties—Theoretical and Experimental Insights into Mo_1-xW_xSe₂

Transition metal dichalcogenides (TMDs) are renowned for their tunable electronic properties, facilitated by quantum confinement effects and strong interfacial interactions [1,2]. TMD alloys, in particular, offer the advantage of continuously adjustable electronic bandgaps [3]. In this study, we investigate the impact of atomic composition on the structural, electronic, and optical characteristics of the 2D alloy Mo_1−xW_xSe₂. Several samples, with varying atomic compositions, underwent comprehensive analysis via atomic force microscopy (AFM), optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, Raman spectroscopy, and photoluminescence spectroscopy. Additionally, by employing local anodic oxidation via AFM, we crafted monolayer islands within the alloy, introducing controlled defects to probe their effects. The ability to tailor monolayer size, shape, and position was demonstrated, with atomic composition significantly influencing oxide island formation. Remarkably, the alloy with a 50% mixture of Mo and W exhibited the greatest stability under anodic oxidation conditions. Enhanced luminescence was observed in all monolayer island - 2D material heterostructures relative to pristine monolayers.<br/><br/>A detailed investigation of structural and electronic properties employed special quasi-random structures (SQS) and density functional theory (DFT). Notably, vacancy formation energies in Mo_0.5W_0.5Se₂ alloys were higher compared to MoSe₂ and WSe₂ structures, suggesting greater resistance to vacancy formation during local anodic oxidation.<br/><br/>Our findings highlight the potential of Mo_1−xW_xSe₂TMD alloys in nanophotonic and optoelectronic applications. Our approach bridges theoretical predictions with experimental validation, offering a comprehensive understanding of TMD alloy behavior.<br/><br/><b>Acknowledgments</b>: CNPq, FAPEMIG, CENAPAD-SP, LNLS (CNPEM), LNNano (CNPEM), LCPNano (UFMG) and INCT Nanocarbono.<br/><br/><b>References</b>:<br/>1 - Butler, S. Z. <i>et al</i>. <i>ACS nano</i>, <b>7(4)</b>, 2898-2926 (2013).<br/>2 - Radisavljevic, B. <i>et al</i>. <i>Nature nanotechnology</i>, <b>6(3)</b>, 147-150 (2011).<br/>3 - Xie, L. M. <i>Nanoscale</i>, <b>7(44)</b>, 18392-18401 (2015).