Tunable direct bandgap and optical response in \ch{Mo_{1-x}W_xS2} monolayer alloys: A first-principles investigation

• URL: http://arxiv.org/abs/2506.01464v1
• Date: Mon, 02 Jun 2025 09:20:39 GMT
• Title: Tunable direct bandgap and optical response in \ch{Mo_{1-x}W_xS2} monolayer alloys: A first-principles investigation
• Authors: Kevin Ndang Amassa, Jean-Pierre Tchapet Njafa, Anne Justine Etindele, Chetty Nithaya, Serge Guy Nana Engo,
• Abstract summary: This study explores the structural, electronic and optical properties of monolayer chMo_1-xW_xS2 alloys.<n>We establish that these alloys are thermodynamically stable and maintain the characteristic 2H crystal structure.<n>Our results validate the monolayer chMo_1-x W_xS2 as an electronically versatile platform.
• Score: 0.3495246564946556
• License: http://creativecommons.org/publicdomain/zero/1.0/
• Abstract: This study presents a comprehensive first-principles investigation of the structural, electronic and optical properties of monolayer \ch{Mo_{1-x}W_xS2} alloys, systematically exploring the full compositional range ($x=0$ to $1$) using density functional theory (DFT). We establish that these alloys are thermodynamically stable and maintain the characteristic 2H crystal structure with minimal structural perturbation upon alloying. A key finding is the preservation of a direct bandgap at the $K$-point across all compositions. This gap exhibits continuous tunability, increasing near-monotonically from \SI{1.696}{\electronvolt} (\ch{MoS2}) to \SI{1.858}{\electronvolt} (\ch{WS2}), a critical feature for tailoring optoelectronic devices. Electronic structure analysis reveals the systematic evolution of the orbital contributions of transition metal $d$ and sulfur $p$ at the edges of the band with composition. Consequently, the optical spectra, evaluated up to \SI{8}{\electronvolt}, show a progressive blueshift in the main features of the interband transition with increasing \ch{W} content, accompanied by predictable changes in key optical constants. Our comprehensive results validate the monolayer \ch{Mo_{1-x} W_xS2} as an electronically versatile platform that offers fine control over electronic and optical properties via alloying, making these tunable direct-gap semiconductors highly promising for next-generation photodetectors, light emitters, and potentially flexible optoelectronic applications exploiting their 2D nature.

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