同位体を調整することで、半導体を工学化する有望なアプローチに光が当たる(Tweaking isotopes sheds light on promising approach to engineer semiconductors)

2024-05-03 オークリッジ国立研究所(ORNL)

＜関連情報＞

• https://www.ornl.gov/news/tweaking-isotopes-sheds-light-promising-approach-engineer-semiconductors
• https://www.science.org/doi/10.1126/sciadv.adj0758

単層遷移金属ダイカルコゲナイド半導体の光バンドギャップに対する異常な同位体効果 Anomalous isotope effect on the optical bandgap in a monolayer transition metal dichalcogenide semiconductor

YILING YU, VOLODYMYR TURKOWSKI, JORDAN A. HACHTEL, ALEXANDER A. PURETZKY, […], AND KAI XIAO
Science Advances  Published:21 Feb 2024
DOI:https://doi.org/10.1126/sciadv.adj0758

Abstract

Isotope effects have received increasing attention in materials science and engineering because altering isotopes directly affects phonons, which can affect both thermal properties and optoelectronic properties of conventional semiconductors. However, how isotopic mass affects the optoelectronic properties in 2D semiconductors remains unclear because of measurement uncertainties resulting from sample heterogeneities. Here, we report an anomalous optical bandgap energy red shift of 13 (±7) milli–electron volts as mass of Mo isotopes is increased in laterally structured ¹⁰⁰MoS₂–⁹²MoS₂ monolayers grown by a two-step chemical vapor deposition that mitigates the effects of heterogeneities. This trend, which is opposite to that observed in conventional semiconductors, is explained by many-body perturbation and time-dependent density functional theories that reveal unusually large exciton binding energy renormalizations exceeding the ground-state renormalization energy due to strong coupling between confined excitons and phonons. The isotope effect on the optical bandgap reported here provides perspective on the important role of exciton-phonon coupling in the physical properties of two-dimensional materials.