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A Study on Indirect-Direct Bandgap Structures of 2D-layered Transition Metal Dichalcogenides by Laser Etching

2차원 층상 구조 전이금속 칼코겐화합물의 레이저 식각에 의한 직접-간접 띠간격 구조 연구

  • Moon, Eun-A (Department of Electricity, Chosun College of Science & Technology) ;
  • Ko, Pil-Ju (Department of Electrical Engineering, Chosun University)
  • 문은아 (조선이공대학교 전기학과) ;
  • 고필주 (조선대학교 전기공학과)
  • Received : 2016.07.20
  • Accepted : 2016.08.23
  • Published : 2016.09.01

Abstract

Single-layered transition metal dichalcogenides (TMDs) exhibit more interesting physical properties than those of bulk TMDs owing to the indirect to direct bandgap transition occurring due to quantum confinement. In this research, we demonstrate that layer-by-layer laser etching of molybdenum diselenide ($MoSe_2$) flakes could be controlled by varying the parameters employed in laser irradiation (time, intensity, interval, etc.). We observed a dramatic increase in the photoluminescence (PL) intensity (1.54 eV peak) after etching the samples, indicating that the removal of several layers of $MoSe_2$ led to a change from indirect to direct bandgap. The laser-etched $MoSe_2$ exhibited the single $MoSe_2$ Raman vibration modes at ${\sim}239.4cm^{-1}$ and ${\sim}295cm^{-1}$, associated to out-of-plane $A_{1g}$ and in-plane ${E^1}_{2g}$ Raman modes, respectively. These results indicate that controlling the number of $MoSe_2$ layers by laser etching method could be employed for optimizing the performance of nano-electronic devices.

Acknowledgement

Supported by : 조선대학교

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