Experimental and Theoretical Studies of the Electronic Band Structure of Bulk and Atomically Thin Mo1- x W x Se2 Alloys

Jan Kopaczek; Tomasz Woźniak; Magdalena Tamulewicz-Szwajkowska; Szymon J Zelewski; Jarosław Serafińczuk; Paweł Scharoch; Robert Kudrawiec

doi:10.1021/acsomega.1c02788

Experimental and Theoretical Studies of the Electronic Band Structure of Bulk and Atomically Thin Mo_{1- x} W _x Se₂ Alloys

ACS Omega. 2021 Jul 15;6(30):19893-19900. doi: 10.1021/acsomega.1c02788. eCollection 2021 Aug 3.

Authors

Jan Kopaczek¹, Tomasz Woźniak¹, Magdalena Tamulewicz-Szwajkowska², Szymon J Zelewski¹, Jarosław Serafińczuk², Paweł Scharoch¹, Robert Kudrawiec¹

Affiliations

¹ Department of Semiconductor Materials Engineering, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland.
² Department of Nanometrology, Wroclaw University of Science and Technology, Janiszewskiego 11/17, 50-372 Wroclaw, Poland.

Abstract

We present studies focused on the evolution of the electronic band structure of the Mo_1-x W _x Se₂ alloy with the tungsten content, which was conducted by combining experimental and theoretical methods. Employed spectroscopic techniques, namely, photoreflectance, photoacoustic spectroscopy, and photoluminescence, allowed observing indirect and direct transitions at high and beyond high-symmetry points of the Brillouin zone (BZ). Two excitons (A and B) associated with the K point of the BZ were observed together with other optical transitions (C and D) related to band nesting. Moreover, we have also identified the indirect transition for the studied crystals. Obtained energies for all transitions were tracked with a tungsten content and compared with results of calculations performed within density functional theory. Furthermore, based on the mentioned comparison, optical transitions were assigned to specific regions of the BZ. Finally, we have obtained bowing parameters for experimentally observed features, for, i.e., thin-film samples: b(A) = 0.13 ± 0.03 eV, b(B) = 0.14 ± 0.03 eV, b(C) = 0.044 ± 0.008 eV, and b(D) = 0.010 ± 0.003 eV.