Effects of interlayer coupling on the excitons and electronic structures of WS2/hBN/MoS2 van der Waals heterostructures

• DOI: 10.1007/s12274-021-3774-4
• Publication Date: 2021-08-19T13:03:50Z
• Authors: Xudan Zhu; Junbo He; Rongjun Zhang; Chunxiao Cong; Yuxiang Zheng; Hao Zhang; Songyou Wang; Haibin Zhao; Meiping Zhu; Shanwen Zhang; Shaojuan Li; Liangyao Chen
• Keywords: 01 natural sciences; 7. Clean energy; 0104 chemical sciences

Inserting hexagonal boron nitride (hBN) as barrier layers into bilayer transition metal dichalcogenides heterointerface has been proved an efficient method to improve two dimensional tunneling optoelectronic device performance. Nevertheless, the physical picture of interlayer coupling effect during incorporation of monolayer (1L-) hBN is not explicit yet. In this article, spectroscopic ellipsometry was used to experimentally obtain the broadband excitonic and critical point properties of WS2/MoS2 and WS2/hBN/MoS2 van der Waals heterostructures. We find that 1L-hBN can only slightly block the interlayer electron transfer from WS2 layer to MoS2 layer. Moreover, insertion of 1L-hBN weakens the interlayer coupling effect by releasing quantum confinement and reducing efficient dielectric screening. Consequently, the exciton binding energies in WS2/hBN/MoS2 heterostructures blueshift comparing to those in WS2/MoS2 heterostructures. In this exciton binding energies tuning process, the reducing dielectric screening effect plays a leading role. In the meantime, the quasi-particle (QP) bandgap remains unchanged before and after 1L-hBN insertion, which is attributed to released quantum confinement and decreased dielectric screening effects canceling each other. Unchanged QP bandgap as along with blueshift exciton binding energies lead to the redshift exciton transition energies in WS2/hBN/MoS2 heterostructures.