Effects of Hexagonal Boron Nitride Encapsulation on the Electronic Structure of Few-Layer MoS₂

Abstract

The hexagonal boron nitride (hBN) encapsulation has been widely used in the electronics applications of 2D materials to improve device performance by protecting 2D materials against contamination and degradation. It is often assumed that hBN layers as a dielectric would not affect the electronic structure of encapsulated 2D materials.Here we studied few-layer MoS 2 encapsulated in hBN flakes by using a combination of theoretical and experimental Raman spectroscopy. We found that after the encapsulation the out-of-plane A 1g mode is upshifted, while the in-plane E 1 2g mode is downshifted.The measured downshift of the E 1 2g mode does not decrease with increasing the thickness of MoS 2 , which can be attributed to tensile strains in bilayer and trilayer MoS 2 caused by the typical experimental process of the hBN encapsulation. We estimated the strain magnitude and found that the induced strain may cause the K-Q crossover in the conduction band of few-layer MoS 2 , so greatly modifies its electronic properties as an n-type semiconductor. Our study suggests that the hBN encapsulation should be 1 arXiv:1905.05493v2 [cond-mat.mtrl-sci] 16 May 2019 used with caution, as it may affect the electronic properties of encapsulated few-layer 2D materials.

Titanium disulfide as Schottky/ohmic contact for monolayer molybdenum disulfide

“…After creating a contact, the defects generated lower charge mobility 18 . To overcome this issue, some groups have utilized encapsulation technique, the MoS 2 mobility can be preserved by using hexagonal boron nitride (h-BN) nano sheets to enclose the MoS 2 sheet 19,20 . This encapsulation technique though increases the fabrication complexity of the devices which add difficulty for large-scale manufacturing.…”

Optoelectronic Properties of Monolayer Hexagonal Boron Nitride on Different Substrates Measured by Terahertz Time-Domain Spectroscopy

“…Hence, ML hBN has high conducting values compared to bulk or multi-layer hBN. More importantly, in recent years, ML hBN has been applied for the realization of van der Waals heterojunctions in combination with other 2D electronic systems such as graphene [9] and transition metal dichalcogenide (TMD) based 2D electronic systems [10]. ML hBN has been used as a dielectric substrate for graphene based electronic devices, owing to its unique characteristics like thermal stability and as an insulator [11].…”

Theoretical approach to point defects in a single transition metal dichalcogenide monolayer: conductance and force calculations in MoS 2

“…But in a second time, the discovery of graphene has also shed light on a whole world of new bidimensional materials. For example, hexagonal boron nitride (hBN) as the graphene counterpart made of boron and nitrogen is widely used due to its widegap and its encapsulation properties [5,6]. Also we have seen the emergence of the great family of transition metal dichalcogenides (TMDC), made of a transition metal layer sandwiched in between two chalcogen atom layers, and presenting several different properties [7][8][9][10].…”