[Paper Review] Mechanical properties of lateral transition metal dichalcogenide heterostructures

Sadegh Imani Yengejeh, William Wen+1 more|arXiv (Cornell University)|Sep 28, 2020

2D Materials and Applications41 references4 citations

TL;DR

This study investigates the mechanical properties of lateral transition metal dichalcogenide (TMD) heterostructures using density functional theory (DFT) calculations. It reveals that 1H/1T' heterostructures exhibit significantly reduced mechanical strength compared to pure phases, with structural phase engineering offering a tunable strategy to control stiffness in 2D materials for nanoelectromechanical applications.

ABSTRACT

Transition metal dichalcogenide (TMD) monolayers attract great attention due to their specific structural, electronic and mechanical properties. The formation of their lateral heterostructures allows a new degree of flexibility in engineering electronic and optoelectronic devices. However, the mechanical properties of the lateral heterostructures are rarely investigated. In this study, a comparative investigation on the mechanical characteristics of 1H, 1T' and 1H/1T' heterostructure phases of different TMD monolayers including molybdenum disulfide (MoS2) molybdenum diselenide (MoSe2), Tungsten disulfide (WS2), and Tungsten diselenide (WSe2) was conducted by means of density functional theory (DFT) calculations. Our results indicate that the lateral heterostructures have a relatively weak mechanical strength for all the TMD monolayers. The significant correlation between the mechanical properties of the TMD monolayers and their structural phases can be used to tune their stiffness of the materials. Our findings, therefore, suggest a novel strategy to manipulate the mechanical characteristics of TMDs by engineering their structural phases for their practical applications.

Motivation & Objective

• To understand the mechanical behavior of lateral TMD heterostructures, which are critical for flexible and stretchable nanoelectronic devices.
• To identify how structural phases (1H, 1T', and 1H/1T') influence mechanical strength in monolayer TMDs.
• To evaluate the mechanical response of MoS2, MoSe2, WS2, and WSe2 in lateral heterostructure configurations.
• To establish a design principle for tuning mechanical stiffness through phase engineering in 2D materials.

Proposed method

• Density functional theory (DFT) calculations were employed to compute mechanical properties including Young's modulus and fracture strength.
• Structural models of lateral heterostructures were constructed by interfacing 1H and 1T' phases of TMD monolayers.
• Total energy and stress calculations were used to assess mechanical stability and strain response under uniaxial loading.
• The mechanical properties were compared across different TMD systems: MoS2, MoSe2, WS2, and WSe2.
• The influence of interfacial strain and bond reconstruction at the 1H/1T' junction was analyzed to explain mechanical softening.

Experimental results

Research questions

• RQ1 How does the formation of lateral 1H/1T' heterostructures affect the mechanical strength of TMD monolayers compared to their pure phases?
• RQ2 What is the role of structural phase (1H vs. 1T') in determining the stiffness and fracture behavior of TMD heterostructures?
• RQ3 To what extent can mechanical properties be tuned by engineering the phase composition at the heterointerface?
• RQ4 Are there systematic trends in mechanical response across different TMD materials (MoS2, MoSe2, WS2, WSe2)?
• RQ5 What is the origin of mechanical softening in lateral TMD heterostructures?

Key findings

• Lateral 1H/1T' heterostructures exhibit significantly reduced mechanical strength compared to pure 1H or 1T' phases across all TMD monolayers studied.
• The mechanical strength of heterostructures is weakest at the 1H/1T' interface due to bond reconstruction and strain localization.
• Young's modulus values for 1H/1T' heterostructures are substantially lower than those of pristine 1H or 1T' phases, indicating reduced stiffness.
• The mechanical response varies systematically across TMD materials, with MoS2 and WS2 showing more pronounced softening than MoSe2 and WSe2.
• A strong correlation exists between structural phase and mechanical properties, enabling phase engineering as a viable strategy to tune stiffness.