Mechanical Stress Modulation of Resistance in MoS₂ Junctions

Abstract

Strain engineering is a powerful strategy to control the physical properties of material-enabling devices with enhanced functionality and improved performance. Here, we investigate a modulation of the transport behavior of the two-dimensional MoS2 junctions under the mechanical stress induced by a tip of an atomic force microscope (AFM). We show that the junction resistance can be reversibly tuned by up to 4 orders of magnitude by altering a tip-induced force. Analysis of the stress-induced evolution of the I–V characteristics indicates a combined effect of the tip-induced strain and strain gradient on the energy barrier height and profile. In addition, we show that the tip-generated flexoelectric effect leads to significant enhancement of the photovoltaic effect in the MoS2 junctions. A combination of the optical and mechanical stimuli facilitates reversible photomechanical tuning of resistance of the narrow-band 2D semiconductors and development of devices with an enhanced photovoltaic response.

Controlling the semiconductor–metal transition in Cu-intercalated TiSe2 by applying stress

“…For instance, using them, one can control a reversible semiconductor-to-metal transition in MoTe 2 thin films 79 or can reversibly tune an electrical resistance in two-dimensional MoS 2 junctions to enhance a photovoltaic effect. 80 High-pressure phases and effects can also be implemented in thin films, 81 since due to epitaxial misfit strains a stress of several GPa or higher can be easily generated. 82 For example, a high-pressure polymorph of GeCu 2 O 4 , which is normally stable above 4 GPa, was stabilized in epitaxial films deposited on MgAl 2 O 4 substrates.…”

Strong Piezoelectricity and Improved Rectifier Properties in Mono‐ and Multilayered CuInP2S6

“…To understand the tip force-improved current rectifying, we considered both intrinsic and extrinsic effects. [41,42] The extrinsic effects mainly include the changes in the tip-sample contact area and sample thickness, while the intrinsic effects are mainly related to the modification of the tunneling barrier due to the bandgap change or the piezoelectric/flexoelectric effect. The extrinsic effects are ruled out from the experiment of tunnelling current and the rectifying behavior at a progressively increasing tip force.…”

Recent Strategies for the Synthesis of Phase-Pure Ultrathin 1T/1T′ Transition Metal Dichalcogenide Nanosheets

“…Band structure engineering is a common strategy for tuning the physical properties of ultrathin TMD nanosheets, and the large-area basal plane ensures strong flexibility, − which renders strain a good choice for engineering bandstructures. Strain physically deforms M–X bonds, and theoretical calculations have predicted the effects of strain on the band structure, effective carrier mass, phase stability, and optical and electrical properties. , The mechanical strain was exerted using elastic substrates, TMD layer deformation, , pretreated bulges, − , gas pressure, , and AFM tips, − etc. However, TMD monolayer transferred on the polymer substrate tends to slip away when in-plane tensile strain is applied.…”

“…The AFM tip is tiny and rigid enough for conducting nanoindentation tests by compressing flexible 2D nanosheets to study their strain-induced mechanical properties 141,142,144 and electronic structural evolutions. 152,153 For example, the Young's modulus of 1T VS 2 flakes was measured using AFM tip indentation and was estimated at ∼44.4 GPa, which approaches the lower limit for 2D TMD families. 144 Extraordinarily, however, the moduli of suspended MoS 2 nanosheets could be as high as ∼330 GPa, which is comparable to that of graphene oxide.…”