Strain Engineering 2D MoS${}_2$ with Thin Film Stress Capping Layers

Abstract

We demonstrate a method to induce tensile and compressive strain into two-dimensional transition metal dichalcogenide (TMDC) MoS${}_2$ via the deposition of stressed thin films to encapsulate exfoliated flakes. With this technique we can directly engineer MoS${}_2$ strain magnitude by changing deposited thin film stress, therefore allowing variable strain to be applied on a flake-to-flake level. These thin film stressors are analogous to SiN${}_x$ based stressors implemented in industrial CMOS processes to enhance Si mobility, suggesting that our concept is highly scalable and may be applied for large-scale integration of strain engineered TMDC devices. We choose optically transparent stressors to allow us to probe MoS${}_2$ strain through Raman spectroscopy. Combining thickness dependent analyses of Raman peak shifts in MoS${}_2$ with atomistic simulations, we can explore layer-by-layer strain transfer. MoS${}_2$ on conventional substrates (SiO${}_2$, MgO) show strain transfer into the top two layers of multilayer flakes with limited strain transfer to monolayers due to substrate adhesion. To mitigate this limitation, we also explore stressors on van der Waals heterostructures constructed of monolayer (1L) MoS${}_2$ on hexagonal boron nitride (h-BN). This concept frees the 1L-MoS${}_2$ allowing for a 0.85$\%$ strain to be applied to the monolayer with a corresponding strain induced bandgap change of 75 meV. By using thin films with higher stress, strain may be engineered to be even higher. Various stressors and deposition methods are considered, showing a stressor material independent transfer of strain that only depends on stressor film force with negligible defects induced into MoS${}_2$ when thermal evaporation is used.

References in corpus (12)

• Bandgap Engineering of Strained Monolayer and Bilayer MoS2
• Symmetry-dependent phonon renormalization in monolayer MoS2 transistor
• Band Gap Engineering with Ultralarge Biaxial Strains in Suspended Monolayer MoS2
• Rapid and reliable thickness identification of two-dimensional nanosheets using optical microscopy
• Quantitative Raman Spectrum and Reliable Thickness Identification for Atomic Layers on Insulating Substrates
• Tunable stress and controlled thickness modification in graphene by annealing
• Control of Radiation Damage in MoS2 by Graphene Encapsulation
• Tuning Electronic and Magnetic Properties of Early Transition Metal Dichalcogenides via Tensile Strain
• Optical detection of strain and doping inhomogenieties in single layer MoS2
• Strain-Based Room-Temperature Non-Volatile MoTe${}_2$ Ferroelectric Phase Change Transistor
• Heterostrain engineering on twisted graphene bilayer around the first magic angle
• Stretching graphene using polymeric micro-muscles

Cited by in corpus (7)

• Strain-Enhanced Mobility of Monolayer MoS2
• Strain Engineering for High-Performance Phase Change Memristors
• CMOS-compatible Strain Engineering for High-Performance Monolayer Semiconductor Transistors
• Moiré Engineering in 2D Heterostructures with Process-Induced Strain
• Enhanced ferromagnetism in artificially stretched lattice in quasi two-dimensional Cr2Ge2Te6
• Geometrical properties of strained and twisted moiré heterostructures
• Scalable and deterministic construction of moiré superlattice in 2D materials using stressor films