Probing Evolution of Local Strain at MoS2-Metal Boundaries by Surface-Enhanced Raman Scattering

Monolayer Short-Channel Transistors Defined by Nonmetallic van der Waals Contact

Two-dimensional (2D) semiconductors have excellent immunity to short-channel effects and are therefore promising for ultrascaled field-effect transistors. However, ultrascaled transistors necessitate simultaneous minimization of the channel length and contact resistance, which is a significant challenge for atomically thin 2D semiconductors. In this work, a facile angle evaporation technique is developed to fabricate ultrashort channel monolayer 2D transistors with nonmetallic van der Waals (vdW) contacts. By precisely controlling the evaporation angle and the thickness of the physical vapor deposition-grown nonmetallic PbTe, which owns ultrasharp edges due to its perfect and stable periodic crystal structure, the channel length of 2D transistors can be controlled reproducibly. Moreover, due to the nonmetallic contact properties of PbTe, there are negligible metal-induced gap states (MIGS) between PbTe and 2D semiconductors; thus, almost no additional Fermi-level pinning (FLP) at the heterostructure interface. The short-channel MoS2 transistor with PbTe vdW contact exhibits superior performance, including excellent ohmic contacts, near-Boltzmann-limit subthreshold swing, high on/off current ratio (∼109), and negligible drain-induced barrier lowering (∼82 mV V-1). In addition, the device can also operate at a low voltage of 0.01 V with a desirable on/off ratio of ∼108, providing a facile technique to fabricate 2D material-based low-power ultra-scaled transistors.

Tailoring SERS sensitivity in AgNWs-ZIF-67 substrates: Effects of MOF thickness and probe-pore size matching

In this study, we develop a filter paper-supported Ag nanowire (AgNWs) substrate coated with a tunable layer of zeolitic imidazolate framework-67 (ZIF-67) metal-organic framework (MOF) for surface-enhanced Raman scattering (SERS) applications. The thickness of the ZIF-67 layer is precisely controlled by adjusting the soaking time, allowing us to investigate the influence of MOF thickness on SERS performance using probes with different sizes. Sensitivity for large, impenetrable molecules such as thiram and rhodamine 6G (R6G) are primarily governed by localized surface plasmon resonance (LSPR), while smaller, penetrable molecules like 4-mercaptobenzoic acid (4-MBA) exhibit enhanced sensitivity driven by charge transfer (CT) effects due to their ability to penetrate the MOF layer. A finite-difference time-domain (FDTD) simulation reveals that the porous structure of ZIF-67 facilitates electric field propagation to the probe, maintaining significant LSPR effects even beyond 200 nm from the AgNWs. Practical applicability is demonstrated using a wiping mode to detect thiram spiked on apple surfaces, with reliable linear detection achieved across a wide range of concentrations. This study underscores the potential of MOF-based hybrid SERS substrates for real-world applications, leveraging the complementary roles of CT and electromagnetic (EM) mechanisms to enhance sensitivity.

Active Surface-Enhanced Raman Scattering Platform Based on a 2D Material-Flexible Nanotip Array

Two-dimensional materials with a nanostructure have been introduced as promising candidates for SERS platforms for sensing application. However, the dynamic control and tuning of SERS remains a long-standing problem. Here, we demonstrated active tuning of the enhancement factor of the first- and second-order Raman mode of monolayer (1L) MoS2 transferred onto a flexible metallic nanotip array. Using mechanical strain, the enhancement factor of 1L MoS2/nanotip is modulated from 1.23 to 8.72 for 2LA mode. For the same mode, the SERS intensity is enhanced by ~31 times when silver nanoparticles of ~13 nm diameter are deposited on 1L MoS2/nanotip, which is tuned up to ~34 times by compressive strain. The change in SERS enhancement factor is due to the decrease (increase) in gap width as the sample is bent inwardly (outwardly). This is corroborated by FEM structural and electromagnetic simulation. We also observed significant control over mode peak and linewidth, which may have applications in biosensing, chemical detection, and optoelectronics.

Atomic-Scale Distribution and Evolution of Strain in Pt Nanoparticles Grown on MoS2 Nanosheet

Interface strain significantly affects the band structure and electronic states of metal-nanocrystal-2D-semiconductor heterostructures, impacting system performance. While transmission electron microscopy (TEM) is a powerful tool for studying interface strain, its accuracy may be compromised by sample overlap in high-resolution images due to the unique nature of the metal-nanocrystals-2D-semiconductors heterostructure. Utilizing digital dark-field technology, the substrate influence on metal atomic column contrasts is eliminated, improving the accuracy of quantitative analysis in high-resolution TEM images. Applying this method to investigate Pt on MoS2 surfaces reveals that the heterostructure introduces a tensile strain of ≈3% in Pt nanocrystal. The x-directional linear strain in Pt nanocrystals has a periodic distribution that matches the semi-coherent interface between Pt nanocrystals and MoS2, while the remaining strain components localize mainly on edge atomic steps. These results demonstrate an accurate and efficient method for studying interface strain and provide a theoretical foundation for precise heterostructure fabrication.

Changes of phonon modes and electron transfer induced by interface interactions of Pd/MoS2 heterostructures

As functional materials and nano-catalysts, Pd nanoparticles (NPs) are often used to modify two-dimensional (2D) materials. In the heterostructures of metal NPs and 2D transition metal dichalcogenides, the interface atomic configuration and interface effect greatly affect material properties and stability. Therefore, the rational design of interface structures and in-depth analysis of interface interactions are of vital importance for the preparation of specific functional devices. In this work, Pd NPs were deposited on mechanically exfoliated MoS2 flakes and the epitaxial relationship between Pd and MoS2 was observed, accompanied by distinct moiré patterns. Raman spectra of the Pd NPs/MoS2 heterostructure showed an E12g' vibration mode indicative of the local strain in MoS2. A new vibration mode A'1g appeared in the higher-frequency direction compared with the pristine A1g peak. Combined with X-ray photoelectron spectra and density functional theory calculations, the new vibration mode can be attributed to the bonding between Pd and MoS2. Besides, graphene was inserted between Pd NPs and MoS2, and the decoupling of the interfacial effect by graphene was investigated. This study will help deepen our understanding on the interaction mechanism between metals and MoS2, thereby enabling the modulation of optoelectronic properties and the performance of these hybrid materials.

Investigation on Contact Properties of 2D van der Waals Semimetallic 1T-TiS2/MoS2 Heterojunctions

Two-dimensional transition metal dichalcogenides (2D TMDCs) are considered promising alternatives to Si as channel materials because of the possibility of retaining their superior electronic transport properties even at atomic body thicknesses. However, the realization of high-performance 2D TMDC field-effect transistors remains a challenge owing to Fermi-level pinning (FLP) caused by gap states and the inherent high Schottky barrier height (SBH) within the metal contact and channel layer. This study demonstrates that high-quality van der Waals (vdW) heterojunction-based contacts can be formed by depositing semimetallic TiS2 onto monolayer (ML) MoS2. After confirming the successful formation of a TiS2/ML MoS2 heterojunction, the contact properties of vdW semimetal TiS2 were thoroughly investigated. With clean interfaces of the TiS2/ML MoS2 heterojunctions, atomic-layer-deposited TiS2 can induce gap-state saturation and suppress FLP. Consequently, compared with conventional evaporated metal electrodes, the TiS2/ML MoS2 heterojunctions exhibit a lower SBH of 8.54 meV and better contact properties. This, in turn, substantially improves the overall performance of the device, including its on-current, subthreshold swing, and threshold voltage. Furthermore, we believe that our proposed strategy for vdW-based contact formation will contribute to the development of 2D materials used in next-generation electronics.

Direct Characterization of Buried Interfaces in 2D/3D Heterostructures Enabled by GeO2 Release Layer

Inconsistent interface control in devices based on two-dimensional materials (2DMs) has limited technological maturation. Astounding variability of 2D/three-dimensional (2D/3D) interface properties has been reported, which has been exacerbated by the lack of direct investigations of buried interfaces commonly found in devices. Herein, we demonstrate a new process that enables the assembly and isolation of device-relevant heterostructures for buried interface characterization. This is achieved by implementing a water-soluble substrate (GeO2), which enables deposition of many materials onto the 2DM and subsequent heterostructure release by dissolving the GeO2 substrate. Here, we utilize this novel approach to compare how the chemistry, doping, and strain in monolayer MoS2 heterostructures fabricated by direct deposition vary from those fabricated by transfer techniques to show how interface properties differ with the heterostructure fabrication method. Direct deposition of thick Ni and Ti films is found to react with the monolayer MoS2. These interface reactions convert 50% of MoS2 into intermetallic species, which greatly exceeds the 10% conversion reported previously and 0% observed in transfer-fabricated heterostructures. We also measure notable differences in MoS2 carrier concentration depending on the heterostructure fabrication method. Direct deposition of thick Au, Ni, and Al2O3 films onto MoS2 increases the hole concentration by >1012 cm-2 compared to heterostructures fabricated by transferring MoS2 onto these materials. Thus, we demonstrate a universal method to fabricate 2D/3D heterostructures and expose buried interfaces for direct characterization.

Resonance-Assisted Surface-Enhanced Raman Spectroscopy Amplification on Hierarchical Rose-Shaped MoS2/Au Nanocomposites

Surface-enhanced Raman spectroscopy (SERS) has emerged as a highly sensitive trace detection technique in recent decades, yet its exceptional performance remains elusive in semiconductor materials due to the intricate and ambiguous nature of the SERS mechanism. Herein, we have synthesized MoS2 nanoflowers (NFs) decorated with Au nanoparticles (NPs) by hydrothermal and redox methods to explore the size-dependence SERS effect. This strategy enhances the interactions between the substrate and molecules, resulting in exceptional uniformity and reproducibility. Compared to the unadorned Au nanoparticles (NPs), the decoration of Au NPs induces an n-type effect on MoS2, resulting in a significant enhancement of the SERS effect. This augmentation empowers MoS2 to achieve a low limit of detection concentration of 2.1 × 10-9 M for crystal violet (CV) molecules and the enhancement factor (EF) is about 8.52 × 106. The time-stability for a duration of 20 days was carried out, revealing that the Raman intensity of CV on the MoS2/Au-6 substrate only exhibited a reduction of 24.36% after undergoing aging for 20 days. The proposed mechanism for SERS primarily stems from the synergistic interplay among the resonance of CV molecules, local surface plasma resonance (LSPR) of Au NPs, and the dual-step charge transfer enhancement. This research offers comprehensive insights into SERS enhancement and provides guidance for the molecular design of highly sensitive SERS systems.

Controlled Growth of Pd Nanocrystals by Interface Interaction on Monolayer MoS2: An Atom-Resolved in Situ Study

The crystal growth kinetics is crucial for the controllable preparation and performance modulation of metal nanocrystals (NCs). However, the study of growth mechanisms is significantly limited by characterization techniques, and it is still challenging to in situ capture the growth process. Real-time and real-space imaging techniques at the atomic scale can promote the understanding of microdynamics for NC growth. Herein, the growth of Pd NCs on monolayer MoS2 under different atmospheres was in situ studied by environmental transmission electron microscopy. Introducing carbon monoxide can modulate the diffusion of Pd monomers, resulting in the epitaxial growth of Pd NCs with a uniform orientation. The electron energy loss spectroscopy and theoretical calculations showed that the CO adsorption assured the specific exposed facets and good uniformity of Pd NCs. The insight into the gas-solid interface interaction and the microscopic growth mechanism of NCs may shed light on the precise synthesis of NCs on two-dimensional (2D) materials.

Synergistic Photon Management and Strain-Induced Band Gap Engineering of Two-Dimensional MoS2 Using Semimetal Composite Nanostructures

2D MoS₂ attracts increasing attention for its application in flexible electronics and photonic devices. For 2D material optoelectronic devices, the light absorption of the molecularly thin 2D absorber would be one of the key limiting factors in device efficiency, and conventional photon management techniques are not necessarily compatible with them. In this study, we show two semimetal composite nanostructures deposited on 2D MoS₂ for synergistic photon management and strain-induced band gap engineering: (1) the pseudo-periodic Sn nanodots, (2) the conductive SnO_x (x < 1) core-shell nanoneedle structures. Without sophisticated nanolithography, both nanostructures are self-assembled from physical vapor deposition. Optical absorption enhancement spans from the visible to the near-infrared regime. 2D MoS₂ achieves >8× optical absorption enhancement at λ = 700-940 nm and 3-4× at λ = 500-660 nm under Sn nanodots, and 20-30× at λ = 700-900 nm under SnO_x (x < 1) nanoneedles. The enhanced absorption in MoS₂ results from strong near-field enhancement and reduced MoS₂ band gap due to the tensile strain induced by the Sn nanostructures, as confirmed by Raman and photoluminescence spectroscopy. Especially, we demonstrate that up to 3.5% biaxial tensile strain is introduced to 2D MoS₂ using conductive nanoneedle-structured SnO_x (x < 1), which reduces the band gap by ∼0.35 eV to further enhance light absorption at longer wavelengths. To the best of our knowledge, this is the first demonstration of a synergistic triple-functional photon management, stressor, and conductive electrode layer on 2D MoS₂. Such synergistic photon management and band gap engineering approach for extended spectral response can be further applied to other 2D materials for future 2D photonic devices.

α-Fe2O3-supported Co3O4 nanoparticles to construct highly active interfacial oxygen vacancies for ozone decomposition

Ozone pollution has become one of the most concerned environmental issue. Developing low-cost and efficient catalysts is a promising alternative for ozone decomposition. This work presents a creative strategy that using α-Fe₂O₃-supported Co₃O₄ nanoparticles for constructing interfacial oxygen vacancies (Vo) to remove ozone. The efficiency of Co₃O₄/α-Fe₂O₃ was superior to that of pure α-Fe₂O₃ by nearly two times for 200-ppm ozone removal after 6-h reaction at 25 °C, which is ascribed to the highly active interfacial Vo. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy suggest that the Fe³⁺-Vo-Co²⁺ was formed when Co₃O₄ was loaded in α-Fe₂O₃. Furthermore, the density functional theory (DFT) calculations reveal the desorption and electron transfer ability of intermediate peroxide (O₂^2-) on Fe³⁺-Vo-Co²⁺ are higher than the Vo from other regions. In situ diffuse reflectance Fourier transform (DRIFT) spectroscopy also demonstrate the higher conversion rate of O₂^2- on Co₃O₄/α-Fe₂O₃. Base on the intermediates detected, we propose a recycle mechanism of interfacial Vo for ozone removal: O₂^2- is quickly converted to O₂^- and transformed into O₂ on interfacial Vo. Moreover, O₂-temperature-programmed desorption (TPD), H₂-temperature-programmed reduction (TPR), and electrochemical impedance spectroscopy (EIS) reveal that the oxygen mobility, reducibility, and conductivity of Co₃O₄/α-Fe₂O₃ are greatly superior to those of α-Fe₂O₃, which is contributed to the conversion of O₂^2-. Consequently, our proposed strategy effectively enhances the activity and stability of the bimetallic transition oxides for ozone decomposition.

A hydrophilic carbon foam/molybdenum disulfide composite as a self-floating solar evaporator

Solar-driven interfacial evaporation has gained increasing attention as an emerging and sustainable technology for wastewater treatment and desalinization. The carbon/molybdenum disulfide (C/MoS₂) composite has attracted more attention due to its outstanding light absorption capability and optoelectronic properties as a solar steam generator. However, the hydrophobic nature of carbon and MoS₂-based materials hinders their wettability, which is crucial to the effective and facile operation of a solar generator of steam. Herein, a pH-controlled hydrothermal method was utilized to deposit a promising photothermal MoS₂ coating on melamine-derived carbon foams (CFs). The hydrophilic CF/MoS₂ composite, which can easily be floatable on the water surface, is a high-efficiency solar steam evaporator with a rapid increase in temperature under photon irradiation. Due to the localized heat confinement effect, the self-floating composite foam on the surface of water has the potential to produce a significant temperature differential. The porous structure effectively facilitates fast water vapor escape, leading to an impressively high evaporation efficiency of 94.5% under a light intensity of 1000 W m^-2.

Insight into the Heterogeneity of Longitudinal Plasmonic Field in a Nanocavity Using an Intercalated Two-Dimensional Atomic Crystal Probe with a ∼7 Å Resolution

Quantitative measurement of the plasmonic field distribution is of great significance for optimizing highly efficient optical nanodevices. However, the quantitative and precise measurement of the plasmonic field distribution is still an enormous challenge. In this work, we design a unique nanoruler with a ∼7 Å spatial resolution, which is based on a two-dimensional atomic crystal where the intercalated monolayer WS₂ is a surface-enhanced Raman scattering (SERS) probe and four layers of MoS₂ are a reference layer in a nanoparticle-on-mirror (NPoM) structure to quantitatively and directionally probe the longitudinal plasmonic field distribution at high permittivity by the quantitative SERS intensity of WS₂ located in different layers. A subnanometer two-dimensional atomic crystal was used as a spacer layer to overcome the randomness of the molecular adsorption and Raman vibration direction. Combined with comprehensive theoretical derivation, numerical calculations, and spectroscopic measurements, it is shown that the longitudinal plasmonic field in an individual nanocavity is heterogeneously distributed with an unexpectedly large intensity gradient. We analyze the SERS enhancement factor on the horizontal component, which shows a great attenuation trend in the nanocavity and further provides precise insight into the horizontal component distribution of the longitudinal plasmonic field. We also provide a direct experimental verification that the longitudinal plasmonic field decays more slowly in high dielectric constant materials. These precise experimental insights into the plasmonic field using a two-dimensional atomic crystal itself as a Raman probe may propel understanding of the nanostructure optical response and applications based on the plasmonic field distribution.

Thin-layered MoS2 nanoflakes vertically grown on SnO2 nanotubes as highly effective room-temperature NO2 gas sensor

The unique properties of heterostructure materials make them become a promising candidate for high-performance room-temperature (RT) NO₂ sensing. Herein, a p-n heterojunction consisting of two-dimensional (2D) MoS₂ nanoflakes vertically grown on one-dimensional (1D) SnO₂ nanotubes (NTs) was fabricated via electrospinning and subsequent hydrothermal route. The sulfur edge active sites are fully exposed in the MoS₂@SnO₂ heterostructure due to the vertically oriented thin-layered morphology features. Moreover, the interface of p-n heterojunction provides an electronic transfer channel from SnO₂ to MoS₂, which enables MoS₂ act as the generous electron donor involved in NO₂ gas senor detection. As a result, the optimized MoS₂@SnO₂-2 heterostructure presents an impressive sensitivity and selectivity for NO₂ gas detection at RT. The response value is 34.67 (R_a/R_g) to 100 ppm, which is 26.5 times to that of pure SnO_2. It also exhibits a fast response and recovery time (2.2 s, 10.54 s), as well as a low detection limit (10 ppb) and as long as 20 weeks of stability. This simple fabrication of high-performance sensing materials may facilitate the large-scale production of RT NO₂ gas sensors.

Ultralow contact resistance between semimetal and monolayer semiconductors

Advanced beyond-silicon electronic technology requires both channel materials and also ultralow-resistance contacts to be discovered^1,2. Atomically thin two-dimensional semiconductors have great potential for realizing high-performance electronic devices^1,3. However, owing to metal-induced gap states (MIGS)^4-7, energy barriers at the metal-semiconductor interface-which fundamentally lead to high contact resistance and poor current-delivery capability-have constrained the improvement of two-dimensional semiconductor transistors so far^2,8,9. Here we report ohmic contact between semimetallic bismuth and semiconducting monolayer transition metal dichalcogenides (TMDs) where the MIGS are sufficiently suppressed and degenerate states in the TMD are spontaneously formed in contact with bismuth. Through this approach, we achieve zero Schottky barrier height, a contact resistance of 123 ohm micrometres and an on-state current density of 1,135 microamps per micrometre on monolayer MoS₂; these two values are, to the best of our knowledge, the lowest and highest yet recorded, respectively. We also demonstrate that excellent ohmic contacts can be formed on various monolayer semiconductors, including MoS₂, WS₂ and WSe₂. Our reported contact resistances are a substantial improvement for two-dimensional semiconductors, and approach the quantum limit. This technology unveils the potential of high-performance monolayer transistors that are on par with state-of-the-art three-dimensional semiconductors, enabling further device downscaling and extending Moore's law.

Direct Optoelectronic Imaging of 2D Semiconductor-3D Metal Buried Interfaces

The semiconductor-metal junction is one of the most critical factors for high-performance electronic devices. In two-dimensional (2D) semiconductor devices, minimizing the voltage drop at this junction is particularly challenging and important. Despite numerous studies concerning contact resistance in 2D semiconductors, the exact nature of the buried interface under a three-dimensional (3D) metal remains unclear. Herein, we report the direct measurement of electrical and optical responses of 2D semiconductor-metal buried interfaces using a recently developed metal-assisted transfer technique to expose the buried interface, which is then directly investigated using scanning probe techniques. We characterize the spatially varying electronic and optical properties of this buried interface with <20 nm resolution. To be specific, potential, conductance, and photoluminescence at the buried metal/MoS₂ interface are correlated as a function of a variety of metal deposition conditions as well as the type of metal contacts. We observe that direct evaporation of Au on MoS₂ induces a large strain of ∼5% in the MoS₂ which, coupled with charge transfer, leads to degenerate doping of the MoS₂ underneath the contact. These factors lead to improvement of contact resistance to record values of 138 kΩ μm, as measured using local conductance probes. This approach was adopted to characterize MoS₂-In/Au alloy interfaces, demonstrating contact resistance as low as 63 kΩ μm. Our results highlight that the MoS₂/metal interface is sensitive to device fabrication methods and provide a universal strategy to characterize buried contact interfaces involving 2D semiconductors.

Plasmonic Hybrids of MoS2 and 10-nm Nanogap Arrays for Photoluminescence Enhancement

Monolayer MoS₂ has attracted tremendous interest, in recent years, due to its novel physical properties and applications in optoelectronic and photonic devices. However, the nature of the atomic-thin thickness of monolayer MoS₂ limits its optical absorption and emission, thereby hindering its optoelectronic applications. Hybridizing MoS₂ by plasmonic nanostructures is a critical route to enhance its photoluminescence. In this work, the hybrid nanostructure has been proposed by transferring the monolayer MoS₂ onto the surface of 10-nm-wide gold nanogap arrays fabricated using the shadow deposition method. By taking advantage of the localized surface plasmon resonance arising in the nanogaps, a photoluminescence enhancement of ~20-fold was achieved through adjusting the length of nanogaps. Our results demonstrate the feasibility of a giant photoluminescence enhancement for this hybrid of MoS₂/10-nm nanogap arrays, promising its further applications in photodetectors, sensors, and emitters.

Uncovering the Effects of Metal Contacts on Monolayer MoS2

Metal contacts are a key limiter to the electronic performance of two-dimensional (2D) semiconductor devices. Here, we present a comprehensive study of contact interfaces between seven metals (Y, Sc, Ag, Al, Ti, Au, Ni, with work functions from 3.1 to 5.2 eV) and monolayer MoS₂ grown by chemical vapor deposition. We evaporate thin metal films onto MoS₂ and study the interfaces by Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, and electrical characterization. We uncover that (1) ultrathin oxidized Al dopes MoS₂ n-type (>2 × 10¹² cm^-2) without degrading its mobility, (2) Ag, Au, and Ni deposition causes varying levels of damage to MoS₂ (e.g. broadening Raman E' peak from <3 to >6 cm^-1), and (3) Ti, Sc, and Y react with MoS₂. Reactive metals must be avoided in contacts to monolayer MoS₂, but control studies reveal the reaction is mostly limited to the top layer of multilayer films. Finally, we find that (4) thin metals do not significantly strain MoS₂, as confirmed by X-ray diffraction. These are important findings for metal contacts to MoS₂ and broadly applicable to many other 2D semiconductors.

Evolution of local strain in Ag-deposited monolayer MoS2 modulated by interface interactions

Strain is usually unavoidable in the fabrication of devices based on two-dimensional (2D) transition metal chalcogenides (TMDCs). When metals are deposited onto monolayer TMDCs, strain can be induced at metal-TMDC interfaces and evolves with elapsed time. However, the effect of the substrate on the strain evolution at the metal-TMDC interfaces is still unclear, which hinders the development of reliable 2D TMDC-based devices with perfect contacts. In this work, we investigated the evolution of metal-induced local strains for Ag-deposited monolayer MoS2 on three kinds of substrates with different interface interactions, i.e., sapphire, SiO2/Si, and mica. The interface interaction between MoS2 and sapphire is the strongest, while that between MoS2 and mica is the weakest. With the splitting of MoS2 Raman peaks as an indicator of local strain, the evolution behavior of the local strain at the Ag-MoS2 interfaces is found to greatly depend on the interface interactions from the underlying substrates. With elapsed time, the local strain is best preserved on sapphire but relaxed most easily on mica. Density-functional theory calculations show that the adsorption energies at the interfaces are different for MoS2 on different substrates, suggesting that the interface interaction between monolayer MoS2 and the substrates is crucial for the strain evolution. Our work is of benefit for the study of stability and reliability of devices based on TMDCs, particularly for flexible electronic devices.