<i>In Situ</i>
 Monitoring of the Thermal-Annealing Effect in a Monolayer of 
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Su, Liqin; Yu, Yifei; Cao, Linyou; Zhang, Yong

doi:10.1103/physrevapplied.7.034009

Cited by 29 publications

(19 citation statements)

References 42 publications

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“…The annealing process, as shown in the AFM images in Fig. 2d–f and supported by the literature 9 21 51 , removes residual PMMA and water while promoting surface adhesion. Therefore, the post annealing results allow us to separate out the effects from the transfer process and analyze the substrate effects on the flakes.…”

Section: Resultssupporting

confidence: 82%

“…In order to further study the surface interaction, the sample is finally annealed under Ar:H 2 (5:1) gas mixture at 300 °C for two hours. This annealing step has been shown to be crucial in removing excess PMMA and promote surface adhesion 9 21 51 . Specifically in the case of MoS 2 51 , annealing times in excess of 90 minutes are shown, via Raman and PL, to have increased the post transfer substrate bonding, creating an increased strain on the monolayer TMD.…”

Section: Resultsmentioning

confidence: 99%

“…For the out-of-plane A’ 1 peak position, which is most directly related to substrate interaction 13 14 21 41 51 , Fig. 5(a) , the peak positions post annealing show a large variation between substrates.…”

Section: Resultsmentioning

confidence: 99%

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Transfer of monolayer TMD WS2 and Raman study of substrate effects

Mlack

Das

Danda

et al. 2017

Sci Rep

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A facile transfer process for transition metal dichalcogenide WS2 flakes is reported and the effect of the underlying substrate on the flake properties is investigated using Raman spectroscopy. The flakes are transferred from their growth substrate using polymethyl methacrylate (PMMA) and a wet etch to allow the user to transfer the flakes to a final substrate using a microscope and micromanipulator combined with semi-transparent Kapton tape. The substrates used range from insulators such as industry standard high-k dielectric HfO2 and “green polymer” parylene-C, to conducting chemical vapor deposition (CVD) grown graphene. Raman spectroscopy is used first to confirm the material quality of the transferred flakes to the substrates and subsequently to analyze and separate the effects arising from material transfer from those arising from interactions with the substrate. We observe changes in the Raman spectra associated with the interactions between the substrates in the flakes. These interactions affect both in-plane and out-of-plane modes in different ways depending on their sources, for example strain or surface charge. These changes vary with final substrate, with the strongest effects being observed for WS2 transferred onto graphene and HfO2, demonstrating the importance of understanding substrate interaction for fabrication of future devices.

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Section: Resultssupporting

confidence: 82%

Section: Resultsmentioning

confidence: 99%

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Transfer of monolayer TMD WS2 and Raman study of substrate effects

Mlack

Das

Danda

et al. 2017

Sci Rep

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“…It has been documented that 2D films like monolayer MoS 2 and WS 2 usually form significant chemical bonding with the substrates on which they are grown. [29][30][31] Given the predicted weak but signifiant chemical bonding between graphene and silicene, [12,15] we expect that the thin diamond-like Si strcuture could experience some tensile epitaxial strain from the graphite substrate. [12,15] The strain could qualitatively explain the variation in redshift that is larger for the Based on the phonon frequency change between diamond F 2g mode (~1300 cm -1 ) and graphene E 2g mode (~1600 cm -1 ), one would expect that the silicene E 2g phonon frequency to be roughly in proportion higher than that of bulk Si at ~520 cm -1 .…”

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confidence: 99%

Growth of oxidation-resistive silicene-like thin flakes and Si nanostructures on graphene

Yue

Myers

et al. 2019

J. Semicond.

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We report the growth of Si nanostructures, either as thin films or nanoparticles, on graphene substrates. The Si nanostructures are shown to be single crystalline, air stable and oxidation resistive, as indicated by the observation of a single crystalline Si Raman mode at around 520 cm -1 , a STM image of an ordered surface structure under ambient condition, and a Schottky junction with graphite. Ultra-thin silicon regions exhibit silicene-like behavior, including a Raman mode at around 550 cm -1 , a triangular lattice structure in STM that has distinctly different lattice spacing from that of either graphene or thicker Si, and metallic conductivity of up to 500 times higher than that of graphite. This work suggests a bottom-up approach to forming a Si nanostructure array on a large scale patterned graphene substrate for fabricating nanoscale Si electronic devices. *

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“…TMD monolayers have unique optical and electrical properties including high absorption relative to their thickness 1 , direct band gaps 2 – 4 , rapid charge separation 5 , and can even be ferromagnetic 6 – 8 or superconducting 9 – 11 . Due to their thinness, monolayer TMDs interact strongly with their environment; this strong interaction makes characterization of trapped contaminants, surface adsorbed contaminants, water layers, and the TMD-substrate step height necessary to predict and understand device operation 12 – 16 . Dynamic atomic force microscopy (dAFM), in which a nanoscopic tip is driven sinusoidally, can measure topography while providing a plethora of additional data channels for characterizing the surface absorbed contaminants.…”

Section: Introductionmentioning

confidence: 99%

Reduction in Step Height Variation and Correcting Contrast Inversion in Dynamic AFM of WS2 Monolayers

Godin

Cupo

Yang

2017

Sci Rep

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A model has been developed to account for and prevent the anomalies encountered in topographic images of transition metal dichalcogenide monolayers using dynamic atomic force microscopy (dAFM). The height of WS2 monolayers measured using dAFM appeared to be increased or decreased, resulting from the interactions between the tip and the surface. The hydrophilic SiO2 substrate appeared higher than the weakly hydrophilic WS2 when the tip amplitude was low or at a high set point (high force). Large amplitudes and low set points corrected the step height inversion, but did not recover the true step height. Removing water from the sample resulted in an order of magnitude reduced variation in step height, but the WS2 appeared inverted except at low amplitudes and high set points. Our model explains the varying step heights in dAFM of TMDs as a result of varying tip-sample interactions between the sample and substrate, in the presence or absence of capillaries. To eliminate contrast inversion, high amplitudes can be used to reduce the effect of capillary forces. However, when capillaries are not present, low amplitudes and high set points produce images with proper contrast due to tool operation in the repulsive regime on both materials.

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In Situ Monitoring of the Thermal-Annealing Effect in a Monolayer of MoS2

Cited by 29 publications

References 42 publications

Transfer of monolayer TMD WS2 and Raman study of substrate effects

Transfer of monolayer TMD WS2 and Raman study of substrate effects

Growth of oxidation-resistive silicene-like thin flakes and Si nanostructures on graphene

Reduction in Step Height Variation and Correcting Contrast Inversion in Dynamic AFM of WS2 Monolayers

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