Thermal Degradation of Monolayer MoS₂ on SrTiO₃ Supports

Abstract

is a wide-bandgap semiconductor suitable for use in high-temperature electronics. It is therefore important to understand its thermal stability. We report the results of a study on thermal degradation of MoS 2 monolayers supported on SrTiO 3 substrates in ultrahigh vacuum (UHV). Our studies were carried out on the (111), (110), and (001) terminations of SrTiO 3 substrates, but MoS 2 was found to degrade on all of these surfaces in a similar way. By scanning tunneling microscopy, we show that MoS 2 monolayer crystals maintain their structure up to 700 °C under UHV, at which point triangular etch trenches appear along the ⟨21̅ 1̅ 0⟩ lattice directions (i.e., sulfur-terminated edge directions) of the MoS 2 crystals. The trenches are due to the preferential loss of sulfur, allowing molybdenum to be oxidized by oxygen originating from the SrTiO 3 substrate. The intensity of the A-exciton photoluminescence (PL) peak and the E 2g 1 and A 1g Raman signals reduced significantly following treatment at this temperature. The crystals continue to degrade at higher annealing temperatures in UHV until they transform into MoO x (x = 2−3) particles at 900 °C, and the optical properties characteristic of MoS 2 are lost entirely in PL and Raman spectra. The initial sulfur loss and the formation of MoO x are confirmed by X-ray photoelectron spectroscopy. The macroscopic triangular shapes of the MoS 2 crystals are retained until the residual particles evaporate at above 1000 °C. The optical properties of the 700 and 800 °C UHV-annealed samples can be partially recovered upon sulfur annealing. This work establishes a pathway of the thermal degradation of SrTiO 3 -supported monolayer MoS 2 in vacuum from smooth MoS 2 crystals to crystals with sulfur vacancies (etch trenches), followed by MoO 2 and finally MoO 3 particles. We also demonstrate how sulfur annealing can be used to heal the defects.

Single-Step Chemical Vapor Deposition Growth of Platinum Nanocrystal: Monolayer MoS2 Dendrite Hybrid Materials for Efficient Electrocatalysis

“…72 Lower temperature cannot guarantee the sufficient adhesion enhancement (Figure 6d), and further increasing the temperature above 600 ℃ would cause the decomposition of MoS2. 41 The improved long-term stability (~12 h) is validated by chronoamperometry (Figure 6e) and SEM imaging (Figure 6g). 42 We have not seen changes in the XPS spectra before and after annealing, which means that the chemisorption between Pt and MoS2 is unaffected during this treatment.…”

“…The peak position values are displayed in Table S1, echoing the reported data. 32,40,41 The Mo 6+ ionization state is ascribed to the MoO3 precursor that has not been sulfurized during the APCVD or local oxidized regions of the sample after exposure to air. The Mo 3d peaks of Pt:MoS2 dendrite are downshifted by 0.3 eV relative to those of pristine MoS2 (Figure 3b), indicating that the Mo atoms gain electrons as a consequence of the Pt incorporation.…”

Mixed-dimensional InAs nanowire on layered molybdenum disulfide heterostructures via selective-area van der Waals epitaxy

“…The presence of these particles are reported in various studies and is likely to be unreacted MoO 3 . 16,42 The results of optimizing the growth parameter space and the inuence of the PLL surface treatment are used for integration of a single InAs NW on individual, isolated, triangular MoS 2 domains. To this end, samples with and without the PLL treatment are loaded for growth under the previously determined optimal SA-vdWE conditions (i.e., V/III ¼ 25, c TMIn ¼ 8 mmol min À1 , and T G ¼ 750 C).…”

Perovskites based Nano Heterojunctions for Photocatalytic Pollutant Removal

“…Thickness of single crystal BaTiO3 is 0.25-1 mm which transmits from 0.5 μ to 6 μ. Higher adsorption was found for wavelength greater than 11 μ and weak adsorption at 8 μ. Noland studied that the single crystal strontium titanate show optical properties produced by a flame fusion [44]. Between 0.20 μ to 17 μ in wavelength the optical coefficient was measured.…”