Formation of Coherent 1H–1T Heterostructures in Single-Layer MoS₂ on Au(111)

Abstract

Heterojunctions of semiconductors and metals are the fundamental building blocks of modern electronics. Coherent heterostructures between dissimilar materials can be achieved by composition, doping, or heteroepitaxy of chemically different elements. Here, we report the formation of coherent single-layer 1H−1T MoS 2 heterostructures by mechanical exfoliation on Au(111), which are chemically homogeneous with matched lattices but show electronically distinct semiconducting (1H phase) and metallic (1T phase) character, with the formation of these heterojunctions attributed to a combination of lattice strain and charge transfer. The exfoliation approach employed is free of tape residues usually found in many exfoliation methods and yields single-layer MoS 2 with millimeter (mm) size on the Au surface. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), scanning tunneling microscopy (STM), and scanning tunneling spectroscopy (STS) have collectively been employed to elucidate the structural and electronic properties of MoS 2 monolayers on Au substrates. Bubbles in the MoS 2 formed by the trapping of ambient adsorbates beneath the single layer during deposition, have also been observed and characterized. Our work here provides a basis to produce two-dimensional heterostructures which represent potential candidates for future electronic devices.

Interactions of Water with Pristine and Defective MoS2

“…When water is adsorbed in between layers of MoS 2 , it causes a disruption in the MoS 2 lattice, like a bubble in a decal. This has been observed experimentally for MoS 2 on Au substrates . To quantify the changes in the MoS 2 structure induced by adsorbates, we repeated the DFT calculations from Section with a structure consisting of 7 × 7 unit cells of MoS 2 to ensure that the edges of the simulation box are far enough away from the water to not be affected.…”

“…This has been observed experimentally for MoS 2 on Au substrates. 57 To quantify the changes in the MoS 2 structure induced by adsorbates, we repeated the DFT calculations from Section 3.2 with a structure consisting of 7 × 7 unit cells of MoS 2 to ensure that the edges of the simulation box are far enough away from the water to not be affected. Figure 7 shows the displacement in the Z direction (normal to the lamella) of the Mo atoms in the layer directly above the adsorbed water molecule and the defect site.…”

Controlled Doping Engineering in 2D MoS2 Crystals toward Performance Augmentation of Optoelectronic Devices

“…MoS 2 and SnS 2 possess a similar formula MX 2 , consisting of a transition-metal layer sandwiched between two layers of chalcogen S atoms. Yet, the Mo–S length (2.41 Å) is shorter than the Sn–S length (2.59 Å). , The substitution of Sn atoms into the MoS 2 lattice generates additional strain in the host lattice, thereby contributing to the change in Raman peaks versus doping concentrations (Figure b). , Simultaneously, the Raman intensity is reduced, with a smaller I (E 2g 1 )/ I (A 1g ) value of Sn-doped flakes than that of pristine MoS 2 flakes, as shown in Figure c, since the matrix elements and selection rules for Raman-active vibrational modes are principally determined by the lattice symmetry . The sample domain (Figure d) revealed uniform MoS 2 via the Raman intensity mapping of A 1g (Mo–S) (Figure e).…”

Fast and efficient electrochemical thinning of ultra-large supported and free-standing MoS2 layers on gold surfaces

“…5a, as reported. 31,48 The resulting Mo and S peaks are characteristic of MoS 2 at the 2H phase with minimal oxidation, less than 2% for Mo 6+ . Fig.…”