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Abstract Piezoelectricity in low‐dimensional materials and metal–semiconductor junctions has attracted recent attention. Herein, a 2D in‐plane metal–semiconductor junction made of multilayer 2H and 1T′ phases of molybdenum(IV) telluride (MoTe2) is investigated. Strong piezoelectric response is observed using piezoresponse force microscopy at the 2H–1T′ junction, despite that the multilayers of each individual phase are weakly piezoelectric. The experimental results and density functional theory calculations suggest that the amplified piezoelectric response observed at the junction is due to the charge transfer across the semiconducting and metallic junctions resulting in the formation of dipoles and excess charge density, allowing the engineering of piezoelectric response in atomically thin materials.
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Phase‐Dependent Band Gap Engineering in Alloys of Metal‐Semiconductor Transition Metal Dichalcogenides
Abstract Bandgap engineering plays a critical role in optimizing the electrical, optical and (photo)‐electrochemical applications of semiconductors. Alloying has been a historically successful way of tuning bandgaps by making solid solutions of two isovalent semiconductors. In this work, a novel form of bandgap engineering involving alloying non‐isovalent cations in a 2D transition metal dichalcogenide (TMDC) is presented. By alloying semiconducting MoSe2with metallic NbSe2, two structural phases of Mo0.5Nb0.5Se2, the1Tand2Hphases, are produced each with emergent electronic structure. At room temperature, it is observed that the1Tand2Hphases are semiconducting and metallic, respectively. For the1Tstructure, scanning tunneling microscopy/spectroscopy (STM/STS) is used to measure band gaps in the range of 0.42–0.58 at 77 K. Electron diffraction patterns of the1Tstructure obtained at room temperature show the presence of a nearly commensurate charge density wave (NCCDW) phase with periodic lattice distortions that result in an uncommon 4 × 4 supercell, rotated approximately 4° from the lattice. Density‐functional‐theory calculations confirm that local distortions, such as those in a NCCDW, can open up a band gap in1T‐Mo0.5Nb0.5Se2, but not in the2Hphase. This work expands the boundaries of alloy‐based bandgap engineering by introducing a novel technique that facilitates CDW phases through alloying.
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- Award ID(s):
- 1729787
- PAR ID:
- 10380998
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Functional Materials
- Volume:
- 30
- Issue:
- 51
- ISSN:
- 1616-301X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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