Scanning tunneling spectroscopy

About: Scanning tunneling spectroscopy is a research topic. Over the lifetime, 7886 publications have been published within this topic receiving 213828 citations.

Electronic band gaps and exciton binding energies in monolayer M o x W 1 − x S 2 transition metal dichalcogenide alloys probed by scanning tunneling and optical spectroscopy

Abstract: Using optical absorption and scanning tunneling spectroscopy techniques, the authors investigate band-gap properties of single layers of transition metal dichalcogenide (TMDC) alloyed crystals (Mo${}_{x}$W${}_{1-x}$S${}_{2}$). They observe a significant modulation of the excitonic transitions, quasiparticle band gaps, and exciton binding energies. These findings may hold promise for fundamental studies of intralayer phenomena and for potential applications of TMDC alloys in electronic and optoelectronic devices.

Electronic and Mechanical Properties of Graphene–Germanium Interfaces Grown by Chemical Vapor Deposition

Abstract: Epitaxially oriented wafer-scale graphene grown directly on semiconducting Ge substrates is of high interest for both fundamental science and electronic device applications. To date, however, this material system remains relatively unexplored structurally and electronically, particularly at the atomic scale. To further understand the nature of the interface between graphene and Ge, we utilize ultrahigh vacuum scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) along with Raman and X-ray photoelectron spectroscopy to probe interfacial atomic structure and chemistry. STS reveals significant differences in electronic interactions between graphene and Ge(110)/Ge(111), which is consistent with a model of stronger interaction on Ge(110) leading to epitaxial growth. Raman spectra indicate that the graphene is considerably strained after growth, with more point-to-point variation on Ge(111). Furthermore, this native strain influences the atomic structure of the interface by inducing meta...

Observation of Mott localization gap using low temperature scanning tunneling spectroscopy in commensurate 1T-TaS2.

Abstract: The site-specified tunneling spectroscopy on $1T\ensuremath{-}\mathrm{T}\mathrm{a}{\mathrm{Sa}}_{2}$ at 77 K and room temperature indicated a wide opening of energy gap at the Fermi level at 77 K. The gap at the Fermi level was attributed to the Mott localization in the commensurate charge density wave (CDW) phase. The determined gap size on both sides of the Fermi level was about 400-500 mV at 77 K. A significant charge transfer was observed from CDW trough to crest. This charge transfer was derived from the electron localization on the CDW crest induced by Mott localization.

Tunneling rates in electron transport through double-barrier molecular junctions in a scanning tunneling microscope

Abstract: The scanning tunneling microscope enables atomic-scale measurements of electron transport through individual molecules. Copper phthalocyanine and magnesium porphine molecules adsorbed on a thin oxide film grown on the NiAl(110) surface were probed. The single-molecule junctions contained two tunneling barriers, vacuum gap, and oxide film. Differential conductance spectroscopy shows that electron transport occurs via vibronic states of the molecules. The intensity of spectral peaks corresponding to the individual vibronic states depends on the relative electron tunneling rates through the two barriers of the junction, as found by varying the vacuum gap tunneling rate by changing the height of the scanning tunneling microscope tip above the molecule. A simple, sequential tunneling model explains the observed trends.

Flat bands in twisted bilayer transition metal dichalcogenides

Abstract: The crystal structure of a material creates a periodic potential that electrons move through giving rise to the electronic band structure of the material. When two-dimensional materials are stacked, the twist angle between the layers becomes an additional degree freedom for the resulting heterostructure. As this angle changes, the electronic band structure is modified leading to the possibility of flat bands with localized states and enhanced electronic correlations. In transition metal dichalcogenides, flat bands have been theoretically predicted to occur for long moire wavelengths over a range of twist angles around 0 and 60 degrees giving much wider versatility than magic angle twisted bilayer graphene. Here we show the existence of a flat band in the electronic structure of 3° and 57.5° twisted bilayer WSe2 samples using scanning tunneling spectroscopy. Direct spatial mapping of wavefunctions at the flat band energy have shown that the flat bands are localized differently for 3° and 57.5°, in excellent agreement with first-principle density functional theory calculations.