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.

Tunable quasiparticle band gap in few-layer GaSe/graphene van der Waals heterostructures

Abstract: Two-dimensional few-layered materials exhibit unique and exotic electronic properties when compared to their bulk counterparts. Here, the authors report the role of dimensionality on the electronic properties of a van der Waals GaSe/graphene heterostructure. The strong thickness dependence of the GaSe band gap is demonstrated experimentally using scanning tunneling spectroscopy. The GaSe band gap decreases as the number of layers increases due to quantum confinement effects. The particular GaSe `Mexican hat' band structure is further explored by angle-resolved photoemission spectroscopy and by theoretical calculations. Interestingly, an electron transfer from graphene to GaSe has also been detected. It results in $n$-type doped thin GaSe films, opposite to the $p$-type character GaSe bulk.

Single-electron tunneling in nanometer-scale double-barrier heterostructure devices.

Abstract: We report a systematic experimental study of charge transport in nanometer-scale double-barrier resonant-tunneling devices. Asymmetric heterostructure material was used so that one barrier is substantially less transparent than the other. Resonant tunneling through size-quantized well states and single-electron charging of the well are thus largely separated in the two bias polarities. When the emitter barrier is more transparent than the collector barrier, electrons accumulate in the well; incremental electron occupation of the well, starting from zero, is accompanied by Coulomb blockade, which leads to sharp steps of the tunneling current. The voltage extent of the steps is affected by the intrawell electron-electron interaction. When the emitter barrier is less transparent, the current reflects resonant tunneling of just one electron at a time through size-quantized well states; the current peaks and/or steps (depending on experimental parameters) appear in current-voltage characteristics. Experimental results on magnetic field and temperature dependence of the current-voltage curves are also reported. Good agreement is achieved in comparison of many features of the experimental data with simple theoretical models.

Surface Structure and Electronic Property of Reduced SrTiO3(100) Surface Observed by Scanning Tunneling Microscopy/Spectroscopy

Abstract: We have obtained the scanning tunneling microscopy (STM) images and scanning tunneling spectroscopy (STS) data with atomic-scale resolution for a SrTiO3(100) surface annealed in ultrahigh vacuum (UHV) at 1200°C. A √5×√5-R26.6° surface superstructure indicating oxygen vacancy ordering has been observed. The STS data provide evidence for a localized surface state arising from oxygen vacancies at 1.35 eV below the Fermi level. STM images of the √5×√5 structure correspond to the surface orbital of the ordered Ti-oxygen vacancy complex.

Germanene termination of Ge${_2}$Pt crystals on Ge(110)

Abstract: We have investigated the growth of Pt on Ge(110) using scanning tunneling microscopy and spectroscopy The deposition of several monolayers of Pt on Ge(110) followed by annealing at 1100 K results in the formation of three-dimensional metallic Pt-Ge nanocrystals The outermost layer of these crystals exhibits a honeycomb structure The honeycomb structure is composed of two hexagonal sub-lattices that are displaced vertically by 02 A with respect to each other The nearest-neighbor distance of the atoms in the honeycomb lattice is 25${\pm}$01 A, ie very close to the predicted nearest-neighbor distance in germanene (24 A) Scanning tunneling spectroscopy reveals that the atomic layer underneath the honeycomb layer is more metallic than the honeycomb layer itself These observations are in line with a model recently proposed for metal di-(silicides/)germanides: a hexagonal crystal with metal layers separated by semiconductor layers with a honeycomb lattice Based on our observations we propose that the outermost layer of the Ge2Pt nanocrystal is a germanene layer

Reversible Change of the Spin State in a Manganese Phthalocyanine by Coordination of CO Molecule

Abstract: We show that the magnetic state of individual manganese phthalocyanine (MnPc) molecules on a Bi(110) surface is modified when the $\mathrm{Mn}2+$ center coordinates to CO molecules adsorbed on top. Using scanning tunneling spectroscopy we identified this change in magnetic properties from the broadening of a Kondo-related zero-bias anomaly when the CO-MnPc complex is formed. The original magnetic state can be recovered by selective desorption of individual CO molecules. First principles calculations show that the CO molecule reduces the spin of the adsorbed MnPc from $S=1$ to $S=1/2$ and strongly modifies the respective screening channels, driving a transition from an underscreened Kondo state to a state of mixed valence.