Sunday, March 29, 2020

One-dimensional electron transport and thermopower in an individual InSb nanowire

We have measured the electrical conductance and thermopower of a single InSb nanowire in the temperature range from 5 to 340 K. Below temperature (T) 220 K, the conductance (G) shows a power-law dependence on T and the current (I)–voltage (V) curve follows a power-law dependence on V at large bias voltages. These features are the characteristics of one-dimensional Luttinger liquid (LL) transport. The thermopower (S) also shows linear temperature dependence for T below 220 K, in agreement with the theoretical prediction based on the LL model. Above 220 K, the power law and linear behaviours respectively in the G–T and S–T curves persist but with different slopes from those at low temperatures. The slope changes can be explained by a transition from a single-mode LL state to a multi-mode LL state.

Source:IOPscience

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Tuesday, March 24, 2020

Lateral n–i–p junctions formed in an InSb quantum well by bevel etching

We have used a novel, simple technique based on bevel etching, to fabricate samples containing lateral n–i–p junctions in an InSb/InAlSb quantum well. The structure was designed by self-consistent solution of Schrödinger's and Poisson's equations, and grown by molecular beam epitaxy on a SI GaAs substrate. Current/voltage characteristics were measured as a function of temperature between 10 and 80 K, and rectifying characteristics were obtained over the whole temperature range.

Source:IOPscience

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Wednesday, March 18, 2020

Epitaxial growth and electronic properties of few-layer stanene on InSb (1 1 1)

Stanene has been theoretically predicted to be a 2D topological insulator with a large band gap, potentially hosting quantum spin Hall effect at room temperature. Here, few-layer stanene films have been epitaxially grown on Sb-terminated InSb (1 1 1) surface and their structural and electrical properties are characterized. Scanning tunneling spectrum results reveal a large bulk bandgap in single-layer stanene (over 0.2 eV). Moreover, spectroscopy evidence for a filled edge state near the steps was observed. The gap decreases dramatically with increasing number of layers, and multilayer stanene should become a Dirac semimetal in the bulk limit. The changeover may involve nontrivial topological phase transitions. Clear and reproducible Shubnikov–de Haas oscillations were observed on the single-layer stanene films that were exposed to atmospheric conditions for an extended period of time, showing the possibility for device experiments using nanofabrication and magneto-transport. Our results demonstrate that the single-layer stanene is a promising topological material for exploring fundamental physics and quantum applications.

Source:IOPscience

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Wednesday, March 11, 2020

Raman Spectroscopy of the Damages Induced by Ar-Ion Beam Etching of InSb(100) Surface

The strong enhancement of forbidden TO mode on Ar ion beam-etched InSb(100) surfaces was examined by Raman spectroscopy. By raising the applied RF power in Ar-ion etching from 50 to 200 W, the integrated area ratio of ITO/ILO increased from 0.05 to 0.23 and the full width at half maximum of LO peak increased from 5.46 to 7.46 cm−1. Such increases are induced by the partly disordered structure deformed by bombarded Ar ions. Raman spectroscopy could investigate the microscopic damages of the crystalline structure leading to break the Raman selection rules.

Source:IOPscience

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Thursday, March 5, 2020

Ion irradiation-induced polycrystalline InSb foam

InSb films with various thicknesses were deposited by magnetron sputtering on SiO2/Si substrates and subsequently irradiated with 17 MeV Au+7 ions. The structural and electronic changes induced by ion irradiation were investigated by synchrotron and laboratory based techniques. Ion irradiation of InSb transforms compact films (amorphous and polycrystalline) in open cell solid foams. The initial stages of porosity were investigated by transmission electron microscopy analysis and reveal the porous structure initiates as small spherical voids with approximately 3 nm in diameter. The evolution of porosity was investigated by scanning electron microscopy images, which show that film thickness increases up to 16 times with increasing irradiation fluence. Here we show that amorphous InSb films become polycrystalline foams upon irradiation with 17 MeV Au+7 ions at fluences above 1014 cm−2. The films attain a zincblende phase, with crystallites randomly oriented, similarly to the polycrystalline structure attained by thermal annealing of unirradiated films.

Source:IOPscience

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