Xiaoyue He

Fabrication and ethanol sensing characteristics of ZnO nanowire gas sensors

Based on the achievement of synthesis of ZnO nanowires in mass production, ZnO nanowires gas sensors were fabricated with microelectromechanical system technology and ethanol-sensing characteristics were investigated. The sensor exhibited high sensitivity and fast response to ethanol gas at a work temperature of 300 °C. Our results demonstrate the potential application of ZnO nanowires for fabricating highly sensitive gas sensors.

Evidence of Silicene in Honeycomb Structures of Silicon on Ag(111)

In the search for evidence of silicene, a two-dimensional honeycomb lattice of silicon, it is important to obtain a complete picture for the evolution of Si structures on Ag(111), which is believed to be the most suitable substrate for growth of silicene so far. In this work we report the finding and evolution of several monolayer superstructures of silicon on Ag(111), depending on the coverage and temperature. Combined with first-principles calculations, the detailed structures of these phases have been illuminated. These structures were found to share common building blocks of silicon rings, and they evolve from a fragment of silicene to a complete monolayer silicene and multilayer silicene. Our results elucidate how silicene forms on Ag(111) surface and provides methods to synthesize high-quality and large-scale silicene.

Evidence for Dirac Fermions in a Honeycomb Lattice Based on Silicon

Silicene, a sheet of silicon atoms in a honeycomb lattice, was proposed to be a new Dirac-type electron system similar to graphene. We performed scanning tunneling microscopy and spectroscopy studies on the atomic and electronic properties of silicene on Ag(111). An unexpected √3 × √3 reconstruction was found, which is explained by an extra-buckling model. Pronounced quasiparticle interferences (QPI) patterns, originating from both the intervalley and intravalley scatter, were observed. From the QPI patterns we derived a linear energy-momentum dispersion and a large Fermi velocity, which prove the existence of Dirac fermions in silicene.

Positive temperature coefficient resistance and humidity sensing properties of Cd-doped ZnO nanowires

Cd-doped ZnO nanowires in mass production were synthesized by evaporating metal zinc (Zn) and cadmium (Cd) at 900 °C. Devices using the synthesized nanowires were fabricated on microstructured substrates. Cd-doped ZnO nanowires show a clear positive temperature coefficient of resistance effect, which is quite abnormal as compared to pure ZnO nanowires. At room temperature, resistance change of more than three orders of magnitude was measured when Cd-doped ZnO nanowire device was exposed to a moisture pulse of 95% relative humidity.

Highly tunable electron transport in epitaxial topological insulator (Bi1-xSbx)2Te3 thin films

Atomically smooth, single crystalline (Bi1−xSbx)2Te3 films have been grown on SrTiO3(111) substrates by molecular beam epitaxy. A full range of Sb-Bi compositions have been studied in order to obtain the lowest possible bulk conductivity. For the samples with optimized Sb compositions (x=0.5±0.1), the carrier type can be tuned from n-type to p-type across the whole thickness with the help of a back-gate. Linear magnetoresistance has been observed at gate voltages close to the maximum in the longitudinal resistance of a (Bi0.5Sb0.5)2Te3 sample. These highly tunable (Bi1−xSbx)2Te3 thin films provide an excellent platform to explore the intrinsic transport properties of the three-dimensional topological insulators.

Chemical potential fluctuations in topological insulator (Bi0.5Sb0.5)2Te3-films visualized by photocurrent spectroscopy

We investigate the photocurrent properties of the topological insulator (Bi

Substitution-induced spin-splitted surface states in topological insulator (Bi1-xSbx)2Te3

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Tuning the surface plasmon on Ag(111) by organic molecules

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Growth of Topological Insulator Bi2Se3 Thin Films on SrTiO3 with Large Tunability in Chemical Potential

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