arXiv subjects

Shaohua Xiang

Publications and source records attributed to Shaohua Xiang.

4 recordsLinked to original sources

arXiv2020

Morphology and magneto-transport in exfoliated graphene on ultrathin crystalline \b{eta}-Si3N4(0001)/Si(111)

We report the first experimental study of graphene transferred on \b{eta}-Si3N4(0001)/Si(111). Our work provides a comprehensive quantitative understanding of the physics of ultrathin Si3N4 as a gate dielectric for graphene-based devices. The Si3N4 film was grown on Si(111) under ultra-high vacuum (UHV) conditions and investigated by scanning tunneling microscopy (STM). Subsequently, a graphene flake was deposited on top of it by a polymer-based transfer technique, and a Hall bar device was fabricated from the graphene flake. STM was employed again to study the graphene flake under UHV conditions after device fabrication and showed that surface quality is preserved. Electrical transport measurements, carried out at low temperature in magnetic field, revealed back gate modulation of carrier type and density in the graphene channel and showed the occurrence of weak localization. Under these experimental conditions, no leakage current between back gate and graphene channel was detected.

cond-mat.mes-hall↗

arXiv2017

Perfecting the Growth and Transfer of Large Single-Crystal CVD Graphene: A Platform Material for Optoelectronic Applications

In this work we demonstrate the synthesis of millimetre-sized single-crystals of graphene, achievable in a commercially-available cold-wall CVD reactor, and several different approaches to transfer it from the growth substrate to a target substrate of choice. We confirm the high crystal quality of this material using various characterisation techniques, including optical and scanning electron microscopy as well as Raman spectroscopy. By performing field effect and quantum Hall effect measurements we demonstrate that the electronic properties of such single-crystals are comparable to those of ideal mechanically exfoliated flakes of graphene. Several applications of this high-quality material are also reviewed.

cond-mat.mtrl-sci↗

arXiv2016

Inter-Edge Backscattering in Buried Split-Gate-Defined Graphene Quantum Point Contacts

Quantum Hall effects offer a formidable playground for the investigation of quantum transport phenomena. Edge modes can be detected, branched, and mixed by designing a suitable potential landscape in a two-dimensional conducting system subject to a strong magnetic field. In the present work, we demonstrate a buried split-gate architecture and use it to control electron conduction in large-scale single-crystal monolayer graphene grown by chemical vapor deposition. The control of the edge trajectories is demonstrated by the observation of various fractional quantum resistances, as a result of a controllable inter-edge scattering. Experimental data are successfully modeled both numerically and within the Landauer-Buettiker formalism. Our architecture is particularly promising and unique in view of the investigation of quantum transport via scanning probe microscopy, since graphene constitutes the topmost layer of the device. For this reason, it can be approached and perturbed by a scanning probe down to the limit of mechanical contact.

cond-mat.mes-hall↗

arXiv2016

Low-temperature quantum transport in CVD-grown single crystal graphene

Chemical vapor deposition (CVD) has been proposed for large-scale graphene synthesis for practical applications. However, the inferior electronic properties of CVD graphene are one of the key problems to be solved. In this study, we present a detailed study on the electronic properties of high-quality single crystal monolayer graphene. The graphene is grown by CVD on copper using a cold-wall reactor and then transferred to Si/SiO2. Our low-temperature magneto-transport data demonstrate that the characteristics of the measured single-crystal CVD graphene samples are superior to those of polycrystalline graphene and have a quality which is comparable to that of exfoliated graphene on Si/SiO2. The Dirac point in our best samples is located at back-gate voltages of less than 10V, and their mobility can reach 11000 cm2/Vs. More than 12 flat and discernible half-integer quantum Hall plateaus have been observed in high magnetic field on both the electron and hole side of the Dirac point. At low magnetic field, the magnetoresistance shows a clear weak localization peak. Using the theory of McCann et al., we find that the inelastic scattering length is larger than 1 μm in these samples even at the charge neutrality point.

cond-mat.mes-hall↗