Large single-crystal graphene is highly desired and important for the applications of graphene in electronics, as grain boundaries between graphene grains markedly degrade its quality and properties. Here we report the growth of millimetre-sized hexagonal single-crystal graphene and graphene films joined from such grains on Pt by ambient-pressure chemical vapour deposition. We report a bubbling method to transfer these single graphene grains and graphene films to arbitrary substrate, which is nondestructive not only to graphene, but also to the Pt substrates. The Pt substrates can be repeatedly used for graphene growth. The graphene shows high crystal quality with the reported lowest wrinkle height of 0.8 nm and a carrier mobility of greater than 7,100 cm2 V−1 s−1 under ambient conditions. The repeatable growth of graphene with large single-crystal grains on Pt and its nondestructive transfer may enable various applications.

Although transition metal dichalcogenides such as MoS2 have been recognized as highly potent two-dimensional nanomaterials, general methods to chemically functionalize them are scarce. Herein, we demonstrate a functionalization route that results in organic groups bonded to the MoS2 surface via covalent C-S bonds. This is based on lithium intercalation, chemical exfoliation and subsequent quenching of the negative charges residing on the MoS2 by electrophiles such as diazonium salts. Typical degrees of functionalization are 10-20 atom % and are potentially tunable by the choice of intercalation conditions. Significantly, no further defects are introduced, and annealing at 350 °C restores the pristine 2H-MoS2. We show that, unlike both chemically exfoliated and pristine MoS2, the functionalized MoS2 is very well dispersible in anisole, confirming a significant modification of the surface properties by functionalization. DFT calculations show that the grafting of the functional group to the sulfur atoms of (charged) MoS2 is energetically favorable and that S-C bonds are formed.

A Raman spectroscopic investigation of graphite oxide derived graphene AIP Advances 2, 032183 (2012) Nanofracture in graphene under complex mechanical stresses Appl. Phys. Lett. 101, 121915 (2012) Low-energy electron transmission imaging of clusters on free-standing graphene Appl. Phys. Lett. 101, 113117 (2012) Highly tunable spin-dependent electron transport through carbon atomic chains connecting two zigzag graphene nanoribbons J. Chem. Phys. 137, 104107 (2012) Formation and control of wrinkles in graphene by the wedging transfer method

Hall elements are by far the most widely used magnetic sensor. In general, the higher the mobility and the thinner the active region of the semiconductor used, the better the Hall device. While most common magnetic field sensors are Si-based Hall sensors, devices made from III-V compounds tend to favor over that based on Si. However these devices are more expensive and difficult to manufacture than Si, and hard to be integrated with signal-processing circuits for extending function and enforcing performance. In this article we show that graphene is intrinsically an ideal material for Hall elements which may harness the remarkable properties of graphene, i.e. extremely high carrier mobility and atomically thin active body, to create ideal magnetic sensors with high sensitivity, excellent linearity and remarkable thermal stability.

Top-gate HfS2 field-effect transistors (FETs) with 5 nm HfO2 as dielectrics are successfully demonstrated, with on/off ratio of 10(5) and subthreshold swing of 95 mV dec(-1) . Moreover, due to the self-functionalization of HfS2 , uniform and ultrathin HfO2 film free of pinhole-like defects could be deposited on HfS2 , which is dramatically different from other transition metal dichalcogenide FETs.

The excellent electronic and mechanical properties of graphene provide a perfect basis for high performance flexible electronic and sensor devices. Here, we present the fabrication and

We detail a facile fabrication and testing method of functionalizing single-layer graphenes (SLGs) by photoactive TiO 2 thin films as test-beds for building efficient multifunctional optoelectronic devices. Interestingly, tuning the photoactivity of TiO 2 enables us to realize fast and significant photoswitching effects in TiO 2 -graphene devices. More importantly, using the hybrid devices as solid-state gas sensors, we have demonstrated a reversible and linear electrical sensitivity towards oxygen gas in the full concentration range (5-100%) at room temperature and ambient pressure, with a calculated minimum detection limit (MDL) of 0.01% oxygen. The unique oxygen sensitivity of the devices is attributed to the synergetic effect of the photoactivity of TiO 2 and the environmental ultrasensitivity of SLGs. These results form the basis for new types of future ultrasensitive multifunctional integrated devices for a variety of possible detection and/or sensing applications.

Vertical metal-insulator-graphene (MIG) diodes for radio frequency (RF) power detection are realized using a scalable approach based on graphene grown by chemical vapor deposition and TiO as barrier material. The temperature dependent current flow through the diode can be described by thermionic emission theory taking into account a bias induced barrier lowering at the graphene TiO interface. The diodes show excellent figures of merit for static operation, including high on-current density of up to 28 A cm, high asymmetry of up to 520, strong maximum nonlinearity of up to 15, and large maximum responsivity of up to 26 V, outperforming state-of-the-art metal-insulator-metal and MIG diodes. RF power detection based on MIG diodes is demonstrated, showing a responsivity of 2.8 V W at 2.4 GHz and 1.1 V W at 49.4 GHz.