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We demonstrated the fabrication of graphene nanoribbons (GNRs) as narrow as 35 nm created using scanning probe lithography to deposit a polymer mask1–3and then fluorinating the sample to isolate the masked graphene from the surrounding wide band gap fluorographene. The polymer protected the GNR from atmospheric adsorbates while the adjacent fluorographene stably p-doped the GNRs which had electron mobilities of ∼2700 cm2/(V·s). Chemical isolation of the GNR enabled resetting the device to nearly pristine graphene. [ABSTRACT FROM AUTHOR]

We report a process to form large-area, few-monolayer graphene oxide films and then recover the outstanding mechanical properties found in graphene to fabricate high Young’s modulus (< E>= 185 GPa), low-density nanomechanical resonators. Wafer-scale films as thin as 4 nm are sufficiently robust that they can be delaminated intact and resuspended on a bed of pillars or field of holes. From these films, we demonstrate radio frequency resonators with quality factors (up to 4000) and figures of merit ( f× Q> 10 11) well exceeding those of pure graphene resonators reported to date. These films’ ability to withstand high in-plane tension (up to 5 N/m) as well as their high Q-values reveals that film integrity is enhanced by platelet-platelet bonding unavailable in pure graphite. [ABSTRACT FROM AUTHOR]

We demonstrate reduced graphene oxide as the active material for high-performance molecular sensors. Sensors are fabricated from exfoliated graphene oxide platelets that are deposited to form an ultrathin continuous network. These graphene oxide networks are tunably reduced toward graphene by varying the exposure time to a hydrazine hydrate vapor. The conductance change of the networks upon exposure to trace levels of vapor is measured as a function of the chemical reduction. The level of reduction affects both the sensitivity and the level of 1/ fnoise. The sensors are capable of detecting 10 s exposures to simulants of the three main classes of chemical-warfare agents and an explosive at parts-per-billion concentrations. [ABSTRACT FROM AUTHOR]

The heteroepitaxial growth of Ge on Au-patterned Si(001) is investigated using in situ spectromicroscopy. Patterning of a hydrogen-terminated Si surface with a square array of Au dots followed by brief exposure to air leads to the spontaneous, local oxidation of Si. The resulting oxide nanopattern limits the surface migration of Au during annealing up to 600 °C, resulting in complete preservation of the Au pattern. Subsequent deposition of Ge induces a redistribution of Au across the surface even as the oxide nanopattern persists. As a result, the oxide pattern drives the growth of Ge islands into an ordered assembly, while Au decorates the surfaces of the Ge islands and modifies their shape. [ABSTRACT FROM AUTHOR]

The evolution of crystallographic facets of strained heteroepitaxial Ge islands on Si is investigated. Islands growing on Si(001), (111), (110) and (113) are bound by an equilibrium set of facets that includes only shared stable surfaces between bulk Si and Ge--{105}, {113}, {15 3 23} and {111}. The formation of a stereographic map from these indices facilitates the prediction of Ge faceted-island shapes on any Si substrate at different stages of growth. The analysis presented here can be applied to other heteroepitaxial islanding systems where a finite set of shared equilibrium facets exists for the bulk starting materials. [ABSTRACT FROM AUTHOR]

We present the first nanomechanical resonators microfabricated in single-crystal diamond. Shell-type resonators only 70 nm thick, the thinnest single crystal diamond structures produced to date, demonstrate a high-quality factor (Q≈ 1000 at room temperature, Q≈ 20 000 at 10 K) at radio frequencies (50–600 MHz). Quality factor dependence on temperature and frequency suggests an extrinsic origin to the dominant dissipation mechanism and methods to further enhance resonator performance. [ABSTRACT FROM AUTHOR]

Many applications of graphene can benefit from the enhanced mechanical robustness of graphene-based components. We report how the stiffness of vertical graphene (VG) sheets is affected by the introduction of defects and fluorination, both separately and combined. The defects were created using a high-energy ion beam while fluorination was performed in a XeF2 etching system. After ion bombardment alone, the average effective reduced modulus (Er), equal to ∼4.9 MPa for the as-grown VG sheets, approximately doubled to ∼10.0 MPa, while fluorination alone almost quadrupled it to ∼18.4 MPa. The maximum average Er of ∼32.4 MPa was achieved by repeatedly applying fluorination and ion bombardment. This increase can be explained by the formation of covalent bonds between the VG sheets due to ion bombardment, as well as the conversion from sp2 to sp3 and increased corrugation due to fluorination. [ABSTRACT FROM AUTHOR]