Despite noteworthy progress in the fabrication of large-area graphene sheetlike nanomaterials, the vapor-based processing still requires sophisticated equipment and a multistage handling of the material. An alternative approach to manufacturing functional graphene-based films includes the employment of graphene oxide (GO) micrometer-scale sheets as precursors. However, search for a scalable manufacturing technique for the production of high-quality GO nanoscale films with high uniformity and high electrical conductivity is still continuing. Here we show that conventional dip-coating technique can offer fabrication of high quality mono- and bilayered films made of GO sheets. The method is based on our recent discovery that encapsulating individual GO sheets in a nanometer thick molecular brush copolymer layer allows for the nearly perfect formation of the GO layers via dip coating from water. By thermal reduction the bilayers (cemented by a carbon-forming polymer linker) are converted into highly conductive and transparent reduced GO films with a high conductivity up to 10 S/cm and optical transparency on the level of 90%. The value is the highest electrical conductivity reported for thermally reduced nanoscale GO films and is close to the conductivity of indium tin oxide currently in use for transparent electronic devices, thus making these layers intriguing candidates for replacement of ITO films.

We describe measurements aimed at tracking the subsurface energy deposition of ionic radiation by encapsulating an irradiated oxide target within multiple, spatially separated metal-oxide-semiconductor (MOS) capacitors. In particular, we look at incident kinetic energy and potential energy effects in the low keV regime for alkali ions (Na 1 ) and multicharged ions (MCIs) of Ar Q1 (Q 5 1, 4, 8, and 11) incident on the as-grown layers of SiO 2 on Si. With the irradiated oxide encapsulated under Al top contacts, we record an electronic signature of the incident ionic radiation through capacitance-voltage (C-V) measurements. Both kinetic and potential energy depositions give rise to shifted C-V signatures that can be directly related to internal electron-hole pair excitations. The MCI data reveal an apparent power law dependence on charge state, which is at odds with some prior thin foil studies obtained at higher incident energies.

A new electron beam ion trap (EBIT) based ion source and beamline were recently commissioned at Clemson University to produce decelerated beams of multi-to highly-charged ions for surface and materials physics research. This user facility is the first installation of a DREEBIT-designed superconducting trap and ion source (EBIS-SC) in the U.S. and includes custom-designed target preparation and irradiation setups. An overview of the source, beamline, and other facilities as well as results from first measurements on irradiated targets are discussed here. Results include extracted charge state distributions and first data on a series of irradiated metal-oxide-semiconductor (MOS) device targets. For the MOS devices, we show that voltage-dependent capacitance can serve as a record of the electronic component of ion stopping power for an irradiated, encapsulated oxide target.

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Measurements were performed to characterize and better understand the effects of slow highly charged ion (HCI) irradiation, a relatively unexplored form of radiation, on metal oxide semiconductor (MOS) devices. Si samples with 50 nm SiO 2 layers were irradiated with ion beams of Ar Q+ (Q = 4, 8, and 11) at normal incidence. The effects of the irradiation were encapsulated with an array of Al contacts forming the MOS structure. High frequency capacitance-voltage (CV) measurements reveal that the HCI irradiation results in stretchout and shifting of the CV curve. These changes in the CV curve are attributed to dangling Si bond defects at the Si/SiO 2 interface and trapped positive charge in the oxide, respectively. Charge state dependencies have been observed for these effects with the CV curve stretchout having a dependence of Q ∼1.7 and the CV curve shifting with a dependence of Q ∼1.8 . These dependencies are similar to the results of previous studies focused on the Q-dependence of the stopping power of HCIs. Published by the AVS.

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Hot electron generation was measured under the impact of energetic Ar and Rb ions on Ag thin film Schottky diodes. The energy-and angular-dependence of the current measured at the backside of the device due to ion bombardment at the frontside is reported. A sharp upturn in the energy dependent yield is consistent with a kinetic emission model for electronic excitations utilizing the device Schottky barrier as determined from current-voltage characteristics. Backside currents measured for ion incident angles of 630 are strongly peaked about 0 (normal incidence) and resemble results seen in other contexts, e.g., ballistic electron emission microscopy. Accounting for the increased transport distance for excited charges at non-normal incidence, the angular results are consistent with the accepted mean free path for electrons in Ag films. V