Band gap opening and engineering is one of the high priority goals in the development of graphene electronics. Here, we report on the opening and scaling of band gap in BN doped graphene (BNG) films grown by low-pressure chemical vapor deposition method. High resolution transmission electron microscopy is employed to resolve the graphene and h-BN domain formation in great detail. X-ray photoelectron, micro-Raman, and UV-vis spectroscopy studies revealed a distinct structural and phase evolution in BNG films at low BN concentration. Synchrotron radiation based XAS-XES measurements concluded a gap opening in BNG films, which is also confirmed by field effect transistor measurements. For the first time, a significant band gap as high as 600 meV is observed for low BN concentrations and is attributed to the opening of the π-π* band gap of graphene due to isoelectronic BN doping. As-grown films exhibit structural evolution from homogeneously dispersed small BN clusters to large sized BN domains with embedded diminutive graphene domains. The evolution is described in terms of competitive growth among h-BN and graphene domains with increasing BN concentration. The present results pave way for the development of band gap engineered BN doped graphene-based devices.

Enhanced photoelectrochemical (PEC) performances of Ga(2)O(3) and GaN nanowires (NWs) grown in situ from GaN were demonstrated. The PEC conversion efficiencies of Ga(2)O(3) and GaN NWs have been shown to be 0.906% and 1.09% respectively, in contrast to their 0.581% GaN thin film counterpart under similar experimental conditions. A low crystallinity buffer layer between the grown NWs and the substrate was found to be detrimental to the PEC performance, but the layer can be avoided at suitable growth conditions. A band bending at the surface of the GaN NWs generates an electric field that drives the photogenerated electrons and holes away from each other, preventing recombination, and was found to be responsible for the enhanced PEC performance. The enhanced PEC efficiency of the Ga(2)O(3) NWs is aided by the optical absorption through a defect band centered 3.3 eV above the valence band of Ga(2)O(3). These findings are believed to have opened up possibilities for enabling visible absorption, either by tailoring ion doping into wide bandgap Ga(2)O(3) NWs, or by incorporation of indium to form InGaN NWs.

A 3D trenched-structure metal-insulator-metal (MIM) nanocapacitor array with an ultrahigh equivalent planar capacitance (EPC) of ~300 μF cm(-2) is demonstrated. Zinc oxide (ZnO) and aluminum oxide (Al2O3) bilayer dielectric is deposited on 1 μm high biomimetic silicon nanotip (SiNT) substrate using the atomic layer deposition method. The large EPC is achieved by utilizing the large surface area of the densely packed SiNT (!5 × 10(10) cm(-2)) coated conformally with an ultrahigh dielectric constant of ZnO. The EPC value is 30 times higher than those previously reported in metal-insulator-metal or metal-insulator-semiconductor nanocapacitors using similar porosity dimensions of the support materials.

An intriguing system featuring a wide band gap silica nanowire (SiO x NW) that absorbs visible light (532 nm) via the surface plasmons (SPs) of embedded gold nanoparticles (Au NPs) is reported for sensing applications. We report SP resonanceenhanced molecular oxygen sensing by single Au-NPs@SiO x NWs under 532-nm illumination (visible light) at room temperature. Excellent selectivity of the Au-NPs@SiO x NWs to molecular oxygen in air has been demonstrated. Illumination improved the sensing properties in terms of response and fast recovery time, which can be attributed to the photogenerated hole-mediated oxygen desorption. A general strategy of light-modulated sensing, vis-à -vis dark, is demonstrated in a wide band gap single NW system that could potentially open up routes for biosensing, because silica and Au both lack biotoxicity. NPG Asia Materials (2013) 5, e49; doi:10.1038/am.2013.17; published online 24 May 2013 Keywords: gas sensor; nanowire; silica; surface plasmon INTRODUCTION Oxide-based semiconductor nanostructured materials have been widely investigated for chemical and biosensing applications because of their biocompatibility, relatively easy large-scale synthesis, superior thermal and chemical stabilities and high surface-to-volume ratios. 1,2 However, improving the sensing performance requires improved sensitivity, good selectivity or specificity, short rise and fall times of signals (high-speed response and recovery) and an easily attainable working temperature, ideally in the room-temperature range. Because of their large surface areas, nanostructures such as nanowires (NWs), 3 nanotubes, 4,5 nanorods 6 and nanoparticles (NPs) 7 offer large reaction cross sections for signal generation. To further enhance the sensing performance of these nanostructures, surface modification, [8][9][10] applications of high electrical bias 11 and high operational temperatures (T4100 1C) 12 have been used.Improving the sensing performance with light has also been demonstrated using ZnO-based nanostructures under UV illumination. 13 However, most of these approaches have required high operational temperatures, high biases and light outside the visible range (400-800 nm), which has somewhat limited their general applicability. We demonstrated how Au NPs embedded in single amorphous silica NW (Au-NPs@SiO x silica NW) can be used as an oxygen gas sensor by amperometric routes in this work. According to that study, the silica shell is amorphous, containing various defects within the NW, such as nonbridging oxygen atoms, dangling bonds,