Enhanced Field Emission of ZnO Nanowires

Abstract

sorbed Pd II . All potentials are reported versus SCE (saturated calomel electrode), although for the scanning tunneling microscopy (STM) experiments a platinum wire was used as a pseudo-reference electrode (E Pt = +0.55 ± 0.05 V vs. SCE). Details about the experimental setup for cyclic voltammetry and STM are described elsewhere [26]. After their preparation, the samples for the photoemission experiments were immediately stored under an argon atmosphere, reducing the exposure time to ambient conditions during their loading into the ultrahigh-vacuum system of the electron spectrometer to less than a minute.The photoelectron spectra were measured with a Fisons Escalab-210 system using monochromatic Al Ka radiation (1486.6 eV, spot size < 1 mm). All spectra were taken with an overall energy resolution (full width at half maximum) of 0.36 eV and an angular resolution of ± 12 to avoid photoelectron-diffraction effects. To calibrate the instrument, the Fermi edge of a gold reference sample was determined, defining the origin of the binding energy scale (E B = 0). It has to be emphasized that radiation damage to the SAM by the X-ray exposure could be avoided due to the small-spot X-ray source, allowing a certain sample position to be probed for times of less than 1 h, followed by moving to a new position. During that time, no measurable decreases in the corresponding core-level intensities, or changes in their line shapes, were detected.

Broadband ZnO Single-Nanowire Light-Emitting Diode

“…9 The ZnO nanowires used in this study were grown by vaporizing and condensing a mixture of ZnO and graphite powder on carbon cloth. 11,19,20 The resulting nanowires are n-type, similar to ZnO in bulk or thin films. [15][16][17] Our technique (Figure 1) relies on the use of poly(methyl methacrylate) (PMMA) 22 as a negative resist 12,13 and electrically insulating layer.…”

Carbon-assisted nucleation and vertical growth of high-quality ZnO nanowire arrays

“…Figure 3(d) and 3(e) reveal that ZnO crystals directly nucleate on the flat a-C film with their c-axis perpendicular to the surface of the a-C film. It is known that carbon materials such as amorphous carbon, 17 diamond, 18 graphite flakes, 19 carbon cloths, 20 and photoresists 21 can be used as preferential nucleation and growth sites for ZnO NWs. It has been suggested that the extracted Zn droplets from the reaction of ZnO/ZnO x gas with carbon materials can act as the catalysts for ZnO NW nucleation and growth on the surfaces of carbon materials.…”

“…We have not observed any catalysts at the tips of the ZnO NWs, suggesting a self-catalytic growth. The HRTEM image recorded along the zone axis [11][12][13][14][15][16][17][18][19][20] of a NW is shown in Figure 1(d). Obviously, these ZnO NWs were structurally uniform and no crystalline defects, such as dislocations and stacking faults were observed.…”

Field enhancement factor and field emission from a hemi-ellipsoidal metallic needle

“…Finally for the electrical field with the assumption (P − Q)/C * ≈ 0 formulas (33) and (34) are completely analogous to (9) and (10). Therefore for the force and emission current we may use the above derived formulas.…”

“…Recently, field emission from metals [7], metal oxides [8][9][10][11], metal carbides [12], and other elongated nanostructures have also been explored. It is now possible to control the diameter, height, radius of curvature of the tip, and basic form of emitters during growth.…”