Co-reporter:Weijie Sun, Yunlong Li, Yang Yang, Yunming Li, Changzhi Gu and Junjie Li
Journal of Materials Chemistry A 2014 vol. 2(Issue 13) pp:2417-2422
Publication Date(Web):08 Jan 2014
DOI:10.1039/C3TC32240H
The bottom-up growth method has been the main way to form various AlN nanostructures, but there still exists many problems in the lack of control and non-uniformity. Here, we adopt a firstly top-down plasma etching method to easily fabricate large-area AlN nanocone arrays on magnetron sputtered (002) AlN films, and the unique, pebble-like array morphologies of the AlN films surface greatly induce the whole selective plasma etching process without any masked process. The as-formed AlN nanocones not only keep the crystalline oriented (002) and microstructure of the original AlN film, but also have a good uniformity and controllability in the height and density, as well as the tip-size. These AlN nanocone arrays exhibited an intense broad ultraviolet emission, centered at 3.26 eV and excellent field emission properties, especially showing a tip-size dependent photoluminescence and field emission properties that were remarkably enhanced with decreasing the nanocone tip-size. Our results provide a promising route for the controllable fabrication of AlN nanostructures and practical application of AlN-based various nanodevices in optoelectronics and vacuum-nanoelectronics.
Co-reporter:Shibing Tian, Weijie Sun, Zhaosheng Hu, Baogang Quan, Xiaoxiang Xia, Yunlong Li, Dong Han, Junjie Li, and Changzhi Gu
Langmuir 2014 Volume 30(Issue 42) pp:12647-12653
Publication Date(Web):2017-2-22
DOI:10.1021/la5022643
Control of the wetting property of diamond surface has been a challenge because of its maximal hardness and good chemical inertness. In this work, the micro/nanoarray structures etched into diamond film surfaces by a maskless plasma method are shown to fix a surface’s wettability characteristics, and this means that the change in morphology is able to modulate the wettability of a diamond film from weakly hydrophilic to either superhydrophilic or superhydrophobic. It can be seen that the etched diamond surface with a mushroom-shaped array is superhydrophobic following the Cassie mode, whereas the etched surface with nanocone arrays is superhydrophilic in accordance with the hemiwicking mechnism. In addition, the difference in cone densities of superhydrophilic nanocone surfaces has a significant effect on water spreading, which is mainly derived from different driving forces. This low-cost and convenient means of altering the wetting properties of diamond surfaces can be further applied to underlying wetting phenomena and expand the applications of diamond in various fields.
Co-reporter:Qiang Wang, Jun Jie Li, and Chang Zhi Gu
The Journal of Physical Chemistry C 2012 Volume 116(Issue 32) pp:16864-16869
Publication Date(Web):July 24, 2012
DOI:10.1021/jp304193z
Water-modified ultraviolet (UV) light response of single anodic TiO2 nanotube (NT) is reported in this article. After keeping in deionized water at room temperature, the original smooth surface of amorphous TiO2 NTs is roughened and even changes into sponge-like structure by stacking of further oxidized and crystallized nanodots (NDs) through water-driven surface dissolution process. Two-dimensional variable range hopping (2D-VRH) model is recognized to interpret low-temperature electrical transport properties for the original NT, and the water-modified NT shows deviation from this mechanism owing to the additional electronic tunneling through the surface-crystallized NDs assemblies. The resistance in dark is increased about one order after water-modification due to surface carrier depletion by nanocontacts between crystalline NDs and the original amorphous core. The UV sensitivity S (IUV/Idark) of as-prepared single NT is ∼1.6, and response and recovery times are about 0.39 and 0.45 s, respectively. S is increased to ∼21.7 after surface water-modification, whereas response and recovery times are increased to 7.1 and 7.5 s, respectively. Surface water-modification will reduce the density of recombination centers and increase the trap state density of carriers in TiO2 NT due to surface charge-separation effect, both leading to the larger UV sensitivity and response time. Single anodic TiO2 NT shows no persistent photocurrent, and it can be applied as high-speed, high-sensitivity UV optoelectronic nanodevices.
Co-reporter:Shibing Tian, Yunlong Li, Xiaoxiang Xia, Changzhi Gu, Junjie Li
Physica E: Low-dimensional Systems and Nanostructures 2011 Volume 43(Issue 10) pp:1902-1905
Publication Date(Web):August 2011
DOI:10.1016/j.physe.2011.06.036
A fast reactive ion etching (RIE) treatment method is presented for dramatic enhancement of the field emission performances of nanocrystalline diamond (NCD) films. In this method a moment RIE treatment is able to modify the surface morphologies of NCD films and form a large area of nanoneedle-like arrays on the NCD films, in which the diamond nanoparticles were seeded on the film to serve as an etching mask. These elaborated diamond nanoneedle-like structures showed good uniformity and dense morphology with a controllable aspect ratio and distribution density and thereby significantly increased the electron field emission properties of the NCD films due to the formation of more emitting tips and enhanced field enhancement factor.Graphical abstractHighlights► Highly efficient field emission from nanodiamond films by fast RIE treatment process. ► Large area of diamond nanoneedle-like arrays was formed on the nanodiamond films by RIE process. ► Dispersed diamond nanoparticles were seeded on the nanodiamond film to serve as an etching mask. ► Enhanced field emission is due to more emitting tips and increased field enhancement factor.
Co-reporter:J.J. Li, C. Lu, X.X. Xia, C.Z. Gu
Applied Surface Science 2010 Volume 256(Issue 21) pp:6433-6436
Publication Date(Web):15 August 2010
DOI:10.1016/j.apsusc.2010.04.030
Abstract
Ferroelectric copolymer thin films P(VDF-TrFE) are used as a ferroelectric cathode for investigation of their electron emission properties. This ferroelectric copolymer films with different thicknesses are deposited by spin-coating method, and then the annealing process is carried out to improve the crystallinities of as-deposited copolymer films. The measurement results of ferroelectric electron emission showed that the copolymer P(VDF-TrFE) films had a desired ferroelectric electron emission ability excited at low-voltage pulse, and its peak emission current can reach to be ∼1.3 μA when the pulse voltage is 280 V. In addition, the effect of film thickness on electron emission property and emission stability of copolymer thin film P(VDF-TrFE) are discussed.
Co-reporter:Z.L. Wang, C. Lu, J.J. Li, C.Z. Gu
Applied Surface Science 2009 Volume 255(Issue 23) pp:9522-9525
Publication Date(Web):15 September 2009
DOI:10.1016/j.apsusc.2009.07.086
Heavily boron-doped diamond films are synthesized by the hot-filament chemical vapor deposition method under the gas mixtures of H2, CH4 and trimethyl borate. The measurement results of scanning electron microscopy, Raman spectroscopy, X-ray diffractometer and electrical properties showed the morphologies, microstructures, carrier concentration and superconducting transition temperature for as-grown diamond films were dependent on the change of growth pressure, and specially its carrier concentrations could be adjusted from 1019 to 1021 cm−3 by increasing growth pressures from 2.5 to 5 kPa. And further, the effects of growth pressure on the film microstructural property and the doping level dependence of the superconducting transition temperature were discussed.
Co-reporter:Y.L. Li, Z.L. Wang, Q. Wang, X.X. Xia, J.J. Li, C.Z. Gu
Vacuum 2009 Volume 83(Issue 8) pp:1118-1122
Publication Date(Web):1 May 2009
DOI:10.1016/j.vacuum.2009.02.006
The hydrogenation of Ib-type single crystalline diamond with grain size of several tens of micrometers, synthesized by high-pressure and high-temperature (HPHT) sintering, was carried out by hydrogen plasma treatment in a hot-filament chemical vapor deposition (HFCVD) system. After exposure to air, the surface conductivity of (001) and (111) facets of HPHT single crystalline diamond was measured. The influences of hydrogenation duration, temperature and gas pressure on the surface conductivity of (001) and (111) facets have been investigated. The measurement results show that the variation of hydrogenation conditions has a noticeable effect on the surface conductivity of single crystalline diamond, which is closely related to the formation of a chemical vapor deposition (CVD) regrowth layer on the facets induced by hydrogen plasma treatment process. In addition, (001) surface exhibits higher electrical conductivity than (111) surface, which is mainly attributed to less nitrogen concentration on the (001) surface than on the (111) surface.
Co-reporter:J.J. Li, Q. Wang, C.Z. Gu
Ultramicroscopy 2007 Volume 107(Issue 9) pp:861-864
Publication Date(Web):September 2007
DOI:10.1016/j.ultramic.2007.02.021
New forms of tubular carbon cone (TCC) were grown on gold wires by hot-filament chemical vapor deposition (HFCVD). They have a long-cone-shaped appearance with a herringbone hollow interior, surrounded by helical sheets of graphite that are coiled around it. It is considered that TCC formation results because the size of the catalyst particle located in the top of the TCC decreases continuously during growth, due to etching effects in the CVD plasma, reflecting competition between the growth and etching processes in the plasma. In addition, field emission measurements show that TCCs have a very low-threshold field of 0.27 V/μm, and that a stable macroscopic emitting current density of 1 mA/cm2 can be obtained at only 0.5 V/μm. TCCs have good field emission properties, compared to other forms of carbon field emitter, and may be good candidates for use in field emission display devices.
Co-reporter:Weijie Sun, Yunlong Li, Yang Yang, Yunming Li, Changzhi Gu and Junjie Li
Journal of Materials Chemistry A 2014 - vol. 2(Issue 13) pp:NaN2422-2422
Publication Date(Web):2014/01/08
DOI:10.1039/C3TC32240H
The bottom-up growth method has been the main way to form various AlN nanostructures, but there still exists many problems in the lack of control and non-uniformity. Here, we adopt a firstly top-down plasma etching method to easily fabricate large-area AlN nanocone arrays on magnetron sputtered (002) AlN films, and the unique, pebble-like array morphologies of the AlN films surface greatly induce the whole selective plasma etching process without any masked process. The as-formed AlN nanocones not only keep the crystalline oriented (002) and microstructure of the original AlN film, but also have a good uniformity and controllability in the height and density, as well as the tip-size. These AlN nanocone arrays exhibited an intense broad ultraviolet emission, centered at 3.26 eV and excellent field emission properties, especially showing a tip-size dependent photoluminescence and field emission properties that were remarkably enhanced with decreasing the nanocone tip-size. Our results provide a promising route for the controllable fabrication of AlN nanostructures and practical application of AlN-based various nanodevices in optoelectronics and vacuum-nanoelectronics.
