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ABSTRACT: Ferroelectric copolymer thin film PVDF-TrFE was deposited by spin coating method, and then annealed for the improved crystallization. The XRD and AFM measurements showed that as-formed PVDF-TrFE thin film was composed of the nanocrystallines with 50-80 nm in size and some amorphous phases. Meanwhile, as-formed PVDF-TrFE thin films also show a good polarization inversion property with a switch current of approximately 2.0 microA at a coercive field 40 MV/m. Electron emission testing results showed that under a continuous excitation of applied voltage pulses, PVDF-TrFE thin films exhibited an expected electron emission ability with emission current range of 0.08-0.52 microA, and the related electron emission mechanism was discussed.
Journal of Nanoscience and Nanotechnology 03/2009; 9(2):832-5. · 1.56 Impact Factor
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ABSTRACT: In this article, the direct experimental evidences to determine the effect of grain boundary on local surface conductivity (SC) of diamond films were provided by the measurement using double probe scanning electron microscopy (SEM) technology. Undoped diamond films with (001) orientation were first grown by microwave plasma enhanced chemical vapor deposition and were then hydrogenated at different conditions for SC measurement. In the SEM system, double probes with tiny tip radius severed as two leads were moved along and contacted with the diamond film surface to directly test the local SC of diamond film. The surface electrical property results indicate that for the same distance between the two probes, the local SC of the area across grain boundary is much higher than that of area without grain boundary for the same duration of hydrogenation degrees. In addition, local SC of the area between the two probes increases with the number of grain boundaries in this area, which demonstrates that the grain boundaries play an important role in improving the SC of diamond film. The contribution of the grain boundaries on the local SC of diamond film can be mainly attributed to the defects in grain boundaries that can effectively improve electron transport ability at the diamond film surface.
Journal of Applied Physics 02/2009; · 2.17 Impact Factor
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ABSTRACT: In summary, an individual AlN cone with high aspect ratio was formed by FIB technique. And a nature field emission property of individual AlN cone was measured in a dual probe SEM system. The results indicated that as formed single AlN cone with high aspect ratio exhibits a good field emission ability without any field shielding effect although only has a tiny emission area. Compared with a single Si cone fabricated by the same method, a single AlN cone has a better electron emission ability and hence a good promising candidate of point electron source candidate for the application of vacuum electronic device field.
Vacuum Nanoelectronics Conference, 2007. IVNC. IEEE 20th International; 08/2007
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ABSTRACT: Diamond cone arrays were formed by plasma etching of diamond films in a hot filament chemical vapor deposition (HFCVD) system. The role of CH4 in the formation of diamond cone arrays was investigated. It was found that addition of CH4 to H2 plasma could enhance the plasma intensity and hence the etching efficiency to improve the formation of diamond cones with high aspect ratio and controllable density. The microscopic measurement of the as-formed diamond cones shows that they have an inner core of polycrystalline structure and an outer layer of amorphous carbon. These as-formed diamond cones have exhibited field emission current density of 1 μA/cm2 at threshold field of 5 V/μm. For an applied field of 12 V/μm, the emission current density can rapidly reach as high as 560 μA/cm2. The property of high field electron emission is attributed to the high aspect ratio of as-formed diamond cones and the appropriate cone density as well as the outer amorphous carbon layer which acts as a pathway for electron-hopping conduction during field electron emission.
04/2007;
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ABSTRACT: The nanocrystalline diamond films with different morphologies and roughness were synthesized by a bias-assisted hot filament chemical vapor deposition method. It was found that the nanocrystalline diamond film exhibited low-k dielectric properties with the increase of CH4 concentration during diamond deposition. The low-k nanocrystalline diamond film with grain size of around 40 nm and dielectric constant of 2.4 was obtained at the CH4 concentration of 16% and the bias of −140 V. The low dielectric constant can be mainly attributed to the decrease of diamond grain sizes and the formation of more nanopores in as-grown nanocrystalline diamond film, both of which were discussed in details based on the grain size determined band gap expansion effect and the two-phase dielectric mixing model, respectively.
Applied Physics Letters 03/2007; 90(13):133118-133118-3. · 3.84 Impact Factor
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ABSTRACT: Field electron emission properties of individual diamond cone were investigated using a customized double-probe scanning electron microscope system. The diamond cone was formed by maskless ion sputtering process in bias-assisted hot filament chemical vapor deposition system. The as-formed sharp diamond cone coated with high-sp2-content amorphous carbon exhibited high emission current of about 80 μA at an applied voltage of 100 V. The field emission was stable and well in consistent with the conventional Fowler-Nordheim emission mechanism, due to a stabilization process in surface work function. It has demonstrated the possibility of using individual diamond cone as a point electron emission source, because of its high field electron emission ability and stable surface state after the process of work function stabilization.
Applied Physics Letters 08/2006; 89(6):063105-063105-3. · 3.84 Impact Factor
