D.S Mao

ZnO/Zn phosphor thin films prepared by IBED

Abstract ZnO/Zn phosphor thin films were prepared by ion-beam-enhanced deposition (IBED). Post-deposition annealing of these films was performed at temperatures from 100 to 1000°C in a N 2 atmosphere. RBS, XRD and PL spectra were employed to characterize these films. It was detected that there is a large amount of excess Zn in the prepared films. An amorphous structure was found in the films deposited without ion bombardment, and simultaneous ion bombardment could cause the films to contain crystalline phases and even greater excess Zn. The PL spectra showed that UV/violet and blue/green luminescence was excited in ZnO/Zn films. The annealing strongly affected the visible luminescence. Possible reasons may include the recovery of structural defects, homogenization, and evaporation of excess Zn with different contributions at different temperature ranges.

Electron field emission from diamond-like carbon films and a patterned array by using a Ti interfacial layer

Electron field emission from diamond-like carbon (DLC) films deposited on Si, Ti/Si, and Au/Si substrates by a filtered arc deposition technique was studied. As compared to DLC/Si and DLC/Au/Si, electron field emission from DLC/Ti/Si was enhanced, showing an increased emission current density and emission site density (∼1.2×103/cm2). An emission site density up to 2.2∼2.2×103/cm2 was obtained after the DLC/Ti/Si had been annealed at 430 °C for 0.5 h. A patterned DLC/Ti/Si array fabricated by the oxygen reactive ion beam etching technique showed further field emission enhancement. An emission site density up to 3.2∼3.5×103/cm2 and a threshold field as low as 2.1 V/μm were achieved. It was shown that the low potential barrier at the interface and high local geometric electric field enhancement around the edges produced by reactive ion beam etching were possible causes of the enhancing effects. It could also be explained by Geis’ metal-diamond-vacuum triple junction emission mechanism.

Enhanced electron field emission properties of diamond-like carbon films using a titanium intermediate layer

Substantially improved uniformity and enhanced electron field emission properties of hydrogen-free diamond-like carbon (DLC) films were obtained using a titanium intermediate layer after the annealing process. Large emission current densities of 2.08 mA cm-2 at 14.3 V µm-1 and 7.20 mA cm-2 at 25.7 V µm-1 were achieved for DLC/Ti/Si film annealed at 430 °C for 0.5 h. Its field emission was much more uniform than that of as-prepared DLC/Ti/Si and DLC/Si films. Secondary ion mass spectroscopy (SIMS) showed that C has been amply diffused into the Ti layer. An x-ray photoelectron spectroscopy (XPS) spectrum of the annealed DLC/Ti/Si film after 10 min of argon ion sputtering showed the formation of TiC at the interface between the DLC and Ti/Si substrate. This interaction and interdiffusion of C and Ti could significantly lower the Schottky barrier height between the DLC and Ti/Si substrate. The result was that electrons induced from the Ti/Si substrate can be easily penetrated into DLC films, which enhances the field emission properties.

Diamond-like carbon films prepared by filtered arc deposition for electron field emission application

Abstract In this paper, hydrogen-free diamond-like carbon (DLC) films were prepared by filtered arc deposition. The effect of sp 3 content and annealing on electron field emission properties of the DLC films was studied. A patterned DLC flat thin film column emitter array was fabricated by oxygen reactive ion beam etching (RIBE) technique. It was shown that the threshold field of the DLC films was approximately 3–15 V/μm. Field emission site density ranged from 5×10 2 to 2×10 3 /cm 2 . The field emission mechanism of the DLC films is also discussed.

Effect of annealing on electron field emission properties of hydrogen-free amorphous carbon films

In this paper, a series of 200-nm-thick, hydrogen-free, amorphous carbon (a-C) films deposited on heavily doped Si (111) by filtered arc deposition (FAD) were isothermally annealed at 200, 400, 600, 800, and 1000°C for 30 min. Electron field emission from these films was studied by using a diode structure device. It was shown that field emission properties of the films were degraded with increasing annealing temperatures. But after being annealed at 800°C for 30 min, the a-C film showed enhanced field emission properties compared with the unannealed a-C film. Atomic force microscopy (AFM) showed that a-C film annealed at 800°C had dense protrusions on the surface. It was shown that annealing can have a remarkable effect on field-emission properties of the a-C films.

Electron field emission from nitrogen-containing diamond-like carbon films deposited by filtered arc deposition

Abstract In this paper, electron field emission properties and fluorescent displays of 300 nm thick nitrogen-containing diamond-like carbon (DLC:N) films are reported. The films were deposited on to highly n -doped Si (111) substrates by filtered arc deposition (FAD) with different N 2 partial pressures (0.01, 0.05, 0.1 Pa) in the deposition chamber. Their electron field emission properties were studied using a simple diode structure. It was shown that the DLC:N film possessed enhanced field emission properties when a N 2 pressure of 0.05 Pa was used. Emission current of 0.1 μA was detected under the electric field of 8.1 V/μm. An emission current density of 0.204 mA/cm 2 was obtained under 17.8 V/μm.

Electron Field Emission from Different sp3 Content Diamond-Like Carbon Films

Different sp3 content diamond-like carbon films are deposited on to highly n-doped Si(111) substrates by a new plasma deposition technique-filtered arc deposition. Their electron field emission properties are studied by using a simple diode structure. It is showed that the turn-on field is decreased and field emission current density is increased with the increasing sp3 content (75-80%, 80-83%, and 88-90%) of the films. Field emission current of 0.1 μA from the three samples was detected under the electric field of 10.1, 5.6, and 2.9 V/μm and emission current density of 4.4, 15.2, and 43.2 μA/cm2, respectively, under 14.3 V/μm. Fowler-Nordheim (F-N) plots of the three samples nearly show of lineaity indicating that electron field emission obeys F-N theory.

High sp(3) content hydrogen-free amorphous diamond: an excellent electron field emission material

Details are given of a study of the characteristics of field-induced electron emission from hydrogen-free high sp3 content (>90%) amorphous diamond (a-D) film deposited on heavily doped (ρ<0.01ω·cm) n-type monocrystalline Si (111) substrate. It is demonstrated that a-D film has excellent electron field emission properties. The emission current can reach 0.9 μA at applied field as low as 1 V/μm, and the emission current density can be about several mA/cm2 under 20 V/μm. The emission current is stable when the beginning current is at 50 μA within 72 h. Uniform fluorescence display of electron emission from the whole face of the a-D film under the electric field of 10–12 V/μm is also observed. The contribution of excellent electron emission property results from the smooth, uniform, amorphous surface and high sp3 content of the a-D film.

Effect of interface layers on electron field emission properties of amorphous diamond films

Hydrogen-free high sp3 content amorphous diamond (AD) films are deposited on three different substrates—Au-coated Si (Au/Si), Ti-coated Si (Ti/Si) and Si wafers. Electron field emission properties and fluorescent displays of the above AD films are studied by using a sample diode structure. The compositional profile of the interfaces of AD/Ti/Si and AD/Si is examined by using secondary ions mass spectroscopy (SIMS). Because of the reaction and interdiffusion between Ti and C, the formation of a thin TiC intermediate layer is possible between AD film and Ti/Si substrate. The field emission properties of AD/TI/Si are sufficiently improved, especially its uniformity. A field emission density of 0.352 mA/cm2 is obtained under an electric field of 19.7 V/μm. The value is much more than that of AD/Au/Si and AD/Si under the same electric field.