Yukun Zhu

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.

Characteristics of ZnO : Zn phosphor thin films by post-deposition annealing

Abstract ZnO:Zn phosphor thin films were prepared by ion beam assisted deposition (IBAD). Post-deposition annealing of these films was performed at temperature from 100°C to 1000°C in N2 and air, respectively. Several analysis techniques were employed to characterize their composition, structure and photoluminescence. Two different bands of luminescent peaks, which are UV/violet (380–420 nm) and blue/green (470–530 nm) luminescence, were found in the PL spectra of these films. The results show that the intensity of the blue/green light is strongly affected by the temperature of annealing which may result from the recovery of structural defects, the homogenization and the evaporation of excess Zn. However, the contributions of these processes are different at different temperature ranges. We also find that the films annealed in N2 ambient show stronger luminescent intensity than those in air ambient.

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.

Electron field emission from a patterned diamondlike carbon flat cathode

A 300-nm-thick diamondlike carbon (DLC) film was deposited on to a heavily doped n-type Si (111) wafer by filtered arc deposition. A flat thin film cylindrical emitter array was then fabricated by reactive-ion etching the DLC film. Its electron field emission properties were studied using a simple diode structure. A field emission current of 0.1 μA was detected under an electric field of 5.2 V/μm. As large as 64.1 mA/cm2 of field emission current density was achieved after an activation process under a 39 V/μm field. An image formed on the anode screen showed that electron field emission from the DLC flat emitter array is rather uniform. The field emission behavior is also consistent with Fowler–Nordheim theory. Hydrogen plasma surface treatments were found to enhance the field emission properties.

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.

ZnO:Zn phosphor thin films prepared by filtered arc deposition

ZnO:Zn phosphor thin films, which can be used in field emission displays, were prepared by filtered arc deposition. Depositing parameters, including bias and temperature of the substrates, duct current and partial pressure of O2 in the depositing chamber, were varied to synthesize the films. Both dc and rf bias were utilized in the process. The structure, thickness, luminescent intensity, and morphology of the films were investigated. Most of the as-deposited films contained both crystalline and amorphous phases. It was found that lower bias, lower substrate temperature, rf bias, and lower duct current tended to obtain thicker films. Neither lower nor higher O2 concentration in the chamber obtained thicker films. There are two categories of luminescent peaks, the UV/violet emission (370–420 nm) and the blue/green light (470–530 nm), in the deposited ZnO:Zn films. An interesting relation between PL intensity and morphology was found. Some samples with a special type of individual tip-like structures showed...

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.