Fumin Zhang

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.

Ion beam assisted deposition of diamond-like nanocomposite films in an acetylene atmosphere

Abstract In recent years, doped diamond-like carbon (DLC) coatings have been shown to solve some intrinsic application difficulties of DLC, esp. reducing internal stresses and improving thermal stability. Diamond-like nanocomposite (DLN), by incorporating an amorphous Si-O network into the DLC, is a special class of modified DLC coatings, which have many excellent properties and wide applications. In this paper, a diamond-like nanocomposite film was synthesized by an ion beam assisted deposition method in an acetylene atmosphere. The composition and microstructure of the DLN film were investigated by various spectroscopic analyses, including Fourier transform infrared absorption spectroscopy, Rutherford backscattering spectroscopy. Raman scattering spectroscopy, X-ray photoelectron spectroscopy, and ultraviolet-visible absorption spectroscopy.

Synthesis and magnetic properties of iron nitride films deposited on Ge(100) by reactive ion beam sputtering

Iron nitride films were deposited on Ge(100) wafers by a reactive ion beam sputter deposition of iron in an ammonia atmosphere. The composition and microstructure of these films were monitored by Rutherford backscattering spectroscopy analyses and x-ray diffraction experiments. The magnetic properties of these films were determined by a vibrating sample magnetometer. It was found that Ge(100) substrate is profitable for epitaxial growth of the α′′ phase. The optimum ammonia pressure for α′/α′′ phase formation was about 5×10−4 Torr. The saturation magnetization σs of each as-deposited Fe–N film is higher than that of a pure iron film. However, the film with the highest α′/α′′ phase content did not exhibit the largest σs value. The variation of σs of the Fe–N films during annealing at a temperature of 180 °C in a flowing nitrogen atmosphere was also investigated. It was found that there is no direct relationship between the higher σs values and the α′/α′′ phase in these Fe–N films.

Effect of ion impinging on the microstructure and field emission of carbon nanotubes

Effects of ion impinging on the microstructure and field electron emission properties of screen-printed carbon nanotube films were investigated. We observed that the plasma treatment modified the microstructure of CNTs along with the remarkable increase of emission site density. With the prolongation of ion impinging time, the emission current falls down first, and then rises up to higher than that of the untreated films. It is proposed that the change of emission characteristics is due to the different emission mechanisms. After the treatment, electrons are emitted predominantly from the nano-nodes on the tube wall instead from the nanotube tips.

Reactive ion beam assisted deposition of a titanium dioxide film on a transparent polyester sheet

In this work, a titanium dioxide film was synthesized on a thin transparent polyester sheet by a reactive ion beam assisted deposition technique at room temperature. In this deposition process, a pure titanium target was sputtered by an argon ion beam under an oxygen atmosphere, and the growing film was concurrently bombarded by another argon ion beam in order to enhance both the adhesion of the film and the reactivity of the depositing titanium species with surrounding oxygen molecules. The microstructure of the as-deposited film was studied by Rutherford backscattering spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction analyses. The film was examined to be of rutile structure with a (110) preferential orientation. The optical properties of the film were measured by ultraviolet-visible transmittance spectroscopy and Fourier-transform infrared absorption spectroscopy experiments. It was found that the as-deposited titania film was quite transparent in visible region, while ultraviolet light could be filtered effectively, and infrared transmittance could also be reduced evidently. Our titania-coated polyester sheet should be applicable as a shielding cover on car windscreens or window glasses for the purpose of filtering ultraviolet radiation from the sunlight and partially insulating heat as well.

Annealing effect on electron field-emission properties of diamond-like nanocomposite films

The field-emission properties of a Si–O bond-containing diamond-like nanocomposite (DLN) film were investigated as a function of annealing temperature (Ta). It was found that with increasing Ta the emission threshold voltage decreased gradually. After annealing at Ta=500 °C, the emission current decreased significantly. At Ta=700 °C, however, the field-emission properties of the DLN film improved greatly, the threshold field became very low (∼1.5 V/μm), and the emission current rather high (e.g., ∼2.3 μA/mm2 at an electric field of 22 V/μm). The structural variation of the film after annealing at different temperatures was monitored by ultraviolet Raman spectroscopy, spectroscopic ellipsometry, atomic-force microscopy, and electrical resistivity measurements. By using a three-step model: (i) electron injection from the substrate, (ii) electron transport through the film, and (iii) electron emission at the film surface, the annealing effect on field-emission properties of the DLN film were qualitatively in...

Electron emission suppression characteristics of molybdenum grids coated with Pt films by ion-beam-assisted deposition

Pt was deposited onto molybdenum grids by the ion-beam-assisted deposition method. The electron emission characteristics of molybdenum grids, with and without Pt, contaminated by active electron emission substances (Ba, BaO) of the cathode were measured using analogous diode method. The x-ray diffraction, energy dispersive x-ray, and x-ray photoelectron spectroscopy analyses were preformed on the surface of the molybdenum grids coated with Pt. The electron emission current from the molybdenum grid coated with a Pt film is smaller than that without the Pt film, and the mechanism for electron emission suppression of the molybdenum grid coated with the Pt film was discussed.

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...