Zhongyu Chen

Overall energy model for preferred growth of TiN films during filtered arc deposition

TiN films with different preferred crystalline orientations have been prepared by a new cathodic arc evaporation technique - filtered arc deposition (FAD). The evolution of the preferred orientation in the TiN films was investigated systematically. Three kinds of preferred orientation, i.e. the (200), (111), and (220) preferred orientation, were achieved continuously in one deposition procedure by varying the film thickness and substrate bias which determines the bombarding energy of the deposited energetic particles. At the initial stage of film growth, the (200) orientation is dominant at a lower substrate bias. When the film becomes thicker and/or substrate bias increases, the preferred orientation will be (111) instead of (200). If the substrate bias increases further, then the preferred (220) growth occurs at any film thickness. The evolution of the preferred orientation from (200) to (111) and then to (220) is discussed on the basis of a new concept, the so-called overall energy which consists of the surface energy, the strain energy, and the stopping energy. The preferred orientation of TiN films is determined by the competition between the surface energy, the strain energy and the stopping energy.

Optimization of two-monomer-based photopolymer used for holographic recording

Abstract Studies of optimization and characteristics of a dry film photopolymerizable recording material are presented. The effect of variation of the concentration of each component was investigated. Diffraction efficiencies of 55%, with the energetic sensitivity of 60 mJ/cm 2 , have been obtained in the photosensitive films of 150-μm thickness with a spatial frequency of 2750 lines/mm. An image has been successfully stored in the material with a small distortion.

Optical and electrical properties of nitrogen incorporated amorphous carbon films

Nitrogen incorporated amorphous carbon (a-C:N) films on silicon (111) wafer, quartz, and Ti/C substrates with nitrogen concentration up to 20 at. % are prepared by filtered arc deposition. The nitrogen concentration and area density of the films were measured by Rutherford backscattering. The electrical properties of the films were investigated by Hall electrical measurements. The optical properties of the films were characterized by ultraviolet–visible and infrared reflection spectrometry. Results indicate that the optical band gap and area density of a-C:N films decrease with increasing nitrogen pressure, accompanied with an increase of nitrogen concentration and reflectivity of the films. Furthermore, the influence of nitrogen concentration on the optical band gap of the films is discussed. The dielectric constant, refractive index and absorption coefficient of a-C:N films in infrared region were investigated. The results indicate that the optical constants of a-C:N show considerable variation with wav...

Phase-shifting apodizer for next-generation digital versatile disk

The next generation digital versatile disk (DVD) using blue lasers will have a capacity of 13 to 15 Gbytes. Compared with current DVD, the wavelength will be shorter and the numerical aperture (NA) will be higher. But with the increase of NA and decrease of wave length, the depth of focus (DOF) decrease rapidly, which makes it hard for the servo-system to track. We propose an optimized three-portion phase-shifting apodizer to increase the depth of focus and at the same time minimize the spot size, which makes the DOF of next generation DVD comparable to current DVD. The simulation result shows that an optical system with this apodizer also has a good defocus characteristic

Electrical properties of nitrogen incorporated tetrahedral amorphous carbon films

Abstract The electrical properties of nitrogen incorporated tetrahedral amorphous carbon (ta-C:N) films studied by Hall measurements over the range of 15–300 K were reported. Results indicated that the electrical properties of ta-C:N films are related to nitrogen pressure, which was the only variable during film deposition. The electrical resistivity of the ta-C:N films decreases with nitrogen pressure, accompanied by an increase of nitrogen concentration in the films. The influence of thermal annealing on the electrical properties of ta-C:N films was also investigated. The variation of the electrical properties of ta-C:N films may arise from the development of graphite-like structures in these films due to the incorporated nitrogen and annealing effects.

Preparation of thin films by filtered arc deposition and ion assisted arc deposition

Abstract The present work focuses on Filtered Arc Deposition (FAD) and Ion Assisted Arc Deposition (IAAD) techniques. The properties of TiN, a-diamond and a-C:N films prepared by FAD and IAAD have been investigated in respect to surface morphologies, field emission behavior and optical properties.

Optical properties of CNx films prepared by filtered arc deposition

Abstract CN x films on silicon (111) wafer, quartz and Ti C substrates with nitrogen concentration up to 20 at% have been prepared by a new plasma deposition technique-filtered arc deposition. The nitrogen concentration and area density of the films were measured by Rutherford back-scattering. The optical properties of the films were characterized by ultravioletvisible and infrared reflection spectrometry. Results indicate that the optical band gap and area density of the CN x films decrease with increasing nitrogen pressure, accompanied with an increase of nitrogen concentration and reflectivity of the films. Furthermore, the influence of nitrogen pressure on the optical band gap of the films is discussed.

Surface morphology of nitrogen doped tetrahedral amorphous carbon films on silicon by atomic microscopy imaging

Abstract The results of studies of the surface morphology of nitrogen doped tetrahedral amorphous carbon (ta-C) films with atomic force microscopy (AFM) are reported. The films were prepared by filtered arc deposition (FAD). N is introduced into the films during growth by injecting N 2 gas into a plasma stream formed by a carbon cathode vacuum arc. AFM revealed that the surface on formed films is uniform and smooth on the nanometerscale and the root-mean-square roughness of the films surface is calculated to be approximately 0.23–0.26 nm. The influence of N doping on the surface morphologies of ta-C films are discussed.

Field emission from filtered arc deposited amorphous diamond

Abstract In this work, amorphous diamond (a-D) films have been prepared by filtered arc deposition (FAD). Field emission data from the a-D film were obtained using planar diode structure. Emission currents in the range of 20–40 μ A were detected at an electric field of 20 V μ m −1 . A mechanism for electron emission from the a-D film is discussed. FAD a-D films had a low effective work function (1.0 eV) and negative electron affinity (−0.2 eV). In addition, uniform and stable emission can be achieved for FAD a-D films.

Amorphous carbon and carbon nitride films prepared by filtered arc deposition and ion assisted arc deposition

In the present work, filtered arc deposition (FAD) and ion assisted arc adposition (IAAD) techniques have been used to deposit amorphous carbon (a-C) and carbon nitride (a-CN) films. Atomic and electronic structures of a-C films have been characterized by electron diffraction and electron energy loss spectra (EELS). In addition, the properties of a-C and a-CN films have been investigated with respect to field emission behavior and optical properties.