Tiemao Shi

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.

DETERMINATION OF THE SP3/SP2 RATIO IN TETRAHEDRAL AMORPHOUS CARBON FILMS BY EFFECTIVE MEDIUM APPROXIMATION

In this article, a method for the determination of the sp3/sp2 ratio for highly tetrahedral amorphous carbon (ta-C) films is presented. This method is an optical characterization according to the Bruggeman effective medium approximation based on simulation of the infrared reflection spectrum. The simulation reflectivity is in good agreement with the experimental spectrum, and the obtained results of sp3 content are in good agreement with electron energy loss spectroscopy data, suggesting that this is an effective method for obtaining the sp3/sp2 ratio of ta-C films.

Simulating the impacts of ecological protection policies on urban land use sustainability in Shenyang-Fushun, China

Chinese cities are undergoing rapid urban sprawl, dramatic landscape change, industrialisation, and ecological damage, which threaten urban sustainable development. The aim of our research was to answer the following question: is it possible to achieve sustainable development through rational ecological protection policies that harmonise future urbanisation, re‐industrialisation, economic development, and sustainable urban land use in these cities? To answer the question, we conducted a simulation of policy impacts on future urban growth and landscape change. We applied a widely used regional assessment and predictive model, SLEUTH, to explore the potential impacts of different ecological protection policy scenarios in the Shenyang-Fushun metropolitan region of China. Future urban growth and landscape changes were projected out to 2050, assuming three different ecological protection policy scenarios: (1) accelerated urban development (AUD), (2) managed urban development (MUD), and (3) limited urban development (LUD). Landscape metrics were used to compare and analyse the impacts of the future scenarios on urban growth and landscape change. Analysis reveals that urban growth and landscape fragmentation increase in all scenarios, but future urban growth area and landscape pattern differ among the scenarios. The AUD scenario will cause excessive urban growth, major land loss, and serious landscape fragmentation. The LUD scenario shows good land resource protection and low landscape fragmentation, but the urban growth rate is unrealistically low, reducing the extent of likely re-industrialisation and economic development. The MUD scenario shows moderate urban growth and landscape fragmentation. It would be the most suitable scenario for the industrial metropolitan area under study if the urban sprawl can be controlled, and it would better harmonise re-industrialisation, ecological health, and land preservation and achieve sustainable development in the area.

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.

Field emission from amorphous diamond films prepared by filtered arc deposition

Nonhydrogenated amorphous carbon films have been prepared by filtered arc deposition (FAD), which provides carbon ions with optimum kinetic energies at practical deposition rates. It was found that the carbon atoms were so highly tetrahedrally bonded that the films were referred to as amorphous diamond (α-D). The field emission behaviour of the α-D films has been studied for the first time. The field emission current more that 10 μA was detected at an electric field intensity of 18 V/μm. Such a low threshold field provides the designer of flat panel displays with an opportunity to develop a planar emitter, rather than the conventional Spindt-tip field emitter which requires lithographic and microstructural burdens.

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.

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.

Optical study of low energy ion-beam-assisted deposited diamond-like carbon films

Abstract Diamond-like carbon (DLC) films were prepared on single crystal silicon wafers by low energy ion-beam-assisted deposition (IBAD). The microstructure characteristics, thickness, optical band gap, sp3 fraction and so on, of these DLC films have been analyzed by infrared reflection, Raman and ultraviolet-visible optical spectroscopy experiments. It was found that the infrared reflectivity of the as-deposited DLC films depends on both the wave number and deposition conditions. The measured infrared reflection spectra were fitted by a Bruggeman effective medium approximation (EMA) method. The calculated spectra coincided very well with the experimental data, and it was demonstrated that the as-deposited DLC films were mainly composed of sp3 bonded carbon atoms. The Raman spectra showed a broad asymmetric band in the range of 1500–1580 cm−1, which is a typical characteristic of an amorphous diamond-like structure. The optical band gap of the DLC films was determined to be 0.54–1.0 eV from UV transmittance spectra.

The carbon fixation and oxygen release benefits of urban parks' vegetation in Shenyang by adopting GIS with RS

Urban parks provide numerous social, environmental, and economic services of measurable value to a city. To better understand the importance of the urban parks, by using Quickbird satellite image (QB) also adopting Geographic Information System (GIS), we employ the methods of Image Interpretation, Site Survey, Photosynthetic Experiment and Forestation Costs Method, assessment the quantities and monetary benefits of Vegetations in Urban Parks. The results show that the vegetations of the studied Parks in Shenyang were estimated to reduce atmospheric CO2 by 197847 t annually, and this benefit is valued at 51618.4 thousand Yuan in total; meanwhile, the vegetations release O2 by 147149.3 t annually, so this benefit is valued at 51933.4 thousand Yuan in all. Therefore, the total monetary benefit of vegetations in urban parks through fixing carbon and releasing oxygen is 103551.8 thousand Yuan.