Physical Vapor Deposition is nowadays introduced in industrial production of metal strip coatings. When employed in the field of flat stainless steel, such new plasma technologies offer not only evolutions of present products, but create new products and so new markets. Besides, in comparison with conventional coating processes such as electroplating or conversion in chemical bath, on-line plasma deposition technologies represent alternative processes in respect of the new European environmental rules.

Stainless steel strip until 1.5 meters in width coated with chromium nitride nanolayers have been achieved by Cathodic Magnetron Sputtering at room temperature. Deposition parameters have been optimized in order to get chromium nitride nanolayers, in the first hand with uniformity and reproducibility, in the second hand with anti-abrasive properties and stainless steel aestheticism. Several stoechiometries of Cr:N have been attempted on austenitic AISI 304 and ferritic AISI 430 stainless steels, by monitoring N₂ flow rate.

Morphology, microstructure and composition of Cr-N coatings on stainless steel were characterized at nanoscale by Transmission Electronic Microscopy, Atomic Force Microscopy, X-ray Diffraction, FEG-Scanning Electron Microscopy and X-ray Photoelectron Spectroscopy. It was shown that Cr:N stoechiometry has a strong influence on the visual aspect of the coated stainless steel strips.

Adherence, hardness and friction behavior of the different chromium nitride nanolayers were deduced from nanoindentation measurements, nanoscratch and nanotribology tests. Results from mechanical macrotests such as pion disc, normalized Taber abrasimeter, and in-house abrasion test are presented. Mechanical properties in relation with stoechiometry, structure and thickness of the Cr-N thin films are discussed. High performance of flat stainless steel functionalized by Cr-N nanolayers against abrasion are discussed in relation with different coating features.

CrCu(N) coatings with a nanocomposite structure have been identified as offering excellent wear resistance for applications involving abrasion, erosion and impact wear. Due to the low solid state miscibility of Cr and Cu (the former with or without an interstitial solid solution of N), predominantly metallic nanocomposites can be produced with high resilience and toughness, and a hardness close to that of ceramic coatings (>15 GPa). Also, by having low coating internal stress and an elastic modulus more closely matched to that of the substrate, the full benefit of these coatings can be obtained.

In this paper we discuss the thermal stability and high temperature oxidation resistance of CrCu(N) coatings of different composition, deposited by twin-crucible (one Cr-source and one Cu-source) Electron Beam Physical Vapour Deposition (EBPVD), in order to control independently each vapour source material. Plasma assisted EBPVD processes may be more attractive than sputtering for commercial applications, as potentially they offer lower running costs, higher maximum deposition rates, and improved flexibility for tailoring the through-thickness coating composition.

To characterise these coatings, techniques such as X-ray diffraction analysis and scanning electron microscopy have been employed. Hardness has been determined for coatings in both the as-deposited and the annealed condition. High temperature oxidisation resistance is investigated by means of thermo-gravimetric analysis, X-ray diffraction and scanning electron microscopy.

As a new functional material, a-Si:H (hydrogenated amorphous silicon) films have been widely applied^[1] to semiconductor devices, such as photosensitive devices, solar cells and thin film transistors (TFT) etc. However, light-induced metastable defects or in other words Staebler-Wronski effect limits its efficiency of the photonic devices as an inexpensive semiconductor material. So it is important to study the stability of a-Si:H. Microwave electron cyclotron resonance-chemical vapor deposition (MWECR-CVD) due to its attractive features has been used for the deposition of the a-Si:H films. However, there still exist some problems in the films prepared by the conventional MWECR-CVD system, such as poor stability, low photosensitivity, etc. So, based on the previous work,^[2][3] we develop a new system assisted by hot wire to obtain high-quality a-Si:H films. The experimental results indicate that in the microstructure of the a-Si:H films, the concentration of dihydride is decreased and a trace of microcrystalline occurs, which is useful to improve their stability,and that in the optoelectronic properties of the a-Si:H films, the deposition rate reaches above 2.0nm/s and the photosensitivity increases up to 4.71×105.

^[1]Kitagawa M, Setsune K, Manabe Y and Hirao T J. Appl. Phys. 61(1987)2084

^[2]Yin S Y and Chen G H Phys. 4 (2004) 272 (in Chinese)

^[3]Hu Y H, Yin S Y, Chen G H et al. Acta Phys. Sin. 53(2004) 2263 (in Chinese).

Boron and borides are well-known compounds used in hard coatings, because of excellent high-temperature properties. Chemical Vapor Deposition is an important route for their synthesis. One of the main sources is boron trichloride. For example, boron carbide may be synthesized by CVD from BCl₃/H₂/CH₄ mixtures. However a precise control of the deposit quality (microstructure, stoichiometry) is difficult to achieve, due to an important sensitivity to processing conditions, like temperature, pressure, flow rate and gas mixture composition. In order to minimize development costs, CVD modeling is an attractive option.

In this context, a first step is to set up a homogeneous chemical mechanism, featuring thermochemical and kinetic data for a large set of species and reactions. Since the gas-phase chemistry of the B-Cl-H subsystem is still poorly known, this work is aimed at its determination, combining detailed modeling and experimental measurements.

This paper will present results on the ab-initio study by the G3B3 computational method. Potential energy surfaces have been generated for numerous reaction paths, and have allowed to identify transition states, from which reaction rates have been deduced using the canonical variational transition state theory or the RRKM theory. Then, a coherent gas-phase species and reaction set is obtained and inserted in a chemical kinetic solver for validation.

The model results are compared to IRTF data on the low-pressure decomposition of BCl₃/H₂ mixtures obtained in a tubular furnace featuring a hot-zone.

Transition metal nitrides have been widely used in applications such as cutting tools, protection wear and machinery components, because of their superior tribological, chemical and physical properties. (Cr,Al)N has gained much attention as a substitute for (Ti,Al)N, and has been investigated with respect to, microstructure, mechanical properties, thermal stability, and cutting performance. Recently, we developed the newly (Cr,Al)N based films by adding foreign metal such as Y and Si, which are expected to lead formation of stable oxide and amorphous at elevated higher temperature. From the XRD results of samples after vacuumed annealing, incorporation of Si and Y to (Cr,Al)N prevented Cr₂ N phase segregation at 800 ºC; and cubic phase stability was better than (Cr,Al,Si)N and (Cr,Al,Y)N.

In this study, (Cr,Al,Y)N, (Cr,Al,Si)N and (Cr,Al,Si,Y)N were annealed under vacuum or air pressure with ranging from 800 to 1100°C. Changes in micro-hardness and microstructure as a function of annealing temperature were studied and discussed based on X-ray diffraction method, electron microscopy.

The high power pulsed magnetron sputtering (HPPMS) has been suggested as the promising technology for the enhancement of the ionization rate of sputtered atoms in 1999. The potential of this technology has attracted keen interest because it can transiently produce high-density plasma with high electron-impact excitation efficiency during the pulse-on period. However, the HPPMS has the fatal drawback that the deposition rate is extremely low even though it depends on the target material. In this presentation, a novel pulsing technique will be proposed for the enhancement of the sputtering rate of the target material in the HPPMS. In the new pulsing method, two pulses of the high-voltage HV pulse with the peak voltage of about -1.7 kV and the pulse width of about 5 µms and the low-voltage LV pulse with the minimum voltage of 500 V and the pulse width of 10 µms were sequentially applied to the cathode. The repletion frequency of the resulted cathode pulse was 10 kHz and so, the pulse-off duration was about 80 µms. Using the dual pulse with only an additional low voltage pulse, we could obtain the deposition rate of the Ti film more than two times higher than that in the single high-power pulse discharge. The mechanism on the enhancement of the deposition rate will be discussed from the time-resolved diagnostic results.

¹The authors would like to thank the Engineering and Research Center (grant no. R11-2000-086-03007-0) for their financial support of this research.

²The company Plasmart Ltd. Is specially acknowledged for the technical support and the supply of probe acquisition system (SLP2000$super ®$).

Since the discovery of carbon nanotubes, much technological and scientific excitement has been raised by the discovery of various forms of nanostructures. Recently, coaxial nanocable-like one-dimensional (1D) structures comprising different kinds of materials have been successfully synthesized not only for making nanometer scale electronic devices with a variety of functions, but also for the protection of 1D structures from contamination or oxidation. Hexagonal gallium nitride (GaN), an important semiconductor with a wide-band-gap of 3.4 eV at room temperature, is an ideal material for the fabrication of blue light-emitting diodes and laser diodes. On the other hand, the formation of SiO_x sheaths, which exhibit excellent insulating characteristics on the exterior of nanowires, is essential not only to avoid interference between building blocks of a complex nanoscale circuit, but also to protect nanowires from contamination. In particular, the insulating SiO_x sheath is required to fabricate field effect transistors and sensor devices based on nanowires. Furthermore, the SiO_x coating layer is optically transparent for the visible absorption/emission of semiconductor nanowires, resulting in limited destruction of their intrinsic optical properties. Since the three-dimensional geometry with respect to bundles of 1D structures requires high degree of the process control for achieving the conformal coating, it is worth developing suitable growth method. For potential application to ultra-large-scale-integration (ULSI) fabrication requiring a simple and well-controllable process, the feasibility of using two-step process was investigated.

In this study, pre-grown GaN nanowires were coated via a sputtering technique using a Si wafer as a target. We have investigated comparatively the samples before and after the coating in terms of their structural and photoluminescence (PL) characteristics. This novel approach to fabricate the nanowire heterostructures will be a step toward the potential applications of composite nanowires to nanodevices.