Chizi Liu

A new method for inner surface modification by plasma source ion implantation (PSII)

Abstract A new method for inner surface modification, named grid-enhanced inner surface modification by plasma source ion implantation (PSII), was proposed and demonstrated in this paper. By introducing an RF plasma core, which is produced between a central cathode and a coaxial grid electrode, and sputtering the cathode, uniform ion implantation and film deposition on the inner surface of a tubular sample can be realized based upon the PSII technique.

Inner surface coating of TiN by the grid-enhanced plasma source ion implantation technique

An inner surface coating of a tubular sample was realized by a new method of grid-enhanced plasma sourceion implantation (GEPSII), which is an extension of previous plasma sourceion implantation inner surface modification. In GEPSII, a rf plasma core is produced between a center cathode and a grid electrode, which are coaxially arranged inside the tubular sample. Negative high voltage pulses are applied between the grid electrode and the inner surface of the tubular sample, thus an accelerating field for positive ions can be established between the grid electrode and the inner surface of the sample. In addition, particles of solid matter can be introduced into the rf plasma by sputtering the cathode, thus, it is possible to realize metal ion implantation and film deposition. In this article, the concept of GEPSII and some preliminary measurement results of this method are presented, and TiN films are produced on the inner surface of a tubular sample, which is a cylinder of an automobile. The plasma density profiles and plasma electron temperature inside the sample are measured by a Langmuir probe. It is shown that the axial plasma density profile is rather uniform in GEPSII. TiN films were also deposited on single-crystal silicon substrates, which are arranged on the inner surface of the cylinder.

Characteristics of (Ti,Ta)N thin films prepared by using pulsed high energy density plasma

(Ti,Ta)N films were prepared by pulsed high energy density plasma (PHEDP) from a coaxial gun in N2 gas. The coaxial gun is composed of a tantalum inner electrode and a titanium outer one. Material characteristics of the (Ti,Ta)N film were investigated by x-ray photoelectron spectroscopy and x-ray diffraction. The microstructure of the film was observed by a scanning electron microscope. The elemental composition and the interface of the film/substrate were analysed using Auger electron spectrometry. Our results suggest that the binary metal nitride film, (Ti,Ta)N, can be prepared by PHEDP. It also shows that dense nanocrystalline (Ti,Ta)N film can be achieved.

Pulsed high energy density plasma processing silicon surface

Pulsed high energy density plasma (PHEDP) is a new material modification technique, which has the features of: high energy density (1–10 J/cm2), high plasma density (1014–1016 cm−3), high electron temperature (10–100 eV), high directed plasma velocity (10–100 km/s) and short pulse duration (10–100 μs). PHEDP interacting with material will result in rapid melting and re-solidification of surface layer with a quenching rate up to 108 K/s; thus the material surface properties are modified. At the same time, PHEDP contains condensable ions or/and atoms, so a thin film layer can be formed on the modified surface and the deposited layer can be mixed with the substrate (or previous deposited layer) during following pulses. Therefore, this technique actually combines film deposition and mixing into one step. In this paper, we have reported the research results on the metallization of Si by PHEDP. The Tiue5f8Si reactions under PHEDP are also discussed.

Preparation of Ta(C)N films by pulsed high energy density plasma

The pulsed high energy density plasma (PHEDP) is generated in the working gas due to a high-voltage high-current discharge, within a coaxial gun. In PHEDP surface modification, discharge is applied for preparing the amorphous and nanostructured high-melting materials as thin films deposited on various substrates. In this investigation, Ta(C)N films were deposited using PHEDP on stainless steel. Pure tantalum and graphite were used as the inner and outer electrodes of the PHEDP coaxial gun, respectively. Nitrogen was used as the working gas and also one of the reactants. Preliminary study on the films prepared under different conditions shows that the formation of Ta(C)N is drastically voltage dependent. At lower gun voltage, no Ta(C)N was detected in the films; when the gun voltage reaches or exceeds 3.0 kV, Ta(C)N occurred. The films are composed of densely stacked nanocrystallines with diameter less than 30 nm, and some grains are within 10 nm in diameter.

Spatial distribution of the high energy density plasma in a coaxial gun for surface modification

Summary form only given. The coaxial plasma gun, by generating the pulsed High Energy Density Plasma (HEDP) with a simple method, is an effective method for materials surface modification. It incorporates fast quenching, ion implantation and film deposition into one process, and produces a modification layer of strongly adhesive to the substrate. The spatial distribution of the plasma stream ejected from the coaxial gun determines the surface modification. In this paper, this problem was investigated on a 40 kV gas-puff coaxial plasma gun by using thermal sensitive (Fax) paper and dosimeter.

A novel instrument for material surface treatment by pulsed high power density plasma beam

While great interest has been focused on low temperature plasma for material processing, the concept of using pulsed high speed and high temperature plasma beam for material surface treatment was put forward. Thus a novel instrument based on Thetatron-Pinch was built up and the plasma beam with a temperature of several hundred eVs and a density up to 1016u2009cm−3 was created uniformly over a large cross section. The plasma beam was then accelerated by a sample bias of 0–2.0 kV under a high vacuum circumstance. The energy density exerted on the sample surface is 1–20u2009J/cm2 with a duration time of less than 10 μs, which is comparable to that of laser treatment. Preliminary experiments indicate that this method has the combining feature of laser treatment and ion implantation techniques when it is used for surface modification; moreover, a transient high temperature and high pressure environment exists on the treated surface in this technique and the plasma contains a high concentration of radical particles. Bo...

Modified Thomson spectrometer for the detection of low energy (<1 keV) high power ion beams

By applying an after acceleration electric field, the detection and registration of the ion species and spectral distribution of low energy ion beams (<1u2009keV) have been achieved by the Thomson spectrometer with CR-39 nuclear track detector as detection plate. With the use of this modified spectrometer, the low energy and high energy density plasma ion beams generated by a coaxial plasma gun have been detected and investigated. The ion beams were mainly N+ ions and were distributed in the energy range from E∼0.12 to 0.4 keV.

Simulation methods of ion sheath dynamics in plasma source ion implantation

Progress of the theoretical studies on the ion sheath dynamics in plasma source ion implantation (PSII) is reviewed in this paper. Several models for simulating the ion sheath dynamics in PSII are provided. The main problem of nonuniform ion implantation on the target in PSII is discussed by analyzing some calculated results. In addition, based on the relative researches in our laboratory, some calculated results of the ion sheath dynamics in PSII for inner surface modification of a cylindrical bore are presented. Finally, new ideas and tendency for future researches on ion sheath dynamics in PSII are proposed.

Structural and chemical diagnosis of magnetic multilayers by RAFS and XRF techniques

Abstract Elemental distribution of Ni, Mn and Co at the NiMn/Co and Co/NiMn interfaces of ultra-thin NiMn/Co multilayers and that of Bi in the Cu/NiFe/Bi/FeMn/Cu multilayers have been investigated by X-ray reflection anomalous fine structure (RAFS) and X-ray fluorescence (XRF) methods. For the as-grown sample of the NiMn/Co multilayers, a chemical intermixing region with the chemical component varying gradually from Co to CoMn is observed at the Co/NiMn interface, but not at the NiMn/Co interface. After annealing at 250 °C for 3, 10 and 20 h respectively, this gradual chemical component variation also appears at the NiMn/Co interface. For the Cu/NiFe/Bi/FeMn/Cu multilayers, the depth distributions of the Bi atoms of the samples with different thicknesses of Bi layer are obtained. The results show that the diffuse ability of Bi is strongly dependent on the thickness of the Bi layer.