Zou Shichang

Improvement of oxidation resistance of TiAl by ion-beam-enhanced deposition coatings

Abstract Silicon nitride films of different thicknesses were synthesized on the intermetallic compound TiAl by ion-beam-enhanced deposition. Auger electron spectroscopy shows that the silicon nitride film is composed of a thin silicon-enriched top layer, a stoichiometric Si 3 N 4 layer and a mixing layer at the film-substrate interface. It was found that a small amount of aluminium and titanium diffused into coatings from X-ray photoemission spectroscopy measurements. Cyclic oxidation tests were carried out on the TiAl coupons coated with nitride films of thicknesses of 0.5, 1 and 2 μm. The nitride film of 0.5 μm thickness demonstrated an excellent oxidation resistance at 1300 K for at least 30 cycles (600 h). However, this effect decreases as the thickness of the coating increases. Scanning electron microscopy observation and energy-dispersive X-ray spectroscopy revealed that the excellent oxidation resistance came from the formation of a thin layer rich in Al 2 O 3 beneath the outer TiO 2 layer during the oxidation period. The less effectiveness for oxidation resistance of the thicker film resulted from the local fracture of the coating and the spalling off of the oxide scale.

Improved activation in Si+ and P+ dually implanted InP

Dual implantations of Si+ and P+ at elevated temperatures were used to study the amphoteric property of Si in InP. The electrical properties from Hall measurements indicate that improved activation is obtained in dually implanted samples, and in-diffusion of Si species is inhibited by implantation of P species. Photoluminescence spectra at 11 K proved that the implantation of P species can suppress the formation of deep Si acceptors formed from substantial Si at P sites effectively. All these results demonstrate that as in GaAs, Si is an amphoteric dopant in InP and that high carrier concentration can be attained by dual implantations.

THE EFFECT OF N+ ION-BEAM BOMBARDMENT ON AQUEOUS CORROSION OF IRON

Abstract As the second part of our program, an attempt has been made to investigate the effect of N + ion beam bombardment on the aqueous corrosion behaviour of Fe/Cr and Fe/Al systems by means of electrochemical and electron-optical techniques. Fe deposited with Cr (400A) and Al (800A) were bombarded by a N + ion beam with an energy of 150 keV at a dose of 5 × 10 16 N + /cm. The anodic current I c and I m , as displayed on anodic polarization curves for both Fe/Cr and Fe/Al systems, were decreased by one order of magnitude. It is mainly related with the chemical effect of N + ion implantation, and presumably associated with formation of a metastable phase of nitride as a barrier layer reducing the anodic dissolution.

Recycling of Electric Materials

Different technologies have been used for recycling of electrical materials. High quality AlNiCo permanent magnet with excellent magnetic properties was produced with remelted waste material by sophisticated technology. Reclamation of iridium deposited on ZrO2 by melting technology has been used to obtain high purity iridium available for crucible application. The beryllium scrap produced in the processing of beryllium powder was utilized to prepare a high strength, heat resistant and high conductive Cu-Co-Be alloy for electrodes in contact welding.

Optical total reflection and transmission with mode control in a dielectric subwavelength nanorod chain

We report a polarization dependent reflection phenomenon beyond the normal incidence with a subwavelength nanorod chain. Light waves of the transverse electric mode will be totally reflected while those of the transverse magnetic mode will transmit through. The total reflection or transmission phenomenon can be seen as a constructive or destructive interference of the incident field with the transverse mode field of the chain. With the low-loss feature and the ultra-compact characteristic, this structure may find applications in photonic circuits.

Formation of nanocrystalline TiN film by ion-beam-enhanced deposition

Abstract Nanocrystalline TiN thin films have been synthesized by ion-beam-enhanced deposition at room temperature. The effects of the ion species, energies and partial pressure of N 2 in the sample chamber on the grain size, lattice parameter and preferred orientation of the films were investigated. The formation of a nanocrystalline structure is attributed to the effect of local recrystallization in a collision cascade volume generated by incident ions.

The two-dimensional pair correlation function for the Si(001) surface: computer simulation results

A two-dimensional pair correlation function (TPCF) has been introduced into the study of the surface structure of materials. A molecular dynamics simulation was then performed to obtain the TPCFs for the Si(001) surface and deeper layers. The atoms interact via a potential developed by Stillinger and Weber, which includes both two-body and three-body contributions. The analysis of TPCFS shows that the atoms in deeper layers of Si(001) do not derive from their original (001) atomic plane lattice sites, but just thermally vibrate in the vicinity of their equilibrium sites, and the nearer to the surface layer the atoms are, the more violent the vibration is. The analysis also indicates that a rearrangement of atoms has occurred in the Si(001) surface and, while the majority of these atoms form bonds, a minority still exists as non-bonding atoms.

Computer simulation of SIMOX and SIMNI formed by low-energy ion implantation

Abstract The computer program IRIS (Implantation of Reactive Ions into Silicon) has been modified and used to simulate low energy (

Effects of flourine ion implantation on superconducting properties of YBa2Cu3O7-x

The effects of fluorine ion implantation on superconductivity in YBa2Cu3O7-x thin films have been studied using resistance measurements and X-ray diffraction patterns. Damage created by nuclear energy loss processes degrades both the transition temperature and the critical current density. However, the onset temperature and X-ray diffraction patterns almost remain the same until the critical fluence of 2.7×1013 ions/cm2. At low ion fluences, the data from measurements suggest that ion implantation does not destroy the superconducting property within granular cells, but destroyes the weak links between grain boundaries. At high ion fluences, the material goes continuously through the metal to semiconductor transition. At still higher fluences a crystalline to amorphous transition occurs, and the sample becomes insulator.

Stress behavior of TIN films formed by reactive ion-beam-assisted deposition

Abstract The effect of ion species and ion energy on the intrinsic stress in TiN films formed by reactive ion-beam-assisted deposition has been examined. The result shows that the stress changes from tensile to compressive and increases in magnitude with increasing ionic mass and ion energy. This stress annealing is considered to be momentum controlled.