Stages of surface erosion under ion irradiation

Initial stages of surface erosion have been studied for NaCl and LiF single crystals bombarded by Ar⁺ ions with 20 keV. For irradiation with doses D=10¹⁰-10¹¹ ions/cm², exoelectron emission has been used, whereas for higher doses, we have used electron microscopy. Two stages of initial surface erosion have been identified; for small doses, there is slow development of atomic-scale roughening, which reaches its peak when areas damaged by closest incident ions start to overlap, and then, beginning with D=10¹⁶ ions/cm², there is rapid etching, deep into the crystal, followed by the emergence of secondary microscopic structure, i.e. caverns, concentric closed steps and terraces. Ion-induced surface structure of alkali halide crystals has been shown to depend strongly on the presence of foreign particles on the surface, as well as on segregation. Topography of thin carbon films and some metals have been discussed.     

Secondary ion emission from Ti and Si targets induced by medium energy Ar ion bombardment - Experiment and computer simulation

The paper presents experimental results of secondary ion energy distributions obtained for Ti and Si targets bombarded by 20-30 keV monoisotope Ar⁺ ion beam. The influence of the extraction voltages between target and a slit of the electrostatic energy analyzer entrance on the energy distributions of secondary ions was investigated. After optimization of the secondary ion extraction system, the mass spectra of secondary ions were also measured. The investigations were done using recently built experimental system. Experimental data are compared with the computer simulation results obtained using TRQR and SATVAL codes.     

Thin film deposition on a corrugated surface: A molecular dynamics approach

This paper presents the use of molecular dynamics (MD) simulation in the investigation of the surface topography of early-stage film growth on a GMR (giant-magnetoresistance) corrugated structure. The size of the simulated system is limited in order to reduce the computational workload. The numerical model adopts the Morse potential and the Verlet-leapfrog time evolution scheme [R.W. Hockney, 1970; D. Potter, 1972 (Chapter 5). [1]] to describe the atomic interactions which take place between the atoms. The impact energy transferred from the incident atoms to the substrate is modeled by rescaling the atoms within the upper substrate layers. It is found that the important properties of the film-substrate system may be obtained after the deposition of just several atomic layers. The influence of the impact velocity upon the coating parameters is investigated by varying the incident energy of the deposited atoms. The current results indicate that the surface coverage is poor, when atoms are deposited at low incident energies upon a low temperature substrate. At a higher incident energy, the deposited film tends to exhibit a quasi-layer-by-layer growth mechanism, which results in an improved surface coverage. Finally, it is demonstrated that a distinct quasi-fluid behavior is evident on the substrate when the atoms are deposited at high incident energies.     

光信息存储与溅射靶材

在光盘制造过程中，需要使用多种溅射靶材。本文简介溅射靶材的制造及主要应用情况。     

Self-aligned fabrication of single crystal diamond gated field emitter array

This paper describes a self-aligned fabrication process for diamond gated field emitter array (FEA). Utilizing the non-conformal coverage sputtering conditions of silicon oxide, an interesting “sphere on cone” structure is formed on diamond nano tip array, which is the key point of gate hole opening process. This structure causes shadowing at certain regions of side-wall during Ti / Au gate metal deposition. Removal of “sphere” by wet etching leads to the successful fabrication of a single crystalline diamond gated FEA. Scanning electron microscope observations reveal the fabrication of a uniform emitter array with tip radius of curvature (20 nm) and gate hole (1.4 μm). We also confirmed that no noticeable physical damage exists on tip. In field emission characteristics of the fabricated single crystal diamond gated FEA, gate voltage control of field emission current is realized.     

Optimization of the sputter-deposited platinum cathode for a direct methanol fuel cell

The electrodes prepared by a sputtering method were evaluated as the cathodes for direct methanol fuel cells (DMFCs). Pt loading below 0.25 mg cm⁻² achieved higher mass activities than that of 0.5 mg cm⁻² prepared by the paste method, which was general conventional method. However, an increase in Pt loading reduced the catalyst activity for the oxygen reduction reaction (ORR). This result may suggest an increase in only electrochemically inactive Pt. Pt utilization efficiency can be found about ten times higher at Pt loading of 0.04 mg cm⁻². Moreover, addition of Nafion to sputter-deposited Pt cathodes is found possible to improve the catalyst activity for the ORR, but the excess Nafion over the optimum condition reduces the active sites.     

氮掺杂二氧化钛的制备及可见光催化研究进展

TiO2在紫外光下具有优异的光催化性能，在废水处理、空气净化、抗茵等环保领域有着广泛的应用，但实现其可见光催化一直是研究的难点之一，而氮掺杂TiO2可以实现可见光催化，本文详细介绍了氮掺杂TiO2的制备方法、研究现状和可见光催化的应用情况，并对未来的发展趋势作了预测。     

Growth of La2Mo2O9 films on porous Al2O3 substrates by radio frequency magnetron sputtering

Synthesis conditions of La₂Mo₂O₉ thin film by radio frequency (RF) sputtering technique on Al₂O₃ ceramic substrates are studied. It is found that the deposition temperature and oxygen partial pressure are the most important factors for obtaining pure La₂Mo₂O₉ films. Varying both parameters, Mo-rich, stoichiometric, and Mo-deficient films are obtained. With increasing the La:Mo ratio, films become denser. A crust layer is observed on top of the Mo-rich and the Mo-deficient films. The formation of the La₂Mo₂O₉ phase is discussed with respect to the sputtering mechanism.     

Effect of substrate rotation on structure, hardness and adhesion of magnetron sputtered TiB2 coating on high speed steel

Titanium diboride (TiB₂) coatings have been deposited on stationary and rotating high speed steel substrates by magnetron sputtering of a TiB₂ target. The structure and hardness of the coatings and the coating–substrate adhesion have been investigated by X-ray diffraction, field emission scanning electron microscopy, nanoindentation and microscratch tests. The results show that substrate rotation has a significant effect on these structural and properties features. It was found that, with substrate rotation, the TiB₂ coating exhibits a columnar structure with random orientation and relatively low hardness and coating–substrate adhesion. On the other hand, without substrate rotation, the TiB₂ coating shows a strong (001) texture with dense, equiaxed grain structure. The hardness and coating–substrate adhesion of the coatings deposited on stationary substrates are much higher than those deposited on rotating substrates. The observed phenomena are discussed in terms of the energy of the sputtered flux, which varies with the substrate–target distance during deposition.     

Magnetic properties and microstructure of FePt–SiO2 nanocomposite films fabricated by nanocluster beam technology

Nanocluster beam technology combined with conventional sputtering was used to fabricate FePt–SiO₂ nanocomposite films in this present work. The post-deposition annealing affected the final particle size and size distribution of FePt nanoclusters. The effects of both volume fraction of SiO₂ matrix and annealing temperature on magnetic and microstructural properties were studied. Partial ordering, grain growth and agglomeration of FePt particles in FePt–SiO₂ nanocomposite films occurred during annealing. A higher volume fraction of SiO₂ matrix was effective in suppressing diffusion of atoms and magnetic exchange coupling of FePt grains. Excessive SiO₂ however resulted in a lower degree of FePt ordering and thus lower coercivity.