Classical Cascade Calculations on the Analysis of Surface Bonding Structures by Secondary Particle Mass Spectrometry

The application of secondary particle mass spectrometry to analyze the atomic bonding configuration on a surface was investigated with computer calculations of particle sputtering from an Ar-bombarded surface of Ag{111}. In contrast to the prediction from the present sputtering theory, better resolved structure in the angular distribution was not observed for particles of high energy sputtered from the surface. These particles ejected to a wide angle and their angular distribution may not reflect well the atomic bonding geometry on the surface. The analytical capability of secondary particle mass spectrometry to determine surface structures can be significantly improved by selecting for detection only those particles that have prolonged collisions. The preferred directions of ejection and the relative sputtering intensity in the distribution of azimuthal angle between major open channels on the surface vary insignificantly with the duration of collision in the regime of long collisions. The results provide the first evidence that at small energies of sputtering the particles emitted from the surface may contain information about only the top two surface layers. Secondary particle mass spectrometry can thus be extremely surface sensitive for analysis of properties of solid surfaces.     

Secondary ion mass spectrometry for quantitative surface and in-depth analysis of materials

Secondary ion mass spectrometry (SIMS) is a technique based on the sputtering of material surfaces under primary ion bombardment. A fraction of the sputtered ions which largely originate from the top one or two atomic layers of the solid is extracted and passed into a mass spectrometer where they are separated according to their mass-to-charge ratios and subsequently detected. Because the sputter-yields of the individual species, coupled with their ionization probabilities, can be quite high and the mass spectrometers can be built with high efficiencies, the SIMS technique can provide an extremely high degree of surface sensitivity. Using a particular mode like static SIMS where a primary ion current is as low as 10^?11 amp, the erosion rate of the surface can be kept as low as 1 Å per hour and one can obtain the chemical information of the uppermost atomic layer of the target. The other mode like dynamic SIMS where the primary ion current is much higher can be employed for depth profiling of any chemical species within the target matrix, providing a very sensitive tool (～ 1 ppm down to ppb) for quantitative characterization of surfaces, thin films, superlattices, etc. The presence of molecular ions amongst the sputtered species makes this method particularly valuable in the study of molecular surfaces and molecular adsorbates. The range of peak-intensities in a typical SIMS spectrum spans about seven to eight orders of magnitude, showing its enormously high dynamic range; an advantage in addition to high sensitivity and high depth-resolution. Furthermore, the high sensitivity of SIMS to a very small amount of material implies that this technique is adaptable to microscopy, offering its imaging possibilities. By using this possibility in static SIMS or dynamic SIMS mode of analysis, one can obtain a two-dimensional (2D) surface mapping or a three-dimensional (3D) reconstruction of the elemental distribution, respectively within the target matrix. Secondary ion yields for elements can differ from matrix to matrix. These sensitivity variations pose serious limitations in quantifying SIMS data. Various methods like calibration curve approach, implantation standard method, use of relative sensitivity factor, etc. are presently employed for making quantitative SIMS analysis. The formation of secondary ions by ion bombardment of solids is relatively a complex process and theoretical research in this direction continues in understanding this process in general. The present paper briefly reviews the perspective of this subject in the field of materials analysis.     

The CuGaSe2(0 0 1) surface: A (4 × 1) reconstruction

We report on the formation of a stable (4 × 1) reconstruction of the chalcopyrite CuGaSe₂(0 0 1) surface. Using Ar⁺ ion-bombardment and annealing of epitaxial CuGaSe₂ films grown on GaAs(0 0 1) substrates it was possible to obtain flat, well-ordered surfaces showing a clear (4 × 1) reconstruction. The cleanliness and structure were analyzed in situ by AES and LEED. AES data suggest a slight Se-enrichment and Cu-depletion upon surface preparation. Our results demonstrate that (0 0 1) surfaces of the Cu-III-VI₂(0 0 1) material can show stable, unfacetted surfaces.     

双群模型在偏滤器材料溅射研究中的应用

为了估计偏滤器靶板材料的腐蚀速率和寿命，应用基于离子输运双群模型的溅射理论计算了聚变带电粒子H^ 、D^ 、T^ 和α粒子轰周Mo、W和Li偏滤器靶板表面的溅射产额，并与蒙特卡罗方法的计算结果作了比较。这些数据对估计对等离子体部件的寿命和堆芯等离子体中的杂质水平是有意义的。     

Er emission from Er-doped Si-rich silicon oxide layers synthesised by hydrogen reactive magnetron co-sputtering

Among the systems used as optical amplifiers, we propose an original way to elaborate photoluminescent materials. The method is based on the reactive RF magnetron co-sputtering of SiO₂ and Er₂O₃ controlled by the hydrogen dilution rate in the plasma gas. The relationship between the photoluminescence properties and the structural characteristics is evidenced through the variation of two parameters in the deposition process: the hydrogen partial pressure within the plasma and the sputtered surface ratio of Er₂O₃ and SiO₂ targets.     

Recent Developments and Applications in Unbalanced Mangnetron Sputtering

Sputtering deposition is one of the most important processes in the vacuum coating, it is widely used in microeletronics industries, optical films, and metallurgical coatings industry et al. Sputtering deposition is, in the vacuum conditions, sputtered particles from the target material deposit on the substrate using energetic ions to bombard surface of target to form a film.     

Preparation of YSZ films by magnetron sputtering for anode-supported SOFC

YSZ films for anode-supported SOFCs were prepared by reactive sputtering method. It was found that the surface morphology of anode substrate has a very important effect on the quality of sputtered films. By applying an anode functional layer and making the anode surface smooth, dense and uniform YSZ films of 10 µm in thickness were successfully fabricated. The sintering behaviors of the sputtered YSZ films were also discussed. It is suggested that the optimized densification condition for the deposited YSZ films is sintering at 1250 °C for 4 h. Single cells with sputtered YSZ film as electrolyte and LSM-YSZ as active cathode materials were tested. 1.08 V open circuit voltage and a 700 mW/cm² maximum power density were achieved at 750 °C by using humidified H₂ as fuel and air as oxidant.     

Influence of a single adatom on sputtering at grazing incidence - A molecular-dynamics case study of 5 keV Ar impact on Pt (1 1 1)

Grazing incidence ion impact on a flat terrace lets the projectile reflect specularly off the surface, leading to little or no damage production or sputtering. The presence of isolated surface defects may change this behaviour drastically. We investigate this phenomenon for the specific case of 5 keV Ar ions impinging at 83° towards the surface normal onto the Pt (1 1 1) surface. Molecular-dynamics simulations allow to study the influence of isolated adatoms in detail. The scattering of the projectile from the adatom can redirect the projectile, or let the adatom recoil, such that either of them deposits considerable energy in the target surface, leading to abundant damage production and sputtering. Two distinct collision zones are identified: (i) When the projectile hits the surface in front of the adatom, it may collide with the adatom indirectly (after being specularly reflected off the surface); (ii) alternatively, it may hit the adatom directly. We quantify our results by measuring the zone of influence (≅13 Å²) around the adatom, into which the projectile must hit in order to collide with the adatom, and by the sputter cross section of roughly . The data compare well with previous simulation results of sputtering from an atomically rough surface.     

Total reflection x-ray fluorescence as a sensitive analysis method for the investigation of sputtering processes

Angular distributions of sputtered germanium atoms during the grazing incidence of argon ions were investigated. Argon ion beams with angles of incidence of 75° and 80° and with ion energy of 20 keV were used in sputtering experiments. TXRF analysis showed to be an excellent method for measuring the angular distribution of sputtered atoms due to its low detection limit under total reflection conditions. The experimental data are compared to Monte-Carlo simulations. The observed differences are discussed, and suggestions for improving the Monte-Carlo simulation of ion sputtering are made.