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A new method for the preparation of sulfur (S) doped iron (Fe) samples is presented. The required amount of S in Fe is obtained by allowing the vaporized form of S to diffuse into a Fe sample (10 mm diameter, 0.5 mm thick) kept at a temperature of 750 K. Depth profile analysis using Auger Electron Spectroscopy and Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) showed that the method is reproducible and can be used for the preparation of samples with different S concentrations. It was also found that S deposited onto Fe forms the desired FeS phase, which will prevent S from evaporating when the sample is annealed. Prepared samples were annealed to obtain homogeneity of S in Fe, after which the amount of S in the respective samples was determined by quantitative TOF-SIMS. The outcome of the results suggests the application of this method to other high melting point host and low melting point dopant systems. Copyright © 2014 John Wiley & Sons, Ltd.

The important role of Auger electron spectroscopy (AES), X-ray photo electron spectroscopy (XPS) and time of flight secondary ion mass spectrometry (TOF-SIMS) to characterize different phosphor materials is pointed out with examples. AES is used to monitor surface reactions during electron bombardment and also to determine the elemental composition of the surfaces of the materials, while XPS and TOF-SIMS are used for the surface chemical composition and valence state of the dopants. Copyright © 2014 John Wiley & Sons, Ltd.

The surfaces of Ti and its alloys are always contaminated by O and C due to the continual uptake of the background gases, even in an ultra high vacuum (UHV) chamber. The surfaces of Ti and its alloys (Ti6Al4V and Ti3A18V6Cr4Zr4Mo) were cleaned by annealing the sample linearly to a temperature higher than 600 ° C and then cooled. The segregation of S was only observed after the samples were heated to temperatures above 550°C. The segregation of S was only measured after most of surface adsorbate elements were removed from the surface. The three samples' surfaces (Ti, Ti6Al4V and Ti3Al8V6Cr4Zr4Mo) were all almost clean or free of contamination in the temperature range 600-650 °C. The addition of the alloying elements impacts the retention of O and C on the surfaces. The linear least square (LLS) fit method was used to determine the contributions of pure Ti, Ti oxide and Ti carbide from the measured Auger peak to peak heights (APPHs). AES peak fitting was done and confirmed the formation of TiC and TiO on the surface at temperatures between 100 °C and 500 °C. The segregation of Al in the Ti6Al4V and Ti3Al8V6Cr4Zr4Mo samples was measured at higher temperatures.

The growth process of a gold thin film, in the sub-monolayer region, on a graphite substrate is studied by means of kinetic Monte Carlo simulations. Four different kinetic processes are considered, namely, atom deposition, diffusion, evaporation and island nucleation. Close attention is paid to the relationship between the substrate temperature, deposition rate and interaction between neighbouring atoms. The interaction potential between the gold atoms is described by the Sutton–Chen potential, while a modified Lennard-Jones potential is utilized for the gold–carbon interaction. The results indicate that the gold islands become more compact and dense at higher temperatures, whereas a more fractal growth pattern was observed at the lower-temperature regime. Conclusions are drawn on the dependence of the island shape and density on both the substrate temperature and deposition rate. Some reference is made to experimental results. Copyright © 2005 John Wiley & Sons, Ltd.

Field emission displays (FEDs) are a possible alternative to other display technologies. They work similar to cathode ray tubes, but instead of an electron gun they have an array of tiny metallic tips acting as electron emitters. This array is situated in close proximity to the phosphor screen and produces light by a process of cathodoluminescence (CL). During prolonged electron beam irradiation a non-luminescent ZnO layer forms on the irradiated surface of the ZnS phosphor powder. This is due to electron-beam-stimulated surface chemical reactions between the ZnS phosphor and water vapour present in the ultrahigh vacuum environment. The low-energy electrons used in FEDs have a shallow penetration depth and, because the CL is dependent upon the energy loss in the ZnS bulk itself, growth of the ZnO layer significantly degrades the CL intensity. Energy loss profiles in the ZnS for different ZnO thicknesses were determined using Monte-Carlo electron trajectory simulations. These profiles, along with photon absorption profiles, were used to determine a curve relating the normalized CL intensity to the ZnO thickness. It was compared with experimentally measured values obtained during CL degradation experiments on standard ZnS : Cu,Al,Au phosphor powders and ZnO thickness measurements with sputter depth profiling. Assuming the presence of a 20 nm thick diffusion interface between the ZnO layer and the ZnS bulk, the theoretical and experimental results agree well. Initially the interface represents the initial stages of oxidation, but after the oxide layer starts to grow as a uniform film it represents a physical interface formed due to diffusion processes.

The room-temperature oxidation of Fe(100), Fe(100)–3.5 wt.% MoN and a segregated MoN layer were compared with each other by using Auger electron spectroscopy. The linear least-squares method was applied successfully to the low-energy Fe AES peaks to obtain the fraction of metal and oxide as a function of oxygen exposure time. The backscattering term is, however, a function of the oxide coverage and an illogical decrease in the oxide thickness at higher exposures were measured. The high-energy Auger peak-to-peak heights of Fe were also used to calculated the oxide thickness at different exposure times and these oxide thickness values were used to calculate the backscattering term for the different oxides as a function of exposure time. The backscattering term for the segregated MoN layer on the Fe(100)–3.5 wt.%MoN specimen is a combination of the backscattering from MoN, the iron oxide and the substrate. The profile indicates how important the change in the backscattering term may be for accurate surface concentration calculations. The backscattering terms for the Fe(100) and Fe(100)−3.5 wt.% MoN decrease exponentially with an increase in the oxygen exposure, which is in direct correlation with the logarithmic growth law of the oxides on the samples. Copyright © 2002 John Wiley & Sons, Ltd.

During electron beam irradiation of ZnS phosphor powders, a non-luminescent ZnO layer is formed on the powder due to electron-beam-stimulated surface reactions. As the thickness of the oxide layer increases, the energy loss in the ZnS bulk decreases with a subsequent degradation in cathodoluminescence. Using the Monte Carlo technique, the trajectories of low-energy electrons were simulated in a ZnS phosphor powder with a ZnO overlayer of varying thickness based on recent models describing the energy loss and scattering angles of low-energy electrons in a solid. A diffusion interface between the ZnO layer and ZnS bulk was simulated by varying the concentration of O and S atoms in the interface. Modelling the interface in this way describes the electron trajectories and energy loss in the interface region, because a sharp interface between two dissimilar layers very seldom exists. In the energy-loss profiles the transition between ZnO and ZnS corresponds to a sharp increase in energy loss due to the increased rate of energy loss of electrons in ZnS. The diffusion interface has a smoothing effect on this sudden increase. From the electron trajectory data and corresponding energy loss, energy loss profiles were determined indicating the cumulative distribution of all the electron energy losses as a function of the interaction volume depth and thickness of the ZnO layer. When a distribution of incident angles is used, the profile differs from the typical energy-loss profile seen at normal incident angles. As the thickness of the ZnO layer increases, the total energy loss in the solid decreases due to the increase in the backscattering coefficient of electrons in ZnO.

The changes in cathodoluminescent brightness and changes in the surface chemistry of ZnS:Cu,Al,Au have been investigated using Auger electron spectroscopy (AES) and a photospectrometer. The ZnS:Cu,Al,Au phosphor powders have been subjected to electron beam bombardment of 2 keV, with an electron beam current density of 88 mA cm -2 at an oxygen pressure of 2 X 10 -6 Torr. The studies were carried out between room temperature and 310 °C. Degradation was manifested by a non-luminescent ZnO layer that formed on the surface of the phosphor according to the electron-stimulated surface chemical reaction (ESSCR) mechanism. An increase in temperature led to a decrease in the surface reaction rate due to a decrease in the mean surface lifetime of the oxygen molecules on the surface, with a direct decrease in the ESSCR probability. Without the presence of the electron beam, no chemical reactions occurred on the surface up to 310 °C. Local heating due to the electron beam irradiation is not responsible for the chemical reactions on the ZnS phosphor surface.

Surface reactions occur on the ZnS:Cu,Al,Au surface during prolonged electron bombardment forming a non-luminescent ZnO layer with consequent loss in cathodoluminescence (CL) intensity. The layer is formed according to the electron-stimulated surface chemical reaction (ESSCR) mechanism. There is a direct correlation between the power emitted as luminescence and the energy loss of the electron beam. The electron energy loss within the ZnS was determined by using the Monte Carlo algorithm CASINO, which is a publicly available code. By determining the energy loss, the influence of a non-luminescent ZnO layer of varying thickness on a ZnS substrate on the CL intensity was simulated. These results were compared also with previous calculations that were based on the results of experiments done on the transmission of electrons through thin films. The energy loss within the ZnS as function of the ZnO thickness was determined at beam voltages of 1, 2 and 5 keV. The results obtained correlate with experimental CL measurements of the phosphor degradation during electron bombardment.

Thin film diffusion studies often involve a surface-sensitive analysis technique combined with ion erosion to produce a depth profile of a sample. Such studies compare the depth profile of a reference sample to the depth profiles of samples that were annealed at different temperatures and times. The extent to which atoms of one layer diffuse into an adjacent layer, for a particular temperature and time, yields information on the diffusion process involved and allows quantification of the diffusion coefficient. The drawback to using an erosion-type system is the effect of the incident ions on the surface being probed. The Mixing-Roughness-Information model attempts to compensate for this effect and is often employed as a means of quantification of measured depth profiles by means of profile reconstruction. Used in conjunction with Auger electron spectroscopy, the Mixing-Roughness-Information (MRI) model is a useful tool to reconstruct the ion erosion depth profiles as well as extracting interdiffusion parameters from these depth profiles. This study focuses on the extraction of the diffusion coefficient of Ni in Cu from Ni/Cu depth profiles obtained from ion erosion Auger electron spectroscopy. The resultant depth profiles were reconstructed with the MRI model. The diffusion coefficient for Ni diffusing in Cu was obtained from the MRI fit and it compared well to values available in literature.

During electron beam irradiation of ZnS phosphor powders, a non-luminescent ZnO layer is formed on the powder due to electron-beam-stimulated surface reactions. As the thickness of the oxide layer increases, the energy loss in the ZnS bulk decreases with a subsequent degradation in cathodoluminescence (CL). Owing to the morphology of the phosphor powder, growth of the oxide layer leads to varying effective ZnO thicknesses. In this paper the effect of the interaction between the electron beam and the ZnO/ZnS powder particles on the energy loss in the ZnS is studied using Monte Carlo simulation techniques. In the simulation, an electron beam with a certain profile is spread according to a Gaussian distribution function over the phosphor particles. These particles consists of both flat and spherical-shaped grains. The incident angle between the electron beam and the particle's surface is determined by using simple vector analysis. If the beam contains a sufficient number of electrons, a distribution of incident angles can be obtained. It was found that this distribution is independent upon the profile of the electron beam as long as the full width at half-maximum (FWHM) beam diameter is larger than the size of the irradiated particles. Using these results a comparison was made between the energy loss in the ZnS particles as a function of the ZnO thickness with and without the angular distribution. A publicly available Monte Carlo code for electron trajectory simulations in solids, called CASINO, was used for this purpose. When the distribution is considered, there is a decreased energy loss in the ZnS bulk. Because the light generation during electron beam irradiation is proportional to this energy loss, the morphology of the phosphor powder also contributes to the CL degradation. Copyright © 2000 John Wiley & Sons, Ltd.

The degradation of cathodoluminescent brightness under prolonged electron beam excitation of phosphors has been identified as one of the outstanding critical issues for the flat-panel field emission industries. The ZnS : Cu,Al,Au phosphor powders have been subjected to electron beam bombardment of 2 keV with different electron beam current densities (2.5-88 mA cm -2 ) at an oxygen pressure of 1 × 10 -6 Torr. Auger electron spectroscopy (AES) and cathodoluminescence, both excited by the same electron beam, were used to monitor changes in surface composition and luminous efficiency during electron bombardment. Degradation was manifested by a non-luminescent ZnO layer that formed on the surface of the phosphor according to electron-stimulated surface chemical reaction (ESSCR). Lower current densities lead to a higher surface reaction rate, due to a lower local temperature beneath the beam, which resulted in more severe cathodoluminescence degradation. A lower temperature beneath the electron beam may lead to an increase in the surface reaction rate due to the longer time spent by the adsorbed molecules on the surface, with a direct increase in the ESSCR probability.

A 2000 A layer of Tb followed by a 200 A layer of Si was deposited onto an SiO2 substrate. The samples were annealed from 480°C for 4 min to 800°C for 120 min in a high vacuum (p⩽2×10−7 Torr). It was inferred from Auger depth profiles and peak shapes that the reaction between Tb and SiO2 starts by the dissociation of SiO2 at the Tb/SiO2 interface. The released oxygen diffuses into the deposited Tb, forming a Tb–O solid solution. Terbium silicide initially forms at the Tb/SiO2 interface. After annealing for 25 min at 480°C, terbium oxide started to grow next to the SiO2 substrate. After annealing for 80 min at 480°C, the oxide/silicide (with oxygen)/oxide layers were well separated on the SiO2 substrate. Annealing at 600°C for 16 min and at 800°C for 120 min resulted in an additional layer that formed next to the SiO2, which consists of Tb, Si and oxygen. We assume that this layer is the beginning of the formation of another silicide layer with embedded oxygen in the layer. The sample eventually consists of SiO2(substrate)/silicide (with oxygen)/metal oxide/silicide (with oxygen)/metal oxide. The metal oxides contain an Si concentration of

The phosphor powder ZnS:Cu,Al,Au has been investigated extensively as a possible green phosphor for field emission displays (FEDs). Phosphor powders of ZnS:Cu,Al,Au have been subjected to electron bombardment (1–5 keV) at oxygen pressures ranging from 1×10−7 to 2×10−6 Torr and different electron current densities (45–58 mA cm−2). Auger electron spectroscopy (AES) and cathodoluminescence (CL), both excited by the same electron beam, were used to monitor changes in surface composition and luminous efficiency during electron bombardment. It was shown that the degradation rate of the CL intensity is a linear function of oxygen pressure. The interactive constant (a measure of the probability of surface reactions) and the burning parameter (a measure of the probability of CL degradation per incident electron) plotted as a function of electron beam energy follow the same trend as the electron impact ionization cross-section for an atom. © 1998 John Wiley & Sons, Ltd.