The damage and the in-depth distributions of Argon atoms or Oxygen atoms in Si(100) surface after Ar⁺ or O₂⁺ ion beam sputtering were investigated by using Medium Energy Ion Scattering Spectroscopy and Dynamic Monte Carlo simulation. The primary ion energy was 0.5 keV and the primary ion beam direction was varied from surface normal to glancing angle. It was observed that the damage layer can be minimized with 0.5 keV O₂⁺ and Ar⁺ ion bombardments at the incident angle of 80° from surface normal. In the case of 0.5 keV Ar⁺ ion beam sputtering at the surface normal incidence, the maximum atomic concentration of Ar atoms was 6 at% at the depth of 2 nm, while at the incident angle of 80°, the in-depth Ar distribution cannot be observed. In the case of 0.5 keV O₂⁺ ion beam sputtering at surface normal incidence, the surface is continuously swelled to ～1.5×10¹⁶ O₂⁺ ions cm^-2 ion dose owing to an incorporation rate of oxygen higher than the sputtering rate of Si. Dynamic Monte Carlo simulation reproduced the in-depth concentration distribution of Ar atoms and Oxygen atoms, quantitatively.

  It is well known that the usual procedure for quantification by electron spectroscopy that is based on measured peak intensities is highly unreliable. An improved method is to take into account that the peak shape in a wide energy range, on the low kinetic energy side of the peak varies considerably with the surface morphology on the nano-meter depth scale. This observation has in recent years been applied in the formulation of a by now well known method for quantification that is based on quantitative analysis of measured peak shapes. The technique is sensitive on the 1 - 10 nm depth scale and it is non-destructive. The method suggested for the extraction of quantitative information from the large variation of the inelastic background with atom depth distribution will be reviewed briefly here. An example of practical application of the technique is also shown.

  A new method for the combination analysis of high-resolution Rutherford backscattering spectroscopy (HRBS) and angle-resolved X-ray photoelectron spectroscopy (AR-XPS) is proposed for accurate depth profiling of chemical states. In this method, attenuation lengths (ALs) for the photoelectrons are first determined so that the AR-XPS result is consistent with the HRBS result. Depth profiling of the chemical states are then performed in the AR-XPS analysis using the compositional depth profiles obtained by HRBS as constrained conditions. This method is successfully applied to a hafnium-based gate stack structure demonstrating its feasibility.

  In-depth distribution of doping elements in shallow depth region is an important role of secondary ion mass spectrometry (SIMS) for the development of next-generation semiconductor devices. KRISS has developed two types of multi-layer reference materials by ion beam sputter deposition. A multiple delta-layer reference material where the layers of one element are very thin can be used to evaluate SIMS depth resolution, to calibrate the depth scale and to monitor sputtering uniformity. The scale of a stylus profilometer can be also calibrated by comparison of the crater depths measured by a stylus profilometer and the certified thickness of the reference material measured by high resolution TEM. In a Korean round robin test for the scale calibration of a stylus profilometer using a Si/Ge multiple delta-layer (MDL), the average slope of the linear fitting results between the measured depth and the nominal depth was 0.989 with the standard deviation of 0.05. In depth scale calibration using a Si/Ge multi-layer reference material showed that the determination of interface position is very important to calibrate the sputtering rates of two different constituent materials. Especially, it is critical to define the positions of interfaces in a SIMS depth profile with interface artifacts.

  Several oblique cutting methods, including a recently developed gradient shaving preparation, for sample pretreatments have been developed. The combination of the above pretreatment method and time-of-flight secondary ion mass spectrometry provides very useful depth-profiling information in the analysis of organic materials for practical use. In this report, some results measured by combinations of the several oblique cutting methods and ToF-SIMS measurements are introduced.

  Depth profiling of model organic thin films composed of Alq₃ and α-NPD on ITO-covered glass has been performed by Ar⁺ or C₆₀⁺⁺ ion sputter. In the case of conventional 2keV-Ar⁺ ion sputter, as a result of the severe damage there are no peaks characteristic of their molecular structure, and a specific elemental ion of Al⁺ is the only sign of Alq₃. Al⁺ profiles of Alq₃ with different thickness show a constant sputtering yield. On the other hand, we can observe the survival of C₁₈H₁₂N₂O₂Al⁺ (Alq₂⁺) by use of 20 keV-C₆₀⁺⁺ cluster ion sputter. However, Alq₃ films show the quite dose-dependent sputtering yields. The dose dependency is caused by the accumulation of the sample damage, which is represented by the increase of C⁺ and C₂⁺. The intensities of low mass fragment ions can be available as an index of the accumulating sample damage.

  ISO / TC201 (Surface Chemical Analysis) / SC4 is the subcommittee to work for standardization in depth profiling. The standard drafts of ISO 14606, TR 15969, and TR 22335 have been published in order to achieve a good depth resolution, to estimate a sputtered depth, and to convert a sputtering time to the sputtered depth by a sputtering rate. ISO/TC201/SC4 is also working to prepare new work items on “ion beam alignment” and “utilization of standard multiple layers”.

  We have investigated the high depth resolution Auger depth profiling using an inclined holder. The developed inclined holder enables the very shallow incident angle of argon ion for sputtering to be used. In consequence, depth profiles of Ga LMM and Al KLL from a GaAs/AlAs multilayer specimen showed a much better depth resolution compared to those obtained by the conventional method. We also measured the Auger depth profiles of a Si/Ge multiple delta-layer specimen using the inclined holder and confirmed. A Ge mono-layer can be profiled.

  As fundamental importance to SEM observation of specimen surface, secondary electron generation and emission processes have been studied by a Monte Carlo method. The simulation is based on a discrete description of cascade secondary electron production. The Monte Carlo model combines the use of Mott’s cross section for electron elastic scattering and of Penn’s dielectric function for electron inelastic scattering. Two models of dielectric function, i.e. the single pole approximation and the full Penn algorithm, are shown to give energy distribution and yield of secondary electrons in agreement with experimental results for non-free electron materials and free electron metals, respectively. We use a constructive solid geometry modeling to describe sample 3D geometry and a Gaussian function to describe random surface roughness. The technique is efficient and powerful in a simulation of SEM images of secondary electrons and backscattered electrons for a quite complex geometry of nanostructures. Finally we present the depth distribution functions for secondary electron generation and emission. Their dependences on primary energy and atomic numbers are analyzed. Furthermore, we shall also discuss a general issue of depth distribution function for rough surfaces.

  It is well-known that angle-resolved X-ray photoelectron spectroscopy (AR-XPS) is a powerful tool for the nondestructive depth profiling of nanometer-scaled thin layers. Recently, high energy XPS (HX-XPS) using hard X-rays reveals the deeper layers up to 20 nm, and enables to clarify the electronic structure and chemical reaction in the nano-materials. Combination of AR-XPS and HX-XPS is going to be a frontier of the analysis of practical nano-devices of which working depth is several tens of nanometer. Emission Depth Distribution Function (EDDF) is a fundamental function for the quantitative nondestructive depth-profiling by using AR-XPS and HX-XPS. We evaluated the EDDF of HX-XPS by the angle-resolved and photon-energy-resolved XPS analysis for Ni 1s photoelectrons excited by synchrotron radiation (SR) linearly-polarized X-rays from 8.5 keV to 14 keV.

  It has been shown, in recent reports, that the backscattering factor (BF) in AES noticeably depends on the in-depth structure of the surface region. Consequently, the signal intensity due to an analyzed element in sputter depth profiling experiments cannot be described with a single BF value. The BF depends on the removed amount of the material and thus varies with time of sputtering. This effect is illustrated here on the example of the thin Ni layer buried in the Au matrix at different depths. The algorithms for calculating the BF for a thin layer of analyzed material are briefly discussed.

  The application of XPS for film thickness analyses of overlayer thin films, the structure analysis of multilayered thin films, the background shape analyses of thin films of varying depth distributions and the compositional depth profiling by ARXPS utilizing the maximum entropy method are described. The destructive depth profiling of organic thin films (such as ～100 nm in thickness) by cluster ion beams is also described. The film thickness analysis is applied for samples such as the oxide thickness distribution on 200 mm silicon wafers. The structure analysis has a great opportunity for applications on chemically modified surfaces. The background shape analysis is useful for both homogeneous and structured thin films. The MEM applied to ARXPS data is also useful for structured analysis for such as SiON thin films. However both background shape analysis and MEM need optimizations of the parameters using prior information about the films. On the other hand, depth profiling of organic thin films in 100 nm order thickness is successfully applied with 10 keV C₆₀ ion beam sputtering and with 0.2 keV Ar ion beam and 10 keV C₆₀ ion beam co-sputtering.

  My group has recently been engaged in the following research work on the nanoscale materials by using XPS:

  X-ray photoelectron spectroscopy (XPS) is known to examine a chemical state analysis. Generally chemical shift can evaluate the valence number of atom and a chemical bond of compound. The analysis of the reference material is important as chemical analysis. In many cases general reagent cannot be used as the reference material of the surface analysis. An irregular example is important for a database.

  Silicon sub-oxide (SiO) is an interesting state of chemistry when the process of the initial oxidization of Si is investigated. There is a SiO reagent as form of powder or grain. However, a commercial reagent of SiO doesn't show an independent XPS peak. The spectrum is similar to a mixture of SiO₂ and Si. This study shows spectra of Si and SiO powder sample for some preparation and measurement by XPS. And XAES spectrum by the high-energy X-rays of Zr anode (Zr-Lα:2042.4eV) and the Bremsstrahlung X-rays of Mg anode are shown.

  In this study, we demonstrate low damage etching of polymer materials for depth profile analysis by using large Ar cluster ion beams. Recently, we have proposed to use keV-energy large cluster ions as primary ions for secondary ion mass spectrometry (SIMS). The intensities of molecular ions from the polymer films were kept constant after etching with large Ar cluster ions, though the primary ion fluence exceeded the static limit. These results prove that large cluster ion beam irradiation rarely leads to damage accumulation on the surface of the polymers, and these characteristics as etching beam could be also suitable for other depth profiling techniques. In addition, the surface chemical states of the polymers were measured with X-ray photoelectron spectrometry (XPS). The chemical states of the polymethyl methacrylate (PMMA) sample etched with Ar atomic ion beams differed significantly from those of the untreated sample, whereas the chemical states were maintained even after etching with large Ar cluster ion beams.

  Recently, we have developed the probe electrospray ionization (PESI) that uses the solid needle. In this system, the probe needle moves up and down along the vertical axis by a motor-driven system. At the highest position of the probe needle, electrospray is generated by applying the high voltage. In this study, we used PESI directly to the biological samples such as urine, mouse brain, mouse liver, salmon egg, artificial salmon egg, and fruits (orange, banana, etc.). Strong ion signals for almost all the samples were obtained. The amount of liquid sample picked up by the needle is as small as pL or less, making the PESI the most promising non-invasive technique for detecting biomolecules in a living systems such as cells. Therefore, PESI may be useful as versatile and ready-to-use semi-on line analyses in the fields of surface chemistry, medicine, pharmaceutical, agriculture, food science, etc.

  The molecular depth profiling of polymer by the electrospray droplet impact (EDI) have been performed. The multiply-charged water droplets with kinetic energy of ～10⁶eV were irradiated to a bulk and a spin coated polymer samples. The synthetic polymer as bulk polystyrene (PS) and spin coated PS on Si substrate were adopted as typical polymers. When a target is etched by EDI, the ablation of the target is suppressed to minimal, i.e. the shallow surface etching with non-recognizable damage on the surface is realized. It was found that X-ray photoelectron spectroscopy (XPS) spectra for PS were independent on the irradiation time by EDI. This indicates that EDI is a unique technique for the surface etching of the polymer materials without leaving any damage on the etched surface.

  Sputter depth profiling of inorganic materials using X-ray Photoelectron Spectrocopy (XPS) has become a standard analytical technique. Generally the quantitative elemental and chemical depth distribution of species can be obtained from the sample surface to several microns into the sample relatively quickly with good interface resolution. It is obviously desirable to achieve the same performance on organic materials, however, there are several well known problems associated with sputter depth profiling of organics which has limited its application. The Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) community have pioneered the use of polyatomic ion sources (in particular C₆₀) to increase ion yields from organic materials. This use of C₆₀ has been extended to XPS depth profiling and for some materials has shown good results. This paper discusses the characterization and optimization of another polyatomic species that is showing considerable promise for XPS depth profiling of organic materials.

  Angle resolved XPS is a useful method for obtaining non-destructive quantification of thin (4-6nm) layers with good absolute depth resolution. Although acquisition of ARXPS data with modern instrumentation is easy, determining the depth distribution of elements from the data is more challenging. The maximum entropy method (MEM) is a technique frequently used for solving the inversion problem in angle resolved XPS experiments. The necessary condition for the consistency of experimentally measured data with the MEM model (successful fit) is that the Laplace transform of the compositional depth profile (LTCDP) calculated from the experimentally measured normalised intensity is a monotonically decreasing function for all measured elements. We have found an efficient algorithm which can estimate the LTCDP for elements with attenuation lengths and provide an independent test of the suitability of the layered model for different sample elements. The practical application of this method is illustrated on analysis of a number of samples and conclusions on the use of these methods to generate elemental and chemical-state depth profiles are discussed.

  Alloying elements added to steel for improving surface properties such as corrosion resistance exhibit different chemical characters, and they are often enriched to the surface of the alloys or oxidized there during annealing at high temperatures. In this study, depth-resolved X-ray absorption spectroscopy (XAS) measurements were carried out using a two-dimensional detector with geometrical arrangement of grazing exit in detection of fluorescence X-ray emitted from sample surface, in order to characterize the enrichment and oxidation of manganese on the surface layers of an Fe-Mn alloy annealed under low oxygen partial pressure. This technique facilitates non-destructive measurement for characterizing the compositional distribution and the oxidation state of manganese in the depth direction. The results showed that manganese was enriched to surface layers of the Fe-Mn alloys during annealing at high temperatures and formed as manganese oxide. The preferential oxidation of manganese by annealing under low oxygen partial pressure is considered the driving force for their enrichment on the alloy surface.

  We have investigated chemical-state-resolved in-depth profiles of HfO₂/SiO_x and HfSiO/SiO_xN_y films using angular-dependent photoemission spectroscopy and Maximum-entropy method. Maximum-entropy method enables to reproduce the stack structure from angular-dependence of core-level spectra and it is utilized to determine atomic concentration of the interfacial layer. For the HfO₂/SiO_x film, it is elucidated that the Si⁺ and Si²⁺ sub-oxide components are located in the vicinity of Si substrate and Si³⁺ is distributed around the interfacial layer. In addition, annealing-temperature dependence of in-depth profile for the HfSiO₂/SiO_xN_y film have been demonstrated, which reveals that Si oxide components diffuse from the interfacial SiO_xN_y layer into the HfSiO layer during annealing.

  In order to study correlation between oxide layers on hydrogen storage metals such as V(111), polycrystalline Vanadium, and VCrTa alloy and hydrogen desorption temperature, the surfaces covered by native oxides have been analyzed by photoemission spectroscopy using soft x-ray synchrotron radiation. Depth analyses of the oxide layers were performed by changing synchrotron radiation energy to estimate the oxide thickness. The native oxide layer was disappeared by thermal annealing up to 713 K for the V(111) surface. The oxide layers of the poly V and the VCrTa alloy, however, were remained even at 873 K. Although the oxides of V and Cr were disappeared, Ta oxides were remained. The re-arrangement of oxidation took place in the oxide layer of the VCrTa alloy by thermal annealing. The oxidation of Ta controlled oxide thickness in the VCrTa alloy. The formation of an artificial oxide layer could be controlled using supersonic oxygen molecular beams.

  The depth profiling of perhydoropolysilazane(PHPS) thin films on Si wafers were investigated by multi anode x-ray photoelectron spectroscopy (XPS) which has four x-ray anodes such as Mg, Zr, Ag and Ti . As the excitation energy of x-ray become higher, the information depth is more deepened. So it is possible to non-destructive depth profiling analysis of PHPS films by using multi anode XPS. It was found that the PHPS films to convert to silica occur not only on surface but also in sample inside by means of thermal treatment.

  We have described the electron backscattering correction for Auger analysis. Ichimura-Shimizu equation has been frequently used for this correction, but has limitations for incident electron energies and angles. Then, we have proposed an improved correction for the backscattering correction that could be applied to the wide analytical conditions based on the Ichimura-Shimizu equation.

  The emission depth distribution functions of photoelectrons for copper oxide CuO and silicon dioxide SiO₂ were calculated by the use of the first-principle quantum mechanical multiple scattering theory. The results were compared with the approximated analytical expressions from the Boltzmann equation by Tilinin et al.. The former explicitly takes the details of atomic arrangement in solids into account, while the latter does not. We show the calculated results by the use of two approaches and how the elastic scatterings affect the depth distribution function.

  Inelastic scattering cross sections of Si in the form of λK(ΔE), the production of the inelastic mean free path and the inelastic scattering cross section, were obtained from the angular dependent reflection electron energy loss spectroscopy (REELS) spectra. The REELS spectra with the energy and angular dependence were measured using an inclined sample holder. The spectra were taken for the primary beam energy from 500 to 4500 eV at a fixed incidence angle and various emission angles. For each primary energy, a series of ten λK(ΔE) spectra were obtained. The experimental λK(ΔE) spectra obtained from the angular dependent REELS spectra were compared in absolute unit. It clearly showed the variation in the relative contribution of bulk and surface losses in these series of the λK(ΔE) spectra after subtracting the multiple scattering. It allowed separating the surface and bulk loss contribution based on the changing of the emission angles.

  The secondary electron spectra from the Si (111) surface induced by irradiation of Xe⁺ ions of 300 eV were measured as functions of oxygen exposure time. The intensity of ion-induced secondary electrons decreased with the increase of oxygen exposure time for Xe⁺ irradiation, while the intensity of electron-induced secondary electrons increased. The atomic force microscopy (AFM) observation supported that the decrement of the peak intensity and the peak energy of the ion-induced secondary electron spectra are originated from the surface roughening enhanced by oxidation. This suggests that the ion-induced secondary electron spectroscopy can be applied for the real-time monitoring of the surface roughening during ion sputtering as a complementary method to AFM or scanning tunneling microscopy.

  Influences of measurement conditions such as the base pressure of the analysis chamber, the acquisition time of Auger electron spectroscopy (AES) and the sputtering time in one period, on AES sputter depth profiling of a GaAs/AlAs superlattice reference material were investigated by irradiating 750 eV Ar⁺ ions at the incident angle of 50°. The results revealed that the ratio of the etching rate of AlAs to that of GaAs is strongly influenced by the base pressure of the analysis chamber. When the base pressure is ～2×10^-9 Torr, the ratio of the etching rate is almost constant at ～0.9 and not affected by measurement conditions. In contrast, when the base pressure is ～8×10^-9 Torr, the ratio of the etching rate is strongly affected by measurement conditions. The shorter the sputtering time in one period is, the smaller the ratio of the etching rate is. The longer acquisition time of AES is also considered to introduce the difference in the ratio of the etching rate. The influences on the etching rate caused by the measurement conditions might be attributed to the oxygen adsorption on the AlAs surface. In addition, in spite of the strong dependence of the ratio of the etching rate on the measurement condition at the base pressure of ～8×10^-9 Torr, the depth resolution does not depend on the measurement condition. The present results strongly suggest that careful attention for the optimization of the measurement condition of sputter depth profiling using the GaAs/AlAs superlattice reference material is required since the etching rate is an important factor to quantitatively understand the depth scale of depth profiles.

  The in-situ observation of the reaction between iron and carbon in TEM was carried out. The contact between iron and carbon was realized utilizing the carbon deposition on the surface of iron and FIB enabled to prepare TEM specimens. The reaction occurred beyond 773K as the precipitation from the boundary between iron and carbon and the precipitates grew into the carbon layer. The growth rate of the precipitates was 100-200nm/min at 873K. EDS and EELS showed that the concentration of the iron in the precipitates was almost 100% and carbon was seldom detected. Only the diffusion of iron into the carbon layer was clarified. The images of the precipitates and the results of EDS and EELS indicated the precipitates were as the result of exchange of iron and carbon.

  A contamination on a surface is a serious problem in thickness measurement especially for thin films less than ten nanometers. Water contact angles are sensitive to the surface condition and the degree of contamination and can be a very useful criterion for a judgment of the effect in practical cleaning processes. The UV-ozone cleaning is the most effective one in removal of carbon contamination in the method we investigated.