K. Takashima

A quantitative auger electron spectroscopy method (applied to a thin film monolayer overgrowth)

Abstract When a thin film grows in a monolayer overgrowth fashion, the AES signal versus film thickness is calculated by a quantitative AES method. The method is applied to the Cases of Ag on Au, Mo on W and Be on Cu. The calculated results agree very well with the experimnetal results. In this method, the following points are considered: (1) the attenuation of a primary beam, (2) the effects of back-scattered and forward-scattered electrons both from thin film and substrate materials, (3) the escape depths of any electrons, and (4) the effect of the three-dimensional movements of secondary electrons and Auger electrons in the solid. Consequently, especially from the above effect (4), the curve of Auger electron signal intensity versus film thickness can be estimated for the various optics (e.g. Cylindrical Mirror Analyzer (CMA), Low Energy Electron Diffraction (LEED) optics,…) used for the usual Auger experiments. Electron mean free paths can be obtained by the interpolation or the extrapolation for the different atomic numbers and the different energies from the published experimental result of Mo and W. The result by this method has a similar tendency as the result obtained by Penn. Also, the number of back-scattered and forward-scattered electrons can be estimated by the coefficient of secondary electrons with energy above the ionization electron energy E C to produce Auger electrons. Then, the values of the secondary electron coefficients are measured and tabulated for the 20 different elements from Be to U as a function of the ionization electron energy.

Comparison of escape depths between Auger electron and disappearance potential spectroscopy electron

Abstract The escape depths of the characteristic electrons of the Auger electron and the quasielastically reflected electron were determined by Auger electron spectroscopy (AES) and disappearance potential spectroscopy (DAPS), respectively, for a Cr overlayer onto Ti and Fe substrates. For the case of Cr on Fe, in-situ measurements of AES and DAPS were carried out. From the results, the mean free paths of 455, 575 and 710 eV electrons through Cr were obtained as 9.6, 13 and 15 A, respectively. The attenuation length of a 2.5 keV primary electron of AES through Cr was also obtained and the value was 62 A. In addition, the mean free paths of electrons with the same energy depend on the scattering materials of Cr, Mo and W (material dependence). The phenomena are useful for a quantitative electron spectroscopy of surfaces.

A quantitative AES method for the study of a monolayer over-growth of thin film

Abstract In a monolayer over-growth of a thin film, a theoretical method for constructing a quantitative calibration curve for an AES signal versus deposit film thickness has been developed. The curve can be easily obtained by only measuring secondary electron coefficients from the pure deposit and substrate materials. The method is applied to and compared with thin film growth experiments of Ag on Au and Be on Cu, with acceptable agreement.

Composition and thickness of the surface segregation region of a binary alloy system determined by a quantitative Auger electron spectroscopy method

Let us consider the surface composition of the binary alloy, where the surface composition R1 is considered to be different from the bulk inside composition R2 and also the segregation region thickness is T. In this model it is possible to count the Auger signals considering the contributions of an attenuating primary beam and the secondary electrons which are backscattered and forwardscattered. Using the theory, we have calculated these R1 for the reported experimental results of the Ag‐Au binary alloy as a function of T. The calculated Ag composition R1 are compared with the ISS (Ion Scattering Spectroscopy) results that are said to be the most surface sensitive technique. When the bulk Ag content is less than 50 at. %, the Ag segregation region thickness T is considered to be one monolayer (2.58 A ∼ an average layer spacing, d3 = M/6.02×1023ρ, where M = atomic mass and ρ = specific mass or density). However, when the bulk content is greater than 50 at. %, T lies between one and two monolayers (2.58 and...

New surface structure analysis of Ag-Si phase by quantitative auger electron spectroscopy method

Abstract Ag or Au was deposited on a clean Si substrate at room temperature. These systems, Ag/Si and Au/Si, were annealed at various temperatures or various heating times. Due to the annealing, Ag or Au diffused into Si and/or Si diffused into the metal. The changes of the surface composition are analyzed by a quantitative Auger Electron Spectroscopy (AES) method which is newly developed as a non-destructive method. In the case of Ag/Si, Ag migrated into the Si substrate and/or Si diffused into Ag. Then, Ag-Si solid solution was produced. After the annealing, the Ag/Si system is changed into Ag/(Ag-Si)/Si of the three-phase structure. In the case of Au/Si (Au film thickness

Introduction of a calibration line for composition determination of a binary alloy by Auger electron spectroscopy (quantitative formalism)

In a complete uniform solid solution of a binary alloy, a theoretical method for constructing a very quantitative calibration line for an AES experiment has been developed. In the method, the following are considered: (i) attenuation of a primary beam, (ii) the effects of backscattered electrons and forwardscattered electrons both from solute and base metals, and (iii) true escape lengths of any electrons. Results of calculations are applied for Ag‐Au, Mo‐W, and Be‐Cu systems.

KCl(100) Surfaces and Epitaxial Grow h of Ag on KCl Studied by LEED and Auger Emission Spectroscopy

Argon ion bombarded KCl(100) surfaces are compared with air and vacuum cleaved surfaces by LEED and AES experiment. When Ag was evaporated on both argon ion bombarded and air cleaved KCl surfaces, the former showed better epitaxial growth. From these surfaces, Cl signals were always observed from AES curve. Therefore, a great probability of K and Cl diffusion into Ag film can be expected. When a total secondary electron curve was taken from KCl surface, elastic peak heights at higher voltages (up to 1 KeV) were very small. They are probably due to dissociation of the KCl surface. This is clearly related to LEED observable voltage regions. Alkali halides are materials from whose surfaces LEED patterns are observable up to several hundred voltages. However, Ta and MgO samples can be observed by LEED up to 1 KeV.