There are many approaches for quantitative Auger electron spectroscopy (AES), and procedures are still being proposed. Matrix effects are usually neglected in quantitative analysis, and often result in errors by more than a factor of two. These errors arise from the neglect of electron backscattering, change in density and change in electron inelastic mean free path with change of matrix. One proposal to reduce such errors is the use of average matrix sensitivity factors instead of elemental sensitivity factors, but this approach has not yet been adopted by the AES community (and is not discussed here). This paper deals with some fundamental approaches that have been used to measure and isolate Auger peaks (and area values) for use in quantitative analysis, particularly those that were adopted in the early days of practical Auger electron spectroscopy. These early approaches include spectrum simulation, spectrum subtraction and spectrum integration, and many of their aspects are still important today.

  The main applications of electron backscattering in sputter depth profiling using AES and related electron spectroscopies such as elastic peak electron spectroscopy (EPES) and reflection electron energy loss spectroscopy (REELS) are briefly summarized. EPES depth profiling is particularly useful for improving the interfacial depth resolution in binary systems by selecting a suitable primary electron energy. With REELS depth profiling, the change of the IMFP during sputtering through an A/B interface can be quantitatively determined. Recently, a method for implementing the backscattering effect in the MRI model has been introduced and applied to AES depth profiles of single layer and multilayer structures. Its capability to provide quantification of measured profiles including the backscattering effect is outlined.

  There is currently increasing interest in a more complete theoretical description of the signal intensity in Auger electron spectroscopy (AES). We report calculations of backscattering factors (BFs) for three selected Auger transitions (Al KL₂₃L₂₃, Pd M₅N₄₅N₄₅, and Pt M₅N₆₇N₆₇) in the corresponding elemental solids using two algorithms. With algorithm A, BF values were obtained with a Monte Carlo calculation in which individual inelastic-scattering events were simulated. With the more approximate, but faster algorithm B, BFs were calculated using the continuous slowing-down approximation and stopping powers from a recently developed predictive formula. For primary-beam energies between 3 keV and 20 keV, differences in BFs from the two algorithms ranged between 1.3 % and 9 % for the three Auger transitions. These differences arose mainly from limitations of the predictive formula for the stopping power with algorithm B. Nevertheless, the differences are believed to be sufficiently small to enable use of the faster algorithm B for many applications in quantitative AES.

  The results of the investigation of the inelastic interaction of medium-energy electrons with the Ni surface were described. The inelastic mean free path (IMFP), the surface excitation parameter (SEP) and the differential SEP (DSEP) were deduced simultaneously from an absolute reflection electron energy loss spectroscopy (REELS) spectrum. The present IMFPs show a good agreement with those calculated using the TPP-2M predictive equation. The dependence of the SEPs on the electron energy is similar to that calculated using Werner’s and Gertgely’s predictive equations. The DSEPs show a reasonable agreement with the theoretical DSEPs calculated using Tung’s theory with optical data. The derived IMFP, SEP and DSEP were applied to Monte Carlo simulation of REELS spectra, in which energy loss processes of signal electrons due to surface excitations were taken into account. The simulated REELS spectra reproduce the experimental absolute REELS spectra well without any fitting parameters, indicating that surface excitations play an important role in the inelastic interaction of medium-energy electrons with the solid surface.

  The inelastic mean free path (IMFP) can be determined from the elastic-backscattering probability I_e of electrons that can be measured by elastic peak electron spectroscopy (EPES). We calculated IMFPs from the absolute I_e measurements of Goto. Calculated values of the elastic backscattering-probability I_ec can be obtained from the EPESWIN software of Jablonski. I_ec denotes the number of electrons/incident electron, backscattered elastically and detected with the cylindrical mirror analyzer (CMA) of Goto. The I_e data deduced from the database of Goto are lower by 20-34% than the calculated I_ec for Si, Ni, Cu, Ag and Au. This discrepancy is explained by surface-excitation losses characterized by the SEP parameter. We made corrections for the experimental I_e data for surface excitations using the material parameters of Chen (modified), Kwei, Ding, and Werner. The parameters of Chen were modified for achieving the minimum deviations between the calculated of I_ec and the SEP corrected f_sI_e values. The material parameter of Nagatomi a_ch = 4.3 was confirmed for Ni by EPES. The SEP corrected IMFPs were deduced from the SEP corrected f_sI_e data. SEP correction of the IMFPs resulted in mean deviations from the calculated TPP-2M data of 3.9 % for Si, 6-7% for Ni, 8.2% for Ag and nearly 12 % for Cu and for Au.

  This paper is a brief review of our final absolute Auger electron spectroscopy which was presented in the work shop on “Electron Transport Parameters Applied in Surface Analysis” (Lake Balaton, Hungary, Sept. 14-17, 2008) as a poster and new data of Ge(111). Some modifications and corrections are made from the poster. This work has been continued in these 21 years and only the significant change was the transmission of the meshes in the analyzer (cylindrical mirror analyzer); effective transmission being 0.22sr and 0.199(9)sr for 42.3 ±6 degrees of emission cone for the data before and after 2008, respectively. This change was due to the over-coating of soot on the former aquadag coating on the gold plated tungsten meshes to stabilize the work function and to reduce the scattered electrons and secondary electrons at the mesh. These Auger electron spectra can now be available on the web; http://www.sasj/COMPRO and http://riodb.ibase.aist.go.jp/DB111/welcome.html.

  The charged water droplets used in electrospray droplet impact (EDI) are extremely large cluster ions with masses of about a few 10⁶ u. When a target is etched by EDI, the physical sputtering of the target does not take place to the recognizable extent. The etched surfaces of TiO₂ thin film on Si(100) by EDI were evaluated by AES crater edge profiling. We found that TiO₂ thin film do not suffer from de-oxygenation by EDI etching.

  A comparison of data obtained by using different formulae for predicting ratios of effective attenuation lengths to inelastic mean free paths for energetic (with energies up to 15 keV) electrons, and experiments is given for the case of several elemental solids such as Si, Ni, Cu, Ge, Ag, W and Au. The results demonstrate the estimated accuracy of these simple approximations as well as the decreasing effect of elastic electron scattering with increasing electron energy.

  The energy distribution of secondary electrons emitted from several metals has been investigated theoretically and a comparison of Monte Carlo simulation result with an experimental measurement has been made. The Monte Carlo simulation of cascade secondary electron production is based on the use of a dielectric function for the treatment of electron inelastic scattering and secondary excitation, and on the use of Mott cross section for describing electron elastic scattering. The calculation reproduces well the weak features presented in the experimental energy spectra of secondary electrons measured with a cylindrical mirror analyzer. The result indicates that, the weak feature is resulted from the directly emitted secondary electrons after generation without energy loss processes and, thus, carries the characteristic energy transferred from the loss energy of the incident electrons. However, during their transportation to the surface much of the cascade secondary electrons have suffered quite energy losses and to be presented as the large background.

  We have determined electron inelastic mean free paths (IMFPs) and surface-electronic excitation parameters (SEPs) of Au and Cu in the 200 - 5000 eV from their elastic peak intensity ratios without reference IMFP values. This proposed method does not require the IMFP values of the reference material. The measurements of elastic peak intensities of these elements were done with noble CMA system. The elastic peak intensities were also calculated from two parameter sets (IMFPs and SEPs for both elements) with Monte Carlo method. By comparison of these two EPI ratios as changing the parameter sets, we have estimated their IMFPs and SEPs in the 200 - 5000 eV energy range. The resulting IMFPs of Au and Cu were in good agreement with optical IMFPs over 1000 eV energy range.