J. Le Héricy

An important step in quantitative auger analysis: The use of peak to background ratio

Abstract If the Auger ratio is defined as being the ratio of the Auger peak to the background at the same energy, this Auger ratio can be considered as an intrinsic measurement, characteristic of the sample, and in a very large degree independent of the instrumental parameters adjustment: intensity of the primary electron beam, modulation voltage, Wehnelt voltage, focusing, deflection, sample positioning, electron multiplier gain and further amplification. However, this Auger ratio depends on the primary electron energy. In a specimen homogeneous in depth, the Auger ratio of an element X normalized to that obtained on a pure X sample yields a direct measurement of the volume fraction occupied by that element in the sample. It is no longer necessary to normalize an Auger peak to the sum of all the other peaks, or to resort to the ratio of the peaks on a given spectrum. Providing that the respective mean free paths of the Auger electrons are sufficiently different, it is even possible to acquire a valuable information on the depth distribution of the elements.

Quantitative approach of Auger electron spectrometry: I. A formalism for the calculation of surface concentrations

We describe a formalism leading to a quantization of Auger spectrometry without resorting to standards. An element of the matrix is choosen as a reference and the other species have their Auger signals expressed in terms of the Auger signal of that reference by means of a sensitivity coefficient α. The intensity of an Auger signal is interpreted as the sum of the contributions given by every atomic layers of the sample, each of them being characterized by an attenuation coefficient k, closely related to the escape depth of the Auger electrons. We derive a formalism which allows us to determine the elemental composition of the atomic layers. Homogeneous sample, heterogeneous sample, multiphase sample, surface segregation and depth profiling have been considered.

Quantitative approach of Auger electron spectrometry: II. Experimental part

Abstract We illustrate the formalism proposed in part one by two studies: thermal segregation of impurities on the surface of a titanium sample, and chemical depth profiling of a passive film formed on stainless steel. The choice of an Auger transition which does not involve valence electrons is particularly emphasized to obtain a satisfactory quantification, when active species are present on the surface.

Contribution a l'etude du dosage par radioactivation du sourfre et du phosphore en tres faibles concentrations dans les metaux de tres haute purete (Aluminium, magnesium, cuivre, fer, nickel)

The determination of sulphur and phosphor by means of activation analysis in high purity aluminium and magnesium is described. The irradiations were performed both with thermal and with fast neutrons. A detailed procedure is given and errors not considered so far are discussed.

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.u2009%, 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.u2009%, T lies between one and two monolayers (2.58 and...

Interstitial trapping by Ni, Ag, in impurities in electron irradiated copper

Abstract Samples of copper, pure and alloyed with very small amounts of Ni, Ag, In impurities have been submitted to isochronal recovery between 10K and 60K after low temperature electron irradiation. The capture radii of the self interstitial atoms by the impurities are found: R Ni ∽ 0, R Ag = 1, R In = 1.5 in units of rv, the average vacancy capture radius for migrating self-interstitials.

Surface composition analysis of Au-Cu alloy by micro-auger electron spectroscopy

Abstract The surface compositions of Au-Cu binary alloys are different from the bulk. The surfaces of the Au-Cu specimens covering all the bulk composition ranges are analyzed by a quantitative AES method. For the Au-Cu alloy surface compositions at room temperature, Au segregates at the surface within a layer of 5–6 A and Cu segregates in a deeper layer between 20–30 A, when the Au bulk compositions are from 40 to 90 at%. However, when the Au bulk compositions are over 90 at%, Cu always segregates in all the surface region. When the Au bulk compositions are less than 40 at%, Au always segregates in all the surface region.

Depth information in Auger electron spectroscopy

Two different methods giving non destructive depth information in Auger Electron Spectroscopy (AES) are described, (i) The first one is based on the Auger ratio PB (ratio of the Auger peak to the background at the same energy). In the case of a binary alloy XY, and as soon as the Auger electron mean free paths of the two elements are sufficiently different, it is possible to obtain a depth information by plotting (PB)x versus (PB)y (ii) The second one is more general and uses the ratio of the Auger tail height (T) to the Auger peak height (P). This ratio (TP) is independent of the concentration of the element. It is only dependent on its depth distribution. Both methods are applied to the experimental example of a silver deposit on a Si(111) surface.