Henning Bubert

Surface and thin film analysis : a compendium of principles, instrumentation, and applications

Surface and thin film analysis: a compendium of principles, instrumentation, and applications , Surface and thin film analysis: a compendium of principles, instrumentation, and applications , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Comparative surface and bulk analysis of oxygen in Si3N4 powders

SummaryFive commercially available α-Si3N4 powders and one in theβ modification were subjected to Auger electron spectroscopy (AES) and carrier-gas-heat extraction (CGHE) analysis.AES depth profiles of the oxygen/nitrogen ratio could be obtained, from which total oxygen contents were calculated and compared to CGHE data. It is demonstrated that by the latter method also dissolved oxygen in α-Si3N4 is detected, whereas by AES only chemically bound oxygen can semiquantitatively be analyzed. Evidence is found for the existence of water, adsorbed or present as hydroxyl groups, near the surface.

Comparative investigation on copper oxides by depth profiling using XPS, RBS and GDOES

Depth profiling has been performed by using X-ray photoelectron spectrometry (XPS) in combination with Ar-ion sputtering, Rutherford backscattering spectrometry (RBS) and glow discharge optical emission spectrometry (GDOES). The data obtained by XPS have been subjected to factor analysis in order to determine the compositional layering of the copper oxides. This leads to two or three relevant components within the oxide layers consisting of Cu2O or CuO dependent on the sample preparation. GDOES measurements show sputtering profiles which are seriously influenced by a varying sputter rate. To ensure the results obtained so far, RBS measurements of the oxide layers have been carried out in order to discover artefacts of the other methods used and to demonstrate the excellent suitability of RBS for quantitative analysis of these layers. Chemical analysis consisting of (1) carrier-gas fusion analysis (CGFA) and (2) selective dissolution of Cu2O/CuO allows the determination of the total amount of oxygen and copper, respectively, and can serve as a cornerstone of quantitative analysis.

AES investigation of thermally sprayed Al2O3 coatings on steel

SummaryThe investigation of plasma sprayed steel/Al2O3 composites by means of Auger Electron Spectroscopy (AES) combined with depth profile analysis is described. Incomplete sprayed Al2O3 layers permit analysis of single sprayed particles and of surrounding uncovered steel substrate regions. More complete coatings are separated from the substrates, so that contact surfaces of substrates and Al2O3 layers can be analyzed. In order to determine the influence of preheating the substrates on the interface widths between steel substrate and Al2O3 coating and therefore on the adherence mechanism, both procedures are carried out for two preheating temperatures. It is shown that preheating hardly effects the interface widths beneath single sprayed particles but it causes laterally constant widths for complete layer fragments. Additionally, a comprehensive view about oxide layer thicknesses on the steel substrates before and after plasma spraying is offered.

Matrix factors affecting quantitative analysis of AES for binary alloys

Abstract To improve the accuracy of quantitative AES analysis, matrix effects disturbing the linearity between the intensity of an Auger signal and the atomic concentrations have to be considered. Matrix factors accounting for these effects refer to (1) electron back-scattering, (2) attenuation length, (3) Auger line shape, (4) initial surface roughness, (5) sputter-induced surface roughness during depth profiling, (6) preferential sputtering, (7) elemental sensitivity and (8) atomic density. Measurements are presented on three systems of binary alloys (Ag/Cu, Ni/Cr and Pb/Sb), whose elemental concentrations range from 0 to 100%. They indicate that the relation between the measured and the true concentration can be expressed by a single formula with two parameters describing summarily the various matrix effects mentioned above. We derive the separation of the contributing factors (1) to (8) from the equation of the Auger electron intensities for a binary system, and their inclusion into the two-parameter approach mentioned. Values for these parameters are empirically estimated for the systems under investigation. The significance of individual factors (1) to (8) in these systems is discussed. The matrix factors mentioned do not fully describe all experimental data obtained from these alloys.

AES investigations on starting powders for high performance ceramics

AES depth profiles on ceramic powders (untreated/hydrolyzed/oxidized/ (Al, Y)2O3 coated Si3N4, [BaO, SiO2] coated Al2O3) are feasible on thin, homogeneous layers or μm sized agglomerations prepared on an Au foil. By means of the depth profiles one can qualitatively characterize the coating around the particles. Factor analysis of the depth profiles on the differently treated Si3N4 powders suggests the existence of an Si2N2O phase on the oxidized sample.

Calibration of sputtering yields for AES depth profiling of oxide layers on aluminium by means of carrier-gas heat extraction analysis

SummaryFor the purpose of obtaining suitable reference materials for technical coatings on aluminium, the feasibility of calibration of oxide layers by means of heat extraction was studied. Oxide layers were prepared on aluminium sheets by immersion in water of 50 or 80 ° C and annealing at 500 or 600 °C in argon atmosphere. The layer thickness was calculated from the oxygen content of the sample as measured by carrier-gas heat extraction analysis.The total sputtering yield of aluminium oxide layers was obtained via the correlation of AES depth profiling with heat extraction analysis results. This was demonstrated for high purity (99.9%) and technical purity (98.5%) aluminium with its original roughness from the rolling process, on which 20 to 1,000 nm thick oxide layers had been grown.The sputtering yields for the oxide layers prepared were found to be 3.9±0.8 atoms/ion, i.e., about four times higher than that for α-Al2O3. Calibration of depth profiling on such technical quality oxide layers on aluminium was found to be feasible with a relative precision of 10 to 20%.

Vergrabene Nitrid-Schichten in Silicium für Kalibrierproben zur quantitativen Auger-Elektronenspektrometrie (AES)

SummaryBuried layers of silicon nitride in silicon are produced by high-dose ion implantation and are checked for their suitability as calibration samples for quantitative thin film analysis. For this purpose, N+ ions (150 and 300 keV; 0.35 to 1×1018 N+ cm−2) are implanted into silicon single crystals and the samples annealed at 1,200°C for up to 15 h. The signal intensities and the sputter time obtained by AES/ sputtering can be converted into nitrogen content and sample depth by means of independent calibration measurements. The absolute depth scale is obtained by AES microanalysis at angle lapped surfaces (angle <1°) and by comparison with Monte Carlo simulation. The accuracy obtained is about 30 nm at a profile depth of 0.3 μm. The nitrogen content is determined quantitatively by means of the measured implantation dose.Additional methods of calibration are discussed. It is shown that the samples used are suitable as calibration samples for the silicon/nitrogen system.ZusammenfassungVergrabene Nitridschichten in Silicium werden durch Hochdosis-Ionenimplantation hergestellt und auf ihre Eignung als Kalibriermaterial für die quantitative Dünnschichtanalyse geprüft. Dafür werden N+-Ionen (150 und 300 keV; 0,35–1·1018 N+ cm−2) in Si-Einkristallen implantiert und durch Temperung (1200°C, bis 15 h) formiert. Die mit AES/Sputtering erhaltenen Signalintensitäten als Funktion der Sputterzeit können mit Hilfe unabhängiger Kalibriermessungen in die Stickstoffgehalte als Funktion der Probentiefe transformiert werden. Die Tiefenzuordnung wird durch AES-Mikroanalyse an Schrägschliffen (<1°) und durch Vergleich mit Monte-Carlo-Simulation mit einer Genauigkeit von ca. 30 nm bei 0,3 μm Profiltiefe erhalten. Der Stickstoffgehalt wird mittels der gemessenen Implantationsdosis bestimmt. Weitere zusätzliche Bestimmungsmethoden werden diskutiert.Es zeigt sich, daß die beschriebenen Proben als Kalibriermaterial für das Stoffsystem Silicium/Stickstoff geeignet sind.

Application of factor analysis in electron spectroscopic depth profiling on copper oxide

Depth profiles were taken by x-ray photoelectron spectrometry/Ar-ion sputtering from copper sheets oxidized during 30 min in air at 200 or 300°C, respectively. The data of the depth profiles were subjected to factor analysis in order to determine the relevant components of the copper oxide layers. Factor analysis shows the existence of a cuprous oxide layer (Cu2O) on both specimens under bombardment with 2 keV argon ions during depth profiling. Rutherford backscattering measurements and carrier gas fusion analysis were successfully applied to determine the oxygen content of the oxide layers. Results corroborate the identification of Cu2O in both layers.

Contribution to the analytical characterization of coatings produced by thermal spraying

This paper reports on the use of Auger electron spectroscopy (AES)/ depth profile analysis for the investigation of plasma-sprayed coatings. Prior to spraying the St 37 substrates are heated to 300 °C or 500 °C for ceramic or metallic layers, respectively. Studies of the starting materials and of the interfaces are important if the adhesion mechanism is to be understood. Therefore the initial components—the unheated and heated substrates and the powder particles NiCrAl, Al2O3 and ZrO2-7.25Y2O3—are analyzed. Depth profiles obtained from two coatings St 37/NiCrAl and St 37/Al2O3 show the influence of plasmaspraying on substrate surfaces and sprayed particles. Plasma-spraying mainly causes a decrease of superficial carbon contamination for both coating layers. In the case of St 37/NiCrAl incorporation of carbon in the sprayed layer is observed. The whole layer is almost completely oxidized except for some areas where substrate and particle material are present. It is assumed that these areas are identical with so-called adherence zones.