EDX depth profiling by means of effective layers

A new approach is described for depth profiling in stratified multilayer samples by recording energy dependent characteristic x-ray EDX(E ₀ ) curves in a scanning electron microscope. An effective layer technique replaces the x-ray excitation function of the heterogeneous target by an equivalent function of a homogeneous sample. First results of thickness determination are shown and compared to direct measurements of film thickness monitoring (FTM) and atomic force microscopy (AFM).     

Characterization of metallic layer composites by means of AES/depth profile analysis

The adherence mechanism of arc sprayed Ni layers on structure steel St37 is investigated. AES depth profiles are obtained on single Ni particles still adhering to the substrate after the Ni layer has been separated from it. A comparison of interface shapes and results of adherence measurements reveals Fe-Ni layered structures for the best adhering layers, whereas less adhering layers are characterized by narrower interfaces caused by diffusion. Areas with no adherence are covered with oxidic layers.     

Characterization of oxide layers on amorphous Mg-based alloys by Auger electron spectroscopy with sputter depth profiling

Amorphous ribbons of Mg-Y-TM-[Ag] (TM: Cu, Ni), prepared by melt spinning, were subjected to electrochemical investigations. Oxide layers formed anodically under potentiostatic control in different electrolytes were investigated by AES and sputter depth profiling. Problems and specific features of characterization of the composition of oxide layers and amorphous ternary or quaternary Mg-based alloys have been investigated. In the alloys the Mg(KL(23)L(23)) peak exhibits a different shape compared to that in the pure element. Analysis of the peak of elastically scattered electrons proved the absence of plasmon loss features, characteristic of pure Mg, in the alloy. A different loss feature emerges in Mg(KL(23)L(23)) and Cu(L(23)VV). The system Mg-Y-TM-[Ag] suffers preferential sputtering. Depletion of Mg and enrichment of TM and Y are found. This is attributed mainly to the preferential sputtering of Mg. Thickness and composition of the formed oxide layer depend on the electrochemical treatment. After removing the oxide by sputtering the concentration of the underlying alloy was found to be affected by the treatment.     

Description of sputter removal during auger depth profiling of rough oxide layers

A model for describing sputter depth profiles on rough surfaces is presented; this is based on the assumption that sputter removal occurs at preferred sites due to the intrinsically rough surface. The progress of sputtering is described by the growth and overlap of statistically distributed holes in the surface layer. Within this assumption the variation of the Auger signal intensity during sputtering is described by simple functions. The model is applied to the sputter removal of oxide layers formed on INCOLOY 800 in hot water.     

SEM and AES depth profile studies of thin titanium and titanium oxide films covered by nanoscale evaporated Au layers

Thin titanium and titanium oxide films, both covered by ultra-thin gold layers, have been compared with titanium films after analysis, using a combination of SEM and AES. The Ti films were prepared under UHV conditions by evaporation on a glass substrate. The Ti oxide layers were prepared in situ by precisely controlled oxygen sorption at 298 K on Ti film. Both Ti and Ti oxide films were then covered in situ by a very thin Au layer. Analysis was performed in a separate system after long-term exposure of the films to air. SEM analysis revealed a much smaller size grain on the Au coated Ti films than on Ti films not coated with a Au layer. The thin gold layers covering the Ti surface prevent an extensive air interaction with Ti film. The analysis of the features of the Ti Auger spectra during the sputter profile measurements allow to characterise the chemical nature of Ti-oxide formed in Ti/Au interface region. Received: 7 September 1998 / Revised: 14 January 1999 / Accepted: 2 February 1999     

Examples for the improvements in AES depth profiling of multilayer thin film systems by application of factor analysis data evaluation

Factor analysis has proved to be a powerful tool for the full exploitation of the chemical information included in the peak shapes and peak positions of spectra measured by AES depth profiling. Due to its ability to extract the number of independent chemical components, their spectra and their depth distributions, its information content exceeds the one of the usual peak-to-peak height evaluation of AES depth profile data. Using modern software with a graphically interactive user interface the analyst is put into a position, where he can work with Factor Analysis on a physically intuitive level despite of all the matrix algebra mathematics which it is based upon. The progress brought about by Factor Analysis to AES depth profiles of thin films is demonstrated by the analysis of two thin film systems. The first one is a Pt/Ti metallisation used as bottom electrode for ferroelectric thin films, the second one is a multilayer system where a Ti silicide formation of buried Ti/Si bilayers has been induced. Both examples show that Factor Analysis evaluation of AES depth profile data is capable to give access to stoichiometry information and to reveal interfacial layer phases, information which is hardly obtained from the conventional peak-to-peak height data evaluation.     

Examples for the improvements in AES depth profiling of multilayer thin film systems by application of factor analysis data evaluation

Factor analysis has proved to be a powerful tool for the full exploitation of the chemical information included in the peak shapes and peak positions of spectra measured by AES depth profiling. Due to its ability to extract the number of independent chemical components, their spectra and their depth distributions, its information content exceeds the one of the usual peak-to-peak height evaluation of AES depth profile data. Using modern software with a graphically interactive user interface the analyst is put into a position, where he can work with Factor Analysis on a physically intuitive level despite of all the matrix algebra mathematics which it is based upon. The progress brought about by Factor Analysis to AES depth profiles of thin films is demonstrated by the analysis of two thin film systems. The first one is a Pt/Ti metallisation used as bottom electrode for ferroelectric thin films, the second one is a multilayer system where a Ti silicide formation of buried Ti/Si bilayers has been induced. Both examples show that Factor Analysis evaluation of AES depth profile data is capable to give access to stoichiometry information and to reveal interfacial layer phases, information which is hardly obtained from the conventional peak-to-peak height data evaluation.     

Modeling of glancing incidence X-ray for depth profiling of thin layers

In this work, we present a method to obtain quantitative information about the thickness of thin, polycrystalline layers. This non-destructive method is based on Glancing-Incidence X-ray Diffraction (GIXRD) experiments at different incidence angles. At different incidence angles, information about phases lying at different depths is obtained. The diffracted X-ray intensities' dependence on the glancing angle was analyzed and compared with simulations performed by means of a simple optico-geometrical model taking into account the Fresnel coefficients, X-ray absorption, and the effective scattered volume. The depth profile of polycrystalline Au layers was evaluated to test the procedure. The results of the GIXRD and the simulations are in very good agreement with the thickness obtained by means of X-ray reflectivity (XRR) technique.     

Multielement analysis of aluminium by NAA and ICP/AES

The results of neutron activation analysis (NAA) and inductively coupled plasma atomic emission spectrometry (ICP/AES) are compared for aluminium samples in the purity range from 99.7 to 99.998%. The advantages of each method towards the determination of 25 elements is discussed.     

Characterization of interfaces of alumina – high alloyed steels by SST and AES depth profiling

Thin alumina films, deposited at 280°?C on several high alloyed steels by low pressure metal-organic chemical vapour deposition (LP-MOCVD), were annealed at 0.17 kPa in a nitrogen atmosphere for 2, 4 and 17 h at 600 and 800°?C. The effect of the annealing process on the adhesion of the thin alumina films was studied using a scanning scratch tester (SST) and Auger electron spectroscopy (AES). The best adhesion properties were obtained with commercial oxide dispersion strengthened (ODS) high temperature alloys, especially type PM 3030. From the “normally” high alloyed stainless steels, type AISI-321 showed the best properties. The other stainless steel – alumina combinations showed after a thermal treatment a decrease of the critical load, L_c. Using ODS alloys as the substrate resulted in an increased L_c. AES-studies revealed that the increased L_c can be explained by 1) the presence of sulphur trapping elements, avoiding segregation of sulphur near the interface which could have a detrimental effect on scale adherence, and 2) titanium and carbon enrichment at the interface resulting in a beneficial effect on the adherence between the oxide and the substrate.     

Quantitative molecular depth profiling of organic delta-layers by C60 ion sputtering and SIMS

Alternating layers of two different organic materials, Irganox1010 and Irganox3114, have been created using vapor deposition. The layers of Irganox3114 were very thin ( approximately 2.5 nm) in comparison to the layers of Irganox1010 ( approximately 55 or approximately 90 nm) to create an organic equivalent of the inorganic 'delta-layers' commonly employed as reference materials in dynamic secondary ion mass spectrometry. Both materials have identical sputtering yields, and we show that organic delta layers may be used to determine some of the important metrological parameters for cluster ion beam depth profiling. We demonstrate, using a C(60) ion source, that the sputtering yield, S, diminishes with ion dose and that the depth resolution also degrades. By comparison with atomic force microscopy data for films of pure Irganox1010, we show that the degradation in depth resolution is caused by the development of topography. Secondary ion intensities are a well-behaved function of sputtering yield and may be employed to obtain useful analytical information. Fragments characteristic of highly damaged material have intensity proportional to S, and those fragments with minimal molecular rearrangment exhibit intensities proportional to S(2). We demonstrate quantitative analysis of the amount of substance in buried layers of a few nanometer thickness with an accuracy of approximately 10%. Organic delta layers are valuable reference materials for comparing the capabilities of different cluster ion sources and experimental arrangements for the depth profiling of organic materials.     

The fluorimetric detection of pesticides on aluminium oxide layers.

Several pesticides have been investigated for their fluorigenic properties on acidic and basic aluminium oxide layers. Fluorescence was obtained in several instances and the relative intensities were observed. Fluorescence spectra were recorded for the best fluorescence obtained before and after heat treatment of the chromatogram. The results are compared with those already reported for silica gel layers.     

Quantification problems in depth profiling of pwr steels using Ar+ ion sputtering and XPS analysis.

The oxide scales of AISI 304 formed in boric acid solutions at 300 degrees C and pH = 4.5 have been studied using X-ray photoelectron spectroscopy (XPS) depth profiling. The present focus is depth profile quantification both in depth and chemical composition on a molecular level. The roughness of the samples is studied by atomic force microscopy before and after sputtering, and the erosion rate is determined by measuring the crater depth with a surface profilometer and vertical scanning interferometry. The resulting roughness (20-30 nm), being an order of magnitude lower than the crater depth (0.2-0.5 microm), allows layer-by-layer profiling, although the ion-induced effects result in an uncertainty of the depth calibration of a factor of 2. The XPS spectrum deconvolution and data evaluation applying target factor analysis allows chemical speciation on a molecular level. The elemental distribution as a function of the sputtering time is obtained, and the formation of two layers is observed-one hydroxide (mainly iron-nickel based) on top and a second one deeper, mainly consisting of iron-chromium oxides.     

Determination of an accurate depth distribution of sodium, calcium and aluminium in thin oxide layers using several methods

Summary Experience in obtaining accurate sodium, calcium and aluminium profiles in silicon dioxide using SIMS and Auger depth profiling is reported. With the knowledge of implantation energy and ion dose, it is possible to calculate and to realize well defined implantation profiles in special substrates with high accuracy. The technological demand is to measure this so called accurate profiles in implanted structures without alteration by the measurement. SIMS and Auger profiling have been tested in special applications to study the influence of ion sputtering on the depth distribution in membranes and to obtain accurate profiles. Experimental results are presented for the application of Auger profiling at sample edges and SIMS profiling using negative ions. In the case of Auger profiling a transformation routine was developed for using linescan and sputter profile results in combination.     

Evaluation of the sputtering rate variation in SIMS ultra‐shallow depth profiling using multiple short‐period delta layers

We have developed multiple short‐period delta layers as a reference material for SIMS ultra‐shallow depth profiling. Boron nitride delta layers and silicon spacer layers were sputter‐deposited alternately, with a silicon spacer thickness of 1–5 nm. These delta‐doped layers were used to measure the sputtering rate change in the initial stage of oxygen ion bombardment. A significant variation of sputtering rate was observed in the initial 3 nm or less. The sputtering rate in the initial 3 nm was estimated to be about four times larger than the steady‐state value for 1000 eV oxygen ions. Copyright © 2003 John Wiley & Sons, Ltd.     

XPS depth profiling investigations on La2Zr2O7 layers prepared by chemical solution deposition

La₂Zr₂O₇ (LZO) layers have been recently investigated as potential buffer layers for superconducting YBa₂Cu₃O_7–x coated conductors deposited on Ni tapes. Chemical solution deposition was used for LZO layer preparation. X-ray photoelectron spectroscopy (XPS) depth profiling is demonstrated to be an important method for layer characterization in addition to X-ray diffraction techniques. XPS measurements revealed layers that are homogeneous in depth, very smooth, and have no significant impurities. A slight difference to the nominal La:Zr stoichimetry is discussed in combination with structural defects that are suspected from spectral changes during ion sputtering.     

AES and SIMS profiling of buried silicide layers formed by 6 MeV high dose nickel implantation into silicon

Summary The composition of deep-buried conductive layers formed by 6 MeV high dose Ni implantation into silicon at 450 K has been studied using AES and SIMS. For a dose of 1.3 × 10¹⁸ Ni/cm², AES analysis yields a Ni to Si ratio close to NiSi₂ stoichiometry at profile maximum, as expected from high dose Monte Carlo simulations. In this region the shape of the Si LVV Auger line indicates the presence of NiSi₂. TEM/XTEM investigations reveal a continuous NiSi₂ layer, showing a high density of extended defects.

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AES- und SIMS-Profilanalyse vergrabener Silicidschichten, die durch 6-MeV-Hochdosis-Nickel-Implantation in Silicium erzeugt wurden

     

Characterization of polymeric light emitting diodes by SIMS depth profiling analysis

SIMS depth profiling experiments have been used to elucidate the layered structure, the impurity distribution, and current induced changes in polymeric light emitting diodes (LEDs). In the first investigated system (ITO/PPV/Al), a poly-p-phenylene-vinylene (PPV) layer has been deposited onto an indium/tin oxide (ITO) glass support, and covered by an aluminium top electrode. A well defined aluminium oxide interlayer has been found in between the polymer and the Al overlayer. Furthermore, an enrichment of chlorine has been detected at both electrode-polymer interfaces, a residue from the polymer preparation process. This observation points to a chemical reaction between the electrodes and elimination products that are liberated during the thermal decomposition of the polymer precursor. In the second system, three different polymeric layers have been spin-coated onto an ITO substrate, i.e. a pure poly-methylphenylsilane (PMPS) layer, a second PMPS layer doped with an organic dye, and finally a polystyrene (PS) layer containing an oxadiazole derivative. By the addition of a bromine containing label into the first layer, it can be shown that the two PMPS layers have been diffusing into each other, whereas the PMPS and the PS regions have remained well separated. As found with the single layer devices, the formation of an interfacial oxide layer between the PS layer and the Al top electrode has been observed. Investigations of driven multilayer LEDs have provided evidence for drastic current-induced degradation effects.