Examples of Quantification in XPS on 5f Materials

 Various aspects of quantification in actinide research using photoelectron spectroscopy are discussed. In particular, the influence of instrumental factors, different types of the background, and shape of the line intensities are addressed. We give several examples of quantitative analysis of actinide bulk compounds and thin films.     

Atomic Force Microscopy Studies of SnO2 Thin Film Microstruc tures Deposited by Atomic Layer Epitaxy

 ALE-grown, rutile-type SnO₂ thin films and gas sensor structures based thereupon were studied by AFM with main emphasis on cross-sectional investigations (X-AFM). On glass substrates the polycrystalline films showed a preferred orientation which depended on the film thickness and growth temperature while on single crystal sapphire () the growth was heteroepitaxial. For the X-AFM studies various sample preparation techniques were investigated but only ion beam etching gave satisfactory results and revealed substructures in the sensor structure consisting of Pt and SnO₂ layers on a silicon substrate.     

Quantitative Analysis of Thin Aluminium-Oxynitride Films by EPMA

 Thin films of aluminium oxynitride with diverse composition were prepared by dc-magnetron sputtering of aluminium, utilising sputtering power as well as argon, oxygen and nitrogen gas flows to vary the composition. Since film properties depend mainly on the content of incorporated oxygen and nitrogen, a method for quantitative analysis of the main constituents based on electron probe micro analysis with energy dispersive detection was developed. The excellent precision of the quantitative results for aluminium as well as oxygen and nitrogen are shown. Furthermore, a film layer analysis program was applied for the quantification of several films deposited under the same deposition parameters on silicon wafers, from 520 nm down to 40 nm thickness, showing that electron probe micro analysis with energy dispersive detection is a reliable method for quantitative compositional analysis of thin aluminium oxynitride films down to approximately 20 nm thickness. Since this method of analysis provides only bulk information, expected inhomogeneities of the depth distribution of the film components were checked by secondary ion mass spectrometry depth profiles of two thin films and correlated to the EPMA results. The thickness of the films was determined by ellipsometry. Received September 1, 1998     

Analysis of Slightly Rough Thin Films by Optical Methods and AFM

 In this paper the analysis of a family of rough silicon single crystal surfaces covered with native oxide layers is performed using a combined optical method based on a multisample treatment of the experimental data obtained using variable angle of spectroscopic ellipsometry and near normal spectroscopic reflectometry. Within this analysis the values of the thicknesses of the native oxide layers are determined together with the values of statistical parameters of roughness, i.e. with the rms values of the heights and the values of the autocorrelation lengths, for all the samples studied. For interpreting experimental data the perturbation Rayleigh–Rice theory and scalar diffraction theory are employed. By means of the results of the analysis achieved using both the theories limitations of the validity of these theories is discussed. The correctness of the values of the statistical parameters determined using the optical method is verified using AFM measurements.     

Electronic Structure Effect of Polythiophene Derivatives and Nano N-Zn-Ag/TiO2 on Performance of Organic Thin Film Solar Cell

Nanocrystal N-Zn-Ag/TiO₂ powders were prepared with N-Zn/TiO₂ by photo deposition method. A series of pure polymers P3HT[poly(3-hexylthiophene)], P3OT[poly(3-octylthiophene)], P3DT[poly(3-decylthiophene)] and P3DDT[poly(3-dodecylthiophene)], was synthesized, which were used to synthesize p-n type semiconductor materials P3HT/N-Zn-Ag-TiO₂, P3OT/N-Zn-Ag-TiO₂, P3DT/N-Zn-Ag-TiO₂ and P3DDT/N-Zn-Ag-TiO₂ by in situ che-mical method. X-Ray diffraction(XRD) and infrared(IR) spectroscopy showed the structure of the polymers and complexes. Ultraviolet-visible(UV-Vis) spectra and cyclic voltammograms(CV) showed the optical and electronic performance of the polymers and complexes. Two new single and double organic thin film heterojunction solar cells were prepared with the above mentioned synthesized powders as raw materials. Current-voltage(I-V) measurements indicate that the conversion efficiency of the single organic thin film heterojunction solar cell is higher than that of the double organic thin film heterojunction solar cells. Single organic thin film heterojunction solar cells based on P3DT/N-Zn-Ag-TiO₂ can get a photoelectric conversion efficiency of 0.0408%. The performance of electronic transform between electron donor and acceptor on organic thin film solar cells was researched.     

Carbon Species and Precise Elemental Analysis of Precursors for Superconducting (Bi,Pb)2Sr2Ca2Cu3Ox Tapes

 The chemical composition of BiPbSrCaCuO precursors prepared by different syntheses has to be checked analytically before further application to production of superconducting (Bi,Pb)₂Sr₂Ca₂Cu₃O_x tapes. Carbon species in concentrations below 0,1%(w/w) were observed to be possibly a source of gas evolving reactions during the heat treatment procedures for the superconducting phase formation. A method that allows the temperature controlled detection of CO₂ resulting from reactions of various carbon species was developed based on an commercial C/H₂O-analyser with IR gas detectors. By means of this method it is possible to relate the carbon content to the conditions of synthesis and technological steps of the tape production. The phase formation mechanism of the superconducting (Bi,Pb)2223 phase from a multiphase precursor strongly depends on its elemental composition. Titrimetric and ICP spectrometric methods that allow the determination of the content of the main components Bi, Pb, Ca, Sr, and Cu with high precision and accuracy were developed and their results were compared. The best results were obtained with a combined chemical-spectrometric procedure. The relative standard deviations (RSD) for all metallic elements do not exceed 1%. The analytical results of the main components and specific trace determinations are essential for the functioning of superconducting tapes.     

X-Ray Emission from Thin Films on a Substrate – Calculation and Experiments

 Monte Carlo simulation of electron transport in solids is widely used in electron microscopy, spectroscopy and microanalysis. The reliability of physical models incorporated in a Monte Carlo code is usually checked by comparing with experimental results. Elastic or inelastic collisions are usually considered as the basic interactions of electrons with atoms. In our Monte Carlo code the single scattering model is employed for simulation of X-ray emission from thin films of Au on the Si substrate. The electron beam energy was in the range 10–30 keV, the take-off-angle was 40°. The simulated values of X-ray production were calculated in our Monte Carlo code using several models of ionisation cross-sections. For the emitted intensities the depths of inelastic collision and X-ray absorption were taken into account, then the k-ratios were calculated. These data were compared with experimental values of k-ratios calculated from X-ray intensities of Au M and Au L characteristic lines. We followed mainly the dependence of the k-ratios of the film element on film thickness. The film thickness was in the range 0.05–1 μm. Reasonably good agreement was found for dependences of X-ray intensity on film thickness in the whole energy range and for both lines, especially for Powell’s model of the ionisation cross-section.     

Particle Analysis by SEM/EDXS and Specimen Damage

 Quantitative analysis of particles, especially environmental particles in the submicron region, is hampered mainly by radiation damage. It can already be observed for probe currents smaller than 1 nA and analysis times of 10 seconds. The main reason for radiation damage is the storage of thermal energy in the particle, until the melting temperature is reached, and the subsequent loss of one or more of the elements of the respective material, e.g. SO_x in K₂SO₄. The lower the melting point, the more severe the specimen damage. The amount of specimen damage can vary substantially even for particles of the same size and composition. Specimen damage on inorganic materials can be observed for energies as low as 1 keV. Thus radiation damage is the greatest obstacle to accurate quantitative analysis for particles in the submicron region, even for analysis times as low as those used in automated particle analysis by CCSEM/EDXS.     

XRF Analysis of Microsamples of Semiconductor Type Multielement Materials by the Thin Layer Method. Determination of Cr, Co, Ni, Cu, Zn, Ga, Se, Sb, Yb

 A simple and quick method of durable samples preparation by the thin layer method through direct digesting of the analysed material on the substrate has been presented. Four- and three-component mono- and polycrystals have been analysed. Standards have been used in calibration containing: Cr, Co, Ni, Cu, Zn, Ga, Se, Sb, Yb. To improve the correlation between the concentration and the fluorescent radiation models of mathematical corrections have additionally been used: multiple linear regression, Lucas-Tooth-Pyne model (L. T. P.) and de Jongh model (d. J.). Statistical parameters: detection limits for 0.5 mg samples: Cr–0.041%, Co–0.034%, Ni–0.042%, Cu–0.053%, Zn–0.054%, Ga–0.057%, Se–0.057%, Sb–0.113%, Yb–0.077%. Correlation coefficients: simple regression 0.9946–0.9997, multiple regression 0.9974–1.0000, L. T. P. 0.9993–1.0000, d. J. 0.9995–1.0000. Received August, 1, 1998. Revision March 25, 1999.     

Monitoring Fibre Surfaces with XPS in Papermaking Processes

 Recent instrumental advances have vastly improved the analysis power of X-ray photoelectron spectroscopy (XPS), which has been widely used in applied surface research for decades. In this presentation a set of XPS analysis methods well suited for problems and analytical needs encountered in papermaking technology is presented. The emphasis will be on analysis of pulps and non-coated papers. Examples given describe the use of XPS in quantification of surface lignin and extractives; an alternative approach for evaluating elemental surface distributions via the Tougaard background analysis is also presented. The experimental work and interpretations presented are based on more than two thousand XPS analyses performed at Helsinki University of Technology during 1996–2000. With strictly standardised experimental setup, state-of-the-art instrumentation and a proper combination of analysis methods XPS can yield valuable and consistent information on surface properties of natural fibers.     

Oxidation, Diffusion and Segregation in CuNi(Mn) Films Studied by AES

 The surface and in-depth compositions of sputter-deposited Cu_0.57Ni_0.42Mn_0.01 thin films were studied by Auger electron depth profiling after thermal treatment. The samples were thermally cycled to maximum temperatures of 300 °C to 550 °C in air, argon and forming gas (N₂, 5 vol. % H₂). Linear least-squares fit to standard spectra and factor analysis were applied to separate the overlapping Auger transitions of Cu and Ni. Under bombardment by 4 keV argon ions, CuNi(Mn) layers display bombardment-induced surface enrichment of Ni in the same extent as binary CuNi alloys. At sufficiently high oxygen partial pressures, a duplex oxide layer is formed and a thick surface copper oxide overgrows the initial nickel oxide. In reducing atmosphere selective oxidation of manganese takes place. A capping NiCr layer prevents CuNi(Mn) from being oxidized, but the film configuration is degraded with increasing annealing temperature due to formation of a surface chromium oxide and diffusion of Ni from the CuNi(Mn) layer into the NiCr/CuNi(Mn) interface.     

Pt／Ti／Si3N4／SiO2／Si基底的多层薄膜制备及拉曼研究

选用三水醋酸铅、乙酰基丙酮酸锆、四异丙氧基钛、乙酰丙酮作初始材料,用同样的方法分别制备了锆钛酸铅（PZT）和钛酸铅（PT）两种固体前驱物．采用改良型的溶胶-凝胶工艺技术,分别在不同的Pt-Ti-Si3N4-SiO2-Si基底上,按照不同的组合方式,制备了三种多层薄膜：PZT、PT／PZT—PZT／PT、PT／PZT／-／PZT／PT．较详细地讨论了薄膜制备的工艺技术,发现当凝胶通过烧结和干燥后变成固态物质时,薄膜内部存在着较大的残余应力,当薄膜在600℃下退火时其内部残余应力可以被减小．通过拉曼衍射和XRD分析,发现PT／PZT—PZT／PT结构的薄膜具有较好的结晶性和较小的残余应力．XRD分析表明,多层混合薄膜的衍射峰是PZT和PT两种薄膜衍射峰的叠加．     

EFTEM and EELS Analysis of a Pt/NiO Interface

 Energy-filtering transmission electron microscopy (EFTEM) is more and more becoming an important nanoanalytical technique in both materials science and biology. The main advantage of the method lies in the possibility to obtain two-dimensional chemical information from large specimen areas as well as from features on a nanometer scale. Due to its excellent lateral resolution it is perfectly suited for the investigation of nanometer sized features (e.g. interfaces). In this paper we will show how EFTEM can be used to characterize the interface between a Pt layer and a NiO crystal as part of a coulometric titration cell. In addition to elemental distribution maps electron energy-loss spectra (EELS) across the interface (EELS linescans) have been acquired to obtain quantitative compositional profiles. By employing these methods the following interfacial layers could be identified, all of which containing Pt, Ni and O in different proportions: 13 nm Pt-rich, 32 nm Ni-rich and 29 nm Pt-rich. The origin of these is discussed in terms of displacement reactions.     

Role of Layer-by-Layer Deposition on Electrical and Optical Properties of PEDOT: PSS/Polyaniline Thin Films for Solar Cells

In this article, electrical and optical properties of PEDOT:PSS/Polyaniline: (PANI)bilayer thin films deposited on indium tin oxide (ITO) are reported. Spin coater has been used for fabrication of thin films of 40–50 nm thickness at 5000 rpm. The deposited thin films have been characterized by using Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), UV-vis spectroscopy and Keithley electrometer. Layer-by-layer (LBL) technique has been shown to produce electroactive polymer films with low roughness, excellent uniformity, and high electrical conductivity for heterojunction solar cells. The electrical response of fabricated films showing ohmic behavior for PEDOT: PSS/PANI thin films.     

Ion-Pair Formation in Pharmaceutical Analysis. Conductimetric Determination of Promazine, Chlorpromazine, Promethazine, Imipramine and Ciprofloxacin Hydrochlorides in Pure Form, Drug Formulations and Urine

 Potassium ferricyanide and sodium tetraphenylborate were used as titrants for the conductimetric determination of promazine HCl, chlorpromazine HCl, promethazine HCl, imipramine HCl and ciprofloxacin HCl through ion-associate complex formation. The molar combining ratio, effects of dilution of titrant, temperature and solvent were studied. The accuracy of the method is indicated by excellent recovery (99.50–99.96%). The sensitivity of the proposed method is discussed and the results are compared with the pharmacopoeial or the official methods. The suggested method has been applied for the analysis of the mentioned compounds in their pharmaceutical formulations and urine. Received March 1, 1998. Revision May 31, 1999.     

Quantitative Analysis of Ti-Si-Ge/Si-Ge/Si Structures by EDS and AES

 A method for quantitative analysis of Ti-Si-Ge/Si-Ge/Si structures with submicron thick layers by energy dispersive spectroscopy (EDS) in transmission electron microscopy (TEM) and Auger electron spectroscopy (AES) was developed. Quantitation of the results of both AES and EDS techniques was performed on the basis of a single reference specimen for the Ti-Si-Ge system comprising a uniform layer of the Ti(Si_0.85Ge_0.15)₂ phase on a silicon substrate. The reference sample was prepared by the same procedure as the samples used in the study, and was thoroughly characterized by X-ray diffractometry, transmission electron microscopy and energy dispersive spectroscopy in scanning electron microscopy. Using this reference sample the elemental sensitivity factors relative to Si were found for both techniques, which enable us to obtain the elemental depth distributions for the studied samples. Good agreement between the results obtained by EDS/TEM, AES and supplementary techniques was found.     

Assessment of Four Inter-Comparison Exercises in Organic Elemental Analysis

 Four inter-comparison exercises on organic elemental analysis were carried out between 1997 and 2001 by the Department of Analytical Chemistry of the University of Barcelona, together with the Microanalysis Service and the Institute of the Marine Sciences, which both belong to the CSIC in Barcelona, and the University of A Coru?a. More than sixty laboratories participated in these exercises. Here we describe the design and characteristics of the trials, the samples and the homogeneity tests applied. We report the results obtained for the analysis of carbon, hydrogen, nitrogen, sulphur and oxygen, their statistical analysis, and the most relevant aspects of the technical discussion meetings. Received December 20, 2001; accepted March 18, 2002; published online July 22, 2002     

A new Fluorimetric Reagent for Highly Selective and Sensitive Determination of Terbium Ion

 In this work, a new ligand, 2,9-bis[N,N-bis(carboxymethyl)-aminomethyl]-1,10-phenanthroline (BBCAP), was synthesized and used to establish a novel fluorimetric method for the determination of trace amounts of terbium in a binary system. Its luminescence mechanism was studied. The excitation and emission wavelengths are 284 nm and 547 nm, respectively. Other rare-earth metal ions in 100-fold excess caused no interference. The fluorescence intensity was a linear function of the concentration of terbium in the range of 5.0 × 10⁻¹⁰–1.0 × 10⁻⁶ mol/L. The detection limit was 2.0 × 10⁻¹¹ mol/L (n = 12). The standard addition method was used to determine the terbium in a synthetic rare-earth sample with satisfactory results. This method represents a direct, rapid, selective and sensitive analytical procedure with a widely linear range. Received November 29, 2001 Revision February 9, 2002     

Development and Application of Instrumental Methods for Strain Analysisof Semiconductor Layers and Devices

 Strain effects on semiconductor layers were studied by means of optical spectroscopic techniques with a device developed especially for the study of layered structures and microstructures. Raman, modulated photoreflectance and reflectance anisotropy spectroscopy (RAS) were applied. Measurements were performed on elemental semiconductors (Si), semiconductor alloys (Si–Ge) and III–V semiconductor compounds (GaAs). By application of RAS, strains lower than 10⁻⁴ could be resolved, which is at least one order of magnitude lower than those observable with Raman and modulated reflectance techniques. The RAS spectra of layers strained along either the [010] or [011] direction showed a derivative-like structure at E₁-gap energies, which increased linearly and very quickly with increasing strain. The dependence of this spectral feature on applied strain was used to evaluate strain-dependent effects. This behaviour strongly suggests that RAS can be applied for the optical characterisation of strain in semiconductor microstructures and devices, with a higher efficiency and accuracy than that achieved by previously established optical methods such as Raman and modulation spectroscopy. In addition, the compactness and ease of operation of the instrumentation of RAS provides considerable potential for in situ monitoring/control of semiconductor fabrication conditions.     

Two-Phase Aqueous Extraction of Chromium and its Application to Speciation Analysis of Chromium in Plasma

 This work proposes a new extraction method for chromium based on the two-phase aqueous system isopropyl alcohol-ammonium sulfate-ammonium thiocyanate (i-PrOH-(NH₄)₂SO₄-NH₄SCN), and the related experimental conditions are optimized. The results show that chromium (III) can be quantitatively extracted under the selected conditions: 4 mL of i-PrOH, 200 μL of 2 mol/L sulfuric acid, 1 mL of 4 mol/L NH₄SCN and 3 mL of saturated (NH₄)₂SO₄ solution (V_total=10 mL). Application of the proposed method to speciation analysis of plasma chromium was also investigated and satisfactory results were obtained. Received May 22, 1999. Revision November 8, 1999.