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5009. Chemical effects in ion scattering spectroscopy
Classified abstracts 5005-5012 boards. Although no visible contamination can be seen on the surface of the gold, poor bonding or high contact resistance frequently occurs. It has been assumed that some grain boundary diffusion of nickel has been occurring through the 2 pm gold film. A scanning Auger microanalysis was conducted on the surface and in depth on the thin film structure before and after heating at 300°C for 4 h. Two-dimensional Auger analysis, after heating, showed the nickel to be distributed along the grain boundaries on the surface of the gold film. Subsequent Auger depth profiling showed the nickel layer to be oxidized and approximately 50 A in depth. This characterization has led to improved understanding of the bonding problems and variation of contact resistance with this metallization system. T E Brady and T Hovland, J Vat Sci Tech&, 18 (2), 1981, 339-342. 37 5005. X-ray photoelectron and Auger analysis of thin films. (USA) X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES) are two of the most powerful materials analysis techniques available today. First, the fundamental concepts underlying these methods are presented in simplified form. Then the most important problem areas of concern to workers in these fields are examined. These are: radiation damage, the technology of ion milling, and quantitative analysis. The complexity of these areas is illustrated from what is already known, and some problems that arise in areas that are still incompletely understood are discussed. Finally, the relative merits of XPS and AES are considered by evaluating the performance of each technique with respect to: (1) sensitivity, (2) speed, (3) spatial resolution, (4)depth resolution, (5) chemical bonding information, (6) sample damage, (7) quantitative analysis, and (8) electrostatic charging problems. Scores have been assigned for each of these 8 criteria for XPS and AES; at present, AES is found to have a significantly higher total score. These criteria have also been evaluated assuming that all the theoretical limits can be attained. In that limit, some problems are expected to remain for AES with respect to sensitivity, chemical bonding information, damage, and charging; however, with XPS, all of the performance criteria become superior to AES except for spatial resolution. The total Performance score for XPS then becomes much higher than for AES. C C Chang, J Vat Sci Technol, 18 (2), 1981, 276-281. 37 5006. Studies of surface, thin film and interface properties by automatic spectroscopic ellipsometry. (USA) This paper qualitatively describes the principles and presents some applications of the rapidly developing technique of automatic spectroscopic ellipsometry, as applied to the analysis of the properties of surfaces and interfaces of materials in bulk or thin film form. Examples include composition and density measurements of polycrystalline and amorphous Si films, the determination of the bestquality surfaces of bulk materials, oxidation of Si, optical profiling of microscopic surface roughness, determination of interface widths in semiconductor-oxide systems and CVD heterostructures, and nucleation of c&i films. D E Aspens, J Vat Sci Technol, 18 (2), 1981, 289-295. 5007. Characterization of thin films for laser systems analytical techniques. (USA)
wing
37 surface
High performance laser systems require dielectric thin film coatings applied to optical components in order to satisfy various functional requirements such as polarization suppression, wavelength selection, and specular reflection enhancement. In addition to high incident radiation levels, these coatings are sometimes subjected to uv radiation and active gasses, i.e., HF/DF mixtures for 2.5 to 4.1 pm laser systems. Thorium tetrafluoride and zinc sulfide coatings in particular have been found to degrade with time and exposure. This degradation is analysed by means of Scanning Auger Microscopy, X-ray Photoelectron Spectroscopy, Secondary Ion Mass Spectroscopy, and Secondary Electron Microscopy. The validity of these types of analyses is demonstrated. Investigations reveal several defects and abnormal oxygen content in these coatings which may eliminate these materials from further use in high energy laser applications and other systems which require durability and sustained performance. T W Humpherys et al, J Vat Sci Tech&, 18 (2). 1981, 296300. 37 5508. Fourier analysis of linear surface kinetics in reactive molecular beam scattering. (USA) The surface kinetics of reactive molecular beam scattering have been analysed by discrete Fourier analysis of the scattered product waveform. In experiment and by calculation, it has been shown that with square wave 222
modulation, harmonics in the scattered waveform as high as 29 can be significant. These harmonics can be used to characterize the transfer function of linear surface kinetics with modulation at four or fewer frequencies. Optimum signal-to-noise in the derived rate parameter is obtained using the phase shift of the first harmonic where K/o is approximately one. Fourier waveform analysis of square wave modulation compares favourably with lock-in amplifier detection, cross correlation modulation, and pulse testing for the analysis of surface kinetics. H H Sawin and R P Merrill, J Vat Sci Tech&, 19 (1). 1981, 40-46. 37 5009. Chemical effects in ion scattering spectroscopy. (USA)
The principal use of low-energy ion scattering spectroscopy (ISS) as a surface analytical tool has been the identification of surface layer atoms through binary collision kinematics. In this mode of analysis, the chemical state of the atom is usually not discernible with data normally obtained. This paper reviews a number of observations which indicate that chemical state information or the nature of local atom arrangements may be inferred from certain aspects of the experimental data. The earliest recognition of chemical state information resulted from study of resonant charge exchange processes for particular ion/atom combinations. By appropriate manipulation of experimental data, it is possible to obtain fingerprint spectra in the inverse velocity domain for various compounds. Recently, two techniques used in this laboratory have been applied to the study of surface atom configutations. In the first, the energy dependence of scatter peak height ratios in ionic compounds is used to infer an atom shielding susceptibility for various cations in oxide matrices. Secondly, a number of peak shift and doublet scattering peaks have been observed in special cases where the surface layer decomposes under bombardment by the probe ion beam. R C McCune, J Vat Sci Technol, 18 (3). 1981, 700-708. 37 5010. Molecular secondary ion mass spectrometry
(SIMS). (USA)
Ion beams have been used for a number of years in material analysis. SIMS has been used recently to study the interaction ofadsorbed gases on metal surfaces and the molecular structure of organic, inorganic, biologic, and polymeric compounds. This paper reviews the advancing field of molecular SIMS applied in two distinct areas: as an analytical tool for surface analysis and as a sensitive ionization source for nonvolatile and thermally-labile molecules. The present understanding of the molecular ion formation process is illustrated by results of calculation and experiment. Comparison of SIMS with other new ionization methodologies in mass spectrometry such as field, plasma, and laser desorption shows clear spectral similarities. In addition, SIMS demonstrates an extreme surface sensitivity, best detection limits in the picogram range, and high mass capability (z 5000 amu). Ionization of nonvolatile and thermally labile molecules can occur via three separate processes involving cationization/anionization, electron transfer, or direct sputter emission of positive and negative secondary ions. Over 80 papers are referenced. R J Colton, J Vat Sci Tech&. 18 (3), 1981, 737-747. 37 5011. Intrinsic secondary ion emission bombardment. (USA)
from binary alloys dnring Ar+
The emission of positive atomic secondary ions from single phase binary alloys during 15 keV Ar+ bombardment was studied in an ultrahigh vacuum environment. For all the five alloy systems: Fe-Ni, Cu-Ni, Pd-Ni, AI-Ni, and Si-Ni, the ionization probabilities of the elements show little or no correlation with the bulk alloy density of states or the local density of states near the Fermi level. When the ionization probabilities are compared with the electronegativity differences of the elements, we notice that only the emission of Al’ and Ni+ from AI-Ni alloys seems to follow the direction of the anticipated charge transfer. M L Yu and W Renter, J Vat Sci Tech&, 18 (2). 1981, 57@573. 37 5012. Secondary ion mass spectrometry and Rutherford backscattering spectroscopy for the analysis of thin films. (USA)
The merits and limitations of SIMS and RBS are discussed stressing the complementary nature of the information generated by these techniques. After a brief discussion of the physics of these techniques, their capabilities are compared with respect to: Mass resolution, quantitative interpretation and sensitivity, probing depth and depth resolution, and resolution, sample conductivity, sample damage, structural information and information on chemical bonding. W Renter and J E E Baglin, J Vat Sci Technol, I8 (2), 1981, 282-288.
wing
37 surface
High performance laser systems require dielectric thin film coatings applied to optical components in order to satisfy various functional requirements such as polarization suppression, wavelength selection, and specular reflection enhancement. In addition to high incident radiation levels, these coatings are sometimes subjected to uv radiation and active gasses, i.e., HF/DF mixtures for 2.5 to 4.1 pm laser systems. Thorium tetrafluoride and zinc sulfide coatings in particular have been found to degrade with time and exposure. This degradation is analysed by means of Scanning Auger Microscopy, X-ray Photoelectron Spectroscopy, Secondary Ion Mass Spectroscopy, and Secondary Electron Microscopy. The validity of these types of analyses is demonstrated. Investigations reveal several defects and abnormal oxygen content in these coatings which may eliminate these materials from further use in high energy laser applications and other systems which require durability and sustained performance. T W Humpherys et al, J Vat Sci Tech&, 18 (2). 1981, 296300. 37 5508. Fourier analysis of linear surface kinetics in reactive molecular beam scattering. (USA) The surface kinetics of reactive molecular beam scattering have been analysed by discrete Fourier analysis of the scattered product waveform. In experiment and by calculation, it has been shown that with square wave 222
modulation, harmonics in the scattered waveform as high as 29 can be significant. These harmonics can be used to characterize the transfer function of linear surface kinetics with modulation at four or fewer frequencies. Optimum signal-to-noise in the derived rate parameter is obtained using the phase shift of the first harmonic where K/o is approximately one. Fourier waveform analysis of square wave modulation compares favourably with lock-in amplifier detection, cross correlation modulation, and pulse testing for the analysis of surface kinetics. H H Sawin and R P Merrill, J Vat Sci Tech&, 19 (1). 1981, 40-46. 37 5009. Chemical effects in ion scattering spectroscopy. (USA)
The principal use of low-energy ion scattering spectroscopy (ISS) as a surface analytical tool has been the identification of surface layer atoms through binary collision kinematics. In this mode of analysis, the chemical state of the atom is usually not discernible with data normally obtained. This paper reviews a number of observations which indicate that chemical state information or the nature of local atom arrangements may be inferred from certain aspects of the experimental data. The earliest recognition of chemical state information resulted from study of resonant charge exchange processes for particular ion/atom combinations. By appropriate manipulation of experimental data, it is possible to obtain fingerprint spectra in the inverse velocity domain for various compounds. Recently, two techniques used in this laboratory have been applied to the study of surface atom configutations. In the first, the energy dependence of scatter peak height ratios in ionic compounds is used to infer an atom shielding susceptibility for various cations in oxide matrices. Secondly, a number of peak shift and doublet scattering peaks have been observed in special cases where the surface layer decomposes under bombardment by the probe ion beam. R C McCune, J Vat Sci Technol, 18 (3). 1981, 700-708. 37 5010. Molecular secondary ion mass spectrometry
(SIMS). (USA)
Ion beams have been used for a number of years in material analysis. SIMS has been used recently to study the interaction ofadsorbed gases on metal surfaces and the molecular structure of organic, inorganic, biologic, and polymeric compounds. This paper reviews the advancing field of molecular SIMS applied in two distinct areas: as an analytical tool for surface analysis and as a sensitive ionization source for nonvolatile and thermally-labile molecules. The present understanding of the molecular ion formation process is illustrated by results of calculation and experiment. Comparison of SIMS with other new ionization methodologies in mass spectrometry such as field, plasma, and laser desorption shows clear spectral similarities. In addition, SIMS demonstrates an extreme surface sensitivity, best detection limits in the picogram range, and high mass capability (z 5000 amu). Ionization of nonvolatile and thermally labile molecules can occur via three separate processes involving cationization/anionization, electron transfer, or direct sputter emission of positive and negative secondary ions. Over 80 papers are referenced. R J Colton, J Vat Sci Tech&. 18 (3), 1981, 737-747. 37 5011. Intrinsic secondary ion emission bombardment. (USA)
from binary alloys dnring Ar+
The emission of positive atomic secondary ions from single phase binary alloys during 15 keV Ar+ bombardment was studied in an ultrahigh vacuum environment. For all the five alloy systems: Fe-Ni, Cu-Ni, Pd-Ni, AI-Ni, and Si-Ni, the ionization probabilities of the elements show little or no correlation with the bulk alloy density of states or the local density of states near the Fermi level. When the ionization probabilities are compared with the electronegativity differences of the elements, we notice that only the emission of Al’ and Ni+ from AI-Ni alloys seems to follow the direction of the anticipated charge transfer. M L Yu and W Renter, J Vat Sci Tech&, 18 (2). 1981, 57@573. 37 5012. Secondary ion mass spectrometry and Rutherford backscattering spectroscopy for the analysis of thin films. (USA)
The merits and limitations of SIMS and RBS are discussed stressing the complementary nature of the information generated by these techniques. After a brief discussion of the physics of these techniques, their capabilities are compared with respect to: Mass resolution, quantitative interpretation and sensitivity, probing depth and depth resolution, and resolution, sample conductivity, sample damage, structural information and information on chemical bonding. W Renter and J E E Baglin, J Vat Sci Technol, I8 (2), 1981, 282-288.