James S. Murday

Extracting Auger lineshapes from experimental data

Abstract A method is presented for extracting Auger lineshapes from an experimental, derivative Auger electron spectrum. The method involves removing the background after numerically integrating the derivative spectrum. This procedure is contrasted with the “dynamic background subtraction” method and similar methods which remove the background before integration. A treatment of electron energy loss is included. A functional form for the total electron emission for the Li salts of SO 4 3− and PO 4 3− is presented and compared to electron-loss data. Electron escape depth and spectrometer response corrections to the observed Auger signal are also considered. The S and P LVV Auger lineshapes are presented for the third row oxyanions, SO 4 2− PO 4 3− .

An interpretation of the Auger LVV transitions from oxides of third-row elements

Abstract The principal features in the LVV Auger spectra from the oxides of third-row elements are semi-empirically derived for the XO 4 n − species of Si, PS and Cl, and the XO 6 n − species of Mg and Al. Electron molecular orbital energies are derived from X-ray photoelectron and X-ray emission spectra; the central atom 3 p electron density of states is taken from the K β X-ray emission. Two principal peaks, separated by ca. 14 eV, are predicted for the central atom LVV Auger spectra and are experimentally confirmed for the XO 4 n − species. Similar features are observed in published spectra for oxides of Mg and Al. These peaks correspond to central atom 3 p electrons in orbitals whose energy is dominated by the atomic oxygen 2 s and 2 p electron levels. An examination of the total LVV line-shape shows that a self-convolution of the K β spectra does not reproduce the more subtle features, which are probably a result of the contributions of other electron orbitals and final-state effects. The possibility of using the LVV Auger spectra to discriminate between various oxide stoichiometries, i.e. sulfate, sulfite, etc., and between various ligand species, i.e. carbide, nitride, oxide, fluoride, is discussed.

Measurement of magnetic field gradient by its effect on the NMR free induction decay

Abstract The technique of measuring a magnetic field gradient from the FID signal of a right cylindrical sample is analyzed for sources of systematic error. The sources include the resonance condition, nonorthogonality of gradient and cylinder axes, time delays from electronic time constants and finite RF pulses, choice of signal baseline, menisci of the sample, background gradients, and inhomogeneities in the applied gradient. Corrections to reduce the errors are provided where possible.

Magnetic field sensing with magnetostrictive materials using a tunneling tip detector

Abstract This paper is a feasibility study for the design and construction of a magnetic field sensor using a tunneling tip as the detection system. In this experiment, a scanning tunneling microscope is used to measure dimensional changes of a short, thin amorphous FeBSi magnetostrictive ribbon exposed to d.c. and a.c. magnetic fields. A response of the system to a.c. magnetic fields was observed down to 0.020 G at a frequency of 1 Hz. The calculated sensitivity of the system can be near 10 −6 G if the vibrational stability of the device can be improved and if the demagnetizing field associated with short ribbons can be reduced. A mode of sensor operation involving the modulation of the tip-to-specimen separation is reported. Methods to improve the stability of the device are also discussed.

Auger Compositional Analysis of Ball Bearing Steels Reacted with Tricresyl Phosphate

The low-speed lifetime of steel ball bearings under boundary lubrication can be significantly extended by prior soaking in hot tricresyl phosphate (TCP). Auger electron spectroscopy (AES) and depth-profiling techniques were combined to monitor changes in the chemistry of 52100 bearing steel surfaces as a function of cleaning history and conditions of TCP exposure. Phosphorus was detected in the outer layer of all samples exposed to TCP; the length of TCP exposure beyond three days had minimal effect on the surface concentration of phosphorus but did increase its depth of penetration and alter its local chemical environment. When presoaked with conditions (15 days in TCP at 110°C) which lead to optimum bearing lifetimes (I), the steel developed a surface film comprising three distinct regions of different composition. The outermost region had 4–6 percent phosphorus where the phosphorus Auger signal shapes were consistent with those of a phosphorus-oxygen moiety. The innermost region resembled the oxide/met...

SIMS molecular cluster intensities of inorganic salts containing sulfur and nitrogen oxyanions

Abstract Secondary ion mass spectrometry (SIMS) is used to examine alkali sulfur oxyanion and nitrogen oxyanion salts. The secondary ion spectra, filtered about a nominal 1-eV kinetic energy, are measured in the dynamic SIMS mode using a 1—5 μA/cm 2 beam intensity of 1-keV Ar + primary ions. Charge build-up on the sample surface is neutralized by thermal electrons. The positive (+) secondary ion spectra are dominated by cation species (M + , MO + , M 2 + , M 2 O + ). The negative (−) secondary ion spectra include the anion central atom (A)—oxygen series (O − , A − , AO − , AO 2 − , AO 3 − , AO 4 − ). The relative ion intensity pattern of the (−) series shows a clear dependence on anion stoichiometry. For sulfur oxyanions and a 1-keV Ar + ion beam, the pattern can be represented by a modified Poisson distribution if dissociation of AO 4 t- and AO 3 − is assumed for sulfate and sulfite, respectively. The Poisson distribution mean values for oxygen loss are found to be 4.5 for sulfate and sulfite and 3 for thiosulfate. The mean value for loss increases with increasing Ar + ion energy in the range 0.5–2.0 keV. The nitrogen oxyanion intensifies are complicated by ion beam damage and by neutralization effects. Primary ion beam damage of the substrate is monitored by X-ray photoelectron spectroscopy (XPS).

Interpretation of the nitrogen KVV Auger line shape from alkali metal nitrates

Experimental N KVV Auger line shapes from sodium nitrate, produced by both x‐ray (XEA) and electron (EEA) excitation, are compared to theoretically derived line shapes based on populations derived from a GTO‐LCAO‐Xα model. The one‐electron orbital energies and valence line widths are determined from x‐ray emission and photoelectron data; the Auger matrix elements are determined from experimental gas phase atomic Auger data. The theoretical Auger energies include hole–hole repulsion and relaxation. Theoretical lines shapes using the local and the Mulliken Xα populations are generated, and a set of empirical populations are also determined. This work emphasizes the importance of shake‐off arising from creation of the initial core hole and its effect on the Auger line shape. A theoretical shake/Auger satellite line shape is generated and found to contribute up to 35% of the total intensity. The XEA and EEA line shapes (after correction for the sample and spectrometer transmission response) each show five fea...

Science and Technology of Nanostructures in the Department of Defense

The United States Department of Defense maintains a research and development program in nanostructures with special attention to miniaturization of information technology devices, nanostructured materials, and nanobiotechnology for detection of biological agents. This article provides a brief guide to those DoD funding officers and research scientists actively interested in nanostructures.

Proximal Probes: Techniques for Measuring at the Nanometer Scale

Abstract A new class of analytical tools, the proximal probes (so named because they depend on probe-to-sample proximity for their capability), are reviewed for their ability to determine the site-specific structure and chemical-physical properties of nanometer-sized structures. There are four types of proximal probes: tunnelling, field emission, force and near-field. The operating principles of each are identified, and their capabilities and limitations briefly discussed with copious references.

Surface Analysis of Bearing Steels After Solvent Treatments

Traces of surface contaminants on precision miniature instrument bearings in guidance and other critical systems can greatly contribute to the ultimate failure of such systems. Current solvent-cleaning procedures employed by Navy facilities to prepare bearings for assembly vary with respect to materials and methods, but the specific effects of these variations on the bearing surfaces are unknown. To critically examine these effects, reference surfaces of specially cleaned 52100 and 440C bearing steels were characterized by Auger electron and X-ray photoelectron spectroscopic analysis, as well as by wettability and infrared studies, subjected to standard sequential cleaning cycles and to individual solvents at several Navy facilities, and re-examined by the same techniques. The data indicated that various quantities of hydrocarbon, ester and other residues were deposited on the reference surfaces during the cleaning process. The results are discussed in terms of comparison of the types, levels and probable...