Edward N. Sickafus

Sulfur and carbon on the (110) surface of nickel

Abstract Auger electron spectroscopy has been used with low energy electron diffraction to determine the conditions giving rise to the appearance and/or disappearance of adsorbed sulfur and carbon on the (110) surface of nickel, and to correlate their presence with specific diffraction characteristics. In the case of these two elements it has been found that in situ surface cleaning techniques may remove one species while the other is subsequently increased. Heating at T > 400°C removes surface carbon but simultaneously increases surface sulfur, while Ar + bombardment removes sulfur but subsequent Auger analysis shows an increase in carbon. Both elements accompany diffraction anomalies in the Ni (110)-c (2 × 2) pattern in the vicinity of the centered spot of the basic Ni (110)-(1 × 1) pattern. Sulfur causes a splitting of the center spot in the (10) direction while carbon and/or sulfur cause a splitting in the (01) direction. In the absence of anomalous splitting a simple c(2 × 2) structure can be attributed to sulfur. The source of the sulfur is believed to be the bulk Ni while that of the carbon probably involves both the bulk and the ambient CO partial pressure. Carbon is removed from the surface at temperatures in excess of 450°C with a characteristic energy of 0.60 eV.

A secondary electron emission correction for quantitative Auger yield measurements

Abstract The Auger electron yield from the de-excitation of L 2,3 core holes of Cu is determined, in the approximation of isotropic emission, from the integral of the characteristic (elastic) Auger emission. The characteristic emission function is obtained from the secondary electron spectrum in two steps: First, the cascade background at a given Auger line is characterized accurately by the method of cascade linearization and subtracted. In the second step the resulting line is debroadened by an approximation to deconvolution debroadening. The concept of modulation stability is introduced as a criterion for credibility of the results of this analysis.

Specimen position effects on energy shifts and signal intensity in a single-stage cylindrical-mirror analyzer

Abstract Peak-height changes and energy shifts associated with small (Δ x = 0.1 mm) changes in specimen position in a single-stage cylindrical-mirror analyzer have been investigated. A specimen position for optimum signal strength is found experimentally and is predicted from theoretical calculations. An exact theoretical expression for signal intensity is presented in integral form. The integral has been evaluated numerically for finite aperture dimensions. It is found that the position dependence of signal intensity is a result of the finite size of the exit aperture and is not related to emission at the specimen or geometry of entrance aperture.

Ultrasonic wave interferometers

An acoustic or ultrasonic device includes two ultrasonic energy transmission paths having substantially identical transmission characteristics for a neutral condition of the device. One or both of the transmission paths include path altering structure(s) or coating(s) for changing the transmission characteristics of one or both of the paths in response to a physical phenomenon to be sensed or monitored. The paths have input transducers coupled thereto for transmitting ultrasonic energy into the paths. The input transducers are driven by a single oscillator such that the ultrasonic energy waves generated in the two paths are substantially identical to one another. A drive adjusting circuit compensates for any differences between the two paths and/or the ultrasonic waves in the two paths. An output transducer is coupled to the two paths for receiving ultrasonic waves from the paths and generating an output signal which is the result of combining the acoustic or ultrasonic waves from the two paths. By combining the waves from the two paths, the output signal is effectively the interference pattern generated by the waves in the two paths and hence the device operates as an acoustic or ultrasonic energy interferometer to sense or monitor physical phenomena to which the path altering structure(s) or coating(s) respond.

Self-consistent analysis of iVV-Auger fine structure

Abstract It is shown from the principles of the two-electron process in Auger-type transitions involving core-band-band excitations that a self-consistent set of guidelines can be developed for use in line-shape analysis. Three conditions derive from energy transformation considerations and two from the properties of the Auger convolution integral. It has been found that the use of such conditions is of considerable aid in the analysis of Auger fine structure for information such as chemical bond characteristics. It is recommended that these necessary constraints on the interpretation of Auger fine structure be considered to establish some credibility for fine structure analyses. Although complex structures may require a deconvolution analysis, it is evident that much can be learned about simple spectra from the other guidelines given herein.