Richard E. Gilbert

Computer‐interfaced digital pulse counting circuit

An electronic circuit is presented which can be used in digital pulse counting applications such as ESCA, Auger spectroscopy, UPS, etc. It consists of a quartz crystal clock and integrated circuits, and can be interfaced easily to a laboratory computer through a parallel board. A modification allows this circuit to be used as a counter with a time delay, thus making it useful in applications involving time‐of‐flight mass spectrometry.

TPD and ESD studies of the interaction of hydrogen and oxygen on polycrystalline zirconium

Temperature programmed desorption (TPD) and electron stimulated desorption (ESD) have been used to study the interaction of hydrogen and oxygen on a polycrystalline zirconium surface. ESD and TPD features due to hydrogen bonding directly both to oxygen and to Zr are identified. Deuterium adsorption studies reveal that the presence of an oxide layer retards hydrogen adsorption but that the oxygen attracts bulk hydrogen forming a hydroxylated surface oxide layer.

An investigation of the interaction of polycrystalline zirconium with O2, N2, CO, and N2O. Part I

The adsorption of O2, N2, CO, and N2O on polycrystalline zirconium has been studied using ESCA and AES over a wide temperature range from room temperature to nearly the melting point of zirconium. The gases adsorb dissociatively at all temperatures studied, and the room temperature sticking coefficients are low (<0.01). Heating causes migration of the adsorbate species into the bulk zirconium. Two distinct surface phases (states) of zirconium are identified. State 1 exists when the sample has not been heated above the hcp↔bcc transition temperature of 1135 K for prolonged periods while state 2 occurs after prolonged heating (the time is a function of temperature) above the transition temperature. The AES spectra and chemisorption properties of the two states are very different. State 1 AES spectra show a prominent 175 eV peak which is nearly gone in state 2 AES spectra. State 1 readily adsorbs CO and N2 at room temperature while state 2 adsorbs relatively small amounts of CO and is almost inert to N2. The...

The interaction of O2 and CO with polycrystalline Zr

This study examines (1) the production of a clean polycrystalline surface, (2) oxygen adsorption as a function of room‐temperature exposure using ion scattering spectroscopy (ISS), Auger electron spectroscopy (AES), and electron spectroscopy for chemical analysis (ESCA), and (3) CO adsorption. S and Cl are typical contaminants which modify the chemisorption properties of a Zr surface. However, they are difficult to detect using AES or ESCA but are readily observed using ISS. Sputtering a hot Zr surface provides an excellent method for producing a contaminant‐free surface. The adsorption of oxygen proceeds in a stepwise fashion by rapidly populating sites in the outermost surface layer, filling subsurface sites and then forming a multilayer oxide film even at room temperature and low O2 pressure (10−6 Torr). CO adsorbs dissociatively on Zr at room temperature. An oxide overlayer is formed which contains no C. The C lies beneath the oxide layer in a chemisorbed or interstitial form. Heating converts this C ...

A characterization study of platinum-tin oxide films supported on Al2O3

Abstract Films which are about 20 A thick containing platinum and tin oxide were produced by impregnating γ-Al 2 O 3 in an acetone solution containing stannic chloride and chloroplatinic acid. Electron spectroscopy for chemical analysis, Auger electron spectroscopy, temperature-programmed decomposition and depth profiling were used to characterize these films after oxidation in air at 725 K and after reduction in hydrogen at 1 atm and 775 K. Both CO and H 2 O are incorporated in these films but in different relative amounts in the oxidized and reduced samples. The desorption characteristics also differ between the oxidized and reduced samples, but H 2 O and CO desorb simultaneously from each type of sample. Electron spectroscopy for chemical analysis shows that the interaction between the platinum and tin is through a Pt-O-Sn bond which is present in both oxidized and reduced samples. Reduction converts PtO and PtO 2 to metallic platinum and causes sintering of platinum crystallites to bulk-like platinum.

The interaction of hydrogen with polycrystalline zirconium: II. The effect of preadsorbed oxygen

Abstract An investigation into the low temperature (300 to 1000 K) behavior of the hydrogen/polycrystalline zirconium system has revealed an interesting binding state for hydrogen which has a desorption temperature of 500 K. This state involves surface oxygen, believed to be in the form of hydroxyl groups. Furthermore, the surface oxygen appears to attract hydrogen from the metal, suggesting a low energy path for the removal of hydrogen from zirconium.

An investigation of the interaction of polycrystalline zirconium with O2, N2, CO and N2O. II: Pretreatment effects on O2 chemisorption properties

Abstract The chemisorption of oxygen at room temperature on polycrystalline zirconium has been studied using AES and ESCA as a function of sample pretreatment. It is shown that annealing at high temperature greatly reduces the ability of zirconium to chemisorb oxygen but that its activity can be restored by argon-ion bombardment. This suggests that chemisorption may be site specific and that the concentration of these sites can be manipulated by varying sample pretreatment.

The interaction of hydrogen with polycrystalline zirconium: I. Sticking coefficients and binding states

Abstract Values for the sticking coefficient of hydrogen on polycrystalline zirconium have been obtained using a computer-controlled flash desorption technique. Sticking coefficients exhibit a maximum of about 6.5 × 10 -4 near 700 K and fall to about 4 × 10 -5 below 350 K and above 1000 K. Such low values are surprising in view of the well-known effectiveness of zirconium as a “getter” material for hydrogen. Plots of desorption rate versus temperature show two binding states below the phase transition temperature and at least one (and possibly two) above that temperature.

A method for rapid collection of high‐energy‐resolution Auger electron spectroscopy data: The digital‐derivative‐generation technique

A new technique for collecting Auger electron spectroscopy (AES) spectral data, referred to as the digital‐derivative‐generation technique, is presented. The function of the lock‐in amplifier is performed with the computer. Data are collected in the dN/dE mode and then integrated to produce N(E) spectra. The technique offers high speed and high energy resolution making it attractive for obtaining chemical state information from AES. No artifical smoothing of the AES data is required beyond that which is inherent in the integration process. Transients in the system are reduced to submillisecond intervals so that data may be taken intermittently. This feature is useful for performing AES at elevated temperatures or time‐resolved AES.