W. E. Baitinger

ESCA studies of metal-oxygen surfaces using argon and oxygen ion-bombardment

Abstract ESCA has been used to monitor alterations of catalytically and electrochemically important metal-oxygen surfaces following exposure to Ar + and O 2 + ion bombardment. This treatment resulted not only in sputtering, but also, in many cases, in reduction to the corresponding metal or lower oxide. A model based on bulk thermodynamic free energy considerations Is proposed to explain this phenomenon. We have also exploited this approach to obtain an in-depth concentration profile of various oxidation states of an element, to selectively prepare desired surface oxide compositio and to aid in interpreting complex O ls spectra. Results obtained from metal-oxygen surfaces for Ni, Ru and Mo are presented. Ni 2 O 3 and RuO 3 , which are gross defect structures of the bulk species, are present on NiO and RuO 2 respectively, with the former being confined to the surface layers. The MoO 2 , on the other hand, is covered with a surface layer of MoO 3 present as a regular crystal structure.

Soft landing of ions as a means of surface modification

Abstract Chemical reactions between low energy mono-, di- and triatomic ions and metal targets lead to products which have been examined using ESCA. The nature, charge state and kinetic energy of the reactant ion all cause changes in the ESCA spectra. Results for the reactions of lead with various sulfur-containing ions (CS2+, CS22+, CS+, S+, S2+) are emphasized. A complex chemistry is involved with the sulfur being present in at least three charge states characteristic of the metal sulfide, elemental or organic sulfur and sulfur in positive oxidation states, respectively.

X-ray photoelectron spectroscopic studies of PbO surfaces bombarded with He+, Ne+, Ar+, Xe+ and Kr+

Abstract The surface composition of PbO has been studied with X-ray photoelectron spectroscopy after bombardment with several inert gas ions of 400 eV. The results show reduction of PbO to metallic Pb with the degree of damage following the order He+ > Ne+ >Ar+. Both Kr+ and Xe+ did not reduce the oxide. The depth of damage varied from ≈9 A for He+ to ≈1 A for Ar+ bombardment. The results were compared to a collisional and a thermal model of the sputtering process.

The study of meta-stable positive ions with a double-focussing mass spectrometer: Part I. Description of the instrument used and its performance

Abstract The instrument used in these studies is the RMH-2 mass spectrometer, of Nier-Johnson geometry having 70° electrostatic and magnetic sectors with an ion radius of 500 mm in the electric and 400 mm in the magnetic sectors. When operated at 10 kV a resolving power of 90,000 has been obtained. Typical energy profiles of the ion beam at 5 kV energy are shown having widths at half-height of ±0.26 V. The focussed ion beam at the source slit is about 0.08 mm wide. Curves obtained when the accelerating voltage is scanned at fixed electric sector voltage show a “third” field-free region in this instrument in which decomposition of meta-stable ions can be studied.

The ion kinetic energy spectrum and the mass spectrum of argon

Abstract The technique of Ion Kinetic Energy Spectroscopy (I.K.E.S.) is described and results obtained with a sample of argon gas are discussed. When coupled with conventional mass spectroscopy, the technique enables the route to formation of the ions in the mass spectrum to be deduced. It can provide information on unimolecular or collision-induced decompositions of meta-stable ions. Its application to the study of the reactions of high-kinetic energy argon ions with nitrogen molecules is described.

Building mass spectrometers and a philosophy of research

Development of the techniques of ion kinetic energy spectrometry and mass-analyzed ion kinetic energy spectrometry is described. The extension of these concepts to the method of tandem mass spectrometry for direct mixture analysis is traced, and a rationale for the construction of hybrid mass spectrometers is presented. Collisions of polyatomic ions with surfaces are discussed as an outgrowth of gaseous collisions. An attempt is made to describe a philosophy of research that guided the construction of a dozen mass spectrometers and the exploration of organic ion chemistry in as many contexts.

System for transferring samples between chambers in UHV

This system provides right angle or end‐on transfer of a sample holder from one chamber to another at ultrahigh‐vacuum conditions. A convenient mechanical coupling and uncoupling device and magnetically driven transfer rods allow movement of the sample‐holder assembly over distances up to 150 cm. The room‐temperature holder accommodates two samples. The heatable assembly includes contacts for resistive heating of the sample to temperatures above 1800 K and thermocouple reading of sample temperatures.

Detection of high mass cluster ions sputtered from Bi surfaces

Abstract The technique of secondary ion mass spectrometry (SIMS) has been employed to detect Bi + 3 ions and associated oxides Bi 3 O + x ( x ≈ 1 to 4) from a Bi foil. Using a 3 keV Ar + ion primary beam of 5 × 10 −7 A/cm 2 , mass resolution to nearly 700 with the requisite sensitivity has been achieved. The Bi surface was also monitored by X-ray photoelectron spectroscopy (XPS or ESCA). The presence of a weak O 1s peak at 532.7 eV and a strong SIMS Bi + 3 peak is interpreted to mean that the oxygen is weakly incorporated into the Bi lattice without disrupting metalmetal bonds.

The study of meta-stable positive ions with a double-focussing mass spectrometer: Part II. Methods used to study “meta-stable peaks” and the sensitivity achieved with a toluene sample

Abstract The sensitivity of the model RMH-2 mass spectrometer for the study of decompositions of meta-stable ions is illustrated in the case of toluene. “Meta-stable peaks” corresponding to about 1 or 2 p.p.m. of base peak intensity can be detected. A method for scanning the mass spectrum with fixed ion accelerating voltage at a series of pre-selected electric sector voltages is described and its advantages discussed. This has enabled many new decomposition processes to be detected.

Instrument combining x‐ray photoelectron spectroscopy and secondary ion mass spectrometry for surface studies

X-ray Photoelectron Spectroscopy (XPS) or (ESCA) and Secondary Ion Mass Spectrometry (SIMS) have been combined in the same ultrahigh vacuum system to facilitate a new approach to studying clean and reacted surfaces. The design philosophy is to connect two satellite vacuum systems via a set of magnetically driven sample transfer devices. The advantages and capabilities of this approach are discussed with respect to its flexibility and its ability to couple to other surface techniques. XPS and static SIMS spectra of an oxidized polycrystalline indium film are presented to exemplify the type of information which can be gleaned from a multitechnique investigation of surfaces. The additional ability to prepare sample surfaces in our system by ion implantation is demonstrated by a positive-ion SIMS analysis of a gold-implanted aluminum foil.