Application of the Ion Bombardment Cleaning Method to Titanium, Germanium, Silicon, and Nickel as Determined by Low-Energy Electron Diffraction

Abstract

It should also be emphasiZed that rubber is not ideally elastic, especially in, the region of strain approaching breaking point, and the analogy with brittle fracture, although useful'in that it may lead to an explanation of the observed maximum speeds of perfectly smooth crack propagation, could be misleading if the slightest step formation occurred at high strains since the consequent energy dissipation could be very much greater than for glass.In this respect a better analogy is with anelastic materials such as polycrystalline metals. Gilman 16 has calculated.tli~ energy dissipated in plastic deformation at a,:>tep and obtains values of the order of 10 6 ergs/sq cm ·~f fracture surface for a typical step height of 1000 A. The work required to produce a unit area of fractured surface thus greatly exceeds the surface energy. This is also the case for rubber4 where the hysteretic loss in the highly sheared material around the step apparently takes the place of the energy dissipated by plastic shearing.The general pattern of fracture propagation in both normal and highly elastic solids would appear to be as follows. First, at low speeds, a mode of quasi-static 18 J. J, Gilman. J, App!. Phys, 27, 1262Phys, 27, (1956 propagation, generally with smooth surfaces, obtained by carefully controlling the boundary conditions to maintain the stability of the stress distribution around the leading edge of the fracture and hence the steadiness of the propagation. Secondly, there is the region of more or less unsteady propagation in which rough surfaces are produced and an average rate of propagation is obtained as a compromise between the tendency to accelerate toan upper limit (as in the third region) and the tendency to instability, i.e., for the fracture to develop on two or more planes, and to use the available energy in shearing between these fracture planes. Thirdly, there is a region where the speed of propagation is a maximum (excluding shock wave phenomena), being limited by the speed of elastic waves in the material as in Mott's theory. ACKNOWLEDGMENTSThe author expresses his gratitude to Mr. J. E.The ion-bombardment cleaning method has been successfully applied to the (100) faces of germanium, silicon, and nickel, and to the (0001) face of titanium. Conditions and precautions necessary for the production of clean surfaces are described. Tests have been made for contamination from the ambient during the cleaning procedure for germanium. It has been shown that contamination approximating one-half monolayer does not occur under the conditions which were obtained, and that the method is capable of producing surfaces which are atomically clean.Results for clean (100), (111), and (110) germanium faces and the (100) silicon face indicate that the atomic positions in the surface planes are not the same as the corresponding positions in the bulk structure. For (100) nickel and (0001) titaniuIil, the positions of the atoms in the surface planes are in agreement with x-ray data. In the case of titanium, an unidentified surf...

Role of oligomer structures in the surface chemistry of amidinate metal complexes used for atomic layer deposition of thin films

“…A Ni(110) single crystal was used as the substrate, cleaned in situ before each experiment by a combination of chemical (O 2 and H 2 treatments) and physical (sputtering-annealing cycles) procedures until the surface was deemed cleaned by CO or H 2 TPD. Sputtering was followed by annealing at high temperatures (;1100 K) to regain the smooth nature of the single-crystal flat (110) surface, as established by others in the past [36,37]. The UHV chamber used in these experiments is also equipped with an hemispherical electron energy analyzer and an aluminum-anode (hm 5 1486.6 eV) X-ray source, used to acquire XPS to further check on the cleanliness of the sample.…”

Surface conductivity of semiconductors and its variation by adsorption, transverse electric fields and irradiation

“…43 To remove this layer and other contaminations a cleaning procedure has been developed using a bombardment with argon ions and subsequent annealing in an ultra-high vacuum. 18 It has been shown by measurements of field effect and surface conductivity that this cleaning method produces extremely p-type surfaces (G = 2 x 10-4 ohm-1) even on n-type crystals (inversion layer, fig. l(c) and fig.…”

Departures from the ideal chemical and physical structure of a semiconductor considered in relation to chemical reactivity

“…(i) Slow-electron diffraction 17 determines the surface spacing and changes of the surface structure upon exposure to ambients. (ii) The investigation of the ejection patterns of atoms sputtered from crystal surfaces under ion bombardment.…”