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Surface self diffusion at cryogenic temperatures: Rh on Rh
Classified abstracts
561-574
16 561. The use of ion beams in surface physics studies. (GB) This paper reviews recent progess on the applications of the reflection of ions, the emission of rays by ion bombardment, and the generation of secondary ion species at solid surfaces, for composition and structure analysis. The resolution and sensitivity of the techniques are discussed and the problems of rendering the processes quantitative examined. G Carter (Proc 19th Nat Symp Am Vat Sot), J Vat Sci Technol, 10 (l), Jan/Fe6 1973, 95-99. 16 562. Sticking coetBcient of COz on solid Hz0 films. (USA) A molecular beam method has been used to measure the sticking coefficient y of COZ molecules on thin films of solid HzO. Impingement rates were below 10“’ molecules cm-= s-r, and the CO2 gas temperature was 184 K. The substrate temperature 7” was varied from 65.5-76.4 K. At Ts = 76.4 K, y was initially near umty, but decreased with increasing CO2 coverage until y N 0 at approximately monolayer coverage. When Ts was below 76.4 K, the initial y was also close to unity. As the CO* coverage increased, y decreased to a minimum value at about one monolayer coverage. However, y again increased with time as COZ continued to be deposited. These results are discussed in terms of a simple nucleation theory. V Caxcarra et al, (Proc 19th Nat Symp Am Vat Sot), J Vat Sci Technol, 10 (l), Jan/Fe6 1973, 148-152. 16 563. Oxidation of (011) iron at room temperature: mainly LEED aspects. (USA) The interaction of oxygen with (011) Fe at room temperature has been investigated using simultaneous combinations of LEED, ellipsometry, and surface potential measurements. This paper is concerned mainly with the LEED aspects. The sequence of LEED patterns found was either similar to that previously found or slightly different, depending on experimental conditions. In most experiments a new LEED pattern, ~(2 x l), was observed instead of the c(3 x 1) pattern previously reported. Direct keying of the LEED patterns to the ellipsometry-derived growth kinetics leads to further understanding of the oxidation mechanism. The occurrence of heterogeneous oxide nucleation is supported, and it is shown that an oxide consistent with the expected diffraction properties of Fe0 grows to a ‘limiting’ thickness of about 25-30 A in oxygen. The terminal oxide in the air is concluded to have about the same thickness but a significantly different structure. A J MeImed and J J Carroll, (Proc 19th Nat Symp Am Vat Symp) J Vat Sci Technol, 10 (l), Jan/Fe6 1973, 164-169. 16 564, Photoemission spectra from adsorbed 0 on W(110) and CO on W(100). (USA) Photoemission energy distribution curves are presented for adsorbed layers of 0 on W(110) and CO on W(100) surfaces. The electronic energy levels of adsorbed oxygen initially form a 2.0 eV-wide peak at - 6.4 eV below the Fermi level which shifts to - 6.0 eV and broadens to 2.8 eV with increasing coverage. Provision for simultaneous LEED, Auger spectroscopy, and flash desorption enable the structure and coverage of the adsorbed layers to be determined. /3 phase CO adsorbed in either the (1 x 1) or C(2 x 2) structures on W(100) produces a photoemission peak at -6.0 eV with a weaker peak at -3.5 eV. Adsorption of CO in the a phase gives rise to a 2.2 eV-wide peak at -8.9 eV which is identified as originating from levels essentially the same as those of molecular CO. J M Baker and D E Eastman, (Proc 19th Nat Symp Am Vat Sot) J Vat Sci Technol, 10 (l), Jan/Fe6 1973, 223-226. 16 565. Scattering of metastable molecules from a gas-covered (100) surface of germanimn (USA). Studies have been made of the scattering and deexcitation of thermal energy beams of metastable Ar, He, Ne, and NZ from an oxygencovered germanium surface. It has been found that the survival of incident metastable species after a surface collision is strongly dependent on the degree of surface gas coverage. Using the metastable time-of-flight technique, both angular scattering and time-of-flight distributions were measured for the scattered metastable species. Changes in the TOF distribution of the scattered molecules relative to the incident distribution have been observed. In addition, changes in 336
angular distribution as well as total me&table survival have been observed as a function of incident angle. Differences in survival for the various species studied have been measured and are discussed in terms of the excitation energy of the excited electron in the metastable atom relative to untilled energy states at the germanium surface. J H Craig Jr and J T Dickinson, J Vat Sci Technol, 10 (l), Jan/Fe6 1973, 319-324. 16 566. FEM studies of oxygen on silver. (Germany) WA Schmidt et ai, Abstract. (Proc 19th Nat Symp Am Vat Sot) J Vat Sci Technol, 10 (l), Jan/Fe6 1973, 295. 16 567. Adsorption and solution of Ha and Nz by Ta and Nb. (USA) S M Ko and L D Schmidt, Abstract. (Proc 19th Nat Symp Am Vat Sot) J Vat Sci Technol, 10 (l), Jan/Fe6 1973,294. 16 56% Reaction kinetics of gas-solid reactions at elevated temperatures. (USA) R J Madix, Abstract. (Proc 19th Nat Symp Am Vat Sot) J Vat Sci Technol, 10 (l), Jan/Fe6 1973, 283. 16 569. Scattering of diatomic and poiyatomic molecules from the (100) crystal face of platinum. (USA) L A West and G A Somorjai, Abstract. (Proc 19th Nat Symp Am Vat Sot) J Vat Sci Technol, 10 (l), Jan/Fe6 1973,273. 16 570. Interaction of carbon monoxide with (110) nickel. (Germany) H H Madden et al, Abstract. (Proc 19th Nat Symp Am Vat Sot) J Vat Sci Technol, 10 (l), Jan/Fe6 1973, 266. 16 571. Lateral interactions in adsorption and desorption kinetics. (GB) D A King, Abstract. (Proc. 19th Nat Symp Am Vat Sot) J Vat Sci Technol, 10 (l), Jan/Fe6 1973, 272.
17. THERMODYNAMICS 17 572. Spatial distribution of CO, and H,O molecules on reflection and sublimation from a cold surface. (USA) An effusive molecular beam, a copper target, and several quartz crystal microbalances were used to measure the spatial distributions of reflected and sublimated COZ and Ha0 molecules. These spatial distributions were found to be identical for surface temperatures ranging from 55 to 210 K for COZ and from 55 to 160 K for H20, and for gas temperatures below 300 K. Experimental results agreed with the diffuse cosine law spatial distribution within the accuracy of the measurement. C E Bryson III et ai, J Vat Sci Technol, 10 (l), Jan/Fe6 1973,310-312. 17 573. Surface self diffusion at cryogenic temperatures: Rh on Rh. (USA) G Ayrault and G Ehrlich, Abstract. (Proc 19th Nat Symp Am Vat Sot) J Vat Sci Technol, 10 (l), Jan/Fe6 1973, 266.
18. GASEOUS ELECTRONICS 18 574. Impedance probe and dc probe studies on tire plasma of a glow discharge. (India) A plane probe acting simultaneously as an rf impedance probe and a dc probe has been used for studying the collision-dominated plasma of a glow discharge. The conventional probe methods are suitably modified so as to take into account the effect of the presheath lying between the probe sheath and the undisturbed plasma. Measurements of the electron temperature and electron density have been carried out under different discharge conditions. It is found that the electron temperatures, as given by the rf and dc methods, are in excellent agreement, while the corresponding electron densities differ by a factor of 2-3. The thickness of the positive-ion sheath formed in front of the probe has been determined by the impedance method; the variation of the thickness with sheath voltage, discharge current or operating pressure is as expected. C Sen and J Basu, JPhys D: Appl Phys, 6 (2) 19 Jan 1973, 172-183.
561-574
16 561. The use of ion beams in surface physics studies. (GB) This paper reviews recent progess on the applications of the reflection of ions, the emission of rays by ion bombardment, and the generation of secondary ion species at solid surfaces, for composition and structure analysis. The resolution and sensitivity of the techniques are discussed and the problems of rendering the processes quantitative examined. G Carter (Proc 19th Nat Symp Am Vat Sot), J Vat Sci Technol, 10 (l), Jan/Fe6 1973, 95-99. 16 562. Sticking coetBcient of COz on solid Hz0 films. (USA) A molecular beam method has been used to measure the sticking coefficient y of COZ molecules on thin films of solid HzO. Impingement rates were below 10“’ molecules cm-= s-r, and the CO2 gas temperature was 184 K. The substrate temperature 7” was varied from 65.5-76.4 K. At Ts = 76.4 K, y was initially near umty, but decreased with increasing CO2 coverage until y N 0 at approximately monolayer coverage. When Ts was below 76.4 K, the initial y was also close to unity. As the CO* coverage increased, y decreased to a minimum value at about one monolayer coverage. However, y again increased with time as COZ continued to be deposited. These results are discussed in terms of a simple nucleation theory. V Caxcarra et al, (Proc 19th Nat Symp Am Vat Sot), J Vat Sci Technol, 10 (l), Jan/Fe6 1973, 148-152. 16 563. Oxidation of (011) iron at room temperature: mainly LEED aspects. (USA) The interaction of oxygen with (011) Fe at room temperature has been investigated using simultaneous combinations of LEED, ellipsometry, and surface potential measurements. This paper is concerned mainly with the LEED aspects. The sequence of LEED patterns found was either similar to that previously found or slightly different, depending on experimental conditions. In most experiments a new LEED pattern, ~(2 x l), was observed instead of the c(3 x 1) pattern previously reported. Direct keying of the LEED patterns to the ellipsometry-derived growth kinetics leads to further understanding of the oxidation mechanism. The occurrence of heterogeneous oxide nucleation is supported, and it is shown that an oxide consistent with the expected diffraction properties of Fe0 grows to a ‘limiting’ thickness of about 25-30 A in oxygen. The terminal oxide in the air is concluded to have about the same thickness but a significantly different structure. A J MeImed and J J Carroll, (Proc 19th Nat Symp Am Vat Symp) J Vat Sci Technol, 10 (l), Jan/Fe6 1973, 164-169. 16 564, Photoemission spectra from adsorbed 0 on W(110) and CO on W(100). (USA) Photoemission energy distribution curves are presented for adsorbed layers of 0 on W(110) and CO on W(100) surfaces. The electronic energy levels of adsorbed oxygen initially form a 2.0 eV-wide peak at - 6.4 eV below the Fermi level which shifts to - 6.0 eV and broadens to 2.8 eV with increasing coverage. Provision for simultaneous LEED, Auger spectroscopy, and flash desorption enable the structure and coverage of the adsorbed layers to be determined. /3 phase CO adsorbed in either the (1 x 1) or C(2 x 2) structures on W(100) produces a photoemission peak at -6.0 eV with a weaker peak at -3.5 eV. Adsorption of CO in the a phase gives rise to a 2.2 eV-wide peak at -8.9 eV which is identified as originating from levels essentially the same as those of molecular CO. J M Baker and D E Eastman, (Proc 19th Nat Symp Am Vat Sot) J Vat Sci Technol, 10 (l), Jan/Fe6 1973, 223-226. 16 565. Scattering of metastable molecules from a gas-covered (100) surface of germanimn (USA). Studies have been made of the scattering and deexcitation of thermal energy beams of metastable Ar, He, Ne, and NZ from an oxygencovered germanium surface. It has been found that the survival of incident metastable species after a surface collision is strongly dependent on the degree of surface gas coverage. Using the metastable time-of-flight technique, both angular scattering and time-of-flight distributions were measured for the scattered metastable species. Changes in the TOF distribution of the scattered molecules relative to the incident distribution have been observed. In addition, changes in 336
angular distribution as well as total me&table survival have been observed as a function of incident angle. Differences in survival for the various species studied have been measured and are discussed in terms of the excitation energy of the excited electron in the metastable atom relative to untilled energy states at the germanium surface. J H Craig Jr and J T Dickinson, J Vat Sci Technol, 10 (l), Jan/Fe6 1973, 319-324. 16 566. FEM studies of oxygen on silver. (Germany) WA Schmidt et ai, Abstract. (Proc 19th Nat Symp Am Vat Sot) J Vat Sci Technol, 10 (l), Jan/Fe6 1973, 295. 16 567. Adsorption and solution of Ha and Nz by Ta and Nb. (USA) S M Ko and L D Schmidt, Abstract. (Proc 19th Nat Symp Am Vat Sot) J Vat Sci Technol, 10 (l), Jan/Fe6 1973,294. 16 56% Reaction kinetics of gas-solid reactions at elevated temperatures. (USA) R J Madix, Abstract. (Proc 19th Nat Symp Am Vat Sot) J Vat Sci Technol, 10 (l), Jan/Fe6 1973, 283. 16 569. Scattering of diatomic and poiyatomic molecules from the (100) crystal face of platinum. (USA) L A West and G A Somorjai, Abstract. (Proc 19th Nat Symp Am Vat Sot) J Vat Sci Technol, 10 (l), Jan/Fe6 1973,273. 16 570. Interaction of carbon monoxide with (110) nickel. (Germany) H H Madden et al, Abstract. (Proc 19th Nat Symp Am Vat Sot) J Vat Sci Technol, 10 (l), Jan/Fe6 1973, 266. 16 571. Lateral interactions in adsorption and desorption kinetics. (GB) D A King, Abstract. (Proc. 19th Nat Symp Am Vat Sot) J Vat Sci Technol, 10 (l), Jan/Fe6 1973, 272.
17. THERMODYNAMICS 17 572. Spatial distribution of CO, and H,O molecules on reflection and sublimation from a cold surface. (USA) An effusive molecular beam, a copper target, and several quartz crystal microbalances were used to measure the spatial distributions of reflected and sublimated COZ and Ha0 molecules. These spatial distributions were found to be identical for surface temperatures ranging from 55 to 210 K for COZ and from 55 to 160 K for H20, and for gas temperatures below 300 K. Experimental results agreed with the diffuse cosine law spatial distribution within the accuracy of the measurement. C E Bryson III et ai, J Vat Sci Technol, 10 (l), Jan/Fe6 1973,310-312. 17 573. Surface self diffusion at cryogenic temperatures: Rh on Rh. (USA) G Ayrault and G Ehrlich, Abstract. (Proc 19th Nat Symp Am Vat Sot) J Vat Sci Technol, 10 (l), Jan/Fe6 1973, 266.
18. GASEOUS ELECTRONICS 18 574. Impedance probe and dc probe studies on tire plasma of a glow discharge. (India) A plane probe acting simultaneously as an rf impedance probe and a dc probe has been used for studying the collision-dominated plasma of a glow discharge. The conventional probe methods are suitably modified so as to take into account the effect of the presheath lying between the probe sheath and the undisturbed plasma. Measurements of the electron temperature and electron density have been carried out under different discharge conditions. It is found that the electron temperatures, as given by the rf and dc methods, are in excellent agreement, while the corresponding electron densities differ by a factor of 2-3. The thickness of the positive-ion sheath formed in front of the probe has been determined by the impedance method; the variation of the thickness with sheath voltage, discharge current or operating pressure is as expected. C Sen and J Basu, JPhys D: Appl Phys, 6 (2) 19 Jan 1973, 172-183.