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Investigation of composition of surface oxides of molybdenum by the method of secondary ion-ion emission.
Classified Classified
abstracts
abstracts 682-689
682-782
on this page
Editor’s note The label immediately following the title of each item denotes country or origin end of each abstract indicates country of origin of work (where known).
I.
General
16. GASES
vacuum
science
and engineering
AND SOLIDS
16 682. Temperature and height of the maximum desorption rate as a function of the surface coverage of the linde molecular sieve 13X. (Germany) From molecular sieves, each test gas is desorbed in a definite temperature interval, and the previously reported dependence of the characteristic temperature of the interval on the surface coverage is investigated in more detail. The curves obtained show the strong dependence of the maximum desorption rate on the pressure during absorption. On double logarithimic paper, straight lines were obtained with slopes m-O.63 for CO2 and m-0.80 for CO. Finally the utility of the method of slow desorption spectrometry in gas analysis is demonstrated using three gas mixtures of known composition. M Durm and K Starke, VrrX~rl,,,l-Trrh,rik, 21 (I), Feb 1972, 1 I-15 (i/q German). 16 683. Sorption capacities in desorption spectrometry with the Linde molecular sieve 13X. (Germany) As a basis for desorption studies on the Linde 13X molecular sieve, the sorption capacity of the device was determined and the results compared with theoretical predictions. Experimental results obtained with several binary gas mixtures showed very close agreement with the theoretical. However, it was observed that, with increasing surface coverage, the maxima Iof the desorption rate curves were shifted to lower temperatures. This cannot be explained by the present calculations which are based on a first order reaction. M Durm and K Starke, Ynkuun~-fechnik, 20 (S), Dee 1971, 239-244 (in Geuman). 16 684. Influence of electron bombardment on sorption properties of carbon dioxide condensed at 20’ K. (USSR) Influence of electron bombardment on the sorption characteristics of layers of condensed gases was examined. The system hydrogencarbon dioxide at 20 ‘K: was chosen for the experiments. An experimental arrangement consisting of two vacuum chambers with ultimate pressures of I k 10mx torr is described. Sorption ability was determined by measurement of isotherms in the pressure range 10e3 to IO-’ torr. An electron gun with tungsten cathode and current of 5 mA was used to provide an electron beam with a circular cross section of 50 cm’ on the collector. Layers of solid carbon dioxide IO-” cm thick were investigated. The possibility of self-protection in the layers against electrons with small energies up to 100 eV is demonstrated. Prolonged bombardment by electrons with higher energies results in structural changes in the layers and aggravation of their sorption characteristics. The cause of a decrease in the pumping speed of the layer bombarded with electrons is assumed to be a decrease in the hydrogen diffilsion flow inside the layer, which can be attributed to a reduction in the total surface of inter-grain boundaries during the process of crystallite growth. V B Yuferovand L G Sorokovoy,Zh Tekh Fiz, 41 (IO), Ort 1971,21912195 (in Russian). I6 685. Dependence of evaporation characteristics of barium oxide film from molybdenum substrate on temperature and degree of coverage. (USSR) The evaporation characteristics of the system BaO-Mo(llz) prepared by evaporation of BaO on heated filaments are investigated. The experiments were performed in a device with two filaments functioning as 3 sample and receiver at residual gas pressure of 2 ;+ IO-” torr.
of publication,
and that at the
It is shown that the evaporation rate from the lilament heated during deposition is higher than the evaporation rate from the filamtnt which was not heated during EaO deposition. Activity of the EaO films is preserved in a broad interval of temperatures. At all ten-peratures, only a part of the tilm is evaporated and this part increases with temperature rise. At temperature of 1400-K the film with the coverage below unity is evaporated fully, while the EaO film with coverage higher than unity is not fully evaporated and, probably, a part of BaO dissociates and it is not recorded by the receiver filament. The thermal dependence of the heat of evaporation of the film was determined. A R Shulman and T S Kirsanova, Izv VUZ Fiz, No IO, 197 I, 99- IO3 (if/ Russian). I6 686. Scattering of slow caesium ions on a tungsten surface at low temperatures. (USSR) The scattering of slow caesium ions, with energies of 20 to 250 eV, is investigated in the bombardment of polycrystalline tungsten at low temperatures. Experimental results are discussed. V I Veksler and R N Evtukhov, fzla VUZ Fiz, No 6, 1971, 125 (in Russiail). 16 687. Investigation of composition of surface oxides of molybdenum by the method of secondary ion-ion emission. (IJSSR) The secondary ion-ion emission method is used to investigate the composition of oxides on the molybdenum surface. The expcrilrents were performed in a vacuum chamber with variable partial pressureof oxygen in the range 5 i; IO-* to I x lo-” torr. A primauy beam of argon ions, with energy of 4 keV and current density of 5 J IO-’ A/cm2, was incident to the molybdenum filament and the emitted secondary ions were analyzed by a magnetic mass spectron-eter. It is found that oxides Mo,O,, MOO,, MOO,, Mo,O,, and Mo?O exist on the surface of molybdenum. The relative coverage of the molybdenum surface by these oxides depends on the temperature and partial prcssure of oxygen. The results are compared with those obtained by the flash filament method with use of a mass spectrometer. V Ya Kolot et al, Izv AN SSSR Ser Fiz, 35 (2), 1971, 255-260 (i/l Russian). I6 688. Fine structure of the electron characteristic energy loss spectrum in GaAs. (USSR) The fine structure of the electron characteristic energy loss spectrum of electrons with energies below 400 eV reflected from the GaAs (1 IO) surface is observed and analyzed by the technique of electronic differentiation with respect to energy of the inelastic scattered electron current. The experiments were performed in an all-metal appnratus for low energy electron diffraction. An atomically clean GaAs surface was obtained by cleaving the crystal in vacuum at 5 x 10-l” torr. The degree of cleanliness of the surface was checked by LEED. The position of the characteristic energy loss peaks of the (1 IO) GaAs surface cleaved in 5x lO-‘O torr and the same surface after 8 hour storage in vacuum at I x 10m5 torr is investigated. The data obtained and those obtained by optical measurement are correlated. The feasability of employing characteristic energy loss spectra of low energy electrons for studying the purity and chemical composition of the surface of solids is demonstrated experimentally. A Yu Mityagin et al, Zh Eksper Twu Fiz, 61 (5). Nov 1971, 1957- 1961 (if? Russian). 16 689. Investigation of kinetics of oxygen interaction with tantalum using the flash-filament method. (USSR) Using the flash-filament method in connection with a timeof-ilight 239
abstracts
abstracts 682-689
682-782
on this page
Editor’s note The label immediately following the title of each item denotes country or origin end of each abstract indicates country of origin of work (where known).
I.
General
16. GASES
vacuum
science
and engineering
AND SOLIDS
16 682. Temperature and height of the maximum desorption rate as a function of the surface coverage of the linde molecular sieve 13X. (Germany) From molecular sieves, each test gas is desorbed in a definite temperature interval, and the previously reported dependence of the characteristic temperature of the interval on the surface coverage is investigated in more detail. The curves obtained show the strong dependence of the maximum desorption rate on the pressure during absorption. On double logarithimic paper, straight lines were obtained with slopes m-O.63 for CO2 and m-0.80 for CO. Finally the utility of the method of slow desorption spectrometry in gas analysis is demonstrated using three gas mixtures of known composition. M Durm and K Starke, VrrX~rl,,,l-Trrh,rik, 21 (I), Feb 1972, 1 I-15 (i/q German). 16 683. Sorption capacities in desorption spectrometry with the Linde molecular sieve 13X. (Germany) As a basis for desorption studies on the Linde 13X molecular sieve, the sorption capacity of the device was determined and the results compared with theoretical predictions. Experimental results obtained with several binary gas mixtures showed very close agreement with the theoretical. However, it was observed that, with increasing surface coverage, the maxima Iof the desorption rate curves were shifted to lower temperatures. This cannot be explained by the present calculations which are based on a first order reaction. M Durm and K Starke, Ynkuun~-fechnik, 20 (S), Dee 1971, 239-244 (in Geuman). 16 684. Influence of electron bombardment on sorption properties of carbon dioxide condensed at 20’ K. (USSR) Influence of electron bombardment on the sorption characteristics of layers of condensed gases was examined. The system hydrogencarbon dioxide at 20 ‘K: was chosen for the experiments. An experimental arrangement consisting of two vacuum chambers with ultimate pressures of I k 10mx torr is described. Sorption ability was determined by measurement of isotherms in the pressure range 10e3 to IO-’ torr. An electron gun with tungsten cathode and current of 5 mA was used to provide an electron beam with a circular cross section of 50 cm’ on the collector. Layers of solid carbon dioxide IO-” cm thick were investigated. The possibility of self-protection in the layers against electrons with small energies up to 100 eV is demonstrated. Prolonged bombardment by electrons with higher energies results in structural changes in the layers and aggravation of their sorption characteristics. The cause of a decrease in the pumping speed of the layer bombarded with electrons is assumed to be a decrease in the hydrogen diffilsion flow inside the layer, which can be attributed to a reduction in the total surface of inter-grain boundaries during the process of crystallite growth. V B Yuferovand L G Sorokovoy,Zh Tekh Fiz, 41 (IO), Ort 1971,21912195 (in Russian). I6 685. Dependence of evaporation characteristics of barium oxide film from molybdenum substrate on temperature and degree of coverage. (USSR) The evaporation characteristics of the system BaO-Mo(llz) prepared by evaporation of BaO on heated filaments are investigated. The experiments were performed in a device with two filaments functioning as 3 sample and receiver at residual gas pressure of 2 ;+ IO-” torr.
of publication,
and that at the
It is shown that the evaporation rate from the lilament heated during deposition is higher than the evaporation rate from the filamtnt which was not heated during EaO deposition. Activity of the EaO films is preserved in a broad interval of temperatures. At all ten-peratures, only a part of the tilm is evaporated and this part increases with temperature rise. At temperature of 1400-K the film with the coverage below unity is evaporated fully, while the EaO film with coverage higher than unity is not fully evaporated and, probably, a part of BaO dissociates and it is not recorded by the receiver filament. The thermal dependence of the heat of evaporation of the film was determined. A R Shulman and T S Kirsanova, Izv VUZ Fiz, No IO, 197 I, 99- IO3 (if/ Russian). I6 686. Scattering of slow caesium ions on a tungsten surface at low temperatures. (USSR) The scattering of slow caesium ions, with energies of 20 to 250 eV, is investigated in the bombardment of polycrystalline tungsten at low temperatures. Experimental results are discussed. V I Veksler and R N Evtukhov, fzla VUZ Fiz, No 6, 1971, 125 (in Russiail). 16 687. Investigation of composition of surface oxides of molybdenum by the method of secondary ion-ion emission. (IJSSR) The secondary ion-ion emission method is used to investigate the composition of oxides on the molybdenum surface. The expcrilrents were performed in a vacuum chamber with variable partial pressureof oxygen in the range 5 i; IO-* to I x lo-” torr. A primauy beam of argon ions, with energy of 4 keV and current density of 5 J IO-’ A/cm2, was incident to the molybdenum filament and the emitted secondary ions were analyzed by a magnetic mass spectron-eter. It is found that oxides Mo,O,, MOO,, MOO,, Mo,O,, and Mo?O exist on the surface of molybdenum. The relative coverage of the molybdenum surface by these oxides depends on the temperature and partial prcssure of oxygen. The results are compared with those obtained by the flash filament method with use of a mass spectrometer. V Ya Kolot et al, Izv AN SSSR Ser Fiz, 35 (2), 1971, 255-260 (i/l Russian). I6 688. Fine structure of the electron characteristic energy loss spectrum in GaAs. (USSR) The fine structure of the electron characteristic energy loss spectrum of electrons with energies below 400 eV reflected from the GaAs (1 IO) surface is observed and analyzed by the technique of electronic differentiation with respect to energy of the inelastic scattered electron current. The experiments were performed in an all-metal appnratus for low energy electron diffraction. An atomically clean GaAs surface was obtained by cleaving the crystal in vacuum at 5 x 10-l” torr. The degree of cleanliness of the surface was checked by LEED. The position of the characteristic energy loss peaks of the (1 IO) GaAs surface cleaved in 5x lO-‘O torr and the same surface after 8 hour storage in vacuum at I x 10m5 torr is investigated. The data obtained and those obtained by optical measurement are correlated. The feasability of employing characteristic energy loss spectra of low energy electrons for studying the purity and chemical composition of the surface of solids is demonstrated experimentally. A Yu Mityagin et al, Zh Eksper Twu Fiz, 61 (5). Nov 1971, 1957- 1961 (if? Russian). 16 689. Investigation of kinetics of oxygen interaction with tantalum using the flash-filament method. (USSR) Using the flash-filament method in connection with a timeof-ilight 239