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Diffusion of oxygen on the Mo(110) plane
A527 Surface Science 290 (1993) 1-14 North-Holland
Diffusion of oxygen on the Mo(ll0) plane Y. Song and R. Gomer Department of Chemtstry and The James Franck Institute, Unwerstty of Chtcago, 5640 Elhs Avenue, Chtcago, IL 60637, USA Recewed 16 November 1992, accepted for pubhcatlon 2 February 1993 T h e diffusion and m e a n square fluctuations ( ( ~ N ) 2 ) / ( N ) of O on M o ( l l 0 ) have been investigated as functions of coverage and temperature over the range 0 05 < 0 < 0 9 The diffusion coefficient D, multlphed by ( ( g N ) 2 ) / ( N ) yields the j u m p diffusion coefficient Dj, which is stmilar to the single parhcle or tracer coefficient T h e forms D = D o e x p ( - ~ E ) and Dj = Dj0 eXl~-13Ej) with {J = 1/knT are used to analyze the results Except at 0 = 0 9 ( ( ~ N ) 2 ) / ( N ) 1s temperature independent, so that E = E k E increases from 17 kcal at 0 = 0 07 to 26 kcal at 0 = 0 5, then drops to 18 kcal at 0 = 0 7 and finally rises to ~ 20 keai at 0 = 0 9 At this coverage Ej --- 28 kcal D o v a n e s from 1 em 2 s - I at low coverage to 1 0 - 2 - 1 0 -1 cm 2 s -1 at 0 = 0 5, then drops to 10 -5 cm 2 s - I at 0 = 0 9 Dj0 values range from 10 - 2 cm 2 s -1 at 0 = 0 05, drop to 2 × 10 - 4 cm 2 s -1 at 0 = 0 15, then rtse to 10 - 2 em 2 s -1 at 0 = 0 5 and finally decrease to 10 -5 cm 2 s -1 at higher coverages There are strong compensation effects between E and Dj0 T h e variation in E with coverage can be explained in terms of repulswe nearest and attractive farther-than-nearest-neighbor O - O lnteraetaons, which are suggested by the low 0 phase diagram The coverage dependence of ( ( g N ) 2 / ( N ) lS comphcated, with a m i n i m u m at 0 - 0 25 and a broad m a r a m u m near 0 = 0 5
Surface Science 290 (1993) 15-25 North-Holland
STM study of the structure and phases of Pb on Ge(111) L. Seehofer, G. Falkenberg and R.L. Johnson II Instltut fur Expenmentalphysd~, Unwersltat Hamburg, Luruper Chaussee 149, D-2000 Hamburg 50, Germany Received 25 November 1992, accepted for pubhcatlon 10 February 1993
T h e dtfferent structures of Pb on G e ( l l l ) have been studied as a function of Pb-coverage up to two monolayers wtth scanning t u n n e h n g microscopy At low coverages a c(2 × 8) and a (v/3 × v~)R30* reconstruction with a mtxture of Pb and Ge adatoms both occupying T4-sltes was observed T h e bias voltage dependence of topographic images of these structures xs interpreted m terms of a charge transfer between the different adatom danghng-bond orbltals O n the basis of the STM images new structural models for the metastable (4 × 4) reconstruction and the higher density (¢'3- × vr3)R30 * reconstruction are proposed In a d d m o n a previously unobserved striped i n c o m m e n s u r a t e phase was found for coverages greater than 4 / 3 monolayers T h e data from th~s striped phase are compared with the predictions of domain-wall theory for c o m m e n s u r a t e - i n c o m m e n s u r a t e phase t r a n s m o n s
Surface Science 290 (1993) 26-34 North-Holland
Low energy Auger electron spectroscopy of iron oxide: oxidation of one monolayer of iron on Cu(100) H. den Daas, O.L.J. Gllzeman and J.W. Geus Debye Instttute, Surface Sctence Dw~swn, Utrecht Umverstty, Padualaan 8, 3584 CH Utrecht, Netherlands Received 20 November 1992, accepted for pubhcation 27 January 1993 T h e peak shape of the iron M2,3W A u g e r peak d u n n g the oyadaUon of one monolayer of iron on Cu(100) was studied Peak shape analysts indicated that all iron is o~adlsed to T-Fe203 before oxygen adsorbs on the Cu(100) surface T h e oJodatlon of iron probably proceeds at once from Fe ° to Fe 3+ though Initially adsorbing oxygen causes a different ratio between the cross transition and the auto-lonlsatlon peak than later adsorbing oxygen
Diffusion of oxygen on the Mo(ll0) plane Y. Song and R. Gomer Department of Chemtstry and The James Franck Institute, Unwerstty of Chtcago, 5640 Elhs Avenue, Chtcago, IL 60637, USA Recewed 16 November 1992, accepted for pubhcatlon 2 February 1993 T h e diffusion and m e a n square fluctuations ( ( ~ N ) 2 ) / ( N ) of O on M o ( l l 0 ) have been investigated as functions of coverage and temperature over the range 0 05 < 0 < 0 9 The diffusion coefficient D, multlphed by ( ( g N ) 2 ) / ( N ) yields the j u m p diffusion coefficient Dj, which is stmilar to the single parhcle or tracer coefficient T h e forms D = D o e x p ( - ~ E ) and Dj = Dj0 eXl~-13Ej) with {J = 1/knT are used to analyze the results Except at 0 = 0 9 ( ( ~ N ) 2 ) / ( N ) 1s temperature independent, so that E = E k E increases from 17 kcal at 0 = 0 07 to 26 kcal at 0 = 0 5, then drops to 18 kcal at 0 = 0 7 and finally rises to ~ 20 keai at 0 = 0 9 At this coverage Ej --- 28 kcal D o v a n e s from 1 em 2 s - I at low coverage to 1 0 - 2 - 1 0 -1 cm 2 s -1 at 0 = 0 5, then drops to 10 -5 cm 2 s - I at 0 = 0 9 Dj0 values range from 10 - 2 cm 2 s -1 at 0 = 0 05, drop to 2 × 10 - 4 cm 2 s -1 at 0 = 0 15, then rtse to 10 - 2 em 2 s -1 at 0 = 0 5 and finally decrease to 10 -5 cm 2 s -1 at higher coverages There are strong compensation effects between E and Dj0 T h e variation in E with coverage can be explained in terms of repulswe nearest and attractive farther-than-nearest-neighbor O - O lnteraetaons, which are suggested by the low 0 phase diagram The coverage dependence of ( ( g N ) 2 / ( N ) lS comphcated, with a m i n i m u m at 0 - 0 25 and a broad m a r a m u m near 0 = 0 5
Surface Science 290 (1993) 15-25 North-Holland
STM study of the structure and phases of Pb on Ge(111) L. Seehofer, G. Falkenberg and R.L. Johnson II Instltut fur Expenmentalphysd~, Unwersltat Hamburg, Luruper Chaussee 149, D-2000 Hamburg 50, Germany Received 25 November 1992, accepted for pubhcatlon 10 February 1993
T h e dtfferent structures of Pb on G e ( l l l ) have been studied as a function of Pb-coverage up to two monolayers wtth scanning t u n n e h n g microscopy At low coverages a c(2 × 8) and a (v/3 × v~)R30* reconstruction with a mtxture of Pb and Ge adatoms both occupying T4-sltes was observed T h e bias voltage dependence of topographic images of these structures xs interpreted m terms of a charge transfer between the different adatom danghng-bond orbltals O n the basis of the STM images new structural models for the metastable (4 × 4) reconstruction and the higher density (¢'3- × vr3)R30 * reconstruction are proposed In a d d m o n a previously unobserved striped i n c o m m e n s u r a t e phase was found for coverages greater than 4 / 3 monolayers T h e data from th~s striped phase are compared with the predictions of domain-wall theory for c o m m e n s u r a t e - i n c o m m e n s u r a t e phase t r a n s m o n s
Surface Science 290 (1993) 26-34 North-Holland
Low energy Auger electron spectroscopy of iron oxide: oxidation of one monolayer of iron on Cu(100) H. den Daas, O.L.J. Gllzeman and J.W. Geus Debye Instttute, Surface Sctence Dw~swn, Utrecht Umverstty, Padualaan 8, 3584 CH Utrecht, Netherlands Received 20 November 1992, accepted for pubhcation 27 January 1993 T h e peak shape of the iron M2,3W A u g e r peak d u n n g the oyadaUon of one monolayer of iron on Cu(100) was studied Peak shape analysts indicated that all iron is o~adlsed to T-Fe203 before oxygen adsorbs on the Cu(100) surface T h e oJodatlon of iron probably proceeds at once from Fe ° to Fe 3+ though Initially adsorbing oxygen causes a different ratio between the cross transition and the auto-lonlsatlon peak than later adsorbing oxygen