Surface diffusion of Cs on Si(100)-2 × 1

Milne, Richard; Azim, M.; Persaud, Rajendra; Venables, J. A.

doi:10.1016/0039-6028(95)00512-9

Cited by 11 publications

(6 citation statements)

References 25 publications

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“…It has been shown in the similar case of Cs on Si͑100͒, that the diffusion constant and the activation energy are, respectively, 10 Ϫ8 cm 2 / s Ϫ1 , 18 and 0.47 eV. This means that diffusion is impossible at LT. On the other hand, diffusion is very efficient at RT, and can allow the cesium atoms to reach energetically favorable sites.…”

Section: Surface Optical Transitionsmentioning

confidence: 91%

Formation of the Cs/GaAs(001) interface: Work function, cesium sticking coefficient, and surface optical anisotropy

Kierren¹,

Paget²

1997

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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We have studied at room temperature (RT) and at near liquid-nitrogen temperature [low temperature (LT)], the adsorption of cesium on clean gallium-rich GaAs(001) prepared by sulfide passivation, and annealing in ultrahigh vacuum. We monitor the optical transitions of gallium surface dimers, using reflectance anisotropy spectroscopy (RAS), and the changes of work function and cesium sticking coefficient. The clear correlations between these three quantities allow us to distinguish three adsorption phases: (i) At LT and up to 0.7 ML coverage, cesium adsorption induces a decrease of the RA signal, which perfectly corresponds with the work function decrease. The RA decrease is, therefore, caused by the surface dipole due to charge transfer from cesium to the solid. (ii) At RT, for a coverage smaller than 0.15 ML, both the RA signal and the work function change are different from their LT behavior, so that a distinct adsorption process occurs. This indicates that cesium diffuses to specific surface sites at which the bonding is different. (iii) At a coverage larger than 0.7 ML, and independently on adsorption temperature, no charge transfer to the solid occurs, since no change of RA spectrum and work function is observed. The cesium sticking coefficient is reduced by a factor of 2. Comparison with results obtained on As-decapped GaAs(001) shows the similarity of the formation of the interface for the two surfaces. However, the results are clearer for the surface prepared by sulfide passivation, which seems to be of higher quality.

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Section: Surface Optical Transitionsmentioning

confidence: 91%

Formation of the Cs/GaAs(001) interface: Work function, cesium sticking coefficient, and surface optical anisotropy

Kierren¹,

Paget²

1997

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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show abstract

“…It is seen that the transition occurs in the 200 to 300 K temperature range since, in this range, G drops by a factor of 1.6, while it does not change for both lower and higher temperatures. Using the value of this temperature, a standard calculation yields the value of the activation energy for cesium surface diffusion, which is found to be of 0.7 eV that is, slightly more than the value of 0.47 eV obtained on Si(001) [7].…”

Section: Disorder±order Transitionmentioning

confidence: 79%

“…The estimated diffusion energy is 0.5 eV. It is generally admitted that the decrease of activation energy with increasing coverage reveals a repulsive interaction between the adatoms [7,9]. This repulsive interaction may occur either because of the large size of the cesium atom with respect to the size of the surface sites, or because of the repulsive electrostatic interaction between the cesium-induced surface dipoles.…”

Section: Disorder±order Transitionmentioning

confidence: 97%

“…This result comes from two distinct observations. Firstly, electron microscopy studies on the similar Cs/Si(001) system [7] have shown that at RT cesium diffusion is possible over macroscopic distances, but that the activation energy for Cs diffusion on Si is large, of the order of 0.47 eV, so that even a slight temperature decrease has an extremely large effect on the diffusion constant. Secondly, the observed changes of the RA spectrum under Cs adsorption are very different for RT and for LT adsorption [5], which indicates that the morphology of the cesium overlayer is very different for the two temperatures.…”

Section: Principles and Experimentalmentioning

confidence: 99%

“…In the past, electron microscopy [7] or laser ablation [11] have been used to probe diffusion over macroscopic distances. Here, we show that RA spectroscopy is able to probe diffu-Optical Investigation of Submonolayer Phase Transitions of Cs on GaAs(001) 393 Fig.…”

Section: Disorder±order Transitionmentioning

confidence: 99%

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