Optical study of surface dimers on sulfur-passivated (001)GaAs

Berkovits, V. L.; Paget, D.

doi:10.1063/1.108390

Cited by 40 publications

(27 citation statements)

References 19 publications

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“…This quality is very good, since the RA signal is large with respect to other cases studied previously. 12 In the same way, the RA dimer line is narrow, and its width decreases at LT, which indicates that little inhomogeneous broadening due to defects is present. Fig.…”

Section: A Experimental Setup and Proceduresmentioning

confidence: 87%

“…Its spectral shape is similar to the one obtained for the ͑4ϫ2͒ reconstructed surface, either on in situ molecular beam epitaxy grown material, 11 or on As-decapped GaAs. 12,14 The starting surface is, therefore, characterized by a gallium-rich reconstruction, probably the ͑4ϫ2͒ one that has been obtained using the same preparation procedure. 15 The RA signal observed between 1.6 and 2.9 eV reflects the optical anisotropy induced by internal optical transitions of gallium dimers, 11 and will be used in the following as a probe for interface formation.…”

Section: A Experimental Setup and Proceduresmentioning

confidence: 99%

“…12 The UHV chamber base pressure is in the low 10 Ϫ11 mbar range. Cesiation was performed under a pressure in the same range using a thoroughly outgassed cesium getter.…”

Section: A Experimental Setup and Proceduresmentioning

confidence: 99%

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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: A Experimental Setup and Proceduresmentioning

confidence: 87%

Section: A Experimental Setup and Proceduresmentioning

confidence: 99%

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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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“…However, its origin is still under discussion. While Hughes et al [25] attributed its occurrence to a transition involving sulfur dimers, other explanations like transitions within Ga-S bonds are also possible [26].…”

Section: Reflection Anisotropy Spectroscopymentioning

confidence: 99%

Optical Anisotropy of Organic Layers Deposited on Semiconductor Surfaces

Kampen

Paraian

Rossów

et al. 2001

phys. stat. sol. (a)

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The optical properties of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) films grown by organic molecular beam deposition (OMBD) on passivated Si and GaAs substrates were determined using variable angle spectroscopic ellipsometry (VASE) and reflectance anisotropy spectroscopy (RAS). All PTCDA layers deposited at room temperature with a low deposition rate of about 0.2 nm/min are strongly optically anisotropic and are treated as uniaxial. From the VASE measurements the in-plane refractive indices and extinction coefficients are found to be larger than the respective out-of-plane optical constants in the spectral range from 300 nm (4.13 eV) to 1700 nm (0.73 eV). The altogether lower refractive indices of PTCDA films grown on GaAs indicate a lower density of the films which can be explained by the film structure. RAS results for PTCDA films grown on GaAs show features which can be attributed to transitions between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). GaAs features near the E 1 gap remain unchanged upon PTCDA deposition indicating that the surface reconstruction of the GaAs substrate stays intact.

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“…A number of authors have contributed to the development of this point of view, first to superparticles in higher dimensional spacetimes, and then to heterotic strings, membranes and higher-dimensional extended objects [6, 7, 8, 9, 11, 12, 10, 13, 5, 28, 14, ?]. In addition, this new approach has much in common with various twistor-like formulations of superparticles and extended supersymmetric objects [18,19,22,24,25,26]. One of the most interesting objects to study is undoubtedly the heterotic string in tendimensional spacetime.…”

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confidence: 99%