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1

Potential Energy Surfaces for H Adsorbed at 4H-SiC{0001} Surfaces

100%

Wachowicz E., Kiejna A.

Acta Physica Polonica A

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2013

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vol. 124

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issue 5

765-767

EN

The constant adsorption energy surfaces for hydrogen adsorbed on Si- and C-terminated hexagonal 4H-SiC{0001} surfaces have been calculated within density functional theory framework. The two unreconstructed and one reconstructed √3 × √3 surfaces were taken into account. We show that on all surfaces there is a global energy minimum indicating the most favourable adsorption site corresponding to H atom adsorption on-top of the topmost substrate layer atom. In case of reconstructed surface, there is another small and shallow local minimum. Moreover, the diffusion barrier is much higher at reconstructed surface than at unreconstructed ones.

2

Ab Initio Studies of Al and Ga Adsorption on 4H-SiC{0001} Surfaces

81%

Wachowicz E., Sznajder M., Majewski J.

Acta Physica Polonica A

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2012

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vol. 122

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issue 6

1045-1048

EN

Changes in the atomic and electronic structure of Si- and C-terminated 4H-SiC{0001} surfaces resulting from aluminium and gallium adsorption have been studied within density functional theory framework. Al and Ga coverages ranging from a submonolayer to one monolayer were considered. Our results show that Al binds more strongly to both surfaces than Ga. The binding is stronger to the C-terminated surface for both metals. The sites occupied by Al and Ga atoms at 1 monolayer are different and it is due to a different charge transfer from metal to the substrate.

3

Interaction of Hydrogen with Vanadium Layers Preadsorbed on Tungsten Field Emitter Tip

81%

Błaszczyszyn R., Wachowicz E., Błaszczyszynowa M.

Acta Physica Polonica A

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1998

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vol. 93

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issue 5-6

763-773

EN

Interaction of hydrogen with vanadium layers preadsorbed on a thermally cleaned tungsten field emitter was studied at room temperature and 78 K through measurements of the total work function changes. An increase in the work function followed by its slight decrease at higher exposure can be understood taking into account the possibility of negatively (β^{-}) and positively (β^{+}) polarized adspecies formation on thin vanadium layer. This process leads to vanadium hydride formation. The work function results suggest that hydrogen diffusion into the vanadium layer is meaningful at room temperature. Thermal desorption of hydrogen adsorbate carried out within the temperature range 409-461 K from thin vanadium layer (Θ_{V} = 40) provided a value of 127 ± 6 kJ/mol for the activation energy for desorption.

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3 Acta Physica Polonica A

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1 Kiejna A.

1 Majewski J.

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Potential Energy Surfaces for H Adsorbed at 4H-SiC{0001} Surfaces

Ab Initio Studies of Al and Ga Adsorption on 4H-SiC{0001} Surfaces

Interaction of Hydrogen with Vanadium Layers Preadsorbed on Tungsten Field Emitter Tip