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Pb induced charge accumulation on InAs(111)B
KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
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2007 (English)In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 601, no 15, 3246-3252 p.Article in journal (Refereed) Published
Abstract [en]

The Pb/InAs(111)B interface has been studied by synchrotron radiation photoelectron spectroscopy (SR-PES) of valence band and ln4d, As3d and Pb5d core levels. Room temperature deposition of similar to 1 ML of Pb on InAs(I I I)B leads to an ordered overlayer that induces a metallic channel at the surface, as seen through a weak emission in the vicinity of the Fermi level. Its narrow localization in reciprocal space supports the formation of a two-dimensional free electron gas (2DEG) in the surface region. It is proposed that the adsorbed metal layer swaps the initial polarisation of the surface and thus pulls electrons back to the surface. This charge re-arrangement increases the charge density in the accumulation layer and reduces the screening length and thus the depth of the potential well at the surface.

Place, publisher, year, edition, pages
2007. Vol. 601, no 15, 3246-3252 p.
Keyword [en]
photoelectron spectroscopy, indium arsenide, accumulation layer, by-layer growth, low-temperature, surfaces, spectroscopy, adsorption, interface, states
URN: urn:nbn:se:kth:diva-16887DOI: 10.1016/j.susc.2007.05.058ISI: 000248881900013ScopusID: 2-s2.0-34447504892OAI: diva2:334930
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2010-09-10Bibliographically approved
In thesis
1. Electronic structure of clean and adsorbate-covered InAs surfaces
Open this publication in new window or tab >>Electronic structure of clean and adsorbate-covered InAs surfaces
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is the result of investigations regarding the processes in InAs III-V semiconductor surfaces induced by additional charge incorporated by adsorbates. The aim of the project is to study the development of the accumulation layer on the metal/InAs(111)A/B surfaces and its electronic structure. InAs(111)A is indium-terminated and InAs(111)B is arsenic-terminated. In addition, InAs(100) is also studied. These three substrates are different; InAs(111)A has a (2x2)-termination, explained by an indium vacancy model, and the clean surface exhibits a two-dimensional electron gas (2DEG). InAs(111)B(1x1) is bulk-truncated and unreconstructed and does not host a 2DEG. InAs(100)(4x2)/c(8x2) exhibits a more covalent character of the surface bonds compared to InAs(111)A/B, and the surface is terminated by a complex reconstruction. Photoelectron spectroscopy and LEED (low energy electron diffraction) have been used as the main tools to study surfaces with sub-monolayer to monolayer amounts of adsorbates. A photoemission peak related to a two-dimensional electron gas appears close to the Fermi level. This 2DEG has in most cases InAs bulk properties, since it is located in the InAs conduction band. A systematic study of core levels and valence bands reveals that the appearance of the 2DEGs is a complex process connected to the surface order. Adsorption of lead, tin or bismuth on InAs(111)B(1x1) induces emission from a 2DEG, but only at monolayer coverage and when the surface is ordered. Cobalt reacts strongly with InAs forming InCo islands and no accumulation is observed.

Examination of Cs/InAs(111)B does not reveal any 2DEG and the surface reaction is strongly related to the clean surface stabilization process. Examination of the In-terminated InAs(111)A(2x2) surface shows that In reacts strongly with cobalt and tin adatoms and with oxygen in cases of large exposure, which decreases the 2DEG intensity, while adatoms of cesium and small doses of oxygen enhance the emission from the 2DEG. InAs(100) is terminated with one kind of atom - the InAs(100)(4x2)/c(8x2) is indium terminated. Bismuth creates dimers on the surface and a 2DEG is observed.

More generally, this thesis describes some of the general physical background applied to surface science and 2DEG. The first part is a general overview of the processes on the surface. The second part concentrates on the methods related to preparation of samples, and the third part on the measurement methods. The photoelectron spectroscopy part concerns the theory used in mapping electronic structure. The inserted figures are taken from different experiments, including results for InAs(111)A not previously published.



Place, publisher, year, edition, pages
Stockholm, Sweden: KTH, 2010. 156 p.
Trita-ICT/MAP AVH, ISSN 1653-7610 ; 2010:01
angle-resolved photoemission, electronic structure, accumulation layer, adatoms, reconstruction
National Category
Condensed Matter Physics
urn:nbn:se:kth:diva-24423 (URN)978-91-7415-702-4 (ISBN)
Public defence
2010-10-01, Ka-Aula, Isafjordsg.39, Forum, Kista, 10:20 (English)
QC 20100910Available from: 2010-09-10 Created: 2010-09-08 Last updated: 2010-09-10Bibliographically approved

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