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Chemical reaction and interface formation on InAs(111)-Co surfaces
KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.ORCID iD: 0000-0003-1631-4293
KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
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2005 (English)In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 574, no 2-3, 181-192 p.Article in journal (Refereed) Published
Abstract [en]

We report a study of the initial interface formation of Co on InAs(1 1 1)A and B surfaces using high resolution photoelectron spectroscopy and scanning tunneling microscopy. We observe a strong chemical interaction between Co and, in particular, surface indium forming a metallic overlayer already below monolayer coverage. On annealed surfaces this overlayer agglomerates into islands, with a narrow size distribution. Furthermore, no two-dimensional electron gas is formed on InAs(1 1 1)A-Co in contrast to the clean surface.

Place, publisher, year, edition, pages
2005. Vol. 574, no 2-3, 181-192 p.
Keyword [en]
InAs(111), cobalt, photoelectron spectroscopy, surface reaction, core-level, fe films, accumulation, inas, band
National Category
Physical Sciences Chemical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-14485DOI: 10.1016/j.susc.2004.10.033ISI: 000226663000011OAI: oai:DiVA.org:kth-14485DiVA: diva2:332526
Note
QC 20100525 QC 20111206Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically 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.
Series
Trita-ICT/MAP AVH, ISSN 1653-7610 ; 2010:01
Keyword
angle-resolved photoemission, electronic structure, accumulation layer, adatoms, reconstruction
National Category
Condensed Matter Physics
Identifiers
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)
Opponent
Supervisors
Note
QC 20100910Available from: 2010-09-10 Created: 2010-09-08 Last updated: 2010-09-10Bibliographically approved
2. Initial stages of metal- and organic-semiconductor interface formation
Open this publication in new window or tab >>Initial stages of metal- and organic-semiconductor interface formation
2006 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

This licentiate thesis deals with the electronic and geometrical properties of metal-semiconductor and organic-semiconductor interfaces investigated by photoelectron spectroscopy and scanning tunneling microscopy.

First in line is the Co-InAs interface (metal-semiconductor) where it is found that Co is reactive and upon adsorption and thermal treatment it alloys with the indium of the substrate to form metallic islands, about 20 nm in diameter. The resulting broken bonds causes As entities to form which are loosely bond to the surface and evaporate upon thermal treatment. Thus, the adsorption of Co results in a rough interface.

Secondly the metal-free phthalocyanine (H2PC) - titanium dioxide interface (organic-semiconductor) is investigated. Here it is found that the organic molecules arrange themselves along the substrate rows upon thermal treatment. The interaction with the TiO2 is mainly with the valence Π-electrons in the molecule causing a relatively strong bond, but this interaction is short range as the second layer of molecules retains their molecular character. This results in an ordered adsorption but limited mobility of the molecules on the surface prohibiting well ordered close packed layers. Furthermore, the hydrogen atoms inside the cyclic molecule leave the central void upon thermal treatment.

The third case is the H2PC-InAs/InSb interface (organic-semiconductor). Here ordered overlayer growth is found on both substrates where the molecules are preferentially adsorbed on the In rows in the [110] direction forming one-dimensional chains. The InSb-H2PC interface is found to be weakly interacting and the bulk-like molecular character is retained upon both adsorption and thermal treatment. On the InAs-H2PC interface, however, the interaction is stronger. The molecules are more affected by the surface bond and this effect stretches up a few monolayers in the film after annealing.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. 47 p.
Series
Trita-FTE, ISSN 0284-0545 ; 0601
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-3911 (URN)
Presentation
2006-04-07, Sal C1, KTH-Electrum, Isfjordsgatan 22, Kista, 10:15
Opponent
Supervisors
Note
QC 20101122Available from: 2006-04-07 Created: 2006-04-07 Last updated: 2010-11-22Bibliographically approved

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