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Initial stages of metal- and organic-semiconductor interface formation
KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
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: urn:nbn:se:kth:diva-3911OAI: oai:DiVA.org:kth-3911DiVA: diva2:9982
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
List of papers
1. Chemical reaction and interface formation on InAs(111)-Co surfaces
Open this publication in new window or tab >>Chemical reaction and interface formation on InAs(111)-Co surfaces
Show others...
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.

Keyword
InAs(111), cobalt, photoelectron spectroscopy, surface reaction, core-level, fe films, accumulation, inas, band
National Category
Physical Sciences Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-14485 (URN)10.1016/j.susc.2004.10.033 (DOI)000226663000011 ()
Note
QC 20100525 QC 20111206Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
2. Bonding of metal-free phthalocyanine to TiO2(110) single crystal
Open this publication in new window or tab >>Bonding of metal-free phthalocyanine to TiO2(110) single crystal
2006 (English)In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, Vol. 90, no 20, 3602-3613 p.Article in journal (Refereed) Published
Abstract [en]

The metal-free phthalocyanine interface formation on rutile TiO2(110) is investigated using scanning tunneling microscopy and photoelectron spectroscopy. The molecules are adsorbed flat on the surface, centered on the substrate oxygen rows. High-resolution core-level C1s spectroscopy indicates a strong difference between the second layer and the first monolayer bonding to the surface. The C1s core-level from the second layer has a bulk-like line shape whereas the first layer shows a strongly modified line profile. Upon thermal treatment, changes in the N1s core level line profile points to dehydrogenation of the center of the molecule.

Keyword
Adsorption; Metal-free phthalocyanine; Titanium dioxide; Dehydrogenation; Heat treatment; Scanning tunneling microscopy; Single crystals; Titanium oxides; X ray photoelectron spectroscopy; Metal-free phthalocyanine; Monolayer bonding; Substrate oxygen; Nitrogen compounds
National Category
Other Engineering and Technologies not elsewhere specified
Identifiers
urn:nbn:se:kth:diva-7778 (URN)10.1016/j.solmat.2006.06.054 (DOI)000241483200011 ()2-s2.0-33749134840 (Scopus ID)
Note
QC 20100812Available from: 2007-12-10 Created: 2007-12-10 Last updated: 2010-11-22Bibliographically approved
3. Self-ordering of metal-free phthalocyanine on InAs(100) and InSb(100)
Open this publication in new window or tab >>Self-ordering of metal-free phthalocyanine on InAs(100) and InSb(100)
2006 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 18, no 48, 10707-10723 p.Article in journal (Refereed) Published
Abstract [en]

The adsorption and surface ordering of metal-free phthalocyanine (H2PC) on InAs(100)(4 x 2)/c(8 x 2) and InSb(100) c(8 x 2) is investigated using scanning tunnelling microscopy (STM) and synchrotron based photoelectron spectroscopy. The two systems show structural similarities; at submonolayer coverage the preferred adsorption site of H2PC is on top of the In rows, and above 1 monolayer and after thermal treatment the first molecular layer is ordered in a densely packed 'x3' structure observed with both low energy electron diffraction and STM.

The electronic properties and the surface bonds of the two systems are quite different: the InAs-H2PC interface is semiconducting after room temperature adsorption but becomes metallic upon thermal treatment whereas InSb(100) H2PC is semiconducting at all preparations. These differences are reflected in pronounced differences in the C 1s line shape between the two systems. N 1s core level spectra from both surfaces reveal deprotonation of the molecules, i.e. the central hydrogen atoms are lost upon thermal treatment.

Keyword
Adsorption; Crystalline materials; Electron diffraction; Electronic properties; Heat treatment; Photoelectron spectroscopy; Scanning tunneling microscopy; Semiconducting indium compounds; Surface chemistry; Adsorption sites; Deprotonation; Phthalocyanine; Surface bonds; Pigments
National Category
Other Engineering and Technologies not elsewhere specified
Identifiers
urn:nbn:se:kth:diva-7782 (URN)10.1088/0953-8984/18/48/001 (DOI)000242650600002 ()2-s2.0-33846096421 (Scopus ID)
Note
QC 20100812Available from: 2007-12-10 Created: 2007-12-10 Last updated: 2010-11-22Bibliographically approved

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