Selected Publications - 2008:
1) X-ray Characterization of the Lattice Perfection of Heteroepitaxial SIS Structures
P. Zaumseil, G. Weidner and T. Schroeder
IHP, Im Technologiepark 25, D-15236 Frankfurt (Oder), Germany
Solid State Phenomena Vols. 131-133 (2008) pp. 619-624
The crystallographic structure of semiconductor - insulator - semiconductor (SIS) structures consisting of a Si(111) substrate, Prs2O3 and Y2O3 insulating high-k materials, and Si cap layer was characterized by a combination of X-ray pole figure measurement and conventional X-ray diffraction. Oxide and Si cap layer were grown by molecular beam epitaxy and have the same 111 lattice orientation as the substrate. It is shown that the oxide layers grow in a type B stacking orientation only, while the epi-layer exhibits exclusively the same type A orientation as the substrate. A small fraction of the epi-Si lattice was identified with 511 netplanes parallel to the surface. TEM investigations identify these areas as structural defects between Si grains of differing stacking sequence.
PDF published by Solid State Phenomena available online at www.scientific.net
2) Lattice engineering of dielectric heterostructures on Si by isomorphic oxide-on-oxide epitaxy
T. Schroeder 1, I. Costina 1, P. Storck 2, A. Wilke 1, O. Seifarth 1, A. Giussani 1,
H.-J. Müssig 1, and P. Zaumseil 1
1 IHP, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
2 SILTRONIC AG, Hanns-Seidel-Platz 4, 81737 München, Germany
Journal of Applied Physics 103, 084102 (2008)
(Received 13 November 2007; accepted 11 February 2008; published online 17 April 2008)
The isomorphic oxide-on-oxide epitaxy of Y2O3 on cubic Pr2O3(111) / Si(111) support systems was studied to tailor the lattice constant of the dielectric heterostructure for future integration of functional semiconductors via heteroepitaxy on the Si material platform. Laboratory- and synchrotron-based x-ray diffraction was applied to study the structure as well as the epitaxy mechanism of Y2O3 on the cubic Pr2O3(111) / Si(111) support. The oxide heterostructure is characterized by the formation of closed single crystalline cubic Y2O3(111) films which are in especial twin-free and exhibit an exclusive type B epitaxy orientation on the cubic Pr2O3(111) / Si(111) system. Nondestructive depth profiling x-ray diffraction reveals that the epitaxy mechanism of Y2O3 films on cubic Pr2O3(111) / Si(111) systems is determined by the formation of a transition layer with variable lattice parameters, changing with increasing depth from the Y2O3 values towards the parameters of the isomorphic Pr2O3 support. This transition layer thus effectively accomodates the relatively large lattice misfit of 4.8% between the isomorphic oxides. X-ray photoelectron depth profiling studies are applied to discriminate between strain and interface reaction effects in the formation of this transition region at the Y2O3 / Pr2O3 boundary. An interface reaction, forming a compositionally graded Pr2-xYxO3 (x=0–2) buffer layer at the oxide/oxide boundary, results as the most probable physical origin. © 2008 American Institute of Physics.
PDF published by Journal of Applied Physics available online at jap.aip.org
3) The influence of lattice oxygen on the initial growth behavior of heteroepitaxial Ge layers on single crystalline PrO2(111)/Si(111) support systems
A. Giussani 1, O. Seifarth 1, P. Rodenbach 1, H.-J. Müssig 1, P. Zaumseil 1, T. Weisemöller 2, C. Deiter 2, J. Wollschläger 2, P. Storck 3,
and T. Schroeder 1
1 IHP, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
2 University of Osnabrück, Barbarastrasse 7, 49076 Osnabrück, Germany
3 SILTRONIC AG, Hanns-Seidel-Platz 4, 81737 München, Germany
Journal of Applied Physics 103, 084110 (2008)
(Received 30 October 2007; accepted 18 December 2007; published online 23 April 2008)
A combined structure and stoichiometry study on the growth behavior of single crystalline Ge(111) layers on PrO2(111) / Si(111) heterostructures is presented. Ex situ x-ray diffraction techniques indicate that the interaction between Ge and PrO2(111) results in a complete reduction of the buffer oxide to a cubic Pr2O3(111) film structure. In situ reflection high energy electron diffraction, x-ray and ultraviolet photoelectron spectroscopy studies demonstrate that this chemical reduction of the oxide support occurs during the initial Ge growth stage. The interaction of PrO2 with Ge results in the formation of an amorphous Ge oxide layer by the diffusion of lattice oxygen from the dielectric to the forming semiconductor deposit. After the complete conversion of PrO2 to cubic Pr2O3, the supply of reactive lattice oxygen is exhausted and the continuous Ge deposition reduces the initially formed amorphous GeO2-like film to GeO. The sublimation of volatile GeO uncovers the single crystalline cubic Pr2O3(111) film surface which provides a thermodynamically stable template for elemental Ge heteroepitaxy. A Volmer–Weber growth mode is observed which results after island coalescence in the formation of atomically smooth, single crystalline Ge(111) layers. © 2008 American Institute of Physics.
PDF published by Journal of Applied Physics available online at jap.aip.org
4) X-ray measurement of the tetragonal distortion of the oxide buffer layer in Ge/Pr2O3/Si(1 1 1) heteroepitaxial structures
P. Zaumseil
IHP, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
J. Phys. D: Appl. Phys. 41 (2008) 135308 (7pp)
An epi-Ge/Pr2O3/Si(1 1 1) layer structure produced by consecutive steps of epitaxial deposition and annealing is used to demonstrate a technique to measure the tetragonal distortion of the oxide buffer layer with high precision. It uses /2 x-ray diffraction scans on different netplanes tilted by an angle χ sideways to the diffraction plane and plotting a calculated ‘cubic’ lattice constant versus cos2χ. The obtained linear dependence gives the
in-plane and off-plane lattice constants at cos2 χ = 0 and cos2 χ = 1, respectively. For the investigated structure with a pronounced A–B–A stacking sequence in the (1 1 1) direction, this method has the advantage that oxide reflections are not superimposed to reflections of the Si substrate and the epi-Ge layer. This increases the sensitivity for thin oxide layers significantly. The method was also successfully used to characterize the tetragonal distortion of uncovered PrO2 layers on the Si(1 1 1) substrate.
PDF published by Journal of Physics D: Applied Physics available online at www.iop.org/EJ/journal/JPhysD
5) Epitaxy of single crystalline PrO2 films on Si(111)
T. Weisemoeller1, C. Deiter1, F. Bertram1, S. Gevers1, A. Giussani2, P. Zaumseil2,T. Schroeder2, and J. Wollschläger1
1 Department of Physics, University of Osnabrück, Barbarastrasse 7, D-49069 Osnabrück, Germany
2 IHP, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
Applied Physics Letters 93, 032905 (2008)
(Received 23 February 2008; accepted 23 June 2008; published online 24 July 2008)
A film of praseodymium sesquioxide with hexagonal structure, that has been deposited on Si(111) by molecular beam epitaxy, was annealed in oxygen atmosphere to obtain a PrO2 film for improved heteroepitaxy as buffer dielectric for alternative semiconductor layer integration. The film structure is characterized by x-ray diffraction and x-ray reflectometry. The film is single crystalline with Fm3m (fluorite) structure. It is B oriented with respect to Si and has lattice constants close to bulk PrO2. The cubic lattice of the PrO2 film is slightly distorted due to residual oxygen vacancies which increase the diameter of Pr ions. © 2008 American Institute of Physics.
PDF published by Applied Physics Letters available online at apl.aip.org/apl/
6) A complex x-ray characterization of heteroepitaxial silicon/insulator/silicon(111) structures
P. Zaumseil and T. Schroeder
IHP, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
Journal of Applied Physics 104, 023532 (2008)
(Received 12 February 2008; accepted 20 May 2008; published online 29 July 2008)
The application of new semiconductor materials deposited on Si substrates via heteroepitaxial growth on oxide buffer layers is one possible way to improve performance and functionality of future Si-based integrated circuits. It is demonstrated how the crystallographic structure of semiconductor-insulator-semiconductor (SIS) structures consisting of a Si(111) substrate, Pr2O3 and Y2O3 insulating buffer layers, and Si cap layer can be characterized by different x-ray techniques. Especially a combination of pole figure measurement with conventional x-ray diffraction scans and reciprocal space mapping is applied to study the in-plane orientation of the oxide and epi-Si layer relative to the Si substrate, the strain state of the individual layers, and the structural perfection of the epi-Si film. Oxide and Si cap layer were grown by molecular beam epitaxy and have the same (111) lattice orientation as the substrate. It is shown that the oxide layers grow in a type B stacking orientation only, while the epilayer exhibits exclusively the same type A orientation as the substrate. Pole figure measurements reveal an unexpected orientation of a small fraction of the epi-Si lattice. This behavior was explained by microtwins as the major defect mechanism in the epi-Si layer. The proposed combination of x-ray techniques allows a relatively fast, integrated, and nondestructive analysis of the epi-Si layer.
PDF published by Journal of Applied Physics available online at jap.aip.org