Priv.-Doz. Dr. Mathias Schubert |
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| Address |
Curriculum vitae |
Research Activities |
Publications | Conferences |
Funded Projects |
News |
Ellipsometry Workgroup |
Projects
| Title | Interface-induced electro-optic properties of oxide semiconductor - ferroelectrica interfaces |
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| Sponsor | Deutsche Forschungsgemeinschaft, within Forschergruppe 404 "Oxydische Grenzflächen" | |
| Grant | SchuXXX/X-1 | |
| PI | Dr. M. Schubert, in collaboration with Dr. M. Lorenz | |
| Mit Hilfe der Laser-Plasmaabscheidung (PLD) werden Grenzflächen aus perowskitischen und wurtzitischen Materialien (Doppelheterostrukturen und Multischichten) hergestellt und bezüglich ihrer strukturellen, optischen und elektro-optischen Eigenschaften untersucht. Als Modellsystem wird in der ersten Phase Bariumtitanat (BaTiO3, Perowskit-Struktur) und Zinkoxid (ZnO, Wurtzit-Struktur) verwendet. Beide Systeme sind auf Grund ihrer besonderen materialphysikalischen Eigenschaften zukunftsorientierte Werkstoffe der Mikro- und Optoelektronik. Unser Ansatz besteht darin, schaltbare ionische Perowskit-Grenzflächenladungen mit nicht-schaltbaren ionischen Wurtzit-Grenzflächenladungen zu kombinieren, und deren Wechselwirkung zu studieren. Insbesondere soll der Einfluss der freien und gebundenen Grenzflächenladungen sowie der Realstruktur der Grenzflächen auf die Ausbildung ferroelektrischer Phasen innerhalb von Doppelheterostrukturen und Multischichten bestimmt werden. Fernziel ist die Exploration der neuartigen Materialkombinationen für Anwendungen in zukünftigen Bauelementstrukturen. | ||
| Duration | 01.01.2004 - 31.12.2006 | |
| Title | Functional optical thin films |
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| Sponsor | Flabeg GmbH & Co. KG, Furth im Wald, Germany | |
| Grant | ||
| PI | Dr. M. Schubert | |
| Control and optimization of functional optical coatings | ||
| Duration | 01.09.2003 - | |
| Title | Free-carrier properties and infrared dielectric functions of organic semiconductor layers |
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| Sponsor | JOANNEUM Research Forschungsgesellschaft mbH, Graz, Austria | |
| Grant | ||
| PI | Dr. M. Schubert | |
| Infrared spectroscopic ellipsometry for wavenumbers from 333 cm-1 to 4000 cm-1 is used as unique technique for determination of free-carrier properties and phonon mode frequencies in organic semiconducting materials in layered structures. The ability of this non-contact optical tool to extract these information from extremely thin layers is tested. Hall effect measurements are performed in order to obatin complementary information. Model lineshape analysis of the ellipsometry data upon the classical Drude approach aimes at quantification of the free-carrier densitiy, mobility, and effective mass parameter information. | ||
| Duration | 01.05.2001 - | |
| Title | In-situ-Ramanscattering and in-situ-Ellipsometry of flexible Cu-(In,Ga)-(Se,S)-thin-film solar cells |
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| Sponsor | Bundesministerium für Bildung und Forschung (BMBF) | |
| Grant | 03WKI09 (subgrant FKO) | |
| PI | Dr. M. Schubert, in collaboration with Dr. V. Riede | |
| The aim is the in-line, non-destructive, real-time control and feed-back for optimization of the optical and structural properties of the Cu-(In,Ga)-(Se,S)-thin-film solar cells during deposition at the Solarion GmbH Leipzig. A new combination of spectroscopic in-situ Raman scattering with in-situ spectroscopic ellipsometry shall be established. | ||
| Duration | 01.08.2001 - 31.12.2003 | |
| Title | Generalized infrared ellipsometry characterization of
lattice properties, |
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| Sponsor | Deutsche Forschungsgemeinschaft, within Schwerpunktprogram SPP1032 (1997-2002) | |
| Grant | Rh28/3-1, Rh28/3-2 | |
| PI | Dr. M. Schubert, in collaboration with Prof. Dr. B. Rheinländer | |
| The group III-nitrides ((BN), GaN, AlN, InN, AlGaN, InGaN, AlInN) are promising materials for many optoelectronic device applications over a large spectral region (~ 1.9 eV ... 6 eV (~9 ... 10 eV)). Generalized infrared ellipsometry is used here to study anisotropy of phonon properties and free-carrier parameters of MBE and MOVPE grown group-III nitride single layers and heterostructurs. Special attention is drawn to the anisotropy of carrier effective mass and optical mobility parameters. The infrared ellipsometry technique is non-destructive, and is being uniquely employed for characterization of wide band gap materials in this proposal. Effects of strain and alloying in binary, ternary, and quaternary layers can be studied and separated. Composition and free-carrier parameters are accessible without sample contamination. For example, focus is directed on p and n-type doping in cubic and hexagonal GaN and AlGaN single layers and superlattices, 2DEG effects at the GaN-AlGaN interface, effects at the SiC/GaN interface, and correlation of electrical and optical carrier parameters. | ||
| Duration | 01.01.1999 - 31.12.2002 | |
| Title | Infrared Spectroscopic Ellipsometry |
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| Sponsor | National Science Foundation | |
| Grant | DMI-9901510 (subgrant) | |
| PI | Dr. M. Schubert, in collaboration with Prof. Dr. J. A. Woollam (University of Lincoln-Nebraska, U.S.A.) | |
| This program investigates new applications of infrared ellipsometry with spectral range extension for characterization of microstructures in III-V materials. Lattice mode frequencies of Phosphides and Arsenides will be explored using a prototype rotating-analyzer spectroscopic ellipsometer setup. IR ellipsometry will be evaluated as a technique for studying spontaneously or synthetically ordered III- V semiconductors. In particular, spontaneous and synthetically ordering will be investigated in the (Al,Ga)InP and (Al,Ga)InAs systems. The investigations will aim to (1) measure and assign compound-material optical phonons and their polarization dependencies, (2) derive an anisotropic dielectric function model for the infrared response of ordered semiconductor compounds, and (3) compare the detected phonon modes with theoretical predictions. Synthetically ordered samples will cover a wide range of superlattice, and possibly embedded monolayer materials, with interest in characterization of the heterostructure optical properties and applicability for light emitting and detector systems. | ||
| Duration | 01.10.1999 - 30.09.2001 | |
| back to Staff | Last update August 29, 2003 (Leipzig) |