Refine
Year of publication
Document Type
Keywords
- dielectric (3)
- organic field effect transistor (2)
- AION buffer (1)
- Aluminium (1)
- Annealing-process (1)
- CIS-Solarzellen (1)
- Corrosion (1)
- CuInS2 films (1)
- Fluorotitanates (1)
- Fluorozirconates (1)
- Kelvin-AFM (1)
- NEXAFS (1)
- OFET (1)
- PEEM (1)
- Photoemission electron microscopy (PEEM) (1)
- Photoemission-electron-microscopy (PEEM) (1)
- Polypyrrole (1)
- Röntgen-Photoelektronenspektroskopie (1)
- Scanning Kelvin probe microscopy (SKPM) (1)
- Tiefenprofilierung (1)
- X-Ray photoelectron spectroscopy (1)
- X-ray absorption spectroscopy (1)
- X-ray photoelectron spectroscopy (1)
- block copolymers (1)
- buffer layer (1)
- catalytic oxidation (1)
- high-k (1)
- magnetic nano particles (1)
- microscopic (1)
- pattern (1)
- photo-emission-electron-microscopy (1)
- photoelectron emission microscopy (PEEM) (1)
- photoemission electron microscopy (PEEM) (1)
- preparation (1)
- semiconductor (1)
- small mu (1)
- spectrocsopic (1)
- stochastic (1)
Institute
Microscopic and spectroscopic characterization of interfaces and dielectric layers for OFET devices
(2009)
Photo-Emission-Electron-Microscopy for Characterization of an Operating Organic Electronic Device
(2006)
Scanning Kelvin probe and photoemission electron microscopy of organic source-drain structures
(2004)
Wir haben CuInS2 (CIS) unterschiedlicher Herstellung (Koverdampfung, Sputtern, Pulsed Laser Deposition, CIS auf Kupferband aufgebracht) untersucht. Neben Tiefenprofilen (durch Sputtern) der Elementverteilung dieser Proben wurden der Einfluss der Temperatur, von aufgedampftem Kupfer und Indium, ebenfalls bei verschiedenen Temperaturen, auf das Verhalten der Stöchiometrie mit spektroskopischen Methoden (XPS, UPS) studiert. Parallel dazu wurde das Verhalten von im Vakuum aufgedampften ZnS und die entsprechenden Oberflächenreaktionen in Abhängigkeit von der Temperatur untersucht und charakterisiert, so dass Aussagen über die Optimierung und Anpassung von Präparationsbedingungen und Parametern zur Herstellung von erstens reinem CIS und zweitens von Mischkristallen des Typs Zn2-xCuxInxS2 möglich werden. Zwischen den beiden Endgliedern ZnS und CuInS2 besteht bis auf einen Phasenübergang bei etwa 80% CIS lückenlose Mischbarkeit gemäss Zn2-xCuxInxS2 (Bente: Chem.Erde (1991)). Die elektronische Bandlücke dieser Mischkristalle lässt sich im Vergleich zu reinem CuInS2 in einem Bereich von 3,67 eV (ZnS) bis 1,55 eV (CuInS2) variieren. Damit besteht die Möglichkeit, durch kontrollierte Änderung der Zusammensetzung der Schichten die Effizienz von Solarzellen aus diesem Material zu optimieren.
Microscopic and Spectroscopic Characterization of Interfaces and Dielectric Layers for OFET Devices
(2008)
X-ray photoemission spectroscopy of Aluminium Oxynitride on Si(001) and the rise as buffer layers
(2008)
Praseodymium oxide (PrxOy) is one of the candidate as high-k transistor gate dielectrics, but aluminium oxynitride (AlxONy) as buffer layer is needed to prevent diffusions from the silicon into PrxOy and to hinder charge injection from the semiconductor into the insulator. The thermal stability and thickness dependence of aluminum oxynitride (AlxONy) has been investigated by synchrotron radiation photoemission spectroscopy (SR-PES). AlxONy layers were prepared by low energy ion-beam assisted deposition (LE-IBAD) at room temperature on a silicon substrate cleaned with HF-acid. Aluminium oxynitride is stable till 800∘C. From photoemission spectra we can assess that silicon oxynitride is built as first and then the growth of AlxONy follows. Resonant inelastic X-ray scattering measurements with synchrotron radiation have been performed. The combination of X-ray absorption spectroscopy (XAS) and RIXS make possible to determinate the band gap of AlxONy.
In order to optimize organic field effect transistors, the characterization of surfaces in terms of their roughness or chemical composition is very important. We report on high resolution spectromicroscopic mapping of organic thin film transistors by photoemission electron microscopy (PEEM). It was shown that PEEM is a useful technique to characterize the surface morphology (roughness), the chemical homogeneity or the composition of structures in between the source and drain electrodes. Mapping of surface potentials, especially at the interface electrode/channel is possible. We compare different preparation methods and the characterization at applied voltages is also shown.
The transistors itself were prepared by a new low cost method. The electrodes for source and drain have been prepared by a plotting method with colloidal graphite or carbon black as the conducting material. P3HT was used as active layer and has been prepared by spin coating.
Photoelectron spectroscopy and microscopy on magnetic nano particles embedded into block copolymers
(2005)
The formation of metallic nano particles stored in thin films of block copolymers has been investigated by means of synchrotron radiation based photoemission spectroscopy (PES) and microscopy (PEEM). Empty channels in poly(styrene-block-4-vinylpyridine) copolymer with diameters of tens of nanometers filled with CrO2, Cr2O3 and Ni provide ideal bases for performing electron spectroscopy with energy and lateral resolution on magnetic nano particles. We present UPS, XPS, NEXAFS spectra and PEEM images on and off the C 1s, Cr 2p, Ni 2p resonances and discuss the geometric and electronic structure of such compounds. The synchrotron radiation was delivered from the U49/2 beamline at BESSY II.
Surface potential imaging with Photoemission-electron-microskopy (PEEM) in high lateral resolution is introduced as a new tool for the characterisation of organic transistor structures. We use source-drain- electrode structures of different organic materials like carbon-black or graphite plotted on a printing foil. Semiconducting regioregular Poly(3-Hexylthiophene-2,5-diyl) (P3HT) was deposited by spin coating. For our measurements we used radiation of a standard high pressure Hg-lamp (4,9 eV) and synchrotron radiation at the BESSYII-U49/2 beam line. In contrast to Kelvin-AFM measurements of the surface potential, PEEM enables a simultaneous analysis of chemical composition by photoelectron spectroscopy. UPS, for example, at zero potential gives information on chemical homogeneity of the organic semiconductor in lateral resolution. PEEM images at applied voltages, compared with UPS-spectra, gives informations on doping profiles in the semiconductor, for example. In conclusion, PEEM should be a complementary method for characterisation of the surface potential with Kelvin-AFM. In addition, PEEM gives opportunities for measurements of chemical composition in the working state of the transistor (applied voltages).
We study the chemical stability and electrical properties of Pr-oxides-SiC MIS stacks. In MISFET devices for high power applications the electric field scaling at the interface between semiconductor and insulator is determined by the ratio of their permittivity values. A high-k material can be used to optimize the performance of such devices. In previous studies we had to understand that the chemical reactivity of the PrOx/SiC interface causes a destructive interaction yielding silicate and graphite formation as well as poor electrical performance after direct deposition of PrOx onto SiC. Therefore we introduced an additional chemically inert layer and in this contribution we focus on PrOx/AlON as a suitable insulator stack. In our spectroscopic investigations we recognized a stable AlON/3C-SiC interface even for annealing steps up to 900∘C. First electrical characterizations are performed on Si substrates and we find a strong improvement in the leakage current by several orders of magnitude down to values of 10−7 A/cm2 at an EOT of 4nm and interface state densities of mean values of 5*1011/eVcm2. We also report on our ongoing electrical characterization of such stacks on SiC substrates. This work is supported by Deutsche Forschungsgemeinschaft within priority program 1157 (DSCH 745/9-2).
We introduce a recently developed novel polypyrrole-based coating, which can be formed on the aluminium surface from an aqueous pyrrole solution of fluorozirconic and fluorotitanic acid neutralised with zinc oxide. The composite layer consists of polypyrrole (Ppy) chemisorbed on titanium and zinc oxides and exhibits advanced corrosion resistance. For the investigation of the structure and the corrosion mechanism of the composite corrosion resistant layer we use a photo-electron emission microscope (PEEM). PEEM is especially suitable because it can deliver topographic contrast as well as elemental contrast and chemical information in connection with a variable X-ray source. Additionally, in order to investigate further the corrosion mechanism, but also the role of the alloy in the corrosion process, we examine the aluminium samples with SEM/EDX. The structure of the corrosion resistant layer was investigated before and after accelerated corrosion tests. Our results pointed out the important role of titanium oxide and zinc in the corrosion resistance of our Ppy coating on aluminium.