@misc{HoffmannMikaloYfantisetal., author = {Hoffmann, Patrick and Mikalo, Ricardo Pablo and Yfantis, Alexandros D. and Batchelor, David R. and Appel, G{\"u}nter and Schmeißer, Dieter}, title = {A Spectro-Microscopic Approach for Thin Film Analysis Grain Boundaries in mc-Si and Sn/SnO2 Nano Particles}, series = {Microchimica Acta}, volume = {136}, journal = {Microchimica Acta}, number = {3-4}, issn = {1436-5073}, pages = {109 -- 113}, language = {en} } @article{Hoffmann, author = {Hoffmann, Patrick}, title = {Photoemission studies of very thin (<10nm) silicon oxynitride (SiOxNy) layers formed by PECVD}, abstract = {The "ITRS Roadmap" suggests the necessity of working out the processing methods allowing formation of ultrathin dielectric layers with higher values of the dielectric permittivity than for silicon dioxide. The silicon oxynitride layers (SiOxNy) seem to be the most natural compromise. But still none of high temperature methods used for its formation can be seriously considered as final solution for future ULSI-CMOS ICs production due to the inevitable formation of nitride monolayers just at the silicon-insulator interface. The main scope of this investigation is to check if this is true.}, language = {en} } @article{HoffmannMikaloSchmeisser, author = {Hoffmann, Patrick and Mikalo, Ricardo Pablo and Schmeißer, Dieter}, title = {Si(001) surface oxidation by N2O}, abstract = {Ultra-thin homogeneous oxynitride films are prepared on Si(001). The Si surface is cleaned in UHV by heating (flashing) and is exposed to different pressures of N2Oat altered temperatures. Thus oxynitride layers of different thickness and different properties are grown depending on the N2O pressure and the Si temperature. This isillustrated by a schematic diagram. The properties of the different oxynitride layers were studied by a combined photoemission electron microscopy (PEEM) andphotoelectron spectroscopy (PES) investigation using highly monochromatic synchrotron radiation. The amount of oxygen and nitrogen incorporated in the oxynitridelayers is determined from the PES measurements. The typical surface morphology for different preparation conditions is shown in PEEM images.}, language = {en} } @article{SchmeisserHoffmann, author = {Schmeißer, Dieter and Hoffmann, Patrick}, title = {Characterisation of the PrOx/Si(001) Interface by Photoelectron Spectroscopy}, language = {en} } @misc{HenkelSohalTorcheetal., author = {Henkel, Karsten and Sohal, Rakesh and Torche, Mohamed and Paloumpa, Ioanna and M{\"u}ller, Klaus and Hoffmann, Patrick and Schmeißer, Dieter}, title = {Grenzfl{\"a}chenoptimierung f{\"u}r funktionale D{\"u}nnschichtsysteme: Oxide und Polymere}, series = {Forum der Forschung}, volume = {9}, journal = {Forum der Forschung}, number = {18}, issn = {0947-6989}, pages = {49 -- 56}, language = {de} } @inproceedings{HoffmannMikaloSchmeisseretal., author = {Hoffmann, Patrick and Mikalo, Ricardo Pablo and Schmeißer, Dieter and Kittler, Martin}, title = {Spektro-Mikroskopie auf multikristallinem Silizium}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {Es werden spektro-mikroskopische Untersuchungen an multikristallinem Silizium (mc-Si) vorgestellt, einem aussichtsreichen Material f{\"u}r die Herstellung preiswerter Solarzellen. Dazu wird ein Photoemissions- Elektronenmikroskop (PEEM) ausgestattet mit einem zus{\"a}tzlichen Energieanalysator f{\"u}r Elektronen (µESCA) genutzt. Bei Verwendung eines Synchrotrons als Anregungsquelle ist es so m{\"o}glich, sowohl Absorbtions-Spektren (NEXAFS) als auch Photoelektronen-Spektren (PES) mit Ortsaufl{\"o}sung zu erhalten. Dabei wird gezeigt, dass das nat{\"u}rliche Oxid zur Untersuchung der morphologie-abh{\"a}ngigen Oberfl{\"a}chenpotentiale nicht entfernt werden muss. Des Weiteren wird die Verteilung von Ca- und Na-Ausscheidungen, die auf dem mc-Si gefunden wurden, durch ortsaufgel{\"o}stes NEXAFS bzw. PES dargestellt. F{\"u}r den Photoemissions-Prozess des mc-Si im PEEM wird ein Modell aufgestellt, welches Photoemission mit einer Quecksilberdampflampe (hνmax = 4,9 eV) erkl{\"a}rt.}, language = {de} } @inproceedings{MikaloAppelHoffmannetal., author = {Mikalo, Ricardo Pablo and Appel, G{\"u}nter and Hoffmann, Patrick and Schmeißer, Dieter}, title = {Conducting Polypyrrole doped with Phthalocyaninesulfonates - new materials for chemical sensors}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {Polypyrrole - a conducting polymer - is used as an active electrode of a quartz micro ballance and considered as a gate electrode in all-polymer field effect transistors used as chemical sensor. We use substituted phthalocyanines as dopants of polypyrrole as they offer the possibility to enhance the dopant concentration as well as to include functionalized groups. We studied these films by photoelectron spectroscopy, NEXAFS, PEEM, and TEM. These investigations revealed that the electronic structure as well as the morphology are highly dependent on the dopant's structure. We suggest a new charge transport model for 5-ring heterocycle conductive polymers. Whereas in the standard model only the carbon backbone is considered for the charge transport, we found by NEXAFS investigations that the heteroatom has a considerable high participation in the gap states, which are responsible for the charge transport. The dopants π-interactions force the nitrogen lone pair wave functions to contribute to the conducting polymer π-system. This is a novel approach concerning the application as chemical sensors since the reversible interaction of the analyte modifies the dopant and not the matrix.}, language = {en} } @inproceedings{HoffmannBoehmeSchmeisseretal., author = {Hoffmann, Patrick and B{\"o}hme, Oliver and Schmeißer, Dieter and Lloyd Spetz, Anita and M{\aa}rtenson, Per}, title = {Einfluß von Nanopartikeln auf die Funktion von Hochtemperatursensoren}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {Es werden Untersuchungen an als Hochtemperatur-Sensoren arbeitenden Schottky-Dioden mit dem Aufbau Metall-Oxidschicht-Siliziumkarbid vorgestellt. Dazu wurden Tiefenprofile mit XPS durch abwechselndes Abtragen durch Sputtern und Messen erstellt. Die Messungen erfolgten an thermisch unterschiedlich vorbehandelten Proben. Dabei konnten dipol-bedingte Verschiebungen der Bindungsenergie von Rumpfniveaus beobachtet werden. Das dazu notwendige Dipol-Moment wird durch das Entstehen von mit einer Oxidschicht {\"u}berzogenen Nanoteilchen erkl{\"a}rt. Die unterschiedlich ausgepr{\"a}gten Dipol-Verschiebungen auf den einzelnen Proben erlaubten eine Erkl{\"a}rung der thermischen Vorbehandlung, die bei Weglassen zu „frischen" und je nach Temperatur zu „aktivierten" oder „toten" Sensoren f{\"u}hrte.}, language = {de} } @inproceedings{MikaloAppelHoffmannetal., author = {Mikalo, Ricardo Pablo and Appel, G{\"u}nter and Hoffmann, Patrick and Schmeißer, Dieter}, title = {Leitf{\"a}higes Polypyrrol als Elektrodenmaterial: Wechselwirkungen mit Silber}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {Untersuchungen des metallischen Kontaktes von Silber auf tosylat- und phthalocyanindotiertem Polypyrrol wurden mittels XPS- und µ-NEXAFS vorgenommen. Es wurde festgestellt, daß Silber mit dem Polypyrrol keine Verbindung eingeht. Daraus kann geschlossen werden, daß sowohl das leitf{\"a}hige Polymer, als auch das Silber ihren Leitf{\"a}higkeitsmechanismus beibehalten. Es konnte gezeigt werden, daß bei steigender Silberbelegung die Intensit{\"a}t der Polaronenzust{\"a}nde des Polypyrrol in st{\"a}rkerem Maße abnimmt, als die Intensit{\"a}t der unbesetzten Zust{\"a}nde. Das l{\"a}ßt darauf schließen, daß Silber die Grenzfl{\"a}che stabilisiert.}, language = {de} } @inproceedings{HoffmannMikaloSchmeisser, author = {Hoffmann, Patrick and Mikalo, Ricardo Pablo and Schmeißer, Dieter}, title = {PEEM-Untersuchung an Spaltfl{\"a}chen von MoTe2-(0001)}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {Molybd{\"a}nditellurid (MoTe2) geh{\"o}rt zu den Schichtgitterverbindung und ist im allgemeinen durch den Herstellungsprozeß n-dotiert. Proben dieses MoTe2 wurden im Ultrahochvakuum gespalten und die so erhaltenen sauberen (0001)-Spaltfl{\"a}chen mit einem Photoemissions-Elektronenmikroskop (PEEM) untersucht. Diese Untersuchung erbrachte nebeneinander auf den Proben- oberfl{\"a}chen liegende stark kontrastierte helle und dunkle Bereiche. Da das PEEM Austrittsarbeitsunterschiede als Kontrast darstellt, k{\"o}nnen diese hellen und dunklen Bereiche auf lokale Unterschiede in der Austrittsarbeit zur{\"u}ckgef{\"u}hrt werden. Weiterhin wird {\"u}ber den Versuch berichtet, eine Zuordnung zwischen dem Kontrast und dem Unterschied in der Austrittsarbeit mit Hilfe eines Elektronenenergie-Analysators (micro-ESCA) zu treffen.}, language = {de} } @inproceedings{BatchelorHoffmannSchmeisseretal., author = {Batchelor, David R. and Hoffmann, Patrick and Schmeißer, Dieter and Hulea, Iulian and Brinza, Monica}, title = {The Al-Fe interface of friction-welded joints}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {The interface region of friction-welded joints Al-Fe samples is investigated by scanning Auger Spectroscopy, Electron Probe Micro-analysis (EPMA), X-ray Photoelectron spectroscopy, and Photoemission Electron Microscopy, performed at the synchrotron light source (BESSY). We investigated polished samples cut to obtain a cross-section of the Al-Fe joints. At the Al-Fe interface there is a small number of Fe teeth protuding into the adjacent Al-matrix. Beside this mechanical interlock mechanism we identify an Fe-Al alloy which is formed in an almost homogeneous interface layer of approximately 80 micron thickness. We determine the valence band spectra within that layer and notice that the alloying formation is limited to the interface region. In addition, the profile of both, the Fe and O distribution within the Al next to that interface is determined. A model of the friction-welding mechanism is derived and discussed in terms of the ability of achieving low temperature Fe-Al joints.}, language = {en} } @article{BieniekBeckJakubowskietal., author = {Bieniek, Tomasz and Beck, Romuald B. and Jakubowski, Andrzej and Konarski, Piotr and Cwil, M. and Hoffmann, Patrick and Schmeißer, Dieter}, title = {Application of r.f. plasma ultrashallow nitrogen ion implantation for pedestal oxynitride layer formation}, language = {en} } @inproceedings{MikaloHoffmannSchmeisseretal., author = {Mikalo, Ricardo Pablo and Hoffmann, Patrick and Schmeißer, Dieter and Lloyd Spetz, Anita and Lundstr{\"o}m, Ingemar and Wawra, Herbert and Pressel, Klaus and Ourmazd, Abbas}, title = {Depth profiling using synchrotron radiation with high energetic resolution as demonstrated for Si-, SiC-, SiGe-, and SiGeC-samples}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {Photoelectron spectroscopy utilizing synchrotron radiation of high energetic resolution (more than E/ΔE=3000) was used to record the Si2p emission signal of Si, SiC, SiGe, and SiGeC samples. The spectra exhibit signals of the elemental silicon as well as of fully oxidised silicon. Upon variing the photon energy, and therefore the escape depth of the photoelectrons, we find an oxidic silicon signal which is only half oxidized. This half oxidized silicon is located to be at the interface of the bulk material with the oxide. We determine the thickness of the surface oxide from the total ratio of oxidic and elemental silicon. We find differences between the interface and bulk oxides regarding their elemental composition. The line width of the elemental Si2p-signal exhibits a broadening of approximately 200meV while variing the photoelectron escape depth. This behaviour is interpreted as caused by surface stress.}, language = {en} } @inproceedings{HoffmannSchmeisser, author = {Hoffmann, Patrick and Schmeißer, Dieter}, title = {Depth Profiling of Ultrathin Oxynitride Layers Using Synchrotron Radiation}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {To determine the depth structure of samples various destructive (SIMS, depth profiling with sputtering and AES or XPS) and non-destructive techniques (RBS - Rutherford-Back-Scattering) are available. But all methods are less suitable for investigating especially ultrathin (<5nm) layers: While the destructive techniques suffer from Ion-mixing the RBS can not deliver chemical information. Due to the depth-dependent attenuation of photo-electrons XPS also contains depth information. As XPS gives only a sum signal across the layer one needs to modify the Inelastic Mean Free Path (IMFP) of the photo-electrons to vary the depth information in the photo-electron spectra. This can be done by changing the kinetic energy with the use of different excitation energies delivered from a Synchrotron. Using this method we were able to investigate the chemical depth structure of silicon oxynitride layers. The layers were grown on Si(111) by a N2O-treatment. The depth profile of that layer shows a silicon nitride layer forming the interface between the silicon substrate and the oxynitride.}, language = {en} } @inproceedings{SchmeisserWehnerHoffmannetal., author = {Schmeißer, Dieter and Wehner, Stefan and Hoffmann, Patrick and Brand, Helmut R. and K{\"u}ppers, J{\"u}rgen}, title = {Influence of the Substrate on the Pattern Formation of a Surface Reaction}, series = {Nonequilibrium statistical mechanics and nonlinear physics, XV Conference on Nonequilibrium Statistical Mechanics and Nonlinear Physics, Mar del Plata, Argentina, 4 - 8 December 2006}, booktitle = {Nonequilibrium statistical mechanics and nonlinear physics, XV Conference on Nonequilibrium Statistical Mechanics and Nonlinear Physics, Mar del Plata, Argentina, 4 - 8 December 2006}, editor = {Descalzi, Orazio}, publisher = {AIP Publishing}, address = {Melville, New York}, isbn = {978-0-7354-0421-2}, pages = {121 -- 126}, language = {en} } @inproceedings{HoffmannMikaloSchmeisser, author = {Hoffmann, Patrick and Mikalo, Ricardo Pablo and Schmeißer, Dieter}, title = {Si(001) surface oxidation}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {A Si(001) surface is cleaned in UHV by heating (flashing) and is exposed to different pressures of N2O at altered temperatures. Oxynitride layers of different thicknesses and different properties are grown depending on the N2O-pressure and the Si- temperature. This is illustrated by a schematic diagram. The properties of the different Oxynitride layers were studied by a combined PEEM- and PES-investigation using highly monochromatised synchrotron radiation. The amount of Oxygen and Nitrogen incorporated in the Oxynitride layers is determined from the PES measurements. The typical surface morphology for different preparation conditions is shown in PEEM images. A model based on differently established dipole layers in the Oxynitride layers is proposed. This model is capable of interpreting the features appearing in the PE-spectra. This model can also be applied to the interface of Si/SiO2.}, language = {en} } @article{BeckHoffmannSchmeisseretal., author = {Beck, Romuald B. and Hoffmann, Patrick and Schmeißer, Dieter and Bieniek, Tomasz and Jakubowski, Andrzej}, title = {Composition and Electrical Properties of Ultra-Thin SiOxNy Layers Formed by rf Plasma Nitrogen Implantation/Plasma Oxidation Processes}, language = {en} } @inproceedings{HoffmannGoryachkoSchmeisser, author = {Hoffmann, Patrick and Goryachko, Andriy and Schmeißer, Dieter}, title = {Growth of oxynitrides on Si-rich 4H-SiC(0001) surfaces}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {Oxynitride layers are grown on 4H-SiC(0001) by a thermal treatment in N2O. The nitrogen content is controlled by varying the growth conditions (N2O pressure and substrate temperature) and the nitrogen incorporation is found to be stronger for higher substrate temperatures and lower N2O pressures. Excess carbon is generated due to SiC decomposition under such growth conditions (high temperature and low N2O pressure) which leads to unwanted high interface state density and has to be avoided. Our approach is to prepare a Si-rich or even Si-covered SiC surface by Si evaporation. Upon oxidation in N2O the additional silicon is expected to compensate the loss of silicon from the SiC while preparation. The Si-rich SiC surface as well as the grown layers were investigated by photoelectron spectroscopy (XPS) for chemical analysis and by AFM/STM for analysis of the surface morphology. Concerning the chemical analysis we focus on the total nitrogen content, on the amount of silicon nitride Si3N4 and of silicon oxynitride SiOxNy, and on the existence of sub-oxides which build the interface between SiC and the oxynitride layers.}, language = {en} } @inproceedings{HoffmannSchmeisser, author = {Hoffmann, Patrick and Schmeißer, Dieter}, title = {Growth of oxynitrides on Si-rich 4H-SiC(0001) surfaces}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {It will be reported on the growth of oxynitride thin layers (≤10nm) on (0001)-oriented 4H-SiC surfaces. The oxynitride layers were grown by a thermal treatment of the samples in low pressure N2O ambient. By varying the growth conditions (N2O pressure, sample temperature, growth time) different layers were made. The grown layers were investigated by photoelectron spectroscopy (XPS) for chemical analysis and by AFM/STM for analysis of the surface morphology. Concerning the chemical analysis it will be discussed the general nitrogen content of the samples, the composition of the films (e.g. content of silicon nitride Si3N4 and silicon oxynitride SiOxNy) and the sub-oxides which build the interface between SiC and the oxynitride layers. Concerning the surface morphology mainly the roughness will be discussed. The so obtained results for oxynitride thin films on 4H-SiC will be compared to similarly prepared oxynitride layers on Si(111) investigated in the past.}, language = {en} } @article{MroczynskiHoffmannSchmeisser, author = {Mroczynski, Robert and Hoffmann, Patrick and Schmeißer, Dieter}, title = {The Influence of Annealing (900 Grad C) of Ultra-Thin PECVD Silicon Oxynitride Layers}, language = {en} }