TY - JOUR A1 - Sokolowski-Tinten, Klaus A1 - Horn-von Hoegen, Michael A1 - von der Linde, D. A1 - Cavalleri, Andrea A1 - Siders, C. W. A1 - Brown, F. L. H. A1 - Leitner, D. M. A1 - Tóth, Csaba A1 - Squier, Jeff A. A1 - Barty, C. P. J. A1 - Wilson, K. R. A1 - Kammler, Martin T1 - Transient lattice dynamics in fs-laser-excited semiconductors probed by ultrafast X-ray diffraction JF - Journal de Physique IV N2 - A study of lattice dynamics in fs-laser-excited crystalline bulk Ge and Ge/Si-heterostructures, using time-resolved x-ray diffraction, was presented. Fast energy transport deep into the bulk of the material, coherent acoustic phonon dynamics, lattice anharmonicity, and vibrational transport across a buried interfaces were observed. Graphs showing time-dependent shifts of the centroid of the measured rocking curves in the Ge-overlayer and in the Si-substrate for different fluences, were presented. Y1 - 2001 U6 - https://doi.org/10.1051/jp4:2001290 VL - 11 IS - Pr2 SP - 473 EP - 477 PB - EDP ER - TY - JOUR A1 - Sokolowski-Tinten, Klaus A1 - Cavalleri, Andrea A1 - Siders, C. W. A1 - Brown, F. L. H. A1 - Leitner, D. M. A1 - Tóth, Csaba A1 - Kammler, Martin A1 - Horn-von Hoegen, Michael A1 - von der Linde, D. A1 - Squier, Jeff A. A1 - Barty, C. P. J. A1 - Wilson, K. R. T1 - Time-resolved x-ray diffraction study of ultrafast acoustic phonon dynamics in Ge/Si-heterostructures JF - Chemical Physics N2 - Using time-resolved x-ray diffraction the ultafast strain dynamics in fs-laserexcited Ge/Si-heterostructures has been studied. A fluence dependent, anharmonic damping of the impulsively generated acoustic phonons and vibrational transport across the buried Ge/Si-interface are observed. Y1 - 2001 U6 - https://doi.org/10.1007/978-3-642-56546-5_81 VL - 66 SP - 281 EP - 283 PB - Springer ER - TY - CHAP A1 - Sokolowski-Tinten, Klaus A1 - Blome, Christian A1 - Dietrich, Clemens A1 - Blums, Juris A1 - Horn-von Hoegen, Michael A1 - von der Linde, D. A1 - Cavalleri, Andrea A1 - Squier, Jeff A. A1 - Kammler, Martin T1 - Structural dynamics in laser-excited solids investigated with femtosecond x-ray diffraction T2 - 2002 Summaries of Papers Presented at the Quantum Electronics and Laser Science Conference, 19-24 May 2002, Long Beach, CA, USA N2 - Summary form only given. Ultrashort x-ray pulses offer a unique combination of atomic-scale spatial and temporal resolution, which permits direct measurements of structural transients on an ultrafast time scale. Using time-resolved X-ray diffraction with femtosecond, multi-keV X-ray pulses we have studied transient lattice dynamics in optically excited semiconductors. Y1 - 2002 U6 - https://doi.org/10.1109/QELS.2002.1031182 SP - 115 EP - 116 PB - IEEE ER - TY - JOUR A1 - Sokolowski-Tinten, Klaus A1 - Blome, Christian A1 - Dietrich, Clemens A1 - Tarasevitch, A. A1 - Horn-von Hoegen, Michael A1 - von der Linde, D. A1 - Cavalleri, Andrea A1 - Squier, Jeff A. A1 - Kammler, Martin T1 - Femtosecond x-ray measurement of ultrafast melting and large acoustic transients JF - Physical review letters N2 - Time-resolved x-ray diffraction with ultrashort ( approximately 300 fs), multi-keV x-ray pulses has been used to study the femtosecond laser-induced solid-to-liquid phase transition in a thin crystalline layer of germanium. Nonthermal melting is observed to take place within 300-500 fs. Following ultrafast melting we observe strong acoustic perturbations evolving on a picosecond time scale. Y1 - 2001 U6 - https://doi.org/10.1103/PhysRevLett.87.225701 VL - 87 PB - APS ER - TY - JOUR A1 - Sokolowski-Tinten, Klaus A1 - Blome, Christian A1 - Dietrich, Clemens A1 - Tarasevitch, A. A1 - Horn-von Hoegen, Michael A1 - von der Linde, D. A1 - Cavalleri, Andrea A1 - Squier, Jeff A. A1 - Kammler, Martin T1 - Femtosecond time-resolved X-ray diffraction study of ultrafast structural dynamics in laser-excited solids JF - International Conference on Ultrafast Phenomena, 12 May 2002, Vancouver Canada N2 - Time-resolved x-ray diffraction with sub-300 fs, multi-keV x-ray pulses was used to study ultrafast lattice dynamics in laser-irradiated germanium and bismuth. In bismuth strong excitation of optical phonons is observed prior to disordering of the material. Y1 - 2002 U6 - https://doi.org/10.1007/978-3-642-59319-2_10 VL - 71 SP - 36 EP - 38 PB - Optica Publishing Grou ER - TY - INPR A1 - Tringides, Michael C. A1 - Conrad, E. H. A1 - Menzel, Andreas A1 - Voss, Neil R. A1 - Kammler, Martin A1 - Horn-von Hoegen, Michael T1 - Dynamics of atomic steps on Si(001) studied by temporal LEED spectroscopy [Poster] N2 - While surface kinetics measurements for single atom diffusion have proliferated, little work exists attempting to measure surface dynamics under equilibrium conditions. We will present our recent work on developing Temporal LEED Spectroscopy (TLS) as a dynamic probe of surfaces capable of kinetics measurements at both high temperatures and surface coverages. By tuning the diffraction to specific structural entities such as steps, islands, etc., and monitoring the diffracted signal as a function of time, dynamics information about these structures can be obtained. As an example we will present TLS results for the dynamics of step fluctuations on Si(001) [1]. We have measured activation energies and identified step-edge diffusion as the rate limiting process for 950K < T < 1130K. Although this result is in apparent disagreement with earlier work, a careful analysis, considering crossover temperatures between different microscopic processes, can reconcile the differences. 1. M. Kammler, et al., Phys. Rev. B (in press). Y1 - 2002 UR - https://www.researchgate.net/publication/252546721_Dynamics_of_atomic_steps_on_Si001_studied_by_temporal_LEED_spectroscopy_poster ER - TY - JOUR A1 - Horn-von Hoegen, Michael A1 - Meyer zu Heringdorf, Frank-Joachim A1 - Kammler, Martin A1 - Schaeffer, C. A1 - Reinking, D. A1 - Hofmann, K. R. T1 - Bi surfactant mediated epitaxy of Ge on Si(111) JF - Thin Solid Films N2 - We have tested Bi for the surfactant mediated epitaxy of Ge on Si(111). Islanding of Ge is prevented and a 2D layer growth of smooth and continuous Ge films is observed. The lattice mismatch is accommodated by a periodic array of dislocations confined to the Si/Ge interface. The large covalent radius of Bi reduces the binding energy, allowing Very efficient segregation and low doping levels even at low growth temperatures. Unfortunately, this results also in a high Bi desorption flux limiting the possible growth temperatures below 600 degrees C. Consequently the Ge films show a high defect density in the order of 10(8) cm(-2) for stacking faults and 10(9) cm(-2) for dislocations which limit electron Hall mobility to values below 700 cm(2)/V s at room temperature. KW - Hall mobility KW - Heteroepitaxial growth KW - Surfactants KW - Doping KW - Molecular beam epitaxy KW - Silicon KW - Germanium KW - Bismuth KW - Low energy electron diffraction KW - Scanning electron microscopy Y1 - 1999 U6 - https://doi.org/10.1016/S0040-6090(98)01659-9 VL - 343-344 SP - 579 EP - 582 PB - Elsevier ER - TY - JOUR A1 - Cavalleri, Andrea A1 - Siders, C. W. A1 - Brown, F. L. H. A1 - Leitner, D. M. A1 - Tóth, Csaba A1 - Squier, Jeff A. A1 - Barty, C. P. J. A1 - Wilson, K. R. A1 - Sokolowski-Tinten, Klaus A1 - Horn-von Hoegen, Michael A1 - von der Linde, D. A1 - Kammler, Martin T1 - Anharmonic lattice dynamics in germanium measured with ultrafast x-ray diffraction JF - Physical review letters N2 - Damping of impulsively generated coherent acoustic oscillations in a femtosecond laser-heated thin germanium film is measured as a function of fluence by means of ultrafast x-ray diffraction. By simultaneously measuring picosecond strain dynamics in the film and in the unexcited silicon substrate, we separate anharmonic damping from acoustic transmission through the buried interface. The measured damping rate and its dependence on the calculated temperature of the thermal bath is consistent with estimated four-body, elastic dephasing times (T2) for 7-GHz longitudinal acoustic phonons in germanium. Y1 - 2000 U6 - https://doi.org/10.1103/PhysRevLett.85.586 VL - 85 IS - 3 SP - 586 EP - 589 PB - APS ER - TY - JOUR A1 - Sokolowski-Tinten, Klaus A1 - Horn-von Hoegen, Michael A1 - von der Linde, D. A1 - Cavalleri, Andrea A1 - Siders, C. W. A1 - Brown, F. L. H. A1 - Tóth, Csaba A1 - Squier, Jeff A. A1 - Barty, C. P. J. A1 - Wilson, K. R. A1 - Kammler, Martin T1 - Time-resolved x-ray diffraction study of ultrafast acoustic phonon dynamics in Ge/Si-heterostructures JF - International Conference on Ultrafast Phenomena , 9 July 2000, Charleston N2 - Using time-resolved x-ray diffraction the ultafast strain dynamics in fs-laserexcited Ge/Si-heterostructures has been studied. A fluence dependent, anharmonic damping of the impulsively generated acoustic phonons and vibrational transport across the buried Ge/Si-interface are observed. KW - Acoustic Phonon KW - Acoustic Transmission KW - Carrier Diffusion KW - Homogenous Expansion KW - Lattice Anharmonicity Y1 - 2000 UR - https://opg.optica.org/abstract.cfm?uri=UP-2000-MF43 PB - Optica ER - TY - JOUR A1 - Siders, C. W. A1 - Cavalleri, Andrea A1 - Sokolowski-Tinten, Klaus A1 - Tóth, Csaba A1 - Guo, T. A1 - Kammler, Martin A1 - Horn-von Hoegen, Michael A1 - Wilson, K. R. A1 - von der Linde, D. A1 - Barty, C. P. J. T1 - Detection of nonthermal melting by ultrafast X-ray diffraction JF - Science N2 - Using ultrafast, time-resolved, 1.54 angstrom x-ray diffraction, thermal and ultrafast nonthermal melting of germanium, involving passage through nonequilibrium extreme states of matter, was observed. Such ultrafast, optical-pump, x-ray diffraction probe measurements provide a way to study many other transient processes in physics, chemistry, and biology, including direct observation of the atomic motion by which many solid-state processes and chemical and biochemical reactions take place. Y1 - 1999 U6 - https://doi.org/10.1126/science.286.5443.1340 VL - 286 IS - 5443 SP - 1340 EP - 1342 ER - TY - JOUR A1 - Reinking, D. A1 - Kammler, Martin A1 - Hoffmann, N. A1 - Horn-von Hoegen, Michael A1 - Hofmann, K. R. T1 - Fabrication of high-mobility Ge p-channel MOSFETs on Si substrates JF - Electronics Letters N2 - The first fabrication of Ge p-channel MOSFETs (p-MOSFETs) on Si substrates is reported. A CMOS compatible process based on relaxed Ge layers grown on Si(111) substrates by surfactant mediated epitaxy (SME) was used. The non-optimised low temperature process yielded normally-off Ge p-MOSFETs with record channel drift mobilities of 430 cm2/Vs KW - silicon KW - CMOS integrated circuits KW - germanium KW - carrier mobility KW - epitaxial growth KW - integrated circuit technology KW - elemental semiconductors KW - semiconductor growth KW - MOSFET KW - Insulated gate field effect transistors KW - Thin film growth and epitaxy Y1 - 1999 U6 - https://doi.org/10.1049/el:19990349 VL - 35 IS - 6 SP - 503 EP - 504 PB - IET ER - TY - JOUR A1 - Siders, C. W. A1 - Cavalleri, Andrea A1 - Sokolowski-Tinten, Klaus A1 - Tóth, Csaba A1 - Guo, T. A1 - Kammler, Martin A1 - Horn-von Hoegen, Michael A1 - Wilson, K. R. A1 - von der Linde, D. A1 - Barty, C. P. J. T1 - Direct Observation of Ultrafast Non-thermal Melting by Ultrafast X-ray Diffraction JF - Ultrafast Phenomena XII N2 - Ultrafast nonthermal melting of femtosecond laser-irradiated germanium was observed directly for the first time using sub-picosecond, 1.54-angstrom x-ray diffraction. Such measurements allow the study of transient atomic motion fundamental to many processes in physics, chemistry, and biology. Y1 - 2000 U6 - https://doi.org/10.1007/978-3-642-56546-5_80 VL - 66 SP - 276 EP - 280 PB - Springer ER - TY - CHAP A1 - Sokolowski-Tinten, Klaus A1 - von der Linde, D. A1 - Siders, C. W. A1 - Cavalleri, Andrea A1 - Tóth, Csaba A1 - Guo, T. A1 - Wilson, K. R. A1 - Barty, C. P. J. A1 - Kammler, Martin A1 - Horn-von Hoegen, Michael T1 - Lattice dynamics of femtosecond laser-excited semiconductors probed by ultrafast x-ray diffraction T2 - Applications of High Field and Short Wavelength Sources VIII N2 - The present knowledge of the atomic structure of matter is to a large extent due to x-ray spectroscopies. Y1 - 1999 U6 - https://doi.org/10.1364/HFSW.1999.PD3 PB - Optica ER - TY - JOUR A1 - Schmidt, Thomas A1 - Kröger, Roland A1 - Flege, Jan Ingo A1 - Horn-von Hoegen, Michael A1 - Clausen, T. A1 - Falta, J. A1 - Janzen, Andreas A1 - Zahl, P. A1 - Kury, P. A1 - Kammler, Martin T1 - Less strain energy despite fewer misfit dislocations: the impact of ordering JF - Physical review letters N2 - The average strain state of Ge films grown on Si(111) by surfactant mediated epitaxy has been compared to the ordering of the interfacial misfit dislocation network. Surprisingly, a smaller degree of average lattice relaxation was found in films grown at higher temperature. On the other hand, these films exhibit a better ordered dislocation network. This effect energetically compensates the higher strain at higher growth temperature, leading to the conclusion that, apart from the formation of misfit dislocations, their ordering represents an important channel for lattice-strain energy relaxation. Y1 - 2006 U6 - https://doi.org/10.1103/PhysRevLett.96.066101 VL - 96 IS - 6 PB - APS ER - TY - JOUR A1 - Hull, Robert A1 - Gray, J. L. A1 - Kammler, Martin A1 - Vandervelde, T. A1 - Kobayashi, Takeshi A1 - Kumar, P. A1 - Pernell, T. A1 - Bean, J. C. A1 - Floro, J. A. A1 - Ross, Frances M. T1 - Precision placement of heteroepitaxial semiconductor quantum dots JF - Materials Science and Engineering: B N2 - We describe two new approaches to the patterning of Si(1 0 0) surfaces for controlled nucleation of heteroepitaxial Ge semiconductor clusters. In the first method, a Ga ' -focused ion beam in situ to the growth chamber is used to create local regions of enhanced Ga ' concentration and surface topography. It is shown that at low ion doses (Â/10 14 cm (2), implanted Ga causes local nucleation of Ge clusters upon the implanted region. At higher doses (]/10 15 cm (2), a complex surface topography localizes nucleation of Ge clusters. This approach can be used to seed complex patterns of Ge clusters with diameters of tens of nanometers and positional accuracy of sub-100 nm. The second method employs self-assembly of complex strain-stabilized ''quantum quadruplet'' and ''quantum fortress'' structures, whereby cooperative island nucleation around shallow strain-relieving pits is identified during Ge x Si 1(x /Si(1 0 0) heteroepitaxy. These configurations are kinetically limited structures that exist over a range of compositions, growth temperatures, and growth rates, but which are destabilized by strain relaxation (e.g. by the introduction of misfit dislocations) and by growth conditions which provide high adatom surface mobilities. Both methods have broad potential application to nanoelectronic device architectures. 2003 Elsevier Science B.V. All rights reserved. KW - Strained layer epitaxy KW - Strain relaxation KW - Quantum fortress KW - Molecular beam epitaxy KW - Controlled nucleation Y1 - 2003 U6 - https://doi.org/10.1016/S0921-5107(02)00680-3 VL - 101 IS - 1-3 SP - 1 EP - 8 PB - Elsevier ER - TY - JOUR A1 - Hanisch-Blicharski, Anja A1 - Janzen, Andreas A1 - Krenzer, Boris A1 - Wall, S. A1 - Klasing, Friedrich A1 - Kalus, Annika A1 - Frigge, Tim A1 - Kammler, Martin A1 - Horn-von Hoegen, Michael T1 - Ultra-fast electron diffraction at surfaces: from nanoscale heat transport to driven phase transitions JF - Ultramicroscopy N2 - Many fundamental processes of structural changes at surfaces occur on a pico- or femtosecond time scale. In order to study such ultra-fast processes, we have combined modern surface science techniques with fs-laser pulses in a pump-probe scheme. Reflection high energy electron diffraction (RHEED) with grazing incident electrons ensures surface sensitivity for the probing electron pulses. Utilizing the Debye-Waller effect, we studied the cooling of vibrational excitations in monolayer adsorbate systems or the nanoscale heat transport from an ultra-thin film through a hetero-interface on the lower ps-time scale. The relaxation dynamics of a driven phase transition far away from thermal equilibrium is demonstrated with the In-induced (8×2) reconstruction on Si(111). This surface exhibits a Peierls-like phase transition at 100K from a (8×2) ground state to (4×1) excited state. Upon excitation by a fs-laser pulse, this structural phase transition is driven into an excited (4×1) state at a sample temperature of 20K. Relaxation into the (8×2) ground state occurs after more than 150 ps. Y1 - 2013 U6 - https://doi.org/10.1016/j.ultramic.2012.07.017 VL - 127 SP - 2 EP - 8 PB - Elsevier ER - TY - JOUR A1 - Menzel, Andreas A1 - Kammler, Martin A1 - Conrad, E. H. A1 - Yeh, V. A1 - Hupalo, Myron A1 - Tringides, Michael C. T1 - Kinetics measurements of Pb island growth on Si(111) JF - Physical Review B N2 - We present the results of kinetics experiments on quantum-size-effects (QSE) Pb islands formed on Si(111). We have looked at the evolution of seven-layer Pb islands from five-layer Pb islands due to the transport of Pb atoms from the interisland region, overcoming a barrier at the island edges, and moving to the island tops. By analyzing low-energy electron-diffraction and scanning-tunneling microscopy data, we have estimated the barrier for layer formation in this system to be ∼0.32eV. This energy is much larger than that expected from QSE electronic contributions alone. Y1 - 2003 U6 - https://doi.org/10.1103/PhysRevB.67.165314 VL - 67 IS - 16 PB - American Physical Society ER - TY - CHAP A1 - Kammler, Martin A1 - Horn- von Hoegen, Michael A1 - Voss, N. A1 - Tringides, Michael C. A1 - Menzel, Andreas A1 - Conrad, E. H. T1 - Surface Dynamics of Stepped Si(001) Studied by Temporal Leed Spectroscopy T2 - Collective Diffusion on Surfaces: Correlation Effects and Adatom Interactions (NATO Science Series II: Mathematics, Physics and Chemistry N2 - We present the first demonstration of Temporal LEED Spectroscopy’s ability to measure surface dynamics as shown by a study of step dynamics on vicinal Si(001). While we measure activation energies consistent with other work, the observed microscopic mechanism driving the fluctuations is inconsistent with previous claims. We exclude evaporation/condensation of atoms from the steps as the rate limiting kinetics in the temperature range of this experiment. Possible reasons for these differences are discussed. Y1 - 2001 U6 - https://doi.org/10.1007/978-94-010-0816-7_3 VL - 29 SP - 23 EP - 32 PB - Springer ER - TY - JOUR A1 - Streubühr, C. A1 - Kalus, Annika A1 - Zhou, Ping A1 - Ligges, Manuel A1 - Hanisch-Blicharski, Anja A1 - Kammler, Martin A1 - Bovensiepen, U. A1 - Horn-von Hoegen, Michael A1 - von der Linde, D. T1 - Comparing ultrafast surface and bulk heating using time-resolved electron diffraction JF - Applied Physics Letters N2 - From measurements of the transient Debye-Waller effect in Bismuth, we determine the buildup time of the random atomic motion resulting from the electronic relaxation after short pulse laser excitation. The surface sensitive reflection high energy electron diffraction and transmission electron diffraction yield a time constant of about 12 ps and 3 ps, respectively. The different energy transfer rates indicate relatively weak coupling between bulk and surface vibrational modes. (C) 2014 AIP Publishing LLC. Y1 - 2014 U6 - https://doi.org/10.1063/1.4872055 VL - 104 SP - 1 EP - 3 PB - American Institute of Physics ER - TY - CHAP A1 - Shymanovich, Uladzimir A1 - Nicoul, Matthieu A1 - Lu, Wei A1 - Tarasevitch, A. A1 - Kammler, Martin A1 - Horn-von Hoegen, Michael A1 - von der Linde, D. A1 - Sokolowski-Tinten, Klaus A1 - Phipps, Claude T1 - Coherent acoustic and optical phonons in laser-excited solids studied by ultrafast time-resolved X-ray diffraction T2 - AIP Conference Proceedings N2 - We apply ultrafast time‐resolved X‐ray diffraction to directly study coherent acoustic and optical phonons in laser‐excited materials. In Au the ps acoustic response has been investigated with the particular goal to clarify the interplay of electronic and thermal pressure contributions. In Bi the extreme softening of the coherently excited A 1 g optical phonon presents strong indication that upon intense laser‐excitation the Peierls‐transition which determines the equilibrium structure of Bi can be reversed. In FeRh we studied the lattice response after a fast laser‐induced anti‐ferromagnetic to ferromagnetic phase transition. Y1 - 2010 U6 - https://doi.org/10.1063/1.3507146 IS - 1 SP - 558 EP - 566 PB - AIP ER - TY - JOUR A1 - Payer, Thomas A1 - Klein, C. A1 - Acet, M. A1 - Ney, V. A1 - Kammler, Martin A1 - Meyer zu Heringdorf, Frank-Joachim A1 - Horn-von Hoegen, Michael T1 - High-quality epitaxial Bi(111) films on Si(111) by isochronal annealing JF - Thin Solid Films N2 - Bi(111) films grown on Si(111) at room temperature show a significantly higher roughness compared to Bi films grown on Si(100) utilizing a kinetic pathway based on a low-temperature process. Isochronal annealing steps of 3 min duration each with temperatures up to 200 °C cause a relaxation of the Bi films' lattice parameter toward the Bi bulk value and yield an atomically flat Bi surface. Driving force for the relaxation and surface reordering is the magic mismatch of 11 Bi atoms to 13 Si atoms that emerges at annealing temperatures above 150 °C and reduces the remaining strain to less than 0.2%. KW - Epitaxy KW - Strain KW - Annealing KW - Bismuth KW - Silicon Y1 - 2012 U6 - https://doi.org/10.1016/j.tsf.2012.06.004 VL - 520 IS - 23 SP - 6905 EP - 6908 PB - Elsevier ER - TY - CHAP A1 - Zhou, Ping A1 - Streubühr, C. A1 - Kalus, Annika A1 - Frigge, Tim A1 - Wall, S. A1 - Hanisch-Blicharski, Anja A1 - Kammler, Martin A1 - Ligges, Manuel A1 - Bovensiepen, U. A1 - von der Linde, D. A1 - Horn-von Hoegen, Michael T1 - Ultrafast time resolved reflection high energy electron diffraction with tilted pump pulse fronts T2 - EPJ Web of Conferences - XVIIIth International Conference on Ultrafast Phenomena N2 - We present time-resolved RHEED from a laser excited Pb(111) surface using a pulse front tilter for the compensation of the velocity mismatch of electrons and light. The laser pulses with tilted fronts were characterized by a spatially resolving cross correlator. The response of the surface upon excitation was observed to be less than 2 ps. Y1 - 2013 U6 - https://doi.org/10.1051/epjconf/20134110016 VL - 41 PB - EPJ ER - TY - CHAP A1 - Lu, Wei A1 - Nicoul, Matthieu A1 - Shymanovich, Uladzimir A1 - Tarasevitch, A. A1 - Kammler, Martin A1 - Horn-von Hoegen, Michael A1 - von der Linde, D. A1 - Sokolowski-Tinten, Klaus T1 - Transient reversal of a Peierls-transition: Extreme phonon softening in laser-excited Bismuth T2 - International Conference on Ultrafast Phenomena, Snowmass N2 - Laser-excited coherent optical phonons in Bismuth were investigated using time-resolved X-ray diffraction. The observed extreme softening of the excited A1g-mode presents strong indication that the Peierls-distortion defining the equilibrium structure of Bismuth is transiently reversed. Y1 - 2010 U6 - https://doi.org/10.1364/UP.2010.ME41 IS - ME41 PB - Optica Publishing Group ER - TY - JOUR A1 - Portavoce, A. A1 - Kammler, Martin A1 - Hull, Robert A1 - Reuter, Mark C. A1 - Copel, M. A1 - Ross, Frances M. T1 - Growth of nanostructures by locally modified surface reactivity JF - Materials Science in Semiconductor Processing N2 - The chemical vapor deposition (CVD) of Si and Ge on Si(0 0 1) substrates covered by 1 monolayer of Ga has been studied. Ga modifies surface reactivity and surface atom mobility. We show that islanding occurs during Ga-mediated CVD even in the absence of strain, allowing for the formation of islands without a wetting layer or with a thinner wetting layer. The morphology of the grown layer is highly dependent on kinetic parameters, i.e. growth temperature and growth pressure, that control Si and Ge deposition and Ga desorption. Si Ga-mediated CVD promotes the formation of self-assembled epitaxial Si islands exhibiting {1 1 3} facets. Ge islands grown by Ga-mediated CVD present reduced lateral sizes and an increased surface density compared to non Ga-mediated CVD. The growth morphology (particularly island size and density) can be understood by considering a qualitative model in which atoms are deposited only on sites whose dangling bonds are not passivated by Ga. We suggest that modification of surface reactivity during surfactant-mediated CVD can thus provide a new degree of freedom for quantum dot fabrication. KW - UHV TEM KW - UHV CVD KW - Epitaxial growth KW - Si KW - Ge KW - Surfactant Ga Y1 - 2009 U6 - https://doi.org/10.1016/j.mssp.2009.07.001 VL - 12 IS - 1-2 SP - 25 EP - 30 PB - Elsevier ER - TY - JOUR A1 - Portavoce, A. A1 - Kammler, Martin A1 - Hull, Robert A1 - Reuter, Mark C. A1 - Ross, Frances M. T1 - Mechanism of the nanoscale localization of Ge quantum dot nucleation on focused ion beam templated Si(001) surfaces JF - Nanotechnology N2 - We investigate the fundamental mechanism by which self-assembled Ge islands can be nucleated at specific sites on Si(001) using ultra-low-dose focused ion beam (FIB) pre-patterning. Island nucleation is controlled by a nanotopography that forms after the implantation of Ga ions during subsequent thermal annealing of the substrate. This nanotopography evolves during the annealing stage, changing from a nanoscale annular depression associated with each focused ion beam spot to a nanoscale pit, and eventually disappearing (planarizing). The correspondence of Ge quantum dot nucleation sites to the focused ion beam features requires a growth surface upon which the nanotopography is preserved. A further key observation is that the Ge wetting layer thickness is reduced in patterned regions, allowing the formation of islands on the templated regions without nucleation elsewhere. These results provide routes to the greatly enhanced design and control of quantum dot distributions and dimensions. Y1 - 2006 U6 - https://doi.org/10.1088/0957-4484/17/17/028 VL - 17 IS - 17 SP - 4451 EP - 4455 PB - IOP ER - TY - JOUR A1 - Ross, Frances M. A1 - Kammler, Martin A1 - Reuter, Mark C. A1 - Hull, Robert T1 - In-situ observations of self-assembled island nucleation on patterned substrates JF - Philosophical Magazine N2 - We compare in-situ electron microscopy observations of Ge island growth on Si surfaces modulated by different techniques. Si(001) substrates were patterned either using a focused Ga ion beam or lithographically to produce similar feature sizes. In the case of the focused-ion-beam patterned substrates, chemical or strain effects caused by low Ga doses control the positions at which islands nucleate. Nucleation on topographically modulated substrates, with the pattern produced either by high-dose sputtering or lithographically, is controlled by the nature of the side walls of topographic features. The two patterning approaches have different benefits in creating arrays of islands for device applications. Y1 - 2004 U6 - https://doi.org/10.1080/14786430410001671430 VL - 84 IS - 25-26 SP - 2687 EP - 2702 PB - Taylor & Francis ER - TY - JOUR A1 - Menzel, Andreas A1 - Conrad, E. H. A1 - Tringides, Michael C. A1 - Kammler, Martin A1 - Horn- von Hoegen, Michael T1 - Finite collection time effects in autocovariance function measurements JF - Journal of Applied Physics N2 - In this paper we discuss how finite data sets influence experimental measurements of the autocovariance function. Autocovariance estimators are biased, meaning that the expectation value for any measured autocovariance function is not identical to the actual autocovariance function. In this work we show that the measured autocovariance function for a finite length time series must become negative for some lag times. We derive analytic corrections to these finite time errors for different types of correlated random sequences. Our results explain the apparent anticorrelated noise observed in experimental observations. Y1 - 2003 U6 - https://doi.org/10.1063/1.1537466 VL - 93 IS - 4 SP - 2229 EP - 2235 PB - AIP Publishing ER - TY - JOUR A1 - Kammler, Martin A1 - Hull, Robert A1 - Reuter, Mark C. A1 - Ross, Frances M. T1 - Lateral control of self-assembled island nucleation by focused-ion-beam micropatterning JF - Applied Physics Letters N2 - We demonstrate that the nucleation sites of nanoscale, self-assembled Ge islands on Si(001) can be controlled by patterning the Si surface in situ with a focused ion beam. At low doses of 6000 Ga+ ions per <100 nm spot, the selective growth is achieved without modifying the initial surface topography. At larger doses, topographic effects produced by sputtering and redeposition control the selective nucleation sites. Islands grown on irradiated spots are smaller with higher aspect ratio than islands grown on clean Si(001), suggesting a strong surfactant effect of Ga. Y1 - 2003 U6 - https://doi.org/10.1063/1.1542680 VL - 82 IS - 7 SP - 1093 EP - 1095 ER - TY - JOUR A1 - Sokolowski-Tinten, Klaus A1 - Blome, Christian A1 - Blums, Juris A1 - Shymanovich, Uladzimir A1 - Nicoul, Matthieu A1 - Cavalleri, Andrea A1 - Tarasevitch, A. A1 - Horn-von Hoegen, Michael A1 - Kammler, Martin A1 - von der Linde, D. T1 - Ultrafast X-ray diffraction JF - Ultrafast Phenomena XIV N2 - In the last few years the generation of femtosecond pulses in the X-ray regime has become possible. These ultrashort X-ray pulses have enabled femtosecond time- resolution to be extended to X-rays. Y1 - 2005 U6 - https://doi.org/10.1007/3-540-27213-5_53 VL - 79 SP - 170 EP - 174 PB - Springer ER - TY - JOUR A1 - Kammler, Martin A1 - Hull, Robert A1 - Portavoce, A. A1 - Reuter, Mark C. A1 - Ross, Frances M. T1 - In-Situ Focused Ion Beam Micropatterning of Ge Islands JF - Microscopy and Microanalysis Y1 - 2003 U6 - https://doi.org/10.1017/S1431927603441214 VL - 9 IS - S02 SP - 132 EP - 134 PB - Microscopy Society of America ER - TY - JOUR A1 - Fritz, D. M. A1 - Reis, D. A. A1 - Adams, B. A1 - Akre, R. A. A1 - Arthur, J. A1 - Blome, Christian A1 - Bucksbaum, P. H. A1 - Cavalieri, A. L. A1 - Engemann, S. A1 - Fahy, S. A1 - Falcone, R. W. A1 - Fuoss, P. H. A1 - Gaffney, K. J. A1 - George, M. J. A1 - Hajdu, J. A1 - Hertlein, M. P. A1 - Hillyard, P. B. A1 - Horn-von Hoegen, Michael A1 - Kammler, Martin A1 - Kaspar, J. A1 - Kienberger, R. A1 - Krejcik, P. A1 - Lee, S. H. A1 - Lindenberg, A. M. A1 - McFarland, B. A1 - Meyer, D. A1 - Montagne, T. A1 - Murray, E. D. A1 - Nelson, A. J. A1 - Nicoul, Matthieu A1 - Pahl, R. A1 - Rudati, J. A1 - Schlarb, H. A1 - Siddons, D. P. A1 - Sokolowski-Tinten, Klaus A1 - Tschentscher, Th A1 - von der Linde, D. A1 - Hastings, J. B. T1 - Ultrafast bond softening in bismuth: mapping a solid's interatomic potential with X-rays JF - Science N2 - Intense femtosecond laser excitation can produce transient states of matter that would otherwise be inaccessible to laboratory investigation. At high excitation densities, the interatomic forces that bind solids and determine many of their properties can be substantially altered. Here, we present the detailed mapping of the carrier density-dependent interatomic potential of bismuth approaching a solid-solid phase transition. Our experiments combine stroboscopic techniques that use a high-brightness linear electron accelerator-based x-ray source with pulse-by-pulse timing reconstruction for femtosecond resolution, allowing quantitative characterization of the interatomic potential energy surface of the highly excited solid. Y1 - 2007 U6 - https://doi.org/10.1126/science.1135009 VL - 315 IS - 5812 SP - 633 EP - 636 PB - AAAS ER - TY - CHAP A1 - Sokolowski-Tinten, Klaus A1 - Blome, Christian A1 - Blums, Juris A1 - Shymanovich, Uladzimir A1 - Nicoul, Matthieu A1 - Cavalleri, Andrea A1 - Tarasevitch, A. A1 - Horn-von Hoegen, Michael A1 - Kammler, Martin A1 - von der Linde, Dietrich ED - Kobayashi, Tetsuro T1 - Ultrafast X-ray diffraction T2 - Ultrafast Phenomena XIV N2 - In the last few years the generation of femtosecond pulses in the X-ray regime has become possible. These ultrashort X-ray pulses have enabled femtosecond time- resolution to be extended to X-rays. Y1 - 2004 SN - 978-3-540-27213-7 U6 - https://doi.org/10.1007/3-540-27213-5_53 VL - 79 SP - 170 EP - 174 PB - Springer CY - Berlin, Heidelberg ER - TY - JOUR A1 - Kammler, Martin A1 - Horn- von Hoegen, Michael A1 - Voss, N. A1 - Tringides, Michael C. A1 - Menzel, Andreas A1 - Conrad, E. H. T1 - Si(001) step dynamics: A temporal low-energy electron diffraction study JF - Physical Review B N2 - We present equilibrium measurements of the dynamics of steps on Si(001) using temporal electron-diffraction spectroscopy. Activation energies and the rate limiting kinetics are identified for 950K<~T<~1130K. Unlike previous studies at higher temperatures, we can exclude evaporation and condensation of atoms or dimers from the step edges as the rate limiting process in this temperature regime. The possible reason for this difference is discussed in terms of a crossover from different rate-limiting kinetics. Y1 - 2002 U6 - https://doi.org/10.1103/PhysRevB.65.075312 VL - 65 IS - 7 PB - APS ER - TY - JOUR A1 - Krenzer, Boris A1 - Hanisch-Blicharski, Anja A1 - Schneider, Paul A1 - Payer, Thomas A1 - Möllenbeck, Simone A1 - Osmani, O. A1 - Kammler, Martin A1 - Meyer, R. A1 - Horn-von Hoegen, Michael T1 - Phonon confinement effects in ultrathin epitaxial bismuth films on silicon studied by time-resolved electron diffraction JF - Physical Review B N2 - The transient temperature evolution of ultrathin bismuth films, epitaxially grown on a silicon single crystal, upon femtosecond laser excitation is studied by time-resolved electron diffraction. The exponential decay of the film temperature is explained by phonon reflection at the interface, which results in a strongly reduced thermal conduction in the cross plane of the layered system. The thermal boundary conductance is found to be as low as 1273 W/(K cm2). Model calculations, including phonon confinement effects, explain the linear relationship between the observed film-temperature decay constant and the film thickness. Even for 2.5 nm thin films the phonon transmission probability across the interface is given by bulk properties. Our simulations show that phonon confinement effects are negligible for bismuth-film thicknesses larger than 1 nm. Y1 - 2009 U6 - https://doi.org/10.1103/PhysRevB.80.024307 VL - 80 IS - 2 PB - APS ER - TY - JOUR A1 - Klein, C. A1 - Nabbefeld, T. A1 - Hattab, H. A1 - Meyer, D. A1 - Jnawali, G. A1 - Kammler, Martin A1 - Meyer zu Heringdorf, Frank-Joachim A1 - Golla-Franz, A. A1 - Müller, B. H. A1 - Schmidt, Thomas A1 - Henzler, M. A1 - Horn-von Hoegen, Michael T1 - Lost in reciprocal space? Determination of the scattering condition in spot profile analysis low-energy electron diffraction JF - Review of scientific instruments N2 - The precise knowledge of the diffraction condition, i.e., the angle of incidence and electron energy, is crucial for the study of surface morphology through spot profile analysis low-energy electron diffraction (LEED). We demonstrate four different procedures to determine the diffraction condition: employing the distortion of the LEED pattern under large angles of incidence, the layer-by-layer growth oscillations during homoepitaxial growth, a G(S) analysis of a rough surface, and the intersection of facet rods with 3D Bragg conditions. Y1 - 2011 U6 - https://doi.org/10.1063/1.3554305 VL - 82 IS - 3 PB - American Institute of Physics ER - TY - JOUR A1 - Schmidt, Thomas A1 - Kröger, Roland A1 - Clausen, T. A1 - Falta, J. A1 - Janzen, Andreas A1 - Kammler, Martin A1 - Kury, P. A1 - Zahl, P. A1 - Horn-von Hoegen, Michael T1 - Surfactant-mediated epitaxy of Ge on Si(111): Beyond the surface JF - Applied Physics Letters N2 - For a characterization of interface and “bulk” properties of Ge films grown on Si(111) by Sb surfactant-mediated epitaxy, grazing incidence x-ray diffraction and transmission electron microscopy have been used. The interface roughness, defect structure, and strain state have been investigated in dependence of film thickness and growth temperature. For all growth parameters, atomically smooth interfaces are observed. For thin Ge layers, about 75% of the strain induced by the lattice mismatch is relaxed by misfit dislocations at the Ge/Si interface. Only a slight increase of the degree of relaxation is found for thicker films. At growth temperatures below about 600 °C, the formation of twins is observed, which can be avoided at higher temperatures. Y1 - 2005 U6 - https://doi.org/10.1063/1.1882760 VL - 86 IS - 11 PB - AIP ER - TY - JOUR A1 - Frigge, Tim A1 - Wall, S. A1 - Krenzer, Boris A1 - Wippermann, St. A1 - Sanna, Simone A1 - Klasing, Friedrich A1 - Hanisch-Blicharski, Anja A1 - Kammler, Martin A1 - Schmidt, Wolf Gero A1 - Horn-von Hoegen, Michael T1 - Abstract - A Reply to the Comment by H. Shim et al. JF - Physical review letters Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevLett.111.149602 VL - 111 IS - 14 PB - American Physical Society ER - TY - JOUR A1 - Chee, See Wee A1 - Kammler, Martin A1 - Graham, Jeremy A1 - Ross, Frances M. A1 - Hull, Robert T1 - Direct Imaging of Microstructural Changes in Si Induced by FIB-Patterning with Si ++ and Ga + Ions JF - Microscopy and Microanalysis Y1 - 2011 U6 - https://doi.org/10.1017/S1431927611004156 VL - 17 IS - S2 SP - 656 EP - 657 PB - Cambridge University Press ER - TY - JOUR A1 - Wolfgramm, Alex A1 - Abb, Valerius A1 - Samp, Artur A1 - Samp, Rafal A1 - Hoffmann, Jens Christoph A1 - Müller, Rainer A1 - Kammler, Martin T1 - Structural and functional evolution of HKUST-1 nanoparticles induced by ball milling JF - Next Materials N2 - In this study, the effect of post-synthetic ball milling on the structural and functional properties of as-synthesized nanoparticles of the copper-based metal-organic framework (MOF) HKUST-1 was investigated for the first time. Nanoparticles were synthesized using sodium formate as a capping agent. The crystalline particles were subjected to a controlled ball milling process, which induced significant structural changes. Powder X-ray diffraction (PXRD) revealed a reduction in crystallite size from 91 nm to 21 nm and the introduction of microstrain, partially disrupting the MOF's long-range crystalline order, as evidenced by peak broadening and the diminished intensity of high-angle reflections. Particle morphology pre- and post-milling was further studied with scanning electron microscopy (SEM) imaging, verifying a narrow particle size distribution of ± 22 nm after milling. Fourier-transform infrared spectroscopy (FTIR) indicated protonation of carboxylate groups in the larger pores of the framework, likely due to moisture incorporation during milling. Brunauer-Emmett-Teller (BET) surface area analysis showed a substantial decrease in specific surface area from 521 m²/g to 226 m²/g, suggesting a partial collapse of the porous framework. We discuss the applicability of ball milling as a versatile means of post-synthetic approach to reduce MOF particle sizes, a key element in the preparation of MOF-based thin films using inks or polymers. KW - Ball milling KW - Copper-based metal-organic framework KW - HKUST-1 KW - Nitrogen adsorption Y1 - 2026 U6 - https://doi.org/10.1016/j.nxmate.2025.101544 N1 - Corresponding author der OTH Regensburg: Alex Wolfgramm VL - 10 PB - Elsevier ER -