@incollection{SokolowskiTintenvonderLindeSidersetal., author = {Sokolowski-Tinten, Klaus and von der Linde, D. and Siders, C. W. and Cavalleri, Andrea and T{\´o}th, Csaba and Guo, T. and Wilson, K. R. and Barty, C. P. J. and Kammler, Martin and Horn-von Hoegen, Michael}, title = {Lattice dynamics of femtosecond laser-excited semiconductors probed by ultrafast x-ray diffraction}, series = {Applications of High Field and Short Wavelength Sources VIII}, booktitle = {Applications of High Field and Short Wavelength Sources VIII}, publisher = {Optica}, doi = {10.1364/HFSW.1999.PD3}, abstract = {The present knowledge of the atomic structure of matter is to a large extent due to x-ray spectroscopies.}, language = {en} } @article{SchmidtKroegerFlegeetal., author = {Schmidt, Thomas and Kr{\"o}ger, Roland and Flege, Jan Ingo and Horn-von Hoegen, Michael and Clausen, T. and Falta, J. and Janzen, Andreas and Zahl, P. and Kury, P. and Kammler, Martin}, title = {Less strain energy despite fewer misfit dislocations: the impact of ordering}, series = {Physical review letters}, volume = {96}, journal = {Physical review letters}, number = {6}, publisher = {APS}, doi = {10.1103/PhysRevLett.96.066101}, abstract = {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.}, language = {en} } @article{HullGrayKammleretal., author = {Hull, Robert and Gray, J. L. and Kammler, Martin and Vandervelde, T. and Kobayashi, Takeshi and Kumar, P. and Pernell, T. and Bean, J. C. and Floro, J. A. and Ross, Frances M.}, title = {Precision placement of heteroepitaxial semiconductor quantum dots}, series = {Materials Science and Engineering: B}, volume = {101}, journal = {Materials Science and Engineering: B}, number = {1-3}, publisher = {Elsevier}, doi = {10.1016/S0921-5107(02)00680-3}, pages = {1 -- 8}, abstract = {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 ({\^A}/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.}, language = {en} } @article{HanischBlicharskiJanzenKrenzeretal., author = {Hanisch-Blicharski, Anja and Janzen, Andreas and Krenzer, Boris and Wall, S. and Klasing, Friedrich and Kalus, Annika and Frigge, Tim and Kammler, Martin and Horn-von Hoegen, Michael}, title = {Ultra-fast electron diffraction at surfaces: from nanoscale heat transport to driven phase transitions}, series = {Ultramicroscopy}, volume = {127}, journal = {Ultramicroscopy}, publisher = {Elsevier}, doi = {10.1016/j.ultramic.2012.07.017}, pages = {2 -- 8}, abstract = {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.}, language = {en} } @article{MenzelKammlerConradetal., author = {Menzel, Andreas and Kammler, Martin and Conrad, E. H. and Yeh, V. and Hupalo, Myron and Tringides, Michael C.}, title = {Kinetics measurements of Pb island growth on Si(111)}, series = {Physical Review B}, volume = {67}, journal = {Physical Review B}, number = {16}, publisher = {American Physical Society}, doi = {10.1103/PhysRevB.67.165314}, abstract = {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.}, language = {en} } @inproceedings{KammlerHornvonHoegenVossetal., author = {Kammler, Martin and Horn- von Hoegen, Michael and Voss, N. and Tringides, Michael C. and Menzel, Andreas and Conrad, E. H.}, title = {Surface Dynamics of Stepped Si(001) Studied by Temporal Leed Spectroscopy}, series = {Collective Diffusion on Surfaces: Correlation Effects and Adatom Interactions (NATO Science Series II: Mathematics, Physics and Chemistry}, volume = {29}, booktitle = {Collective Diffusion on Surfaces: Correlation Effects and Adatom Interactions (NATO Science Series II: Mathematics, Physics and Chemistry}, publisher = {Springer}, doi = {10.1007/978-94-010-0816-7_3}, pages = {23 -- 32}, abstract = {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.}, language = {en} } @article{StreubuehrKalusZhouetal., author = {Streub{\"u}hr, C. and Kalus, Annika and Zhou, Ping and Ligges, Manuel and Hanisch-Blicharski, Anja and Kammler, Martin and Bovensiepen, U. and Horn-von Hoegen, Michael and von der Linde, D.}, title = {Comparing ultrafast surface and bulk heating using time-resolved electron diffraction}, series = {Applied Physics Letters}, volume = {104}, journal = {Applied Physics Letters}, publisher = {American Institute of Physics}, doi = {10.1063/1.4872055}, pages = {1 -- 3}, abstract = {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.}, language = {en} } @inproceedings{ShymanovichNicoulLuetal., author = {Shymanovich, Uladzimir and Nicoul, Matthieu and Lu, Wei and Tarasevitch, A. and Kammler, Martin and Horn-von Hoegen, Michael and von der Linde, D. and Sokolowski-Tinten, Klaus and Phipps, Claude}, title = {Coherent acoustic and optical phonons in laser-excited solids studied by ultrafast time-resolved X-ray diffraction}, series = {AIP Conference Proceedings}, booktitle = {AIP Conference Proceedings}, number = {1}, publisher = {AIP}, doi = {10.1063/1.3507146}, pages = {558 -- 566}, abstract = {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.}, language = {en} } @article{PayerKleinAcetetal., author = {Payer, Thomas and Klein, C. and Acet, M. and Ney, V. and Kammler, Martin and Meyer zu Heringdorf, Frank-Joachim and Horn-von Hoegen, Michael}, title = {High-quality epitaxial Bi(111) films on Si(111) by isochronal annealing}, series = {Thin Solid Films}, volume = {520}, journal = {Thin Solid Films}, number = {23}, publisher = {Elsevier}, doi = {10.1016/j.tsf.2012.06.004}, pages = {6905 -- 6908}, abstract = {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\%.}, language = {en} } @inproceedings{ZhouStreubuehrKalusetal., author = {Zhou, Ping and Streub{\"u}hr, C. and Kalus, Annika and Frigge, Tim and Wall, S. and Hanisch-Blicharski, Anja and Kammler, Martin and Ligges, Manuel and Bovensiepen, U. and von der Linde, D. and Horn-von Hoegen, Michael}, title = {Ultrafast time resolved reflection high energy electron diffraction with tilted pump pulse fronts}, series = {EPJ Web of Conferences - XVIIIth International Conference on Ultrafast Phenomena}, volume = {41}, booktitle = {EPJ Web of Conferences - XVIIIth International Conference on Ultrafast Phenomena}, publisher = {EPJ}, doi = {10.1051/epjconf/20134110016}, abstract = {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.}, language = {en} }