Peter Kratzer

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We establish a new mechanism for self-propelled motion of droplets, in which ordering of the nanoscale step morphology by sublimation beneath the droplets themselves acts to drive them perpendicular and up the surface steps. The mechanism is demonstrated and explored for Ga droplets on GaP(111)B, using several experimental techniques allowing studies of the(More)
We determine the detailed differences in geometry and band structure between wurtzite (Wz) and zinc blende (Zb) InAs nanowire (NW) surfaces using scanning tunneling microscopy/spectroscopy and photoemission electron microscopy. By establishing unreconstructed and defect-free surface facets for both Wz and Zb, we can reliably measure differences between(More)
Density-functional theory calculations are employed to investigate both the epitaxial growth and the magnetic properties of thin Mn and MnSi films on Si(001). For single Mn adatoms, we find a preference for the second-layer interstitial site. While a monolayer Mn film is energetically unfavorable, a capping-Si layer significantly enhances the thermodynamic(More)
We have studied the stability, the electronic, and the magnetic properties of Co2MnSi(001) thin films for 15 different terminations using density functional theory calculations. The phase diagram obtained by ab initio atomistic thermodynamics shows that in practice the MnSi, pure Mn, or pure Si terminated surfaces can be stabilized under suitable(More)
The atomic arrangement of the technologically important As-rich GaAs 001 2 3 4 reconstructed surface is determined using bias-dependent scanning tunneling microscopy (STM) and first-principles electronic structure calculations. The STM images reveal the relative position and depth of the atomicscale features within the trenches between the top-layer As(More)
Thin-film solar cells with CuIn(x)Ga(1-x)Se2 (CIGS) absorber are still far below their efficiency limit, although lab cells already reach 20.1%. One important aspect is the homogeneity of the alloy. Large-scale simulations combining Monte Carlo and density functional calculations show that two phases coexist in thermal equilibrium below room temperature.(More)
Using density-functional theory within the generalized gradient approximation, we show that Si-based heterostructures with 1/4 layer delta doping of interstitial Mn (Mn(int)) are half-metallic. For Mn(int) concentrations of 1/2 or 1 layer, the states induced in the band gap of delta-doped heterostructures still display high spin polarization, about 85% and(More)
This article reviews the basic computational techniques for carrying out multiscale simulations using statistical methods, with the focus on simulations of epitaxial growth. First, the statistical-physics background behind Monte Carlo simulations is briefly described. The kinetic Monte Carlo (kMC) method is introduced as an extension of the more wide-spread(More)
We have succeeded in direct atomic scale imaging of the exterior surfaces of III-V nanowires by scanning tunneling microscopy (STM). By using atomic hydrogen, we expose the crystalline surfaces of InAs nanowires with regular InP segments in vacuum while retaining the wire morphology. We show images with atomic resolution of the two major types of InAs(More)