Showing papers by "Hans-Gerd Boyen published in 2000"
TL;DR: In this paper, a method for generating quasiregular arrays of nanometer-sized noble metal and metal oxide clusters on flat substrates by the use of a polymer template was presented.
Abstract: A method is presented for generating quasiregular arrays of nanometer-sized noble metal and metal oxide clusters on flat substrates by the use of a polymer template. The approach is of general applicability to other metals and various oxides. In the first step, polymeric micelles with a polar core were generated by dissolution of poly(styrene)-block-poly(2-vinylpyridine) in toluene. These micelles were used as nanocompartments that were loaded with a defined amount of a metal precursor. The metal ions can be reduced in such a way that exactly one elemental or oxidic particle is formed in each micelle, where each particle is of equal size. By dipping a flat substrate into a dilute solution, a monolayer of the micelles was obtained whereby the embedded equally large particles became arranged in a mesoscopic quasihexagonal two-dimensional (2-D) lattice. Exposure to an oxygen plasma allowed removal of the polymer completely, leaving the naked metal particles firmly attached to the substrate in the same quasih...
585 citations
TL;DR: In this article, it was shown that the bombardment of high quality cubic (c-) BN films with 300 keV Ar+ ions leads to a strong relaxation of their compressive stresses without destroying the cubic phase if the total ion fluence is kept below an upper limit.
Abstract: It is shown that the bombardment of high quality cubic (c-) BN films with 300 keV Ar+ ions leads to a strong relaxation of their compressive stresses without destroying the cubic phase if the total ion fluence is kept below an upper limit. In addition, it was found that on top of such a stress-relieved film a further pure c-BN layer can be grown, but it builds up compressive stress again. Based on both results, a procedure is developed to grow thick (>1 μm) c-BN films (>80% c-BN) exhibiting low residual stress and long term stability under ambient conditions.
83 citations
TL;DR: In this article, the self-organization of inverse polystyrene-block-poly(2-vinylpyridine) micelles is exploited for the preparation of cylindrical diamond columns of 15 nm height and 10 nm diameter.
Abstract: Cylindrical diamond columns of 15 nm height and 10 nm diameter have been prepared on a diamond(100) substrate by exploiting the self-organization of metal-loaded diblock copolymers. For this purpose, chemomechanically polished substrates of synthetic (high pressure high temperature) diamond exhibiting extremely low roughness (typical root-mean-square roughness 60 pm) were covered by a monolayer of gold-loaded inverse polystyrene-block-poly(2-vinylpyridine) micelles which self-organize in an hexagonal order on the substrate. After burning off the blockcopolymer in an oxygen plasma, the resulting Au nanoparticles act as a mask during further etching the diamond substrate in this plasma. As a result, Au-capped diamond columns are formed with an approximate size of the former gold particles. After removing the Au caps by evaporation at 1100 °C in ultrahigh vacuum, an array of diamond nanocolumns is obtained. As a consequence of this preparation process, the columns form an hexagonal lattice with a separation of 85 nm reflecting the arrangement of the self-organized micelles. The successive states of sample preparation were characterized by atomic force microscopy, Rutherford backscattering, and in situ scanning tunneling microscopy.
25 citations
01 Jan 2000
TL;DR: A short review of the current status of preparing films of cubic Boron Nitride, a material exhibiting similar attractive properties as diamond, can be found in this paper, where a procedure allowing to obtain thick (>1μm), stress relieved, superhard (48 GPa) samples, which are mechanically stable under ambient conditions.
Abstract: After a short review of the current status of preparing films of cubic Boron Nitride, a material exhibiting similar attractive properties as diamond, a procedure will be reported allowing to obtain thick (>1μm), stress relieved, superhard (48 GPa) samples, which are mechanically stable under ambient conditions.
11 citations
TL;DR: In this article, the electronic structure of liquid tungsten has been studied by time-resolved photo electron spectroscopy on laser pulse molten surface layers and the valence band spectra reveal distinct changes of the electronic structures across the solid-liquid phase transition.
Abstract: The electronic structure of liquid tungsten has been studied by time-resolved photo electron spectroscopy on laser pulse molten surface layers. The valence band spectra reveal distinct changes of the electronic structure across the solid-liquid phase transition which are interpreted by marked changes of the short-range order on melting which change qualitatively the valence electron density of states.
10 citations
TL;DR: In this article, the authors used photoelectron spectroscopy to obtain the valence band spectra of Pd and Mo in both the high temperature solid phase and the liquid phase under identical experimental conditions.
Abstract: Photoelectron spectroscopy measurements on liquid transition metals are not feasible by conventional steady state experiments because of the elevated vapor pressures of these metals at the melting point. However, dynamic experiments with surface melting induced by pulsed laser irradiation combined with time resolved photoelectron spectroscopy make these experiments possible for the first time. Valence band spectra of Pd and Mo have been obtained by this method in both the high temperature solid phase and the liquid phase under identical experimental conditions. Both the elements reveal distinct changes in the valence band spectra on melting. The shapes of the 4d bands of the two metals in the liquid phase are in good agreement with the calculated spectra based on the ab initio density of states (DOS) calculations.
4 citations