Materials Literature
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Natural type IIb diamond surfaces of (100), (110), and (111) orientation, as well as chemical vapor deposited (CVD) diamond thin films with (100), (110), or mixed orientation are probed by photoelectron spectroscopy in the ultraviolet (UPS) and X-ray (XPS) energy regimes. Dramatic changes can be observed in the valenc…
A series of highly oriented and textured microwave CVD diamond films, where only the deposition time was varied, was deposited on silicon wafers in order to follow the evolution of the microstructure and defect content with film thickness. SEM, XRD, Raman spectroscopy, luminescence measurements, and ESR were applied t…
After the successful controlled heteroepitaxial nucleation of diamond on 3C-SiC epitaxial films and on bare silicon wafers, respectively, obtained by research groups in the USA and Germany in 1992, considerable technical progress and scientifical understanding in the area of heteroepitaxy of CVD diamond have been achi…
Graphitic layers have previously been conjectured to play an active role in diamond nucleation by Lambrecht et al. and may also be involved in a mechanism for homoepitaxial diamond growth since the surfaces of diamond may partially graphitize under high-temperature conditions typical of growth processes. Recent molecu…
The introduction of the bias pretreatment process for in-situ nucleation of oriented diamond crystallites on silicon was an important step towards heteroepitaxial deposition of single crystalline diamond films. However, the quality of these films is still limited mainly due to a significant orientational spread of the…
The mechanisms of bias enhanced nucleation (BEN) of diamond on silicon substrates are investigated by means of electrical measurements. OES investigations, and macroscopic as well as local characterization of BEN films. Based on electrical investigations we propose that the reproducibility and homogeneity problems oft…
Temperature dependent resistivity and Hall measurements have been carried out on in situ boron doped polycrystalline diamond films. The temperature dependence of the resistivity can be described by a two band conduction model with two conduction mechanisms working parallel. A fair agreement between the depth distribut…
For electronic applications, a series of boron-doped homoepitaxial diamond layers of high crystal quality have been grown on (100)-cut diamond substrates using the microwave plasma CVD method. The B-concentration varies from 3 × 1017 to 3 × 1020 atoms/cm3. The layers are selectively grown into the shape of Hall bars u…
Ammonium‐ und Borat‐Substituenten polarisieren π‐Elektronensysteme, die deshalb interne CT‐Banden im UV/Vis‐Spektrum aufweisen. Diese Systeme, z.B. 1 , sind deutlich transparenter als analoge push‐pull‐substituierte Verbindungen; ihre Hyperpolarisierbarkeiten erster Ordnung sind aber trotzdem etwa gleich groß, was sie…
In zwei aufeinanderfolgenden Einelektronen‐Oxidationen lassen sich Phenyl‐Endgruppen tragende Oligopyrrole der Formel PhPy n Ph, n = 2–4, reversibel zu stabilen Radikalkationen und Dikationen umsetzen. Spektroelektrochemische Untersuchungen weisen klar auf die Bildung diamagnetischer π‐Dimere von Radikalkationen in Lö…
The angular dependence of surface magnetic Barkhausen noise (MBN) with flux densities up to 1.7 T on eight different samples of oriented 3% Si–Fe steel laminate was investigated. On two of the samples encircle MBN measurements were performed. MBN energy values were obtained by integrating the square of the MBN voltage…
Single crystals of strontium metaborate, SrB2O4, were grown for the first time from the melt by the Czochralski method and a detailed structure analysis was carried out. The Sr atom is dodecahedrally coordinated by eight O atoms from the neighbouring infinite planes consisting of borate molecules so that all O atoms i…
The dissociative chemisorption of oxygen on Pt{100}-(1×1) has been investigated using supersonic molecular beams with incident translational energies between 0.04 and 0.90 eV over the surface temperature range 300 to 380 K. The adsorption process on the Pt{100}-(1×1) surface is found to differ from that on the reconst…
High germanium content ${\mathrm{Si}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Ge}}_{\mathit{x}}$ alloys have been grown pseudomorphically at 400 \ifmmode^\circ\else\textdegree\fi{}C on Ge (001) by molecular-beam epitaxy. The germanium fraction determined using x-ray diffraction measurements (x=0.8) is in good a…
The emission properties of a new phosphor based on LiTaO3:Tb3+ are described. It is shown to be a storage phosphor, i.e., after previous x-ray exposure, Tb3+ emission in green-red region of spectrum can be photostimulated by light in 400–800 nm spectral range. Emission centers (Tb3+ ions), electron storage centers (ox…
Drops of molten silicon surrounded by a SiO2–BaO–CaO flux were undercooled at 350 K below their melting temperature. This undercooling is 75 K greater than the largest one reported so far for bulk silicon. To account for this result as well as the nucleation data from laser-melted thin films, classical nucleation theo…
It is shown that the low frequency collective modes of quasilinear polymers can contribute to the vibrational polarizability and hyperpolarizability despite the fact that their infrared or Raman intensity vanishes in the infinite chain limit. The most significant of these modes are characterized and the dynamic vibrat…
We report temperature-dependent redistribution of spectral weight in photoemission spectra of ${\mathrm{La}}_{0.6}$${\mathrm{Sr}}_{0.4}$${\mathrm{MnO}}_{3}$ over a wide energy range of several eV. We attribute this to a change in the electron correlation strength induced by the changing degree of ferromagnetic order w…
In this study we present photoemission data for three different types of amorphous carbon modifications (a-C:H, ta-C:H, and ta-C) that owe their properties to their different preparations by radio frequency plasma, plasma beam, or arc discharge. Their properties are investigated by means of their characteristic plasmo…
Using synchrotron radiation, we have performed a high-resolution X-ray diffraction study of a phase transition between the incommensurate phase and the commensurate phase characterized by the wave vector q =3 c * /7 in [N(CH 3 ) 4 ] 2 MnCl 4 under pressure. The pressure dependence of the wave vector q exhibits an “inc…