Materials Literature
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In this letter, we describe the formation and ultralow friction mechanisms of a surface film on boron carbide (B4C). This film results from sequential reactions between B4C and oxygen and between the resulting boron oxide (B2O3) and moisture; it can afford friction coefficients of 0.03 to 0.05 to sliding steel surface…
Elastic neutron scattering measurements characterizing the charge and magnetic order in L${\mathrm{a}}_{0.5}$S${\mathrm{r}}_{1.5}$Mn${\mathrm{O}}_{4}$ are presented. Superlattice reflections corresponding to an alternating ${\mathrm{Mn}}^{+3}/{\mathrm{Mn}}^{+4}$ pattern with wave vector ${\mathbf{q}}_{\mathrm{co}}\pha…
The modification of the potential-energy surface (PES) of H_2 dissociation over Pd(100) as induced by the presence of a (2x2) S adlayer is investigated by density-functional theory and the linear augmented plane wave method. It is shown that the poisoning effect of S originates from the formation of energy barriers hi…
Measurements in PMMA of both the energy flux into the tip of a moving crack and the total surface area created via the microbranching instability indicate that the instability is the main mechanism for energy dissipation by a moving crack in brittle, amorphous material. Beyond the instability onset, the rate of fractu…
A database of ab initio calculations of the chemisorption energy of CO over Ni(111), Cu(111), Ru(0001), Pd(111), Ag(111), Pt(111), Au(111), $\mathrm{Cu}{}_{3}$Pt(111), and some metallic overlayer structures is presented. The trends can be reproduced with a simple model describing the interaction between the metal $d$…
The following paper describes an in-situ approach to studies of hot filament chemical vapour deposition (HFCVD) thin film growth. It based on the use of a HFCVD experimental setup in the chamber of an environmental scanning electron microscope (ESEM). The initial stages of diamond thin film growth were examined at tim…
A new technique to measure the thermal conductivity k(T)of CVD diamond is presented. The thermal conductivity parallel to the surface of films with thicknesses ranging from 2 μm up to several hundred μm can be determined over a wide temperature range. The measurements are carried out with micromechanical devices, that…
Modern thin film sensor technology imposes stringent demands upon material quality, highly qualified downstream process technologies, device performance and integrity. Since the earliest stages of its development, crystalline thin film diamond has been promoted as a semiconductor material for high power, high frequenc…
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…