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In this work, nanodiodes comprised of n-GaN nanowires on p-diamond substrates are investigated. The electric trans-port properties are discussed on the basis of simulations and determined experimentally for individual p-diamond/n-GaN nanodiodes by applying conductive atomic force microscopy. For low doping concentrations, a high rectification ratio is observed. The fabrication of a prototype nanoLED device on the basis of ensemble nanowire contacts is presented, showing simultaneous electroluminescence in the UV and the green spectral range which can be ascribed to hole injection into the n-GaN nanowires and electron injection into the p-diamond, respectively. In addition, the operation and heat distribution of the nanoLED device are visualized by active thermographic imaging.

Nanocrystalline diamond- (NCD) and AlN-based ultrathin single layer and bilayer membranes are investigated towards their mechanical properties. It is shown that chemo-mechanical polishing and heavy boron doping of NCD thin films do not impact the elastic properties of NCD layers as revealed by negligible variations of the NCD Young's modulus (E). In addition, it is demonstrated that the combination of NCD elastic layer and AlN piezo-actuator is highly suitable for the fabrication of mechanically stable ultrathin membranes in comparison to AlN single layer membranes. The elastic parameters of NCD/AlN heterostructures are mainly determined by the outstanding high Young's modulus of NCD (E = 1019 ± 19 GPa). Such ultrathin unimorph membranes allow for fabrication of piezo-actuated AlN/NCD microlenses with tunable focus length.

The surface termination of single crystalline diamond with fluorine and chlorine was investigated. The diamond was exposed to SF(6) inductively coupled plasma for fluorination and to Cl(2) plasma for chlorination. For the fluorine termination, the plasma treatment caused one monolayer of fluorine (measured with two angle photoelectron detection) and no carbonyl fluorides on the diamond surface. Furthermore no graphitization or roughening of the surface was observed. The plasma treatment with chlorine led to rough surfaces.

We report on the grain size dependent morphological, physical and chemical properties of thick microwaveplasma assisted chemical vapor deposited (MPCVD) diamond films that are used as target materials for high energy density physics experiments at the Lawrence Livermore National Laboratory. Control over the grain size, ranging from several µm to a few nm, was achieved by adjusting the CH(4) content of the CH(4)/H(2) feed gas. The effect of grain size on surface roughness, morphology, texture, density, hydrogen and graphitic carbon content was systematically studied by a variety of techniques. For depositions performed at 35 to 45mbar and 3000W microwave power (power density ~10 W cm(-3)), an abrupt transition from micro-crystalline diamond to nanocrystalline diamond was observed at 3% CH(4). This transition is accompanied by a dramatic decrease in surface roughness, a six percent drop in density and an increasing content in hydrogen and graphitic carbon impurities. Guided by these results, layered nano-microhybrid diamond samples were prepared by periodically changing the growth conditions from nano- to microcrystalline.

Unimorph heterostructures based on piezoelectric aluminum nitride (AlN) and diamond thin films are highly desirable for applications in micro- and nanoelectromechanical systems. In this paper, we present a new approach to combine thin conductive boron-doped as well as insulating nanocrystalline diamond (NCD) with sputtered AlN films without the need for any buffer layers between AlN and NCD or polishing steps. The zeta potentials of differently treated nanodiamond (ND) particles in aqueous colloids are adjusted to the zeta potential of AlN in water. Thereby, the nucleation density for the initial growth of diamond on AlN can be varied from very low (10(8) cm(-2)), in the case of hydrogen-treated ND seeding particles, to very high values of 10(11) cm(-2) for oxidized ND particles. Our approach yielding high nucleation densities allows the growth of very thin NCD films on AlN with thicknesses as low as 40 nm for applications such as microelectromechanical beam resonators. Fabricated piezo-actuated micro-resonators exhibit enhanced mechanical properties due to the incorporation of boron-doped NCD films. Highly boron-doped NCD thin films which replace the metal top electrode offer Young's moduli of more than 1000 GPa.

Various nano-pores in nano-crystalline diamond (NCD) thin films have been fabricated and characterized. Therefore in this work two aspects of NCD thin films synthesized by microwave assisted chemical-vapour-deposition (MWCVD) have been investigated. Firstly, the influence of CVD-growth conditions on the film morphology and chemical grain boundary composition and their impact on the mechanical properties. Second, the formation of nano-pores by selective etching of the non-diamond phase. Freestanding NCD membranes were fabricated and bulged to calculate the Young's modulus which can reach surprisingly high values (1100 GPa) close to single crystal diamond. The presence of nano-pores was verified by electrochemical experiments where ions have been used to detect the porosity.

International audience; Nickel doped single crystal diamond layers were grown by microwave-plasma enhanced chemical vapour deposition. Optical emission spectroscopy (OES) utilised during growth proved that the organometallic compound nickelocene is an applicable nickel source. It was possible to produce stable and adjustable nickel OES signals during growth by altering the flux of the nickelocene carrier gas. The successful incorporation of nickel into the diamond layers was verified by secondary ion mass spectrometry. Cathodoluminescence (CL) was applied to reveal optically active defects related to nickel. The signature of substitutionally incorporated nickel, namely the nickel related 1.4 eV centre, as well as the 2.369 and 1.563 eV centres were observed in CL. The latter is supposed to be a single-photon emitter on the basis of a nickel-nitrogen defect centre.

The investigation of orientation dependent crystal growth and etch processes can provide deep insights into the underlying mechanisms and thus helps to validate theoretical models. Here, we report on homoepitaxial diamond growth and oxygen etch experiments on polished, polycrystalline CVD diamond wafers by use of electron backscatter diffraction (EBSD) and white-light interferometry (WLI). Atomic force microscopy (AFM) was applied to provide additional atomic scale surface morphology information. The main advantage of using polycrystalline diamond substrates with almost random grain orientation is that it allows determining the orientation dependent growth (etch) rate for different orientations within one experiment. Specifically, we studied the effect of methane concentration on the diamond growth rate, using a microwave plasma CVD process. At 1% methane concentration a maximum of the growth rate near and a minimum near is detected. Increasing the methane concentration up to 5% shifts the maximum towards while the minimum stays at . Etch rate measurements in a microwave powered oxygen plasma reveal a pronounced maximum at . We also made a first attempt to interpret our experimental data in terms of local micro-faceting of high-indexed planes.