Thomas Kups

Growth control of AgTCNQ nanowire arrays by using a template-assisted electro-deposition method

The growth control of AgTCNQ nanowire arrays is achieved by using a template-assisted electro-deposition method. We find that the diffusion of the electrolyte into the nanopores plays an important role in the electro-deposition process, and an equilibrium between the reduction and diffusion is necessary to achieve continuous AgTCNQ nanowire arrays.

Nanoporous Gold Nanoparticles and Au/Al2O3 Hybrid Nanoparticles with Large Tunability of Plasmonic Properties

Nanoporous gold nanoparticles (NPG-NPs) with controlled particle size and pore size are fabricated via a combination of solid-state dewetting and a subsequent dealloying process. Because of the combined effects of size and porosity, the NPG-NPs exhibit greater plasmonic tunability and significantly higher local field enhancement as compared to solid NPs. The effects of the nanoscale porosity and pore size on the optical extinction are investigated for the NPG-NPs with different particle sizes experimentally and theoretically. The influences of both porosity and pore size on the plasmonic properties are very complicated and clearly different for small particles with dominated dipole mode and large particles with dominated quadrupole mode. Au/Al2O3 hybrid porous NPs with controlled porosity and composition ratio are fabricated through plasma-enhanced atomic layer deposition of Al2O3 into the porous structure. In the Au/Al2O3 hybrid porous NPs, both Au and Al2O3 components are bicontinuously percolated over the entire structure. A further red shift of the plasmon peak is observed in the hybrid NPs due to the change of the environmental refractive index. The high tunability of the plasmonic resonances in the NPG-NPs and the hybrid porous NPs can be very useful for many applications in sensing biological and organic molecules.

Structural Evolution of Sputtered Indium Oxide Thin Films

Structural Evolution of Sputtered Indium Oxide Thin Films The indium oxide thin films were deposited at room temperature by reactive magnetron sputtering in the mixture of oxygen and argon on silicon and oxidized silicon substrates. The influence of the oxygen flow in the reactive mixture and post-deposition annealing on the structural properties were investigated. The as deposited In2O3 films showed a dominating randomly oriented nanocrystalline structure of cubic In2O3. The grain size decreased with increasing oxygen concentration in the plasma. Annealing in reducing atmospheres (vacuum, nitrogen and argon), besides improving the crystallinity, led to a partial cubic to rhombohedral phase transition in the indium oxide films.

Buried melting in germanium implanted silicon by millisecond flash lamp annealing

Flash lamp annealing in the millisecond range has been used to induce buried melting in silicon. For this purpose high dose high-energy germanium implantation has been employed to lower the melting temperature of silicon in a predetermined depth region. Subsequent flash lamp treatment at high energy densities leads to local melting of the germanium rich layer. The thickness of the molten layer has been found to depend on the irradiation energy density. During the cool-down period, epitaxial crystallization takes place resulting in a largely defect-free layer.

Pyrolyzed Photoresist Film Electrodes for Application in Electroanalysis

Pyrolyzed Photoresist Film Electrodes for Application in Electroanalysis Pyrolyzed photoresist film (PPF) electrodes for application in electroanalysis were prepared on alumina substrates. These electrodes were characterized for their electrical, microstructural (by Raman spectroscopy) and electrochemical properties. As a support, the PPF electrodes were tested for simultaneous determination of Pb(II), Cd(II) and Zn(II) in an aqueous solution on in-situ formed bismuth film by square wave voltammetry (SWV). The dependence of the stripping responses on the concentration of target metals was linear in the range from 1 × 10-8 to 9 × 10-8 mol/L. The effect of activation of the PPF surface by argon plasma on analytical performance of bismuth film electrode (BiFE) on PPF support was also investigated.

Effect of Post-Annealing Treatment on the Structure and Luminescence Properties of AIN:Tb3+ Thin Films Prepared by Radio Frequency Magnetron Sputtering

Terbium-doped aluminum nitride thin films have been deposited by radio frequency magnetron sputtering. The influence of annealing treatments on structural, morphological and luminescence properties of the films is examined with the aim to optimize post-deposition annealing conditions. Temperatures starting from 500 up to 1000°C using two annealing techniques were investigated: rapid thermal processing and quartz tube furnace. X-ray diffraction analysis revealed the formation of aluminum oxide and aluminum oxynitride phases at temperatures higher than 750°C. The oxygen content in the surface layer was measured with energy dispersive X-ray. The terbium emission was obtained after excitation either by photons or electrons. The films treated with rapid thermal processing at 750°C resulted in the highest emission.

High dose high temperature ion implantation of Ge into 4H-SiC

A box like Ge distribution was formed by ion implantation at 600°C. The Ge concentration was varied from 1 to 20 %. The TEM investigations revealed an increasing damage formation with increasing implantation dose. No polytype inclusions were observed in the implanted regions. A detailed analysis showed different types of lattice distortion identified as insertion stacking faults. The lattice site location analysis by “atomic location by channelling enhanced microanalysis” revealed that the implanted Ge is mainly located at interstitial positions.

Ge Addition during 4H-SiC Epitaxial Growth by CVD: Mechanism of Incorporation

In this paper, we will describe a detailed experimental study on the behavior of Ge incorporation into 4H-SiC during its homoepitaxial growth by CVD. Addition of GeH4 precursor to the standard chemical system SiH4 + C3H8 was investigated as a function of various growth parameters. Its effect on surface morphology, layer quality and purity was followed. All these results will allow proposing an exhaustive picture of Ge incorporation mechanism into 4H-SiC with the possible benefits of such impurity incorporation in the silicon carbide lattice.

Structure and Lattice Location of Ge Implanted 4H-SiC

Pseudomorphic 4H-(Si1-xC1-y)Gex+y solid solutions were formed by ion implantation at 600°C and rapid thermal annealing at implanted Ge concentrations below 10%. At higher implantation doses followed by annealing 3C-SiC inclusion and SiGe precipitates are formed. Transmission electron microscopy investigations accompanied with “atomic location by channeling enhanced microanalysis” of the annealed samples revealed an increasing incorporation of Ge on Si lattice sites.

Atomic Layer Epitaxy of (Si1-xC1-y)Gex+y Layers on 4H-SiC

3C-(Si1-xC1-y)Gex+y ternary alloys were grown on 8.5° off axis 4H-SiC substrates by solid source molecular beam epitaxy in a temperature range between 750°C and 950°C. Energy dispersive X-ray (EDX) analysis revealed a decrease of the Ge incorporation versus substrate temperature. This effect is due to the fixed Si/Ge ratio during the epitaxial growth. The Ge distribution within the grown epitaxial layers was found to be nearly homogeneous. The investigations by atomic location by channeling enhanced microanalysis allowed the conclusion that Ge is located mainly at Si lattice sites.