Electric-field noise from the surfaces of ion-trap electrodes couples to the ion’s charge causing heating of the ion’s motional modes. This heating limits the fidelity of quantum gates implemented in quantum information processing experiments. The exact mechanism that gives rise to electric-field noise from surfaces is not well-understood and remains an active area of research. In this work, we detail experiments intended to measure ion motional heating rates with exchangeable surfaces positioned in close proximity to the ion, as a sensor to electric-field noise. We have prepared samples with various surface conditions, characterized in situ with scanned probe microscopy and electron spectroscopy, ranging in degrees of cleanliness and structural order. The heating-rate data, however, show no significant differences between the disparate surfaces that were probed. These results suggest that the driving mechanism for electric-field noise from surfaces is due to more than just thermal excitations alone.

Dense, controlled-impedance, superconducting cables with small cross-sections are desirable, especially for quantum computing applications. In this study, superconductivity properties, rf microwave response and mechanical reliability performance of embedded Nb dc cables and Nb microstrip transmission line resonators with different thicknesses of polyimide PI-2611 encapsulation layers (0, 4 and 8 μm) have been investigated. Critical temperature (Tc) and critical current (Ic) of embedded Nb dc cables are ∼ 8.2 K and ∼ 0.2 A, respectively. Embedded Nb resonators yield high loaded quality factor (QL), with values as high as 14481 at ∼ 1.2 K and at a fundamental resonance of ∼ 2 GHz. From mechanical fatigue testing, we have observed that a polyimide encapsulation layer can effectively enhance the mechanical reliability of superconducting Nb flexible cables.

The use of ceria abrasives in the chemical mechanical polishing (CMP) of glass allows us to prepare extremely smooth surfaces because it aides both the chemical and mechanical aspects of the polishing process. The mechanism of CMP has remained vague, but the redox of Ce4+/Ce3+ would play a major role for the formation of hydration layer by the chemical factors of CMP. This redox accompanies the process of the charge transfer at glass/slurry interface. Electron charge carrier would be important role in chemical polishing if the redox reaction occurs during polishing. We then prepared the polishing model that it is possible to estimate slurry resistivity and the interfacial area specific resistance (ASR). The effects of abrasive compositions and slurry solution on chemical factor of CMP were investigated to clarify CMP mechanism. The hydration layer forms as a result of the shear stress during polishing but is independent of polishing loads. The amount of hydration layer as well as removal rate was increasing with increasing lanthanum concentration dissolved in ceria lattice. Small amount addition of NH4NO3 increase electron charge carrier density in slurry and improves removal rate, but excess addition inhibited hydration reaction by steric hindrance.

The union of the unique diamond properties with steel (most common substrate material) provides a new solution for machine parts under critical mechanical conditions and severe environmental. However, CVD diamond coating directly on steel comes with several issues. The fundamental reasons for the lack of adhesion are an iron catalytic effect, the high carbon solubility in iron and high mismatch in thermal expansion coefficient of diamond and steel. The use of interlayer may solve these issues acting as a diffusion barrier, for both iron and carbon, and match thermal expansion coefficients. Several articles describe the PVD deposition or electroplated interlayer. In the present study, the diamond film coated steel with an intermediate barrier deposited by laser cladding process. In this novel technique, laser irradiation melts the powder (preplaced) and the substrate surface to create the coating on a steel substrate. We used the SiC/Ti and SiC/Cu powder mixtures to create the intermediate barrier. Diamond film deposition was carried out in an HFCVD reactor (Hot Filament Chemical Vapor Deposition). The samples characterization included X-ray Diffraction (XRD); Field Emission Gun - Scanning Electron Microscopy (FEG-SEM) and Raman Scattering Spectroscopy (RSS). Results showed that laser incidence dissociated partially the SiC powder, forming FeSi, Cu3Si phases. Further, the composite layer assisted the high thermal stress relief in steel/diamond interface.

Polyaniline (PAni)/B-doped diamond/carbon fiber (CF) ternary composites were produced and characterized, aiming their application as electrodes for supercapacitor device. In order to optimize the composite properties, structurally different CF substrates, heat treated at 1000 and 2000°C, were used to grown diamond films. Moreover, the diamond films were grown on CF in two different morphologies, boron doped micro and nanocrystalline diamond (BDD/BDND), by Hot Filament Chemical Vapor Deposition (HFCVD) technique. FEG-SEM images showed that PAni covered and enwrapped the diamond/CF surfaces, producing tridimensional electrodes. Raman spectra confirmed the PAni formation for all composites. Electrochemical characterizations indicated that the PAni/BDD/CF2000 composite has the highest current density and capacitance response among the studied composites combinations. In addition, it showed the most reversible oxidation and reduction processes, the greatest charge storage capacity as well as the lowest charge transfer resistance.

The parameter optimizations of square-wave anodic stripping voltammetry using boron doped diamond (BDD) electrodes with different doping levels for cadmium detection were studied. The optimized relation among the peak current with the pulse frequency, the amplitude, and the potential increment for highly (1019 cm-3) and heavily BDD (1021 cm-3) electrodes was considered. The peak currents were measured around -0.75 V vs. Ag/AgCl for Cd2+ concentration ranged from 1 to 20 ppb. Both BDD films provided detection limits lower than 5 ppb showing that these electrodes are suitable to use in a mercury-free method to determine cadmium trace levels in water.

Diamond is a promising wide band-gap semiconductor material for use in devices; therefore a thorough understanding of the surface electronic structure is important. The Kelvin Probe (KP), Surface Photovoltage / Surface Photovoltage Spectroscopy (SPV/SPS) and Ambient Pressure Photoemission Spectroscopy (APS) techniques are commonly applied to traditional and organic semiconductor materials. The application of these techniques to synthetic and natural diamond samples provides some challenges: surface charge on the samples and atypical capacitive interaction with the KP tip. In this study, measurements using a combination of KP, SPV/SPS and APS techniques are taken of samples of natural and synthetic diamond samples to investigate their surface electronic structure and compare their different properties. These techniques are all non-contact and non-destructive. The Fermi Level position of the diamond samples was found to vary, typically between 4.3 – 4.9 eV, depending on the light illumination. For example, when a natural diamond sample was illuminated with 400 nm light from a 150W Quartz Tungsten Halogen light source, there was a surface photovoltage response of ∼250 mV. The oxygen terminated synthetic diamond sample required near continuous illumination at low visible wavelengths in order to retain sufficient conductivity to allow measurement with the Kelvin Probe. By contrast, the natural diamond samples measured showed good conductivity in the layers underneath the top surface. In summary, the KP, SPV/SPS and APS measurement techniques provided some interesting information on the diamond samples and an initial investigation of their surface electronic states is performed.

Charge carrier trapping in diamond surface conduction field effect transistors (FETs) has been analyzed. For these devices two methods were used to obtain a negative electron affinity diamond surface; either plasma hydrogenation or annealing in an H2 environment. In both cases the Al2O3 gate dielectric can trap both electrons and holes in deep energy levels with emission timescales of seconds, while the diamond – Al2O3 interface traps exhibit much shorter time scales in the microsecond range. Capacitance-Voltage (CV) analysis indicates that these interface traps exhibit acceptor-like characteristics. Correlation with CV based free hole density measurements indicates that the conductance based interface trap analysis provides a method to quantify surface characteristics that lead to surface conduction in hydrogenated diamond where atmospheric adsorbates provide the acceptor states for transfer doping of the surface.

A systematic study was performed concerning the production, characterization, and application of BDD and BDND films grown on Ti substrate to degrade brilliant green dye using an electrochemical flow reactor. Films were grown in a hot filament chemical vapour deposition (HFCVD) reactor using H2/CH4 (BDD) and H2/CH4/Ar (BDND) gas mixtures. Boron doping was performed by dissolution of B2O3 in methanol in the appropriate B/C ratio to obtain good conductive electrodes. The electrolysis was carried out using BDD/Ti and BDND/Ti as anode material analyzing the influence of different current densities and flow rates. During the electrolysis, aliquots of the treated solution were analyzed by UV-Vis and Total Organic Carbon (TOC) measurements. The electrode efficiencies were compared considering the color removal as well as the TOC mineralization in the end of each electrolysis. The absorption bands intensity from UV/Vis spectra clearly decreased up to their completely vanishing at current density of 100 mA/cm2 for both electrodes. These results were corroborated by TOC measurements where 50% of the organic material was removed.

Microelectrodes have attracted great interest for electroanalysis because of their unique properties, such as nonlinear diffusion, increased rate of mass transport and reduced capacitance, which allows a fast response. In this work, we created a porous nanocomposite of boron doped diamond (BDD) deposited on carbon nanotubes – reduced graphene oxide (CNTs – RGO) by Hot Filament Chemical Vapor Deposition (HFCVD) technique. The resulting material yielded porous BDD microelectrodes. On the first step, we have grown the CNTs on carbon fiber (CF) surface by Thermal CVD in a tubular reactor. Camphor solution and Fe-Co were carbon and catalyst source, respectively. For exfoliation, CNTs were treated by hydrogen plasma and oxygen plasma. We applied a seeding solution containing nanodiamond dispersed in KCl aqueous solution. Diamond nanoparticles interact with oxygen-containing groups on CNTs, promoting an efficient seeding. We deposited BDD films in an HFCVD reactor using methane/hydrogen gas mixtures. For doping, a partial hydrogen flow bubbled in a closed vessel containing a solution of boron oxide dissolved in methanol. The microelectrodes were characterized by Raman Scattering Spectroscopy, Scanning Electron Microscopy with Field Emission Gun and Cyclic Voltammetry. The crystalline quality of CNTs and BDD doping level were studied by Raman analysis. SEM micrographs showed that nanocomposite presented high porosity. Electrochemical analysis showed that the deposition of BDD on CNTs-RGO increased the electrochemical response of the microelectrode. Besides, this electrode presented a low capacitive current in comparison with BDD grown on flat substrates. Further, the porous BDD nanocomposite showed itself to be promising in electroanalysis.