Weak localization in ultrananocrystalline diamond

In this letter we present results of magnetotransport measurements, carried out on heavily nitrogen-doped ultrananocrystalline diamond films, prepared by plasma-enhanced chemical vapor deposition. This material having at room temperature appreciably high electric conductivity ( ∼ 4200 S m−1) revealed surprisingly at Kelvin temperatures a giant negative magnetoresistance reaching up to 22% at 1.28 K and at 8 T. The analysis of experimental data has borne evidence of the fact that the transport in this subsystem has a character of low-dimensional disordered metal and it is controlled by quantum interference effects of electrons resulting in their weak localization

Real-Time Monitoring of Aptamer Functionalization and Detection of Ara H1 by Electrochemical Impedance Spectroscopy and Dissipation-Mode Quartz Crystal Microbalance

Peanut allergy, the most common cause of fatal-food-related anaphylaxis, is a lifelong disorder and the only existing therapy is avoidance of allergen-containing food. Detection of Ara h 1, the most important peanut allergen, is commonly performed by immunoassay techniques relying on the use of expensive and relatively unstable antibodies. Aptamers can overcome these drawbacks and offer a great potential for the development of reliable biosensors. Therefore, we will present a novel aptamer-based sensor for the label-free detection of Ara h 1. Amino (NH2)-terminated Ara h 1 aptamers were covalently attached to carboxylated gold surfaces employing carbodiimide chemistry. This functionalization procedure was followed in real time by electrochemical impedance spectroscopy and quartz crystal microbalance with dissipation monitoring. Subsequently, the functionalized surfaces were exposed to Ara h 1 solutions in TGK buffer. By combining the two techniques, we can measure in a wide concentration regime varying from the low nanomolar range (1-15 nM) via electrochemical impedance spectroscopy to the higher concentrations (25-250 nM) by microgravimetric detection. In summary, a fast, low-cost and sensitive sensor platform for Ara h 1 detection has been developed, which can be operated as a ‘stand-alone device’, making it well suited for applications such as the screening of trace allergens

The preparation, characterization and tribological properties of TA-C : H deposited using an electron cyclotron wave resonance plasma beam source

A compact electron cyclotron wave resonance (ECWR) source has been developed for the high rate deposition of hydrogenated tetrahedral amorphous carbon (ta-C:H). The ECWR provides growth rates of up to 900 Å/min over a 4″ diameter and an independent control of the deposition rate and ion energy. The ta-C:H was deposited using acetylene as the source gas and was characterized in terms of its sp3 content, mass density, intrinsic stress, hydrogen content, C-H bonding, Raman spectra, optical gap, surface roughness and friction coefficient. The results obtained indicated that the film properties were maximized at an ion energy of approximately 167 eV, corresponding to an energy per daughter carbon ion of 76 eV. The relationship between the incident ion energy and film densification was also explained in terms of the subsurface implantation of carbon ions into the growing film

Compositional and electrical characterisation of the hydrogen-oxygen terminated diamond (100) surface

In this work (100) diamond films are hydrogenated using a conventional MWPE-CVD (microwave plasma enhanced chem. vapor deposition) reactor contg. a H2 or a H2/O2 mixt. For the latter, XPS (XPS) expts. show an increased presence of oxygen at the (sub)-surface. Contrary to pure H2-plasma treated samples, H2/O2-treated layers still posses enough cond. to enable STS (Scanning Tunneling Spectroscopy) investigations to be carried out after an annealing at 410 DegC in UHV (Ultra High Vacuum). Evidence for surface resonance states is detected, yielding a possible explanation for the measured cond. UPS (UPS) data point to a neg. electron affinity of -0.3 eV for the H2/O2-treated layers. [on SciFinder (R)

The role of (sub)-surface oxygen on the surface electronic structure of hydrogen terminated (100) CVD diamond

In this work, scanning tunnelling microscopy (STM) and scanning tunnelling spectroscopy (STS) were applied to investigate the surface morphol. and the surface electronic structure of plasma-treated (100)-oriented CVD diamond films. These films were hydrogenated using a conventional MWPE-CVD (microwave plasma enhanced chem. vapor deposition) reactor contg. a H2 or a H2/O2 mixt. A comparison is made between (100)-oriented CVD diamond films hydrogenated with and without a small addn. of oxygen (1%). XPS and UPS (UPS) measurements point to the presence of O-atoms at the (sub)-surface of the diamond film. The measured cond. is significantly different for the two processes of hydrogenation. Annealing expts. point out that the samples, which were terminated using the H2/O2 mixt. are still conductive enough after annealing at 410 DegC to enable STM expts. Here, we discuss the mechanism for STM imaging of H2/O2 treated diamond films, assocd. with surface states induced by the oxygen incorporation. [on SciFinder (R)