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Natalie Vanden Bon,1 Bart van Grinsven,2 Mohammed Sharif Murib,2 Weng Siang Yeap,2 Ken Haenen,2,3 Ward De Ceuninck,2,3 Patrick Wagner,2,3 Marcel Ameloot,1 Veronique Vermeeren,1 Luc Michiels11Biomedical Research Institute, Hasselt University, Diepenbeek, Belgium; 2Institute for Materials Research, Hasselt University, Diepenbeek, Belgium; 3IMOMEC, Diepenbeek, BelgiumAbstract: Conventional neonatal diagnosis of phenylketonuria is based on the presence of abnormal levels of phenylalanine in the blood. However, for carrier detection and prenatal diagnosis, direct detection of disease-correlated mutations is needed. To speed up and simplify mutation screening in genes, new technologies are developed. In this study, a heat-transfer method is evaluated as a mutation-detection technology in entire exons of the phenylalanine hydroxylase (PAH) gene. This method is based on the change in heat-transfer resistance (Rth) upon thermal denaturation of dsDNA (double-stranded DNA) on nanocrystalline diamond. First, ssDNA (single-stranded DNA) fragments that span the size range of the PAH exons were successfully immobilized on nanocrystalline diamond. Next, it was studied whether an Rth change could be observed during the thermal denaturation of these DNA fragments after hybridization to their complementary counterpart. A clear Rth shift during the denaturation of exon 5, exon 9, and exon 12 dsDNA was observed, corresponding to lengths of up to 123 bp. Finally, Rth was shown to detect prevalent single-nucleotide polymorphisms, c.473G>A (R158Q), c.932T>C (p.L311P), and c.1222C>T (R408W), correlated with phenylketonuria, displaying an effect related to the different melting temperatures of homoduplexes and heteroduplexes.Keywords: mutation detection, heat-transfer resistance, melting temperature, nanocrystalline diamond, persistence length

A high-temperature procedure to hydrogenate diamond films using molecular hydrogen at atmospheric pressure was explored. Undoped and doped chemical vapour deposited (CVD) polycrystalline diamond films were treated according to our annealing method using a H2 gas flow down to ∼50 ml/min (STP) at ∼850 °C. The films were extensively evaluated by surface wettability, electron affinity, elemental composition, photoconductivity, and redox studies. In addition, electrografting experiments were performed. The surface characteristics as well as the optoelectronic and redox properties of the annealed films were found to be very similar to hydrogen plasma-treated films. Moreover, the presented method is compatible with atmospheric pressure and provides a low-cost solution to hydrogenate CVD diamond, which makes it interesting for industrial applications. The plausible mechanism for the hydrogen termination of CVD diamond films is based on the formation of surface carbon dangling bonds and carbon-carbon unsaturated bonds at the applied tempera-ture, which react with molecular hydrogen to produce a hydrogen-terminated surface. [ABSTRACT FROM AUTHOR]

Time-of-Flight (ToF) experiments were carried out to study the electrical transport and charge trapping properties of oxidized freestanding single crystalline (100) CVD diamond crystals. It is shown that the diamond surface and properties of the electrical contacts are of extreme importance, influencing measured charge carrier mobility values. While sputtered Al contacts yield textbook ToF spectra and electron mobilities μe exceeding 1860 cm2/Vs, thermally deposited contacts suffer from enhanced trapping. We propose a model in which the observed polarization effects can be explained by charge transfer to oxygen-related surface states, which interact with surface adsorbates, according to the well-known transfer-doping model. [ABSTRACT FROM AUTHOR]

The systematics of the suppression of superconductivity with increasing magnetic field in boron-doped nanocrystalline chemical vapor deposition diamond is studied in a broad temperature range. At the temperature of TS0 which is above the critical temperature, a plateau is observed in the resistivity versus temperature curve ρ(T) taken at zero magnetic field. When a magnetic field of B=BSN(N=1,2,...,5) is applied, the plateau moves to low temperature with the thermoresistivity maximum located at TSN (N=1,2,...,5). The ρ(B) curves, measured at different temperatures around TSN, intersect in the ρ-B plane at the field of B=BSN. By tuning BSN from 0 to 5 T, a series of plateaus in the ρ-T plane and the corresponding intersections in the ρ-B plane are observed. The intersections quadratically chain up in the ρ-B plane, separating the superconducting from the insulating region. The thermoresistivity maxima exponentially group up in the ρ-T plane, thus defining a phase fluctuation zone. The phase boundary, composed of the intersections and separating the superconducting states from the insulating state, is shown to be a generic consequence of granularity. [ABSTRACT FROM AUTHOR]

In this work, we investigate the stress developed in phosphorus-doped layers grown on (110)-textured polycrystalline diamond templates. To that end, we follow the shifts of the diamond Raman diffusion and the exciton recombination energies by Raman and cathodoluminescence spectroscopies, respectively. With each approach, a high tensile strain of several gigapascal is evidenced. Moreover, Raman mapping performed in cross section shows (i) at the grain boundaries, a strain in tension that propagates along the growth direction from the template to the deposited layer and (ii) at the center of each grain, a tensile strain of the phosphorus-doped layer with respect to the underlying undoped grain. Concerning the second, we observe also an increase in strain effects at high phosphorus incorporation, together with a structural degradation. The possible origins of such high lattice deformation of phosphorus-doped layers are discussed. [ABSTRACT FROM AUTHOR]

We report on the observation of a negative magnetoresistance (NMR) regime in boron-doped nanocrystalline diamond films at low temperatures. A comparative analysis of our experimental results and those reported for systems composed of superconducting granules embedded in an insulating matrix (also referred as granular films) suggest the presence of superconducting regions inside the insulating films as causing the NMR. By considering the latter scenario, the experimental observations are explained by modeling the systems as consisting of a distribution of superconducting granules whose global properties are tuned by the intergrain distance. [ABSTRACT FROM AUTHOR]