A graphene field-effect transistor as a molecule-specific probe of DNA nucleobases

© 2015 Macmillan Publishers Limited. All rights reserved. Fast and reliable DNA sequencing is a long-standing target in biomedical research. Recent advances in graphene-based electrical sensors have demonstrated their unprecedented sensitivity to adsorbed molecules, which holds great promise for label-free DNA sequencing technology. To date, the proposed sequencing approaches rely on the ability of graphene electric devices to probe molecular-specific interactions with a graphene surface. Here we experimentally demonstrate the use of graphene field-effect transistors (GFETs) as probes of the presence of a layer of individual DNA nucleobases adsorbed on the graphene surface. We show that GFETs are able to measure distinct coverage-dependent conductance signatures upon adsorption of the four different DNA nucleobases; a result that can be attributed to the formation of an interface dipole field. Comparison between experimental GFET results and synchrotron-based material analysis allowed prediction of the ultimate device sensitivity, and assessment of the feasibility of single nucleobase sensing with graphene

Ion beam induced charge and numerical modeling study of novel detector devices for single ion implantation

C1 - Journal Articles Referee

Controlled shallow single-ion implantation in silicon using an active substrate for sub-20-keV ions

C1 - Journal Articles Referee

Palladium forms Ohmic contact on hydrogen-terminated diamond down to 4K

A hydrogen-terminated diamond (H-terminated diamond) surface supports a two-dimensional (2D) p-type surface conductivity when exposed to the atmosphere, as a result of the surface transfer doping process. The formation of reliable Ohmic contacts that persist to cryogenic temperature is essential for the exploration of quantum transport in the diamond 2D conducting channel. Herein, the contact properties of Pd on H-terminated diamond have been fully investigated down to 4 K using transmission line method measurements. Pd is shown to form an Ohmic contact on H-terminated diamond with linear I-V characteristics and low specific contact resistance in the range of (8.4 ± 1) ×10-4 ω·cm2 to (1.3 ± 0.2) ×10-3 ω·cm2 for the temperature range of 300 K-4 K. This is in stark contrast to reference devices with Au/Pt/Ti contacts, which exhibit a significant temperature dependence and non-Ohmic behavior at low temperature. Using 2D thermionic emission theory, a negative Schottky barrier height (SBH), - 23 ± 1 meV, between Pd and H-terminated diamond has been determined, in comparison to a positive SBH of 42 ± 1 meV for the Au/Pt/Ti/H-terminated diamond interface. These results show that Pd serves as an excellent candidate for forming reliable Ohmic contacts on H-terminated diamond for enabling precise electrical transport measurements at cryogenic temperature.</p

Evidence for Primal sp(2) Defects at the Diamond Surface: Candidates for Electron Trapping and Noise Sources

Many advanced applications of diamond materials are now being limited by unknown surface defects, including in the fields of high power/frequency electronics and quantum computing and quantum sensing. Of acute interest to diamond researchers worldwide is the loss of quantum coherence in near-surface nitrogen-vacancy (NV) centers and the generation of associated magnetic noise at the diamond surface. Here for the first time is presented the observation of a family of primal diamond surface defects, which is suggested as the leading cause of band-bending and Fermi-pinning phenomena in diamond devices. A combination of density functional theory and synchrotron-based X-ray absorption spectroscopy is used to show that these defects introduce low-lying electronic trap states. The effect of these states is modeled on band-bending into the diamond bulk and it is shown that the properties of the important NV defect centers are affected by these defects. Due to the paramount importance of near-surface NV center properties in a growing number of fields, the density of these defects is further quantified at the surface of a variety of differently-treated device surfaces, consistent with best-practice processing techniques in the literature. The identification and characterization of these defects has wide-ranging implications for diamond devices across many fields

The knowledge spillover theory of entrepreneurship

Opportunity, Knowledge, Entrepreneurship, Endogenous growth, Start-ups, New product innovation, J24, L26, M13, O3,