http://experimentationlab.berkeley.edu/sites/default/files/AFMImages/butt_AFM.pdf

Force measurements with the atomic force microscope: Technique, interpretation and applications

Shape-engineerable and highly densely packed single-walled carbon nanotubes and their application as super-capacitor electrodes

/pdf/shape-engineerable-and-highly-densely-packed-single-walled-slt8pdoyvz.pdf

J. Y. Tsao,* S. Chowdhury, M. A. Hollis,* D. Jena, N. M. Johnson, K. A. Jones, R. J. Kaplar,* S. Rajan, C. G. Van de Walle, E. Bellotti, C. L. Chua, R. Collazo, M. E. Coltrin, J. A. Cooper, K. R. Evans, S. Graham, T. A. Grotjohn, E. R. Heller, M. Higashiwaki, M. S. Islam, P. W. Juodawlkis, M. A. Khan, A. D. Koehler, J. H. Leach, U. K. Mishra, R. J. Nemanich, R. C. N. Pilawa-Podgurski, J. B. Shealy, Z. Sitar, M. J. Tadjer, A. F. Witulski, M. Wraback, and J. A. Simmons

/pdf/ultrawide-bandgap-semiconductors-research-opportunities-and-49ev1zu2ym.pdf

Ultrawide-Bandgap Semiconductors: Research Opportunities and Challenges

A huge enhancement of the superconducting transition temperature Tc was observed in a tetragonal FeSe superconductor under high pressure. The onset temperature was as high as 27K at 1.48GPa and the pressure coefficient showed an extremely high value of 9.1K∕GPa. The upper critical field Hc2 was estimated to be ∼72T at 1.48GPa. Because of the high Hc2, the FeSe system can be applied to superconducting wire rods.

Superconductivity at 27K in tetragonal FeSe under high pressure

We introduce a technique based on the spatial localization of electron and phonon Wannier functions to perform first-principles calculations of the electron-phonon interaction with an ultradense sampling of the Brillouin zone. After developing the basic theory, we describe the practical implementation within a density-functional framework. The proposed method is illustrated by considering a virtual crystal model of boron-doped diamond. For this test case, we first discuss the spatial localization of the electron-phonon matrix element in the Wannier representation. Then, we assess the accuracy of the Wannier-Fourier interpolation in momentum space. Finally, we study the convergence of the electron-phonon self-energies with the sampling of the Brillouin zone by calculating the electron and phonon linewidths, the Eliashberg spectral function, and the mass enhancement parameter of B-doped diamond. We show that more than ${10}^{5}$ points in the irreducible wedge of the Brillouin zone are needed to achieve convergence.

Electron-phonon interaction using Wannier functions

We report unambiguous evidence for superconductivity in a heavily boron-doped diamond thin film grown by microwave plasma-assisted chemical vapor deposition (MPCVD). An advantage of the MPCVD-deposited diamond is that it can contain boron at high concentration, especially in (111)-oriented films. Superconducting transition temperatures are determined by transport measurements to be 7.4 K for TC onset and 4.2 K for zero resistance. The upper critical field is estimated to be 7 T. Magnetization as a function of magnetic fields shows typical type-II superconducting properties.

Superconductivity in diamond thin films well above liquid helium temperature

Diamond has always been adored as a jewel. Even more fascinating is its outstanding physical properties; it is the hardest material known in the world with the highest thermal conductivity. Meanwhile, when we turn to its electrical properties, diamond is a rather featureless electrical insulator. However, with boron doping, it becomes a p-type semiconductor, with boron acting as a charge acceptor. Therefore the recent news of superconductivity in heavily boron-doped diamond synthesized by high pressure sintering was received with considerable surprise. Opening up new possibilities for diamond-based electrical devices, a systematic investigation of these phenomena clearly needs to be achieved. Here we show unambiguous evidence of superconductivity in a diamond thin film deposited by a chemical vapor deposition (CVD) method. Furthermore the onset of the superconducting transition is found to be 7.4K, which is higher than the reported value in ref(7) and well above helium liquid temperature. This finding establishes the superconductivity to be a universal property of boron-doped diamond, demonstrating that device application is indeed a feasible challenge.

Superconductivity in CVD Diamond Thin Film Well-Above Liquid Helium Temperature

High temperature application of diamond power device

Diamond field effect transistors have operated in electrolyte solution for the first time Since the hydrogen-terminated diamond surfaces are stable enough for the use as an electrochemical electrode, the diamond surface channels are exposed to the electrolyte in the transistor structure A perfect pinch-off and saturated current-voltage characteristics have been obtained for bias voltages within the potential window The threshold voltages are almost constant in electrolytes with different pH values of 7-13, indicating pH insensitiveness of the hydrogen-terminated diamond surface Based on this pH insensitive surface, ion selective regions can be fabricated to form transistor-based biosensors

Electrolyte-Solution-Gate FETs Using Diamond Surface for Biocompatible Ion Sensors

The current-voltage characteristics of non-punch-through-type diamond Schottky barrier diodes (SBDs) are analyzed by using thermionic and thermionic-field emission (TFE) models. Diamond SBD with defects such as nonepitaxial crystallites (NCs) shows shunt path conductance both under forward and reverse bias conditions. However, SBD without NCs shows a low reverse leakage current density of less than 1×10−11A∕cm2, which is more than 12 orders of magnitude smaller than the forward current density. From the fitting of the reverse leakage current of SBD without NCs, TFE current dominates when the reverse electric field is larger than 1.2MV∕cm and its current density value reaches 10−6A∕cm2 even at 1.6MV∕cm, which is lower than the avalanche limit.

Hitoshi Umezawa

Papers

Superconductivity in diamond thin films well above liquid helium temperature

Superconductivity in CVD Diamond Thin Film Well-Above Liquid Helium Temperature

High temperature application of diamond power device

Electrolyte-Solution-Gate FETs Using Diamond Surface for Biocompatible Ion Sensors

Leakage current analysis of diamond Schottky barrier diode