This review paper illustrates the main normal and superconducting state properties of magnesium diboride, a material known since the early 1950s but only recently discovered to be superconductive at a remarkably high critical temperature Tc = 40 K for a binary compound. What makes MgB2 so special? Its high Tc, simple crystal structure, large coherence lengths, high critical current densities and fields, and transparency of grain boundaries to current promise that MgB2 will be a good material for both large-scale applications and electronic devices. During the last seven months, MgB2 has been fabricated in various forms: bulk, single crystals, thin films, tapes and wires. The largest critical current densities, greater than 10 MA cm−2, and critical fields, 40 T, are achieved for thin films. The anisotropy ratio inferred from upper critical field measurements is yet to be resolved as a wide range of values have been reported, γ = 1.2–9. Also, there is no consensus on the existence of a single anisotropic or double energy gap. One central issue is whether or not MgB2 represents a new class of superconductors, which is the tip of an iceberg awaiting to be discovered. To date MgB2 holds the record for the highest Tc among simple binary compounds. However, the discovery of superconductivity in MgB2 revived the interest in non-oxides and initiated a search for superconductivity in related materialss; several compounds have since been announced to be superconductive: TaB2, BeB2.75, C–S composites, and the elemental B under pressure.

https://iopscience.iop.org/article/10.1088/0953-2048/14/11/201/pdf

Review of the superconducting properties of MgB2

Characterization of amorphous and nanocrystalline carbon films

Diamond exhibits several special properties, for example good biocompatibility and a large electrochemical potential window, that make it particularly suitable for biofunctionalization and biosensing. Here we show that proteins can be attached covalently to nanocrystalline diamond thin films. Moreover, we show that, although the biomolecules are immobilized at the surface, they are still fully functional and active. Hydrogen-terminated nanocrystalline diamond films were modified by using a photochemical process to generate a surface layer of amino groups, to which proteins were covalently attached. We used green fluorescent protein to reveal the successful coupling directly. After functionalization of nanocrystalline diamond electrodes with the enzyme catalase, a direct electron transfer between the enzyme's redox centre and the diamond electrode was detected. Moreover, the modified electrode was found to be sensitive to hydrogen peroxide. Because of its dual role as a substrate for biofunctionalization and as an electrode, nanocrystalline diamond is a very promising candidate for future biosensor applications.

Protein-modified nanocrystalline diamond thin films for biosensor applications

Surface composition analysis by low-energy ion scattering

A new fabrication method to produce homogeneously fluorescent nanodiamonds with high yields is described. The powder obtained by high energy ball milling of fluorescent high pressure, high temperature diamond microcrystals was converted in a pure concentrated aqueous colloidal dispersion of highly crystalline ultrasmall nanoparticles with a mean size less than or equal to 10 nm. The whole fabrication yield of colloidal quasi-spherical nanodiamonds was several orders of magnitude higher than those previously reported starting from microdiamonds. The results open up avenues for the industrial cost-effective production of fluorescent nanodiamonds with well-controlled properties.

https://iopscience.iop.org/article/10.1088/0957-4484/20/23/235602/pdf

High yield fabrication of fluorescent nanodiamonds

Thermal oxidizing treatments of hydrogenated diamond surfaces have been performed in an O2 environment. Chemisorption of oxygen on diamond surfaces has been investigated by diffuse reflectance Fourier-transform infrared (FTIR), temperature-programmed desorption (TPD), temperature-programmed reaction (TPR) and thermogravimetry (TG). Oxidation of the hydrogenated diamond occurred above 300 °C and diamond started to burn out above 480 °C in 20% O2. Diffuse reflectance FTIR spectra indicated that the oxidation gave species containing CO and C—O—C structures on the diamond surface above 300 °C. The structures of the chemisorbed species changed with the oxidation temperature. The maximum coverage of oxygen was obtained between 480 and 500 °C. TPD spectra of oxidized diamond indicated that the oxygen-containing species were desorbed as CO and CO2 above 480 °C. This paper deals with the mechanistic considerations for the oxidation of diamond surfaces.

Vapour-phase oxidation of diamond surfaces in O2 studied by diffuse reflectance Fourier-transform infrared and temperture-programmed desorption spectroscopy

Kazuo Yamamoto

Papers

Vapour-phase oxidation of diamond surfaces in O2 studied by diffuse reflectance Fourier-transform infrared and temperture-programmed desorption spectroscopy

Chemical modification of diamond surfaces using a chlorinated surface as an intermediate state

Surface vibrational studies of CVD diamond

Direct interaction of elemental fluorine with diamond surfaces

Difference in the outermost layer between TaB 2 ( 0001 ) and HfB 2 ( 0001 )