Ultralow-power cryogenic thermometry based on optical-transition broadening of a two-level system in diamond

Cryogenic temperatures are the prerequisite for many advanced scientific applications and technologies. The accurate determination of temperature in this range and at the submicrometer scale is, however, nontrivial. This is due to the fact that temperature reading in cryogenic conditions can be inaccurate due to optically induced heating. Here, we present an ultralow power, optical thermometry technique that operates at cryogenic temperatures. The technique exploits the temperature dependent linewidth broadening measured by resonant photoluminescence of a two level system, a germanium vacancy color center in a nanodiamond host. The proposed technique achieves a relative sensitivity of 20% 1/K, at 5 K. This is higher than any other all optical nanothermometry method. Additionally, it achieves such sensitivities while employing excitation powers of just a few tens of nanowatts, several orders of magnitude lower than other traditional optical thermometry protocols. To showcase the performance of the method, we demonstrate its ability to accurately read out local differences in temperatures at various target locations of a custom-made microcircuit. Our work is a definite step towards the advancement of nanoscale optical thermometry at cryogenic temperatures

High-pressure high-temperature synthesis and structure of α-tetragonal boron

ERRATUMThis is an Erratum for the article 2011 Sci. Technol. Adv. Mater. 12 055009The publisher regrets that there is a typographical error on page 2 of this article. The fourth sentence of section 3 should read as follows:The lines characteristic of B–H–B (1700–2000 cm-1) and B–H (2550–2650 cm-1) bonds of decaborane were not found in the Raman spectra of the crystals (figure 3) that confirms the complete decomposition of decaborane [19, 20]

High-Pressure Synthesis of Nanodiamonds from Adamantane Myth or Reality?

International audienceThe high-pressure and high-temperature technique is the most promising for mass production of ultra-small diamond nanoparticles of perfect structure. In the present work, this technique was successfully used for the synthesis of nanodiamonds from their molecular analogue, adamantane. A minimum size of synthesized diamond crystals of about 3nm was reached. It was found that the decisive condition for the stable production of nanodiamonds from adamantane under pressures below the limit value required for direct conversion of graphite into diamond is the minimization of the carbon sample loss during the synthesis. The possibility of doping such diamonds with optically active impurities is demonstrated by the synthesis of submicron diamonds, containing nitrogen-related centers, from a mixture of adamantane and adamantane carbonitrile

Size-Dependent Thermal Stability and Optical Properties of Ultra-Small Nanodiamonds Synthesized under High Pressure

Diamond properties down to the quantum-size region are still poorly understood. High-pressure high-temperature (HPHT) synthesis from chloroadamantane molecules allows precise control of nanodiamond size. Thermal stability and optical properties of nanodiamonds with sizes spanning range from −1). Following the previously proposed explanation, we attribute this phenomenon to the Fano effect caused by resonance of the diamond Raman mode with continuum of conductive surface states. We assume that these surface states may be formed by reconstruction of broken bonds on the nanodiamond surfaces. This effect is also responsible for the observed asymmetry of Raman scattering peak. The mechanism of nanodiamond formation in HPHT synthesis is proposed, explaining peculiarities of their structure and properties

Structure and superconductivity of isotope-enriched boron-doped diamond

Superconducting boron-doped diamond samples were synthesized with isotopes of 10B, 11B, 13C and 12C. We claim the presence of a carbon isotope effect on the superconducting transition temperature, which supports the 'diamond-carbon'-related nature of superconductivity and the importance of the electron–phonon interaction as the mechanism of superconductivity in diamond. Isotope substitution permits us to relate almost all bands in the Raman spectra of heavily boron-doped diamond to the vibrations of carbon atoms. The 500 cm−1 Raman band shifts with either carbon or boron isotope substitution and may be associated with vibrations of paired or clustered boron. The absence of a superconducting transition (down to 1.6 K) in diamonds synthesized in the Co–C–B system at 1900 K correlates with the small boron concentration deduced from lattice parameters

Mie resonant diamond nanoantennas for spontaneous light emission

The size of the hosting particle affects the spontaneous light emission of embedded emitters. Here we study submicron-sized diamond particles containing silicon-vacancy color centers. We measure size-dependent scattering spectra, fluorescence emission rate, and Raman scattering intensity. Obtained results are found to agree with our calculations and demonstrate the potential of Mie resonances in nanoantennas design