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Diamond Materials

Diamond Materials for Quantum Application

23. September 2014: The DFG research group FOR 1493 “Diamond Materials and Quantum Applications” goes into its second funding period. FOR1493 is a national research consortium funded by the Deutsche Forsch-ungsgemeinschaft.

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ERC Advanced Grant

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A new diamond based thermometer measures temperatures on nm scale

The precise measurement of temperature is a vital characterization tool in material and life sciences. However, at the length scale of for example state-of-the-art silicon technology or intracellular organelles only a few thermometers exist and their accuracy is often insufficient to monitor processes of interest.

We have developed a novel temperature sensor which combines high accuracy and high spatial resolution at the same time. To this end we have exploited the temperature response of a single quantum system inside the diamond lattice, namely the nitrogen-vacancy (NV) center.

Nanodiamonds form rigid and protective cages for defects like the NV center which can be used as versatile sensor probes, either attached to scanning devices, like atomic force microscopes, or dispersed on or inside a sample. Their small sizes (~10 – 100 nm) allow measurements on the nanometer scale. The electronic spin associated with the NV center in diamond is sensitive to many influences from its environment, for example magnetic and electric fields. Using a new technique now also allows to measure temperature with high accuracy, without having to modify the nanodiamond probe.

Changes in the temperature affect the transition frequencies of the NV spin. This effect is usually hidden as other effects, mostly magnetic fields, dominate the spin dynamics. In order to reveal the influence of the temperature, a new decoupling technique was devised. It cancels out effects arising from magnetic fields, but retains the temperature influence. In addition the diamond quality was improved substantially to reduce deleterious effects of lattice impurities.

This way a temperature sensor with an accuracy of 1 mK and a sensitivity of 5 mK/Hz½ was realized. Using dispersed nanodiamonds on a glass slide (Fig. a), we could measure the temperature gradient close to an operational microstructured resonator in the range of a few micrometers (Fig. b).

Our novel method could yield applications in material and life sciences. One could for example imagine tracking temperature changes during the metabolism of a living cell.

This research was a joint effort of the Universities of Tsukuba (Japan), Dortmund and Stuttgart and the company Sumitomo.


Figure a: Schematics of dispersed nanodiamonds. Typical scales are in the range of tens to hundreds of nanometers. Single nanodiamonds containing NV centers can be used as individual temperature probes.
Figure b: The temperature gradient near a heated RF-guide is measured with dispersed nanodiamonds.

Reference:
“High-Precision Nanoscale Temperature Sensing Using Single Defects in Diamond”
P. Neumann, et al., Nano Lett., 2013, 13 (6), pp 2738–2742