Optimal architecture for diamond-based wide-field thermal imaging

Abstract

Nitrogen-Vacancy centers in diamond possess an electronic spin resonance that strongly depends on temperature, which makes them efficient temperature sensor with a sensitivity down to a few mK/ √ Hz. However, the high thermal conductivity of the host diamond may strongly damp any temperature variations, leading to invasive measurements when probing local temperature distributions. In view of determining possible and optimal configurations for diamond-based wide-field thermal imaging, we here investigate, both experimentally and numerically, the effect of the presence of diamond on microscale temperature distributions. Three geometrical configurations are studied: a bulk diamond substrate, a thin diamond layer bonded on quartz and diamond nanoparticles dispersed on quartz. We show that the use of bulk diamond substrates for thermal imaging is highly invasive, in the sense that it prevents any substantial temperature increase. Conversely, thin diamond layers partly solve this issue and could provide a possible alternative for microscale thermal imaging. Dispersions of diamond nanoparticles throughout the sample appear as the most relevant approach as they do not affect the temperature distribution, although NV centers in nanodiamonds yield lower temperature sensitivities compared to bulk diamond.Thermal imaging, enabling fast and accurate monitoring of heat distribution at sub-micron scales, has become decisive in a broad range of fields from exploratory research up to prototyping and manufacturing in nanomaterials science, nanoelectronics, nanophotonics or nanochemistry. Various detection schemes are being explored in this respect 1 . These schemes include tip-enhanced infrared or Raman thermometry 2,3 , scanning thermal microscopy (SThM) 4,5 , SQUID-based nano-thermometry 6 or nanoscale fluorescence thermometry making use of fluorescent nanoparticles either dispersed on the probed sample or attached to the tip of an atomic force microscope (AFM) 7 . Yet none of these techniques can simultaneously provide fast, sensitive (in the sub-K/ √ Hz range), and quantitative thermal imaging with a sub-micron spatial resolution under ambient conditions.Nitrogen-Vacancy (NV) centers in diamond have garnered growing attention in the last decade, notably because their electron spin resonance can be detected optically 8 and strongly depends on various external perturbations. This dependence has enabled to implement highly sensitive NV-based quantum sensors capable to locally probe several physical quantities including strain 9,10 , electric 11,12 and magnetic fields 13-15 . The sensing capabilities of the NV center have also been extended to thermometry 16 , building on the variation of the zero-field splitting parameter of its electron spin sublevels with temperature 17 . A thermal sensitivity in the range of 100 mK/ √ Hz was demonstrated for single NV centers hosted in nanodiamonds 18 and can reach values down to few mK/ √ Hz while using NV centers with long spin coherence times embedded in ultrapure bulk diamond samples 16,[1...

Diamond quantum thermometry: from foundations to applications

“…It is necessary to consider how physical contact of thermometers affect the temperature of the target objects via heat exchange at the interface between the target and the thermometer. This is particularly the case for diamond nanothermometry, which aims to measure the temperature of tiny objects, because diamond has a very high thermal conductivity of 1000-3000 W m −1 K −1 [132] (several times higher than that of copper). Reducing the size of the diamond is necessary to probe the small heat source, whereas the significant size reduction degrades the defect centre properties.…”

Widefield Diamond Quantum Sensing with Neuromorphic Vision Sensors

“…The measurement precision was below 0.5 K for all measurements (lower panel in Figure 4B), and an almost uniform temperature distribution (upper panel in Figure 4B) was observed due to the high thermal conductivity of the bulk diamond sample. [37] Based on the static measurement, we further demonstrated the dynamic temperature monitoring, where the temperature is controlled via an electrically-rotated linear polarizer that tunes the heating laser power (red in Figure 4A). By rotating the polarizer at a fixed speed 𝜔, the heating laser power irradiating the sample surface will be tuned in a continuous cosine square pattern (Figure S15A, Supporting Information), indicating a similar pattern in temperature dynamics, i.e., ΔT = A 0 cos 2 (𝜔t + 𝜑) + c. With the event-based OMDR measurement, we achieved a temporal resolution of 0.28 s, demonstrating an easy widefield temperature tracking.…”

Diamond quantum thermometry: From foundations to applications

“…However, contact thermometers need to consider how they themselves affect the temperature of the target objects via heat exchange at the physical interface between the target and thermometers. This is particularly the case for diamond nanothermometry, which aims to measure the temperature of tiny objects, because diamond has a very high thermal conductivity of 1000-3000 W/(m • K) [124] (several times higher than that of copper). Reducing the size of the diamond is necessary to probe the small heat source, whereas the significant size reduction degrades the defect centre properties.…”

“…Nanostructured bulk diamonds have been investigated to introduce bulk-grade diamond quantum thermometry performance to local temperature probing. Tanos et al reported nanopillar structures on bulk diamonds wherein NV centers show excellent spin properties [124]. They analyzed the heat conduction using the finite element method and evaluated the temperature sensing ability of these nanopillar structures.…”