Temperature-Dependent Excited State Lifetimes of Nitrogen Vacancy Centers in Individual Nanodiamonds

Modern electronic and data storage technologies combine shrinking feature sizes with ever-increasing operating speeds, leading to transient nanoscale hotspots that can limit device performance. Quantifying hotspots in operating devices thus requires a non-invasive thermometer with high spatial and temporal resolution. Nitrogen vacancy (NV) centers are luminescent defects widely employed for thermometry, most commonly via temperature-dependent shifts of their optically detected magnetic resonance. Recently, alternative all-optical approaches have also gained traction. Excited state lifetime thermometry is an all-optical technique that has been implemented using other fluorophores but has not previously been demonstrated for NV centers in individual nanodiamonds (NDs). We measured the excited state lifetime of NV centers in individual NDs between 300 K and 500 K and recorded a 32 ± 7.0% and 35 ± 8.3% average decrease in the lifetimes of individual NDs on silicon and glass substrates, respectively, over this temperature range. A linear approximation applicable to nearly all measured NDs yields temperature coefficients of -2000 ± 240 ppm/K and -2600 ± 280 ppm/K for NDs on silicon and glass, respectively. Beyond all-optical operation, single-ND lifetime thermometry offers ~100 ns temporal resolution and utilizes time-correlated single photon counting measurements ideally suited to low emission intensities, a limiting factor for other NV center thermometry techniques above 700 K. We also demonstrate that atomic force microscope nanomanipulation can position individual NDs at critical locations on a sample, enabling single-point temperature measurements that combine ~100 ns temporal resolution and ~100 nm spatial resolution. Finally, our results have implications for other single-ND excited state lifetime sensing applications, where care is required to avoid conflating changes in temperature and other parameters.