Nitrogen vacancy (NV) centers are bright fluorescent defects in diamond lattice structures. They have emerged as useful optical sensors in extreme conditions, such as very high temperatures or pressures. This makes them attractive for applications in bioimaging, quantum information processing, nanoscale magnetometry, and thermometry.

The excited state lifetimes of NV centers in individual nanodiamonds are understood to be fast at room temperature, enabling development of temperature measurements with high spatial and temporal resolution.

Bommidi and Pickel obtained single-point temperature measurements using atomic force microscope nanomanipulation, which positions individual nanodiamonds at critical locations on a sample. Their research is the first to establish excited state lifetimes as temperature dependent, finding a lifetime decrease at temperatures between 300K and 500K.

“Using single nanodiamonds enables single-point temperature measurements with high spatial resolution approximately equal to the nanodiamond size, less than 100 nanometers,” said author Andrea Pickel.

The findings suggest harnessing temperature dependent excited state lifetimes of NV centers in individual nanodiamonds will aid all-optical, time-resolved nanothermometry near room temperature.

“This method may be particularly applicable under conditions where other single nanodiamond thermometry methods may fail, such as in applications where high temporal resolution is critical, at very high temperature where other thermometry signals cannot be detected, or in situations where microwave antenna required by other common methods is undesirable,” said Pickel.

In the future, the thermometry method could be applied to quantify the exact switching temperatures in phase change memory devices. Such devices exchange nanoscale amounts of phase change material between two electrical resistivity states using Joule heating.

Source: “Temperature-dependent excited state lifetimes of nitrogen vacancy centers in individual nanodiamonds,” by Dinesh K. Bommidi and Andrea D. Pickel. Applied Physics Letters (2021). The article can be accessed at https://doi.org/10.1063/5.0072357.