  Nanoscale optical thermometry is a promising non-contact route for measuring
local temperature with both high sensitivity and spatial resolution. In this
work, we present a deterministic optical thermometry technique based on quantum
emitters in nanoscale hexagonal boron-nitride. We show that these
nanothermometers exhibit better performance than that of homologous,
all-optical nanothermometers both in sensitivity and range of working
temperature. We demonstrate their effectiveness as nanothermometers by
monitoring the local temperature at specific locations in a variety of
custom-built micro-circuits. This work opens new avenues for nanoscale
temperature measurements and heat flow studies in miniaturized, integrated
devices.
