Optical and acoustic phonon temperature measurements using electron nanoprobe and electron energy loss spectroscopy

Measuring temperature at a high spatial resolution is a fundamental technique for investigating local static and dynamic thermal properties in various materials and devices. Here, we report temperature measurement by electron energy loss spectroscopy using monochromated electron probes of 1--2 nm diameter and large scattering vectors of electrons and based on the principle of detailed balancing between the annihilation and creation of phonons. Temperatures defined by optical and acoustic phonons are evaluated separately. We demonstrate that the use of acoustic phonons is advantageous for low-temperature measurements with higher accuracy. The scheme is applied to evaluating local temperatures in a diamond nanowire during Joule heating. We also discuss the Joule heating mechanism and key factors for improving temperature measurement accuracy.