A non-beam-based Doppler broadening of positron annihilation radiation (DBAR) spectrometer for a single piece of micron-thickness film

Abstract

Doppler broadening of positron annihilation radiation (DBAR) spectroscopy is a critical technique to provide electronic momentum information of materials. For conventional non-beam-based DBAR experiments, due to the continuous distribution of initial kinetic energy (0-545 keV) of positrons from 22Na source, two pieces of identical samples with sufficient thickness (> 1 mm for each sample with a density of 1 g/cm3) are required to stop almost all positrons in the samples. However, in many film studies, it is difficult or even impossible to meet this sample thickness requirement. In this work, judging by the output signals of a specially designed anticoincidence detector, the annihilation of positrons in a film sample and positron source are selectively collected. Furthermore, a new method is proposed to correct high-proportioned source components. Based on this, for the first time, a non-beam-based DBAR spectrometer was developed for a single piece of micron-thickness film. This approach will drastically broaden the application of DBAR spectroscopy in film characterization in future.