Modulation frequency dependence of continuous-wave optically/electrically detected magnetic resonance

TL;DR

This paper develops analytical solutions for the modulation frequency dependence in cwODMR and cwEDMR, revealing complexities and ambiguities in interpreting the underlying spin-dependent processes in these spectroscopic techniques.

Contribution

It introduces closed-form solutions based on an intermediate pair recombination model for cwODMR and cwEDMR, highlighting interpretative ambiguities and limitations of existing models.

Findings

Multiple models cannot be distinguished based on experimental data.

Signal signs are influenced by various processes and parameters.

Recombination types cannot be distinguished solely from cwODMR and cwEDMR signals.

Abstract

Continuous wave optically and electrically detected magnetic resonance spectroscopy (cwODMR/cwEDMR) allow the investigation of paramagnetic states involved in spin-dependent transitions, like recombination and transport. Although experimentally similar to conventional electron spin resonance (ESR), there exist limitations when applying models originally developed for ESR to observables (luminescence and electric current) of cwODMR and cwEDMR. Here we present closed-form solutions for the modulation frequency dependence of cwODMR and cwEDMR based on an intermediate pair recombination model and discuss ambiguities which arise when attempting to distinguish the dominant spin-dependent processes underlying experimental data. These include: 1) a large number of quantitatively different models cannot be differentiated, 2) signs of signals are determined not only by recombination, but also by other processes like dissociation, intersystem-crossing, pair generation, and even experimental parameter such as, modulation frequency, microwave power, and temperature, 3) radiative and non-radiative recombination cannot be distinguished due to the observed signs of cwODMR and cwEDMR experiments.