An optically detected magnetic resonance spectrometer

Abstract

A dual spectrometer capable of performing both conventional and optically detected electron paramagnetic resonance has been constructed at Victoria University of Wellington. The spectrometer is intended mainly for studying optically-active paramagnetic defect centres in wide band-gap semiconductors. Two novel features of this spectrometer are the use of a Gunn diode as the microwave source and a stripline resonator as the microwave resonant structure; these two replacing the normal klystron source and cavity resonator respectively. Apparatus developed and constructed for the spectrometer during this project includes the stripline resonator, electronics to operate and control microwave generation and detection apparatus, and software for a microcomputer system to control the spectrometer and perform data logging and signal averaging. Other apparatus used in the spectrometer is described and various problems encountered during its development are discussed. For conventionally detected resonance the spectrometer is compared to a commercially manufactured spectrometer and shown to have a similar sensitivity. For optically detected resonance, samples of materials with known spectra are used to provide a test. A donor resonance in ZnS (g = 1.88 ±0.01) was detected at a signal to noise ratio of ≈3. However, the general results of the ODMR tests are not as good as desired and further work is suggested to rectify this.