High frequency electrometry and imaging with defects in silicon carbide

Optically active defects in wide bandgap host materials are promising sensors of local properties such as magnetic fields, electric fields, temperature and mechanical strain [1]. While magnetometry has received considerable interest owing to the spin properties of these defects, electrometry and strain sensing have been significantly more challenging due to the weak sensitivity of the ground spin state.

Here we demonstrate that the charge state of defects in silicon carbide (SiC), including divacancies and silicon vacancies, can be used to sense high frequency (MHz – GHz) electric fields and acoustics [2]. Optical excitation can convert the defect from a bright (photoluminescent) charge state to a dark charge state, and vice-versa [3]. This conversion rate depends directly on local high frequency electric fields and mechanical strains, resulting in direct modulation of the photoluminescence intensity and enabling sensing protocols. We further develop methods for spectroscopy (phase and frequency resolution) and vector measurements.

We explore electric field and strain sensing using both this novel charge technique and spin measurements in various electromechanical devices. We map the electric fields from lithographically patterned capacitors and observe mechanical modes in a surface acoustic wave resonator and in clamped membranes. We obtain 3D spatial and high frequency information typically challenging to achieve with other sensing techniques. This demonstrates the potential of optically active defects for in-situ electrical and micromechanical systems characterization in commercial materials such as SiC.

[1] F. J. Heremans et. al., Proc. IEEE 104, 10 (2016).
[2] G. Wolfowicz et. al., Proc. Natl. Acad. Sci. 115, 31 7879-7883 (2018).
[3] G. Wolfowicz et. al., Nat. Com. 8, 1876 (2017).

In collaboration with S. J. Whiteley, C. P. Anderson, A. L. Yeats, P.-L. Yu, S. Bhave, F. J. Heremans, D. D. Awschalom.