Electrometry by optical charge conversion (EOCC) using SiC defects

August 6, 2018

In a study published in Proceedings of the National Academy of Sciences, researchers indicate that due to the piezoelectric character of SiC, they obtain spatial 3D maps of surface acoustic wave modes in a mechanical resonator.

EOCC. (A) Schematic of the optical setup with one reset color (365 nm or 405 nm) and one pump color (976 nm). Illumination at 365 nm generates electron-hole (e-h) pairs that reset VV to VV0 (bright state) in the steady state, at 405 nm directly ionizes VV− (dark state) to VV0, and at 976 nm excitation converts VV0 to VV− by direct two-photon ionization or indirectly by one-photon ionization of local traps (11, 18). In addition, VV0 photoluminescence is provided through excitation at 976 nm. VV(0/−) is the transition energy level between the neutral and negatively charged states. VB and CB are the valence and conduction bands, respectively. An RF electric field (rms amplitude E, frequency fE) is applied across a coplanar capacitor with a 17-μm gap. VVs are created by carbon implantation immediately below the surface. A fast detector with 10-MHz bandwidth (BW) allows for direct detection of a full OCC transient signal in a single measurement. (B) VV is first reset to its bright state (VV0) by 405-nm illumination, followed by PL detection (Top) of the charge conversion toward the VV dark state by 976-nm excitation. Bottom shows the difference between conversion with and without applied electric field (10 MHz). Data are fitted to a stretched exponential function with R=42 kHz and n=0.54 obtained using a global fit for all electric field values.

Scientific Achievement

Using the optical properties and charge state dynamics of point defects in silicon carbide (SiC) to sense high frequency (MHz-GHz) electric field fluctuations.

Significance and Impact

Provides a means for all-optical, high frequency electrometry with quantum defects with a measured electric field sensitivity of 41 (?/??^?)/√Hz.

Research Details

A simple to implement, all-optical electrometry technique based on changes in the photoluminescence due to optical charge conversion of point defects in silicon carbide using both a UV and near-IR excitation wavelengths.
Under near-IR excitation, the defect photoluminescence becomes darker and as an electric field is applied, this change in photoluminescence (time decay) becomes faster.
Technique is highly sensitive to electric fields and sensitive to high frequency (MHz-GHz) electric and strain fields, making it ideal for studying MEMs structures.

DOI: 10.1073%2Fpnas.1806998115

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