Electrons are the backbone of modern-day technology. Electrons power all electronic devices, no matter how big or small. However, undesired and uncontrolled charges can cause damage to electronic devices, which lowers their performance over time. Some common examples of the undesirable charges in electronic devices include gate-oxide breakdown in flash memory devices and charge-noise at the nanoscale level in sensitive devices, such as wide bandgap (WBG) semiconductors and quantum technologies. 

Detecting individual charges is a crucial part of materials science, as having a good fundamental understanding of what is going on at the atomic level is vital for advancing both classical and quantum technologies beyond their current levels. With a focus today on high-performance devices that can operate with lower noise, understanding and resolving these charges at the atomic lattice level in a timely manner is key to ensuring that new devices are performing optimally. This is where new advanced electrometers are required. 

The Need for Electrometers that Can Measure at Small Scales 

Even though there has been a lot of progress made with improving the capabilities of electrometers over the years, they still can’t provide time-resolved information on elementary charges with sub-nanometre resolution, which is crucial for highly sensitive technology where atomic-scale charges can easily affect performance. 

One example is 2D ferroelectric systems. These devices would benefit from a highly sensitive electrometer because it could provide fundamental insights into some of the unknown foundational aspects of their physical characteristics. As classical systems continue to get smaller, the most common component at the forefront of this miniaturisation is silicon transistors. They are now only a few nanometres in size, with intentions of getting smaller. As they reach smaller and smaller scales, they get increasingly susceptible to charge-induced noise. So, having an electrometer that can measure these charges could well be crucial for the future of transistor miniaturisation as well.  

One of the other main areas that would benefit, though, is quantum technology. In ion-based quantum computers, for example, localised electronic states can cause signal decoherence due to motional heating, whereas superconducting quantum bits (qubits) are susceptible to defect-induced charge noise. For atom-like spin qubits in WBG semiconductors, optical and spin decoherence can occur due to charge-noise effects. All these quantum platforms can have different atomic-scale charge issues, so understanding the underlying detrimental mechanism for each specific platform is key to developing quantum technology with high performance.  

Understanding more at the fundamental level, such as lattice defect formation, electron dynamics and decoherence processes, could also help to develop a wider range of quantum, photonic, and nanoscale electronic devices. 

Quantum Electrometer Can Detect Single Charges 

Researchers have now developed a quantum electrometer that can detect the electric fields generated by single and multiple elementary charges. The electrometer is incredibly sensitive, with a relative sensitivity of 10-7 to electrical fields and can detect individual charge state dynamics down to the Angstrom level within 60 nanoseconds. 

The electrometer contains an electric field-sensitive and optically active local probe, and a read-out unit. The local probe is a negatively charged tin-vacancy colour centre (SnV) in diamond. The SnV is a solid-state defect that undergoes fluorescent transitions and a non-linear response to electric fields. The read-out unit is a microscope that performs photoluminescence excitation spectroscopy on the local atomic probe.  

Measuring Charge Dynamics with Quantum Precision

The spectroscopy unit is based on frequency modulation using electro-optical modulators, which enables the charge dynamics to be deduced by measuring nonfluorescent defects under laser irradiation. Measuring the energy shift at the location of the probe identifies the magnitude of the electric field, which enables local atomic-scale charges to be deduced. The system is categorised as a time-resolved quantum electrometer that can measure at the atomic level. 

The sensor probe also exhibits a negligible linear- and strong non-linear response due to its inversion symmetry, which makes it suitable for detecting dopant and defect densities in semiconductors. The inversion centre of the sensor means that the further the defect is away from the probe, the higher the spectral shift. This makes the probe very sensitive to charges very close to the probe. The high relative electric field sensitivity of 10-7 allows for a very high spatial resolution, down to a few Angstroms, including charge densities up to 100 ppm. 

Applications and Future Potential 

The sensor can detect a range of single charge defects and charge traps, and can be used to understand the origin of charge transport phenomena. This includes the detection of topological quantum phenomena in ferroelectrics, such as ferroelectric vortices and polar skyrmions. Identifying different charge defects at the atomic lattice level also enables the transport dynamics and material properties of different materials and technologies to be determined. 

In this study, the probe was stationary and located inside a bulk crystal. However, the probe could be integrated into the tip of a scanning probe microscope (SPM) that would enable position-dependent measurements to be taken. This could potentially open more applications in magnetometry. It could also be integrated into nanodiamond materials to enable the study of single and multiple lattice defects in optically active quantum memories, silicon transistors, and defect-induced charge noise in on-chip ion and superconducting computers.  

The researchers also identified a secondary application for the probe. As well as being used to probe atomic-level dynamics, the probe’s sub-diffraction resolution and sensitivity to background charge-noise could be harnessed for estimating the position of an illumination laser with 1 nm of the actual position. 

The researchers have also stated that, alongside using SnV, similar probes based on germanium or silicon vacancies (and other materials with inversion symmetric defects) could be used as a local probe. So, there’s a lot of scope for building highly sensitive electrometer probes for highly sensitive technologies, especially in the quantum technology space.  

Conclusion

Time-resolved quantum electrometers based on inversion-symmetric colour centres provide the missing link between atomic-scale charge dynamics and device-level performance. By resolving single-charge effects with sub-nanometre precision and nanosecond timing, this approach offers a practical path to diagnosing charge noise, characterising dopants and defects, and accelerating advances in semiconductors, ferroelectrics, and quantum technologies.

Reference: 

Schroder T. et al, Quantum electrometer for time-resolved material science at the atomic lattice scale, Nature Communications, 16, (2025), 6435