Sensor Development

In a collaboration with IBM, and funded by an NSF Instrumentation for Materials Research–Major Instrumentation Projects (IMR-MIP) grant, the Moler group has developed 3 next generation SQUID microscope sensors.

Scanning SQUID susceptometers with sub-micron spatial resolution

The first, shown below, is a scanning SQUID susceptometer. Our susceptometers have a shielded gradiometric geometry with on-chip field coils. This design enables simultaneous local measurement of magnetic flux and magnetic susceptibility.

a) Schematic, b) Layout of the entire sensor chip, c) 3D rendering of the pickup loop/field coil region, and d) Calculated sensitivity profile of the sensor.

A description of first results from this sensor have appeared in J.R. Kirtley et al., “Scanning SQUID susceptometers with sub-micron spatial resolution”, Rev. Sci. Instrum. 87, 093702 (2016).

Scanning SQUID susceptometers with dispersive readout

The Moler group, in collaboration with Hendrik Bluhm’s group at RWTH Aachen in Germany and IBM, has developed a new kind of scanning SQUID susceptometer, which senses magnetic fields through changes in the resonance frequency of the device.

a) Schematic, b) Full layout of the sensor, c) Layout of the pickup loop/field coil region, and d) Resonant frequency vs. applied flux for one such device.

First results from these sensors haveappeared in F. Fouroughi et al., “A micro-SQUID with dispersive readout for magnetic scanning microscopy”, Appl. Phys. Lett.112, 252601 (2018). 

Scanning SQUID samplers

In collaboration with IBM we have also developed scanning SQUID samplers, capable of measuring periodic magnetic signals on micron length-scales with demonstrated 40 ps time resolution.

a) Schematic b) Full chip layout, c) Layout of the active region of the sensor, d) Simulation of the ultimate time resolution of this sensor.

First results from this sensor have been published in Zheng Cui et al., “Scanning SQUID sampler with 40-ps time resolution”, Rev. Sci. Instrum. 88, 085106 (2017).

The Moler group SQUID sensors have been used to measure the vibrations between sample and sensor in a SQUID microscope. This work was published in Daniel Schiessl et al., “Determining the vibrations between sensor and sample in SQUID microscopy”, Appl. Phys. Lett. 109, 232601 (2016).