Nano-Hall sensors with granular Co-C

TL;DR

This paper demonstrates that granular Co-C nano-Hall sensors, fabricated via focused electron or ion beam induced deposition, exhibit significantly enhanced Hall effects and magnetic field resolution at room temperature, surpassing pure Co sensors.

Contribution

It introduces a novel fabrication method for granular Co-C nano-Hall sensors with improved sensitivity and resolution, highlighting the role of granular structure and Co ratios.

Findings

Hall effect increased by two orders of magnitude in granular Co-C wires

Optimal Co ratio for magnetic field resolution is 60-70%

Room temperature flux resolution of 2×10^{-5} φ_0 in a 200×200 nm^2 area

Abstract

We analyzed the performance of Hall sensors with different Co-C ratios, deposited directly in nano-structured form, using $Co_2(CO)_8$ gas molecules, by focused electron or ion beam induced deposition. Due to the enhanced inter-grain scattering in these granular wires, the Extraordinary Hall Effect can be increased by two orders of magnitude with respect to pure Co, up to a current sensitivity of $1 \Omega/T$. We show that the best magnetic field resolution at room temperature is obtained for Co ratios between 60% and 70% and is better than $1 \mu T/Hz^{1/2}$. For an active area of the sensor of $200 \times 200 nm^2$, the room temperature magnetic flux resolution is $\phi_{min} = 2\times10^{-5}\phi_0$, in the thermal noise frequency range, i.e. above 100 kHz.