Hall effect sensors have long been a cornerstone of magnetic field sensing, valued for their simplicity and reliability. However, as applications evolve and demand for more precise, robust and versatile solutions, the limitations of traditional Hall sensors become apparent. These limitations include constrained temperature ranges, restricted dynamic ranges and interference from cross-magnetic fields due to their 3D molecular structures.

Graphene Hall Effect Sensors (GHS) address these challenges by leveraging the unique properties of graphene — a two-dimensional material known for its exceptional conductivity and mechanical strength. GHS offer a wide operational temperature range, from cryogenic conditions to high temperatures, and an expansive dynamic range for measuring both low and high magnetic fields. Additionally, their compact size allows for integration into space-constrained environments, making them especially valuable in sectors like automotive engineering.

The Hall Effect: A Foundation for Magnetic Sensing

All Hall sensors operate on the Hall effect principle: when a current flows through a material exposed to a magnetic field, charge carriers are deflected to one side, creating a measurable voltage. This voltage is directly proportional to both the strength of the magnetic field and the sensitivity of the sensing material.

Graphene enhances this effect by virtue of its two-dimensional structure. Unlike conventional 3D materials, graphene experiences the Hall effect exclusively within its atomic plane. This eliminates through-thickness interference and stray field effects, leading to cleaner signals and higher precision. In multi-directional magnetic fields, graphene’s charge carriers are deflected solely across its 2D plane, avoiding the diagonal deflections that compromise measurements in thicker materials.

The high carrier mobility of graphene further enhances its performance. By fine-tuning this property, the sensitivity of GHS can be tailored to specific applications. For example, higher sheet resistance can yield greater sensitivity when required, while higher mobility can be prioritized for less demanding scenarios.

Fabrication: Ensuring High-Quality Graphene

The performance of GHS relies heavily on the quality of the graphene used. Traditional fabrication methods, such as transferring chemical vapor deposition (CVD)-grown graphene onto sensor substrates, often introduce defects and contaminants that degrade performance. Instead, advanced methods like metalorganic chemical vapor deposition (MOCVD) enable the direct growth of graphene on substrates, ensuring a pristine, defect-free material.

Additional layers are applied to the graphene using atomic layer deposition (ALD), allowing precise control of its resistivity and sensitivity. These layers, typically metal oxides, like Al2O3 or nitrides, “dop” the graphene without introducing defects. This approach preserves graphene’s intrinsic properties while tailoring its electrical conductivity for specific sensing requirements.

Advantages of Graphene Hall Effect Sensors

Graphene’s unique characteristics translate into numerous advantages for GHS, including:

• Wide Dynamic Range: GHS can measure magnetic fields from microtesla (µT) to over 40 Tesla (T) without polarization effects, offering unparalleled versatility.
• Low Power Consumption: GHS consume many times less power than traditional silicon-based Hall sensors, thanks to current flow through graphene’s delocalized electron planes.
• Temperature Robustness: Operating effectively from -55°C to 150°C and even at cryogenic temperatures down to 4 K, GHS excel in extreme thermal environments where traditional sensors often fail.
• Precise and Clean Signals: The absence of through-thickness interference and stray fields ensures accurate measurements with low signal-to-noise ratios.
• High Sensitivity and Customizability: Layer-based doping methods allow precise tuning of graphene’s properties without compromising its structural integrity or performance.

Applications Across the Magnetic Field Spectrum

The capabilities of GHS make them ideal for a broad range of applications, from high-field environments like particle accelerators and electromagnets to low-field scenarios such as battery monitoring and quantum computing. Specific benefits include:

• Reliable performance in both low and high magnetic fields, ensuring consistent results regardless of operating conditions.
• Resilience in extreme magnetic fields and temperatures, outlasting conventional sensors in demanding environments.
• Stable sensitivity at high temperatures, overcoming the intrinsic limitations of semiconductor band gaps.

A Versatile Platform for the Future

By combining graphene’s exceptional properties with proprietary, innovative fabrication techniques, Paragraf’s GHS offer a powerful solution for diverse sensing applications. Whether the goal is precision measurement in ultra-high magnetic fields, effective operation in extreme environments or energy-efficient sensing in compact systems, GHS deliver performance and reliability that meet the demands of modern engineering and design challenges.

Get in touch today

At Paragraf, we’re not just developing GHS; we’re paving the way for next-generation sensing solutions. Contact our team to discover how our customizable and scalable graphene-based sensors can provide solutions in your industry, from cryogenics to automotive and beyond.