Hall-Effect Sensor With Ferromagnetic Layer For Charge-Carrier Detection
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Solution Overview
Problem
Creating a sensitive charge-carrier Hall-effect sensor that can detect small changes in charge-carrier density is challenging due to the need for a high vector cross product of the magnetic field and current, and low and homogeneous charge-carrier density across the sample.
Innovation Solution
A charge-carrier Hall-effect sensor is designed with a semiconductor or semimetal layer, an underlying insulating layer, and a ferromagnetic layer, where the semiconductor layer is thin and two-dimensional, and the ferromagnetic layer provides a strong perpendicular magnetic field, allowing for detection of changes in charge-carrier density through the measurement of Hall voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional Hall-effect sensor is used, then the device structure is simple, but the sensitivity to detect small changes in charge-carrier density is insufficient
Solution Approach 1:
The patent employs a composite structure combining a two-dimensional material layer (such as graphene or transition metal dichalcogenide) with a ferromagnetic layer. The two-dimensional material provides extremely low and homogeneous charge-carrier density, while the ferromagnetic layer generates a strong perpendicular magnetic field through magnetic domain wall movement. This composite approach enables detection of single-atom or single-molecule changes in charge-carrier density by maximizing the Hall voltage signal without overly complicating the device structure.
Solution Approach 2:
The patent changes the physical state and parameters of the sensing material by using two-dimensional materials with exceptionally low charge-carrier density compared to conventional materials. Additionally, the magnetic field strength is dynamically changed through manipulation of magnetic domain walls in the ferromagnetic layer, allowing the vector cross product (I × B) to be sufficiently high to detect minute changes in charge-carrier density.
2Measurement precision
If the charge-carrier density is increased to improve signal strength, then the Hall voltage signal becomes stronger, but the ability to detect small changes in charge-carrier density is reduced
Solution Approach 1:
The patent utilizes two-dimensional materials that inherently possess extremely low charge-carrier density, representing a dramatic parameter change from conventional Hall-effect sensor materials. This low charge-carrier density is crucial because it amplifies the Hall voltage signal for a given change in carrier density, enabling detection of single-atom or single-molecule events. The ferromagnetic layer compensates for weak signals by providing a strong perpendicular magnetic field through domain wall manipulation.
Solution Approach 2:
The patent introduces dynamic control of the magnetic field through movement of magnetic domain walls in the ferromagnetic layer. By dynamically adjusting the magnetic field strength and direction through domain wall manipulation, the system can optimize the vector cross product (I × B) to maximize sensitivity for detecting small changes in charge-carrier density, rather than relying on a static high magnetic field.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The sensor can detect significant changes in charge-carrier density, including the presence of a single atom or molecule, by maximizing the vector cross product of the electric current and magnetic field, enabling high sensitivity and accuracy in measuring charge-carrier changes.
Implementation Method 1
the ferromagnetic layer provides a strong perpendicular magnetic field
Implementation Method 2
a ferromagnetic layer, where the semiconductor layer is thin and two-dimensional, and the ferromagnetic layer provides a strong perpendicular magnetic field
Implementation Method 3
A Hall-effect sensor may be used to measure the charge-carrier density of a material that provides an electric current channel of a Hall-effect sensor. A constant electric current is passed along the electric current channel of the material in a longitudinal direction and a voltage is measured across the channel in a transverse direction. The voltage, known as the Hall voltage, is proportional to the vector cross product of the electric current and any local magnetic field divided by the charge-carrier density.
Data Source
Figure 1~6
AI summary
A charge-carrier Hall-effect sensor comprising: a semiconductor or a semimetal layer; a pair of electric current contacts in electrical contact with the semiconductor or semimetal layer and separated in a first longitudinal direction along a first electric current channel; a pair of voltage contacts in electrical contact with the semiconductor or semimetal layer and separated in a second transverse direction, orthogonal to the first direction, and positioned on either side of the electric current channel; an electrically insulating layer underlying the semiconductor or the semimetal layer; and a ferromagnetic layer underlying the electrically insulating layer comprising at least one region having a magnetic moment with a component perpendicular to a plane comprising the pair of electric current contacts and the pair of voltage contacts.