Optical Spectroscopic Measurement of Electrical Resistance

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Solution Overview

Problem

Existing methods for determining specific electrical resistance and conductivity are invasive, limited in spatial resolution, and unsuitable for high resistances or low conductivity samples, requiring multiple measurements and causing surface damage.

Innovation Solution

A non-contact, spatially resolved optical-spectroscopic analysis using the Drude model to determine charge carrier density and surface resistance, employing a system of detectors and an electronic evaluation unit to analyze electromagnetic radiation reflection and transmission, allowing for the calculation of specific electrical properties through Fresnel formulas and numerical optimization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If four-point measurement is used to determine specific electrical resistance with spatial resolution, then measurement precision is improved, but device complexity increases and surface damage occurs

Engineering Contradiction:

Improvespatial resolutionVSAvoidmeasurement complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical contact-based four-point measurement system with an optical measurement system. The optical system uses light reflection and spectral analysis to determine electrical resistance properties without physical contact, thereby reducing device complexity and avoiding surface damage while maintaining spatial resolution capability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces optical radiation as an intermediary between the measurement system and the sample. Instead of direct electrical contact, the system uses reflected light spectra as a mediator to extract electrical resistance information, simplifying the measurement process and eliminating surface alteration

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If four-point measurement is used to determine specific electrical resistance with spatial resolution, then measurement precision is improved, but surface damage occurs

Engineering Contradiction:

Improvespatial resolutionVSAvoidsurface damage

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of operation

If eddy current measurements are used to determine electrical conductivity, then non-contact measurement is achieved, but measurement precision deteriorates for high resistance samples

Engineering Contradiction:

Improvenon-contact measurementVSAvoidmeasurement accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent changes the measurement parameters by using optical spectral reflection across multiple wavelengths instead of single-frequency eddy currents. This parameter change enables the system to detect a broader range of electrical resistance values with high precision, overcoming the limitation of eddy current methods for high-resistance samples

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a universal measurement system that can handle both low-resistance and high-resistance samples through non-contact optical measurement. The system's ability to analyze spectral reflection across different wavelengths provides multi-functionality, replacing the need for different measurement techniques for different resistance ranges

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Area of stationary object

If multiple measurements are performed at different positions for larger samples, then measurement coverage is improved, but measurement time increases

Engineering Contradiction:

Improvemeasurement coverageVSAvoidmeasurement time

Core Design Contradiction:

Area of stationary objectVSLoss of time

Solution Approach 1:

The patent transitions from sequential point-by-point measurement to simultaneous two-dimensional spatial mapping. By using an optical system that can capture reflection spectra across the entire sample surface at once, the system achieves comprehensive area coverage in a single measurement, dramatically reducing measurement time while maintaining spatial resolution

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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

Enables non-destructive, high-resolution determination of specific electrical resistance and conductivity across entire surfaces, overcoming limitations of invasive methods and providing comprehensive quality control in various technical fields.

Implementation Method 1

electromagnetic radiation emitted from a broadband radiation source strikes the detectors either after reflection from the surface of the sample

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 2

after passing through a sample transparent to electromagnetic radiation

Methodology Applied

Scientific EffectTransmission:

Implementation Method 3

using a Drude model as a physical model or function to describe the wavelength-dependent behavior of the complex refractive index (the wavelength-dependent behavior of the real refractive index and the absorption coefficient or the dielectric function) of electrically conductive materials

Methodology Applied

Scientific EffectDrude model:

Implementation Method 4

using advantageous algorithms to describe the propagation of electromagnetic radiation in layered systems with Fresnel formulas

Methodology Applied

Scientific EffectFresnel formulas: Fresnel Diffraction

Data Source

PatentEP3265788B1Arrangement for spatially resolved determination of the specific electrical resistance and/or the specific electrical conductivity of samples

Publication Date: 2021.11.17 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV

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AI summary

Arrangement for spatially resolved determination of the specific electrical resistance and/or the specific electrical conductivity of a sample at different positions, with which a plurality of detectors for spatially resolved spectral analysis of electromagnetic radiation within a wavelength interval is configured. A surface of the sample is irradiated with homogeneous intensity. The detected spatially-resolved and wavelength-resolved measurement signals of the detectors, within a wavelength interval, are compared for each detected position with a wavelength-resolved function, wherein the wavelength-dependent function is produced by calculating the propagation of electromagnetic radiation in multi-layer systems using an optical model for physically describing the tested sample, while considering the wavelength-dependent curves of the linear optical refractive indices (n) and absorption coefficients (k) of all materials and/or substances forming the sample. By a change in the parameters of the physical function, same are brought iteratively to sufficient congruence with a calibration curve in order to determine the specific electrical resistance and/or the specific electrical conductivity at different positions in a spatially resolved manner.