Work Function Measurement Apparatus with Dual Photoemission and Kelvin Probe Modes
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Solution Overview
Problem
Current methods for measuring work function properties of surfaces, such as the Kelvin probe and photoelectric effect techniques, face limitations in resolution and duration, with Kelvin probes providing relative measurements that require calibration and photoelectric effect instruments typically resolving to 0.050 - 0.100 eV with measurement durations of 5-10 minutes.
Innovation Solution
A measurement apparatus and method that combines a probe capable of measuring contact potential difference and a light source for photoelectric emission, with the probe operable in modes for relative and absolute work function measurements, allowing simultaneous or quasi-simultaneous operation, and featuring a gaseous environment with controlled humidity or nitrogen, and optional features like modulated radiation and multiple light sources for enhanced precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If photoelectric effect instruments are used for work function measurement, then absolute work function values can be obtained, but measurement duration is long (5-10 minutes) and resolution is limited (0.050 - 0.100 eV)
Solution Approach 1:
The patent combines the Kelvin probe system with a photoelectric emission detection system into a single integrated measurement apparatus. This merging allows the system to perform both contact potential difference measurements and photoelectric threshold measurements simultaneously or sequentially, thereby achieving high-resolution work function measurements without the long measurement times previously associated with photoelectric instruments alone
Solution Approach 2:
The patent employs dynamic modulation techniques where the probe oscillates at a specific frequency and the light source is modulated. By detecting signals at these modulated frequencies, the system achieves rapid data acquisition and processing, reducing measurement duration while maintaining high resolution through frequency-domain signal separation and noise filtering
2Productivity
If Kelvin probe is used for work function measurement, then measurement speed is fast, but only relative work function values are obtained requiring calibration
Solution Approach 1:
The system performs preliminary calibration measurements using the photoelectric effect to establish absolute work function reference values. These preliminary absolute measurements are then used to calibrate the Kelvin probe's relative measurements, enabling the system to maintain fast measurement speeds while achieving absolute accuracy through the integrated dual-mode capability
Solution Approach 2:
The patent uses a reference material with known work function properties as an intermediary. By measuring the contact potential difference between the probe and the reference material, and combining this with photoelectric threshold measurements, the system establishes an absolute reference frame that transforms relative Kelvin probe measurements into absolute work function values without sacrificing measurement speed
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
This approach enables faster and more accurate work function measurements, reducing errors from 0.050 - 0.100 eV to 0.010 - 0.030 eV, and allows for simultaneous or quasi-simultaneous relative and absolute work function determination, improving resolution and measurement speed.
Implementation Method 1
a light source; wherein the light source is configured to, in use, emit radiation for triggering photoelectric emission from a sample which is provided on or forms the surface
Data Source
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AI summary
A measurement apparatus for surface analysis carried out in a gaseous environment such as air comprises a measurement device capable of measuring a contact potential difference between a probe and a surface, and a light source that triggers photoelectric emission from a sample. The apparatus may operate in "dual" photoemission and contact potential difference (CPD) measurement modes.