Piezoelectric Probe Vibration for Bias-Free Surface Charge Measurement
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Solution Overview
Problem
Existing methods for measuring microscopic electrical properties of material surfaces, such as those using Kelvin probe force microscope (KPFM), electrostatic force microscope (EFM), and conductive atomic force microscope (CAFM), suffer from inaccuracies due to the application of AC and DC voltages affecting the sample material, leading to unreliable determination of charge density and work function.
Innovation Solution
A method and apparatus utilizing a piezoelectric ceramic to induce vibration of a probe above the sample material, measuring the target contact potential difference and induced alternating current amplitude to determine the work function and charge density without applying AC or DC voltages, using a pre-stored amplitude determination function based on resonant frequency and capacitance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If AC bias voltage and DC voltage are applied between the probe and sample material to measure electrical properties, then charge density and work function can be determined, but the applied voltages affect the electrical properties of the sample material, resulting in inaccurate measurement results
Solution Approach 1:
The patent extracts and removes the harmful AC and DC bias voltages from the measurement system. Instead of applying voltages between the probe and sample, the invention uses only AC voltage applied to the piezoelectric ceramic to drive probe vibration, eliminating the voltage application that was causing measurement inaccuracies while preserving the ability to measure electrical properties through contact potential difference and induced current.
Solution Approach 2:
The patent replaces the electrical field-based measurement approach (applying voltages to induce current) with a mechanical vibration-based approach. The probe is driven to vibrate mechanically via piezoelectric ceramic, and electrical properties are measured through the mechanical vibration-induced effects, specifically through contact potential difference and induced alternating current during vibration, rather than through direct voltage application.
2Measurement precision
If EFM uses piezoelectric ceramic to drive probe vibration and measures amplitude and phase changes, then qualitative determination of charge density can be made, but there is no exact correspondence between vibration parameters and electrostatic force magnitude, preventing accurate quantitative measurement
Solution Approach 1:
The patent introduces feedback mechanisms to establish exact correspondence between vibration parameters and electrostatic force. By measuring both the contact potential difference and the induced alternating current amplitude during probe vibration, and using these measurements in calculation formulas, the system achieves quantitative determination of charge density and work function, converting the qualitative EFM approach into a quantitative measurement system.
Solution Approach 2:
The patent changes the measurement parameters from simple amplitude and phase detection to include contact potential difference measurement and induced alternating current amplitude measurement. These parameter changes enable quantitative calculation of electrical properties through established physical relationships, transforming the measurement system from qualitative to quantitative capability.
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
Accurately determines the work function and charge density of the sample material's surface by measuring the induced alternating current amplitude and contact potential difference, improving measurement precision without the interference of external voltages.
Implementation Method 1
applying an alternating voltage on a piezoelectric ceramic so that a probe fixed on the piezoelectric ceramic vibrates
Implementation Method 2
measuring a target contact potential difference between the probe and the sample material, and determining a target amplitude of an induced alternating current generated due to the vibration of the probe
Data Source
AI summary
A method and an apparatus for measuring an electrical property of a sample material are provided. In the method, an alternating voltage is applied to a piezoelectric ceramic so that a probe fixed on the piezoelectric ceramic vibrates above a surface of the sample material, a target contact potential difference between the probe and the sample material is measured, and a target amplitude of an induced alternating current generated due to the vibration of the probe above the surface of the sample material, a target work function of the surface of the sample material is determined according to the target contact potential difference and a determined work function of the probe, and a target charge density of the surface of the sample material is determined according to the target amplitude, the target contact potential difference, and a pre-stored target amplitude determination function for the induced alternating current.