Scanning Probe Microscopy Force Mapping With Harmonic Signals
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional scanning probe microscopy methods, such as Tapping Mode AFM, are unable to accurately measure the forces between the probe tip and the surface due to their reliance on periodic averages, which fail to capture the full spectrum of forces, leading to incomplete force estimation.
Innovation Solution
The method employs a scanning probe microscopy system with wide-band probes and a recursive Kalman filter to analyze multiple frequency components of the sensor signal, allowing for accurate force estimation by quantifying two or more frequency components in a Fourier transform, particularly using sub- or super-harmonic modes, and applying a regularized Kalman estimator to model the dynamics of the cantilever.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional Tapping Mode AFM is used to scan the surface, then the scanning operation can be performed, but the force measurement precision deteriorates because only periodic average forces are captured
Solution Approach 1:
The patent applies dynamics by analyzing the dynamic response of the cantilever at multiple frequency components (fundamental frequency and harmonics) during intermittent contact. Instead of relying on static or periodic average measurements, the system captures the dynamic behavior of the cantilever across different frequencies to reconstruct the full force spectrum, thereby improving force measurement precision while preserving information.
Solution Approach 2:
The patent transitions from single-frequency (one-dimensional) force measurement to multi-frequency (multi-dimensional) analysis. By quantifying frequency components at the fundamental frequency and its harmonics, the system adds dimensional depth to the measurement, capturing a more complete picture of the tip-sample forces and resolving the contradiction between measurement precision and information loss.
2Measurement precision
If multiple frequency components are analyzed using Fourier transform, then the force estimation accuracy improves, but the computational complexity increases
Solution Approach 1:
The patent employs a recursive Kalman filter that uses feedback from previously estimated force values to refine current measurements. By incorporating feedback mechanisms, the system can process multiple frequency components efficiently, reducing the computational burden while maintaining high force estimation accuracy. The feedback loop allows the system to adapt and improve measurements over time without requiring excessive computational resources.
Solution Approach 2:
The patent changes the parameter representation by transforming the sensor signal into the frequency domain using Fourier transform, and then applying regularization techniques to the Kalman filter. This parameter transformation allows the system to handle multi-frequency data more efficiently, improving force estimation accuracy while managing computational complexity through mathematical optimization.
3Object-affected harmful factors
If intermittent contact mode is used, then the probe can scan the surface with reduced damage, but the force measurement becomes incomplete due to periodic averaging
Solution Approach 1:
The patent utilizes mechanical vibration by exciting the cantilever at its resonant frequency and analyzing the vibrational response at multiple frequency components. The intermittent contact mode causes modulations in the vibrational signal, and by analyzing these modulations at the fundamental frequency and harmonics, the system can extract complete force information without causing surface damage, thus resolving the contradiction between reduced damage and measurement completeness.
Solution Approach 2:
The patent leverages the periodic nature of intermittent contact by analyzing frequency components that arise from this periodic action. The cantilever's periodic contact with the surface creates characteristic frequency signatures that, when analyzed through Fourier transform and processed with Kalman filtering, provide complete force measurement information while maintaining the benefits of intermittent contact mode.
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 provides a stable and accurate real-time estimation of tip-sample forces, enabling precise force measurement during intermittent contact, which enhances the accuracy of surface mapping and material property analysis.
Implementation Method 1
the sensor may monitor a reflected laser beam that is reflected by the cantilever or the back of the probe tip, and which changes angle when the probe tip moves up or down
Implementation Method 2
vibrating the cantilever using an actuator; moving the probe relative to the substrate surface for performing said scanning, wherein said probe is held at a distance to the substrate surface such as to allow contact at a plurality of intermittent contact moments between the probe tip and the surface during said vibrating of the cantilever
Data Source
Figure 1
Figure 2A~2C
Figure 3
AI summary
This document relates to a method of performing surface measurements on a surface of a sample using a scanning probe microscopy system. The system comprises a sample support structure for supporting a sample, a sensor head including a probe comprising a cantilever and a probe tip arranged on the cantilever, and an actuator for scanning the probe tip relative to the substrate surface for mapping of the nanostructures. The method comprising the steps of: vibrating the cantilever using an actuator and moving the probe relative to the substrate surface for performing said scanning. The probe is held at a distance to the substrate surface such as to allow contact at a plurality of intermittent contact moments between the probe tip and the surface during said vibrating of the cantilever. The steps of vibrating of the cantilever and moving of the probe are performed concurrently. For performing the surface measurements, the method comprises obtaining a sensor signal indicative of a position of the probe tip during said scanning, and analyzing this signal by quantifying two or more frequency components in a Fourier transform for determining an estimate of a force value of a force between said substrate surface and said probe tip during said contact moments.