Conductive AFM with Bypass Circuit for Nanoscale Charge Dynamics
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Solution Overview
Problem
Conventional Atomic Force Microscopes (AFMs) lack the spatial and temporal resolution needed to effectively probe local charge carrier dynamics in nanostructured and disordered materials, such as perovskite solar cells, limiting the understanding of fundamental local properties and hindering the development of high-performance solar cells.
Innovation Solution
An enhanced AFM system with a conductive tip, an electrically isolated sample holder, a tunable optical source, a function generator, and a high bandwidth oscilloscope, along with a processor for generating local mobility, carrier lifetime, and impedance maps, is used to collect and analyze data on charge recombination and transfer with improved spatial and temporal resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional AFM systems are used, then basic topography and surface analysis can be performed, but spatial resolution and temporal resolution are insufficient to probe local charge carrier dynamics at nanoscale
Solution Approach 1:
The patent segments the measurement function by separating topography measurement (conventional AFM) from electrical property measurement (new integrated circuit), allowing each to be optimized independently while working together to provide comprehensive nanoscale characterization
Solution Approach 2:
The patent merges conventional AFM topography measurement capabilities with new electrical measurement circuitry into a single integrated system, enabling simultaneous acquisition of both structural and electrical property data at the same nanoscale locations
2Measurement precision
If conventional AFM circuit bandwidth is used, then system simplicity is maintained, but temporal resolution is insufficient to detect fast charge carrier dynamics
Solution Approach 1:
The patent introduces an intermediary measurement circuit that acts as a buffer between the sample and the conventional AFM system, capturing fast electrical signals with high bandwidth before transferring them to external measurement equipment for analysis
Solution Approach 2:
The patent replaces the conventional mechanical/electrical AFM detection system with an optical detection method using a laser and photodetector, which provides higher bandwidth and faster temporal resolution for measuring charge carrier dynamics
3Measurement precision
If AFM tip is kept in physical contact with sample, then electrical measurements can be made, but spatial resolution is reduced due to tip size and contact area
Solution Approach 1:
The patent replaces direct mechanical contact measurement with optical field-based measurement, where a laser beam interacts with the sample to induce local charging effects that are detected by the AFM tip, thereby eliminating the need for sustained physical contact and reducing mechanical damage
Solution Approach 2:
The patent introduces light as an intermediary between the AFM tip and the sample, where the laser beam serves as the primary interaction mechanism for inducing and detecting charge carrier dynamics, while the AFM tip only provides weak electrical sensing without significant mechanical contact
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 system enables the detection of local charge carrier dynamics with nanoscale spatial and sub-microsecond temporal resolution, facilitating the identification of optimal processing conditions and material improvements for next-generation solar cells.
Implementation Method 1
an optical source configured to direct light through the aperture and towards the sample
Implementation Method 2
a function generator configured to drive the optical source and provide a coordinated voltage to a sample positioned on the sample holder
Implementation Method 3
output signal of tip is sent to external preamplifier through a bypass circuit directly to collect analog data corresponding to charge recombination and transfer
Data Source
AI summary
A system for conductive atomic force microscopy measurements includes a function generator that drives a light source as well as current provided to a sample, designed sample holder for local charge dynamics measurements and output circuitry that includes both a frequency response analysis as well as a bypass circuit analysis portion. Bypass circuit with external preamplifier helped to overcome the obstacles of commercially available AFM circuit bandwidth (e.g. 100 kHz) to see the local characteristics with high temporal resolution. By obtaining the data output of the frequency response analyzer and the bypass circuitry, local mobility map, local carrier lifetime and transport time map, local carrier density map, and a nanoscale impedance map can be made of complex solid state devices at high temporal and spatial resolutions.