Scanning Transmission Electron Microscope Condenser Lens Partitioning
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Solution Overview
Problem
Current scanning transmission electron microscopes face limitations in adjusting the convergence angle without mechanical parts, leading to increased costs, reduced beam stability, and limitations in resolution and detection efficiency due to lens aberrations and complex detector arrangements.
Innovation Solution
The microscope features a condenser zoom system comprising the second and third condenser lenses to adjust the convergence angle and spot size, with the sample placed asymmetrically between the upper and lower pole piece faces of the objective electromagnetic lens, and an EDS detector mounted on an arm for linear movement, connected to a control unit for safe operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If mechanical parts (mechanically exchangeable aperture or multi-hole aperture with deflection system) are used to adjust the convergence angle, then the convergence angle can be changed, but the price increases, beam stability decreases, and the deflection system becomes necessary
Solution Approach 1:
The patent replaces the mechanical aperture system with an electromagnetic field-based solution. The condenser objective system uses electromagnetic lenses (condenser lens C1 and objective lens) to control the electron beam convergence angle through magnetic field adjustment, eliminating the need for mechanically exchangeable apertures and complex deflection systems. This substitution of mechanical control with electromagnetic control resolves the contradiction by maintaining convergence angle adjustability while reducing mechanical complexity and improving beam stability.
Solution Approach 2:
The patent changes the operational parameters of the condenser lenses (excitation currents of C1 and objective lens) to adjust the convergence angle dynamically. By varying the magnetic field strength of the electromagnetic lenses through parameter changes in excitation current, the system achieves continuous convergence angle adjustment without mechanical intervention, thereby eliminating the need for mechanical parts while maintaining adaptability.
2Manufacturing precision
If the pole piece gap is reduced to minimize axial aberration, then the resolution improves, but mechanical limitations are reached and detection efficiency decreases due to limited sample tilt and detector placement
Solution Approach 1:
The patent introduces asymmetry in the placement of the sample relative to the pole piece gap. Instead of positioning the sample at the center, the sample is placed closer to one pole piece face, creating an asymmetric configuration. This asymmetric placement allows the pole piece gap to be optimized for minimum axial aberration and maximum resolution while simultaneously providing sufficient space on the other side for detector placement and sample tilt accommodation, thus resolving the contradiction between resolution and adaptability.
3Adaptability or versatility
If the condenser aperture is placed above or below the condenser system, then the beam current and convergence angle can be adjusted, but the device complexity increases and beam stability decreases
Solution Approach 1:
The patent merges the functions of beam current control and convergence angle control into a single integrated condenser objective system. The condenser aperture is positioned within the electromagnetic field of the condenser lens C1 and objective lens, allowing both parameters to be controlled simultaneously through coordinated adjustment of the electromagnetic fields. This merging of control functions into a unified electromagnetic system eliminates the need for separate mechanical control systems, thereby improving beam stability while maintaining adaptability.
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 configuration enhances beam control without mechanical parts, reduces aberrations, and improves detection efficiency by allowing the placement of detectors for X-ray signal collection, achieving superior electron-optical performance and flexible operation modes.
Implementation Method 1
The electron gun - consisting of a (heated/cold) electron emitter, an extraction or control electrode and (multiple) accelerator electrodes - generates a real or virtual electron source (cross-over)
Implementation Method 2
The electrons emerging from the cross-over are focused by the condenser lens system and the objective pre-field lens into the sample and compose the primary beam
Implementation Method 3
an objective electromagnetic lens which generates a small electron spot and a scattering angle distribution image
Implementation Method 4
The transmitted electrons provide the information about the sample down to the atomic scale. The electrons which pass through the sample with no scattering or with a small scattering angle are defined as a bright field (BF) electrons
Data Source
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AI summary
The object of the present invention provides a scanning transmission electron microscope with the ability to adjust a beam current. The scanning transmission electron microscope comprises an electron source, which is configured to provide a primary electron beam with a cross-over, a condenser lens system, an objective electromagnetic lens and a detection system. A salient feature of presented invention is the partition of the condenser system lens into the first condenser lens and the system of second and third condenser lenses. Such a partition allows to place a condenser aperture between the first condenser lens and the condenser zoom system. Presented arrangement thus allows to adjust the beam current independently on the magnification of effective spot size.