TEM Phase Plate Cleaning via Dry Etching and Inert Atmosphere
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Solution Overview
Problem
The existing methods for using phase plates in transmission electron microscopes (TEM) face challenges in enhancing image contrast without impairing resolution, particularly when observing deep-frozen specimens, as existing cleaning methods fail to effectively remove oxygen and carbon compounds, leading to impurity deposition during electron irradiation.
Innovation Solution
A method involving etching the phase plate with an oxygen and carbon removal agent before first-time irradiation, followed by maintaining a reduced oxygen and carbon concentration atmosphere, utilizing dry etching techniques such as argon/hydrogen mixtures, and achieving a high vacuum environment to prevent re-deposition of impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the phase plate is cleaned by conventional methods, then the cleaning process is simple, but oxygen and carbon compounds remain on the surface leading to impurity deposition
Solution Approach 1:
The patent applies dry etching technology to change the cleaning parameters from conventional mechanical or chemical cleaning to plasma-based etching. This removes oxygen and carbon compounds from the phase plate surface through controlled plasma reactions, achieving thorough cleaning that conventional methods cannot accomplish while maintaining a manageable process through automated control
Solution Approach 2:
The patent introduces a holding atmosphere with reduced oxygen and carbon compound concentrations (oxygen ≤1×10¹¹/cm³, carbon ≤5×10¹³/cm³) to maintain the cleaned phase plate surface. This inert-like environment prevents re-deposition of impurities during electron beam irradiation, ensuring sustained cleaning effectiveness without requiring continuous complex cleaning operations
2Productivity
If the phase plate is etched after first irradiation, then the etching process can be integrated into the examination workflow, but more impurities are deposited making cleaning harder
Solution Approach 1:
The patent performs etching before the first electron beam irradiation to remove oxygen and carbon compounds in advance. This preliminary cleaning action prevents impurity deposition during subsequent irradiation, making the cleaning process more effective rather than harder, while still allowing integration into the examination workflow through proper sequencing
3Ease of operation
If the phase plate is held in ambient atmosphere, then the handling is convenient, but oxygen and carbon compounds redeposit on the surface
Solution Approach 1:
The patent implements a holding atmosphere system that maintains reduced oxygen (≤1×10¹¹/cm³) and carbon (≤5×10¹³/cm³) compound concentrations between etching and irradiation. This controlled environment prevents re-deposition of impurities while allowing the phase plate to be held and transferred, balancing convenience with surface cleanliness through automated atmosphere control
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 effectively cleans the phase plate by removing surface oxides and carbon deposits, ensuring improved image contrast without compromising resolution by maintaining a controlled atmosphere and precise etching conditions, resulting in enhanced image quality.
Implementation Method 1
the phase plate is etched with an etching agent suitable for removing compounds containing oxygen and/or carbon
Implementation Method 2
the holding atmosphere is a high vacuum, and so the pressure is at most 10⁻³ mbar, preferably at most 10⁻⁴ mbar, and more preferably at most 10⁻⁵ bar
Implementation Method 3
non-scattered electrons may pass through the phase plate without any further interaction, for example through a through hole in the phase plate, whereas the scattered electrons pass through the phase plate material and are accordingly subjected to an additional phase shift
Data Source
AI summary
The present invention relates to a method for cleaning a phase plate (1) for a transmission electron microscope wherein said phase plate is etched before being irradiated for the first time in the TEM, and is then held in an ultra-pure holding atmosphere until the irradiation in the TEM.