Cryo Shutter Recess Design for FIB Ice Contamination
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Solution Overview
Problem
Cryo-focused ion beam milling of biological samples is hindered by ice contamination due to sublimation of water molecules, limiting the number of lamellae that can be preserved during milling sessions, despite previous advancements like the use of a cryo-shutter and cryo-shield.
Innovation Solution
A cryo shutter device made of heat conductive material, configured to be cooled to cryogenic temperatures and positioned between the sample and ion source, with a small aperture and recess design to minimize open surface area, allowing efficient ion beam passage while enhancing cooling and reducing ice contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a cryo-shutter with a larger aperture is used to allow ion beam passage, then ion beam transmission is improved, but ice contamination of the sample increases due to larger open surface area
Solution Approach 1:
The shutter body is cooled to cryogenic temperatures specifically at the aperture region where ice contamination occurs, creating a local cold zone that traps water molecules. This allows the aperture to remain open for ion beam transmission while the localized cold environment prevents ice deposition on the sample
Solution Approach 2:
The shutter body acts as an intermediary cold trap between the ion source and the sample. It intercepts water molecules from the gas phase before they can reach the sample, using its cryogenically cooled surface as a trapping medium that redirects harmful water vapor away from the sample
2Object-affected harmful factors
If the shutter is positioned closer to the sample to improve shielding, then ice contamination is reduced, but ion beam passage is blocked by the shutter body
Solution Approach 1:
The shutter is positioned in the beam path such that the ion beam passes through the aperture in a direction that bypasses the main body of the shutter. The aperture is strategically located and sized to allow ion beam transmission while the shutter body extends in a different spatial dimension to provide shielding close to the sample
3Speed
If the open surface area of the shutter is increased to improve ion beam access, then ion beam transmission is improved, but cooling efficiency decreases leading to higher ice contamination
Solution Approach 1:
The shutter is designed with a recess that concentrates the cooling effect specifically at the aperture region, where ice contamination is most problematic. This localized quality enhancement ensures that the critical area maintains cryogenic temperatures even with a relatively large aperture, optimizing both ion beam access and cooling efficiency
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
Significantly reduces ice contamination rates, enabling longer automated milling sessions by effectively shielding the sample from ice deposition and improving cooling efficiency.
Implementation Method 1
the body is configured to be cooled to cryogenic temperatures... acts as a cold trap during the focused ion beam milling procedure... sublimation of water molecules from the gas phase
Implementation Method 2
ice contamination by sublimation of water molecules from the gas phase
Implementation Method 3
body, particularly consisting of a heat conductive material... configured to be cooled to cryogenic temperatures
Data Source
AI summary
The invention relates to a device (100) for reducing ice contamination of a sample (S) in a chamber (210) of a focused ion beam milling apparatus (200), wherein the device (100) comprises a body (110) configured to be cooled to cryogenic temperatures, wherein the body (110) comprises an aperture (111), which is configured such that an ion beam (I) generated by an ion source (220) can pass from the ion source (220) through the aperture (111) to the sample (S), wherein the body (110) comprises a recess (112), wherein said aperture (111) is arranged in the recess (112).The invention further relates to a focused ion beam milling apparatus (200) and a method for focused ion beam milling of a sample (S).