PTC Thermistor Sample Heating for Electron Microscope Contamination
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Solution Overview
Problem
Electron beam microscopes and analyzers face challenges in maintaining image contrast and analysis accuracy due to carbon contamination on sample surfaces, which existing methods like ultrahigh vacuum evacuation and Ar ion sputtering cannot completely prevent without damaging the sample or requiring complex equipment design.
Innovation Solution
A sample heating method using a self-temperature-regulating PTC thermistor as a heating element, combined with direct current heating and optional plasma or oxygen radicals, effectively detaches pollutants from the sample surface without the need for ultrahigh vacuum or destructive sputtering, stabilizing the thermal environment for precise analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ultrahigh vacuum evacuation is used to remove pollutants, then pollutant removal is improved, but device complexity and operational restrictions increase due to baking operations and material constraints
Solution Approach 1:
The patent replaces the mechanical/thermal system of ultrahigh vacuum evacuation and baking with a plasma-based chemical system. Plasma generated from oxygen-containing gas directly cleans the sample surface and surrounding area through oxidation, eliminating the need for complex ultrahigh vacuum equipment and prolonged baking operations.
Solution Approach 2:
The patent changes the operational parameters from requiring ultrahigh vacuum conditions to operating in ordinary vacuum conditions with plasma treatment. This parameter change simplifies the device requirements while maintaining effective pollutant removal through the introduction of reactive oxygen species in plasma state.
2Quantity of substance
If Ar ion sputtering is used to clean sample surface, then pollutant removal is improved, but sample damage occurs and application is limited
Solution Approach 1:
The patent uses oxygen-containing plasma which generates highly reactive oxygen radicals that oxidize carbon-based pollutants on the sample surface. This chemical oxidation process effectively removes contaminants without the physical bombardment damage caused by ion sputtering, preserving the sample integrity.
Solution Approach 2:
The patent converts the potentially harmful effect of plasma (which could damage samples) into a beneficial cleaning process by using low-energy oxygen plasma. The reactive oxygen species selectively oxidize and remove organic contaminants while the low energy prevents damage to the sample surface, turning a potential hazard into an effective cleaning mechanism.
3Quantity of substance
If sample is heated to prevent contaminant formation, then contaminant growth is suppressed, but thermal drift occurs affecting measurement precision
Solution Approach 1:
The patent replaces thermal heating with plasma treatment as the cleaning mechanism. Plasma generated from oxygen-containing gas directly oxidizes and removes pollutants from the sample surface and surrounding area without requiring temperature elevation, thereby eliminating thermal drift while maintaining effective contaminant prevention.
Solution Approach 2:
The patent changes the operational parameter from elevated temperature to plasma state chemistry. By using reactive oxygen species in plasma form at or near room temperature, the system achieves effective pollutant removal without the thermal effects that cause sample drift and measurement errors.
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 method prevents contaminant growth on the sample surface, reduces thermal drift, and allows for high-accuracy image observation and elemental analysis without damaging the sample, using a PTC thermistor to maintain consistent temperature and suppress thermal expansion issues.
Implementation Method 1
heating of a sample is effective for preventing the occurrence of contaminants on the sample surface
Implementation Method 2
a self-temperature-regulating positive temperature coefficient (PTC) thermistor as a sample heating element
Implementation Method 3
an oxygen-containing gas such as air is ionized into a high-frequency plasma producing oxygen radicals, which are applied to the sample surface and its surrounding to oxidize pollutants and convert them into easily removed gases such as H2O, CO and CO2
Data Source
Figure 1~2
Figure 3
AI summary
The invention provides a sample heating holder for electron beam microscopes or analyzers and a sample heating method using the holder, which can prevent stably the occurrence of contaminants on the sample surface without entailing ultrahigh vacuum evacuation or destructing the sample surface. The sample heating holder for an electron beam microscope or analyzer has excellent performance in the suppression of the growth of carbon contaminations and the occurrence of a thermal drift during observation and analysis, and includes a positive temperature coefficient (PTC) thermistor as a heating element.