Graphene Heating Chip for Stable In Situ TEM Windows
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Solution Overview
Problem
In situ TEM characterization is hindered by the thermal expansion of metal resistive layers and silicon nitride films, causing sample misalignment due to differing thermal expansion coefficients, which affects the precision and accuracy of dynamic observations.
Innovation Solution
A graphene heating chip is developed with a graphene film integrated onto a suspended silicon nitride membrane, utilizing van der Waals forces to minimize interfacial stress and reduce thermal expansion, allowing for precise temperature control and uniform heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a metal resistance layer and SiNx film form a double-layer structure for heating, then ultra-low heat capacity and fast temperature control are achieved, but the electron-transparent window swells at high temperature due to different thermal expansion coefficients
Solution Approach 1:
The patent changes the material parameter of the resistive heating layer from metal to graphene. Graphene's thermal expansion coefficient closely matches that of SiNx film, eliminating the differential thermal expansion problem. This material substitution resolves the contradiction by maintaining fast temperature control while achieving dimensional stability at high temperatures.
Solution Approach 2:
The patent creates a composite structure where graphene is integrated with the SiNx film to form a unified heating membrane. This composite material approach combines the ultra-low heat capacity of thin-film structures with the matched thermal expansion properties of graphene, simultaneously achieving fast response and dimensional stability.
2Measurement precision
If the electron-transparent window is made thin for TEM observation, then spatial resolution is improved, but thermal expansion causes sample misalignment
Solution Approach 1:
The patent changes the thermal expansion parameter of the window material by replacing metal with graphene. This parameter change allows the window to remain thin for high spatial resolution while maintaining dimensional stability through graphene's matched thermal expansion coefficient with SiNx, preventing sample misalignment during heating.
3Power
If a metal resistance layer is deposited on SiNx film for heating, then electrical heating function is achieved, but interfacial stress causes window swelling
Solution Approach 1:
The patent changes the material composition parameter from metal to graphene. Graphene's lattice structure and bonding characteristics result in minimal interfacial stress with SiNx film during thermal cycling, eliminating the window swelling problem while maintaining effective Joule heating power.
Solution Approach 2:
The patent converts the potential harm of thermal expansion mismatch into a benefit by selecting graphene, whose thermal expansion properties naturally match SiNx. This transforms what was previously a harmful interfacial stress problem into a beneficial stress-free interface, eliminating window deformation.
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
The graphene heating chip achieves rapid heating to high temperatures with minimal sample cell expansion, ensuring accurate and dynamic TEM observations by reducing interfacial stress and maintaining temperature uniformity.
Implementation Method 1
utilizing van der Waals forces to minimize interfacial stress and reduce thermal expansion
Implementation Method 2
graphene heating chip achieves rapid heating to high temperatures
Data Source
AI summary
A graphene heating chip includes a substrate, an insulating layer, a graphene film, and a plurality of electrodes. The substrate has two opposite a first surface and a second surface, and the substrate defines a through hole. The insulating layer is suspended on the substrate. The insulating layer covering the through hole and not in direct contact with the first surface is defined as a window, and a plurality of grooves are formed on the window. The graphene film covers the window, and the graphene film includes a first graphene film portion and a second graphene film portion, and the first graphene film portion and the second graphene film portion are spaced apart from each other. The plurality of electrodes are located on the surface of the insulating layer away from the substrate. The present application also provides a method for making the graphene heating chip.