By Josh Perry, Editor
Researchers from the University of Illinois at Chicago (UIC) have demonstrated that by sandwiching 2-D materials between 3-D silicon bases and an ultrathin layer of aluminum oxide heat transfer is enhanced and overheating can be prevented in nanoelectronics.
An experimental transistor using silicon oxide for the base, carbide for the 2D material and aluminum oxide for the encapsulating material. (Zahra Hemmat/UIC)
According to a report from the university, this process overcomes the main bottleneck in using 2-D materials, such as graphene, in creating fully functional nanoelectronics, which is the weak interactions between 2-D materials and silicon. This interaction leads to poor thermal conductivity and, ultimately, to overheating.
Researchers noted that the bonds between 2-D materials and the silicon substrate are weak and as heat builds up hot spots are created. By adding an encapsulating layer on top of the 2-D material, researchers doubled the energy transfer between the 2-D layer and the silicon.
A prototype transistor was created to test this process. Silicon oxide was used as the base and carbide for the 2-D material. Aluminum oxide was the encapsulating material.
“At room temperature, the researchers saw that the conductance of heat from the carbide to the silicon base was twice as high with the addition of the aluminum oxide layer versus without it,” the article explained.
Up next for the researchers is to test different materials for the encapsulating layer to enhance thermal conductivity even further.
The research was recently published in Advanced Materials. The abstract stated:
“Van der Waals interactions in 2D materials have enabled the realization of nanoelectronics with high?density vertical integration. Yet, poor energy transport through such 2D–2D and 2D–3D interfaces can limit a device's performance due to overheating. One long?standing question in the field is how different encapsulating layers (e.g., contact metals or gate oxides) contribute to the thermal transport at the interface of 2D materials with their 3D substrates.
“Here, a novel self?heating/self?sensing electrical thermometry platform is developed based on atomically thin, metallic Ti3C2 MXene sheets, which enables experimental investigation of the thermal transport at a Ti3C2/SiO2interface, with and without an aluminum oxide (AlOx) encapsulating layer.
“It is found that at room temperature, the thermal boundary conductance (TBC) increases from 10.8 to 19.5 MW m−2 K−1 upon AlOx encapsulation. Boltzmann transport modeling reveals that the TBC can be understood as a series combination of an external resistance between the MXene and the substrate, due to the coupling of low?frequency flexural acoustic (ZA) phonons to substrate modes, and an internal resistance between ZA and in?plane phonon modes.
“It is revealed that internal resistance is a bottle?neck to heat removal and that encapsulation speeds up the heat transfer into low?frequency ZA modes and reduces their depopulation, thus increasing the effective TBC.”