Growing multilayered chips; atomic-scale diamond processing; memristor effect in OFET.
Researchers from MIT, Samsung Advanced Institute of Technology, Sungkyunkwan University, and University of Texas at Dallas developed a method to fabricate a multilayered chip with alternating layers of semiconducting material grown directly on top of each other. The approach enables high-performance transistors and memory and logic elements on any random crystalline surface, eliminating the need for silicon wafer substrates.
The method borrows the edge nucleation technique from metallurgy, in which molten material at the edge of a mold forms the grains that become the crystal structure with less energy and heat. This enables it to work at temperatures low enough to preserve the underlying layer’s circuitry.
The researchers used the method to fabricate a multilayered chip with alternating layers of two different TMDs: molybdenum disulfide for n-type transistors, and tungsten diselenide for p-type transistors. The team was able to grow both materials in single-crystalline form, directly on top of each other, without requiring any intermediate silicon wafers.
“A product realized by our technique is not only a 3D logic chip but also 3D memory and their combinations,” said Jeehwan Kim, associate professor of mechanical engineering at MIT, in a press release. “With our growth-based monolithic 3D method, you could grow tens to hundreds of logic and memory layers, right on top of each other, and they would be able to communicate very well.” [1]
Researchers from Macquarie University developed a technique for atomic-scale surface processing of diamonds that allows for the controlled removal of as little as 1% of a single atomic layer.
The method uses pulsed deep ultraviolet laser light to trigger localized chemical reactions on the diamond surface. The reaction, driven by a two-photon process, removes carbon atoms selectively from the top atomic layer.
This processing resulted in an increase of up to seven times in diamond surface conductivity, a step toward the creation of diamond-based semiconductors for high-power, high-frequency electronics. The researchers also noted that its speed, with the ability to remove 1% of a monolayer in 0.2 milliseconds, makes it feasible for industrial-scale wafer processing. [2]
Researchers from Johns Hopkins University created a memristor effect in pentacene organic FETs. During experiments to understand what happens during transistor charging, the team introduced a molecule called dibenzo tetrathiafulvalene (DBTTF) to the transistors, which forms crystals within the transistor’s insulating layer.
After injecting a small current across the modified transistor, they noticed that the transistor retained its past charge, acting as a memristor.
“Usually, transistors don’t retain previous charges when recharged. This one adjusted based on the previous charge, indicating a memory-like function,” said Riley Bond, a graduate student at Johns Hopkins, in a release. “We are now exploring other transistors we’ve experimented with, looking for memristor behavior and investigating if those transistors could be used in this new technology.” [3]
[1] Kim, K.S., Seo, S., Kwon, J. et al. Growth-based monolithic 3D integration of single-crystal 2D semiconductors. Nature 636, 615–621 (2024). https://doi.org/10.1038/s41586-024-08236-9
[2] Moshkani, M., Geis, M. W., Downes, J. E., Mildren, R. P., The effects of sub-monolayer laser etching on the chemical and electrical properties of the (100) diamond surface, Applied Surface Science, Volume 684, 2025. https://doi.org/10.1016/j.apsusc.2024.161816
[3] C. R. Bond, D. H. Reich, H. E. Katz, Increased Static Charge-Induced Threshold Voltage Shifts and Memristor Activity in Pentacene OFETs Comprising Polystyrene-Based Gate Dielectrics Containing Electroactive Small Molecule Crystallites. Adv. Funct. Mater. 2024, 34, 2410763. https://doi.org/10.1002/adfm.202410763
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