Patterned electron probes enhance precision in measuring tungsten diselenide lattice parameters. Background: complex-shaped electron probe. Foreground: exaggerated diffraction peak changes due to temperature-induced lattice expansion. [Los Alamos]
The research, published in ACS Nano, focuses on materials that are only a few atoms thick, known as two-dimensional materials. These are crucial for advancing microelectronics technology. Until now, measuring how these materials expand with heat has been difficult, leading to inconsistent results.
Atomic-scale weirdness
Theresa Kucinski, a scientist at Los Alamos, explains: “It’s well understood that heating a material usually results in expansion of the atoms arranged in the material’s structure,” said Theresa Kucinski, scientist with the Nuclear Materials Science Group at Los Alamos, in a press release. “But things get weird when the material is only one to a few atoms thick.”
Unravelling such weirdness calls for creativity. In their research, the scientists used a microscopy technique called four-dimensional scanning transmission electron microscopy combined with a non-circular electron beam and complex computational analysis.
The paper, published in, describes describes how the combination of tools jointly helped determine that the thermal expansion of two-dimensional tungsten diselenide is surprisingly similar to that of its bulk counterpart, a finding that has positive implications for incorporating this material into future microelectronics.
The researchers determined specific values for the thermal expansion coefficients of tungsten diselenide. These coefficients quantify how much the material expands when heated. The study found in particular that:
In-plane thermal expansion coefficient: (3.5 ± 0.9) × 10-6 K-1
Out-of-plane thermal expansion coefficient: (5.7 ± 2) × 10-5 K-1
The measurements demonstrate that the thermal expansion of two-dimensional tungsten diselenide is comparable to its bulk counterpart.
Taming the heat in ever-shrinking electronics
This discovery is relevant because of the critical role heat management plays in microelectronics. Tungsten diselenide, a semiconductor material with significant potential for next-generation microelectronics, is a compound semiconductor material belonging to the family of transition metal dichalcogenides (TMDs). Some of its current applications include photovoltaic cells, photodetectors, field-effect transistors, and lubricants.
To investigate tungsten diselenide’s properties at the atomically thin level, the researchers grew a layer of this material, just a few atoms thick (technically described as “nominally monolayer”), on a two-inch silicon wafer coated with silicon dioxide using a chemical process involving heat and gases.
During the experiment, the sample was heated, ranging from room temperature (18 °C) up to 564 °C. The microscope captured thousands of diffraction patterns at each temperature, which were then analyzed to reveal how the material’s structure changed in response to heating.
Promise for two-dimensional tungsten diselenide
This research is particularly relevant for computer chips and other small electronic devices. These components generate heat during operation, which can affect their performance and lifespan. Understanding how materials behave under these conditions is crucial for designing more reliable and efficient devices.
In a press release, Michael Pettes, a scientist with the Center for Integrated Nanotechnologies (CINT), Materials Physics and Applications Division, Los Alamos National Laboratory, noted that the research on two-dimensional tungsten diselenide is “promising as the value is similar to that of conventional materials used in the existing semiconductors integral to microelectronics.”
This is very exciting, and a tremendous discovery. Having retired from the management field of Nuclear Power, my familiarity with the various metals such as Monel, Inconel and stainless to metion a few were used plentifully in the primary system of our two plants. The research you have done to acheive this discovery will prove to be very important in the Nuclear Power Industry.