Scientists at the National Institute of Standards and Technology’s Physical Measurement Laboratory have succeeded in measuring the thermal conductivity for the first time of an ultra-thin material that is expected to play a major role in the developing field of nanoelectronics.
Molybdenum disulfide, also known as molybdenite or “moly” for short, is a 2D material that measures only a few nanometers thick. Similar to graphene, another 2D material that boasts high electrical and thermal conductivity and strength, molybdenite was examined as a potential alternative to the wonder material in electronic devices because its “intrinsic rather than engineered band gap” gave it “an edge as a transistor material.” Ultimately, interest in molybdenite waned because of its “less-than-ideal electron mobility and sub-threshold slope,” but researchers continued to examine the material’s potential for certain applications.
Now, researchers for the first time have measured the material’s thermal conductivity, a key piece of information needed in order to integrate the material properly into electronic devices, says Angela Hight Walker of PML’s Semiconductor and Dimensional Metrology Division.
“At the time we began our study, little was known about the thermal properties of this material, and yet that information is crucially important,” Hight Walker said. “Measurement of thermal conductivity is an absolutely critical step in the evaluation of a material for applications in electronics—or anywhere else, for that matter.”
Hight Walker, along with her colleagues measured molybdenite’s thermal conductivity using a technique known as Raman spectroscopy, which involves shining monochromatic laser light onto a sample of the material and detecting the scattered light. The frequency of the scattered light varies depending on the way the material stretches and vibrates; these vibrations can be affected by temperature during imaging.
Two different techniques were used to study the effect of temperature on the material: in one case, the researchers heated the sample environment, while in the other the power of the laser directed onto the sample was increased.
Ultimately, the researchers found that while moly is about 100 times less efficient than graphene at conducting heat, it still exhibits a thermal response that can be modeled fairly well, a breakthrough that may lead to faster incorporation of the material into future applications.
“By understanding what its properties are, we can match it with applications to leverage the wonder of the material,” Hight Walker said.
