The new data narrows the scope of its potential application in microelectronics and at the same time opens up new prospects for the use of 2D materials as catalysts.
MoS2 is considered a promising basis for a variety of ultra-small electronic devices such as high-frequency detectors, rectifiers, and transistors. As a consequence, research teams around the world are actively studying its 2D format, nanofilm. However, the new research conducted by NUST MISIS scientists has demonstrated that when this 2D material is significantly oxidised in air, it turns into another connection.
Any electronic device using MoS2 without proper protection would quickly stop working. To potentially use MoS2 in microelectronics, the devices would have to be encapsulated.
“For the first time ever, we have managed to experimentally prove that a single-layer MoS2 strongly degrades under environmental conditions, oxidsing and turning into a solid solution MoS2-xOx,” says Pavel Sorokin, head of the research team and leading researcher at the NUST MISIS Laboratory of Inorganic Nanomaterials. “The functions of a 2D semiconductor without defects and losses can be implemented with molybdenum diselenides, another material with a similar structure.
In the experiments, 2D layers of MoS2 obtained as a result of the stratification of MoS2 crystals by ultrasound, were maintained in environmental conditions at normal room temperature and lighting for long periods (more than a year and a half), during which scientists observed the changes in the structure of its surface.
“Thanks to the use of tunnelling microscopy, we were able to track the structural changes of crystals of 2D sulfur disulfide at the atomic level during long-term exposure to environmental conditions,” explains Zakhar Popov, one of the co-authors of the study and a senior researcher at the NUST MISIS Laboratory of Inorganic Nanomaterials. “We have discovered that the material previously considered stable is actually subject to spontaneous oxidation, but at the same time, the original crystal structure of MoS2 monolayers retains formations of MoS2-xOx solid solutions.
“Our simulations have allowed us to propose a mechanism of forming such solid solutions, and the results of the theoretical calculations are in complete agreement with our experimental measurements.”
“The study's second key discovery is the new material that the monolayer of the MoS2turns into is a 2D crystal of a solid solution MoS2-xOx, which is an effective catalyst for electromechanical processes,” concludes Sorokin.
