Scientists at Delft University of Technology have fabricated micromechanical resonators using single-layer molybdenum disulfide. This new monolayer material has great potential for future nanoelectromechanical devices as it combines excellent mechanical and electrical properties. For instance, this material shares the mechanical toughness and reduced dimensions of graphene but (unlike graphene) it is a semiconductor, enabling new applications such as flexible transistors.
The mechanical resonators were fabricated by transferring monolayer molybdenum disulfide onto a silicon wafer previously patterned with holes forming micron-size drumheads that are only three atoms thick. Vibrations of the micro-drumheads are excited using a focusing beam of a modulated blue laser light. The pulsed laser acts as a tiny heater, causing the drums to expand and contract at MHz frequencies. A second continuous red laser is used to sense the drum’s motion using a built-in optical interferometer under the drum.
The TU Delft researchers studied the properties of tens of molybdenum disulfide mechanical resonators, finding resonance frequencies that range from 10 MHz to 30 MHz. Such high frequencies makes these resonators interesting for future nanoelectromechanical devices, a technology that will play an important role in the next generation radio frequency electronic components like the ones used in cell-phones. The team also found that while single-layer resonators behave like tensed membranes similar to a drumhead, thicker membranes behave like elastic discs with negligible tension, gaining a deeper understanding on the dynamics of atomically thin mechanical resonators.