A self-assembled two-dimensional hypersonic phononic insulator

The coupling between the electromagnetic field and the motional degrees of freedom of a nanoscale object offers an interesting control-knob for light–matter interaction. However, this interaction is rather weak so, in general, a precise control over the mechanical vibrations of the object becomes desirable for enhancing and fine-tuning this coupling. Phonon insulation is a base-line to achieve nanoscale vibration control by inducing constructive and destructive phonon interference, which opens phononic band gaps at various frequencies. Phonon insulators are essential for managing and directing mechanical vibrations in advanced mechanical systems, such as resonators and acousto-optic modulators. Conventional fabrication methods, such as electron-beam lithography, are highly robust and efficient but also very demanding and limited in accessibility due to their cost and technical requirements. Self-assembly offers an alternative route for fabricating mechanical structures from diverse materials, allowing for innovative designs with improved functionalities. By using natural self-organizing processes, production is simplified and accelerated, with components assembling automatically in a low-cost, scalable manner. Here, we present a simple self-assembled device that functions as a phonon insulator in the GHz frequency range and can be easily integrated onto silicon. This integration opens the door to a wide range of applications, including optical communication, quantum computing, and ultra-sensitive sensors, where efficient control over mechanical vibrations is vital.