Single Crystal Flexible Electronics Enabled by 3D Spalling

Flexible and stretchable electronics are becoming increasingly important in many emerging applications. Due to the outstanding electrical properties of single crystal semiconductors, there is great interest in releasing single crystal thin films and fabricating flexible electronics with these conventionally rigid materials. In this study the authors report a universal single crystal layer release process, called "3D spalling," extending beyond prior art. In contrast to the conventional way of removing blanket layers from their substrates, the new process reported here enables 3D control over the shape and thickness of the removed regions, allowing direct formation of arbitrarily shaped structures of released film and locally specified thickness for each region. As an exemplary demonstration, silicon flexible tactile sensors are fabricated with sensitivities comparable to those of high performance sensors on rigid substrates. Finite element modeling indicates that the size and thickness of the selectively released features can be tuned over a wide range.