Stretchable field-effect-transistor array of suspended SnO₂ nanowires.

Recently, various future devices including microelectronics and bioimplantable devices have been designed as curvilinear layouts on curved or stretchable surfaces of skin or organs. [ 1–4 ] Silicon and polymer-based organics have been used primarily for commercial fl at/rigid electronics and for curvilinear fl exible/stretchable electronics. [ 2 , 5 ] However, 1D materials such as nanowires (NWs) are expected to be advantageous in future, stretchable electronics, exhibiting increased performance and better integration due to their superior electronic properties and structurally high aspect ratios. [ 6 ] In this work, we report the fabrication of high-performance, stretchable, electronic devices with suspended NWs, which demonstrate great potential for applications in wearable or bioimplantable devices. Diluted poly-amic acid solution was spin-coated onto a common SiO 2 /Si substrate and annealed following the previously reported recipe [ 1 ] to make an approximately 300 nmthick polyimide (PI) layer, as shown in Scheme 1 . Because of the very low adhesion between SiO 2 ( γ ≈ 0.2 J m − 2 ) [ 7 ] and PI ( γ ≈ 37.4 mJ m − 2 ), [ 8 ] the fi rst polyimide layer was coated underneath the device for easy detachment. After deposition and patterning of the gate electrode, the second polyimide layer also was spin-coated on the bottom-gate as a temporary gate insulator. Thus, the gate metal electrodes were encapsulated by two PI layers, which place the metal interconnects in a nearly neutral mechanical plane to minimize expansive/compressive strain. [ 1 ] SnO 2 NWs were synthesized by chemical vapor deposition (CVD) and transferred onto a photoresist prepatterned substrate via a sliding transfer technique. [ 9 ] Au was evaporated to fabricate the source and drain electrodes, which defi ne the channel length and width of 5 and 160 μ m, respectively. To improve the deformability and to reduce strain in the devices, the metal interconnects were Stretchable Field-Effect-Transistor Array of Suspended SnO 2 Nanowires