Controlling Semiconducting and Insulating States of SnO2 Reversibly by Stress and Voltage

By applying mechanical stress (by bending a flexible substrate) and an appropriate voltage, the conductance of a single-crystal SnO2 microrod on a flexible substrate can be tuned in a reversible and nonvolatile manner. The creation and elimination of lattice defects controlled by strain and electrical healing is the origin of this novel transition. A SnO2 microrod changes continually from its normal semiconducting state to an insulating state by bending the flexible substrate. The insulating state is maintained even after straightening the substrate. Interestingly, by applying an appropriate voltage, the defects are electrically healed and the insulating state reverts to the original semiconducting state. The structural changes in the SnO2 microrod observed in the Raman spectra are consistent with the nonvolatile property of the transport. This flexible SnO2 device with the reversible and nonvolatile modification of electrical properties is expected to lead to a better understanding of the mechanism of defect creation and elimination and has potential application in novel flexible strain sensors and switches.