Piezoelectric Bending Measurements: Noise Versus Signals

Many 2-D and 1-D emerging materials have applications as piezoelectric energy generators and as piezotronic materials for intelligent systems. Cyclic straining of the devices on flexible substrates is considered a reliable technique to quantify the direct piezoelectric property. Irrespective of their centrosymmetric nature, many 2-D materials have shown promising electromechanical properties. However, the measured electrical output during bending experiments can originate from different phenomena. It is essential to know if the measured signal is the actual piezoelectric output from the sample or other attributes. The techniques used to perform experiments, the cables, and the substrate itself can generate transient responses to the applied strain that often mimic the piezoelectric response. The output signals from a single 2-D material device are often low level. Therefore, the contribution from electrostatic and triboelectric noise sources often masks the piezoelectric signals. Here, we demonstrate ways to verify the real piezoelectric response from other noise signals. We also provide insight into the polarization direction through open-circuit voltage measurements. The current work focuses on the bending measurements of 2-D material devices. However, the methods are equally applicable to other materials if the testing involves bending experiments.