School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245, USA.
ACS Nano. 2013 Feb 26;7(2):1803-10. doi: 10.1021/nn306007p. Epub 2013 Jan 31.
We demonstrated the first piezoelectric effect on the performance of a pH sensor using an MSM back-to-back Schottky contacted ZnO micro/nanowire device. When the device is subjected to an external strain, a piezopotential is created in the micro/nanowire, which tunes the effective heights of the Schottky barriers at the local contacts, consequently increasing the sensitivity and signal level of the sensors. Furthermore, the strain-produced piezopotential along the ZnO micro/nanowire will lead to a nonuniform distribution of the target molecules near the micro/nanowire surface owing to electrostatic interaction, which will make the sensor proactive to detect the target molecules even at extremely low overall concentration, which naturally improves the sensitivity and lowers the detection limit. A theoretical model is proposed to explain the observed performance of the sensor using the energy band diagram. This prototype device offers a new concept for designing supersensitive and fast-response micro/nanowire sensors by introducing an external strain and piezotronic effect, which may have great applications in building sensors with fast response and reset time, high selectivity, high sensitivity, and good signal-to-noise ratio for chemical, biochemical, and gas sensing.
我们使用 MSM 背靠背肖特基接触 ZnO 微/纳线器件展示了 pH 传感器性能上的首个压电效应。当器件受到外部应变时，微/纳线中会产生压电势，从而调整局部接触处肖特基势垒的有效高度，进而提高传感器的灵敏度和信号水平。此外，由于静电相互作用，沿 ZnO 微/纳线产生的应变压电势会导致微/纳线表面附近的目标分子分布不均匀，这会使传感器能够主动检测即使在极低的总浓度下的目标分子，从而自然提高了灵敏度并降低了检测限。我们提出了一个理论模型，通过能带图来解释传感器的观测性能。该原型器件通过引入外部应变和压电器效应，为设计超高灵敏度和快速响应的微/纳线传感器提供了一个新概念，这可能在构建具有快速响应和重置时间、高选择性、高灵敏度和良好信噪比的化学、生化和气体传感器方面具有重要应用。
