Department of Materials Science and Engineering, Yonsei University, 50 Yonsei-ro, Soedaemun-gu, Seoul 03722, Republic of Korea.
Nanoscale. 2018 Sep 27;10(37):17705-17711. doi: 10.1039/c8nr05096a.
Porous silicon nanowires (PSi NWs) responding to red, green and blue lights simultaneously are reported in this study. NWs with a diameter of 120 nm were prepared from p-type Si wafer by metal-catalyst-assisted etching. The NWs produced in this manner had an outer porous region consisting of Si nanocrystals small enough to ensure the quantum confinement effect. Hydrazine treatment passivated the porous region by reduction of the surface oxides and the formation of Si-H bonds. The energy band structure of the porous region was a direct transition type, while the emission/absorption energies corresponded to red (1.94 eV), green (2.24 and 2.44 eV) and blue (2.98 eV) light photons. A device structure prepared by suspending 10 PSi NWs between two Al electrodes by dielectrophoresis generated photocurrents upon exposure to red, green and blue lights. The rising and decay times were both 30 μs and the ratio of photocurrent to dark current was 92.0, 59.8 and 24.4 for the blue, green and red lights, respectively. The device could be bent down to the bending radius of 5 mm without any significant deterioration of the photoresponse performances. Further, the device survived repeated bending and unbending over 10 000 cycles with this bending radius, demonstrating its application potential as a flexible device with multiple-wavelength photosensing capabilities.
本研究报道了一种能同时对红光、绿光和蓝光产生响应的多孔硅纳米线（PSi NWs）。通过金属催化剂辅助刻蚀，从 p 型硅片上制备出直径为 120nm 的 NWs。这种方法制备的 NWs具有一个由足够小的 Si 纳米晶组成的多孔外区，以确保量子限制效应。肼处理通过还原表面氧化物和形成 Si-H 键来钝化多孔区。多孔区的能带结构为直接跃迁型，而发射/吸收能量对应于红光（1.94eV）、绿光（2.24eV 和 2.44eV）和蓝光（2.98eV）光子。通过介电泳将 10 个 PSi NWs 悬浮在两个 Al 电极之间制备的器件结构，在暴露于红光、绿光和蓝光时会产生光电流。上升和下降时间均为 30μs，蓝光、绿光和红光的光电流与暗电流的比值分别为 92.0、59.8 和 24.4。该器件可以弯曲到 5mm 的弯曲半径，而不会对光响应性能产生任何显著的恶化。此外，该器件在 10000 次以上的重复弯曲和非弯曲循环中，在该弯曲半径下仍能幸存，展示了其作为具有多波长光传感能力的柔性器件的应用潜力。
