Department of Chemistry and Chemical Biology, Harvard University , Cambridge, Massachusetts 02138, United States.
Department of Physics, Korea University , Seoul 136-701, Republic of Korea.
Nano Lett. 2016 Jul 13;16(7):4713-9. doi: 10.1021/acs.nanolett.6b02236. Epub 2016 Jun 27.
Semiconductor nanowires and other one-dimensional materials are attractive for highly sensitive and spatially confined electrical and optical signal detection in biological and physical systems, although it has been difficult to localize active electronic or optoelectronic device function at one end of such one-dimensional structures. Here we report a new nanowire structure in which the material and dopant are modulated specifically at only one end of nanowires to encode an active two-terminal device element. We present a general bottom-up synthetic scheme for these tip-modulated nanowires and illustrate this with the synthesis of nanoscale p-n junctions. Electron microscopy imaging verifies the designed p-Si nanowire core with SiO2 insulating inner shell and n-Si outer shell with clean p-Si/n-Si tip junction. Electrical transport measurements with independent contacts to the p-Si core and n-Si shell exhibited a current rectification behavior through the tip and no detectable current through the SiO2 shell. Electrical measurements also exhibited an n-type response in conductance versus water-gate voltage with pulsed gate experiments yielding a temporal resolution of at least 0.1 ms and ∼90% device sensitivity localized to within 0.5 μm from the nanowire p-n tip. In addition, photocurrent experiments showed an open-circuit voltage of 0.75 V at illumination power of ∼28.1 μW, exhibited linear dependence of photocurrent with respect to incident illumination power with an estimated responsivity up to ∼0.22 A/W, and revealed localized photocurrent generation at the nanowire tip. The tip-modulated concept was further extended to a top-down/bottom-up hybrid approach that enabled large-scale production of vertical tip-modulated nanowires with a final synthetic yield of >75% with >4300 nanowires. Vertical tip-modulated nanowires were fabricated into >50 individually addressable nanowire device arrays showing diode-like current-voltage characteristics. These tip-modulated nanowire devices provide substantial opportunity in areas ranging from biological and chemical sensing to optoelectronic signal and nanoscale photodetection.
半导体纳米线和其他一维材料在生物和物理系统中具有高度灵敏和空间限制的电信号和光信号检测的吸引力，尽管在这样的一维结构的一端很难实现有源电子或光电设备功能的定位。在这里，我们报告了一种新的纳米线结构，其中材料和掺杂剂仅在纳米线的一端被调制，以编码有源的两端器件元件。我们提出了一种通用的自下而上的合成方案来制备这种尖端调制纳米线，并以纳米尺度的 p-n 结的合成为例进行了说明。电子显微镜成像验证了设计的 p-Si 纳米线核，具有 SiO2 绝缘内壳和 n-Si 外壳，具有干净的 p-Si/n-Si 尖端结。通过独立接触到 p-Si 核和 n-Si 壳的电流传输测量，在尖端处表现出电流整流行为，而在 SiO2 壳处没有可检测到的电流。电导对水栅电压的电测量也表现出 n 型响应，脉冲栅实验产生了至少 0.1ms 的时间分辨率，并且在离纳米线 p-n 尖端 0.5μm 以内的区域内，器件灵敏度高达 90%。此外，光电流实验在约 28.1μW 的光照功率下显示出 0.75V 的开路电压，表现出光电流与入射光照功率的线性关系，估计响应率高达约 0.22A/W，并在纳米线尖端显示出局部光电流产生。尖端调制的概念进一步扩展到自上而下/自下而上的混合方法，该方法能够大规模生产具有最终合成产率>75%和>4300 根纳米线的垂直尖端调制纳米线。垂直尖端调制的纳米线被制成>50 个可单独寻址的纳米线器件阵列，显示出二极管型电流-电压特性。这些尖端调制的纳米线器件在从生物和化学传感到光电信号和纳米级光探测的各个领域都提供了很大的机会。
