Much recent attention has been focused on the development of field-effect transistors based on low-dimensional nanostructures for the detection and manipulation of molecules. Because of their extraordinarily high charge sensitivity, InAs nanowires present an excellent material system in which to probe and study the behavior of molecules on their surfaces and elucidate the underlying mechanisms dictating the sensor response. So far, chemical sensors have relied on slow, activated processes restricting their applicability to high temperatures and macroscopic adsorbate coverages. Here, we identify the transition into a highly sensitive regime of chemical sensing at ultralow concentrations (<1 ppm) via physisorption at room temperature using field-effect transistors with channels composed of several thousand InAs nanowires and ethanol as a simple analyte molecule. In this regime, the nanowire conductivity is dictated by a local gating effect from individual dipoles, leading to a nonlinear enhancement of the sensitivity. At higher concentrations (>1 ppm), the nanowire channel is globally gated by a uniform dipole layer at the nanowire surface. The former leads to a dramatic increase in sensitivity due to weakened screening and the one-dimensional geometry of the nanowire. In this regime, we detect concentrations of ethanol vapor as low as 10 ppb, 100 times below the lowest concentrations previously reported. Furthermore, we demonstrate electrostatic control of the sensitivity and dynamic range of the InAs nanowire-based sensor and construct a unified model that accurately describes and predicts the sensor response over the tested concentration range (10 ppb to 10 ppm).

中文翻译：

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超低浓度条件下纳米线的非线性化学敏感性增强。

最近的许多注意力集中在基于低维纳米结构的场效应晶体管的开发上，以用于分子的检测和操纵。由于其极高的电荷敏感性，InAs纳米线提供了一种出色的材料系统，可在其中探测和研究分子在其表面上的行为，并阐明指示传感器响应的潜在机制。到目前为止，化学传感器依赖于缓慢的激活过程，从而限制了它们对高温和宏观吸附物覆盖范围的适用性。在这里，我们确定了在超低浓度（< 在室温下使用场效应晶体管通过物理吸附进行1 ppm的物理吸附，该晶体管具有由几千个InAs纳米线和乙醇作为简单分析物分子组成的通道。在这种情况下，纳米线的电导率由各个偶极子的局部选通效应决定，从而导致灵敏度的非线性增强。在更高的浓度（> 1 ppm）下，纳米线通道被纳米线表面上的均匀偶极子层整体选通。前者由于屏蔽作用减弱和纳米线的一维几何结构而导致灵敏度急剧增加。在这种情况下，我们检测到的乙醇蒸气浓度低至10 ppb，比先前报道的最低浓度低100倍。此外，