Centre of Super-Diamond and Advanced Films (COSDAF) and Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR, China.
ACS Nano. 2010 Jun 22;4(6):3045-52. doi: 10.1021/nn1001613.
p-Type surface conductivity is a uniquely important property of hydrogen-terminated diamond surfaces. In this work, we report similar surface-dominated electrical properties in silicon nanowires (SiNWs). Significantly, we demonstrate tunable and reversible transition of p(+)-p-i-n-n(+) conductance in nominally intrinsic SiNWs via changing surface conditions, in sharp contrast to the only p-type conduction observed on diamond surfaces. On the basis of Si band energies and the electrochemical potentials of the ambient (pH value)-determined adsorbed aqueous layer, we propose an electron-transfer-dominated surface doping model, which can satisfactorily explain both diamond and silicon surface conductivity. The totality of our observations suggests that nanomaterials can be described as a core-shell structure due to their large surface-to-volume ratio. Consequently, controlling the surface or shell in the core-shell model represents a universal way to tune the properties of nanostructures, such as via surface-transfer doping, and is crucial for the development of nanostructure-based devices.
p 型表面电导率是氢化金刚石表面的一个独特的重要特性。在这项工作中，我们报告了在硅纳米线（SiNWs）中类似的表面主导的电特性。值得注意的是，我们通过改变表面条件，在名义上本征 SiNWs 中展示了可调节和可逆的 p(+)-p-i-n-n(+)电导转变，与在金刚石表面上仅观察到的 p 型传导形成鲜明对比。基于 Si 能带能量和环境（pH 值）确定的吸附水层的电化学势，我们提出了一个电子转移主导的表面掺杂模型，该模型可以令人满意地解释金刚石和硅表面的电导率。我们所有的观察结果表明，由于纳米材料具有较大的表面积与体积比，因此可以将其描述为核壳结构。因此，控制核壳模型中的表面或壳层代表了一种调节纳米结构性质的通用方法，例如通过表面转移掺杂，这对于基于纳米结构的器件的发展至关重要。
