功能纳米器件中组成材料间的电荷转移输运过程对于器件中的物理化学过程以及由此引发的器件功能会有重大影响,因此,深入理解器件工作过程中的电子/离子行为机理对于优化器件功能以及进一步开发纳米材料的应用潜力具有重要意义.传统场效应晶体管对于纳米材料的电输运测量表征反映了载流子在整个器件中的统计行为,但难以检测电荷具体的转移输运过程.同时,由于纳米材料的尺寸和分散性,基于纳米材料的场效应晶体管面临着制备困难、电极/纳米材料接触复杂和制作成本高等问题.因此,本课题组发展了介电力显微术(dielectric force microscopy,DFM)方法并实现了对纳米材料电学性质的无接触、高空间分辨率和快速表征.本文介绍了介电力显微术的基本原理,列举了其在探究一维纳米材料、纳米颗粒以及有机半导体薄膜电学性质上的一些应用实例.这些实例验证了介电力显微术对纳米材料电学性质的表征能力,并展现了这一技术在纳米材料物理化学性质和纳米器件功能研究上的广阔前景.
Characterization of electric properties of nanomaterials usually involves fabricating field effect transistors （FET） and deriving materials properties from device performances. However, the quality of electrode contacts in FET devices heavily influences the device performance, which makes it difficult to obtain the intrinsic electric properties of nanomaterials. Dielectric force microscopy （DFM）, a contactless method developed recently, can detect the low-frequency dielectric responses of nanomaterials without electric contact, which avoids the influence of electric contact and can be used to study the intrinsic conductivity of nanomaterials. Here we study the influences of surface adsorbates on the conductivity of ZnO nanowires （NWs） by using FET and DFM methods. The conductivity of ZnO NW is much larger in N2 atmosphere than that in ambient environment as measured by FET device, which is further proven by DFM measurement that the ZnO NW exhibits larger dielectric response in N2 environment, and the influence of electrode contacts on measurement can be ruled out. Based on these results, it can be concluded that the adsorbates on ZnO NW surface highly influence the conductivity of ZnO NW rather than the electrode contact. This work also verifies the capability of DFM in measuring electric properties of nanomaterials.
