Probe the Effects of Surface Adsorbates on ZnO Nanowire Conductivity using Dielectric Force Microscopy

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 muchlarger 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.