Electron holography characterization as a method for measurements of diameter and mean inner potential of hollow nanomaterials.

In this paper, we provide a method for the simultaneous measurement of the inner diameter of nanotubes with a regular shape and calculation of their mean inner potential (MIP) using electron holography. This method contains 4 steps: (i)phase profile characterization from electron holography; (ii) shape assumption from prepared data; (iii) thickness simulation from a shape assumption and fitting method; (iv) calculation of MIP of the simulated and fitted parameters. By this method, as an example, the shape and the outer and inner diameters of a tube formed from C(60) molecules were characterized. The MIP of the tube was also calculated through this method. The MIP calculation from another nano whisker formed from C(60) molecules supports the feasibility of our method and it could be extended to other nanomaterials. This work provides a convenient method for morphology characterization of hollow nanomaterials, such as diameter measurements and cross-sectional shape determination, which are the most basic and important characteristics of the nanomaterials. In addition, it also provides a method for MIP calculation without a thickness measurement if the samples have relatively regular shapes. Thus this method should be more convenient for closely combining the tomography and physical properties of samples, which could be essential for in situ TEM studies of nanomaterials.