Transmission Electron Holography of Polymer Microstructure
Abstract
This is the final report describing a four year effort to develop and apply phase contrast imaging based on transmission electron holography as a means to measure unstained multiphase polymer microstructure. The experiments involve a 200keV transmission electron microscope with a high-coherence field emission electron source. A Mollenstadt biprism was constructed and installed to perform holographic interference experiments, and a slow-scan CCD camera was installed to provide for linear and fully digital hologram recording. A technique was developed to measure the average electron-optical refractive index characteristic of amorphous polymers. This method exploited the model spherical geometry of tilde 50nm diameter polymer latexes. This geometry enabled specimen thickness to be decoupled from the refractive effects of the material as measured by characteristic phase shifts imparted on an incident electron wave. The key quantity involved in the average refraction is known as the mean inner potential (MIP). The MIP for polystyrene was determined experimentally and agrees with predictions of simple models based on electrostatic properties of the polymer. Similar measurements were made on amorphous and crystalline silicon nanospheres yielding a MIP in excellent agreement with LDA calculations of Spence et al. at ASU. Simulations of holographic phase imaging of two-phase polymer microstructure were performed which indicate that the technique is sufficiently sensitive to distinguish between subtly different polymeric materials where no amplitude contrast can be observed.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 24, 1998
- Accession Number
- ADA344467
Entities
People
- Matthew R. Libera
Organizations
- Stevens Institute of Technology