MEASUREMENT OF POLYSTYRENE MEAN INNER POTENTIAL BY TRANSMISSION ELECTRON HOLOGRAPHY OF LATEX SPHERES

This study describes the use of transmission electron holography to de termine the mean inner potential of polystyrene. Spherical nanoparticl es of amorphous polystyrene are studied so that the effect of specimen thickness on the phase shift of an incident electron wave can be sepa rated from the intrinsic refractive properties of the specimen, A recu rsive four-parameter X-squared minimization routine is developed to de termine the sphere center, radius, and mean inner potential (Phi(0)) a t each pixel in the phase image. Because of the large number of pixels involved, the statistics associated with determining a single Phi(0) value characteristic of a given sphere are guile good. Simulated holog rams show that the holographic reconstruction procedure and the chi-sq uared analysis method are robust. Averaging the Phi(0) data derived fr om ten phase images from ten different polystyrene spheres gives a val ue of Phi(0)(PS) = 8.5 V (sigma) = 0.7 V). Specimen charging and elect ron-beam damage, if present, affect the measurement at a level below t he current precision of the experiment.