Scanning photoelectron microscope (SPEM)

Microscope working principle

The geometry of experiment is illustrated on the sketch of the general concept of the microscope, image on the right. The focused beam cone is incident normally to the surface of the sample whereas the emitted photoelectrons are accepted from the direction of 300 with respect to the sample surface. For the present geometry typical escape depth for photoelectrons is 5-10 A, that is the information from only about maximum 10 atomic topmost layers is acquired. The photoelectron spectrum is analyzed with energy dispersive hemispherical analyzer. Thanks to multichannel plate in the analyzer dispersive plane a 48 point photoelectron spectra or images can be acquired simultaneously. Samples should be preferentially conductive as required in photoemission. Anyway one should keep in mind charging if one wants to measure the samples with high resistance. The flux density is extremely high so that one should take care of beam damage effects if planning to experiment with soft matter (organics etc.).

As a result of the experiment one can obtain (i) high resolution photoelectron spectra from surface features and (ii) images of intensity distribution of photoemission components.



Last Updated on Friday, 20 January 2012 15:43