Internal photoemission experiments

Internal photoemission experiments have been performed on polymers in an LED architecture the measurements give access to the energy difference between the electron and hole injections and thus the energy gap for creation of two polarons of opposite charge. The data provide a value of 2.45 eV in the case of poly(2-methoxy-5 -(2 - ethyl - hexyloxy)paraphenylenevinylene), MEH -... 

The internal photoemission measurements appear to be on solid ground, but more detailed investigations, including the field dependence on well-characterized interfaces, would be important. Other experiments such as transient photoconductivity have been applied to depletion-layer profiling, and these appear to be quite useful. 

Photoemission experiments under applied external pressure are difficult to perform. (3ne can, however, simulate the external pressure by forming alloys with a reduced lattice constant which can be thought of as producing an internal pressure. This can, e.g., be achieved by substituting some of the Sm ions by Th ions. If 10% of the Sm ions are replaced by Th ions, the same sort of phase transition, which can be induced by external pressure, is observed. 

Accompanying the photoemission process, electron reorganisation can result in the ejection of a photon (X-ray fluorescence) or internal electronic reorganisation leading to the ejection of a second electron. The latter is referred to as the Auger process and is the basis of Auger electron spectroscopy (AES). It was Harris at General Electric s laboratories at Schenectady, USA, who first realised that a conventional LEED experiment could be modified easily to... 

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