Photoelectron Yield Spectroscopy
PYS is a method to measure the ionization energy of materials (work function in the case of metals) by using photoemission process. A sample surface is irradiated by tunable UV light, and the number of emitted photoelectrons is measured. The quantum yield of photoelectron (Y), which is the number of emitted photoelectrons per photon absorbed, is detected as a function of incident photon energy (hν). The principle is shown in Fig. 75.1 for the case of a material with an energy gap. When hν becomes greater than the threshold ionization energy (Ith) during incremental hν scan, the value of Y starts to increase. Thus, by determining the threshold of the spectrum, the value of Ith can be evaluated. In the case of metal sample, the work function of the sample can be deduced in the similar way.
KeywordsIonization energy Work function Photoelectron Environmental measurement Gap states
- 1.Regarding PYS, see the following review articles, and references therein: Ishii, H., Kinjo, H., Sato, T., Machida, S., Nakayama, Y.: Photoelectron yield spectroscopy for organic materials and interfaces, Chap. 8 (pp. 131–155). In: Ishii, H., Kudo, K., Nakayama, T., Ueno, N. (eds.) Electronic processes in organic electronics: bridging nanostructure, electronic states and device properties. Springer (2015)Google Scholar
- 2.Nakayama, Y., Machida, S., Minari, T., Tsukagoshi K., Noguchi, Y., Ishii, H.: Direct observation of the electronic states of single crystalline rubrene under ambient condition by photoelectron yield spectroscopy. Appl. Phys. Lett. 93(17) (2008) 173305-1~3Google Scholar