Energy level evolution of air and oxygen exposed molybdenum trioxide films

The evolution of electronic energy levels of controlled air and oxygen exposed molybdenum trioxide (MoO3) films has been investigated with ultraviolet photoemission spectroscopy, inverse photoemission spectroscopy, and x-ray photoemission spectroscopy. We found that while most of the electronic levels of as deposited MoO3 films remained largely intact, the reduction in the work function (WF) was substantial. The gradual surface WF change from 6.8 to 5.3 eV was observed for air exposed film, while oxygen exposed film the surface WF saturated at similar to 5.7 eV. Two distinct stages of exposure are observed, the first dominated by oxygen adsorption for < 10(13) Langmuir (L) exposure and at the final step moisture absorption >10(13) L. (C) 2010 American Institute of Physics. [doi:10.1063/1.3454779]