Interface formation of pentacene on Al2O3

Abstract
We examined the interface formed by pentacene deposition onto an Al 2 O 3 substrate. We found that upon pentacene deposition onto Al 2 O 3 the pentacene vacuum level aligns with that of Al 2 O 3 . We observe the immediate appearance of a measurable pentacene molecular orbital near the Fermi level upon deposition of as little as 2 Å of pentacene onto the Al 2 O 3 surface. This suggests that there are no chemical bonds at this interface. The vacuum level change at the interface dipole is found to be less than 0.25 eV, and at least part of it can be attributed to the oxygen adsorbates at the in situ prepared aluminumoxide surface.