Photoemission Study on the Formation of Mo Contacts to CuInSe2

Synchrotron radiation soft-x-ray photoemission spectroscopy was used to investigate the development of the electronic structure at the Mo/CuInSe ₂ interface. Mo overlayers were e-beam deposited in steps on single-crystal n-type CuInSe₂ at ambient temperature. Photoemission measurements were acquired after each growth in order to observe changes in the valence-band electronic structure as well as changes in the In 4d, Se 3d, and Mo 4d core lines. Photoemission measurements on the valence-band and core lines were also obtained after annealing. The results were used to correlate the interface chemistry with the electronic structure at this interface and to directly determine the maximum possible Schottky barrier height φ_b to be ≤0.2 eV at the Mo/CuInSe₂ junction before annealing, thus showing that this contact is essentially ohmic.