High temperature oxidation of CoAl(1 0 0)

We have employed Auger electron spectroscopy (AES), high resolution electron energy loss spectroscopy (EELS), low energy electron diffraction (LEED) and scanning tunneling microscopy (STM) to investigate the growth of an Al2O3 film on CoAl(1 0 0). While exposure to oxygen at room temperature leads to the formation of amorphous alumina, subsequent annealing at higher temperatures results in the growth of well-ordered θ-Al2O3. Well-ordered Al2O3 films are also formed by oxidation at temperatures of 800 K and above. The oxide is characterized by Fuchs–Kliewer modes at around 430, 630, 780 and 920 cm−1. Oxide islands grow in two sets of domains perpendicular to each other. Under ultra-high vacuum conditions, self-limiting thickness of the oxide layer (9–10 Å) has been found. The band gap of the θ-Al2O3 film on CoAl(1 0 0) is 4.3–4.5 eV.