Characterization of Molybdenum Oxide Thin Films Grown by Atomic Layer Deposition

Molybdenum oxide (MoO3) thin films have been deposited using plasma-enhanced atomic layer deposition with molybdenum hexacarbonyl (Mo(CO)6) and oxygen plasma. Self-limiting growth was verified at a deposition temperature of 162°C and the growth rate was determined to be 0.76 Å/cycle. It was found that the as-deposited amorphous thin films crystallized into β- or α-MoO3 during annealing temperatures from 300°C to 400°C in air. In addition, the optical bandgap (Eg) of the amorphous MoO3 was estimated to be 4 eV by transmittance spectral analysis. Moreover, metal-insulator–semiconductor capacitors based on p-type (100) silicon substrates were fabricated to investigate the electrical properties of MoO3. It was shown that the MoO3 thin films exhibit a good dielectric performance and that the dielectric constant of the amorphous MoO3 was determined to be about 17. Additionally, a low leakage current of 6.43 × 10−7 A/cm2 at 1 V was detected and the equivalent oxide thickness was calculated to be 10.5 nm. As a result, MoO3 thin films, as a new high-κ gate dielectrics system, might be a good candidate for metal-insulator–semiconductor field-effect transistors based on two-dimensional transition metal dichalcogenides, especially for metal oxide semiconductor field-effect transistors using molybdenum disulfide (MoS2) as channel material.