A comparative study on lanthanide oxide thin films grown by atomic layer deposition

Abstract Lanthanide oxide (Ln=Nd, Sm, Eu, Gd, Dy, Ho, Er and Tm) thin films were grown onto silicon (100) substrates by atomic layer deposition (ALD) using volatile β-diketonate-type Ln(thd) 3 (thd=2,2,6,6-tetramethyl-3,5-heptanedione) compounds and ozone as precursors. The depositions were carried out at approximately 300 °C under a reduced pressure of 2–3 mbar. X-ray diffraction studies showed all Ln 2 O 3 films to be cubic (C-type) and polycrystalline. Nd 2 O 3 was observed to contain hexagonal phase as well. Compositional studies by time-of-flight elastic recoil detection analysis (TOF-ERDA) revealed the films to be nearly stoichiometric having carbon, fluorine and hydrogen as impurities. According to the infrared spectroscopy measurements, the carbon contamination in the films was mainly caused by a carbonate-type impurity. Electrical characterization showed that thin films were resistive having relative permittivities between 8.4 and 11.1. Leakage current densities through ca. 50 nm thick Ln 2 O 3 were in the order of 10 −9 –10 −7 A/cm 2 and breakdown field strengths were in the range of 0.4–2.1 MV/cm.