Surface-controlled deposition of Sc2O3 thin films by atomic layer epitaxy using β-diketonate and organometallic precursors

Scandium oxide thin film deposition by atomic layer epitaxy was studied at 175-500 degreesC using Sc(thd)(3) (thd = 2,2,6,6-tetramethyl-3,5-heptanedione) and (C5H5)(3)Sc as scandium precursors. A constant deposition rate of 0.125 Angstrom (cycle)(-1) was observed at 335-375 degreesC on Si(100) and soda lime glass substrates with Sc(thd)(3) and O-3. The use of H2O2 as an additional oxidizer slightly increased the deposition rate to 0.14 Angstrom (cycle)(-1). When (C5H5)(3)Sc and H2O were used as precursors, the growth rate Of Sc2O3 was significantly higher, viz., 0.75 Angstrom (cycle)(-1) at 250-350 degreesC. The effects of growth parameters such as reactant pulsing times were investigated in detail to confirm the surface-controlled growth mechanism. The crystallinity and surface morphology of the films were characterized by XRD and AFM, while ion-beam analysis (time-of-flight elastic recoil detection analysis) was used to determine the stoichiometry and impurity levels. Crystalline thin films with (111) as the dominant orientation were obtained on Si(100) when depositions Were carried out at 300 degreesC or above from Sc(thd)(3) and O-3 precursors, while films deposited from (C5H5)(3)Sc and H2O were polycrystalline regardless of the deposition temperature. When films were deposited at 300 degreesC onto Si(100), the preferred orientation changed from (111) to (100) when the film thickness exceeded 200 nm. Films were stoichiometric when deposited from Sc(thd)(3)/O-3 below 450 degreesC or from (C5H5)(3)Sc/H2O at 250 degreesC or above. When the films were deposited from Sc(thd)(3)/O-3, the carbon content was below 0.1 atom % regardless of the deposition temperature, whereas the hydrogen content decreased to below 0.1 atom % when the deposition temperature was increased to 375 degreesC. The C and H contents of the films, deposited from (C5H5)(3)Sc/H2O at 300-400 degreesC, were around 0.1 and 0.5-0.3 atom %, respectively.