Characterization and electrical properties of high-k GdScO3 thin films grown by atomic layer deposition

Gadolinium scandium oxide (Gd-scandate, GdScO3) thin films were grown by atomic layer deposition (ALD) from beta-diketonate precursors M(thd) (3) (M=Gd, Sc; thd = 2,2,6,6-tetramethyl-3,5-heptanedionato) and ozone. The deposition parameters were optimized to produce films with the stoichiometric 1 : 1 metal ratio and a series of samples with nominal thicknesses of 5, 10, 15, and 20 nm were prepared. At 300 degrees C the metal precursor pulsing ratio Gd : Sc = 5 : 6 yielded amorphous stoichiometric films and a growth rate of 0.21 angstrom/cycle. The films stayed amorphous up to 900 degrees C. The surface was probed with an AFM and the rms roughness was found to be 0.3 nm for the 5-20 nm thick films. The electrical properties of the as-deposited films proved to be very promising, with a dielectric constant of similar to 22 and leakage current density of 340 mu A/cm(2), measured at -2V.