Characterization of Lanthanum-Aluminum Oxide Thin Films Deposited by Spray Pyrolysis

The optical, electrical, and structural characteristics of lanthanum-aluminum oxide thin films deposited by ultrasonic spray pyrolysis are presented.The films were deposited using a lanthanum nitrate and aluminum acetylacetonate solution in N, N-dimethylformamide on (100) Si substrates.The substrate temperature during deposition was in the 500-650 • C range.The deposition activation energy was in the range of 17.4-20 kJ mol -1 , depending on the relative concentration of lanthanum to aluminum in the precursor solution.The films were amorphous even at 650 • C and they were given no further temperature annealing.The refractive index at 630 nm was in the range of 1.70-1.755depending on the amount of lanthanum in the films.The electrical characteristics of the films were determined from capacitance and current versus voltage measurements of metal-oxide-semiconductor (MOS) structures incorporating them.A dielectric constant in the range of 5.2-10, and interface states density of the order of 10 11 -10 12 eV -1 cm -2 were measured.Their electrical breakdown field was in the range of 4.5-7.6MVcm -1 for films deposited at 500 and 550 • C and a thickness under 43 nm.