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

Abstract

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 1.70–1.755 depending 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 1011-1012 eV−1 cm−2 were measured. Their electrical breakdown field was in the range of 4.5–7.6 MVcm−1 for films deposited at 500 and 550°C and a thickness under 43 nm.

Enhancement of Gamma-ray Shielding Properties in Cobalt-Doped Heavy Metal Borate Glasses: The Role of Lanthanum Oxide Reinforcement

“…These factors reduce the k value and generate a positive fixed charge, resulting in deterioration of its dielectric properties [8,9]. Therefore, adding other elements to La 2 O 3 will improve its properties; previous studies used silicon, aluminum, and nitrogen to enhance the chemical and electrical characteristics [10,11]. Nevertheless, La 2 O 3 is a possible candidate for modifying the physical and optical properties of glasses and glass-ceramics.…”

Spectroscopic properties of oxygen vacancies inLaAlO3

“…[4] to be 5.84-6.33 eV depending on film thickness. It is possible that these films have a pseudo-cubic crystalline structure as they were annealed at 900 • C, i.e., well above the 650 • C, which other groups have determined is necessary for amorphous films to become crystalline [24,26,27].…”

“…When grown as a thin supported film, rhombohedral LAO is considered to be pseudocubic [25], with oxygen octahedra rotations in an antiphase order. However, in order to achieve a crystalline, as opposed to amorphous, thin film of LAO, annealing at or above 650°C is required [24,26,27], which is above the rhombohedral to cubic phase transition temperature. It is understood that details of the LAO structure in thin films and multi-layered hetero-structures depend on the lattice and polarity mismatch with the substrate and over-layers.…”