Nanocrystalline Lanthanum Oxide Layers on Tubes Synthesized Using the Metalorganic Chemical Vapor Deposition Technique

Lanthanum oxide (La₂O₃) layers are widely used in electronics, optics, and optoelectronics due to their properties. Lanthanum oxide is also used as a dopant, modifying and improving the properties of other materials in the form of layers, as well as having a large volume. In this work, lanthanum oxide layers were obtained using MOCVD (Metalorganic Chemical Vapor Deposition) on the inner walls of tubular substrates at 600-750 °C. The basic reactant was La(tmhd)₃ (tris(2,2,6,6-tetramethyl-3,5-heptanedionato)lanthanum(III)). The evaporation temperature of La(tmhd)₃ amounted to 170-200 °C. Pure argon (99.9999%) and air were used as the carrier gases. The air was also intended to remove the carbon from the synthesized layers. Tubes of quartz glass were used as the substrates. La₂O₃ layers were found to be growing on their inner surfaces. The value of the extended Gr_x/Re_x² criterion, where Gr-Grashof's number, Re-Reynolds' number, x-the distance from the gas inflow point, was below 0.01. The microstructure of the deposited layers of lanthanum oxide was investigated using an electron scanning microscope (SEM). Their chemical composition was analyzed via energy-dispersive X-ray (EDS) analysis. Their phase composition was tested via X-ray diffraction. The transmittance of the layers of lanthanum oxide was determined with the use of UV-Vis spectroscopy. The obtained layers of lanthanum oxide were characterized by a nanocrystalline microstructure and stable cubic structure. They also exhibited good transparency in both ultraviolet (UV) and visible (Vis) light.