Study On The Structures And Epitaxial Growth Of Gd₂O₃ And Nd₂O₃ Nanofilms

Gd₂O₃ and Nd₂O₃ nanofilms could be relatively good dielectric material in semiconductor integrated circuit, thus attracting widespread attention. This paper deduced a calculation method about quickly determining the included angles of substrate of thin film growth, and the concrete distribution of included angles between substrate and thin film. Then this paper studied growth situations of Gd₂O₃ thin films grown on the Si substrates of different orientations by molecular beam epitaxy method. Mainly, growth situations of Gd₂O₃ and Nd₂O₃ thin films deposited on SrTiO₃ substrates are key research directions. The main research content is as follows:1. A simple calculation method which can be performed with general laboratory facility is deduced for quickly determining the included angles distribution?including miscut angle? between the crystal plane and sample plane for a miscut substrate. This method is based on the rocking curve measurement of High-resolution X-ray diffraction?HRXRD?. After measuring and calculating values of two included angles??1 and ?2? between the crystal plane and sample plane at two arbitrary mutually perpendicular azimuths of the sample plane by HRXRD, all included angles at arbitrary azimuths of the miscut substrate can be easily and quickly calculated. Besides, since original azimuthal measurements of ?1 and ?2 may be situated on different positions of the sample plane, the distributions of miscut angle and azimuthal orientation are deduced and analysed.2. We studied the growth conditions of Gd₂O₃ thin films deposited on Si substrates of different orientations by molecular beam epitaxy technique. The interfaces between the substrates and thin films are all very flat. However, an amorphous oxide layer could be always found between the Gd₂O₃ thin film and the Si substrate under different growth conditions. We analysed forming reasons of amorphous oxide layer and impacts on the crystallization performance of thin film. In order to investigate crystallinity properties of Gd₂O₃ nanofilm, the original monocrystalline silicon is replaced with monocrystalline SrTiO₃. It turned out that Gd₂O₃ nanofilm can be epitaxial growth well on SrTiO₃?100? substrate by MBE.3. We studied the growth conditions of Gd₂O₃ thin films deposited on SrTiO₃?100? substrate by molecular beam epitaxy technique. XRD analysis, conventional TEM and STEM are performed to investigate the crystal structure and orientation of thin films. The experiment proved that the annealing of higher temperature is conducive to get single crystal thin film of higher quality on the substrate. Gd₂O₃ thin film grows epitaxially on the SrTiO₃?100? substrate with?001?Gd₂O₃//?100?STO and [110]Gd₂O₃//[001]STO orientations. Furthermore, the Gd atoms are found to diffuse into the SrTiO₃ substrate for a depth of one unit cell and substitute for the Sr atoms near the interface.4. We studied the growth conditions of Nd₂O₃ thin films deposited on SrTiO₃?100? substrate by molecular beam epitaxy technique. Nd₂O₃ was found to have high-quality structure and its crystal structure and lattice constant was very similar to Gd₂O₃. However, Nd₂O₃ has a smaller degree of mismatch than Gd₂O₃, the value of mismatch is +0.24%. STEM and TEM observations reveal that Nd₂O₃ thin film grows epitaxially on the SrTiO₃?100? substrate with?001?Nd₂O₃//?100?STO and [110]Nd₂O₃//[001]STO orientations. The interfacial Nd₂O₃ layer is found to make an exclusive contact to the SrO-terminated?100? STO layer and no any atomic diffusion exists on the interface by HAADF image. The interface between STO substrate and thin film is very flat and smooth.