Epitaxial Growth of CeO_2(110) Layrs on Si(100) Substrates

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Epitaxial cerium dioxide (CeO_2) layrs on silicon substrates are of great interest both for growing high-quality epitaxial insulating materials on Si with close lattice matching and for applications to microelectronics such as miniaturized stable capacitors, silicon on insulator structures and buffer layrs between high-temperature superconductors and Si substrates. In the course of the investigation on the epitaxial growth of CeO_2 on Si, it has been clarified that although CeO_2(111) layrs grow on Si(111) at low temperatures with high crytallinity, CeO_2 layrs grown on Si(100) have a (110) orientation and require a higher substrate temperature of - 820ﾟC.Moreover, the CeO_2(110) layr tends to have a double domain structure consisting of a mixture of CeO_2[100]||Si[110] and CeO_2[110]||Si[110]. It has been found that single-crytalline CeO_2(110) layrs are realized using substrates with an optimum miscut of 2.5ﾟ towards the <110> direction. For silicon-based microelectronic device fabri … More cation, low-temperature processes are strongly desired. In order to lower the epitaxial growth temperature of CeO_2(110) layrs on Si(100) substrates, it is thought that some extrinsic assistance by energetic particles such as ions, electrons and photons, is needed to give sufficient energy for the rearrangement of adsorbed atoms and/or molecules at the growing surface.In this research project, the effect of electron incidence is studied in the epitaxial growth of CeO_2(110) layrs on Si(100) substrates by electron-beam evaporation. Two growth methods are employed : evaporation under substrate bias application (bias evaporation) and electron-beam assisted evaporation. In bias evaporation, a small portion of charged particles among evaporating particles are attracted to the substrate surface by the bias potential and facilitate the CeO_2 epitaxial growth. It is found that electrons from an evaporation sosurce lead to a successful epitaxial temperature lowering in evaporation at positive bias. electron-beam assisted evaporation has much greater effect in both epitaxial temperature lowering and the crystalline quality improvement. This method, a novel method of evaporation with simultaneous electron-beam irradiation has advantages over bias evaporation because of the wider variable range and greater control of the energy and current density of electron irradiation. The epitaxial temperature is lowered to 710ﾟC,i.e., more than 100ﾟC low compared with that of the conventional method. It is clarified that the electron beam assisted evaporation is very promising as an adavanced method for thin film growth. Less