Conductive Oxide Lanio <sub> 3 </ Sub> Thin Film Growth And Ferroelectric Integration

In recent years, ferroelectric thin films have been receiving more and more attention for their applications in integrated circuit and other functional devices. In these applications, it is essential to fabricate high quality ferroelectric thin films on proper electrode materials, such as conductive oxides. LaNiO3 (LNO), as a desirable candidate for electrode materials, has a pseudo-cubic perovskite crystal structure with a lattice parameter of 3.84? and a resistivity of 225μ?.cm at 300K with good chemical and thermal stabilization. It has the similar crystal structure and good crystal matche with ferroelectric thin films,such as BaTiO3 . In this paper, the growth of LNO thin films on different substrates and the integration of ferroelectric thin films on the LNO electrodes have been systematically studied.Firstly, LaNiO3 (LNO) films with different thickness were deposited on STO (100) substrates in the different oxygen pressure. Effects of oxygen pressure on microstructure of LNO conductive thin film has been studied by in situ reflection high energy diffraction (RHEED) and ex situ X-ray photoelectron spectroscopy (XPS). In the relatively low oxygen pressure, LNO film displays spotty RHEED pattern. When the thickness increases up to a critical value, about 30 nm, the spotty RHEED pattern gradually changes to streaky pattern, and the RHEED oscillation curve appears. The RHEED pattern of the ultra thin LNO film deposited in the relatively high oxygen pressure is streaky pattern. With pumping the oxygen pressure to the relatively low value, the streaky RHEED pattern gradually changes to spotty one. When increasing the oxygen pressure, the RHEED pattern changes to streaky one again. This RHEED pattern transformation induced by the oxygen pressure is reversible. Ex situ XPS results indicate that the element Ni of LNO film deposited in the relatively low oxygen pressure with thickness below the critical value exists in the form as Ni2+, while as Ni3+ in the relatively high oxygen pressure. When the thickness increases to upon the critical value, the chemical valence of element Ni in the top layers of LNO film deposited in the relatively low oxygen pressure is +3. A mechanism of effects of oxygen pressure on microstructure of LaNiO3 conductive thin film is given.Then, a series of metallic LaNiO3 (LNO) thin films were deposited on (100)-oriented MgO, SrTiO3 (STO) and LaAlO3 (LAO) crystal substrates by pulsed laser deposition (PLD) under the oxygen pressure of 20Pa at different substrate temperatures from 450oC to 750oC. X-ray diffraction (XRD), ex situ reflection high...