Transmission electron microscopy studies of lanthanum manganese oxide and lanthanum strontium manganese oxide thin films grown on various substrates.

摘要

LaMnO3 (LMO) and La1-xSrxMnO 3 (LSMO) thin films with colossal magnetoresistance have attracted considerable interest for potential applications in many technological devices, such as magnetic sensors and read-head of computer memory. In this work, polycrystalline and epitaxial LMO and LSMO thin films were deposited on various substrates including (001) Si, (001) MgO, and (001) LaAlO3 (LAO) using RF magnetron sputtering. The microstructures of the thin films were initially studied using X-ray diffraction. Detailed microstructure information such as crystallite of the films, grain size, epitaxial quality, crystallographic structure and film/substrate interface were studied using high-resolution transmission electron microscope (HRTEM). More specifically, Effects of sputtering temperature, power and various substrates on the microstructure of the LMO and LSMO films were studied. HRTEM results showed that LMO and LSMO thin films on Si, MgO and LAO substrate deposited at 700 °C have (1) an amorphous structure using a power of 50 W and small crystalline structures using a power of 80 W. LMO and LSMO thin films on Si substrates deposited at 750 °C using a power of 30 W show nano columnar polycrystalline structures. By optimizing the deposition conditions, epitaxial LMO and LSMO thin films with a single crystal structure have been usefully fabricated on both LAO and MgO substrates at 750 °C using a sputtering power of 30 W.