The Effect OF Buffer Layerse On Growth Of Colossal Magnetoresistance Thin FIMS on Silicon

• Main Authors: Tsai, F.W, 蔡方文
• Other Authors: Chin, T.s.
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/62352148227011549090

碩士 === 國立清華大學 === 材料科學工程研究所 === 86 === 　　LaCaMnO (LCMO) thin films were grown on Si (100) by RF magnetron sputtering. Buffer layers including: (1) LaNiO3 (LNO) / LaAlO3 (LAO), (2) LNO / SrTiO3 (STO), (3) SiO2 were applied to study their effect on structure, magnetic and magnetoresistance of the films. 　　In double buffer layer system (Si / LNO / STO / LCMO), the LCMO shows polycrystal morphology because the STO buffered layer is polycrystalline. It presented a MR value of 3.5% at 60K when the inplane applied field is 1 tesla. 　　In other double layer system (Si / LNO / LAO / LCMO), The LCMO films grown on LAO seem to have more or less [001] preferred orientation. The as - deposited film exhibits an MR value of 8.1% (19K, 1T), which is further improved to 176% (14.5K, 1T) by a 900℃ × 2hr annealing. 　　In the last system, The high [001] preferred orientation of LCMO films have been successfully grown on SiO2 buffered Si (100) substrate for the first time. When the substrate temperature is at 700℃ with 10m Torr Po2, the film exhibits MR value as high as 700% near 15K (1T). The MR value can be improved by suitable controll of substrate temperature, Po2 and subsequent annealing. 　　In the above three systems, the resistivity drop occurs during cooling process. And the maximum MR value exhibits near semiconductor - metal transition temperature. Besides, the mutual diffusion and interfacial reactions, as manifest by SIMS, occur after a high temperature annealing for a long time. It deteriorates film structure and MR value apparently. 　　The film composition deviated from that of the target due to different sputtering yields. Ca is the main loss during sputtering. Due to this composition deviation, higher MR values were not attainable.