氧缺失对Nd0.7Sr0.3MnO3外延膜结构和输运性的影响

摘要

不同厚度的Nd0.7Sr0.3MnO3(NSMO)外延膜是由脉冲激光沉积生长在(LaAlO3)0.3(Sr2AlTaO6)0.7(LSAT)(001)衬底上的.X射线衍射(XRD)和电阻率测量结果显示,沉积氧压为21.333Pa时薄膜c轴参数随着膜厚的减小而增加,同时金属-绝缘体的转变温度TP下降,电阻率增大；另一组生长在27.999Pa氧压下,厚度为120nm的薄膜单胞体积随着退火温度的升高而增大,同时电阻率升高,TP下降.上述结果归因于低的原位沉积氧压和真空退火引起的氧缺失导致n(Mn3+)(M甜+)的增大以及MnO6八面体的畸变.结果表明,对超薄的应变薄膜,要获得较高的TP值,较高的沉积氧压是必需的,同时应仔细考虑真空退火对薄膜性能的影响.%Nd0.7Sr0.3 MnO3 films of various thicknesses were grown on (LaAlO3 )0.3 (Sr2AlTaO6)0.7 (LSAT) (001) substrates by the pulsed-Saser-deposition method, and their structure, metal-insulator transition temperature Tp were examined by X-ray diffraction and resistivity measurements. To clarify the effects of in situ deposition oxygen pressure and vacuum annealing temperature on the structure and the thickness dependence of Tp , the films were grown at an oxygen pressure of 21. 333Pa and 27. 999Pa, respectively. The results show that the c axis parameter of the NSMO film (at 21. 333Pa oxygen pressure) grown at low oxygen pressure and is elongated with the reduction of the film thickness, the increase of the resistivity and the reduction of the metal-insulator transition temperature (TP) are also observed. The c axis parameter of the NSMO film (at 27. 999Pa oxygen pressure) is elongated with the increase annealing temperature, the increase of the resistivity and the reduction of the metal-insulator transition temperature (Tp) are also observed as the annealing temperature. These are attributed to the increase of n(Mn3+ )(Mn4+ ) and the distortion of MnO6 octahedra induced from the oxygen deficiency. The results indicate that to get higher Tp especially for the ultra-thin films, higher deposition oxygen pressure is indispensable, and the vacuum annealing effects on the thin and thick films are also discussed in terms of their different microstructure.