真空热处理对CoFe薄膜结构及电磁特性的影响

Influence of Annealing Temperature on Microstructures and Electromagnetic Properties of CoFe Films

在本底真空度优于5×10-4Pa的室温条件下,利用电子束蒸发方法沉积CoFe薄膜,研究了不同退火温度对CoFe薄膜结构和电磁特性的影响。样品采用热氧化Si为基片,在3×10-5Pa真空度下分别进行了150、280、330、450和500℃的60min退火处理。电阻率和磁电阻测量表明,450℃退火处理能够明显降低CoFe薄膜电阻率和提高磁电阻变化率,因为这时的X射线衍射谱显示CoFe薄膜的结构已明显改善。还发现沉积在热氧化Si基片上的CoFe薄膜(111)晶面面间距明显小于靶材相应晶面面间距,而退火处理会使薄膜(111)晶面面间距接近恢复到靶材。透射电镜对沉积态样品分析表明,样品呈多晶结构但结晶不太理想。振动样品磁强计(VSM)的磁特性测量发现,500℃真空退火处理,薄膜的矫顽力和饱和磁化强度都提高近一倍,分别由室温沉积态的2337 A/m和327 emu/cm3上升到退火后的4746 A/m和649 emu/cm3。

Influence of annealing temperature on the microstructures, electrical and magnetic properties of the CoFe films, grown by ebeam evaporation on thermally oxidized silicon suhstrates at room temperature,under a pressure of 5 × 10^-4 Pa, was studied with X-ray diffraction （XRD） and transmission electron microscopy （TEM）. The results show that annealing at 450 ℃ considerably reduces its resistivity and increases its anisotropic magneto-resistance ratio of the polycrystalline CoFe films because the annealing removes some defects and improves its microstructures. Moreover, the annealing relaxes the CoFe（111 ） layer-spacing of the films to that of its bulk crystal. In addition, after annealing at 500 ℃, its coercive force and its saturation magnetization intensity were found to increase from 2337 A/m and 327 emu/cm^3 to 4746 A/m and 649 emu/cm^3, respectively.