Study On The Relationship Between Surface Morphology And Growth Mechanisms Of Co And Al₂O₃ Nano-Films

Co/Al₂O₃/Co multilayers are a species of ultra-high density storage materials with small volume and tunnel magnetoresistance effect. It will maybe develop a kind of memory, which will induce a revolution of memory chip of computer.We prepared Co and Al₂O₃ samples which the thicknesses are 1, 2, 3, 5, 10, 50 and 100nm respectively using ion beam sputtering deposition. The evolution of surface morphology with different deposition times has been observed by AFM on Co and Al₂O₃ nano-films deposited on silicon. It is found that Co and Al₂O₃ nano-films have different growth stages according to the difference of surface roughness at different deposition times and we verify the correctness about kinetics process in nano-films growth by density of peaks.X-ray diffractometer and grazing incident diffraction results show that Co nano-films on Si(100) substrate have very strong preferred orientation. There is an X-ray diffuse scattering peak between 40°-55°. And at the same time there are diffraction peaks of Co-Si compound. There are no Al₂O₃ diffraction peaks, the Al₂O₃ nano-films using ion beam sputtering deposition are amorphous state.We have investigated resistivity and anisotropy magnetoresistance ratio of Co nano-films using four-probe instrument. The results are that the resistivity gradually decreased and AMR gradually increased with the film's thickness increasing. When the film's thickness is more than 50nm, the influence of the film's thickness for the two parameters is weak.We have researched the surface component of Co and Al₂O₃ nano-films. The results show that with the film's thickness gradually increased, the Si photoelectron peaks are gradually reduced and disappeared at the end. So, we can say that the compactness of Co nano-films is very good, which there are very close relationship with film's growth mechanism. The semi-quantitative calculation analysis of Al₂O₃ nano-films show that the composition admeasurement of Al₂O₃ nano-films by ion beam sputtering deposition concluded that the Al︰O is 1.96︰3, which accord with the standard composition admeasurement.At last, we researched the effect of annealing for Co and Al₂O₃ nano-films. Annealing made the crystallized state more perfectly and the state of nano-films changes from amorphpus to crystalline. The particles on surface of nano-films present growing and aggregating in varying degrees. The resistance and AMR of Co nano-films were influenced for the Co film's structure changed. The resistance decreased obviously and AMR increased greatly. The thiner the film's thickness were, the better the effect of the annealing was.