Surface smoothing and crystalline reorientation in thin cobalt films

Article

关键词: CO FILMS;    PARTICLES;    PHOTOEMISSION;    TEMPERATURE;    SAPPHIRE;    CU(001);    GROWTH;   

DOI  :  10.1103/PhysRevB.58.R1778

来源: SCIE

【 摘 要 】

Epitaxial cobalt films in the thickness range of 3.9 to 8.6 nm were deposited on Al2O3[11 (2) over bar 0] substrates by de magnetron sputtering at a substrate temperature of 315 degrees C. In situ annealing was performed in a vacuum after which the samples were rapidly quenched to room temperature in order to preserve the high temperature structure. Ex situ atomic-force microscopy revealed that surface roughening takes place during annealing and reaches a maximum when the annealing temperature TA is equal to a critical temperature T(C)similar to 500 degrees C. We discovered that if T-A>T-C the surface becomes smooth again, although large rectangular pits that go down to the substrate also appear. X-ray-diffraction data show that unannealed samples are oriented along the hcp[0001] direction. Upon annealing samples transform to a preferentially fcc[111] orientation for T-AT-C. We show that surface or interface oxidation cannot be the sole cause of this effect. We speculate that an increasing interface strain st higher temperatures or a surface reconstruction of the substrate are possible mechanisms.

【 授权许可】

Free