Date of Graduation
Eberly College of Arts and Sciences
Physics and Astronomy
Atomic force microscopy (AFM) was employed to investigate the surface roughness of 5.0 nm thick Co films as a function of the annealing temperature. Films were epitaxially grown on (110) sapphire via molecular beam epitaxy (MBE) and magnetron sputtering. Images were acquired in-situ at temperatures ranging between room temperature and 600°C. Surface roughening starts at 425°C and increases depending on the final annealing temperature and time. The films did not show a reversal of the roughening process upon sample cooling. Also a sub-monolayer film of Co was grown on Al2O 3 (0001) via MBE at room temperature. The film annealed at 400°C revealed the formation of dots with an average diameter of 17.6 nm and a height of 0.3 nm. Dots showed a superparamagnetic behavior with a blocking temperature of 130 K and an enhancement of the atomic magnetic moment over the bulk of approximately 9%.
Espinosa, Jorge, "Roughening of cobalt thin films on sapphire (110) upon annealing and superparamagnetic behavior of cobalt nanodots on sapphire (001)" (2005). Graduate Theses, Dissertations, and Problem Reports. 2178.