Structure of agron sputtered Gd-Co and Gd-Co-Mo amorphous thin films

Abstract

We have investigated the short range order structure, microstructure and compositional fluctuations in argon bias-sputtered very thin films of Gd-Co and Gd-Co-Mo alloys. Bright field microscopy results show compositional fluctuations in the form of rods and thin sheets of Gd-rich material nearly perpendicular to the surface. The size of these rods is approximately from 30 to 100 Å and is consistent with the observed low angle anisotropic halo which occurs in the vicinity of ∥s∥=0.19 (Å)-1. We also find the surface of these films to have thickness modulations and irregularities which are found to be dependent on the bias at which the films were deposited. Energy filtered low angle electron scattering data show one or two well defined haloes. From the annealing behavior of the low angle scattering we determined that small pores in the structure anneal out and coalesce into larger pores of approximately 30 Å in diameter at about 120°C±50°C. At this temperature the intensity of the first split halo at s1=2.0 (Å)-1 and s2=2.6-2.95 (Å)-1 sharpens up, which results from atomic redistribution of both Gd and Co in real space. This relaxation of the structure occurs prior to crystallization. We also observe the low angle scattering halo at ∥s∥=0.19 (Å)-1 to increase in intensity as the temperature is lowered below 300°K. This increase we attribute to an increase in the net magnetization of the film.