Structural Defects and Ferromagnetic Signature of V-Doped Sb(2)Te(3) Thin Films Grown on SrTiO(3)(001) Produced by RF-Magnetron Sputtering

[Image: see text] Thin films of V-doped Sb(2)Te(3) compounds were fabricated by co-deposition of Sb(2)Te(3) and V using rf-magnetron sputtering onto SrTiO(3)(001) substrates kept at 570 K. The microstructures of the films were characterized using transmission electron microscopy (TEM) and electron diffraction. The crystal structure of the sputtered film (Sb(38)V(2)Te(60)) is the Bi(2)Te(3)-type structure with lattice parameters of a = 0.44 ± 0.03 nm and c = 3.02 ± 0.02 nm. A combination of cross-sectional and plan-view TEM observations revealed the preferential orientation of the c axis in the film’s normal direction. A thin amorphous layer exists between the Sb(2)Te(3) thin film and the SrTiO(3) substrate. The interfacial amorphous layer relaxes the strain between the thin film and the substrate, and hence, it should promote the growth of a low-index atomic plane with a low surface free energy (i.e., (0001) of the Sb(2)Te(3)). The onset of ferromagnetic order was detected at temperatures below 70 K. A remarkable increase in magnetization was detected in the film’s normal direction, which corresponds to the magnetic easy axis (i.e., c axis of the Sb(2)Te(3)). V(3+) ions substituting Sb sites should contribute to ferromagnetism at low temperatures.