In this study, thin films of Fe 83Ga 17 (a giant magnetostrictive alloy) were grown on single-crystalline n-GaAs (001) and polycrystalline brass substrates via electrochemical synthesis from ferrous and gallium sulfate electrolytes. Extensive structural characterization using microdiffraction, high-resolution ω - 2θ, and rocking-curve analysis revealed that the films grown on GaAs(001) are highly textured with 001 orientation along the substrate normal, and the texture improved further upon annealing at 300°C for 2 h in N 2 environment. On the contrary, films grown on brass substrates exhibited 011 preferred orientation. Rocking-curve analysis done on Fe 83Ga 17/GaAs structures further confirmed that the 001 texture in the Fe 83Ga 17 thin film is a result of epitaxial nucleation and growth. The non-linear current-voltage plot obtained for the Fe-Ga/GaAs Schottky contacts was characteristic of tunneling injection, and showed improved behavior with annealing. Thus, this study demonstrates the feasibility of fabricating spintronic devices that incorporate highly magnetostrictive Fe (1-x))Ga x thin films grown epitaxially via electrochemistry.
Bibliographical noteFunding Information:
The authors would like to thank the U.S. Office of Naval Research and Dr. Jan Lindberg (ONR N00014-06-1-0530) for their support. We are grateful to the National Science Foundation (NSF) for support via their MRSEC and NNIN centers, and the staff of the UMN Characterization Facility and Nanofabrication Center. K.S.M.R. would like to thank Dr. Manish Sharma and Dr. Mike Manno for useful discussions. FIG. 1. (Color online) (a) XRD of a Fe 83 Ga 17 thin film electrodeposited on brass substrate. Symbol (▪) represents brass substrate peaks. (b) SEM image showing a single crystal of Fe 83 Ga 17 bcc phase nucleated during initial stages of the growth. (c) A large-scale SEM image showing deterioration of the single-crystal growth resulting in polycrystalline growth near the top. (d) Schematic representing orientation of the nucleated crystals relative to the brass substrate. FIG. 2. (Color online) High-resolution XRD patterns of Fe−Ga thin films electrodeposited on n -GaAs (001) substrate. Symbol (♦) represents Fe 83 Ga 17 film peaks. Electrodeposition time is in brackets. XRD pattern D was obtained after sample B was annealed at 300 °C for 2 h in N 2 . FIG. 3. (Color online) (a) Diffraction patterns for Fe 83 Ga 17 (002) and Fe 83 Ga 17 (011) obtained on a 2D area detector in a Bragg-Brentano diffraction mode. The beamstop in the right image was used to block the GaAs(004) substrate spot. (b) Separate rocking curves of Fe−Ga(011), Fe−Ga(002), and GaAs(004) are shown overlaid. Schematic on the top represents the new orientation of the Fe−Ga thin film relative to the GaAs substrate. FIG. 4. (Color online) Current−voltage characteristics of Fe 83 Ga 17 /GaAs Schottky contacts as-grown and after annealing at 300 °C. All measurements were done at RT.