A comparative study of the influence of the deposition technique (electrodeposition versus sputtering) on the properties of nanostructured Fe70Pd30 films

Abstract

Sputtering and electrodeposition are among the most widespread techniques for metallic thin film deposition. Since these techniques operate under different principles, the resulting films typically show different microstructures even when the chemical composition is kept fixed. In this work, films of Fe₇₀Pd₃₀ were produced in a thickness range between 30 and 600 nm, using both electrodeposition and sputtering. The electrodeposited films were deposited under potentiostatic regime from an ammonia sulfosalicylic acid-based aqueous solution. Meanwhile, the sputtered films were deposited from a composite target in radio frequency regime. Both approaches were proven to yield high quality and homogenous films. However, their crystallographic structure was different. Although all films were polycrystalline and Fe and Pd formed a solid solution with a body-centered cubic structure, a palladium hydride phase was additionally detected in the electrodeposited films. The occurrence of this phase induced internal stress in the films, thereby influencing their magnetic properties. In particular, the thickest electrodeposited Fe₇₀Pd₃₀ films showed out-of-plane magnetic anisotropy, whereas the magnetization easy axis lied in the film plane for all the sputtered films. The domain pattern of the electrodeposited films was investigated by magnetic force microscopy. Finally, nanoindentation studies highlighted the high quality of both the sputtered and electrodeposited films, the former exhibiting higher reduced Young's modulus and Berkovich hardness values.

Keywords: 105 Low-Dimension (1D/2D) materials; 106 Metallic materials; 203 Magnetics / Spintronics / Superconductors; 301 Chemical syntheses / processing; 303 Mechanical / Physical processing; 306 Thin film / Coatings; 503 TEM; 504 X-ray / Neutron diffraction and scattering; FePd alloy; SEM; STEM; electrodeposition; magnetic properties; mechanical properties; perpendicular magnetic anisotropy; sputtering; stripe domains; thin films.

Graphical abstract

Figure 1.

(a) SEM micrograph and (b) and (c) AFM images of the surface of the sputtered film with 46 nm thickness. (d) SEM micrograph and (e) and (f) AFM images of the surface of the sputtered film with 500 nm thickness

Figure 2.

Evolution of the roughness for the sputtered and electrodeposited films as a function of the film’s thickness

Figure 3.

GIXRD plots labeled by film thickness from: (a) sputtered and (b) electrodeposited films. Intensity values are reported in linear scale. Unlabeled peaks in (a) belong to the substrate. Inset of panel (b) shows the geometry of the GIXRD set-up used for the acquisition of the GIXRD plots

Figure 4.

(a) SEM micrograph and (b) and (c) AFM images of the surface of the electrodeposited film with 30 nm thickness. (d) SEM micrograph and (e) and (f) AFM images of the surface of the electrodeposited film with 600 nm thickness

Figure 5.

TEM images of the cross-section of the (a) 30 nm and (b) 600 nm thick electrodeposited films

Figure 6.

Hysteresis loops, measured at room temperature, for the in-plane orientation of the field corresponding to the (a) sputtered and (b) electrodeposited films with varying thickness. The insets show the evolution of the coercive field as a function of the film thickness for the sputtered and electrodeposited films

Figure 7.

Room temperature MFM images, acquired at magnetic remanence, for the electrodeposited films with a thickness of (a) 600 nm, (b) 340 nm, (c) 305 nm and (d) 30 nm

Figure 8.

Load-displacement nanoindentation curves of the: (a) 305 nm thick electrodeposited (circles) and 300 nm thick sputtered (squares) films and (b) 600 nm thick electrodeposited (circles) and 500 nm thick sputtered (squares) films