Pure phase BiFeO3 thin films sputtered over Si: A new route towards high magnetization

Abstract

We have investigated the structural and magnetic properties of BiFeO 3 (BFO) thin films grown over (100)-oriented Si substrates by rf magnetron sputtering in a new route under O 2 free low pressure Ar atmosphere. Single-phase BFO films were deposited in a heated substrate and post-annealed in situ. The new routed allows high deposition rate and produce polycrystalline BFO pure phase, confirmed by high resolution X-ray diffraction. Scanning electron and atomic force microscopy reveal very low surface roughness and mean particle size of 33 nm. The BFO phase and composition were confirmed by transmission electron microscopy and line scanning energy-dispersive X-ray spectroscopy in transmission electron microscopy mode. The surface chemistry of the thin film, analyzed by X-ray photoelectron spectroscopy, reveals the presence of Fe 3+ and Fe 2+ in a 2:1 ratio, a strong indication that the film contains oxygen vacancies. An hysteretic ferromagnetic behavior with room temperature high saturation magnetization ∼ 165 × 10 3 A/m was measured along the film perpendicular and parallel directions. Such high magnetization, deriving from this new route, is explained in the scope of oxygen vacancies, the break of the antiferromagnetic cycloidal order and the increase of spin canting by change in the surface/volume ratio. Understanding the magnetic behavior of a multiferroic thin films is a key for the development of heterogeneous layered structures and multilayered devices and the production of multiferroic materials over Si substrates opens new possibilities in the development of materials that can be directly integrated into the existent semiconductor and spintronic technologies.

XPS Study in BiFeO3 Surface Modified by Argon Etching

“…A low-pressure argon atmosphere (work pressure of 3 mTorr) was used to minimize chemical changes and reduce the presence of BFO spurious phases. The substrate deposition temperature was kept at 873 K, with further in-situ annealing at 973 K for 60 min after the film deposition [12]. In grazing incidence mode, the thin-film crystalline structure was studied by high-resolution X-ray diffraction (HR-XRD) performed in the Brazilian Synchrotron Light Laboratory (LNLS), with 1.3776 Å wavelength.…”

“…One way to reduce the presence of these phases during the BFO film preparation consists of using a mixed atmosphere of O 2 with an inert gas such as argon or nitrogen [11]. One can obtain pure phase BFO thin films over Si (100) by sputtering in an argon atmosphere at low pressure [12]. One way to study the thin film's surface properties is through X-ray Photoelectron Spectroscopy (XPS).…”

Recent advances in bismuth ferrite nanomaterials: Synthesis, characterization and application

“…In general, the reports in the literature focus on preparing thin film materials requiring an deposited surfaces such as LaAlO3, glass and amorphous silica substrates under encompassing various precursors routs [37][38][39][40] . For examples, the chemical vapor deposition 41,42 , pulsed laser deposition 43,44 , sputtering 45,46 , sol-gel process 47,48 and the polymeric 49,50 methods were employ to grow BiFeO3thin films. As displayed in Fig.…”

Interplay of piezoresponse and magnetic behavior in Bi0.9A0.1FeO2.95 (A = Ba, Ca) and Bi0.9Ba0.05Ca0.05FeO2.95 co-doped ceramics

“…It is desirable to achieve suppression of the spin-cycloid in BiFeO 3 at room temperature to pave way for enhanced magnetic properties. This can be realized through chemical substitution, [10][11][12][13][14][15][16][17] inducing strain in thin lms, [18][19][20][21] high magnetic elds, [22][23][24][25][26][27] hydrostatic pressure [28][29][30] and nite size effects. [31][32][33][34][35][36] Of these, aliovalent doping controls the chemistry of the material and oen could result in increased chemical pressure that would work similar to applying hydrostatic pressure externally.…”