Combinatorial pulsed laser deposition of Fe, Cr, Mn, and Ni-substituted SrTiO3 films on Si substrates

Bi Alloying into Rare Earth Double Perovskites Enhances Synthesizability and Visible Light Absorption

A high throughput combinatorial synthesis utilizing inkjet printing of precursor inks was used to rapidly evaluate Bi-alloying into double perovskite oxides for enhanced visible light absorption. The fast visual screening of photo image scans of the library plates identifies 4-metal oxide compositions displaying an increase in light absorption, which subsequent UV-vis spectroscopy indicates is due to bandgap reduction. Structural characterization by X-ray diffraction (XRD) and Raman spectroscopy demonstrates that the visually darker composition range contains Bi-alloyed Sm₂MnNiO₆ (double perovskite structure), of the form (Bi,Sm)₂MnNiO₆. Bi alloying not only increases the visible absorption but also facilitates crystallization of this structure at the relatively low annealing temperature of 615 °C. Investigation of additional seven combinations of a rare earth (RE) and a transition metal (TM) with Bi and Mn indicates that Bi-alloying on the RE site occurs with similar effect in the family of rare earth oxide double perovskites.

Pulsed laser deposition with rapid beam deflection by a galvanometer mirror scanner

A pulsed laser deposition system with rapid beam deflection (RBD-PLD) by a galvanometer mirror scanner has been developed for alternating ablation of multiple targets with a single laser instrument. In this system, the alternating deposition of different target materials is carried out by scanning the laser beam between the positionally fixed targets with a galvanometer mirror instead of mechanically switching the target positions on a fixed optical path of the laser beam as is done in conventional pulsed laser deposition (PLD) systems. Thus, the "wait" time required for switching target materials to be deposited, which typically takes several seconds in a conventional system, can be made as short as a few milliseconds. We demonstrate some of the advantages of this PLD system in several technologically important aspects of thin film synthesis: (1) fast fabrication of binary alloy films, (2) preparation of natural composition spread libraries, (3) effect of the target switching time on the deposition of volatile compounds, (4) control of the degree of mixing of two different materials in a film, and (5) efficient growth of compositionally graded thin films.

ABO3 and A1-xCxB1-yDy(O1-zEz)3: review of experimental optimisation of thin film perovskites by high-throughput evaporative physical vapour deposition

The development of functional perovskites for future technologies can be achieved though the combinatorial synthetic method of evaporative physical vapour deposition (HT-ePVD) which provides a direct low temperature route to anion stoichiometric materials. When combined with the ability to control and vary precisely the composition of thin film libraries of materials, high-throughput methods of screening and characterisation provides a rapid experimental determination of the structure/function relationship. This review of the use of HT-ePVD shows that controlled cationic substitutions in A and/or B sites can easily be explored, as can the effect of anionic substitution. This is exemplified in using this approach for a wide range of perovskite systems, where the tuning of the functional properties through cation substitution has application in a broad range of technologies.

Thin-Film Processing Routes for Combinatorial Materials Investigations-A Review

High-throughput combinatorial investigations are transforming materials discovery, phase diagram development, and processing optimization. Thin-film deposition techniques are frequently used to fabricate sample libraries employed in these studies. Various adaptations of well-known thin-film chemical vapor deposition (CVD) and physical vapor deposition (PVD) techniques utilized for the synthesis of inorganic combinatorial thin-film materials libraries are reviewed, with novel processing approaches being highlighted. Methods for developing gradients in composition of other film properties are described. Issues and considerations specific to thin-film processing of combinatorial materials libraries are discussed, with some emphasis on catalytic applications.

Nanopillars with E-field accessible multi-state (N ≥ 4) magnetization having giant magnetization changes in self-assembled BiFeO3-CoFe2O4/Pb(Mg1/3Nb2/3)-38at%PbTiO3 heterostructures

We have deposited self-assembled BiFeO₃-CoFe₂O₄ (BFO-CFO) thin films on (100)-oriented SrRuO₃-buffered Pb(Mg_1/3Nb_2/3)_0.62Ti_0.38O₃ (PMN-38PT) single crystal substrates. These heterostructures were used for the study of real-time changes in the magnetization with applied DC electric field (E_DC). With increasing E_DC, a giant magnetization change was observed along the out-of-plane (easy) axis. The induced magnetization changes of the CFO nanopillars in the BFO/CFO layer were about ΔM/M_rDC = 93% at E_DC = −3 kv/cm. A giant converse magnetoelectric (CME) coefficient of 1.3 × 10⁻⁷ s/m was estimated from the data. By changing E_DC, we found multiple(N ≥ 4) unique possible values of a stable magnetization with memory on the removal of the field.

Magnetic and Photoluminescent Coupling in SrTi0.87Fe0.13O3-δ/ZnO Vertical Nanocomposite Films

Self-assembled growth of SrTi_0.87Fe_0.13O_3-δ (STF)/ZnO vertical nanocomposite films by combinatorial pulsed laser deposition is described. The nanocomposite films form vertically aligned columnar epitaxial nanostructures on SrTiO₃ substrates, in which the STF shows room-temperature magnetism. The magnetic properties are discussed in terms of strain states, oxygen vacancies, and microstructures. The nanocomposites exhibit magneto-photoluminescent coupling behavior that the near-band-edge emission of ZnO is shifted as a function of magnetic field.

Magnetic Phase Formation in Self-Assembled Epitaxial BiFeO3-MgO and BiFeO3-MgAl2O4 Nanocomposite Films Grown by Combinatorial Pulsed Laser Deposition

Self-assembled epitaxial BiFeO3-MgO and BiFeO3-MgAl2O4 nanocomposite thin films were grown on SrTiO3 substrates by pulsed laser deposition. A two-phase columnar structure was observed for BiFeO3-MgO codeposition within a small window of growth parameters, in which the pillars consisted of a magnetic spinel phase (Mg,Fe)3O4 within a BiFeO3 matrix, similar to the growth of BiFeO3-MgFe2O4 nanocomposites reported elsewhere. Further, growth of a nanocomposite with BiFeO3-(CoFe2O4/MgO/MgFe2O4), in which the minority phase was grown from three different targets, gave spinel pillars with a uniform (Mg,Fe,Co)3O4 composition due to interdiffusion during growth, with a bifurcated shape from the merger of neighboring pillars. BiFeO3-MgAl2O4 did not form a well-defined vertical nanocomposite in spite of having lower lattice mismatch, but instead formed a two-phase film with in which the spinel phase contained Fe. These results illustrate the redistribution of Fe between the oxide phases during oxide codeposition to form a ferrimagnetic phase from antiferromagnetic or nonmagnetic targets.

Oxygen partial pressure dependence of magnetic, optical and magneto-optical properties of epitaxial cobalt-substituted SrTiO₃ films

Cobalt-substituted SrTiO3 films (SrTi0.70Co0.30O(3-δ)) were grown on SrTiO3 substrates using pulsed laser deposition under oxygen pressures ranging from 1 μTorr to 20 mTorr. The effect of oxygen pressure on structural, magnetic, optical, and magneto-optical properties of the films was investigated. The film grown at 3 μTorr has the highest Faraday rotation (FR) and magnetic saturation moment (M(s)). Increasing oxygen pressure during growth reduced M(s), FR and optical absorption in the near-infrared. This trend is attributed to decreasing Co2+ ion concentration and oxygen vacancy concentration with higher oxygen partial pressure during growth.

Combinatorial pulsed laser deposition of magnetic and magneto-optical Sr(GaxTiyFe0.34-0.40)O3-δ perovskite films

Ferromagnetic Sr(GaxTiyFe0.34-0.40)O3-δ (0.1 ≤ x, y ≤ 0.5) films with single-crystal perovskite structure were epitaxially grown on (001) (LaAlO3)0.3(Sr2AlTaO6)0.7 substrates by combinatorial pulsed laser deposition (CPLD) and compared with previous results from films grown from single targets. In CPLD films the Fe was present as both Fe(2+) and Fe(3+). The distribution of Sr, Ga, Ti, and O was homogeneous, but Fe-rich nanowires with diameter of 3 nm were present perpendicular to the film plane. The unit cell was tetragonally distorted with the ratio of out-of-plane to in-plane lattice parameter decreasing from 1.06 to 1.02 as the Ga content increased. The magnetic easy axis of the films changed from out-of-plane when Ti content y > 0.3 to isotropic as the Ga content increased, consistent with a reduction in magnetoelastic anisotropy. The Ga lowered the Faraday rotation and the magnetization but increased the optical transmittance.

Epitaxial growth of high-quality AlN films on metallic nickel substrates by pulsed laser deposition

Single-crystalline AlN films with smooth surface and abrupt interface have been grown on metallic nickel (Ni) substrates by pulsed laser deposition with an in-plane epitaxial relationship of AlN[112̄0]//Ni[11̄0].

Magnetostriction in epitaxial SrTi(1-x)Fe(x)O(3-δ) perovskite films with x = 0.13 and 0.35

The crystal structure, magnetic anisotropy and magnetoelasticity of epitaxial SrTi(0.87)Fe(0.13)O(3-δ) (STF13) and SrTi(0.65)Fe(0.35)O(3-δ) (STF35) films grown on (001), (011), and (111) oriented SrTiO(3) substrates were investigated. The films grew with compressive in-plane strain and underwent tetragonal, monoclinic, and rhombohedral distortions on the (001), (011), and (111) substrates, respectively. All samples showed room temperature magnetic hysteresis loops with strong out-of-plane anisotropy. The resulting magnetoelastic anisotropy was an order of magnitude greater than the magnetocrystalline and shape anisotropies. Magnetoelastic coefficients of B(1) =- 6.7 × 10(6) and B(2) =- 28 to -26 × 10(6) erg cm(-3) for STF13 and B(1) =- 2.0 × 10(6) and B(2) =- 5.4 to -3.9 × 10(6) erg cm(-3) for STF35 were determined from the magnetic anisotropy and lattice strain, corresponding to magnetostriction constants of λ(100) = 2.09 × 10(-6) and λ(111) = 7.68 × 10(-6) for STF13, and λ(100) = 0.62 × 10(-6) and λ(111) = 1.07 × 10(-6) for STF35.