Pulsed Laser Deposition Properties Research Articles

Post-annealing effects on structural and magnetic properties of pulsed laser deposition grown Co–Ni–Al ferromagnetic shape memory alloys thin films

Co–Ni–Al is considered as a suitable ferromagnetic shape-memory alloy and has significant control over structural transformation temperature, magnetic parameters, and ductility. In this paper, the fabrication of Co–Ni–Al alloy thin films on Si (1 0 0) substrate was achieved via pulsed laser deposition (PLD) technique. The developed films annealing was done at 573, 673, and 773 K temperatures and inveterate their crystalline structure, phase analysis, and magnetic nature of the annealed Co38Ni35Al27 films. X-ray diffraction analysis at 773 K annealing temperature reveals that, the Co38Ni35Al27 film shows high crystallinity, and all annealed films have a body-centered cubic phase structure. The crystallite size estimated from Scherrer rule is noticed to increase from 10 to 22 nm when the annealing temperature raised to 773 K. From the SEM images, we infer that there is an increase in grain size when the annealing temperature increases and the grains shape looks spherical. The magnetic study of the samples shows that the film possesses highest magnetic saturation and lowest coercivity at 773 K annealing temperature. Also, the film annealed at 773 K exhibits a wide range of transformation temperatures and has a curie temperature of 180 K.

Elastic strain control of electronic structure, and magnetic properties of [Pr1−xCaxMnO3/SrTiO3]15 superlattices

We report the growth, electronic structure, and in-plane magnetic properties of pulsed laser deposition grown 2D superlattice structures [Pr0.7Ca0.3MnO3/SrTiO3]15 and [Pr0.5Ca0.5MnO3/SrTiO3]15 on (001) oriented SrTiO3 and LaAlO3 single crystal substrates. The x-ray reflectivity measurements reveal well-defined interfaces between the manganite and titanate layers along with the existence of Kiessig fringes, providing the evidence for the smooth periodic superlattice structure. The reciprocal space mapping provides signature of tetragonal distortion in all the superlattices. The electronic structure determined from the x-ray photoelectron spectroscopy reveals divalent Sr and Ca, tetravalent Ti, and mixed valent Mn with a pronounce shift of binding energy peaks toward the higher energy side in the superlattices grown on (001) oriented LaAlO3 as compared to those grown on SrTiO3. These superlattices exhibit highly anisotropic ferromagnetic character. We used the law of approach to saturation to determine the anisotropy field (HK) and cubic anisotropy constant (K1) for all the investigated superlattices. This analysis yields the highest HK∼9 kOe and K1∼8×105 erg/cc for the [Pr0.7Ca0.3MnO3/SrTiO3]15 superlattice system. Furthermore, significant enhancement of the overall magnetic moment and a decrease in TC (<100 K) was observed in the case of LaAlO3 grown superlattice, which indicates a substantial role of residual elastic strain on the magnetic ordering. Our results indicate that the strain induced elongation of MnO6 octahedra leads to finite possibility of non-orthogonal overlapping of orbitals in the presence of large crystal field splitting of eg levels, which, in turn, causes suppression of the ferromagnetic double exchange interaction.

Drastic deviations from stoichiometry transfer during pulsed laser deposition

In common, one of the most characteristic properties of pulsed laser deposition is the stoichiometry transfer between target and substrate, which has been used heavily for many complex systems. In this paper we show that it is yet possible to obtain drastic deviations from stoichiometry transfer in a binary system by just varying the fluence during laser deposition. In the W–Cu system, the W concentration of films grown from a composite W60Cu40 target (60 wt% W) was indeed continuously changed over an unprecedented large range of 0–70 wt% W. Close to the deposition threshold, pure Cu films are formed due to the much higher vapor pressure of Cu. At higher laser fluences, more and more W-rich W–Cu alloy samples are obtained, since ion implantation and intermixing processes occur. These alloys can reach W contents even higher than that of the target because of enhanced resputtering and reflection of the lighter Cu atoms at the film surface. Stoichiometric films with 60 wt% of W are only obtained at laser fluences around 2.7 J/cm2, when the strong Cu evaporation from the target and reflection and resputtering effects of Cu at the film surface are in balance.

Structural characterization and optical properties of pulsed laser deposition of Se75Te25 and Se75Te17Ge8 amorphous thin films

Thin films of Se75Te25 and Se75Te17Ge8 were deposited onto glass substrates using a pulsed laser deposition technique. The target materials used for the films deposition were prepared by conventional solid state reaction in a vacuum sealed silica tube to avoid oxide formation. Chemical composition and structural characterization were investigated using energy-dispersive X-ray spectrometry (EDX) and X-ray diffraction (XRD). The optical constants were determined from the spectrophotometric measurements of the transmittance and reflectance spectra carried out on the prepared films. The refractive index behavior is adequately described by the single oscillator model proposed by Wemple and DiDomenico whereby the oscillator parameters values were determined. The optical absorption coefficient was analyzed to identify the type of the optical transition and for determination of the corresponding energy values.

The effect of target rotation rate on structural and morphological properties of thin garnet films fabricated by pulsed laser deposition

The effect of target rotation rate on the structural and morphological properties of pulsed laser deposition grown Bi:YIG garnets is investigated. The rotation rate dependence of the surface morphology and magnetic properties of the thin films were studied using atomic force microscopy combined with a magneto-optical measurement setup. The results show that decrease in the target rotation rate can also increase the roughness, the index of refraction, and the surface skewness and can decrease Faraday rotation by an order of magnitude.

PLD-fabricated anisotropic Nd–Fe–B thick films with Ga additive

In this report, an evaluation on magnetic properties of pulsed laser deposition (PLD)-made anisotropic films with Ga additive was carried out. Coercivity, remanence, and (BH)max values of a film prepared from a Nd2.6Fe14B including Ga target were approximately 850 kA/m, 0.95 T, and 150 kJ/m3, respectively. These magnetic properties were superior compared with those for the anisotropic PLD-made Nd–Fe–B films without additives. The peak intensities of x-ray diffraction patterns corresponding to c-planes such as (004), (006), and (008) of the film with Ga additive were stronger than those of the additive-free film.

Effect of NH3 and N2 annealing on the interfacial and electrical characteristics of La2O3 films grown on fully depleted SiGe-on-insulator substrates

The interfacial structure and the electrical properties of pulsed laser deposition derived La2O3 ultra-thin films on fully depleted SiGe-on-insulator (FD SGOI) substrates before and after post-annealing in NH3 and N2, respectively, have been investigated comparatively. The results from high-resolution transmission electron microscopy and x-ray photoelectron spectroscopic revealed that interface reactions take place after the NH3 and N2 annealing process, but, as compared with the N2 annealing process, the NH3 annealing process can effectively decrease the thickness of the interfacial layer and incorporate more nitrogen at the dielectric/SiGe interface, resulting in smaller equivalent oxide thickness. The La2O3 capacitors annealed in NH3 show good capacitance–voltage characteristics with negligible hysteresis, smaller interface trap density and lower gate-leakage current density in comparison with those of capacitors annealed in N2. It is demonstrated that the NH3 annealing process can be a promising technology in improving the quality of high-k dielectric on FD SGOI substrates.

Nd–Fe–B thick films prepared at the high deposition rate of 90 µm/h

AbstractAfter a postannealing process, the magnetic properties of pulsed laser deposition (PLD)‐made Nd–Fe–B film magnets prepared at the deposition rate of 20–90 µm/h showed constant values, and the average values of Hc, Br and (BH)max were 1050 kA/m, 0.6 T, and 60 kJ/m3, respectively. The obtained results were comparable to those previously reported. In conclusion, it was found that a maximum deposition rate of 90 µm/h could be achieved without deterioration of magnetic and mechanical properties. © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Nd:GdVO 4 thin films grown on La 3Ga 5SiO 14 (LGS) and sapphire substrates by pulsed laser deposition properties

Nd-doped gadolinium vanadate (Nd:GdVO 4) films have been grown on La 3Ga 5SiO 14 (LGS) and sapphire substrates by pulsed laser deposition for the purpose of fabricating diode-pumped waveguide lasers. Films were grown over a range of temperatures from 600 to 700 °C in the presence of an oxygen pressure between 2 and 20 Pa. Films were characterized by X-ray diffraction, atomic force microscopy, and prism coupling method. Nd:GdVO 4 films on different substrates show preferential growth along (2 0 0) with smooth surface. However, films fabricated on sapphire substrates have better crystallization quality compared with that on La 3Ga 5SiO 14 (LGS) substrates according to the X-ray analysis. Films with sharper dips were observed on sapphire substrates in comparison with that on LGS substrates, which means a good confinement of the light in the corresponding mode.

Materials by design—exploiting the unique properties of pulsed laser deposition for the synthesis of novel hard materials and structures

Novel multilayer thin film structures with an (A–B–C–B) four-sublayer periodicity were synthesized using pulsed reactive crossed-beam laser ablation. The layers were based on transition metal carbonitrides in which one sublayer (A=TiC x N 1− x ) was optimized for its high hardness, another (C=ZrC x N 1− x ) for its low frictional properties, and a third (B=VC x N 1− x ) which acted as a barrier to dislocation propagation. Control of growth and stoichiometry was facilitated by using thermally stable gases as sources for the carbon and nitrogen which were activated by collisions with the ablation plasma. It was discovered that the ablation yields of Ti, V, and Zr were almost identical, so that the sublayer thickness was directly proportional to the number of ablated shots per sublayer metal. The four-sublayer structures were harder ( H ̄ =35 GPa) than corresponding bilayer structures ( H ̄ =30 GPa) in which the VC x N 1− x sublayers were missing. Further improvements are expected by optimizing the sublayer ratios and the absolute period thickness.

Electron microscopy of pulsed-laser-deposited thin films for tribological applications

Pulsed laser deposition (PLD) is a novel thin film deposition technique which has recently been applied to tribological materials with great success. PLD has several inherent advantages over conventional deposition techniques, including excellent film adhesion, replication of target chemistry, and low film deposition temperature. Because load-bearing materials are typically hardened, heat treated alloys, these properties of PLD are ideally suited for tribological applications. In addition to being a relatively simple deposition technique, considerable processing flexibility is inherent with PLD. Dense, nonporous, stoichiometric films of solid lubricants, such as MoS2, have been grown having long wear lives with low coefficients of friction. Hard coating materials, such as TiC, have been grown at room temperature that were polycrystalline and had excellent wear properties.A significant feature of pulsed laser deposited (PLD) thin films is the incorporation of spherical particles within the films. Figure 1 shows these particles embedded in a film of PLD MoS2 deposited at room temperature.