Laser ablation of solid targets in the liquid medium can be realized to fabricate nanostructures with various compositions (metals, alloys, oxides, carbides, hydroxides, etc.) and morphologies (nanoparticles, nanocubes, nanorods, nanocomposites, etc.). At the same time, the post laser irradiation of suspended nanomaterials can be applied to further modify their size, shape, and composition. Such fabrication and modification of nanomaterials in liquid based on laser irradiation has become a rapidly growing field. Compared to other, typically chemical, methods, laser ablation/irradiation in liquid (LAL) is a simple and “green” technique that normally operates in water or organic liquids under ambient conditions. Recently, the LAL has been elaborately developed to prepare a series of nanomaterials with special morphologies, microstructures and phases, and to achieve one-step formation of various functionalized nanostructures in the pursuit of novel properties and applications in optics, display, detection, and biological fields. The formation mechanisms and synthetic strategies based on LAL are systematically analyzed and the reported nanostructures derived from the unique characteristics of LAL are highlighted along with a review of their applications and future challenges.

Nanomaterials via Laser Ablation/Irradiation in Liquid: A Review

The observation of ferromagnetism in magnetic ion doped II–VI diluted magnetic semiconductors (DMSs) and oxides, and later in (Ga,Mn)As materials has inspired a great deal of research interest in a field dubbed “spintronics” of late, which could pave the way to exploit spin in addition to charge in semiconductor devices. The main challenge for practical application of the DMS materials is the attainment of a Curie temperature at or preferably above room temperature to be compatible with junction temperatures. Among the studies of transition-metal doped conventional III–V and II–VI semiconductors, transition-metal-doped ZnO and GaN became the most extensively studied topical materials since the prediction by Dietl et al., based on mean field theory, as promising candidates to realize a diluted magnetic material with Curie temperature above room temperature. The underlying assumptions, however, such as transition metal concentrations in excess of 5% and hole concentrations of about 1020 cm−3, have not gotten as much attention. The particular predictions are predicated on the assumption that hole mediated exchange interaction is responsible for magnetic ordering. Among the additional advantages of ZnO-and GaN-based DMSs are that they can be readily incorporated in the existing semiconductor heterostructure systems, where a number of optical and electronic devices have been realized, thus allowing the exploration of the underlying physics and applications based on previously unavailable combinations of quantum structures and magnetism in semiconductors. This review focuses primarily on the recent progress in the theoretical and experimental studies of ZnO- and GaN-based DMSs. One of the desirable outcomes is to obtain carrier mediated magnetism, so that the magnetic properties can be manipulated by charge control, for example through external electrical voltage. We shall first describe the basic theories forwarded for the mechanisms producing ferromagnetic behavior in DMS materials, and then review the theoretical results dealing with ZnO and GaN. The rest of the review is devoted to the structural, optical, and magnetic properties of ZnO- and GaN-based DMS materials reported in the literature. A critical review of the question concerning the origin of ferromagnetism in diluted magnetic semiconductors is given. In a similar vein, limitations and problems for identifying novel ferromagnetic DMS are briefly discussed, followed by challenges and a few examples of potential devices.

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Ferromagnetism of ZnO and GaN: A Review

Significance of calcium phosphate coatings for the enhancement of new bone osteogenesis – A review ☆

Pulsed laser deposition (PLD) is a conceptually and experimentally simple yet highly versatile tool for thin-film and multilayer research. Its advantages for the film growth of oxides and other chemically complex materials include stoichiometric transfer, growth from an energetic beam, reactive deposition, and inherent simplicity for the growth of multilayered structures. With the use of PLD, artificially layered materials and metastable phases have been created and their properties varied by control of the layer thicknesses. In situ monitoring techniques have provided information about the role of energetic species in the formation of ultrahard phases and in the doping of semiconductors. Cluster-assembled nanocrystalline and composite films offer opportunities to control and produce new combinations of properties with PLD.

Synthesis of Novel Thin-Film Materials by Pulsed Laser Deposition

The growth and characterization of functional oxide thin films that are ferroelectric, magnetic, or both at the same time are reviewed. The evolution of synthesis techniques and how advances in in situ characterization have enabled significant acceleration in improvements to these materials are described. Methods for enhancing the properties of functional materials or creating entirely new functionality at interfaces are covered, including strain engineering and layering control at the atomic-layer level. Emerging applications of these functional oxides such as achieving electrical control of ferromagnetism and the future of these complex functional oxides is discussed.

/pdf/advances-in-the-growth-and-characterization-of-magnetic-1r6yol3qt6.pdf

Advances in the growth and characterization of magnetic, ferroelectric, and multiferroic oxide thin films

Manganites of the series , with x = 0, 0.1, 0.3, 0.5, 0.7 and 1.0, have been characterized in ceramic form and thin films have been prepared by pulsed laser deposition. Characterization techniques included x-ray diffraction, conductivity and magnetoresistance, magnetization and susceptibility, optical spectroscopy and the Faraday effect. Both the films and ceramics exhibit a maximum low-temperature conductivity at which is coexistent with ferromagnetic order. The negative magnetoresistance effect is qualitatively different for the x = 0.3 and x = 0.5 compositions. For x = 0.3 the magnetoresistance peak occurs around the Curie point, whereas for x = 0.5 the onset of magnetoresistance is somewhat below and increases monotonically as . The applied field appears to modify the magnetic order (on the scale of the spin diffusion length) down to the lowest temperatures for x = 0.5, but for x = 0.3 the ferromagnetic order is essentially complete and collinear below the Curie point.

Pulsed laser deposition of thin films of (

The reaction between nitrogen gas and the series of R2Fe17 intermetallic compounds is studied by thermopiezic analysis on micron‐size powders. Nitrogen diffusion in the range 300–550 °C can be represented by an activated interstitial diffusion process D=D0e−Em/kT with D0=1.95×10−10 m2 s−1 and an activation energy Em=0.81 eV. This stage of the nitrogenation reaction leads to the formation of R2Fe17N3−δ nitrides which have structures related to those of the parent compounds. Heating above about 800 °C leads to complete disproportionation of the compounds into a mixture of rare‐earth nitride and iron.

Nitrogenation of R2Fe17 compounds: R=rare earth

Thin films of (La1−xCax)MnO3 prepared by laser ablation deposition are ferromagnetic when 0.2≤x≤0.5 with Tc≊250 K. These films show strong Faraday rotation both in the vicinity of the 2p(O)→3d(Mn) charge‐transfer absorption at approximately 3.0 eV (θF≳40 000°/cm), and in the vicinity of the 3d(t2g)→3d(eg) excitation at approximately 1.5 eV (θF≳10 000°/cm just below Tc). The films are moderately transparent, having values of 2θF/α of approximately 0.1 at 1.5 eV and 0.5 at 3.0 eV.

Magneto‐optic Faraday effect in (La1−xCax)MnO3 films

The authors report on the synthesis of thin films of the BiSrCaCuO family by single-target pulsed laser deposition. The post annealing (ex situ) technique normally leads to very granular films. For Bi2Sr2CaCu2O8+ delta (2212) films prepared in this way, the resistivity drops abruptly at temperatures in the range 80-85 K. Post-annealed Bi2Sr2Ca2Cu3O10+ delta (2223) films could only be obtained in a very narrow annealing temperature window. They all contained the secondary 2212 phase and therefore displayed a two-step resistivity drop at 110 K and 80 K. Moreover, all the ex situ films display a resistive tail at lower temperatures due to their granularity. In situ crystallized films have very flat surfaces, but have poorer superconducting properties than ex situ films. The resistive transitions are broader, but there is no resistive tail at lower temperatures. They suggest that this behaviour could be due to inhomogeneities in the oxidation process during deposition. The first results on the in situ preparation of 2223 show that a substantial quantity of the 2223 phase can be obtained, but the resistive transitions remain very broad. The ex situ results suggest that the deposition conditions for optimizing the in situ formation of the 2223 phase may need to be closely defined.

https://iopscience.iop.org/article/10.1088/0953-2048/6/7/007/pdf

Synthesis of BiSrCaCuO thin films by in situ and ex situ pulsed laser deposition

In Bi 2 Sr 2 CaCu 2 O 8 , hydrogen absorption at 1 bar occurs in three stages starting at approximately 275°C, 500°C and 600°C. Only the first stage occurs without decomposition of the compound or a change in structure; there is an increase in cell volume of 1.1 A 3 (H atom) −1 up to approximately 2 H atoms per formula unit. The diamagnetic a.c. susceptibility is reduced by more than a factor of two with the absorption of 1.1 H atoms per formula unit, but the onset of superconductivity at 87 K is depressed by no more than 3 K. A possible explanation is that hydrogen accepts electrons from the 6p(Bi) pocket and resides in the (BiO) 2 double layers; physical decrepitation then greatly increases the surface to volume ratio thereby increasing the volume fraction lying within the penetration depth.

J.F. Lawler

Papers

Pulsed laser deposition of thin films of (

Nitrogenation of R2Fe17 compounds: R=rare earth

Magneto‐optic Faraday effect in (La1−xCax)MnO3 films

Synthesis of BiSrCaCuO thin films by in situ and ex situ pulsed laser deposition

Hydrogen absorption in single-crystal Bi2Sr2CaCu2O8 and its effect on superconductivity