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We report on the structural, electrical, and optical properties of 5% niobium doped TiO2 thin films grown on various substrates by pulsed laser deposition. The epitaxial anatase Nb:TiO2 film on LaAlO3 is shown to be an intrinsic transparent metal and its metallic property arises from Nb substitution into Ti site as evidenced by the Rutherford backscattering channeling result. In contrast, the rutile Nb:TiO2 thin films show insulating behaviors with 2–3 orders higher room temperature electrical resistivity and ∼30 times lower mobility. A blueshift in the optical absorption edge is observed in both phases, though of differing magnitude. [ABSTRACT FROM AUTHOR]

We have investigated the defect structure in pure Co-doped and (Co, Nb)-doped TiO2 (anatase) thin films grown by pulsed laser deposition on (001) single crystal LaAlO3. Although both films exhibit room temperature ferromagnetism, dilute Nb doping significantly improves the conductivity and microstructure of the TiO2 (anatase) thin film at the cost of a lower saturation magnetization. Z-contrast imaging and electron-energy-loss-spectroscopy study in the scanning transmission electron microscope show cluster-free microstructure in the (Co, Nb)-doped thin film although Co is enriched into the surface and forms a CoxTi1-x-yNbyO2-δ phase. In contrast, metallic Co, rutile TiO2, and cobalt oxide nanoparticles combined with some crystallographic shear defect structures are observed in the pure Co-doped thin film. The magnetic behavior in each film can be explained with the presence of these defect states or second phases. [ABSTRACT FROM AUTHOR]

Discusses the preparation of superconducting thin films of y[sub1]-Ba[sub2]-Cu[sub3]-O[subx] with superconducting temperature and prepared by a laser deposition technique. Method used in film preparation; Effects of thermal stresses in the films; Composition of the film; Result of the x-ray powder diffraction of the films.

Presents a study that investigated the segregation of [sup 73]germanium and [sup 75]arsenic in pulsed-laser-melted carbon. Experimental results; Description of model calculations; Results of calculations; Discussion.

Presents a study which developed a model for pulsed laser melting of graphite. Method of the study; Results and discussion; Conclusion.

Presents a study which investigated film-substrate interactions of YBa[sub2]Cu[sub3]O[sub7-x] thin films grown by pulsed laser deposition on alkaline earth fluoride substrates. Experimental details; Results and discussion; Conclusion.

We report on the synthesis of low doping Zn1-xCoxO (0Al2O3 substrates. The films were prepared in an oxidizing atmosphere, using the pulsed-laser deposition technique starting from Zn and Co metallic targets. We first studied the influence of the strains of ZnO and their structural properties. Second, we investigated the structural and the magnetic properties of the Zn1-xCoxO films. We show that at low doping, the lattice parameters and the magnetization of the Zn1-xCoxO films depend strongly on the Co concentration. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The evolution of pulsed laser deposition had been an exciting process of invention and discovery, with the development of high Tc superconducting films as the main driver. It has become the method of choice in research and development for rapid prototyping of multicomponent inorganic materials for preparing a variety of thin films, heterostructures and atomically sharp interfaces, and has become an indispensable tool for advancing oxide electronics. In this paper I will give a personal account of the invention and development of this process at Bellcore/Rutgers, the opportunity, challenges and mostly the extraordinary excitement that was generated, typical of any disruptive technology. [ABSTRACT FROM AUTHOR]

The evolution of ZnO nanowires has been studied under supersaturation of Zn metal species with and without a ZnO thin-film buffer layer on α-Al2O3 deposited by the pulsed laser ablation technique. The nanowires had diameters in the range of 30 nm to 50 nm and lengths in the range of 5 μm to 10 μm with clear hexagonal shape and $$ [000\bar{1}] $$, $$ [10\bar{1}1] $$, and $$ [10\bar{1}0] $$ facets. X-ray diffraction (XRD) measurements indicated crystalline properties for the ZnO nanostructures grown on pulsed laser deposition (PLD) ZnO nucleation layers. The optical properties were analyzed by photoluminescence (PL) and cathodoluminescence (CL) measurements. The ZnO nanowires were found to emit strong ultraviolet (UV) light at 386 nm and weak green emission as observed by PL measurements. The stoichiometry of Zn and O was found to be close to 1 by x-ray photoelectron spectroscopy (XPS) measurements. The process-dependent growth properties of ZnO nanostructures can be harnessed for future development of nanoelectronic components including optically pumped lasers, optical modulators, detectors, electron emitters, and gas sensors. [ABSTRACT FROM AUTHOR]

Hafnium oxide (HfO2) thin films were deposited by the pulsed laser deposition (PLD) method on SiC substrates. The bandgap of HfO2 thin films was observed to be 5.8 eV. The chemical nature and stoichiometry of the films were analyzed by x-ray photoelectron spectroscopy (XPS). Metal-insulator-semiconductor (MIS) structures with Ni as a top electrode and TiN as a bottom electrode were fabricated to study the leakage current properties. The devices exhibited leakage current density of 50 nA/cm². The dielectric constant of these films is estimated to be in the range 17-24 from capacitance-voltage (C-V) measurements. The frequency dependence of the interface trapped charges is studied. [ABSTRACT FROM AUTHOR]

In order to obtain an enhancement of low field magnetoresistance (MR) in Nd/sub 0.7/Sr/sub 0.3/MnO/sub 3/ (NSMO) films, two kinds of superconducting flux focusing devices made of YBa/sub 2/Cu/sub 3/O/sub 7/ (YBCO) have been fabricated. In the superconducting state, YBCO expels magnetic flux from its interior and focuses the magnetic flux on a bridge of NSMO film. Using such a magnetic "lens", at temperatures below 77 K, /spl sim/900% enhancement in MR was observed. This corresponds to more than 15% change in the MR of NSMO in the presence of a couple of hundred Gauss. In order to successfully integrate high-T/sub c/ superconductivity with the magnetoresistive effect, bilayers of YBCO/NSMO were in situ deposited on (100) LaAlO/sub 3/ substrates by pulsed laser deposition so that the peak resistance temperature (T/sub p/) of NSMO was below the superconducting transition temperature (T/sub c/) of YBCO. X-ray diffraction and Rutherford Backscattering Spectroscopy (RBS) measurements provide evidence of epitaxial growth of YBCO/NSMO heterostructures. [ABSTRACT FROM PUBLISHER]

We studied the effects of Co doping on the intrinsic anisotropic properties of aligned a-axis YBa/sub 2/Cu/sub 3-x/Co/sub x/O/sub 7-/spl delta// films pulsed laser deposited on (100) LaSrGaO/sub 4/ substrates We used X-ray-absorption fine structure analysis and resistivity data to determine the quality of Co incorporation. Higher deposition pressures provided with better Co dopant incorporation but smaller grain size. However at lower pressures Co incorporation can still be achieved by down the cooling process. For transport along the c-direction, Co dopant causes reduction interlayer coupling as evidenced by an increase resistive anisotropy (/spl rho//sub c///spl rho//sub b/) with increasing level of Co incorporation, Co doping level of x=0.22 effectively doubles the resistive anisotropy of YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// films (from -18 to -40 at 100 K). [ABSTRACT FROM PUBLISHER]

We have pulsed laser deposited untwinned a-axis oriented YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// films on (100) LaSrGaO/sub 4/. From resistive measurements, the chain contribution to the total charge carrier density was estimated to be around 60%. Critical current density (J/sub c/) depends on the granular nature of the films and the transport across each grain boundary can be modeled as a collection of multiple parallel narrow conductive paths. Measurements in fields up to 6 T indicate that the behavior of J/sub c/ vs. B along the b- and c- directions is similar to that of standard c-axis films, with no significant weak link effects from the grain boundaries. We have also measured the temperature and magnetic field dependence of the critical current density (J/sub c/) along b- and c- directions of our films. The direction of magnetic field with respect to the crystallographic axes was found to be the dominant factor determining the J/sub c/. For supercurrents flowing along the c- direction, a cross-over from grain boundary pinning to surface and interface pinning was observed as temperatures approached T/sub c/. [ABSTRACT FROM PUBLISHER]

Pt/Pb(Zr/sub 0.5/Ti/sub 0.5/)O/sub 3//YBa/sub 2/Cu/sub 3/O/sub 7/ (Pt/PZT/YBCO) heterostructures were made by pulsed laser deposition on (100) SrTiO/sub 3/ or (100) LaSrGaO/sub 4/ substrates for studies of ferroelectric field effects in high-T/sub c/ superconducting thin films. X-ray diffraction data, including /spl Phi/ scans, indicated that the PZT layer grew with c-axis orientation epitaxially on top of the YBCO layers. Polarization measurements at room temperature and 77 K showed similar hysteretic loops in the PZT layer. The remanent polarization field can induce as many as 10/sup 14/ carriers/cm/sup 2/ in the bottom superconducting channel at the interface. Both c-axis and in-plane-aligned a-axis-oriented YBCO films, typically exhibiting zero resistance transition temperature of /spl sim/85 K, were used as superconducting channels. By polarizing the PZT film, a 2-5% change in both the channel resistance and the critical current at 77-85 K was obtained in /spl sim/100 nm thick films. Device operation at microsecond speeds was observed. [ABSTRACT FROM PUBLISHER]

Conductance-voltage characteristics of interfaces between a-axis YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) thin films and gold are presented. When the gold counter electrode is deposited in-situ, the junctions have a specific interface resistivity in the 10/sup -9/ /spl Omega/-cm/sup 2/ range, about an order of magnitude lower than nominal in-situ, c-axis YBCO/noble-metal junctions. As with nominal c-axis YBCO/noble-metal junctions, there is clear evidence at T=4 K for a peak in the conductance at low bias. In addition, a dip in the the middle of the broad peak structure was resolved. It appears to be a feature unique to the a-axis YBCO/Au interface. [ABSTRACT FROM PUBLISHER]

Presents information on a study which compared room temperature Raman spectra from a single-crystal-like film of YBa[sub2]Cu[sub3]O[sub7-y] fabricated by pulsed laser deposition, with similar spectra of a single crystal of YBa[sub2]Cu[sub3]O[sub7-y]. Description of the single crystals obtained as free-growing platelets from nonstoichiometric partial melts; Demonstration of the micro-Raman technique; Fabrication of the film used in the experiments.

Useful electronic, magnetic, and optical properties have been proposed and observed in thin films of Ti1-xMxO2 (M=Ta,Nb,V). In this work, we have studied phase formation for films of Ti1-xTaxO2 prepared by pulsed laser deposition. We show that substitutional Ta in TiO2 results in a different material system in terms of its electronic properties. Moss-Burstein shift is ruled out by comparing the electrical transport data of anatase and rutile TiO2. Vegard's law fit to the blueshift data and the high energy optical reflectivity studies confirm the formation of an alloy with a distinct band structure. [ABSTRACT FROM AUTHOR]

The authors performed a systematic study of the structural and electrical properties of Nb:TiO2 thin films by varying the substrate temperature (TS) and oxygen partial pressure (PO2). Niobium is found to incorporate easily and substitutionally into titanium lattice site as indicated by its low activation energy. By increasing TS, the carrier concentration (n) increases in the same way that niobium substitution fraction (s) increases, and the mobility increases as the structural quality is improved. With increasing PO2, n decreases dramatically though s does not change considerably. This may indicate that a large number of p-type native defects form, which “kill” the electrons produced by the Nb donors. [ABSTRACT FROM AUTHOR]

Thin films of Nb-doped SrTiO3 (NSTO) are grown via pulsed laser deposition (PLD) on LaAlO3 (LAO,001), MgAl2O4 (MAO,001), SrTiO3 (STO,001), and Y-stabilized ZrO2 (YSZ,001) substrates. The effects of the film-substrate lattice mismatch, film thickness, and substrate temperature during growth on the film properties are investigated. The electrical transport in NSTO films is shown to exhibit a strong sensitivity to strain, which is suggested to arise from the dependence of carrier mobility on bond distortions/stretching and related changes in phonon modes. [ABSTRACT FROM AUTHOR]

We report on the growth of highly oriented HfO2 thin films of monoclinic phase stabilized by 5% Co doping on (001) yttrium-stabilized zirconia (YSZ) using pulsed-laser deposition at 700 °C at an oxygen partial pressure of 10-4 Torr. On the other hand, pure HfO2 of such quality did not grow on YSZ in wide range of growth parameters. Rutherford backscattering-ion channeling in this film showed a 24% minimum yield (χmin) indicating highly oriented film growth, while hardly any ion channeling was observed in the undoped sample. High-resolution transmission electron microscopy revealed a sharp interface, and no signature of Co clusters. Electron energy loss spectroscopy showed that Co is in the 2+ state. Attempts were also made to grow films on a (001) Si substrate, and the results showed a very low ion channeling yield (∼8%). [ABSTRACT FROM AUTHOR]

We present the results of Raman and photoluminescence studies on epitaxial anatase phase Ti[sub 1-x]Co[sub x]O[sub 2] films for x=0–0.07, grown by pulsed-laser deposition. The low-doped system (x=0.01 and 0.02) shows a Curie temperature of 700 K in the as-grown state. The Raman spectra from the doped and undoped films confirm their anatase phase. The photoluminescence spectrum is characterized by a broad emission from self-trapped excitons (STE) at 2.3 eV at temperatures below 120 K. This peak is characteristic of the anatase-phase TiO[sub 2] and shows a small blueshift with increasing doping concentration. The Co-doped samples show two spin-flip emission lines at 2.77 and 2.94 eV. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Thin films of 5% Co doped Cu[SUB2]O were grown on single-crystal (001) MgO substrates by pulsed-laser deposition, without and with 0.5% codoping with Al, V, or Zn. Structural, electrical, and magnetic properties were studied. The films showed phase-pure character under the chosen optimum growth conditions. Spin-glass-like behavior was observed in Co-doped films without codoping. A clear ferromagnetic signal at room temperature was found only in the case of Co:Cu[SUB2]O films codoped with Al. [ABSTRACT FROM AUTHOR]

Studies the effects of annealing and strain on La[sub 1-x]Ca[sub x]MnO[sub 3] thin films. Deposition of the thin films onto (100)-oriented LaAlO[sub 3] substrates using the pulsed laser deposition technique; Physical properties of the as-grown films.

Studies the influence of oxygen pressure on the epitaxy, surface morphology and optoelectronic properties of zinc oxide (ZnO) thin films grown on sapphire by pulsed-laser deposition. Rutherford backscattering and ion channeling in conjuction with atomic force microscopy; Impact of growth and defects on electron mobility, free-electron concentration and luminescence.

The microstructure of in situ epitaxially grown Y-Ba-Cu-O thin films on (001) SrTiO3 substrates was studied using cross-sectional transmission electron microscopy. The films, prepared by pulsed laser deposition at substrate holder temperature of 650 °C without post-annealing, exhibit zero resistivity above 90 K and critical currents exceeding 106 A/cm2 at 77 K. The films are of heavily faulted single crystalline structure with the c axis approximately perpendicular to the substrate (001) surface. We suggest that, due to the fast quenching and low substrate temperature, crystalline defects and chemical fluctuations are locked into a faulted structure after each laser pulse. Despite their rather imperfect microstructure, the films are free from macroscopic grain boundaries and secondary phases and possess superb superconducting properties. [ABSTRACT FROM AUTHOR]

We have grown ultrathin films of Y1Ba2Cu3O7-x in situ on (001) SrTiO3 by pulsed laser deposition. The zero resistance transition temperature (Tc0) is >90 K for films >300 Å thick. The critical current density (Jc at 77 K) is 0.8×106 A/cm2 for a 300 Å film and 4–5×106 A/cm2 for a 1000 Å film. The Tc0 and Jc deteriorate rapidly below 300 Å, reaching values of 82 K and 300 A/cm2 at 77 K, respectively, for a 100 Å film. Films only 50 Å thick exhibit metallic behavior and possible evidence of superconductivity without showing zero resistance to 10 K. These results are understood on the basis of the defects formed at the film-substrate interface, the density of which rapidly decreases over a thickness of 100 Å. We have studied these defects by ion channeling measurements and cross-section transmission electron microscopy. Our results suggest that the superconducting transport in these films is likely to be two dimensional in nature, consistent with the short coherence length along the c axis of the crystals. [ABSTRACT FROM AUTHOR]

The pulsed laser thin-film deposition process can enable preparation of thin films of complex composition with good control over the film stoichiometry. The film compositions are similar to that of the target pellet and as a consequence this technique appears to be an ideal method for preparing high Tc thin films on a variety of substrates.The factors which contribute to this beneficial phenomenon have been explored by a laser ionization mass spectrometry (LIMS) and a post ablation ionization (PAI) neutral velocity analysis technique in order to determine the mass and velocities of the laser ejected material. In addition, x-ray absorption measurements on films deposited onto substrates at room temperature were performed in order to identify the presence of short-range crystalline order in the films. Both of these studies rule out the ejection of stoichiometric clusters of material from the pellet during the laser ablation/deposition process. Instead, binary and ternary suboxides are emitted from the target pellet. These suboxides most likely have unit sticking coefficient to the substrate which could contribute to the preservation of the film stoichiometry. The velocity distribution of several neutral species (e.g., BaO) indicates that particles have energies of several eV. Thus the effective temperatures of the emitted species are ∼15×103 K, and these energetic particles may facilitate growth of the crystalline films at low substrate temperatures. [ABSTRACT FROM AUTHOR]

Focuses on the use of the pulsed laser deposition (PLD) technique in the United States. Industrial applications of PLD; Concept behind thin-film deposition; Benefits of PLD.

Examines the growth of crystalline quality epitaxial gallium nitride thin films by pulsed laser deposition. Generation of an x-ray diffraction rocking curve linewidth; Indication of the crystallinity degree by the ion channeling minimum yield; Reflection of gallium desorption in a decreasing growth rate.

Thin superconducting films of Y-Ba-Cu-O were prepared at 650 °C using the pulsed laser deposition technique. The as-deposited films were fully superconducting at low temperature (30 K). After annealing in oxygen at 450 °C for 3 h, the films exhibited superconductivity with zero resistance at temperatures as high as 83 K. Film-substrate interface reaction was minimal as revealed by Rutherford backscattering and Auger electron spectrometry. These films processed at such low temperatures are also found to have excellent planar surface morphology and high critical current density. [ABSTRACT FROM AUTHOR]

Etching of Y-Ba-Cu-O superconducting thin films has been accomplished using a pulsed excimer laser (248 nm, 30 ns). Etch depth as a function of the number of laser pulses was linear over a wide range of incident laser energy densities. An etch threshold energy density of 0.11 J/cm2 was observed and etch rate per pulse scaled linearly with the logarithm of the incident energy density. The dependence is adequately explained by a linear absorption model with an inverse absorption length of 2.3×105 cm-1. [ABSTRACT FROM AUTHOR]

Examines the morphology and microstructure of Nd[sub 1.85]Ce[sub 0.15]CuO[sub 4-y] superconductors grown epitaxially by pulsed laser deposition. Use of electron diffraction and high resolution electron microscopy; Composition of the films; Absence of polytypoidic faulting.

Describes the in situ fabrication of superconducting Y[sub 1]ba[sub 2]Cu[sub 3]O[sub 7-x]/Nd[sub 1.85]Ce[sub 0.15]CuO[4-y] bilayer thin films by pulsed laser deposition. Use of nitrogen oxide as reactive gas; Phase coherence between the superconductors.

Utilizes the pulsed laser deposition in growing the YBA[sub 2]Cu[sub 3]O[sub 7-delta] (YBCO) films. Absence of significant weak-link effects in the films; Superconductivity of the nominal 1-unit cell thick YBCO layer.

We have grown YBa2Cu3O7-x-PrBa2Cu3O7-y heterostructures with the perovskite a axis normal to the surface of a variety of (001) oriented substrates using the pulsed laser deposition technique. X-ray diffraction studies indicate little or no formation of the traditional c-axis normal orientation usually nucleated on these substrates, while ion channeling, transmission electron microscopy (TEM), and Raman scattering studies reveal a highly ordered crystalline structure similar in quality to that obtained in the best c-axis oriented films. Superconducting transition temperatures, for current transport in the plane of the films, consistently exceed 80 K, but are probably lower than the optimum 92 K transition expected for YBa2Cu3O7-x due to the presence of growth twin boundaries between grains with the c axis oriented along the two substrate directions. [ABSTRACT FROM AUTHOR]

The changes in the superconducting properties of in situ pulsed laser deposited Y1Ba2Cu3O7-x thin films caused by irradiation with 200 keV He+ ions are due to both oxygen loss as well as oxygen and cationic displacements induced by the irradiation. This is demonstrated by a study of the recovery of these defects by plasma oxidation and relatively low temperature (∼600 °C) annealing in oxygen. Plasma oxidation of films irradiated to low fluences enables the replacement of oxygen atoms in the lattice, leading to a substantial recovery of Tc0, Jc, and normal state resistivity. Irradiation-induced oxygen and cationic displacements and other microscopic defects can be further annealed out at relatively low temperatures leading to an almost full recovery of Tc0, Jc, and normal state resistivity. A transmission electron microscope study of irradiated films shows evidence that they are structurally disordered. [ABSTRACT FROM AUTHOR]

The regrowth of an oxygen-implanted YBa2Cu3O7-δ thin film was studied by Rutherford backscattering, ion channeling, and x-ray diffraction studies. The atomic composition of the thin film was preserved even after a 1 h anneal at 990 °C, reflecting the high chemical stability of the material obtained by the pulsed laser deposition technique. Two distinct activation energies were determined during the regrowth process: 0.42±0.04 eV at lower temperatures, corresponding to epitaxial growth from the interface, and 0.18±0.03 eV at higher temperatures, presumably associated with homogeneous nucleation and reorientation. [ABSTRACT FROM AUTHOR]

Superlattices of YBa2Cu3O7-x/YyPr1-yBa2Cu3O7-x(y=0.8 and 0.0) have been successfully grown in situ on MgO and LaAlO3 by using a multitarget pulsed laser deposition system. Satellite peaks have been observed in x-ray diffraction for the superlattices with modulation wavelengths from about few tens of angstroms to few hundred angstroms. The x-ray diffraction measurements also indicate that the multilayers have c axis normal to the substrates. Good crystallinity has been observed in the superlattices with He ion backscattering minimum yields of about 10%, indicating highly oriented growth. The presence of a periodic layer structure was further confirmed by the observation of composition oscillations in these structures by secondary-ion mass spectrometry. [ABSTRACT FROM AUTHOR]

We have fabricated Josephson weak links from in situ laser-deposited four-layer structures of YBa2Cu3O7-x/PrBa2Cu3O7-x/YBa2Cu3O7-xAu. These devices show superconductor/normal-metal/superconductor-like current-voltage characteristics with good areal scaling of both the critical currents Ic and resistances Rj, with IcRj≊3.5 mV. Constant-voltage current steps observed in response to 84 GHz mm-wave radiation and modulation of the dc supercurrent in a transverse magnetic field demonstrate that both the ac and dc Josephson effects occur in these devices. [ABSTRACT FROM AUTHOR]

We report, for the first time, growth of thin films of Y-Ba-Cu-O by pulsed laser deposition onto [001] YbFeO3 single-crystal substrates. A Tc,0 of 88 K was obtained along with a critical current greater than 105 A/cm2 at 77 K. X-ray diffraction shows epitaxial growth of the 1-2-3 phase with the c axis oriented normal to the substrate plane. Rocking curve measurements show a 0.5° full width at half maximum, indicating good alignment of the layered structure. The composition was verified by Rutherford backscattering, while channeling results reveal a 17% yield, consistent with the rocking curve measurements. Growth of thin films of 1-2-3 on a magnetic substrate may open the way for potentially new applications. [ABSTRACT FROM AUTHOR]

High oxygen partial pressure has been found to be an important parameter for the pulsed laser deposition of as-deposited superconducting thin films with high Tc and Jc. The optical emissions from both elemental and oxide species ejected from the target of YBa2Cu3O7-x during the pulsed laser deposition process increase with the oxygen pressure, with the oxide emission showing a stronger pressure dependence than the elemental emission. The dynamics of the interaction between the oxygen atoms and the species in the laser-produced plume were studied by a wavelength and time-resolved measurement. The results are qualitatively explained using a simple model based on optical emission arising from inelastic and recombination collision between the elemental species and electronically excited oxygen atoms. The formation of oxides in the plume is shown to be essential for the production of higher quality superconducting films, indicating the value of optical spectroscopy as a diagnostic tool. [ABSTRACT FROM AUTHOR]

Iron oxide films have been deposited on alumina substrates by pulsed ruby laser evaporation from a bulk α-Fe2O3 pellet. The films have been characterized by using the techniques of conversion electron Mössbauer spectroscopy, Rutherford backscattering, and scanning electron microscopy. It is demonstrated that the stoichiometry of the deposited film can be varied between FeO and Fe3O4 by controlling the oxygen partial pressure during deposition over a range from 5×10-7 to 10-4 Torr. It is further shown that the Fe3O4 film can be converted into γ-Fe2O3 by suitable thermal annealing treatment. [ABSTRACT FROM AUTHOR]

Growth of MgB[sub 2] thin films by pulsed laser deposition is examined under ex situ and in situ processing conditions. For the ex situ process, boron films grown by pulsed laser deposition were annealed at 900 °C with excess Mg. For the in situ process, different approaches involving ablation from a stoichiometric target under different growth conditions, as well as multilayer deposition involving interposed Mg layers were examined and analyzed. Magnetic measurements on ex situ processed films show T[sub c] of ∼39 K, while the current best in situ films show a susceptibility transition at ∼22 K. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Single-phase PrBa[sub 0.7]Sr[sub 1.3]Cu[sub 3]O[sub 7] thin films with the Sr dopant concentration exceeding the solid solubility limit were epitaxially grown on (001) SrTiO[sub 3] and (001) LaAlO[sub 3] substrates by pulsed laser deposition (PLD) method. The resistivity of the doped films grown on LaAlO[sub 3] was significantly lower than that of PrBa[sub 2]Cu[sub 3]O[sub 7]. For most of the films grown on SrTiO[sub 3], the resistivity was higher than that of PrBa[sub 2]Cu[sub 3]O[sub 7]. The results were explained by considering the Sr-doping effect and lattice-mismatch-induced strain effect. This work shows the potential of PLD to grow single-phase films with the dopant concentration exceeding the solid solubility limit. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report the electronic structures of Ta-doped anatase TiO2 thin films grown by pulsed laser deposition (PLD) with varying magnetization using a combination of first-principles calculations and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy. The roles of Ta doping and Ti vacancies are clarified, and the observed room-temperature ferromagnetism is attributed to the localized magnetic moments at Ti vacancy sites ferromagnetically ordered by electron charge carriers. O K-edge spectra exhibit significant polarization dependence which is discussed and supported by first-principles calculations in relation to both the crystal symmetry and the formation of defects. In particular, anomalous spectral-weight transfer across the entire O K edge for the ferromagnetic thin film is associated exclusively with the occurrence of Ti vacancies and strong correlation effects, which result in the enhancement of the direct interaction between oxygen sites and of the anisotropy of the eg-pσ hybridizations in the out-of-plane component. Our results show that O K-edge NEXAFS spectra can provide reliable experimental probes capable of revealing catiomc defects that are intimately related to the ferromagnetism in transition metal oxides. [ABSTRACT FROM AUTHOR]

We report optical, electrical and magnetotransport properties of oxygen deficient SrTiO3 (SrTiO3-x) thin films fabricated by pulsed laser deposition technique. The oxygen vacancies (Ovac) in the thin film are expected to be uniform. By comparing its electrical properties to those of bulk SrTiO3-x, it was found that Ovac in bulk SrTiO3-x is far from uniform over the whole material. The metal-insulator transition (MIT) observed in the SrTiO3-x film was found to be induced by the carrier freeze-out effect. The low temperature frozen state can be reexcited by Joule heating, electric and intriguingly magnetic field. [ABSTRACT FROM AUTHOR]

Abstract: Wide band gap InGaZn6O9 films of thickness ~350 nm were deposited on sapphire (0001) at room temperature by using the pulsed laser deposition technique. The transparent films showed the optical transmission of >80% with the room temperature Hall mobility of ~10 cm2/V s and conductivity of 4×102 S/cm at a carrier density >1020 cm−3. The electrical properties as a function of deposition temperatures revealed that the conductivity and mobility almost retained up to the deposition temperature of 200 °C. The films annealed in different atmospheres suggested oxygen vacancy plays an important role in determining the electrical conductivity of the compound. Room temperature grown heterostructure of n-InGaZn6O9/p-SiC showed a good rectifying behavior with a leakage current density of less than 10− 9 A/cm2, current rectifying ratio of 105 with a forward turn on voltage ~3 V, and a breakdown voltage greater than 32 V. [Copyright &y& Elsevier]

Abstract: Hexagonal and cubic Mg x Zn1−x O thin films corresponding to optical band gaps of 3.52eV, 4eV and 6.42eV for x =0.15, 0.28 and 0.85 compositions were grown by pulsed laser deposition technique. The crystalline quality of the films was investigated by X-ray diffraction–rocking curve measurements and indicated a high degree of crystallinity with narrow FWHM’s of 0.21°–0.59°. Rutherford back scattering–channeling spectroscopy provides channeling yields of 7–14% indicating the good crystalline quality of the thin films. X-Ray photoelectron spectroscopy measurements clearly indicated different level of oxidation states of Mg and Zn. [Copyright &y& Elsevier]

Abstract: Interfacial stress is thought to have significant effects on electrical and oxygen transport properties in thin films of importance in solid oxide fuel cell applications. We investigate how in-plane biaxial stress modifies the electronic structure of La2/3Ca1/3MnO3 and La1/2Sr1/2MnO3 thin films prepared by pulsed laser deposition on three different substrates to vary the in-plane stress from tensile to compressive. The electronic structure was probed by X-ray absorption spectroscopy of the Mn L2,3-edge to characterize the interfacial disruption in this region in an element-specific, site-specific manner. The compressive or tensile interfacial strain modifies the relative concentrations of La and Sr in the interfacial region in order to achieve a better lattice match to the contact material. This atomic migration generates an interfacial region dominated by a compound with a single valency for the transition metal ion, resulting in a severe barrier to oxygen and electron transport through this region. [Copyright &y& Elsevier]