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The effect of 200 MeV Ag ion irradiation on the temperature and field dependence of critical current density (JC) of high quality MgB2 thin films is studied. Substantial increase in JC is observed over a certain field range for the film irradiated at a dose of 1012 ions/cm2. Our analysis suggests that columnar defects are not formed under irradiation conditions used in these studies, which correspond to an electronic energy loss of about 16 keV/nm. Defects clusters are likely to be responsible for the observed improvement in JC.

Transparent conducting films of SnO2 are grown on single-crystal R-Al2O3 substrates by the pulsed electron beam deposition (PED) technique, and their electrical, optical, and microstructural properties are compared with the films grown by pulsed-laser deposition (PLD). In PED, the pulsed electron beam used for ablation is generated by a channel-spark system with discharge voltage of 12 kV, current ∼1 kA, and pulse duration of ∼100 ns. The PED films are highly oriented, show good epitaxy, and are highly transparent with transmittance of ∼80% in the visible and IR range. The measured band gap is close to 3.9 eV. It is shown that the PED film properties compare well with those of PLD films, with the 119Sn Mossbauer spectroscopy showing comparable local environments in the two.

An all-perovskite ferroelectric field-effect transistor with a ferroelectric Pb(Zr0.2Ti0.8)O3 (PZT) gate and a colossal magnetoresistive La0.8Ca0.2MnO3 (LCMO) channel has been successfully fabricated by pulsed-laser deposition on Si. A clear and square channel resistivity hysteresis loop, commensurate with the ferroelectric hysteresis loop of PZT, is observed. A maximum modulation of 20% after an electric field poling of 1.5×105 V/cm, and 50% under a magnetic field of 1 T, are achieved near the metal-insulator transition temperature of the LCMO channel. A data retention time of at least one day is measured. The effects of electric and magnetic fields on the LCMO channel resistance are discussed within the framework of phase separation scenario.

An experimental scheme is devised and demonstrated to realize integration of porous silicon with free standing CVD diamond. Laser Raman spectroscopy, atomic force microscopy, photoluminescence spectroscopy and scanning electron microscopy are used to bring out the nature and quality of the integration achieved.

We have grown high quality a-axis oriented YBa/sub 2/Cu/sub 3/O/sub 7-x//PrBa/sub 2/Cu/sub 3/O/sub 7-y/ films on [100] LaSrGaO/sub 4/ substrates. We have optimized the crystalline orientation and the superconducting properties of our films. We have performed annealing studies on a- and c-axis films in vacuum and oxygen to compare the oxygen depletion of the films and found that T/sub c/ degradation of a-axis films is comparable to that of c-axis films. To further optimize the a-axis films for trilayer junction fabrication, we significantly reduced the surface roughness of the films by a gradual lowering of oxygen pressure during the deposition. >

Thin films of YBa/sub 2/Cu/sub 3-x/Fe/sub x/O/sub 7-y/ (0/spl les/x/spl les/0.2) were made by pulsed laser deposition using different O/sub 2/ pressures and annealing times. Their microwave absorption was measured and shows that the preparation conditions have a profound effect on the surface resistance. That is, if the Fe incorporation was successful, the microwave absorption had a large peak near T/sub c/. Various other diagnostics such as X-ray, ac susceptibility and atomic-force microscopy have also been performed. >

Epitaxial c-axis-oriented thin films of Fe- or Zn-doped YBa 2 Cu 3 O 7-δ have been grown on (001) LaAlO 3 substrates by pulsed excimer laser ablation. Adequate substitutional incorporation of Fe atoms required optimal choice of oxygen pressure during deposition as well as a postsynthesis annealing treatment at 550 °C. Zn incorporation did not require such special processing conditions. The resistivity transitions for such high-quality well-characterized films were studied at different magnetic fields up to 5 T. Analysis of T c depression and change in dH c2 /dT at T c has been made in terms of the possible changes in the density of states at the Fermi level, contributions of the exchange field, magnetization field, and nonmagnetic scattering. Estimates of the activation energy [U 0 (H)] for vortex motion have also been made.

Ferromagnetism is observed at and above room temperature in pulsed laser deposited epitaxial films of Co-doped Ti-based oxide perovskite (La1-xSrxTiO3-d). The system has the characteristics of an intrinsic diluted magnetic semiconductor (metal) at low concentrations (

Diamond like carbon films and C-N films were prepared using ion beam assisted deposition technique (IBAD). Tribological properties were studied by subjecting DLC coated films to the accelerated wear tests. These tests indicated a significant improvement in the mechanical surface properties of glass by DLC coating. Better wear features were obtained for thinner DLC coating as compared to the thicker ones. We also studied the optical properties and obtained a band gap of 1·4 eV for these films. An attempt was made to prepare C3N4 films by using IBAD. We observed variation in the nitrogen incorporation in the film with the substrate temperature.

EXAFS spectra have been measured at the Cu K edge in Fe- and Zn-doped YBa2Cu3O7- delta using a laboratory EXAFS spectrometer. The dopant concentration was varied and the changes in the near-neighbour environment around the Cu ions were examined by determining the best-fit structural parameters after curve fitting to the first-shell EXAFS function. The average Cu-O distance is found to decrease as Fe concentration increases, and is found to increase as Zn concentration increases. The results indicate that Fe and Zn affect the Cu-O environment significantly but in different ways. The mobile hole concentration in the YBa2Cu3O7- delta superconductor is known to change with doping, and our results indicate that the Cu-O distance and the mobile hole concentration are probably related, the Cu-O distance increasing as mobile hole concentration decreases and vice versa.

Thin films of carbon were deposited onto tungsten substrates using laser-induced physical vapour deposition (LPVD) from a high purity pyrolitic graphite target. An excimer laser was used for the deposition of these films. The films were irradiated with Ar + ions up to an ion dose of 1 × 10 16 ions cm -2 to promote ion beam induced atomic mixing at the W-C interface. Since the state of the mixed region is expected to be metastable, the possibility of transformation of this state to a more ordered state via thermal annealing treatment was explored. These treatments clearly revealed the formation of tungsten carbide at the interface. X-ray diffraction (XRD) studies were performed at every stage of processing using a low angle XRD technique. Scanning electron microscopy was used for qualitative characterization of the surface morphology of samples. The microhardness was measured using a conventional Vicker's microhardness testing machine.

A Monte Carlo simulation study is performed to examine the effects of near-surface nonstoichiometry in a mixed-valent manganite (e.g., La0.7A0.3MnO3, where A=Sr, Ca) on the magnetization of its surface, and that of a few layers underneath. The nonstoichiometry is introduced either in the form of oxygen vacancy gradient or a gradient in the La:A ratio. The corresponding gradient in the exchange constant J is incorporated phenomenologically from the known phase diagram [P. Schiffer et al., Phys. Rev. Lett. 75, 3356 (1995)]. We show that the near-surface nonstoichiometry can account for the temperature dependence of magnetization of the surface layers as revealed by photoemission and x-ray magnetic circular dichroism (X-MCD) experiments [J. Park et al., Nature (London) 392, 794 (1998); J. Park et al., Phys. Rev. Lett. 81, 1953 (1998)]. The demagnetization shows viscous fingeringlike protrusions which may have important consequences for spin-polarized transport across interfaces.

Both ferromagnetic (FM) and charge-ordered domain structures of (La/sub 1-x/Pr/sub x/)/sub 0.67/Ca/sub 0.33/MnO/sub 3/ thin film were detected by magnetic force microscopy (MFM) and electric force microscopy (EFM) operated at low temperatures near the peak resistance temperature (T/sub p/). The in-plane-like FM domains of submicrometer size emerge below T/sub p/, and their magnetic interaction with an MFM tip becomes stronger as the temperature is reduced. Charge-ordered insulating regions have the strong electrostatic interaction with an EFM tip near T/sub p/, and the interaction correlates well with the temperature dependence of resistivity of the film.

The development of self-assembled magnetic CoFe2O4 nanoparticles within polymer matrices at room temperature is reported. Diblock copolymers consisting of poly (norbornene) and poly (norbornene-dicarboxcylic acid) (NOR/NORCOOH) were synthesized. The self-assembly of the mixed metal oxide within the NORCOOH block was achieved at room temperature by processing the copolymer nanocomposite using wet chemical methods. Morphology and magnetic properties were determined by superconducting quantum interference device magnetometry, transmission electron microscopy, wide angle x-ray diffraction, and 57Fe Mossbauer spectroscopy. The CoFe2O4 nanoparticles are uniformly dispersed within the polymer matrix, and have an average radius of 4.8±1.4 nm. The nanocomposite films are superparamagnetic at room temperature and ferrimagnetic at 5 K.

Pulsed laser ablation from oxide surfaces in hydrogen atmosphere is shown to be a powerful new method for deposition of high quality metal films. Specifically, the cases of ablation from CuO and α‐Fe2O3 are studied. By examining the effects of hydrogen pressure, laser energy density, and the substrate temperature on the nature of the deposited films, optimum parameters have been identified for realization of high quality films of metallic Cu and Fe.

We present the results of an investigation of the magnetic properties of A/sub 2/FeReOe (A=Ca, Sr, Ba). We have studied the magnetization, high-temperature susceptibility and the ferromagnetic resonance response. The Ba and Sr systems are conducting while the Ca material is an insulator. The ordering temperature of the Ca materials is highest (/spl sim/540 K) and decreases to 315 K for the Ba system. The high-temperature susceptibility suggests a large moment, and the Curie-Weiss temperature is very close to the ordering temperature, as expected for a simple ferromagnet, although the ferromagnetic moment is somewhat less than expected. The spin dynamics are rather peculiar: the ferromagnetic resonance results suggest a magnetically inhomogeneous material. We discuss these results in terms of cation disorder.

A commercial atomic force microscope/magnetic force microscope (MFM) was modified to cool magnetic samples down to around 100 K under a high vacuum while maintaining its routine imaging functionality. MFM images of a 120 nm thick La0.7Ca0.3MnO3 film on a LaAlO3 substrate at low temperature show the paramagnetic-to-ferromagnetic phase transition. Evolution of magnetic domains and magnetic ripples with decreasing temperature are also observed near the edge of a 20 nm thick patterned Co film on a Si substrate.

A prominent theme in inorganic materials research is the creation of uniformly flat thin films and heterostructures over large wafers, which can subsequently be lithographically processed into functional devices. This letter proposes an approach that will lead to thin film topographies that are directly counter to the above-mentioned philosophy. Recent years have witnessed considerable research activity in the area of self-assembly of materials, stimulated by observations of self-organized behavior in biological systems. We have fabricated uniform arrays of nonplanar surface features by a spontaneous assembly process involving the oxidation of simple metals, especially under constrained conditions on a variety of substrates, including glass and Si. In this letter we demonstrate the pervasiveness of this process through examples involving the oxidation of Pd, Cu, Fe, and In. The feature sizes can be controlled through the grain size and thickness of the starting metal thin film. Finally, we demonstrate how...

Microchannel is basic functional component of microfluidic chip and every step-forward of its construction technique has been receiving concern all over the world. The present work describes a novel, rapid and simple fabrication technique for building 3D microchannels in poly(dimethyl siloxane) (PDMS) elastomer. These microchannels were used for rapid detection of antigens (E. coli) by quantum dot (QD) based approach. Luminescent QD (CdTe) were synthesized by aqueous method and characterized using high resolution transmission electron microscopy (HRTEM), fluorescence spectroscopy and X-ray diffraction (XRD). The QDs were functionalized with anti-E. coli antibodies for immuno-detection. The reported process allowed easier and faster method of fabrication of circular 3D micochannels and demonstrated their potential use in an immuno-biosensor device.

We present here detailed transport, magnetic, structural and morphological studies on thin and ultra-thin films of superconducting YBa 2 Cu 3 O 7−δ (1-2-3) deposited on single crystalline substrates of LiNbO 3 . The films were deposited using the technique of excimer laser ablation and have been found to have their c -axis oriented perpendicular to the plane of the film. We report results for films of thickness 500 A, 1000 A, 1600 A and 6000 A. Superconducting transition temperatures ( T c ) have been studied by DC-resistivity, AC- and DC-magnetization. Critical current densities ( J c ) from transport measurements are found to be in excess of 10 5 A/cm 2 at 77 K. The temperature dependence of J c is also examined and the flux pinning energy is estimated within the flux creep picture. High field hysteresis loop studies are in agreement with the above results and yield meaningful indications of critical fields H c and irreversibility fields H r . A study of the evolution of film morphology with increase of film thickness is also reported and it reflects on the growth mechanism of 1-2-3 on LiNbO 3 .

The reactive aspect of pulsed laser induced vaporization has been explored via synthesis of tungsten carbide films from an unreacted sintered mixture of the W–C system. Using low-angle x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS), it is shown that stoichiometry and the extent of chemical compound formation in the deposited films depend upon the laser fluence. Two cases with energy density 20 J/cm2 and 40 J/cm2 are discussed and compared. An attempt has been made to illustrate the mechanism behind the reactive aspect of the deposition.

The effect of Ar+-ion implantation (energy 100 keV) has been studied on ferrocene pellets at 1×1014 and 5×1014 ions/cm2 doses. The characterization techniques used were infrared spectroscopy, small-angle X-ray diffraction and bulk X-ray diffraction. At the lower dose, formation of a metastable alkene occurred; at the higher dose a metastable alkane was formed. The X-ray data showed that metastable phases like Fe−C, (Fe−C)H and carbon phases were produced at the surface. Not being observable on the surface, the organic counterparts are expected to be volatile in nature. When treated with varying energy doses, ferrocene showed bulk damage; the IR spectra showed the loss of fine structure and only a single peak persisted, which was due to metal-ring vibration.

Stoichiometric films of cupric and cuprous oxide are deposited on Si, MgO, and Y‐ZrO2 substrates by pulsed excimer laser ablation technique. It is found that the equilibrium phase diagram based considerations dictate the phase formation. The films are characterized by small‐angle x‐ray diffraction, infrared, and UV‐visible spectroscopies and Rutherford backscattering spectroscopy. It is shown that epitaxy of Cu2O films can be realized on single crystal MgO (100) substrates and the corresponding film resistivity is of the order of 40–60 Ω cm.

Ion‐implantation induced structural transformations are investigated in hydrogenated microcrystalline silicon (μc‐Si:H). Ion‐beam processing of the μc‐Si:H samples was done using 160 keV Ar+ ions at different dose values, in the range of 1013–1016 ions/cm2. Ion‐beam induced transformation from the microcrystalline‐to‐amorphous phase was examined with the help of x‐ray diffraction (XRD) and laser‐Raman spectroscopic techniques. The conductivity changes in the samples were also monitored as a function of ion dose. It is observed that at a specific threshold ion dose value, the conductivity decreases by more than an order of magnitude. There are concomitant changes in XRD and laser Raman features. Furthermore the results clearly indicate grain growth under ion‐beam irradiation at high dose values.

The time-dependent relaxation of the remanent polarization in epitaxial lead zirconate titanate (PbZr0.2Ti0.8O3) ferroelectric thin films, containing a uniform two-dimensional grid of 90° domains (c axis in the plane of the film), is examined using piezoresponse microscopy. The 90° domain walls preferentially nucleate the 180° reverse domains during relaxation, with a significant directional anisotropy. Relaxation occurs through the nucleation and growth of reverse domains, which subsequently coalesce and consume the entire region as a function of time.

We report microwave absorption measurements as a function of temperature (from 290 to 125 K) and magnetic field (from 0 to 0.3 T) in mm-thick parallelepipeds of sintered $V_2O_3$ and $V_2O_3$ containing micron-size Fe precipitates. As before, it turns out that near the metal–insulator (MI) transition, the loss exhibits a sharp peak as a function of temperature. On application of a magnetic field, the peak temperature for ($V_2O_3$ + Fe) changes by a few kelvin, causing a giant magnetoimpedance ( \approx 200% in 0.1 T field) in the neighborhood of the MI transition.

The effects of YBa2Cu3O7−δ (YBCO) cap layers on the magnetic and electronic properties of La0.7Sr0.3MnO3 (LSMO) underlayers was determined by x-ray magnetic circular dichroism and x-ray absorption spectroscopy techniques. The YBCO caps alter the LSMO in a way that effectively decreases the concentration of La at the LSMO/YBCO interface.

We have done a systematic study of the ac susceptibility, dc magnetization, and ferromagnetic resonance in a set of polycrystalline samples of La1−xSrxMnO3 with nominal x values varying from 0.46 to 0.53 at 0.01 intervals. Apart from noting the remarkable changes attendant on small variations in x, it is found that at low T, one has coexistence of ferromagnetic and antiferromagnetic phases. The resonance data are interpreted to provide a measure for the size of the ferromagnetic regions.

Epitaxial films of La2/3Ca1/3MnO3 were successively implanted with 100 and 200 keV silver ions at fluences of 4.5×1015 and 1×1016 ions/cm2, respectively, to achieve a fairly uniform implant distribution. The as-implanted films are insulating and do not show a metal–insulator transition. Postimplantation annealing at 950 °C shows a recovery of the high structural quality of the films, along with an increase in the metal–insulator transition temperature (Tp), magnetoresistance, and the peak temperature coefficient of resistance (TCR) at the transition. The peak TCR of 23% for manganite films is clearly significant for bolometric applications.

Anisotropic growth of magnetite (Fe3O4) nanoparticles is achieved in a hydrothermal growth process using hexamine to play a dual role of oxide forming and directing agent. The samples are characterized by X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, squid magnetometry, ferromagnetic resonance technique, diffuse reflectance spectroscopy and Mössbauer spectroscopy, which collectively establish the formation of Fe3O4 phase. Anisotropic structures such as nanorods and nanotubules are revealed and these are shown to exhibit good humidity sensing properties.

In this paper we present some results on medium energy ion beam induced microstructural modifications in pulsed laser deposited tungsten carbide films and their effects on the microhardness of the material. Thin films of tungsten carbide were deposited by laser ablation from “WC” compound. These films were subsequently implanted with 80 keV N+2 ions at various dose levels. Variations in the microstructure and phase precipitation were studied by using low angle X-ray diffraction. Scanning electron microscopy was also used for characterization. After every stage of processing, the microhardness of the sample was monitored using Knoop's indentation technique. Ion beam induced recrystallization in as-deposited amorphous thin films, an increase in the microhardness of the film at an optimum ion dose of 3 × 1016 ions cm−2, and their correlation to structural and morphological features are the main interesting results of this study.

Superconducting thin films of Y 1 Ba 2 Cu 3 O 7− x were deposited onto YZrO 2 substrates by pulsed excimer ( λ = 248 nm) laser ablation. The deposited films were exposed to the aqueous medium for different durations of time ranging from 15 min to 42 h. The degradation of Y 1 Ba 2 Cu 3 O 7− x epitaxial films was studied by X-ray diffraction and measurements of the transition temperature T c . In a separate set of experiments, subsequent to deposition of superconducting films, thin layers (0.1-1μm) of polymer (polyacrylonitrile) were deposited onto the films without breaking vacuum. The sandwiches were subjected to the same aqueous treatment. It was observed that degradation effects were passified by the polymer overlayer.

An automated linear laboratory EXAFS spectrometer of the Johansson type has been indigenously developed. Only two translational motions are required to achieve the necessary Rowland circle configuration for the (fixed) X-ray source, the dispersing and focusing bent crystal and the receiving slit. With the available crystals the spectral region from 5 to 25 keV can be scanned. The linear motions of the crystal and receiving slit including the detector assembly are achieved by employing software-controlled DC motors and utilizing optical encoders for position sensing. The appropriate rotation of the crystal is achieved by the geometry of the instrument. There is a facility to place the sample alternately in the path of the X-ray beam and out of the path to record both the incident X-ray intensityI0 and the transmitted intensityI employing the scintillation detector. An arrangement with a two-window proportional detector before the sample to measureI0 and the scintillation detector to recordI is also developed; in this case it is not necessary to oscillate the sample. Fast electronic circuits are employed to minimize counting errors. The instrument is user-friendly and it is operated through a menu-driven IBM compatible PC. EXAFS spectra of high resolution have been recorded using the spectrometer and employing the Si(111) reflecting planes; the X-ray source being a Rigaku 12 kW rotating anode with Cu target. We describe the spectrometer and discuss its performance with a few representative spectra.

Ion beam and thermally induced interface reactions between high-Tc superconducting thin film of Y1Ba32Cu3O7−x (YBaCuO) and metal overlayer of Ag are studied with a view to improve the electrical properties of the interface. The interface reaction is induced by 100 keV Ar+ ion beam with a dose value ranging from 5 × 1013 to 2 × 1015ions/cm2. The electrical properties of the Ag/YBaCuO film interface, specifically contact resistance, have been investigated by the “three-probe vs four-probe” configuration.

High-Tc superconductor YBa2Cu3O7 was irradiated by thermal neutrons. Significant effects on the critical temperature were found. The changes were also investigated by X-ray diffraction technique.65Cu (n, γ)66Cu was the only reason for the degradation in superconducting properties. The existence of an isotope effect is argued.

An attempt was made to modify the surface of an austenitic stainless steel using laser surface melting (LSM) technique to improve the localized corrosion resistance. AISI type 316 stainless steel (SS) specimens in solution annealed, cold worked (5, 10, 15 and 20%) and sensitized (923 K, 20 h) conditions were laser surface melted using a pulsed ruby laser at the energy of 6 J per pulse. The melted layers were characterized by small angle X-ray diffraction (XRD), optical microscopy and scanning electron microscopy (SEM)

Sixteen patients, presenting with cerebrospinal fluid leak, were operated upon using the transorbital frontoethmoidectomy (TOFE) approach for closure of the leak. The most common etioIogy in our series was trauma (87%), with accidental trauma being the most frequent type. Metrizamide CT scanning was found to be very useful in identifying the presence and site of the leak. The fovea ethmoidalis and the cribriform plate were found to be the commonest sites of leak. The TOFE approach offered adequate exposure of the orbit and paranasal sinuses as well as good cosmesis, no postoperative anosmia and the use of the operating microscope to preserve vital structures.

Using x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) techniques, we have investigated the electronic structure and magnetic properties of La0.7Sr0.3MnO3 (LSMO) as a function of YBa2Cu3O7−δ (YBCO) cap layer thickness. The Mn L2,3 XAS and XMCD data clearly show that the magnetic properties and electronic structure of the LSMO are adversely affected by the YBCO overlayer caused by cation displacement/exchange that effectively reduces the concentration of the La atoms in the LSMO near the YBCO/LSMO interface.

Monte Carlo simulation studies are performed to examine the implications of octahedral cation (Fe, Mo) site disorder for magnetization in the double-perovskite Sr2FeMoO6. Correlations between the near-neighbor cation distributions and the spin distributions are identified to gain insight into the spin arrangement within, and on the periphery of a given transition element cation cluster. It is shown that the drop in the magnetic moment is nearly linear with the increase in the mis-site defect concentration for the case of randomly created defects. Implications of the concomitant presence of mis-site defects and oxygen vacancies are also analyzed.

Epitaxial thin films of ordered double-perovskite Sr2FeMoO6−y are deposited on (001) SrTiO3 substrates by pulsed-laser deposition using a two step growth process. Selection of growth conditions is found to lead to either highly conductive metallic thin films (residual resistivity of about 1 μΩ cm) or semiconducting films. The metallic films show a positive magnetoresistance (MR) as high as 35%, while the semiconducting films show a negative MR of −3%, at a temperature of 5 K and a field of 8 T.

Anomalously high metal–insulator transition temperature Tp and ferromagnetic transition temperature Tc have been observed in thin films of La0.8Ca0.2MnO3. Ferromagnetic resonance signals from microwave studies are observed at room temperature (well above Tc) suggesting the presence of multiple magnetic spin systems. The Tp and Tc values are higher than that of La0.67Ca0.33MnO3 which have the highest Tp and Tc according to the bulk phase diagram. These results suggest that properties well beyond those seen in the bulk phase diagram may be achievable in thin films of the manganites.

We report on the effects of using SrFe7Al5O19 as a buffer layer for growth of high-quality epitaxial barium-ferrite thin films on sapphire substrates. X-ray diffraction studies reveal that the buffer layer causes the interfacial strains in the barium-ferrite films to relax. As a result, the ferromagnetic resonance linewidth decreases even in the as-deposited case. However, the more striking result is the drastic reduction in the linewidth that occurs when the barium-ferrite film is deposited on the buffer layer and subsequently annealed at 1000 °C for 2 h, allowing the observation of a large number of spin-wave resonances (up to the 15th mode), indicating an improvement in both the surface and interface characteristics.

Random sequential adsorption of mixed convex plus concave contour (MC) objects exhibits some distinctly different peculiar characteristics than the cases of purely convex objects. Though the substrate coverage approaches the jamming limit with time t as t;{-p} , same as that for convex objects, the law p approximately 1d_{f} , valid for convex objects with d_{f} degrees of freedom, does not hold for MC objects. Interestingly, for a fixed number of degrees of freedom, the exponent p changes with the degree of nonconvexity and bears a near perfect correlation with the same.

Diamondlike hydrogenated amorphous carbon films have been deposited for the first time by pulsed ruby laser deposition (PLD) from pyrolytic graphite in hydrogen partial pressure. A hint in the IR absorption spectrum at 2920 cm−1 provides an evidence for the incorporation of hydrogen in the film. Raman scattering (RS) measurements display a large downward shift in the position of the intense G line to 1500 cm−1, whereas the relatively weak D line is observed near 1350 cm−1 along with a strong enhancement in RS near 1210 and 800 cm−1. These features are attributed to an increased proportion of tetrahedral (sp3) character in the amorphous carbon network due to formation of hydrogen‐related complexes. Additional support for this proposal is sought from the enhanced band gap of the PLD a‐C:H films compared to those of unhydrogenated PLD a‐C films.

Ion implantation effects have been studied in the pulsed-laser-deposited amorphous carbon (a-C) films having a diamond-like character. 80 keV Ar + ions were implanted at various doses, and the optical and electrical properties of the films were studied as a function of ion dose. It was observed that the electrical resistivity and optical band gap decrease as the ion dose increases. The transparency increases from 80% (for the as-deposited a-C) to over 97% in the wavelength range 2.5–4 microm for the sample implanted at 1 × 10 13 ions cm −2 and at higher doses it decreases. Raman measurements at higher doses show the loss of sp 3 hybridized carbon atoms with no sign of microcrystallinity. The absence of the Raman contribution at 600 and 1275 cm −1 in samples implanted at doses greater than 1 × 10 15 ions cm −2 corresponds to an implantation-induced sp 3 -to-sp 2 transformation without graphitization.

Interface reactions induced at the liquid-solid interface by a field-generated plasma are used to synthesize metastable forms of iron oxide, carbide and nitride. The resulting chemical and microstructural changes on the surface of iron are studied using conversion electron Mossbauer spectroscopy, while the information regarding the surface morphology is obtained through scanning electron microscopy.

The progress in the area of applications of ion implantation and laser treatment to III–V semiconductors is reviewed. The achievements till todate are discussed alongwith the yet unresolved problems.

Thin films of BaTiO3 and Ni x Fe3−x O4 have been obtained by pulsed ruby laser evaporation process. In the case of BaTiO3 a sintered bulk pellet was used as the vaporization source, while Fe50Ni50 metallic alloy was used as the source for synthesis of nickel ferrite. The dependence of the film properties on oxygen partial pressure and laser energy density during deposition has been investigated. It is shown that thin films of these materials having good structural, morphological and stoichiometric properties can be obtained by the laser process by appropriate control of process parameters.

Barium titanate is a well-known ferroelectric material (Tc ≈ 120°C) dominating the dielectric ceramics field for the last five decades and is very widely used in multi-layer capacitors. It is usually prepared via the classical solid state reaction between barium carbonate and titanium dioxide around 1100–1300°C. On the other hand, chemical routes with new precursors are being developed to improve its performance parameters. In the present work, butyl titanate monomer is hydrolyzed in presence of saturated solution of barium nitrate at room temperature resulting in reactive mixture of titania and barium nitrate. The mixture is dried around 100°C and subsequent calcination of these powders under controlled conditions (T ≈ 650°C) led to a high purity, homogeneous BaTiO3 powder. XRD, DTA/TG/DTG, IR and dielectric measurements were used to characterize the powder. A successful attempt is made to deposit thin films of BaTiO3 using pulsed ruby laser. The deposited films are characterized by various tech...