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Preliminary results on magnetic and transport properties of a thin film of disordered Fe2CrAl deposited on (111) Si by pulsed laser deposition is reported in this study. While the bulk arc melted ingot used as target for the deposition is purely ferromagnetic, the film shows the co-existence of different magnetic phases, which arises due to the granular nature of the film. This is because, although the average composition pertains to Fe2CrAl, local disorder results in the formation of grains with different magnetic states that may be ferromagnetic or may consist of magnetic clusters. The resulting magnetic inhomogeneity of the thin film leads to large values of negative temperature coefficient of resistance of ∼22%/K at 260 K. [ABSTRACT FROM AUTHOR]

Abstract: Random variation of band bowing in pulsed laser deposited Mg doped (x=0.090, 0.147, 0.211, 0.268) ZnO thin films was observed. The X-ray diffraction and ultraviolet–visible spectroscopy data reveal lattice relaxation and increase in band gap as well as disorderness in the samples. The X-ray photoelectron spectroscopy data confirm the presence of magnesium and oxygen interstitials (Mg i and O i ) as well as oxygen vacancies (V O ). The randomness of band bowing is attributed to the presence of these defects. [Copyright &y& Elsevier]

Abstract: We have studied rectifying properties of ZnO/p-Si and ZnO/Fe3O4/p-Si heterojunction grown by Pulsed Laser Deposition. It is observed that junction properties strongly depend on temperature. Our measurement shows that intermediate Fe3O4 layer has significant impact in modifying the transport properties in ZnO/Fe3O4/p-Si. In ZnO/p-Si thermionic emission is dominant mechanism for electrical transport across the junction. Whereas in ZnO/Fe3O4/p-Si thermionic emission model explains the non linear current voltage characteristics at room temperature, but below Verwey transition when intermediate Fe3O4 layer act as an insulator, electrical transport is governed by tunneling mechanism. [Copyright &y& Elsevier]

Abstract: Magnetite (Fe3O4) thin films are prepared by pulsed laser deposition using an α-Fe2O3 target on silicon (111) substrate in the substrate temperature range of 350 °C to 550 °C. X-ray diffraction (XRD) measurement shows that the film deposited at 450 °C is a single phase Fe3O4 film oriented along [111] direction. However, the film grown at 350 °C reveals mixed oxide phases (FeO and Fe3O4), while the film deposited at 550 °C is a polycrystalline Fe3O4. X-ray photoelectron spectroscopy study confirms the XRD findings. Raman measurements reveal identical spectra for all the films deposited at different substrate temperatures. We observe abrupt increase in the resistivity behavior of all the films around Verwey transition temperature (T V) (125 K–120 K) though the transition is broader in the film deposited at 350 °C. We observe that the optimized temperature for the growth of Fe3O4 film on Si is 450 °C. The electrical transport behavior follows Shklovskii and Efros variable range hopping type conduction mechanism below T V for the film deposited at 450 °C possibly due to the granular growth of the film. [Copyright &y& Elsevier]

We have studied the electronic and magnetic properties of SrRuO 3 thin films deposited by pulse laser deposition on SrTiO 3 (100) substrate. X-ray diffraction and reciprocal space mappings show the epitaxial nature of the thin films and the formation of different structural phase such as tetragonal and tetragonal + monoclinic phase with oxygen partial pressure. In magnetization versus temperature behaviour we observed the large variation in Curie temperature with oxygen partial pressure. These variations are attributed to the defect induced modification in the local structure comprising RuO 6 octahedra. [ABSTRACT FROM AUTHOR]

Zero field cooled spontaneous exchange bias (SEB) is observed in self-assembled nanocomposite thin films of La 0.7 Sr 0.3 MnO 3 (LSMO):NiO grown on single crystal line SrTiO 3 (001) substrate by pulsed laser deposition. SEB is displayed by the asymmetry in the hysteresis loop of the composite film along with the field cooled conventional exchange bias (CEB) effect. The training effect shows that exchange bias relaxation is disorder mediated. It is revealed from DC magnetization measurements that such nanocomposite film divulges spin glass like behaviour, arising due to competing ferromagnetic and antiferromagnetic interactions at the assorted interfaces of ferromagnetic LSMO and antiferromagnetic NiO. X-ray magnetic circular dichroism (XMCD) measurements discern that SEB is mainly originating due to ferromagnetic coupling of unstable interfacial antiferromagnetic spin due to NiO with the ferromagnetic LSMO at the disordered interface. These results of self-assembled thin films provide a useful input to realize and understand microscopic origin of SEB for device application. • Self-assembled nanocomposite thin films of La 0.7 Sr 0.3 MnO 3 (LSMO):NiO grown on SrTiO 3 (001). • Zero field cooled spontaneous exchange bias (SEB), field cooled conventional exchange bias (CEB). • The training effect shows that exchange bias relaxation is disorder mediated. • Magnetization measurements reveals the presence of interfacial disordered glass like behaviour. [ABSTRACT FROM AUTHOR]

The electronic structure of Pulsed Laser Deposited (PLD) ZnO, Zn 0.95 Fe 0.05 O (ZFO), Zn 0.98 Al 0.02 O (ZAO) and Zn 0.93 Fe 0.05 Al 0.02 O (ZFAO) films were investigated by Photoelectron spectroscopy and X-ray absorption spectroscopy. X-ray diffraction and ϕ-scan measurements show epitaxial c-directional growth of the films. Temperature dependent magnetization and M-H loop measurements show the presence of room temperature magnetic ordering in all the films. Fittings of Fe 2p XPS and Fe L 3,2 −edge XAS of ZFO and ZFAO films show the presence of Fe, in both, Fe +2 and Fe +3 states in tetrahedral symmetry. Valence band spectra in resonance mode show resonance photon energy at 56 eV showing the presence of Fe 2+ state (∼2 eV) near the Fermi level. A significant effect of Fe and Al doping on the spectral shape of O K-edge XAS was observed. Results of the Spectroscopic studies reveal that, ferromagnetism in the films is due to the contribution of oxygen deficiency which increases the number of charge carriers that take part in the exchange interaction. Al co-doping with Fe (in ZFAO) results in the enhancement of saturation magnetization by increase in the carrier-mediated ferromagnetic exchange interaction. [ABSTRACT FROM AUTHOR]

We have studied the structural, electronic and magnetic properties of pulsed laser deposited thin films of Ni 1− x Cr x Fe 2 O 4 ( x =0.02 and 0.05) on Si (111) and Si (100) substrates. The films reveal single phase, polycrystalline structure with larger grain size on Si (111) substrate than that on Si (100) substrate. Contrary to the expected inverse spinel structure, x-ray photoemission (XPS) studies reveal the mixed spinel structure. XPS results suggest that Ni and Fe ions exist in 2+ and 3+ states, respectively, and they exist in tetrahedral as well as octahedral sites. The deviation from the inverse spinel leads to modified magnetic properties. It is observed that saturation magnetization drastically drops compared to the expected saturation value for inverse spinel structure. Strain in the films and lattice distortion produced by the Cr doping also appear to influence the magnetic properties. [ABSTRACT FROM AUTHOR]

• Stoichiometric hexagonal Sr0.6Ba0.4MnO3 films are grown. • Raman spectroscopy indicates towards octahedral distortion due to strain. • Weak ferromagnetic behavior is observed at room temperature with high TC. • XMCD measurement confirms weak ferromagnetism at room temperature. • Orbital moment is unquenched and has significant contribution in magnetization. We have probed the effect of intrinsic strain on the structural and magnetic properties of magneto-electric hexagonal Sr 0.6 Ba 0.4 MnO 3 (SBMO) thin film grown by pulsed laser deposition on LaAlO 3 (1 1 0) substrate by varying oxygen partial pressure (OPP). While the grown films show hexagonal structure with varying OPP, transition from oriented to polycrystalline growth is observed with increase in OPP. Raman spectroscopy confirms the P 6 3 / mmc symmetry of grown films along with the indication of distortion of octahedral. Magnetization measurements reveal room temperature weak ferromagnetic behavior in the thin films, which is in contrast to antiferromagnetic nature of its bulk counterpart. X-ray magnetic circular dichroism measurement confirms weak ferromagnetic behavior with contribution from unquenched orbital magnetic moment. [ABSTRACT FROM AUTHOR]

Relationship between magnetism and structure of Cu-doped ZnO was investigated at macroscopic and microscopic levels. Thin Zn 1−x Cu x O films ( x = 0.02, 0.04, 0.07 and 0.10) were prepared by a pulsed laser deposition and characterized via superconducting quantum interference device (SQUID) magnetometry, high-resolution x-ray diffraction, and Cu K -edge and Zn K -edge x-ray absorption, x-ray linear dichroism and x-ray circular magnetic dichroism spectroscopy. Even though the samples exhibit room-temperature ferromagnetism with magnetization that increases with Cu concentration, we did not detect signatures of local magnetic moments associated with Cu atoms, as evidenced by the lack of any XMCD signal. The host ZnO wurtzite lattice is not significantly altered by the addition of Cu. At the same time, most of the Cu atoms are not incorporated into the wurtzite lattice but rather have a CuO-like coordination. These results indicate that ferromagnetism of the investigated Zn 1−x Cu x O films is not directly linked to the doping atoms but rather is due to some other changes which have been introduced to the host ZnO by the dopants. [ABSTRACT FROM AUTHOR]

Fe (4 at.%) doped europium (III) oxide thin film was deposited on silicon (1 0 0) substrate by pulsed laser deposition technique. Structural, spectral and magnetic properties were studied by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and magnetization measurements. XRD and Raman spectroscopy reveal that the grown film is single phased and belongs to the cubic structure of Eu 2 O 3 . XPS study of the Eu 1.92 Fe 0.08 O 3 film shows that Fe exists in Fe 3+ ionic state in the film. The film exhibits magnetic ordering at room temperature. [ABSTRACT FROM AUTHOR]

We have investigated TiO 2 films prepared by pulsed laser deposition method on Si(1 1 1) surface using X-ray diffraction (XRD), Raman Spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM) and ion beam sputtering techniques. Our XRD data along with Raman indicated that the deposited TiO 2 is in anatase phase. The binding energy position of Ti 2p also supports the anatase phase formation. AFM topography of as deposited film indicates the formation of non uniform TiO 2 growth with the formation of voids on Si(1 1 1) substrate. After sputtering with argon ion beam, surface erosion occurs and voids have disappeared. The Ti 2p core level of sputtered TiO 2 exhibits the formation of Ti 2 O 3 , TiO and pure Ti on the surface. High binding energy shoulder of O 1s peak becomes sharp after sputtering. Ti LMM Auger peaks become broader after sputtering but no shift in kinetic energy is observed. [ABSTRACT FROM AUTHOR]

Patterned nano crystalline ZnFe 2 O 4 thin film was fabricated on quartz substrate by pulse laser deposition. XRD and Raman spectroscopic techniques were employed for structural characterization of the film. Silencing of a small number of prominent ferrite XRD peaks in thin film signify mild textured film growth. The observed XRD peak position swing with respect to the target material in thin film indicates formation of lateral strain in opposite directions during film growth. The thin film XRD peak position shift with target material data as reference is explained by suggesting an appropriate film growth model. Designated ferrite Raman emission peaks originated from film surface authenticates the stoichiometric and structural stability of ferrite material. AFM images indicate specific pattern formation with nanogranular morphology. Magnetic property measurements of the thin film revealed enhanced properties which are explained on the basis of texture, lattice strain, and surface features that are originated from patterned thin film growth. [ABSTRACT FROM AUTHOR]

Abstract: Magnetic behavior of a few pulsed laser deposited soft ferromagnetic thin films of Ni–Fe–Mo alloys of different thickness on sapphire single crystals is interpreted on the basis of their structural characteristics. Highly textured thin films have high void density due to island-like growth. X-ray reflectivity (XRR) of the thin films indicate that instead of a uniform density there are effectively three layers with density gradient across the thickness, which is further supported by atomic force microscopy and cross-sectional scanning electron microscopy. Rutherford backscattering spectroscopy and energy dispersive spectrum measurements reveal that the composition in the films is not too far from that of the bulk target with a trend of enhanced Fe yield in the films. The structural disorder strongly affected the magnetic property of the films resulting in much higher values of the Curie temperature T C and coercive field H C than those of the bulk targets. Bifurcations of low-field zero-field-cooled and field-cooled magnetization reflect the disorder-induced anisotropy in the thin films. The spin wave stiffness constants D are higher than their bulk counterparts which are supportive of the enhanced Fe yield in the films. The saturation magnetization, M calculated from measurements in field transverse to the films strongly supports the thickness found from XRR. Finally, even the 10nm thin films have sizable M and H C and T C >300K, making them good candidates for magnetic applications. Overall, the magnetic behavior and the structural characteristics have reasonably complemented each other. [Copyright &y& Elsevier]

Abstract: Effect of oxygen partial pressure on the structural, transport and magnetic properties of BiFeO3 (BFO) films grown on n-type conducting SrNb0.002Ti0.998O3(SNTO) substrates has been investigated. Variation in oxygen partial pressure, during pulsed laser deposition (PLD), results in the modifications in the physical properties of the films. Rutherford Backscattering (RBS) measurement shows that, BFO/SNTO films grown at 100 and 300mT oxygen partial pressures, exhibit better polarization and magnetization. Tuning of electrical and magnetic properties with oxygen partial pressure has been discussed in the light of oxygen vacancies. Various charge transport mechanisms have been discussed to understand the leakage current mechanisms in BFO/SNTO films. [Copyright &y& Elsevier]

Abstract: We report the effect of 200MeV Ag15+ ion irradiation with fluence of ∼5×1011 ions/cm2 on the structure and surface morphology of thin film devices of La0.6Pr0.2Sr0.2MnO3 (named as LPSMO) (p)/SrNb0.2Ti0.8O3 (named as SNTO) (n) manganite grown by Pulsed Laser Deposition (PLD) technique. The n-type manganite layers studied were of thickness 50, 100 and 200nm. After ion irradiation, the structural studies revealed improved crystallinity in the LPSMO/SNTO devices with the thickness of 50 and 200nm. But the 100nm films showed the formation of regular tracks like feature in their surface morphology after irradiation. All the irradiated films show suppression of resistivity at all the temperatures but it was different rate in 100nm LPSMO films which may be attributed to the formation of linear track like defects. [Copyright &y& Elsevier]

Abstract: We report the results of studies on the rectifying behavior and tunneling conduction in ZnO(n)/La0.5Pr0.2Sr0.3MnO3(LPSMO)(p)/SrNb0.002Ti0.998O3 (SNTO)(n) thin film heterostructure comprising of two p–n junctions fabricated using the Pulsed Laser Deposition (PLD) technique. A structural study using XRD -scan depicts the single-crystalline nature and confirms the phase purity while the transport studies using measurements at various temperatures and fields reveal the rectifying behavior. The temperature and field dependent variation in the saturation voltage indicates that, the heterostructure exhibits negative magnetoresistance (MR) at low temperatures and positive MR at room temperature (RT) which can be understood on the basis of the interface effect at the junction. curves obtained at all temperatures and fields show noticeable hysteresis during the positive voltage sweeping which has been attributed to the presence of the various conduction phenomena through the junctions in the presently studied heterostructure. [Copyright &y& Elsevier]

Abstract: Nanocrystalline indium oxide (INO) films are deposited in a back ground oxygen pressure at 0.02mbar on quartz substrates at different substrate temperatures (T s) ranging from 300 to 573K using pulsed laser deposition technique. The films are characterized using GIXRD, XPS, AFM and UV–visible spectroscopy to study the effect of substrate temperature on the structural and optical properties of films. The XRD patterns suggest that the films deposited at room temperature are amorphous in nature and the crystalline nature of the films increases with increase in substrate temperature. Films prepared at T s ≥473K are polycrystalline in nature (cubic phase). Crystalline grain size calculation based on Debye Scherrer formula indicates that the particle size enhances with the increase in substrate temperature. Lattice constant of the films are calculated from the XRD data. XPS studies suggest that all the INO films consist of both crystalline and amorphous phases. XPS results show an increase in oxygen content with increase in substrate temperature and reveals that the films deposited at higher substrate temperatures exhibit better stoichiometry. The thickness measurements using interferometric techniques show that the film thickness decreases with increase in substrate temperature. Analysis of the optical transmittance data of the films shows a blue shift in the values of optical band gap energy for the films compared to that of the bulk material owing to the quantum confinement effect due to the presence of quantum dots in the films. Refractive index and porosity of the films are also investigated. Room temperature DC electrical measurements shows that the INO films investigated are having relatively high electrical resistivity in the range of 0.80–1.90Ωm. Low temperature electrical conductivity measurements in the temperature range of 50–300K for the film deposited at 300K give a linear Arrhenius plot suggesting thermally activated conduction. Surface morphology studies of the films using AFM reveal the formation of nanostructured indium oxide thin films. [Copyright &y& Elsevier]

• Band offset values of NiO/Si has been done by using X-ray photoelectron spectroscopy (XPS). • Energy band diagram is constructed by using the results obtained from XPS. • Optical properties of NiO/Si have been done by using Spectroscopic ellipsometry. • These findings will pave the way to design NiO/Si based optoelectronic devices. We report on the optical properties and the electronic structure of the p -NiO/ n -Si heterostructure system, established for optoelectronic applications in the UV spectral region. Pulsed laser deposition was used to deposit p- NiO onto n -Si to form the p -NiO/ n -Si heterojunction system. The optical constants (n, k) and the morphological properties were obtained by using a spectroscopic ellipsometry performed in the energy range of 1-5 eV, while the band-offset measurements of the p -NiO/ n -Si heterostructure were performed using X-ray photoelectron spectroscopy analysis. Our results show valence and conduction band offsets values between NiO and Si of about 0.34 ± 0.2 eV and 1.68 ± 0.2 eV, respectively. Valence and conduction band offset values assume that a type I band alignment is formed at the p -NiO/ n -Si interface, with the conduction band offset being higher than valence band offset. Based on these findings, an energy-band diagram of the heterojunction is constructed to predict the charge transport properties of the p -NiO/ n -Si system. We infer that photogenerated holes should experience a lower potential barrier for their transfer across the p -NiO/ n -Si interface than photoelectrons, which should experience a larger barrier. Our results pave the way towards the development of these p -NiO/ n -Si heterojunctions for UV detectors, solar cells, and self-biased device applications. [ABSTRACT FROM AUTHOR]

Abstract: Systematic studies of thin silicon carbide (SiC) films deposited on Si (100) substrates using pulsed laser deposition technique at room temperature, 370 °C and 480 °C are carried out. X-ray photoelectron spectroscopy showed the formation of SiC bonds in the films at these temperatures along with some graphitic carbon clusters. Fourier transform infrared analysis also confirmed the formation of SiC nanocrystallites in the films. Transmission electron microscopy and electron diffraction were used to study the structural properties of nanocrystallites formed in the films. Surface morphological analysis using atomic force microscopy revealed the growth of smooth films. [Copyright &y& Elsevier]

Abstract: We report on study of morphology, optical contrast and transport characteristics of La0.7Ba0.3MnO3 (LBMO) manganite thin films bilayered with SnO2 on Si (001) substrate, synthesized using pulsed laser deposition system. X-ray diffraction study reveals that both LBMO and SnO2 show polycrystalline growth over the substrate. Atomic force microscopy shows interesting pyramidal structures of LBMO of size ∼2μm×1μm×0.1μm. On the other hand, SnO2 grows in the form of close packed cylindrical clusters of ∼200nm radius. Near-field optical microscopy (NSOM) study using 532nm laser reveal that optical NSOM output intensity in LBMO is four times less than SnO2 signal. Transport characterizations show that this bilayer configuration exhibit non-linear current–voltage characteristics from 300 upto 50K. The nature becomes linear below this temperature. The results project the system as a promising candidate in non-conventional device category in the area of spintronics. [Copyright &y& Elsevier]

Abstract: Zn 0.965 Cd 0.035 O/ZnO bilayer film has been developed using pulsed laser deposition (PLD) technique. The film is characterized by X-ray diffraction (XRD), energy dispersion analysis by X-ray (EDAX), UV-Vis and Valence band spectra (VBS). The XRD pattern confirms the single phase crystalline nature of the deposited film. The UV-Vis spectra establish a reduction of band gap (≈340meV) in the ternary alloy film of Zn 0.965 Cd 0.035 O/ZnO. The VBS shows shift in the peak corresponding to nonbonding oxygen p states. We also obtained valence band offset of 191meV in the film showing the rise of valence band. The calculated conduction band offset is found to be −51meV which confirms the lowering of the conduction band in the ternary alloy film. [Copyright &y& Elsevier]

• Fabrication of Ca-doped BiFeO3 films using Pulsed Laser Deposition. • Improvement in the ferroelectric behavior of BiFeO3 films with Ca-doping. • Role of strong hybridization between Fe3d–O2p for the improvement in ferroelectric behavior. Effect of Ca – doping on electronic structure and ferroelectric properties have been studied on PLD grown Bi 1-x Ca x FeO 3 /SNTO (x = 0.05, 0.10, 0.20) films. The structural study confirms single crystalline (100) oriented epitaxial growth of the films. The observed improvement in the ferroelectric behavior with an increase in Ca – doping has been attributed to the strong hybridization between Fe3d–O2p and localization of Fe3de g and Bi6s-O2p orbitals understood using X-ray Absorption Spectroscopy measurements. Ferroelectric measurements performed on BCFO films show the finite value of intrinsic ferroelectric polarization, though the contributions from the non – ferroelectric components lead to unsaturated and leaky loop. The sub-bandgap transition observed in the absorption spectra indicates the presence of oxygen vacancy states which is one of the reasons for observed leakage in polarization measurements. [ABSTRACT FROM AUTHOR]