Magneto-optics based current imaging technique compares the nature of topological current distribution in a single crystal and thin film of topological insulator material, Bi2Se3. The single crystal, at low temperatures, has uniform topological surface current sheets which are about 3.6 nm thick. With increasing temperature, the current partially diverts into the crystal bulk and concomitantly, the sheet break up into a patchy network of high and low current density regions. The temperature dependence of the high current density areas shows that the surface to bulk transformation in the crystal has features of classical phase transition phenomena. The surface area fraction with topological high current density behaves like an order parameter. This phase transition is driven by disorder. In Bi2Se3 thin film we show the presence of quasi one-dimensional topological edge currents which are suppressed with a weak applied magnetic field. The edge current transforms into a uniform bulk current in the film.
The magnetic domain structure of the multiferroic Bi1-xDyxFeO3 (BDFO) deposited on ZnO at the macroscopic level has been demonstrated in this paper. Magnetic properties are observed by saturated magnetic and ferroelectric hysteresis loops at room temperature. The coupling behaviour and magnetic transition are verified using Multimode Atomic Force Microscope by applying bias between sample and MFM tip. ZnO thin film of 300 nm was deposited by dielectric sputtering using a ZnO target on Si p-type conducting (.0001-0005 Ω cm) substrate. BDFO thin films of 300 nm were deposited on Si/ZnO using PLD…
Sol-gel spin coating technique was employed to synthesize CuO thin films at 1500 rpm, 2200 rpm and 2400 rpm for 30 seconds, and subsequently annealed at 150-550°C for 1 hour. Multi-layered CuO thin films with 3 and 5 layers were prepared. These thin films were characterized using XRD, FTIR and polarizing light microscopy. The XRD and FTIR analysis confirmed the crystallization of CuO phase in thin films annealed above 350 °C, and corresponding crystallite sizes were observed to be increasing with the annealing temperature. The Scherrer formula was applied for (111) and peaks of XRD patterns of…
We report on the observation of metallic behavior in thin films of oxygen-deficient SrTiO$_3$ - down to 9 unit cells - when coherently strained on (001) SrTiO$_3$ or DyScO$_3$-buffered (001) SrTiO$_3$ substrates. These films have carrier concentrations of up to 2$\times10^{22}$ cm$^{-3}$ and mobilities of up to 19,000 cm$^2$/V-s at 2 K. There exists a non-conducting layer in our SrTiO$_{3-δ}$ films that is larger in films with lower carrier concentrations. This non-conducting layer can be attributed to a surface depletion layer due to a Fermi level pinning potential. The depletion width, trans…
The electrical conductance of molecular beam epitaxial Bi on BaF2(111) was measured as a function of both film thickness (4-540 nm) and temperature (5-300 K). Unlike bulk Bi as a prototype semimetal, the Bi thin films up to 90 nm are found to be insulating in the interiors but metallic on the surfaces. This result has not only resolved unambiguously the long controversy about the existence of semimetal-semiconductor transition in Bi thin film but also provided a straightforward interpretation for the long-puzzled temperature dependence of the resistivity of Bi thin films, which in turn might s…
Mn doped GaAs thin films were grown using molecular beam epitaxy at high and low substrate temperatures. The elemental concentration depth profiles in the thin films were determined by using Auger electron spectroscopy combined with ion etching. The Mn concentration is higher near the surface and then decreases with depth for films grown at high substrate temperatures. The Mn concentration profile is much more uniform when films are grown using a low substrate temperature. What was unexpectedly found are high levels of oxygen in the low substrate temperature grown thin films.
We report pulsed laser deposition synthesis and characterization of polycrystalline Fe1-xCox Si thin films on Si (111). X-ray diffraction, transmission electron, and atomic force microscopies reveal films to be dense, very smooth, and single phase with a cubic B20 crystal structure. Ferromagnetism with significant magnetic hysteresis is found for all films including nominally pure FeSi films in contrast to the very weak paramagnetism of bulk FeSi. For Fe1-xCoxSi this signifies a change from helimagnetism in bulk, to ferromagnetism in thin films. These ferromagnetic thin films are promising as …
Bulk Bi2Te3 is known to be a topological insulator. We investigate surface states of Bi2Te3(111) thin films using density-functional theory including spin-orbit coupling. We construct a method to unambiguously identify surface states of thin film topological insulators. Applying this method for one to six quintuple layers of Bi2Te3, we find that the topological nature of the surface states remains robust with the film thickness and that the films of three or more quintuple layers have topologically non-trivial or protected surface states, in agreement with recent experiments.
We report the magnetic properties of yttrium iron garnet (YIG) thin films grown by pulsed laser deposition technique. The films were deposited on Si (100) substrates in the range of 15-50 nm thickness. Magnetic characterizations were investigated by ferromagnetic resonance spectra. Perpendicular magnetic easy axis was achieved up to 50 nm thickness. We observed that the perpendicular anisotropy values decreased by increasing the film thickness. The origin of the perpendicular magnetic anisotropy (PMA) was attributed to the texture and the lattice distortion in the YIG thin films. We anticipate…
A slanted cobalt sculptured columnar thin film was fabricated using glancing angle deposition, and coated subsequently with graphene using a low temperature chemical vapor deposition process. The graphene deposition process preserves shape and geometry of the sculptured thin film, which was confirmed by scanning electron microscopy. According to the Raman spectroscopy results, the graphene coating is two to three monolayers thick and has a high defect concentration. The graphene coverage within the sculptured thin film is determined from generalized spectroscopic ellipsometry using a generaliz…
In this work, we studied amorphous carbon ($a$-C) thin films deposited using direct current (dc) and high power impulse magnetron sputtering (HiPIMS) techniques. The microstructure and electronic properties reveal subtle differences in $a$-C thin films deposited by two techniques. While, films deposited with dcMS have a smooth texture typically found in $a$-C thin films, those deposited with HiPIMS consist of dense hillocks surrounded by a porous microstructure. The density of $a$-C thin films is a decisive parameter to judge their quality. Often, x-ray reflectivity (XRR) has been used to meas…
Different thicknesses of cobalt thin films were growth by magnetron sputtering deposition techniques. The films thicknesses were determinated with X ray Photoelectron Spectroscopy (XPS) and Quartz Crystal Monitoring (QCM). XPS is also used to determinate the films quality. The films magnetic properties were determinated by Ferromagnetic Resonance (FMR) technique.
We report on the synthesis of perovskite SrIrO3 thin films using sputtering technique. Single phase (110) oriented SrIrO$_3$ thin films were epitaxially grown on SrTiO3 (001) substrate. Using off-axis XRD $θ-2θ$ scans, we demonstrate that these films exhibit (110) out-of-plane orientation with (001) and (1-10) lying in-plane. The sputtering grown thin films have a smooth, homogeneous surface, and excellent coherent interface with the substrate.
Magnetron sputtering has also been used to deposit thin films of some materials and it has significant technological importance. A modeling on deposition of epitaxial thin films of Yttrium Stabilized Zirconia (YSZ) was done the diffusion of adatom on the surface were studies. There exists a strong interaction of ions formed in the plasma during the sputtering process. Cu thin films were deposited on Si. Nanocomposite thin film of SiCN showed dendritic growth.
Thin film quasicrystal coatings have unique properties such as very high electrical and thermal resistivity and very low surface energy. A nano quasicrystalline thin film of icosahedral Al-Ga-Pd-Mn alloy, has produced by flash evaporation followed by annealing. Attempts will be made to discuss the micromechanisms for the formation of quasicrystalline thin film in Al-Ga-Pd-Mn alloys
In this paper we investigate the influence of the substrate material and film thickness on the Peierls transition temperature in tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) thin films, grown by physical vapor deposition. Our analysis shows that the substrate material and the growth conditions strongly influence the film morphology. In particular, we demonstrate that the Peierls transition temperature in thin films is lower than in TTF-TCNQ single crystals. We argue that this effect arises due to defects, which emerge in TTF-TCNQ thin films during the growth process.
We demonstrate high performance chemical bath deposited CdS thin-film transistors TFTs using atomic layer deposited ZrO2 based high-k gate dielectric material.
Ba7Ir3O13+δ in thin film form is discovered. These films are characterized by colossal permittivity (CP) ~104 at room temperature, attributable to the colossal internal barrier layer capacitance effect at atomically thin domain boundaries. These findings suggest a new route to seeking novel CP materials through designing atomically thin domain boundaries.
Varying the substrate temperature changes structural and magnetic properties of spinel ferrite NZFO thin films. XRD of films grown at different temperature display only 004 reflections, without any secondary peaks, showing growth orientation along the c axis. We find an increase in crystalline quality of these thin films with the rise of substrate temperature. The surface topography of the thin films grown on various growth temperatures conditions reveal that these films are smooth with low roughness, however the thin films grown at 800 C exhibit lowest average and rms roughness among all thin…
Tin Sulphide (SnS) thin films have been recognized as a potential candidate for solar cells. Many fabrication techniques have been used to grow SnS thin films. The band-gap, ${\rm E_g}$ of SnS films as reported in literature, were found to vary from 1.2-2.5 eV depending on the film fabrication technique. The present work reports the structural, compositional, morphological and optical characterization of SnS thin films fabricated by thermal evaporation at room temperature. Results show that for the given fabrication technique/ condition, the band-gap functionally depends on the lattice paramet…
We have synthesized epitaxial Ba2IrO4 (BIO) thin-films on SrTiO3 (001) substrates by pulsed laser deposition and studied their electronic structure by dc-transport and optical spectroscopic experiments. We have observed that BIO thin-films are insulating but close to the metalinsulator transition boundary with significantly smaller transport and optical gap energies than its sister compound, Sr2IrO4. Moreover, BIO thin-films have both an enhanced electronic bandwidth and electronic-correlation energy. Our results suggest that BIO thin-films have great potential for realizing the interesting ph…
BiFeO3 thin films have been deposited on Pt/sapphire and Pt/Ti/SiO2/Si substrates with pulsed laser deposition using the same growth conditions, respectively. Au was sputtered as the top electrode. The microscopic structure of the thin film varies by changing the underlying substrate. Thin films on Pt/sapphire are not resistively switchable due to the formation of Schottky contacts at both the top and the bottom interface. However, thin films on Pt/Ti/SiO2/Si exhibit an obvious resistive switching behavior under forward bias. The conduction mechanisms in BiFeO3 thin films on Pt/sapphire and Pt…
This paper discusses questions of synthesizing and pressing vanadium oxides to create film-forming materials that can be used in producing optical coatings. Based on the film-forming materials thus created, technological processes have been developed for fabricating coatings from vanadium dioxide by two methods of producing thin films: vacuum evaporation and magnetron sputtering. Questions of using films made from vanadium oxide in optical instrumentation are considered.
Far-infrared and terahertz spectroscopy of ferroelectric soft and central modes in thin films on substrates is reviewed. In addition to classical displacive proper ferroelectrics, also incipient and relaxor ferroelectrics and multiferroics are discussed. Special attention is paid to differences between the soft-mode behavior in thin films and bulk materials (ceramics and single crystals) and their influence on the low-frequency permittivity. Particularly the effects of the thin film strains and depolarizing electric fields of the probing waves on the grain boundaries are emphasized. The soft-m…
Ferroelectric materials with up-conversion luminescence (UCL) properties have potential opto-electric applications for display and sensing etc. Here, we demonstrate strong green UCL and enhanced electrical properties in Er3+-doped Na0.5Bi0.5TiO3 thin films. The thin films are prepared via using a modified chemical solution deposition method. These thin films are phase-pure and crystallized in perovskite structure. The largest remnant polarization (Pr) and highest dielectric constant are obtained from Na0.5Bi0.49Er0.01TiO3 thin films, and their values are 0.22 C/m2 and 1166, respectively. Meanw…
The temperature coefficients of the resistivity (TCR) of Cu, Ru, Co, Ir, and W thin films have been investigated as a function of film thickness below 10 nm. Ru, Co, and Ir show bulk-like TCR values that are rather independent of the thickness whereas the TCR of Cu increases strongly with decreasing thickness. Thin W films show negative TCR values, which can be linked to high disorder. The results are qualitatively consistent with a temperature-dependent semiclassical thin film resistivity model that takes into account phonon, surface, and grain boundary scattering.
Co and CoO thin films were deposited by magnetron sputtering in the form of multilayers. They were irradiated with Ar and Si ion beams of different energies and fluences. The magnetic properties were investigated.
A closed-form model is developed to evaluate the band-edge shift caused by quantum confinement for a two-dimensional non-parabolic carrier-pocket. Based on this model, the symmetries and the band-shifts of different carrier-pockets are evaluated for BiSb thin films that are grown along different crystalline axes. The phase diagrams for the BiSb thin film systems with different growth orientations are calculated and analyzed.
Here we report the adsorption behaviour of a water soluble laser dye rhodamine onto ultrathin films prepared by LB technique without altering its photophysical behabiour.
Surface-patterned ZnO thin films were fabricated by direct imprinting on ZnO sol and subsequent annealing process. The polymer-based ZnO sols were deposited on various substrates for the nanoimprint lithography and converted to surface-patterned ZnO gel films during the thermal curing nanoimprint process. Finally, crystalline ZnO films were obtained by subsequent annealing of the patterned ZnO gel films. The optical characterization indicates that the surface patterning of ZnO thin films can lead to an enhanced transmittance. Large-scale ZnO thin films with different patterns can be fabricated…
We report a scalable approach to synthesize a large-area (up to 4 mm) thin black phosphorus (BP) film on a flexible substrate. We first deposited a red phosphorus (RP) thin-film on a flexible polyester substrate, followed by its conversion to BP in a high-pressure multi-anvil cell at room temperature. Raman spectroscopy and transmission electron microscopy measurements confirmed the formation of a nano-crystalline BP thin-film with a thickness of around 40 nm. Optical characterization indicates a bandgap of around 0.28 eV in the converted BP, similar to the bandgap measured in exfoliated thin-…
The current practice of angular (Lorentz, Polarization and absorption (LPA)) corrections in bulk materials for higher angle broad peaks, due to the Kα doublet, are based on the results of Pike (Acta Cryst., 12 (1959) 87-92) and Ladell (Acta Cryst. 14 (1961) 47-53). These results are extended to thin film x-ray diffraction. The current practice in thin film studies of using the absorption factors for monochromatic radiation in LPA corrections is incorrect in both symmetric and grazing incidence x-ray diffraction. The correct expressions for absorption corrections are developed. In addition, a n…
Thin-film based phase plates are meanwhile a widespread tool to enhance the contrast of weak-phase objects in transmission electron microscopy (TEM). The thin film usually consists of amorphous carbon, which suffers from quick degeneration under the intense electron-beam illumination. Recent investigations have focused on the search for alternative materials with an improved material stability. This work presents thin-film based phase plates fabricated from metallic glass alloys, which are characterized by a high electrical conductivity and an amorphous structure. Thin films of the zirconium-b…
In the present investigation resistivity Vs temperature measurements have been performed for solgel prepared pure and Ni doped CdO (NDO) thin films. The semiconducting behavior i.e. negative temperature coefficient of resistivity (TCR) of pure CdO thin film through-out the whole temperature range can be attributed mainly due to concentration dependent thermally activation mechanism of the carriers. The semiconductor to metal transition (SMT) for NDO thin films has been elucidated via combined effect of involved grain boundaries, ionic impurities, phonon scattering and carrier activation.
Epitaxial copper thin films were deposited by magnetron sputtering. The adatoms during deposition are influenced by deposition parameters which cause variations in thin film properties. XRD and FESEM studies were done to get an insight into the growth mechanisms of the films. A modeling has been done on the epitaxial thin film growth with sputtering process. The parameters during sputtering like, sputtering yield, pressure, temperature, current density, deposition time were related and an attempt has been made to analyze the sputtering process.
The electronic band structures of Bi${}_{1-x}$Sb${}_{x}$ thin films can be varied as a function of temperature, pressure, stoichiometry, film thickness and growth orientation. We here show how different anisotropic single-Dirac-cones can be constructed in a Bi${}_{1-x}$Sb${}_{x}$ thin film for different applications or research purposes. For predicting anisotropic single-Dirac-cones, we have developed an iterative-two-dimensional-two-band model to get a consistent inverse-effective-mass-tensor and band-gap, which can be used in a general two-dimensional system that has a non-parabolic dispersi…
Poly- and single-crystal thin films of U-Mo alloys have been grown both on glass and sapphire substrates by UHV magnetron sputtering. X-ray and Electron Backscatter Diffraction data indicate that for single-crystal U1-xMox alloys, the pure cubic uranium gamma-phase exists for x > 0.22 (10 wt.% Mo). Below 10 wt.% Mo concentration, the resulting thin film alloys exhibited a mixed alpha-gamma uranium phase composition.
An environmentally stable mesoscopic thin film of Au of certain thickness has been deposited thermally on top of a Ag+ implanted oxide substrate to develop a close to room temperature superconductor. This thin film has been deposited in two different stages. Initially, a sol-gel derived ion conducting metal oxide (ICMO) thin film has been deposited by spin coating. Afterward, Ag+ has been introduced inside ICMO thin film by a chemical method. Following this, a thin layer of Au has been deposited on top of that Ag ion-implanted oxide via thermal evaporation. The temperature dependent resistivit…
The effects of annealing and variation of temperature on the electrical and thermoelectric properties of e-beam evaporated InSe thin films has been investigated in details. The XRD study demonstrates that the as-deposited InSe thin films are amorphous while they become polycrystalline with the presence of In3Se4 phase after annealing. The SEM micrographs reveal that the surfaces of as-deposited films are smooth whereas they become non-uniform due to annealing. The heating and cooling cycles of the as-deposited films exhibit that the resistivity of the films shows an irreversible phase-transiti…
We present and apply a new method to measure directly weak magnetization in thin films. The polarization of a neutron beam channeling through a thin film structure is measured after exiting the structure edge as a microbeam. We have applied the method to a tri-layer thin film structure acting as a planar waveguide for polarized neutrons. The middle guiding layer is a rare earth based ferrimagnetic material TbCo5 with a low magnetization of about 20 mT. We demonstrate that the channeling method is more sensitive than the specular neutron reflection method.
Copper ferrite thin films were rf sputtered at a power of 50W. The as deposited films were annealed in air at 800°C and slow cooled. The transmission electron microscope (TEM) studies were carried out on as deposited as well as on slow cooled film. Significantly larger defect concentration, including stacking faults, was observed in 50W as deposited films than the films deposited at a higher rf power of 200W. The film annealed at 800°C and then slow cooled showed an unusual grain growth upto 180nm for a film thickness of ~240nm. These grains showed Kikuchi pattern.
Neodymium is a remarkable active component in numerous magnetic alloys that are used in various applications. However, the application of bare neodymium thin film is limited due to the lack of information about its electrical and magnetic properties. We report synergistic study of Nd thin film using experimental and theoretical techniques of polarized neutron reflectometry, magnetoresistance measurement and density functional theory. Unlike bulk Nd, thin film specimen is a very poor electrical conductor. Also, as grown thin film on silicon substrate does not exhibit any magnetism in zero field…
To engineer strain relaxation of sputtered BST thin films on Pt-Si wafers, homo-buffer layer method was applied to eliminate Pt hillock formation. Thin BST homo-buffer layers were deposited at room temperature and subsequently the main BST layer was deposited at 650°C, Pt hillock free BST films were obtained with homo-buffer thickness above 5 nm. Relatively good electrical properties were obtained for BST thin films with 15 and 25 nm homo-buffer layer (T= 30 % at 5V and tan δ= 0.018).
