Room-temperature ferromagnetism in Sn1−xMnxO2 nanocrystalline thin films prepared by ultrasonic spray pyrolysis

Sn_1−xMn_xO₂ (x=0.01-0.05) thin films were synthesized on quartz substrate using an inexpensive ultrasonic spray pyrolysis technique. The influence of doping concentration and substrate temperature on structural and magnetic properties of Sn_1−xMn_xO₂ thin films was systematically investigated. X-ray diffraction (XRD) studies of these films reflect that the Mn³⁺ ions have substituted Sn⁴⁺ ions without changing the tetragonal rutile structure of pure SnO₂. A linear increase in c-axis lattice constant has been observed with corresponding increase in Mn concentration. No impurity phase was detected in XRD patterns even after doping 5 at% of Mn. A systematic change in magnetic behavior from ferromagnetic to paramagnetic was observed with increase in substrate temperature from 500 to 700 °C for Sn_1−xMn_xO₂ (x=0.01) films. Magnetic studies reveal room-temperature ferromagnetism (RTFM) with 3.61×10⁻⁴ emu saturation magnetization and 92 Oe coercivity in case of Sn_1−xMn_xO₂ (x=0.01) films deposited at 500 °C. However, paramagnetic behavior was observed for the films deposited at a higher substrate temperature of 700 °C. The presence of room-temperature ferromagnetism in these films was observed to have an intrinsic origin and could be obtained by controlling the substrate temperature and Mn doping concentration.     

Effect of oxidation temperature on microstructure, mechanical behaviors and surface morphology of nanocomposite Ti-Cx-Ny thin films

Two nanocomposite Ti-C_x-N_y thin films, TiC_0.95N_0.60 and TiC_2.35N_0.68, as well as one pure TiN, were deposited at 500 °C on Si(1 0 0) substrate by reactive unbalanced dc-magnetron sputtering. Oxidation experiments of these films were carried out in air at fixed temperatures in a regime of 250-600 °C with an interval of 50 °C. As-deposited and oxidized films were characterized and analyzed using X-ray diffraction (XRD), microindentation, Newton's ring methods and atomic force microscopy (AFM). It was found that the starting oxidation temperature of nanocomposite Ti-C_x-N_y thin films was 300 °C irrespective of the carbon content; however their oxidation rate strongly depended on their carbon content. Higher carbon content caused more serious oxidation. After oxidation, the film hardness value remained up to the starting oxidation temperature, followed by fast decrease with increasing heating temperature. The residual compressive stress did not show a similar trend with the hardness. Its value was first increased with increase of heating temperature, and got its maximum at the starting oxidation temperature. A decrease in residual stress was followed when heating temperature was further increased. The film surface roughness value was slightly increased with heating temperature till the starting oxidation temperature, a great decrease in surface roughness was followed with further increase of heating temperature.     

Annealing effect on the structural and optical properties of a Cd1−xZnxS thin film for photovoltaic applications

Herein is a report of a study on a Cd_1−xZn_xS thin film grown on an ITO substrate using a chemical bath deposition technique. The as-deposited films were annealed in air at 400 °C for 30 min. The composition, surface morphology and structural properties of the as-deposited and annealed Cd_1−xZn_xS thin films were studied using EDX, SEM and X-ray diffraction techniques. The annealed films have been observed to possess a crystalline nature with a hexagonal structure. The optical absorption spectra were recorded within the range of 350-800 nm. The band gap of the as-deposited thin films varied from 2.46 to 2.62 eV, whereas in the annealed film these varied from 2.42 to 2.59 eV. The decreased band gap of the films after annealing was due to the improved crystalline nature of the material.     

Effect of substrate temperature on the morphology, structural and optical properties of Zn1−xCoxO thin films

Zn_1−xCo_xO thin films with c-axis preferred orientation were deposited on sapphire (0 0 0 1) by pulsed laser deposition (PLD) technique at different substrate temperatures in an oxygen-deficient ambient. The effect of substrate temperature on the microstructure, morphology and the optical properties of the Zn_1−xCo_xO thin films was studied by means of X-ray diffraction (XRD), atomic force microscopy (AFM), UV-visible-NIR spectrophotometer, fluorescence spectrophotometer. The results showed that the crystallization of the films was promoted as substrate temperature rose. The structure of the samples was not distorted by the Co incorporating into ZnO lattice. The surface roughness of all samples decreased as substrate temperature increased. The Co concentration in the film was higher than in the target. Emission peak near band edge emission of ZnO from the PL spectra of the all samples was quenched because the dopant complexes acted as non-radiative centers. While three emission bands located at 409 nm (3.03 eV), 496 nm (2.5 eV) and 513 nm (2.4 eV) were, respectively, observed from the PL spectra of the four samples. The three emission bands were in relation to Zn interstitials, Zn vacancies and the complex of V_O and Zn_i (V_OZn_i). The quantity of the Zn interstitials maintained invariable basically, while the quantity of the V_OZn_i slightly decreased as substrate temperature increased.     

Synthesis and characterization of β-Ni(OH)2 up grown nanoflakes by SILAR method

In this paper we report a “bottom up” approach to synthesize β-Ni(OH)₂ nanoflakes using novel successive ionic layer adsorption and reaction (SILAR) method. Ni(OH)₂ thin films have been deposited on glass substrate using aqueous alkaline nickel chloride as nickel ion source and double distilled water maintained at 353 K temperature as hydroxyl ion source. The structural, surface morphological, optical and electrical properties of films are examined. The nanocrystallinity and β-phase of Ni(OH)₂ are confirmed by X-ray diffraction and FT-IR studies. Scanning electron microscope study revealed microporous and random distribution of well up grown interlocked nanoflakes. Optical absorption studies show wide optical band gap of 3.26 eV for β-Ni(OH)₂. The electrical properties revealed that β-Ni(OH)₂ has negative temperature coefficient of resistance with p-type semiconducting behaviour. The electrochemical property studied by cyclic voltametry in 2 M KOH electrolyte solution revealed pseudo capacitive behaviour, when β-Ni(OH)₂ thin film employed as working electrode in three electrode electrochemical cell with platinum as counter electrode and saturated calomel as reference electrode. The specific capacitance of 350 F g⁻¹ is obtained with nanoflake like morphology.     

Physico-chemical, optical and electrochemical properties of iron oxide thin films prepared by spray pyrolysis

Iron oxide thin films were prepared by spray pyrolysis technique onto glass substrates from iron chloride solution. They were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and (UV-vis) spectroscopy. The films deposited at T_s ≤ 450 °C were amorphous; while those produced at T_sub = 500 °C were polycrystalline α-Fe₂O₃ with a preferential orientation along the (1 0 4) direction. By observing scanning electron microscopy (SEM), it was seen that iron oxide films were relatively homogeneous uniform and had a good adherence to the glass substrates. The grain size was found (by RX) between 19 and 25 nm. The composition of these films was examined by X-ray photoelectron spectroscopy and electron probe microanalysis (EPMA). These films exhibited also a transmittance value about 80% in the visible and infrared range. The cyclic voltammetry study showed that the films of Fe₂O₃ deposited on ITO pre-coated glass substrates were capable of charge insertion/extraction when immersed in an electrolyte of propylene carbonate (PC) with 0.5 M LiCLO₄.     

Growth of cubic MgxZn1−xO alloy films by electron beam evaporation

We report the growth of cubic Mg_xZn_1−xO alloy thin films on quartz by electron beam evaporation. It can be found that all the samples have sharp absorption edges by the absorption measurements. X-ray diffraction measurements indicate the Mg_xZn_1−xO films are cubic phase with preferred orientation along the (1 1 1) direction. Energy dispersive spectrometry (EDS) demonstrates that the Mg concentration in Mg_xZn_1−xO films is much higher than the ceramic target used, and the composition can be tuned in a small scope by varying the substrate temperature and the beam electric current. The reasons of this phenomenon are also discussed.     

Photosensitization of nanocrystalline TiO2 film electrode with cadmium sulphoselenide

Nanocrystalline titanium dioxide (TiO₂) thin films composed of densely packed nanometer-sized grains have been successfully deposited onto an indium-doped-tin oxide (ITO) substrate. Then cadmium sulphoselenide (CdSSe) thin film was deposited onto pre-deposited TiO₂ to form a TiO₂/CdSSe film, at low temperature using a simple and inexpensive chemical method. The X-ray diffraction, selected area electron diffraction, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and water contact angle techniques were used for film characterization. Purely rutile phase of TiO₂ with super-hydrophilic and densely packed nanometer-sized spherical grains of approximate diameter 30-40 (±2) nm was observed. The increase in optical absorption was observed after CdSSe film deposition. Nest like surface morphology of CdSSe on TiO₂ surface results in air trapping in the crevices which prevents water from adhering to the film with increase in water contact angle. Photosensitization of TiO₂ with CdSSe was confirmed with light illumination intensity of 80 mW/cm².     

Growth of nanocrystalline CuIn3Se5 (OVC) thin films by ion exchange reactions at room temperature and their characterization as photo-absorbing layers

Nanocrystalline CuIn₃Se₅ thin films have been grown on ITO glass substrates using chemical ion exchange reactions with CdS, in alkaline medium at pH 11. The as-deposited films were annealed in air at 200 °C for 30 min and characterized using X-ray diffraction (XRD), transmission electron microscopy, energy dispersive X-ray analysis, X-ray photoelectron spectroscopy, and scanning electron microscopy to study the structural, compositional and morphological properties. The XRD patterns reveal the nanoparticles size to be of 18-20 nm diameter, while from the SEM images the nanoparticles size is estimated to be 20-30 nm. It is observed that the annealed films contain nanocrystallites connected with each other through grain boundaries, with grain size of about 100-125 nm and have an overall n-type electrical conductivity and higher photoconductivity. The current-voltage (I-V) characteristics (in dark and light) of these films indicated the formation of a Schottky like junction between the n-CuIn₃Se₅ (OVC) and CdS/ITO layers.     

High-throughput characterization of BixY3−xFe5O12 combinatorial thin films by magneto-optical imaging technique

Bi_xY_3−xFe₅O₁₂ thin films have been grown on GGG (Gd₃Ga₅O₁₂) (1 1 1) substrates by the combinatorial composition-spread techniques under substrate temperature (T_sub) ranging from 410 to 700 °C and O₂ pressure of 200 mTorr. In order to study the effect of substrates on the deposition of Bi_xY_3−xFe₅O₁₂ thin films, garnet substrates annealed at 1300 °C for 3 h were also used. Magneto-optical properties were characterized by our home-designed magneto-optical imaging system. From the maps of Faraday rotation angle θ_F, it was evident that the Faraday effect appears only when T_sub = 430-630 °C. θ_F reaches to the maximum value (∼6°/μm, λ = 632 nm) at 500 °C, and is proportional to the Bi contents. XRD and EPMA analyses showed that Bi ions are easier to substitute for Y sites and better crystallinity is obtained for annealed substrates than for commercial ones.     

Annealing effects on the structural and electrical transport properties of n-type Bi2Te2.7Se0.3 thin films deposited by flash evaporation

N-type Bi₂Te_2.7Se_0.3 thermoelectric thin films with thickness 800 nm have been deposited on glass substrates by flash evaporation method at 473 K. Annealing effects on the thermoelectric properties of Bi₂Te_2.7Se_0.3 thin films were examined in the temperature range 373-573 K. The structures, morphology and chemical composition of the thin films were characterized by X-ray diffraction, field emission scanning electron microscope and energy dispersive X-ray spectroscopy, respectively. Thermoelectric properties of the thin films have been evaluated by measurements of the electrical resistivity and Seebeck coefficient at 300 K. The Hall coefficients were measured at room temperature by the Van der Pauw method. The carrier concentration and mobility were calculated from the Hall coefficient. The films thickness of the annealed samples was measured by ellipsometer. When annealed at 473 K, the electrical resistivity and Seebeck coefficient are 2.7 mΩ cm and −180 μV/K, respectively. The maximum of thermoelectric power factor is enhanced to 12 μW/cm K².     

The optical properties of CdxZn1−xS thin films on glass substrate prepared by spray pyrolysis method

A series of Cd_xZn_1−xS thin films have been deposited on glass substrates using spray pyrolysis technique. The crystallinity and microstructure of Cd_xZn_1−xS thin films have been investigated by X-ray diffraction (XRD). Based on the results of Hall measurements, the films obtained were an n-type semiconductor. The X-ray data analysis of Cd_xZn_1−xS thin films showed that the grain size of the Cd_xZn_1−xS increased with increase in Cd composition. It is observed that the band gap increases as the Cd composition decreases. The results also showed a blue shift of absorption edge of optical transmission spectra is increases as Zn ratio increases. The effects of Cd composition on the structural and optical properties of Cd_xZn_1−xS thin films were related to their grain size, stress and carrier concentration.     

Influence of substrate temperature on structures and dielectric properties of pyrochlore Bi1.5Zn1.0Nb1.5O7 thin films prepared by pulsed laser deposition

The influence of substrate temperature on structural and dielectric properties of cubic pyrochlore Bi_1.5Zn_1.0Nb_1.5O₇ (BZN) thin films prepared by pulsed laser deposition process has been investigated. BZN thin films were deposited on Pt/Ti/SiO₂/Si(1 0 0) substrate and in situ annealed at 700 °C. The results indicate that the substrate temperature has a significant effect on the structural and dielectric properties of BZN thin films. The films exhibit a cubic pyrochlore structure in the substrate temperature range from 550 °C to 700 °C and at the annealing temperature of 700 °C. With further increase of substrate temperature to 750 °C, the phases of Bi₂O₃, BiNbO₄ and Bi₅Nb₃O₁₅ can be detected in the XRD pattern due to the Zn loss. The dielectric constant and loss tangent of the films deposited at 650 °C are 192 and 6 × 10⁻⁴ at 10 kHz, respectively. The tunability is 10% at a dc bias field of 0.9 MV/cm.     

Oxygen flux influence on the morphological, structural and optical properties of Zn1−xMgxO thin films grown by plasma-assisted molecular beam epitaxy

The Zn_1−xMg_xO thin films were grown on Al₂O₃ substrate with various O₂ flow rates by plasma-assisted molecular beam epitaxy (P-MBE). The growth conditions were optimized by the characterizations of morphology, structural and optical properties. The Mg content of the Zn_1−xMg_xO thin film increases monotonously with decreasing the oxygen flux. X-ray diffractometer (XRD) measurements show that all the thin films are preferred (0 0 2) orientated. By transmittance and absorption measurements, it was found that the band gap of the film decreases gradually with increasing oxygen flow rate. The surface morphology dependent on the oxygen flow rate was also studied by field emission scanning electron microscopy (FE-SEM). The surface roughness became significant with increasing oxygen flow rate, and the nanostructures were formed at the larger flow rate. The relationship between the morphology and the oxygen flow rate of Zn_1−xMg_xO films was discussed.     

Influence of deposition temperature on the structural and morphological properties of Be3N2 thin films grown by reactive laser ablation

Be₃N₂ thin films have been grown on Si(1 1 1) substrates using the pulsed laser deposition method at different substrate temperatures: room temperature (RT), 200 °C, 400 °C, 600 °C and 700 °C. Additionally, two samples were deposited at RT and were annealed after deposition in situ at 600 °C and 700 °C. In order to obtain the stoichiometry of the samples, they have been characterized in situ by X-ray photoelectron (XPS) and reflection electron energy loss spectroscopy (REELS). The influence of the substrate temperature on the morphological and structural properties of the films was investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD). The results show that all prepared films presented the Be₃N₂ stoichiometry. Formation of whiskers with diameters of 100-200 nm appears at the surface of the films prepared with a substrate temperature of 600 °C or 700 °C. However, the samples grown at RT and annealed at 600 °C or 700 °C do not show whiskers on the surface. The average root mean square (RMS) roughness and the average grain size of the samples grown with respect the substrate temperature is presented. The films grown with a substrate temperature between the room temperature to 400 °C, and the sample annealed in situ at 600 °C were amorphous; while the αBe₃N₂ phase was presented on the samples with a substrate temperature of 600 °C, 700 °C and that deposited with the substrate at RT and annealed in situ at 700 °C.     

Gas sensing properties of nanostructured MoO3 thin films prepared by spray pyrolysis

Thin films of molybdenum trioxide (MoO₃) were deposited on common glass using the chemical spray pyrolysis technique. A (NH₄)₆Mo₇O₂₄4H₂0 solution 0.1 M was used as the precursor one. The influence of substrate temperature on the crystallographic structure, surface morphology and electrical behavior of MoO₃ thin films was studied. MoO₃ can exist in two crystalline forms, the thermodynamically stable orthorhombic α-MoO₃ and the metastable monoclinic β-MoO₃ phase. XRD-spectra showed a growth of α-MoO₃ phase percentage as substrate temperature increases from 420 K up to 670 K. Films deposited in the 500–600 K range have a clearly porous surface structure of nanometer order as can be seen in SEM images. Changes up to six magnitude orders were observed in MoO₃ thin films electrical resistance when films temperature varied from 100 K up to 500 K. The sensing property of these MoO₃ films was also studied. The sensitivity was investigated in the temperature range 160 and 360 K for H₂O and CO gases, respectively. Both of them are of reducing nature. In all studied cases sensitivity decreases slowly as film temperature is raised. At room temperature the sensitivity changes from 12 up to 75% depending on substrate temperature. The sensitivity for CO gas was found to be lower than that of H₂O.     

Effect of UV lamp irradiation during oxidation of Zr/Pt/Si structure on electrical properties of Pt/ZrO2/Pt/Si structure

Metal-insulator-metal (MIM) capacitors were fabricated using ZrO₂ films and the effects of structural and native defects of the ZrO₂ films on the electrical and dielectric properties were investigated. For preparing ZrO₂ films, Zr films were deposited on Pt/Si substrates by ion beam deposition (IBD) system with/without substrate bias voltages and oxidized at 200 °C for 60 min under 0.1 MPa O₂ atmosphere with/without UV light irradiation (λ = 193 nm, Deep UV lamp). The ZrO₂(∼12 nm) films on Pt(∼100 nm)/Si were characterized by X-ray diffraction pattern (XRD), field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HRTEM), capacitance-voltage (C-V) and current-voltage (I-V) measurements were carried out on MIM structures. ZrO₂ films, fabricated by oxidizing the Zr film deposited with substrate bias voltage under UV light irradiation, show the highest capacitance (784 pF) and the lowest leakage current density. The active oxygen species formed by UV irradiation are considered to play an important role in the reduction of the leakage current density, because they can reduce the density of oxygen vacancies.     

Shallow hydroxyapatite coatings pulsed laser deposited onto Al2O3 substrates with controlled porosity: correlation of morphological characteristics with in vitro testing results

We studied the influence of porous Al₂O₃ substrates on Ce-stabilized ZrO₂-doped hydroxyapatite thin films morphology pulsed laser deposited on their top. The porosities of substrates were monitored by changing sintering temperatures and measured with a high pressure Hg porosimeter.The depositions were conducted in 50 Pa water vapors by multipulse ablation of the targets with an UV KrF* (λ = 248 nm, τ ∼ 25 ns) excimer laser. The surface morphology of synthesized nanostructures was investigated by scanning electron microscopy and atomic force microcopy. Ca/P ratio within the range 1.67-1.70 was found for hydroxyapatite coatings by energy dispersive spectroscopy.The films were further seeded with mesenchymal stem cells for in vitro tests. The cells showed good attachment and spreading uniformly covering the entire surface of samples. The complexity of film morphology which is increasing with substrate porosity was shown to have a positive influence on cultivated cells density.     

Effect of nitrogen content on phase configuration, nanostructure and mechanical behaviors in magnetron sputtered SiCxNy thin films

SiC_xN_y thin films with different nitrogen contents were deposited by way of incorporation of different amounts of nitrogen into SiC_0.70 using unbalanced reactive dc magnetron sputtering method. Their phase configurations, nanostructures and mechanical behaviors were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM) and microindentation methods. The result indicated SiC_0.70 and all SiC_xN_y thin films exhibited amorphous irrespective of the nitrogen content. The phase configuration and mechanical behaviors of SiC_xN_y thin films strongly depended on nitrogen content. SiC_0.70 exhibited a mixture consisting of SiC, Si and a small amount of C. Incorporated nitrogen, on one hand linked to Si, forming SiN_x, on the other hand produced CN_x and C at the expense of SiC. As a result, an amorphous mixture consisting of SiC, SiN_x, C and CN_x were produced. Such effects were enhanced with increase of nitrogen content. A low hardness of about 16.5 GPa was obtained at nitrogen-free SiC_0.70. Incorporation of nitrogen or increase of nitrogen content increased the film hardness. A microhardness maximum of ∼29 GPa was obtained at a nitrogen content of 15.7 at.%. This value was decreased with further increase of N content, and finally a hardness value of ∼22 GPa was obtained at a N content of ∼25 at.%. The residual compressive stress was consistent with the hardness in the nitrogen content range of 8.6-25.3 at.%.     

Formation of highly textured (1 1 1) Bi2O3 films by anodization of electrodeposited bismuth films

Highly textured bismuth oxide (Bi₂O₃) thin films have been prepared using anodic oxidation of electrodeposited bismuth films onto stainless steel substrates. The Bi₂O₃ films were uniform and adherent to substrate. The Bi₂O₃ films were characterized for their structural and electrical properties by means of X-ray diffraction (XRD), electrical resistivity and dielectric measurement techniques. The X-ray diffraction pattern showed that Bi₂O₃ films are highly textured along (1 1 1) plane. The room temperature electrical resistivity of the Bi₂O₃ films was 10⁵ Ω cm. Dielectric measurement revealed normal oxide behavior with frequency.