Search

Perovskite multiferroics have drawn significant attention in the development of next-generation multifunctional electronic devices. However, the majority of existing multiferroics exhibit ferroelectric and ferromagnetic orderings only at low temperatures. Although interface engineering in complex oxide thin films has triggered many exotic room-temperature functionalities, the desired coupling of charge, spin, orbital and lattice degrees of freedom often imposes stringent requirements on deposition conditions, layer thickness and crystal orientation, greatly hindering their cost-effective large-scale applications. Herein, we report an interface-driven multiferroicity in low-cost and environmentally friendly bulk polycrystalline material, namely cubic BaTiO

Плівки Cd1 – xMnxS (x = 0,0; 0,2; 0,4; 0,6; 0,8 та 1,0) були виготовлені за допомогою недорогої техніки хімічного осадження з ванни (CBD) на скляну підкладку. Плівки були отримані при оптимізованій температурі ванни 80 °C і pH 11. У поточному дослідженні ми вивчали структурні, оптичні та магнітні властивості осаджених тонких плівок. Рентгенівська дифракція (XRD) підтвердила, що нанокристалічна структура має більшу величину с/а порівняно з плівками CdMnS. XRD свідчить про гексагональні та кубічні структури вюрциту з орієнтацією росту вздовж напряму (002). Параметр решітки а зменшився з 4,126 до 4,003 Å. Спостерігалася та сама тенденція і для параметру решітки с з величиною x від 5,263 до 5,200 Å. Оптичні властивості осаджених нанокристалічних плівок Cd1 – xMnxS досліджували при кімнатній температурі за допомогою УФ-видимого спектрофотометра. Виявлено, що оптична заборонена зона збільшується з додаванням Mn2+. Розбавлені магнітні напівпровідники (DMS) II-VI груп демонструють чіткі магнітні фази при низьких і кімнатних температурах. Дослідження магнітної поведінки та сприйнятливості проводили за допомогою надпровідного квантового інтерференційного пристрою (SQUID) на магнітометрі з вібруючим зразком (VSM) в діапазоні постійного магнітного поля 0-40 кЕ при кімнатній температурі. Cd1 – xMnxS (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) films were prepared using a low-cost chemical bath deposition (CBD) technique onto the glass substrate. Films were obtained at an optimized bath temperature of 80 °C and pH of 11. In the current study, we investigated the structural, optical, and magnetic properties of the as-deposited thin films. The X-ray diffraction (XRD) result confirmed that the nanocrystalline structure has a high aspect ratio compared to CdMnS films. XRD suggests hexagonal wurtzite and cubic structures with growth orientation along the (002) direction. The lattice parameter ‘a’ decreased from 4.126 to 4.003 Å. The same trend in the lattice parameter ‘c’ with x was observed (5.263 to 5.200 Å). The optical properties of as-deposited Cd1 – xMnxS nanocrystalline films were studied at room temperature using a UV-visible spectrophotometer. The optical band gap is found to be enhanced with Mn2+ composition. Group II-VI-based diluted magnetic semiconductors (DMS) show distinct magnetic phases at low and room temperatures. The magnetic behavior and susceptibility studies were carried out using a superconducting quantum interference device (SQUID) on a vibrating sample magnetometer (VSM) in the range of dc magnetic field of 0-40 kOe at room temperature.

( x )BaTiO 3 –(1− x )Co 0.7 Fe 2.3 O 4 (BTO-CFO) magnetoelectric nanocomposite ceramic with x = 0.0, 0.25, 0.50, 0.75, 1.00 were successfully designed and fabricated by sol-gel route. The structural, micro structural, dielectric, ferromagnetic, ferroelectric and magnetoelectric properties of these composites were investigated. The coexistence of tetragonal phase and cubic spinel phase, without any secondary phase in composites is confirmed by the X-ray diffraction measurement. The field emission scanning electron micrograph show well distributed ferrite and ferromagnetic phases in the composites. The energy dispersive X-ray results revealed the purity and stoichiometry of BTO-CFO nanocomposites. The dielectric constant and loss factor of the composites were studied as a function of frequency. The composite sample with x = 0.50, results in higher value of dielectric constant whereas CFO possess lowest value of dielectric constant. The magnetization hysteresis (M−H) loop of the composites show ferromagnetic behavior with saturation magnetization values, Ms varies from 15 to 67.68 emu/g and coercive field Hc from 1538 to 1862 Oe. All the composites exhibit typical ferroelectric hysteresis loops indicating the presence of spontaneous polarization. The magnetoelectric voltage coefficient increases linearly with increases in applied d.c. magnetic bias field up to 8 KOe. The maximum value of magnetoelectric voltage coefficient, α ME = 7.7 mV/cm Oe for BTO-CFO composite having 25% ferrite and 75% ferroelectric content. The high ME voltage coefficient of BTO-CFO composite may be suitable for storage device application.

The magnetoelectric (ME) nanocomposite material contain ferromagnetic phase of yttrium iron garnet (Y3Fe5O12) and ferroelectric phase of yttrium perovskite ferrite (YFeO3) with an equation (x)YFeO3 + (1 − x)Y3Fe5O12 (x = 0.0, 0.25, 0.50, 0.75, 1.0) is synthesized by sol–gel auto combustion method. The composite powder obtained by two phases of composite material sintered at 1100 °C for 6 h. The prepared samples were investigated by using powder X-ray diffraction (XRD) to study the structural properties, that confirm the existence of two phases of Y3Fe5O12 and YFeO3. The crystallite size of material decreased from 23 to 13 nm with increasing the concentration of YFeO3 in composite. The morphological investigation of samples was studied by field emission scanning electron microscopy that gives size, shape and distribution of grains in material and confirmed that material has nano-crystalline in nature. Saturation magnetization (Ms) studied by using vibrating sample magnetometer shows the decrement in its value from 23.9 to 0.48 emu/g with the increase in YFeO3 content. Maximum magnetoelectric coefficient (αME) of 10.711 mv/cm-Oe is observed for composition x = 0.50. Similarly, ferroelectric characteristics of sample such as dielectric constant and dielectric loss were measured in the frequency range 20 Hz to 10 MHz at room temperature. The value of dielectric constant is decreases with increasing frequency and ferroelectric hysteresis loop at room temperature is study by using P-E loop tracer it’s nature is unsaturated due to presence of Y3Fe5O12 phase.

Effect of swift heavy ions (SHI) on low-k SiO2 thin films has been investigated. SiO2 thin films were deposited on pre-cleaned p-Si substrate by using sol-gel spin coating technique. Further, deposited films were annealed at 400 ∘C to remove structural irregularities. Prepared samples were irradiated with 200 MeV Ag15+ ions at different ion fluence such as 5 × 1011, 1 × 1012 and 5 × 1012 ions/cm2. Deposition of SiO2 was confirmed by using EDAX and FTIR spectroscopy. Increase in ion fluence increases the RMS roughness from 1.49 to 7.79 nm. The transformation of deposited material from polycrystalline to amorphous nature was confirmed from XRD spectra. Increase in SHI fluence decreases the grain size from 181.3 to 74.1 nm for pristine and sample irradiated at 5 × 1011 ions/cm2. Whereas, for sample irradiated with 5 × 1011 ions/cm2 fluence doesn’t show crystalline peak at (011). It is observed that SHI irradiation leads to grain agglomeration with decrease in crystal size at higher fluence. Further, conductivity of the samples under study was observed to be decreased with increase in ion fluence. Thus, it is demonstrated that the surface and structural properties of low-k silica thin films can be tailored by controlling the SHI fluence.

The non-ionic surfactant polysorbate 80 (Tween-80) based single step HF assisted mesoporous low-k films were synthesized by using sol–gel spin coating technique. The obtained films were annealed at 150 °C for 1 h to remove the added porogen and the pore solvents. Film thickness and refractive index were measured by spectral ellipsometry and changes in chemical compositions were investigated by using FTIR spectroscopy. The formation of SiO2 in film matrix and incorporation of low polar bonds like F and C were confirmed from obtained FTIR spectra. The porous nature of deposited film was confirmed from FE-SEM micrograph and the measured average pore diameter of mesopores was found to be 16.54 nm. The highest porosity percentage of 60.74% was obtained for the annealed sample deposited with 1 ml of Tween-80 in coating solution. The measured RMS roughness of the samples before and after annealing was observed to be increased from 0.029 to 0.079 nm. The lowest dielectric constant extracted from C–V curve measurement is of 1.06. These obtained mesoporous films with lower k value of 1.06 may be a suitable candidate as interlayer dielectric (ILD) for back end of line (BEOL) in CMOS technology.

Low dielectric constant (Low-[Formula: see text]) films are used as inter layer dielectric (ILD) in nanoelectronic devices to reduce interconnect delay, crosstalk noise and power consumption. Tailoring capability of porous low-[Formula: see text] films attracted more attention. Present work investigates comparative study of xerogel, aerogel and porogen based porous low-[Formula: see text] films. Deposition of SiO2 and incorporation of less polar bonds in film matrix is confirmed using Fourier Transform Infra-Red Spectroscopy (FTIR). Refractive indices (RI) of xerogel, aerogel and porogen based low-[Formula: see text] films observed to be as low as 1.25, 1.19 and 1.14, respectively. Higher porosity percentage of 69.46% is observed for porogen-based films while for shrinked xerogel films, it is lowered to 45.47%. Porous structure of low-[Formula: see text] films has been validated by using Field Emission Scanning Electron Microscopy (FE-SEM). The pore diameters of porogen based annealed samples were in the range of 3.53–25.50 nm. The dielectric constant ([Formula: see text]) obtained from RI for xerogel, aerogel and porogen based films are 2.58, 2.20 and 1.88, respectively.

The present work is focused towards the lowering of the k value of deposited SiO2 thin films by varying solvent concentration i.e. ethanol in the range 4-10 ml. Porous low-k thin films were synthesized by using the sol-gel spinon technique. A non-ionic surfactant polysorbate 80 (Tween 80) was used as a porogen to generate the porosity in the film matrix. The lower values of refractive index and film density were measured to be 1.19 and 0.94 gm/cm3 respectively for 10 ml solvent concentration. Further, the lowest k value of 2.2 and highest porosity percentage of 58.5 % were obtained for the same film due to the dilution of coating solution at higher solvent concentration. The water contact angle of the film was observed to be increased to 106.3° which indicates the transformation of the deposited film surface from hydrophilic to hydrophobic. The change in chemical structure as an effect of solvent concentration is studied by using FTIR. From FTIR spectra the disappearance of Si-OH groups at higher solvent concentration reveals the increase in condensation rate. Overall in this study, the result shows the significant change in structural, chemical and optical properties of the deposited films at 10 ml solvent concentration. Such deposited porous thin films with lower k value and enhanced hydrophobicity can be used as an interlayer dielectric (ILD) for back end of line (BEOL) in CMOS technology.

II-VI semiconductor based ternary CdMnS compound material has received more attention due to its wide area of applications in semiconductor technology. Cd1 – xMnxS (x  0, 0.2, 0.4, 0.6, 0.8 and 1.0) thin films were successfully prepared by chemical bath deposition technique on non-conducting glass substrates. Thin films were deposited at a bath temperature of 80 C and pH  11 by using the chemical bath reaction of cadmium chloride (CdCl2) and manganese chloride (MnCl2) with thiourea (NH4)2S in an aqueous solution. Further, the prepared samples were characterized by UV-visible spectroscopy, photoluminescence, XRD, SEM and EDAX to study the optical, structural, surface, and chemical properties. Effect of Mn2+ ions on the film thickness of Cd1 – xMnxS films was investigated using weight difference technique. The film thickness of Cd1 – xMnxS films decreases as Mn2+ ions increase in the bath solution. The polycrystalline nature with hexagonal and cubic structures of the as-deposited films was confirmed by XRD. The band gap value of the deposited films was observed to increase with increasing Mn2+ ion concentration, this might be ascribed to the fact that Cd atom was substituted by Mn atom in the CdS structure. EDAX analysis confirmed the deposition of Cd, Mn and S elements in the films. Photoluminescence spectra of Cd1 – xMnxS with different values of the composition parameter x exhibited two emission peaks with different intensities. The measurement of the electrical resistivity of Cd1 – xMnxS films was performed at room temperature using two probe methods. The variation in electrical resistivity values with compositional parameters was discussed based on deposition parameters. The investigated polycrystalline Cd1 – xMnxS thin films show promising technological applications in semiconductor industry.

Nanocrystalline Ce-substituted yttrium iron garnet (YIG) powders of different compositions, Y3−xCexFe5O12 (0 ≤ x ≤ 2.0), were synthesized by a combination of sol–gel auto-combustion and solid-state synthesis techniques. The as-obtained powder samples were sintered at 1150 °C for 10 h. The garnet structure formation is confirmed by the X-ray diffraction pattern, which shows that the calculated lattice parameter increased for x = 1.0 and shows a decreasing trend for x ≥ 1.0 with the addition of cerium ions. The lattice parameter increased from 12.38 A to 12.41 A for x ≤ 1.0 whereas it decreased from 12.412 A to 12.405 A with the cerium composition for x > 1.0. The average particle size determined by high resolution transmission electron microscopy is in the range of 50 to 90 nm and found to increase with the substitution of cerium ions in YIG. The room temperature magnetic parameters such as saturation magnetization, coercivity and remanence magnetization are greatly affected by the substitution of cerium ions. The values of saturation magnetization decrease from 25.5 to 15 emu g−1 whereas coercivity increases from 1 to 28 Oe with the substitution of cerium ions. The pure YIG sample shows polycrystalline nature that changed towards a single-crystal structure leading to a preferred-(100) orientation with the Ce substitution. The change from a ring to a spotty pattern observed in SAED confirmed the crystalline phase transformation and is well supported by HRTEM and magnetic measurements. The behavior of magnetic and electrical properties is well supported by the poly- and single-crystalline nature of YIG and Ce-YIG, respectively. The crystal structure transformation in YIG brought about by Ce substitution could unveil enormous opportunities in the preparation of single-crystal materials from their polycrystalline counterparts.

Ferrite samples with a chemical formula Co0.5Ni0.5Al(x)Fe(2-x)O4 (where x = 0.0, 0.25, 0.5, 0.75 and 1.0) were synthesized by sol-gel auto-combustion method. The synthesized samples were annealed at 600 degrees C for 4 h. An analysis of X-ray diffraction (XRD) patterns reveals the formation of single phase cubic spinel structure. The lattice parameter decreased linearly with the increasing Al content x. Nano size of the powders were confirmed by the transmission electron micrographs (TEM). Particle size, bulk density decreased whereas specific surface area and porosity of the samples increased with the Al substitution. Cation distribution of constituent ions shows linear dependence of Al substitution. Based on the cation distribution obtained from XRD data, structural parameters such as lattice parameters, ionic radii of available sites and the oxygen parameter 'u' is calculated. Saturation magnetization (M(s)), magneton number (n(B)) and coercivity (H(c)) decreased with the Al substitution. Possible explanation for the observed structural and magnetic behavior with various Al content are discussed.

Sintering temperature and particle size dependent structural and magnetic properties of lithium ferrite (Li 0.5 Fe 2.5 O 4 ) were synthesized and sintered at four different temperatures ranging from 875 to 1475 K in the step of 200 K. The sample sintered at 875 K was also treated for four different sintering times ranging from 4 to 16 h. Samples sintered at 1475 K have the cubic spinel structure with a small amount of α-Fe 2 O 3 (hematite) and γ-Fe 2 O 3 (maghemite). The samples sintered at≤1275 K do not show hematite and maghemite phases and the crystals form the single phase spinel structure with the cation ordering on octahedral sites. Particle size of lithium ferrite is in the range of 13–45 nm, and is depend on the sintering temperature and sintering time. The saturation magnetization increased from 45 to 76 emu/g and coercivity decreases from 151 to 139 Oe with an increase in particle size. Magnetization temperature curve recorded in ZFC and FC modes in an external magnetic field of 100 Oe. Typical blocking effects are observed below about 244 K. The dielectric constant increases with an increase in sintering temperature and particle size.

Ferrite samples with a chemical formula Co0.5Ni0.5Al(x)Fe(2-x)O4 (where x = 0.0, 0.25, 0.5, 0.75 and 1.0) were synthesized by sol-gel auto-combustion method. The synthesized samples were annealed at 600 degrees C for 4 h. An analysis of X-ray diffraction (XRD) patterns reveals the formation of single phase cubic spinel structure. The lattice parameter decreased linearly with the increasing Al content x. Nano size of the powders were confirmed by the transmission electron micrographs (TEM). Particle size, bulk density decreased whereas specific surface area and porosity of the samples increased with the Al substitution. Cation distribution of constituent ions shows linear dependence of Al substitution. Based on the cation distribution obtained from XRD data, structural parameters such as lattice parameters, ionic radii of available sites and the oxygen parameter 'u' is calculated. Saturation magnetization (M(s)), magneton number (n(B)) and coercivity (H(c)) decreased with the Al substitution. Possible explanation for the observed structural and magnetic behavior with various Al content are discussed.

Now a days silica aerogel thin films are attracted more attention as an interlayer dielectric (ILD) application in ULSI technology due to the lowest dielectric constant. In present work, we report the successful deposition of silica aerogel thin films on Si wafer by sol-gel technique. Further, in order to introduce porosity the deposited thin films were dried at supercritical condition with different temperatures. Elipsometric study shows that the refractive index (RI) of as deposited film is observed to 1.44 whereas RI of super critically dried thin films is observed to be decreased to 1.29 for the film dried at 40 °C. The film thickness observed to be decreased from 200 to 129 nm with increase in supercritical drying temperature. The dielectric constant of the films is observed to be lowered to 2.8 for the film dried at 40 °C temperature. The pore volume and porosity of the films increased up to 0.25 and 37 % respectively with increase in drying temperature while the density of the films is decreases with increasing temperature

The Ni0.4Cu0.2Zn0.4 ferrites with different concentrations of Cr3+ were synthesized at a low temperature (450°C) using sol–gel auto-combustion method. The X-ray diffraction analysis of the samples confirms the formation of a single-phase cubic spinel structure. The lattice constant decreases from 8.331 to 8.253 Å with an increase in Cr3+ substitution. Bulk density decreases from 4.95 to 4.71 gm/cm3 whereas porosity increases from 9.34% to 14.76% with an increase in Cr3+ substitution. Transmission electron microscopy was adopted to determine the particle size. Particle size decreases from 19 to 13 nm with the addition of Cr3+ ions. Saturation magnetization, coercivity, and other hysteresis parameters were measured using a vibrating sample magnetometer at room temperature with a maximum magnetic field of 8 kOe. Magnetization decreases from 62 to 48 emu/g, whereas coercivity increases from 65 to 180 Oe. The direct current (DC) resistivity increases from 3.62 × 106 to 4.21 × 106 Ω cm with Cr3+ content x. The dielectric constant (ε ′) decreases with increasing concentration of Cr3+ ions.