Effects of Li/M (M = Al,Ga, In,and Er) co-doping on the electrical properties of BiFeO3–BaTiO3 ceramics

The defect structures and electrical properties of 0.75BiFeO₃–0.25BaTiO₃ ceramics have been modified using Li/M dopants (M?=?Al, Ga, In, and Er). The effects of Li/M dopants with various ionic radii and electronegativities on the crystal structure, dielectric properties, ferroelectricity, leakage, and insulation behaviors of the ceramics have been investigated. The doped ceramics displayed a typical perovskite structure with a dominant rhombohedral phase, but the impurities BaFe_0.24Fe_0.76O_2.88 emerged and increased in concentration as doping content x increased. As x increased, the dielectric loss reduced and the ferroelectricity improved noticeably. At x?=?6 mol%, leakage current and resistivity studies indicated that the ceramics showed enhanced insulating qualities, particularly high resistivity of?~?10¹¹ Ω cm was recorded in Li/Er-doped samples. The reduced oxygen vacancies are responsible for these results, which were evaluated by defect chemistry and validated by XPS analysis.

     

Insight into the Structural,Magneto-electronic,and Mechanical Characteristic of Y2MnZ (Z = Al,Ga, In) via DFT Computation

Journal of Superconductivity and Novel Magnetism - The first-principle calculations of density functional theory were used to study the structural, electronic, magnetic, mechanic, and half-metallic...     

Electrical transport properties of thin films of a-Se80 – x Ga20 Bix

Abstract

Dark conductivity measurements on thin films of a-Se_{80 – x} Ga₂₀ Bi_x (where x = 0, 5, 10, 15, 20) are reported in the temperature range 148–318 K. The results indicate that at higher temperatures (287–318 K), the conduction occurs in the band tails of localised states and at lower temperatures (148–287 K) the conduction is due to variable range hopping, which is in reasonable agreement with Mott's condition of variable range hopping conduction.     

Composition-dependent structural, optical and electrical properties of In x Ga1−x N (0.5 ≤ x ≤ 0.93) thin films grown by modified activated reactive evaporation

In this report, we have studied the compositional dependence of structural, optical and electrical properties of polycrystalline In _x Ga_1?x N thin films grown by modified activated reactive evaporation. The growth was monitored by optical emission spectroscopy. The thickness of the films was in the range ~600–800 nm. The phase, crystallinity and composition of the films were determined by X-ray diffraction, Raman spectroscopy and energy dispersive X-ray analysis. The surface morphology was studied by atomic force microscopy. The band gaps of these films obtained from transmittance and photoluminescence measurements were found to vary from 1.88 to 3.22 eV. All the films show n-type conductivity. The carrier concentration was found to be decreasing with increase in gallium incorporation which is in good agreement with the free carrier absorption observed in transmittance spectra.     

Structural and optical properties of In doped Se–Te phase-change thin films: A material for optical data storage

Se_75−xTe₂₅In_x (x = 0, 3, 6, & 9) bulk glasses were obtained by melt quench technique. Thin films of thickness 400 nm were prepared by thermal evaporation technique at a base pressure of 10⁻⁶ Torr onto well cleaned glass substrate. a-Se_75−xTe₂₅In_x thin films were annealed at different temperatures for 2 h. As prepared and annealed films were characterized by X-ray diffraction and UV–Vis spectroscopy. The X-ray diffraction results show that the as-prepared films are of amorphous nature while it shows some poly-crystalline structure in amorphous phases after annealing. The optical absorption spectra of these films were measured in the wavelength range 400–1100 nm in order to derive the extinction and absorption coefficient of these films. It was found that the mechanism of optical absorption follows the rule of allowed non-direct transition. The optical band gap of as prepared and annealed films as a function of photon energy has been studied. The optical band gap is found to decrease with increase in annealing temperature in the present glassy system. It happens due to crystallization of amorphous films. The decrease in optical band gap due to annealing is an interesting behavior for a material to be used in optical storage. The optical band gap has been observed to decrease with the increase of In content in Se–Te glassy system.     

Structural and optical properties of Cd x Zn(1 − x)Te thin films

Seven Cd _x Zn_{(1 ? x} Te solid solutions with x = 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1.0 were synthesized by fusing stoichiometric amounts of CdTe and ZnTe constituents in silica tubes. Each composition was used in the preparation of a group of thin films of different thicknesses. Structural investigation of the obtained films indicates they have a polycrystalline structure with predominant diffraction lines corresponding to (111) (220) and (311) reflecting planes, which can be attributed to the characteristics of growth with the (111) plane. The optical constants (the refractive index n, the absorption index k, and the absorption coefficient α) of Cd _x Zn_{(1 \s -x)} Te thin films were determined in the spectral range 500–2000 nm. At certain wavelengths it was found that the refractive index, n, increases with increasing molar fraction, x. It was also found that plots of α² (hv) and α^1/2 (hv) yield straight lines, corresponding to direct and indirect allowed transitions respectively obeying the following two equations: $$\begin{gathered} E_g^d = 1.583 + 0.277x + 0.197x^2 \hfill \\ E_g^{ind} = 1.281 + 0.111x + 0.302x^2 \hfill \\ \end{gathered}$$      

Synthesis,structure, and optical properties of Au–TiO2 composite thin films

Titanium dioxide (TiO₂) films with varying concentrations of gold particles were synthesized using pulsed DC magnetron sputtering, with the intent to develop infrared reflecting films for use on cars and planes to reduce solar heat load. Under our deposition conditions, the films are smooth (RMS roughness on the order of 1.0–2.0 nm) and consist of rutile TiO₂ with embedded gold. The average gold particle diameter on the sample surface was found to change from 60 to 200 nm as the volume fraction of gold in the films increased from 1.9 to 4.3% (3.5 to 7.9 mol% Au). The maximum reflectance of these films in the infrared region (800–2500 nm) is > 50%, compared with 30% for pure TiO₂. The Maxwell–Garnett equation does not model the reflectance data very well, due to the relatively large gold particle size. Instead, by assuming that the contribution of gold particles to the reflectance response is proportional to their projected areal fraction in an effective medium approximation, we were able to fit the observed reflectance data quite well.     

PCLT/P(VDF-TrFE) 0–3 nanocomposite thin films for pyroelectric applications

 Nanocrystalline calcium and lanthanum modified lead titanate (PCLT) powder was prepared by a sol-gel process followed by annealing at 850°C. 0–3 nanocomposite thin films of PCLT powder dispersed in a vinylidene fluoride /trifluoroethylene (P(VDF-TrFE)) copolymer matrix were fabricated on glass substrates using the spin-coating technique. The permittivity, pyroelectric coefficient, specific heat and pyroelectric figures-of-merit were measured as functions of the volume fraction (φ) of ceramic for φ up to 0.16. Single-element pyroelectric sensors with PCLT/P(VDF-TrFE) nanocomposites as the sensing elements were fabricated and characterized. The voltage and current responsivities R_v and R_i of the sensors were measured as functions of frequency and found to agree well with the calculated values. Since the pyroelectric coefficients of PCLT and P(VDF-TrFE) have like signs while the piezoelectric coefficients have opposite signs, the poled composite has high pyroelectric but low piezoelectric activity, thereby reducing the vibration-induced electrical noise in pyroelectric sensor applications. Received: 21 July 1998 / Reviewed and accepted: 22 October 1998     

Growth and optical properties of Sn–Si nanocomposite thin films

The growth and optical properties of nanocomposite thin films comprising of nanocrystalline Sn and Si are reported. The nanocomposite films are produced by thermal annealing of bilayers of Sn and Si deposited on borosilicate glass substrates at various temperatures from 300 to 500 °C for 1 h in air. X-ray diffraction reveals that the as-deposited bilayers consist of nanocrystalline Sn films with a crystallite size of 30 nm, while the Si thin films are amorphous. There is onset of crystallinity in Si on annealing to 300 °C with the appearance of the (111) peak of the diamond cubic structure. The crystallite size of Si increases from 5 to 18 nm, whereas the Sn crystallite size decreases with increase in annealing temperature. Significantly, there is no evidence for any Sn–Si compound, and therefore it is concluded that the films are nanocomposites of Sn and Si. Measured spectral transmittance curves show that the films have high optical absorption in the as-deposited form which decreases on annealing to 300 °C. The films show almost 80 % transmission in the visible-near infrared region when the annealing temperature is increased to 500 °C. There is concomitant decrease in refractive index from 4.0, at 1750 nm, for the as-deposited film, to 1.88 for the film annealed at 500 °C. The optical band gap of the films increases on annealing (from 1.8 to ~2.9 eV at 500 °C). The Sn-Si nanocomposites have high refractive index, large band gap, and low optical absorption, and can therefore be used in many optical applications.     

Growth and characterization of Zn1 – x Mg x S thin films for electroluminescent applications

:Mn thin films (x=0–0.30) were prepared by thermal co-evaporation of ZnS, Mg and Mn. The structural investigation shows the solid solution is formed in the Mg composition range x=0–0.25 and phase segregation occurs at higher Mg composition (x > 0.25). The optical band gap shows an increase with increase of Mg composition. The electroluminescent emission corresponding to the transition ion shows a blue shift with increase of Mg composition in the film. :Mn films could be used as an active layer in a.c. thin film electroluminescent (ACTFEL) devices for obtaining green emission color.     

Structure,mechanical properties,corrosion behavior and cytotoxicity of biodegradable Mg–X (X = Sn,Ga, In) alloys

As-cast Mg–Sn, Mg–Ga and Mg–In alloys containing 1–7 wt.% of alloying elements were studied in this work. Structural and chemical analysis of the alloys was performed by using light and scanning electron microscopy, energy dispersive spectrometry, x-ray diffraction, x-ray photoelectron spectroscopy and glow discharge spectrometry. Mechanical properties were determined by Vickers hardness measurements and tensile testing. Corrosion behavior in a simulated physiological solution (9 g/l NaCl) was studied by immersion tests and potentiodynamic measurements. The cytotoxicity effect of the alloys on human osteosarcoma cells (U-2 OS) was determined by an indirect contact assay. Structural investigation revealed the dendritic morphology of the as-cast alloys with the presence of secondary eutectic phases in the Mg–Sn and Mg–Ga alloys. All the alloying elements showed hardening and strengthening effects on magnesium. This effect was the most pronounced in the case of Ga. All the alloying elements at low concentrations of approximately 1 wt.% were also shown to positively affect the corrosion resistance of Mg. But at higher concentrations of Ga and Sn the corrosion resistance worsened due to galvanic effects of secondary phases. Cytotoxicity tests indicated that Ga had the lowest toxicity, followed by Sn. The most severe toxicity was observed in the case of In.     

Effect of different solvents on the key structural,optical and electronic properties of sol–gel dip coated AZO nanostructured thin films for optoelectronic applications

Transparent conducting aluminum (i.e. 2 at.%) doped zinc oxide (AZO) thin films were prepared on glass substrates by sol–gel dip coating technique using different solvents. This inexpensive dip coating method involves dipping of substrate consecutively in zinc solution and tube furnace for required cycles. Prepared films were investigated by XRD, SEM, PL, Raman spectroscopy optical and electrical studies. From the XRD studies, it confirmed the incorporation of aluminum in ZnO lattice. The prepared samples are polycrystalline nature, and these films reveal hexagonal wurtzite arrangement with (002) direction. The structural parameters such as crystallite size, dislocation density, micro strain, texture coefficient and lattice constant were investigated. SEM study showed well defined smooth and uniformed ganglia shaped grains are regularly distributed on to the entire glass substrate without any pinholes and cracks, and the average grain size is 75 nm. From the optical studies, the observed highest transmittance is 93% in the visible range and the band gap (E_g) is 3.26 eV. Room temperature PL spectra exhibited strong UV emission peak located at 386 nm for all the films. The electrical properties of the AZO thin films were studied by Hall-Effect measurements and found as n-type conductivity with high carrier concentrations (n), 2.76?×?10¹⁹ cm^??3 and low resistivity (ρ), 7.56?×?10^??3 Ω cm for the film deposed using methanol as solvent.     

Selenization of electrodeposited copper–indium alloy thin films for solar cell applications

Copper–Indium (Cu–In) alloys with sulfur and selenium have technological importance in the development of thin film solar cell technology. We have used potentiostatic electrochemical technique with three-electrode geometry for the deposition of Cu–In alloy thin films in an aqueous electrolyte. Cathodic voltammetry (CV) was thoroughly studied to optimize the electrodeposition parameters. The deposition potential for Cu–In alloy was found to be in the range ?0.70 to ?0.85 V versus Ag/AgCl reference electrode. Polycrystalline Cu_xIn_y thin films were electrodeposited from aqueous bath at room temperature and 45 °C. Effect of concentration of citric acid was extensively studied by CV measurements. The as-deposited Cu–In films were characterized with a range of characterization techniques to study the structural, morphological, compositional and electrical properties. Thin layers of Cu–In were selenized in a homemade tubular furnace at 400 ^°C, which reveals the formation of polycrystalline CuInSe₂ (CISe) thin films with tetragonal structure. The band gap of CISe thin film was estimated ~1.05 eV by optical absorption spectroscopy. Nearly stoichiometric CISe thin film, Cu = 25.25 %, In = 26.48 % and Se = 48.27 % was obtained after selenization. The linear behavior of current density–voltage (J–V) was observed for Cu–In alloy thin films whereas, the selenized Cu–In alloy films (CISe) possess rectifying properties.     

Structural,optical and electrical properties of Bi2−xMnxTe3 thin films

Journal of Materials Science: Materials in Electronics - Undoped and Mn doped Bi2Te3 (x = 0, 0.05 and 0.10 at%) thin films were prepared via thermal evaporation method from their bulk alloys. X-ray...     

Enhanced second-harmonic response and stability of corona-poled guest—host polycarbonate thin films

Second-harmonic generation and spectroscopic absorption measurements were made to study the non-linear optical and stability properties of guest/host polycarbonate thin films in which the guest chromophores were oriented by corona poling. Optimum poling conditions were achieved at temperatures less than the glass-rubber transition temperatures. Stabilized order parameters as high as 0.23 and retention of orientational order as high as 86% were found. Stable, resonance-enhanced, values of the non-linear optical coefficient d ₃₃, for the fundamental of 1.064 m, were as high as 31 pm V^–1. This value is over four times that predicted by a simple thermodynamic model for isotropic materials. Hydrogen bonding between the guest and polycarbonate is proposed to account for the high d ₃₃ coefficients and long-term stability of the films.     

High-responsivity (Ga2Ge)100−x(Ga3Sb2)x (x = 15, 30, 45, 60) photodetection sensor for optoelectronic applications

Journal of Materials Science: Materials in Electronics - Electromagnetic signal detection for applications such as astronomy, product quality monitoring, health, and necessitates systems that are...     

Antibacterial and tribological properties of TaN–Cu,TaN–Ag,and TaN–(Ag,Cu) nanocomposite thin films

In this study, attempts were made to prepare and characterize TaN–(Cu,Ag) nanocomposite films by using a hybrid approach combining reactive co-sputtering and rapid thermal annealing at various temperatures to induce the formation of soft metal particles in the matrix or on the surface. The films’ properties and their antiwear and antibacteria behaviors were compared with those previously studied TaN–Cu and TaN–Ag films. All three types of TaN–(soft metal) films showed good tribological properties due to the lubricious Ag and/or Cu layers. It was also found that the antibacteria efficiency of TaN–(Ag,Cu) film against either Escherichia coli or Staphylococcus aureus could be much improved, comparing with that of TaN–Ag or TaN–Cu film. The synergistic effect due to the coexistence of Ag and Cu is obvious. The annealing temperature used to develop TaN–(Cu,Ag) films with good antibacterial and antiwear behaviors could be as low as 250 °C. The lowering of the annealing temperature made these films applicable onto low-melting-point materials, such as polymers.     

Role of chlorine on the opto-electronic properties of β-In2S3 thin films

Effect of chlorine doping on the opto-electronic properties of β-In₂S₃ thin film, deposited by spray pyrolysis technique is studied for the first time. Chlorine was incorporated in the spray solution, using HCl. Pristine sample prepared using In(NO₃)₃ and thiourea as the precursors showed very low photosensitivity. But upon adding optimum quantity of chlorine, the photosensitivity increased by 3 orders. X-ray analysis revealed that crystallinity was also increasing up to this optimum level of Cl concentration. It was also observed that samples with high photosensitivity were having higher band gap. The present study proved that doping with chlorine was beneficial as this could result in forming crystalline and photosensitive films of indium sulfide.     

CuIn(S,Se)2 thin films prepared by selenization and sulfurization of sputtered Cu–In precursors

CuIn(S,Se)₂(CISSe) thin films have been prepared onto soda-lime-glass (SLG) substrates by selenization and sulfurization of magnetron sputtered Cu–In precursors. The results indicate that the properties of the CISSe films are strongly dependent on the post-annealing treatment. After annealing at 400 °C for 20 min, the CISSe films have formed tetragonal (chalcopyrite) crystal structure and the diffraction peaks of the films shift systematically to the left with the temperature varying from 400 °C to 500 °C. EDAX study reveals that the compositions of CISSe films are Cu_0.83In_1.17S_1.67Se_0.3, Cu_0.86In_1.13S_1.61Se_0.4 and Cu_0.82In_1.15S_1.54Se_0.49 after annealing at 400 °C, 450 °C and 500 °C, respectively. The direct optical band gaps of the films slightly decrease from 1.44 ev to 1.32 ev with the increase of the temperature from 400 °C to 500 °C, and the optical absorption coefficient is over 10⁵ cm⁻¹. The films annealed at 400 °C–500 °C are all found to be p-type and the resistivity is almost 10⁻²–10⁻³ Ω cm. The carrier mobility of the film at 500 °C is almost as high as 1.701 cm²/V S.