Preparation and characterization of F doped SnO2 films and electrochromic properties of FTO/NiO films

The dependence of structural and electrical properties of SnO₂ films, prepared using spray pyrolysis technique, on the concentration of fluorine is reported. X-ray diffraction, FTIR and scanning electron microscope (SEM) studies have been performed on SnO₂:F (FTO) films coated on glass substrates. Measured values of Hall coefficient and resistivity are reported. The 7.5 m% of F doped film had a resistivity of 15 × 10⁻⁴ Ω cm, carrier density of 18.7 × 10¹⁹ cm⁻³ and mobility of 21.86 cm² V⁻¹ S⁻¹. The NiO film was coated on an FTO substrate and its electrochromic (EC) behavior was studied and the results are reported and discussed in this paper.     

Magneto-transport of InAs-quantum wells using InP0.69Sb0.31as a barrier material

InAs/InP_0.69Sb_0.31quantum-well structures grown by metal organic vapor-phase epitaxy are studied by temperature-dependent Hall measurements and by quantum Hall and Shubnikov de Haas effect measurements. At temperatures below 0.3 K a two-dimensional electron gas without a conductive by-pass was demonstrated. For a two-dimensional electron gas with a sheet electron concentration of 2.2 × 10¹²cm⁻²mobilities as high as 118 000 cm²(Vs)⁻¹were observed. In contrast to samples doped on both sides of the quantum well, a beating pattern in the longitudinal resistance was observed for samples which were doped on only one side. This effect is explained by spin–orbit coupling of the electrons in the quantum well which leads to a separation in two spin-splitted subbands. A spin-split energy in the range from 6.9 meV to 8.4 meV was extracted from the Shubnikov de Haas measurements.     

Large spontaneous Hall angle in [Co,CoFe/Pt] multilayer

We have quantitatively investigated the Hall effect in [Co, CoFe/Pt] multilayer films. The [Co, CoFe/Pt] multilayers exhibit large spontaneous Hall resistivity (ρ_H) and Hall angle (ρ_H/ρ). Even though the Hall resistivity in [Co, CoFe/Pt] multilayer films (2.7–4 × 10⁻⁷ Ω cm) is smaller than that of amorphous RE–TM alloy films which show large spontaneous Hall resistivity (<2 × 10⁻⁶ Ω cm), the Hall angle of multilayer (6–8%) is almost twice than that in amorphous rare earth–transition metal alloy films (∼3%). The Hall angle provides evidence of the effects of the exchange interaction of the Hall scattering. The exchange is between conduction electron spins and the localized spins of the transition metal. The large Hall angle of [Co, CoFe/Pt] multilayer can be considered due to the high spin polarization and high Curie temperature of Co and CoFe transition metal layers. Even though the role of interfaces and surfaces in the magnetic properties of multilayer films may dominate that of the bulk, the Hall effects in [Co, CoFe/Pt] multilayer may be mainly dominated by the bulk effect.     

Modifications in physical,optical and electrical properties of tin oxide by swift heavy Au8+ ion bombardment

Tin oxide thin films were deposited by a novel technique called as modified-SILAR. The preparative parameters were optimized to obtain good quality thin films. As-deposited films were annealed in O₂ atmosphere for 1 h at 500 °C. The annealed films were irradiated using Au⁸⁺ ions with energy of 100 MeV at different fluencies of 1 × 10¹¹, 1 × 10¹², 5 × 10¹² and 1 × 10¹³ ions/cm² using tandem pelletron accelerator. The irradiation-induced modifications in tin oxide thin films were studied using XRD, AFM, optical band gap, photoluminescence and I–V measurements. XRD studies showed formation of tin oxide with tetragonal structure. AFM revealed uniform deposition of the material with increase in grain size after irradiation. Decrease in band gap from 3.51 eV to 2.82 eV was seen with increases in fluency. A decrease in PL intensity, and an additional peak was observed after irradiation. I–V measurements showed a decrease in resistance with fluency.     

Transport and phase dynamics of poly(vinyl pyrrolidone) doped plastically crystalline N-methyl-N-propylpyrrolidinium tetrafluoroborate

The plastic crystal phase forming N-methyl-N-propylpyrrolidinium tetrafluoroborate organic salt (P₁₃BF₄) was combined with 2, 5 and 10 wt.% poly(vinyl pyrrolidone) (PVP). The ternary 2 wt.% PVP/2 wt.% LiBF₄/P₁₃BF₄ was also investigated. Thermal analysis, conductivity, optical thermomicroscopy, and Nuclear Magnetic Resonance (¹¹B, ¹⁹F, ¹H, ⁷Li) were used to probe the fundamental transport processes. Both the onset of phase I and the final melting temperature were reduced with increasing additions of PVP. Conductivity in phase I was 2.6 × 10^− 4 S cm^− 1 5.2 × 10^− 4 S cm^− 1 1.1 × 10^− 4 S cm^− 1 and 3.9 × 10^− 5 S cm^− 1 for 0, 2, 5 and 10 wt.%PVP/P₁₃BF₄, respectively. Doping with 2 wt.% LiBF₄ increased the conductivity by up to an order of magnitude in phase II. Further additions of 2 wt.% PVP slightly reduced the conductivity, although it remained higher than for pure P₁₃BF₄.     

Epitaxial ZnO thin films grown by pulsed electron beam deposition

In this work, the pulsed electron beam deposition method (PED) is evaluated by studying the properties of ZnO thin films grown on c-cut sapphire substrates. The film composition, structure and surface morphology were investigated by means of Rutherford backscattering spectrometry, X-ray diffraction and atomic force microscopy. Optical absorption, resistivity and Hall effect measurements were performed in order to obtain the optical and electronic properties of the ZnO films. By a fine tuning of the deposition conditions, smooth, dense, stoichiometric and textured hexagonal ZnO films were epitaxially grown on (0001) sapphire at 700 °C with a 30° rotation of the ZnO basal plane with respect to the sapphire substrate. The average transmittance of the films reaches 90% in the visible range with an optical band gap of 3.28 eV. Electrical characterization reveals a high density of charge carrier of 3.4 × 10¹⁹ cm^?3 along with a mobility of 11.53 cm²/Vs. The electrical and optical properties are discussed and compared to ZnO thin films prepared by the similar and most well-known pulsed laser deposition method.     

Synthesis of ammonia at atmospheric pressure with Ce0.8M0.2O2−δ (M = La,Y, Gd,Sm) and their proton conduction at intermediate temperature

Ionic conduction in fluorite-type structure oxide ceramics Ce_0.8M_0.2O_2−δ (M = La, Y, Gd, Sm) at temperature 400–800 °C was systematically studied under wet hydrogen/dry nitrogen atmosphere. On the sintered complex oxides as solid electrolyte, ammonia was synthesized from nitrogen and hydrogen at atmospheric pressure in the solid states proton conducting cell reactor by electrochemical methods, which directly evidenced the protonic conduction in those oxides at intermediate temperature. The rate of evolution of ammonia in Ce_0.8M_0.2O_2−δ (M = La, Y, Gd, Sm) is up to 7.2 × 10^− 9, 7.5 × 10^− 9, 7.7 × 10^− 9, 8.2 × 10^− 9 mol s^− 1 cm^− 2, respectively.     

Oxygen diffusion and surface exchange studies on (La0.75Sr0.25)0.95Cr0.5Mn0.5O3−δ

Oxygen tracer diffusion coefficient (D^⁎) and surface exchange coefficient (k^⁎) have been measured for (La_0.75Sr_0.25)_0.95Cr_0.5Mn_0.5O_3−δ using isotopic exchange and depth profiling by secondary ion mass spectrometry technique as a function of temperature (700–1000 °C) in dry oxygen and in a water vapour-forming gas mixture. The typical values of D^⁎ under oxidising and reducing conditions at ∼ 1000 °C are 4 × 10^− 10 cm² s^− 1 and 3 × 10^− 8 cm² s^− 1 respectively, whereas the values of k^⁎ under oxidising and reducing conditions at ∼ 1000 °C are 5 × 10^− 8 cm s^− 1 and 4 × 10^− 8 cm s^− 1 respectively. The apparent activation energies for D^⁎ in oxidising and reducing conditions are 0.8 eV and 1.9 eV respectively.     

Patterning of Aluminium thin film on polyethylene terephthalate by multi-beam picosecond laser

High speed patterning of a 30 nm thick Aluminium thin film on a flexible Polyethylene Terephthalate substrate was demonstrated with the aid of Computer Generated Holograms (CGH׳s) applied to a phase only Spatial Light Modulator. Low fluence picosecond laser pulses minimise thermal damage to the sensitive substrate and thus clean, single and multi-beam, front side thin film removal is achieved with good edge quality. Interestingly, rear side ablation shows significant Al film delamination. Measured front and rear side ablation thresholds were F_th=0.20±0.01 J cm⁻² and F_th=0.15±0.01 J cm⁻² respectively. With laser repetition rate of 200 kHz and 8 diffractive spots, a film removal rate of R>0.5 cm² s⁻¹ was demonstrated during patterning with a fixed CGH and 5 W average laser power. The effective laser repetition rate was f_eff~1.3 MHz. The application of 30 stored CGH׳s switching up to 10 Hz was also synchronised with motion control, allowing dynamic large area multi-beam patterning which however, slows micro-fabrication.     

Structural,XPS and impedance analysis of LixCoVO4 (x = 0.8, 1.0, 1.2)

Lithium cobalt vanadate Li_xCoVO₄ (x = 0.8; 1.0; 1.2) has been prepared by a solid state reaction method. The XRD analysis confirms the formation of the sample. A new peak has been observed for Li_1.0CoVO₄ and for Li_1.2CoVO₄ indicating the formation of a new phase. The XPS analysis indicates the reduction in the oxidation of vanadium and oxygen with the addition of Li in Li_xCoVO₄ (x = 0.8, 1.0, 1.2). The impedance analysis gives the conductivity value as 2.46 × 10^− 5, 6.16 × 10^− 5, 9 × 10^− 5 Ω^− 1 cm^− 1 for Li_xCoVO₄ (x = 0.8; 1.0; 1.2), all at 623 K. The similarity in the bulk activation energy (E_a) and the activation enthalpy for migration of ions (E_ω) indicate that the conduction in Li_1.2CoVO₄ has been due to hopping mechanism.     

A Boubaker polynomials expansion scheme (BPES)-related protocol for measuring sprayed thin films thermal characteristics

Measurements of In₂S₃ and ZnIn₂S₄ sprayed thin films thermal characteristics have been carried out using the photodetection technique. The thermal conductivity k and diffusivity D were obtained using a new protocol based on photothermal signal parameters analysis. Measured values of k and D were respectively, (15.2 ± 0.85) W m⁻¹K⁻¹ and (69.8 ± 7.1) × 10⁻⁶ m²s⁻¹ for In₂S₃, (7.2 ± 0.7) W m⁻¹K⁻¹ and (32.7 ± 4.3) × 10⁻⁶ m²s⁻¹ for ZnIn₂S₄. These values are extremely important since similar compounds are more and more proposed as Cd-free alternative materials for solar cells buffer layers.     

High quality nitrogen-doped zinc oxide thin films grown on ITO by sol–gel method

Highly transparent N-doped ZnO thin films were deposited on ITO coated corning glass substrate by sol–gel method. Ammonium nitrate was used as a dopant source of N with varying the doping concentration 0, 0.5, 1.0, 2.0 and 3.0 at%. The DSC analysis of prepared NZO sols is observed a phase transition at 150 °C. X-ray diffraction pattern showed the preferred (002) peak of ZnO, which was deteriorated with increased N concentrations. The transmittance of NZO thin films was observed to be ~88%. The bandgap of NZO thin films increased from 3.28 to 3.70 eV with increased N concentration from 0 to 3 at%. The maximum carrier concentration 8.36×10¹⁷ cm⁻³ and minimum resistivity 1.64 Ω cm was observed for 3 at% N doped ZnO thin films deposited on glass substrate. These highly transparent ZnO thin films can be used as a window layer in solar cells and optoelectronic devices.     

Characterization of LSGM films obtained by electrophoretic deposition (EPD)

The application of the electrophoretic deposition (EPD) technique to the preparation of high quality electrolyte films for intermediate temperature solid oxide fuel cells (IT-SOFCs) was investigated. Films of La_0.83Sr_0.17Ga_0.83Mg_0.17O_2.83 (LSGM) were deposited on Pt and La_0.8Sr_0.2MnO₃ (LSM) substrates from suspensions in acetone/ethanol (3:1 by volume) mixture solvent and sintered at 1300 °C. Pt supported LSGM films, 10–20 μm thick, exhibited good adhesion to the Pt substrate, well-distributed microporosity and some surface roughness. LSM supported films exhibited cracking after sintering at 1300 °C for 3 h. Up to 900 °C the bulk conductivity of the Pt supported LSGM film showed the same behaviour of LSGM pellet (E_a = 0.93 eV and 0.99 eV, respectively). The LSGM film exhibited lower bulk electrical conductivity than the latter (4.1 × 10^− 3 and 4.4 × 10^− 2 Ω^− 1 cm^− 1, respectively, at 700 °C). This difference should be ascribed to the slight Ga depletion in the LSGM film. An important issue remains the selection of adequate electrode for LSGM electrolyte films.     

Theoretical study of optoelectronic properties of GaAs1−xBix alloys using valence band anticrossing model

The (12 × 12) and (14 × 14) valence band anticrossing (V-BAC) models were applied to calculate the electronic band structure of GaAs_1−xBi_x dilute alloys along Δ-, Λ- and Σ-directions at room temperature. A comparative study based on these models was performed in terms of energy levels, optical transitions, spin–orbit splitting and effective mass. We found a significant reduction of the band-gap energy E_g by roughly 81 meV/%Bi accompanied by an increase in the spin–orbit splitting Δ_so+ by about 56 meV/%Bi. Furthermore, Δ_so+ does come into resonance with E_g at ∼12%Bi for resonance energy equal to 0.73 eV. An excellent agreement has occurred between the (14 × 14) V-BAC model predictions and experimental results reported in the literature. In addition, we have investigated the Bi composition and k-directions dependence of the effective mass at Γ point. A slight increase of the holes effective mass with x can affect the holes transport properties of GaAsBi. The intrinsic carrier density increases with both x and the temperature T, but it remains below 10¹⁰ cm⁻³ for x ⩽ 5% and T ⩽ 300 K.     

Investigating gate metal induced reduction of surface donor density in GaN/AlGaN/GaN heterostructure by electroreflectance spectroscopy

The internal field of GaN/AlGaN/GaN heterostructure on Si-substrate was investigated by varying the thickness of an undoped-GaN capping layer using electroreflectance spectroscopy. The four samples investigated are AlGaN/GaN heterostructure without a GaN cap layer (reference sample) and three other samples with GaN/AlGaN/GaN heterostructures in which the different thickness of GaN cap layer (2.7 nm, 7.5 nm, and 12.4 nm) has been considered. The sheet carrier density (n_s) of a two-dimensional electron gas has decreased significantly from 4.66 × 10¹² cm⁻² to 2.15 × 10¹² cm⁻² upon deposition of a GaN capping layer (12.4 nm) over the reference structure. Through the analysis of internal fields in each GaN capping and AlGaN barrier layers, it has been concluded that the undiminished surface donor states (n_s) of a reference structure and the reduced n_s caused by the Au gate metal are approximately 5.66 × 10¹² cm⁻² and 1.08 × 10¹² cm⁻², respectively.     

Chemical bath deposition of SnO2 and Cd2SnO4 thin films

A new approach of chemical bath deposition (CBD) of SnO₂ thin films is reported. Films with a 0.2 μm thickness are obtained using the multi-dip deposition approach with a deposition time as little as 8–10 min for each dip. The possibility of fabricating a transparent conducting oxide layer of Cd₂SnO₄ thin films using CBD is investigated through successive layer deposition of CBD-SnO₂ and CBD-CdO films, followed by annealing at different temperatures. High quality films with transmittance exceeding 80% in the visible region are obtained. Annealed CBD-SnO₂ films are orthorhombic, highly stoichiometric, strongly adhesive, and transparent with an optical band gap of ～4.42 eV. Cd₂SnO₄ films with a band gap as high as 3.08 eV; a carrier density as high as 1.7 × 10²⁰ cm^?3; and a resistivity as low as 1.01 × 10^?2 Ω cm are achieved.     

Extraordinary fast oxide ion conductivity in La1.61GeO5−δ thin film consisting of nano-size grain

Thin films of La_1.61GeO_5−δ, a new oxide ionic conductor, were fabricated on dense polycrystalline Al₂O₃ substrates by a pulsed laser deposition (PLD) method and the effect of the film thickness on the oxide ionic conductivity was investigated on the nanoscale. The deposition parameters were optimized to obtain La_1.61GeO_5−δ thin films with stoichiometric composition. Annealing was found necessary to get crystalline La_1.61GeO_5−δ thin films. It was also found that the annealed La_1.61GeO_5−δ film exhibited extraordinarily high oxide ionic conductivity. Due to the nano-size effects, the oxide ion conductivity of La_1.61GeO_5−δ thin films increased with the decreasing thickness as compared to that in bulk La_1.61GeO_5−δ. In particular, the improvement in conductivity of the film at low temperature was significant .The electrical conductivity of the La_1.61GeO_5−δ film with a thickness of 373 nm is as high as 0.05 S cm^− 1 (log(σ/S cm^− 1) = − 1.3) at 573 K.     

Ionic conductivity of polymer electrolyte membranes based on polyphosphazene with oligo(propylene oxide) side chains

A polyphosphazene [NP(NHR)₂]_n with oligo[propylene oxide] side chains − R = –[CH(CH₃)–CH₂O]_m–CH₃ (m = 6 – 10) was synthesized by living cationic polymerisation and polymer-analogue substitution of chlorine from the intermediate precursor [NPCl₂]_n using the corresponding primary amine RNH₂. The polymer had an average molecular weight of 3.3 × 10⁵ D. Polymer electrolytes with different concentrations of dissolved lithium triflate (LiCF₃SO₃) were prepared. Mechanically stable polymer electrolyte membranes were formed using UV radiation induced crosslinking of the polymer salt mixture in the presence of benzophenone as photoinitiator. The glass transition temperature of the parent polymer was found to be − 75 °C before cross linking. It increases after crosslinking and with increasing amounts of salt to a maximum of − 55 °C for 20 wt.% LiCF₃SO₃. The ionic conductivity was determined by impedance spectroscopy in the temperature range 0–80 °C. The highest conductivity was found for a salt concentration of 20 wt.% LiCF₃SO₃: 6.5 × 10^− 6 S·cm^− 1 at 20 °C and 2.8 × 10^− 4 S cm^− 1 at 80 °C. The temperature dependence of the conductivities was well described by the MIGRATION concept.     

M/Li+(M = Mg2+, Zn2+, and Mn2+) ion-exchange on lithium ion-conducting perovskite-type oxides and their properties

Lithium ions of perovskite-type lithium ion conductor La_0.55Li_0.35TiO₃ were replaced by divalent Mg²⁺, Zn²⁺, and Mn²⁺ ions in an ion-exchange reaction using molten chlorides. The polycrystalline Mg-exchanged and Zn-exchanged samples are solid electrolytes for divalent Mg²⁺ and Zn²⁺ ions, whose dc ionic conductivities (σ = 2.0 × 10^− 6 S cm^− 1 at 558 K for the Mg-exchanged sample, La_0.56(2)Li_0.02(1)Mg_0.16(1)TiO_3.01(2) and σ = 1.7 × 10^− 6 S cm^− 1 at 708 K for the Zn-exchanged samples, La_0.55(1)Li_0.0037(2)Zn_0.15(1)TiO_2.98(2)) were compared to those of the known highest Mg²⁺ and Zn²⁺ inorganic solid electrolytes. The Mn-exchanged sample, then, showed paramagnetic behavior in the temperature range of 2 to 300 K. The Mn ions in the exchanged sample are divalent and the spin configuration is in high spin state (S = 5/2).     

Modifications of structural,optical and electrical properties of nanocrystalline bismuth sulphide by using swift heavy ions

Modified chemical bath deposited (MCBD) bismuth sulphide (Bi₂S₃) thin films’ structural, optical and electrical properties are engineered separately by annealing in air for 1 h at 300 °C and irradiating with 100 MeV Au swift heavy ions (SHI) at 5 × 10¹² ions/cm² fluence. It is observed that the band gap of the films gets red shifted after annealing and irradiation from pristine (as deposited) films. In addition, there is an increase in the grain size of the films due to both annealing and irradiation, leading to the decrease in resistivity and increase in thermoemf of the films. These results were explained in the light of thermal spike model.