Optical and electrical properties of indium tin oxide nanofibers prepared by electrospinning

Indium tin oxide (ITO) nanofibers were successfully prepared via an electrospinning method, followed by annealing at 400?°C. Mixed solutions of ITO nanoparticle sol and polyethylene oxide (PEO) were used as precursors of the nanofibers. The PEO decomposed during annealing to yield ITO fibers. The fibers were characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD), thermo-gravimetric/differential thermal analysis (TG/DTA), UV-vis spectrophotometry and four-probe resistivity measurements. The diameter of the prepared fibers was controlled by adjusting the flow rate and the applied electric current. In(2)O(3) crystallized in the ITO nanofibers with a crystallite size of 27?nm. The optical transmittance in the visible region approached 90% in films deposited for 5?min, confirming that the nanofiber film is still transparent in the optical region. The sheet resistance of the nanofiber film was linearly dependent on the inverse of the deposition time and on the PEO/ITO ratio.     

Reproducibility studies on thin-film copper indium diselenide prepared from copper indium oxide

Thin-film copper indium diselenide was prepared by selenization of copper indium oxide deposited by spray pyrolysis of an aqueous solution containing copper and indium salts. The degree of reproducibility in thickness, composition and electrical parameters was found to be good. The electrical parameters could be controlled and tuned for photovoltaic applications reproducibly by means of this cost-efficient fabrication technique. This revised version was published online in November 2006 with corrections to the Cover Date.     

Optical properties of amorphous-like indium zinc oxide and indium gallium zinc oxide thin films

The paper presents the optical properties of amorphous-like indium zinc oxide and indium gallium zinc oxide thin films with various In/(In + Zn) ratios obtained by Pulsed Laser Deposition. Thickness results obtained from simulations of X-ray Reflectivity and Spectroscopic Ellipsometry data were very similar. The dependence of density on stoichiometry resembles the corresponding dependence of the refractive index in the transparency range. A free carrier absorption was noted in the visible spectral range, leading to a weak absorbing thin transparent conductive oxide. On the other hand, the refractive index is smaller than those of based oxides (ZnO and In₂O₃), and counterbalance therefore the weak light absorption.     

Properties of indium oxide films prepared by the reactive evaporation of indium

Indium oxide films with an electrical resistivity of about $\text{4 × 10}{}^{\mathrm{?4}}\text{Ω}\text{cm}$ and good optical quality were prepared by the reactive evaporation of pure indium in the presence of 10^?4 Torr of oxygen. The Auger electron spectrum of these films shows a deficiency of oxygen and corresponds to a composition which can be represented as In₂O_2.85. In the absence of foreign doping agents, the conduction electrons are provided by indium atoms which are adjacent to oxygen vacancies and act as a donor level. The electrical conductivity of the films is shown to be modulated by variations in the partial pressure of oxygen over the film which change the extent of the non-stoichiometry of the oxide by incorporation of oxygen into or extraction of oxygen from the film.     

Morphology and microstructure investigations of YB66 nano-particles prepared by plasma chemical process

Nanocrystalline particles of YB66 were prepared by plasma chemical process, using starting powders of YB4 and B, and the morphology was examined by high-resolution transmission electron microscopy (HRTEM). The average grain size of the YB66 particles is less than 100 nm. All the YB66 nano-particles are cubic in shape, suggesting that they have been formed through a direct coagulation from a vapor phase. Facetting at the cube corners occurs in most particles. The [0 0 1] and [0 1 1] lattice images of a cubic particle with edge-length of 84 nm were obtained. The simulated and experimental images match very well. A considerable amount of coarse, nearly spherical YB6 particles and unreached boron were additionally found by HRTEM. © 1998 Kluwer Academic Publishers     

Characterization of nanocrystalline indium tin oxide thin films prepared by ion beam sputter deposition method

Indium tin oxide (ITO) thin films were deposited on glass substrates by ion beam sputter deposition method in three different deposition conditions [(i) oxygen (O₂) flow rate varied from 0.05 to 0.20 sccm at a fixed argon (1.65 sccm) flow rate, (ii) Ar flow rate changed from 1.00 to 1.65 sccm at a fixed O₂ (0.05 sccm) flow rate, and (iii) the variable parameter was the deposition time at fixed Ar (1.65 sccm) and O₂ (0.05 sccm) flow rates]. (i) The X-ray diffraction (XRD) patterns show that the ITO films have a preferred orientation along (400) plane; the orientation of ITO film changes from (400) to (222) direction as the O₂ flow rate is increased from 0.05 to 0.20 sccm. The optical transmittance in the visible region increases with increasing O₂ flow rate. The sheet resistance (R_s) of ITO films also increases with increasing O₂ flow rate; it is attributed to the decrease of oxygen vacancies in the ITO film. (ii) The XRD patterns show that the ITO film has a strong preferred orientation along (222) direction. The optical transmittance in the visible spectral region increases with an increase in Ar flow rate. The R_s of ITO films increases with increasing Ar flow rate; it is attributed to the decrease of grain size in the films. (iii) A change in the preferred orientations of ITO films from (400) to (222) was observed with increasing film thickness from 314 to 661 nm. The optical transmittance in the visible spectral region increases after annealing at 200 °C. The R_s of ITO film decreases with the increase of film thickness.     

Ultraflat indium tin oxide films prepared by ion beam sputtering

Indium tin oxide (ITO) films with a smooth surface (root-mean-square roughness; R_rms=0.40 nm) were made using a combination of the deposition conditions in the ion beam-sputtering method. Sheet resistance was 13.8 Ω/sq for a 150-nm-thick film grown at 150 °C. Oxygen was fed into the growth chamber during film growth up to 15 nm, after which, the oxygen was turned off throughout the rest of the deposition. The surface of the films became smooth with the addition of ambient oxygen but electrical resistance increased. In films grown at 150 °C with no oxygen present, a rough surface (R_rms=2.1 nm) and low sheet resistance (14.4 Ω/sq) were observed. A flat surface (R_rms=0.5 nm) with high sheet resistance (41 Ω/sq) was obtained in the films grown with ambient oxygen throughout the film growth. Surface morphology and microstructure of the films were determined by the deposition conditions at the beginning of the growth. Therefore, fabrication of ITO films with a smooth surface and high electrical conductivity was possible by combining experimental conditions.     

Properties of indium tin oxide films prepared by ion-assisted deposition

Conducting transparent films of indium tin oxide were deposited by 100 eV oxygen-ion-assisted deposition. A refractive index of 2.13 at 550 nm was obtained for films deposited onto ambient temperature substrates. The refractive index decreased with increasing substrate temperature to a value of 2.0 at 400°C. The sheet resistance of films 135 nm thick decreased from 800 Ω/□ for layers deposited onto room temperature substrates to around 25 Ω/□ at 400°C. Structural studies revealed that ion-assisted deposition onto ambient temperature substrates produced amorphous films, and that at temperatures above 100°C the films exhibit In₂O₃ crystallinity. In addition, it was found that the number of voids in the ion-bombarded films was reduced relative to that in films produced by conventional reactive evaporation.     

Annealing effects in indium oxide films prepared by reactive evaporation

The annealing effects of reactively evaporated indium oxide films in various ambients at temperatures of up to approximately 350°C are reported. It is concluded that the changes in the electrical parameters of the films are due to the chemisorption or desorption of oxygen atoms from the grain boundaries. From these studies the grain boundary barrier heights are found to be 26 meV and 43 meV for as-deposited and air-annealed films respectively.     

Properties of indium oxide/tin oxide multilayered films prepared by ion-beam sputtering

The preparation and characterization of indium oxide (InO _x )/tin oxide (SnO _y ) multilayered films deposited by ion-beam sputtering are described and compared with indium tin oxide (ITO) films. The structure and the optoelectrical properties of the films are studied in relation to the layered structures and the post-deposition annealing. Low-angle X-ray diffraction analysis showed that most films retained the regular layered structures even after annealing at 500° C for 16 h. As an example, we obtained a resistivity of 6×10^–4 cm and a transparency of about 85% in the visible range at a thickness of 110 nm in a multilayered film of InO _x (2.0 nm)/SnO _y (0.2 nm)×50 pairs when annealed at 300° C for 0.5 h in air. Hall coefficient measurements showed that this film had a mobility of 17 cm² V^–1 sec^–1 and a carrier concentration (electron density) of 5×10²⁰ cm^–3.     

Amorphous indium tungsten oxide films prepared by DC magnetron sputtering

Indium-tungsten-oxide (IWO) films were prepared by dc magnetron sputtering at ambient substrate temperature (T_s). Characteristics of the films were compared with those of In₂O₃–SnO₂ (ITO) thin films prepared under the same condition. The sputter-deposited IWO films have entirely amorphous structure with an average transmittance of over 85% in the visible range and exhibit a minimum resistivity of 3.2 × 10^–4cm at W content [W/(In + W)] of 0.57 at.%. An in-situ heating X-ray diffraction measurement have shown that the crystallization temperature of IWO films is higher than those of ITO films (150–160C) and increases with increasing W content. This enabled a smooth amorphous surface of IWO films as compared with a rough surface of partially crystallized ITO films as revealed by an atomic force microscopy. IWO films are useful for transparent electrode of organic light emitting diode and polymer LCDs because of the low resistivity, high transparency and smooth surface obtainable by the conventional dc magnetron sputtering at room temperature.     

Thin bismuth oxide films prepared through the sol–gel method

In this paper, thin and uniform bismuth oxide films were prepared by the sol–gel method. These films were annealed at different temperatures. X-ray diffraction, X-ray photoelectron spectroscopy, atom force microscopy techniques, a surface profiler and a spectrophotometer were applied to characterize these bismuth oxide films annealed at different temperatures. The results show that different annealing temperatures cause the transformation between monoclinic phase and tetragonal phase of bismuth oxides, and that bismuth oxide films annealed at 550 °C contain the highest intensity of tetragonal phase of bismuth oxides.     

Optical recording characteristics of molybdenum oxide films prepared by pulsed laser deposition method

Molybdenum-oxide (MoO₃)films were deposited on glass substrates (Corning #7059 with an area of 26 × 38 mm²) by pulsed laser deposition using an ArF excimer laser. It was found that after annealing at 340 °C for 10 min, the film thickness became 2.3 times that (approximately 30 nm) of the as-deposited film thickness. The difference in the transmittance, ΔT, between the annealed state and the as-deposited state was about 40% at a wavelength of 400 nm. X-ray diffraction spectra indicated that oxygen was absorbed into the MoO₃ films through the annealing process. From revolution testing of 30 nm-thick MoO₃ films without a protective layer deposited on a polycarbonate DVD-R disk substrate (120 mm?, 0.6 mm thickness), a write peak-power dependence of carrier-to-noise ratio (CNR) (recording on-land, at λ = 406 nm, NA = 0.65) of the 3T signal (58.5 MHz) was measured at a linear velocity of 5 m/s and a read power of 0.6 mW. Consequently, CNR near 50dB was obtained in the wide write-power margin ΔP of 7 mW (at peak powers between 3.5 and 10.5 mW). From SEM observations, it was recognized that bits of 0.25-0.30 μm size, corresponding to a storage capacity of 7-10GB/in² in the case of NA = 0.65, were formed. For the sample structure with an Al₂O₃ protective layer of ~ 20 nm thickness, a CNR near 50dB was obtained in the peak-power margin ΔP of 12 mW (at peak powers between 6.0 and 18.0 mW). Larger values of the CNR can be obtained if the film thickness of each layer including both the active and protective layers is optimized.     

The photocatalytic properties of bismuth oxide films prepared through the sol-gel method

In this research, thin bismuth oxide films were prepared through the sol-gel method. In order to study the influence of bismuth oxide crystal phases on the photocatalytic properties of bismuth oxide films, these films were annealed at different temperatures and then applied to decompose a typical textile industry pollutant (Rhodamine B). Scanning electron microscopy, X-ray diffraction and profilometry were applied to characterize these films. It has been found that different annealing temperatures cause the transformation of different bismuth oxide crystal phases, which leads to the different removals of Rhodamine B photolyzed using bismuth oxide films as photocatalyst.     

Low temperature dielectric studies of zinc oxide (ZnO) nanoparticles prepared by precipitation method

Using zinc nitrate as a precursor and NaOH starch as a stabilizing agent, hexagonal zinc oxide (ZnO) nanoparticles has been synthesized by precipitation method. The transmission electron microscopy (TEM) images show particles of nearly uniform spherical size of around 40 nm. The infrared spectroscopy (FT-IR) measurement reveals the peak at 500 cm^?1, corresponding to the Zn–O bond. Dielectric studies of ZnO nanoparticles show frequency dependence dielectric anomaly at low temperature (85–300 K). Results reveal that the capacitance and loss tangent decrease with the frequency while these parameters improve with the increasing of temperature. The increase of a.c. conductivity with the temperature indicates that the mobility of charge carriers is responsible for hopping and electronic polarization in ZnO nanoparticles.     

Optical and electronic properties of cobalt-doped zinc oxide films prepared by the sputtering method

In-doped ZnO, Co-doped ZnO and Li-doped NiO are successively deposited on quartz by the sputtering method. A current versus voltage curve of the three-layer device, in which the Indoped ZnO and Li-doped NiO are used as electrodes, reveals that the In-doped ZnO is an ohmic electrode and the Li-doped NiO is a blocking electrode with respect to electron injection. In photocurrent spectra of the three-layer device, there are two distinct peaks around 410 and 640 nm. The former is ascribed to the photoionization caused by the electric-dipole transition from the ground states,⁴A₂(F), to the conduction band, and the latter to the thermal emission from electronic excited states of Co²⁺,⁴T₁(P).     

Optical and electrical properties of zinc oxide/indium/zinc oxide multilayer structures

Zinc oxide/indium/zinc oxide multilayer structures have been obtained on glass substrates by magnetron sputtering. The effects of indium thickness on optical and electrical properties of the multilayer structures are investigated. Compared to a single zinc oxide layer, the carrier concentration increases from 8 × 10¹⁸ cm⁻³ to 1.8 × 10²⁰ cm⁻³ and Hall mobility decreases from 10 cm²/v s to 2 cm²/v s for the multilayer structure at 8 nm of indium thickness. With the increase of indium thickness, the transmittance decreases and optical band gap shifts to lower energy in multilayer structures. Results are understood based on Schottky theory, interface scattering mechanism and the absorption of indium layer.     

CO sensing devices based on indium oxide nanoparticles prepared by laser ablation in water

A simple and effective solution route for synthesizing colloidal indium oxide (In₂O₃) nanocrystallites, i.e. laser ablation in liquid (LAL), is reported. The morphology and chemical structure of the as-prepared samples were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectra (XPS). The results showed the formation of In₂O₃ nanoparticles with a bimodal distribution, consisting mainly of particles of small diameters (2-5 nm). Sensor devices prepared by spraying directly the LAL colloidal solutions on interdigitated alumina substrates exhibited good sensing properties for the detection of CO at very low concentrations.