Indium Tin Oxide Matrix Research Articles

Novel Approach for Fabricating Transparent and Conducting SWCNTs/ITO Thin Films for Optoelectronic Applications

Single-walled carbon nanotubes (SWCNTs) incorporated in indium tin oxide (ITO) were developed to fabricate transparent conductive thin films via a sol–gel spin coating technique. The fabricated thin films were annealed at 350 °C. The effects of incorporating SWCNTs and varying film thickness on crystal structure were systematically investigated by X-ray diffraction (XRD), Raman shift, surface elemental compositions, surface topography and roughness, optoelectronic characteristics, and mechanical properties. XRD results confirmed the body-centered cubic structure of indium oxide polycrystalline phase, indicating that the structural properties of the ITO films were not significantly altered by incorporating CNTs. The presence of CNTs in the ITO matrix was confirmed by analyses of Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and energy dispersive X-ray spectroscopy (EDX). FESEM images revealed the formation of SWCNTs/ITO nanoparticles, and the average crystallite size increased along with incr...

Characterisation of Ti-doped indium tin oxide nanoparticles synthesised by co-precipitation process

Ti-doped indium tin oxide (ITO) nanoparticles (TITO) with different molar ratios of Ti:ITO were synthesised by co-precipitation method using Ti(OCH2CH2CH2CH3)4, InCl3 and SnCl4·5H2O as starting precursors. Deionised (DI) water was selected as the solvent in this process. The as-precipitated powders were calcined at different temperatures around 700°C for 2 h. For all samples, their crystal structures, optical properties and morphologies were investigated by X-ray diffraction (XRD), UV-Vis absorption spectroscopy, scanning electron microscope (SEM), and transmission electron microscope (TEM), respectively. XRD results reveal that the purity of as-synthesised samples is increased with the increase of calcination temperatures. Relevant mechanisms involved in the synthesis via precipitation process are discussed. It is noticed that the incorporation of Ti into ITO matrix significantly affects the relevant physical properties and optical properties.

Carbon nanotube/indium tin oxide hybrid transparent conductive film: Effect of nanotube diameter

Abstract Hybrid transparent conductive films (TCFs) based on indium tin oxide (ITO) and carbon nanotubes (CNTs) are prepared through a sol–gel dip coating method. The effect of CNT diameter on optoelectrical properties of TCF is investigated. The surface roughness and grain size are decreased and the optical transmittance is increased with CNT diameter. The existence of bundles in smaller CNTs is the main reason for lower transmittance in these samples. In terms of electrical resistivity, the large diameter CNT incorporated ITO film shows lower sheet resistance than bare ITO film at high enough film thicknesses. It seems that the large diameter CNT incorporation in ITO matrix can remarkably reduce the microcrack formation, especially at higher thicknesses, and act as nanobridges when microcracks are formed. Furthermore, the sensitivity of ITO film to thermal cycling is dramatically enhanced with these CNTs. In addition, the figure of merit of ITO film is considerably improved with large diameter CNT incorporation.

A transparent conductive oxide electrode with highly enhanced flexibility achieved by controlled crystallinity by incorporating Ag nanoparticles on substrates

We report the synthesis of highly flexible indium tin oxide (ITO) on a polymer substrate whose surface was engineered by oxide-coated Ag nanoparticles (AgNPs) smaller than 20 nm in diameter. Polyimide (PI) substrates were spin coated with Ag ion ink and were subsequently heat treated to form AgNP coatings. The Ag oxide was formed by O2 plasma treatment to reduce the light absorbance by AgNPs. ITO was dc magnetron sputter-deposited atop the AgNPs. The ITO on the AgNPs was crystalline grown primarily with (2 2 2) growth orientation. This contrasts to the typical microstructure of ITO grown on the polymer, which is that growing c-ITO nucleates are embedded in an amorphous ITO (a-ITO) matrix like a particulate composite. The surface roughness of ITO on AgNPs was as small as the ITO on PI without AgNPs. The crystalline nature of the ITO on the AgNP-coated polymer resulted in the decrease of electric resistivity (ρ) by 65% compared to that of ITO on the bare PI. Furthermore, an electric resistivity change (Δρ) of the ITO on the AgNPs was only 8% at a bending radius (rb) down to 4 mm, whereas the ITO on the non-coated polymer became almost insulating at an rb of 10 mm, owing to a drastic increase in the number of cracks. To validate the potential application in the displays, flexible organic light emitting diodes (f-OLEDs) were fabricated on the ITO on AgNPs and the performances was compared with the f-OLED on ITO on the bare PI.

Incorporating carbon nanotubes in sol-gel synthesized indium tin oxide transparent conductive films.

Carbon nanotubes (CNTs) are incorporated in indium tin oxide (ITO) films through a sol-gel dip coating method. CNT incorporation has no effect on lattice parameter and preferential orientation of the ITO matrix. Raman spectrum confirms the presence of CNTs in the ITO matrix. The surface roughness is decreased by CNT addition. Moreover, the optical transmittance of the ITO-CNT films is more than that of ITO films in the IR region. The higher transmittance region of the ITO-CNT films compared to that of ITO films is extended to the visible region with increasing thickness of the films. In terms of electrical resistance, the ITO film shows slightly lower sheet resistance compared to the ITO-CNT film. However, the sheet resistance of the ITO-CNT film is further reduced by thickness and reaches the minimum amount in the 15-layer deposited sample, which is lower than that of ITO samples. It seems that CNT incorporation in the ITO matrix can dramatically reduce microcrack formation, especially in higher thicknesses. Furthermore, the sensitivity of ITO films to thermal cycling is dramatically enhanced with CNT addition. In addition, the figure of merit of ITO films is strongly improved in the vis-NIR region with CNT incorporation.

Electrical and optical properties of ITO and ITO/Cr-doped ITO films

In this paper we report on the effects of the insertion of Cr atoms on the electrical and optical properties of indium tin oxide (ITO) films to be used as electrodes in spin-polarized light-emitting devices. ITO films and ITO(80 nm)/Cr-doped ITO(20 nm) bilayers and Cr-doped ITO films with a thickness of 20 nm were grown by pulsed ArF excimer laser deposition. The optical, structural, morphological and electrical properties of ITO films and ITO/Cr-doped structures were characterized by UV–Visible transmission and reflection spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM) and Hall-effect analysis. For the different investigations, the samples were deposited on different substrates like silica and carbon coated Cu grids. ITO films with a thickness of 100 nm, a resistivity as low as ∼4×10−4 Ω cm, an energy gap of ∼4.3 eV and an atomic scale roughness were deposited at room temperature without any post-deposition process. The insertion of Cr into the ITO matrix in the upper 20 nm of the ITO matrix induced variations in the physical properties of the structure like an increase of average roughness (∼0.4–0.5 nm) and resistivity (up to ∼8×10−4 Ω cm). These variations were correlated to the microstructure of the Cr-doped ITO films with particular attention to the upper 20 nm.

Flexible organic light-emitting diodes consisting of a platinum doped indium tin oxide anode

This paper demonstrates that a flexible organic light-emitting diode (OLED) with a platinum (Pt)-doped indium tin oxide (ITO) anode could show superior electro-optical characteristics to those of a conventional device. The threshold voltage and turn-on voltage of an OLED device consisting of an aluminium/lithium fluoride/tris(8-hydroxyquinoline) aluminium/N,N′-bis-(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine/Pt-doped ITO/ITO structure were reduced by 1.2 V and 0.8 V, respectively. Current efficiency was found improved for a driving voltage of less than 6.5 V as a result of the enhanced hole-injection rate, attributed mainly to the elevated surface work function and partly reduced surface roughness of ITO by the incorporated Pt atoms in the ITO matrix.

Nonlinear optical properties of copper nanoparticles synthesized in indium tin oxide matrix by ion implantation

Copper nanoparticles were elaborated in an indium tin oxide matrix by ion implantation. The nonlinear refraction and absorption coefficients of the composite materials obtained were measured using the z-scan method with nanosecond pulses (τ=7 ns) at the wavelength of 532 nm. In addition to the conventional on-axis z-scan configuration, measurements were carried out in the off-axis scheme to get a better sensitivity. The mechanisms responsible for nonlinear refraction and absorption in these nanocomposite materials are discussed. By using the temporal trace of the signal in the off-axis configuration, we show the thermal lensing effect to be negligible as compared with pure electronic ones.

Effects of Pt addition on the formation of Co–ITO granular magnetoresistance films by a two-step method

Platinum (Pt) has been added to Co–ITO (ITO: indium tin oxide) films to promote the formation of Co(Pt)–ITO granular structure by a two-step method which includes sputtering deposition at room temperature and postdeposition thermal annealing in a vacuum. Such films consist of magnetic Co(Pt) nanoparticles distributed uniformly in an amorphous ITO matrix. The Co(Pt) particles are formed during the thermal annealing by precipitation, and the matrix also contains certain amount of Co and Pt that suppress the crystallization of the amorphous ITO. Pt plays an important role in controlling the precipitation of Co(Pt) particles and the microstructure formation. First, by adding Pt into the films, more Co can be incorporated into the amorphous phase in the as-deposited state, which ensures sufficient Co to form magnetic particles through precipitation. Second, by incorporating Co and Pt into the film, the crystallization temperature of amorphous ITO is also increased to a temperature as high as 400°C. These two effects make it possible to fabricate the Co(Pt)–ITO granular magnetoresistance films by the two-step method.

In situ growth of Co nanofibers in In2O3–SnO2 matrix during sputtering deposition

Co-sputtering onto (001) cubic zirconia from a target of indium tin oxide (ITO) partially covered by cobalt (Co) was carried out at substrate temperatures of 470–770K in order to investigate the growth of Co nanofibers. During film growth, Co forms fibers in the growth direction in the single-crystalline ITO matrix. The cross section of the Co fibers, the size of which depends on the substrate temperature, was a rectangle with an edge 1–5nm in length. The edge length of the Co fiber increased with the increase of the substrate temperature. The present method is attractive for application to produce magnetic recording media.

Ferromagnetic, transparent and conducting ITO-Fe-cluster composite films

Indium-tin oxide (ITO)-Fe-cluster composite films were fabricated by plasma-gas-condensation-type cluster beam deposition and RF helicon sputtering method, and the structural, optical, electrical and magnetic properties of the films were investigated. The optical transmittance of about 90% is obtained for the Fe cluster layer thickness of 10 nm although it is decreased with increasing the cluster layer thickness. The resistivity is further decreased by embedding metalic Fe clusters into ITO matrix and a resistivity value of about an order of 10/sup -4//spl Omega/ cm was obtained. Moreover, the ITO-Fe cluster composite films show ferromagnetism at room temperature even for a cluster layer thickness of 10 nm.

DC-electric-field effect on CdSe nanocrystal embedded in Indium tin oxide film and its second-order nonlinearity

Abstract The effect of DC-electric-field on crystal-growth and second-order nonlinearity of CdSe nanocrystals embedded in amorphous indium tin oxide (ITO) films prepared by r.f. sputtering has been investigated. The current-voltage curves of the as-deposited films exhibit common characteristics; with raising voltage the current increases following the Ohmic law, and shows an abrupt decrease at around 36 V/cm. When samples were electrically-treated by applying a DC electric field of 50 V/cm, CdSe nanocrystals grew with the initial orientation kept unchanged as indicated by the X-ray diffraction patterns. Considering the fact that temperature of the sample surface was raised up to 250°C during the treatment, the crystal-growth occurred as a result of an increase in temperature due to the Joule heat. On the other hand, when the as-deposited films were heat-treated without applying voltage, CdSe crystallites grew with random orientations, accompanied by crystallization of ITO matrix at 400°C. From the difference in crystallization bahavior between the electrically- and heat-treated films, we infer that the preferential crystal-growth of CdSe in the electrically-treated film can be attributed to the electric field as well as the Joule heat. The second-harmonic intensity for the electrically-treated films was enhanced by two orders of magnitude compared with the as-deposited films and was twice as large as that of the heat-treated samples.

Second-Harmonic Generation in Oriented CdSe-Nanocrystal-Doped Indium Tin Oxide Film and its Application to an Infrared Detector

AbstractSecond-harmonic generation in CdSe nanocrystals doped in indium tin oxide ( ITO ) films has been examined. The thin film samples were prepared by r.f. magnetron sputtering with ITO target on which CdSe chips were placed. The X-ray diffraction patterns of as-deposited films indicate that CdSe crystallites are precipitated in an amorphous ITO matrix, and they are preferentially oriented in the direction of (111) plane of zinc blende structure or (002) plane of wurtzite structure. The mean diameter of CdSe crystallite was estimated to be 3-5 nm using Scherrer's equation. Moreover, the CdSe crystallites grew with keeping its initial orientation when a dc voltage of 50 V/cm was applied in the direction parallel to the film surface. The application of the electric field effectively enhanced the second-harmonic intensity by two orders of magnitude compared to that of the as-deposited films. The second-order nonlinear coefficient d(2) for the electrically-treated specimen calculated on a basis of a modified Maker fringe theory is d31 = 3.0 × 10 pm/V at the wavelength of 1064 nm, which is comparable to d values reported for CdSe single crystal, d31 = 25 pm/V at 1054 nm and d33 =76 pm/V at 1064 nm.