Nanocrystalline ITO Research Articles

Investigation of physical properties and surface free energy of produced ITO thin films by TVA technique

In this study, tin-doped indium oxide (ITO) thin films with composition of 10% SnO2 and 90% In2O3 have been produced onto glass, polyethylene terephthalate (PET) and Silicon (Si) substrates by using thermionic vacuum arc technique. The properties of the ITO thin films were determined various tolls such as an X-ray diffraction (XRD), ultraviolet–visible (UV–Vis) spectrophotometer, optical reflectometer, field emission electron microscopy (FESEM), atomic force microscopy, four-point probe and contact angle (CA) measurements devices. According to the XRD patterns, deposited thin films onto glass, PET and Si substrate are in amorphous structure. The thicknesses of the deposited layers are very close to each other’s and films. The transmittance values are approximately 30% at 632 nm. Refractive index of the deposited layers are close to 1.75, but optical band gaps are found 3.88 and 3.81 eV for the thin film deposited onto glass and PET substrate, respectively. These values are bigger than the value of the band gap value of the ITO material. In surface analysis, it was found that crystallite dimensions are in nano-scales. According to surface analysis, nano-crystalline ITO thin films were deposited. The contact angle of the coated ITO layer were measured in the range of 98°–110°. The electrical resistivity of films was calculated about 0.65 × 10−5 Ω cm for ITO/glass, 1.05 × 10−5 Ω cm for ITO/PET and 5.82 × 10−5 Ω cm for ITO/Si.

Effect of Different Doping Concentrations and Its Characterizations of Nanocrystalline ITO Nano Particles

Nanocrystalline ITO particles are prepared by Combustion Synthesis. Similarly, the structural and morphological properties for as prepared different ratio of powders to be 9:1 and 5:5 were found. Thermogravimetry analysis shows the liberation of O, H, N and metal particles with respective temperatures and loss of weight in mg. The structural, optical grain boundary and electrical studies due to variation of theoretical mobility’s with SEM analysis were discussed. The lattice constants were found to be 10.09 and 10.16 Å for different composition of powders. Here we present the preparation, Thermo gravimetric (TGA) analysis, structural studies, and morphological properties of ITO synthesized by decomposition of ITO by Sol-gel method.

Preparation and characterization of epitaxial growth of ZnO nanotip arrays by hydrothermal method

Preparation and characterization of epitaxial growth of ZnO nanotip arrays are essential for field emission applications due to its high emission rate of electron and fast electron-transfer rate. At first, nanocrystalline ITO thin films were prepared on glass substrates by ion-beam sputter deposition (IBSD) method. ZnO seed layer was prepared on the ITO coated glass substrates by IBSD at room temperature, and then, ZnO nanotip arrays were epitaxially grown on the as-prepared ZnO seed layer coated ITO/Glass substrates by hydrothermal method. The surface morphology study confirmed that the ZnO nanotip array films were epitaxially grown on ITO/Glass substrates, and it clearly showed the formation of well-aligned ZnO nanotip arrays on ITO/Glass substrate. The as-prepared samples were annealed at different temperatures (100, 150 and 270°C). After annealing, the surface morphology of ZnO nanotip arrays did not show any remarkable change. X-ray diffraction pattern of ZnO nanotip array films prepared on ITO/Glass showed a main peak at 2θ=34.3°, which corresponds to (002) plane. The photoluminescence spectra showed the strong intensity of UV emission and weak intensity of green emission. The J–V characteristic of Ag/NPB/PMMA/ZnO/ITO showed good rectification behavior.

Solid state sintering of nano-crystalline indium tin oxide

Abstract The sintering of single phase nano-crystalline In2O3 and ITO (In1.9Sn0.1O3.05) powders is reported and discussed with particular focus on the underlying mass transport mechanisms. The mass transport in the initial stage of sintering was surface diffusion, resulting in necking and coarsening, and grain boundary diffusion, accompanied by grain growth. Lattice diffusion caused significant densification at higher temperatures, leading to densities higher than 95%. The onset of densification and the maximum densification rate were shifted significantly to higher temperatures for ITO compared to In2O3. The reduced sintering rate of ITO was related to the higher valence state of Sn4+ relative to In3+, and due to precipitation of SnO2(s). The volatile sub-oxides In2O(g) and SnO(g) caused significant weight losses at high temperatures, particularly in the case of ITO and inert conditions. The sintering at intermediate temperatures is discussed with focus on heat treatment of ITO thin films.

Memory Functions of Nanocrystalline ITO Embedded Zirconium-Doped Hafnium Oxide High-k Capacitor with ITO Gate

Memory functions of MOS capacitors with the nanocrystalline ITO embedded zirconium-doped hafnium oxide high-k gate dielectric thin film and the ITO gate electrode have been studied. Compared with the capacitor of the same dielectric stack but an aluminum gate, the ITO gated sample has a larger charge storing density. The primary memory mechanism of this device is based on hole injection and trapping to the embedded nanocrystalline ITO layer supplied from the substrate under a negative gate bias condition. The large work function of the ITO gate makes it difficult to transfer electrons from the gate to the embedded nanocrystalline ITO site, which favors the hole storage. Under the positive gate bias condition, all positive charges stored in the ITO gated capacitor are erased while those stored in the aluminum gated capacitor are partially erased.

Deposition and optoelectronic properties of ITO (In2O3:Sn) thin films by Jet nebulizer spray (JNS) pyrolysis technique

Nanocrystalline ITO thin films were deposited on glass substrates by a new spray pyrolysis route, Jet nebulizer spray (JNS) pyrolysis technique, for the first time at different substrate temperatures varying from 350 to 450 °C using a precursor containing indium and tin solution with 90:10 at% concentration. The structural, optical and electrical properties have been investigated as a function of temperature. X-ray diffraction analysis showed that the deposited films were well crystallized and polycrystalline with cubic structure having (222) preferred orientation. The optical band gap values calculated from the transmittance spectra of all the ITO films showed a blue shift of the absorbance edge from 3.60 to 3.76 eV revealing the presence of nanocrystalline particles. AFM analysis showed uniform surface morphology with very low surface roughness values. XPS results showed the formation of ITO films with In3+ and Sn4+ states. TEM results showed the nanocrystalline nature with grain size about 12-15 nm and SAED pattern confirmed cubic structure of the ITO films. The electrical parameters like the resistivity, mobility and carrier concentration are found as 1.82 × 10−3 Ω cm, 8.94 cm2/Vs and 4.72 × 1020 cm−3, respectively for ITO film deposited at 400 °C. These results show that the ITO films, prepared using the new JNS pyrolysis technique, have the device quality optoelectronic properties when deposited under the proposed conditions at 400 °C.

Temperature Effects on Charge Transfer Mechanisms of nc-ITO Embedded ZrHfO High-k Nonvolatile Memory Devices

ABSTRACTThe nanocrystalline ITO embedded Zr-doped HfO2 high-k dielectric thin film has been made into MOS capacitors for nonvolatile memory studies. The devices showed large charge storage densities, large memory windows, and long charge retention times. In this paper, authors investigated the temperature effect on the charge transport and reliability of this kind of device in the range of 25°C to 125°C. The memory window increased with the increase of the temperature. The temperature influenced the trap and detrap of not only the deeply-trapped but also the loosely-trapped charges. The device lost its charge retention capability with the increase of the temperature. The Schottky emission relationship fitted the device in the positive gate voltage region. However, the Frenkel-Poole mechanism was suitable in the negative gate voltage region.

Microstructure analysis of sol‐gel‐derived nanocrystalline ITO thin films

AbstractThe technique for ITO (Tin‐doped indium oxide) thin films by sol‐gel process is presented in this paper. After annealing at 500° for 15 min, ITO gel films get transformed into nanocrystallined indium tin oxide films. We studied the microstructure of ITO thin film which is closely related to optical and electrical properties. The microstructure of ITO thin film can be observed through high‐resolution transmission electronic spectroscopy (HRTEM) and the Fast Fourier Transform (FFT) technique. The film is nanocrystallite with grain sizes about 20 nm. Also, the surface chemical components were studied by XPS spectra. The transmission and the resistivity of ITO films is 97.0% and 3.5 × 10−3 Ω•cm, respectively. Copyright © 2010 John Wiley & Sons, Ltd.

(Invited) Performance and Reliability of Nanocrystals Embedded High-k Nonvolatile Memories

The nanocrystals embedded high-k dielectric structure is promising for the high-density nonvolatile memories. In this paper, the author discussed the performance and reliability of MOS capacitors composed of various nanocrystalline ITO, ZnO, and RuO embedded zirconium doped HfO2 high-k dielectrics. This kind of device is easily fabricated with thin film deposition methods. Material properties of the embedded nanocrystals are critical to device's memory functions and reliability, such as the charge trapping characteristics and the breakdown mechanism.

Stress-Induced Deterioration of Nanocrystalline ITO Embedded ZrHfO High-k Nonvolatile Memories

The stress-induced deterioration phenomenon of the nc-ITO embedded Zr-doped HfO2 high-k gate dielectric film has been studied. The deterioration process is detectable from the decrease of the capacitance in the accumulation region and the shift of flatband voltage as well as the change of the amount of induced charges. In addition, the relaxation current and Coulomb blockage effect are influenced by the stress-induced process. Moreover, the nc-ITO embedded high-k capacitor shows the trap-assisted tunneling phenomenon and the Poole-Frenkel emission mechanism.

Influence of RF power on the growth mechanism, preferential orientation and optoelectronic properties of nanocrystalline ITO films

Nanocrystalline ITO thin films were deposited by the RF sputtering technique using various RF power values keeping the substrates at room temperature. An indepth study of the influence of RF power on the preferential orientation, optical, electrical and surface morphological properties was conducted by varying the RF power from 50 W to a maximum of 350 W. X-ray diffraction results confirmed the formation of nanocrystalline ITO films at all RF power values. At 250 W, the ITO films showed preferential orientation along (400) plane. Below and above this power, the films showed (222) orientation. It was observed from the optical transmittance studies that the bandgap value increased from 3.55 to 3.70 eV when the RF power was varied from 50 to 250 W. The resistivity value showed a minimum of 4.2 × 10 −3 Ω cm and the grain size reached a maximum of 125 nm for the ITO film deposited at 250 W. The XPS, EDAX and AFM results revealed the formation of stoichiometric and smooth ITO films, which contained nano-sized grains distributed uniformly all over the surface. These results show that the nanocrystalline ITO films deposited with 250 W RF power under the optimized conditions at room temperature, have the required optoelectronic and surface morphological properties useful for the fabrication of devices at a relatively lower temperature.

Stress-Induced Deterioration of Nanocrystalline ITO Embedded ZrHfO High-k Nonvolatile Memories

not Available.

Catalytic water oxidation on derivatized nanoITO

Electrocatalytic water oxidation occurs on high surface area, nanocrystalline ITO (nanoITO) surface-derivatized by phosphonate-binding of the catalyst [Ru(Mebimpy)(4,4'-((HO)(2)OPCH(2))(2)bpy)(OH(2))](2+) (Mebimpy is 2,6-bis(1-methylbenzimidazol-2-yl)pyridine; bpy is 2,2'-bipyridine). With nanoITO, spectral data can be acquired on electrochemically generated intermediates and voltammograms monitored spectrophotometrically.

Effect of Ag addition on the structural and electrical properties of ITO powder compact

Nanocrystalline ITO-Ag powders were prepared using a coprecipitation method. Surface modified silver nanoparticles were mixed with the indium tin hydroxide precursor before the sintering process. The ITO-Ag nanocomposite powder was formed into pellets by uniaxial pressing process. The effect of addition of silver to the electrical and structural properties of ITO powder compact was studied. The relative density of the metal filled composite ITO-Ag powder compact is higher than the pure ITO powder compact. The result may be attributed to the melted silver eventually fills the void space between agglomerate pores and hence enhances the interconnection between nanocrystalline ITO powders. The crystal phase and particle size of ITO powder and ITO-Ag powder were measured by powder X-ray diffraction and the surface morphology of powder compact was investigated using a scanning electron microscope.

Single and Dual nc-ITO and nc-ZnO Embedded ZrHfO High-k Nonvolatile Memories

MOS capacitors containing singe and dual nanocrystalline ITO and ZnO embedded in the Zr-doped HfO2 high-k gate dielectric were fabricated and characterized for nonvolatile memory functions. The nc-ITO and nc-ZnO embedded devices show mainly hole and electron trapping characteristics, respectively. The dual-layer nc-ITO and nc-ZnO embedded capacitors have more than double charge trapping capacities and faster charge rates than the single-layer embedded capacitors.

Characterization of Structural Change of Nano-crystalline ITO Films due to Exposure to Hyperthermal Atomic Oxygen

Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois, USA, July 30 – August 3, 2006

CO Gas Sensing Characteristics of ITO Electrode Coupled with Sc2O3-ZrO2 Solid Electrolyte

Tin-doped indium oxide (ITO) is an important industrial material, which was extensively studied as an electrode material for optoelectronic devices and semiconductor gas sensors. However, its application as an oxide electrode material in mixed-potential gas sensor has not been explored so far. In this report, the sensing properties of the planar scandia-stabilized zirconia based mixed potential gas sensor coupled with hydrothermally-obtained nano-sized ITO as an electrode material have been investigated. The planar sensor has shown good sensitivity to low-level of CO concentrations (16~500ppm) in a lower oxygen ambient (4 vol.%) in terms of the high magnitude of the signal and fast response (<5s). A possible sensing mechanism of the planar sensor for rapidly detecting CO has also been discussed. The fast response feature of the fabricated sensor could be attributed to the porous nanocrystalline ITO employed as a thick film electrode in the CO sensor.

Degradation of Nano-crystalline ITO Films due to Exposure to Hyperthermal Atomic Oxygen

ABSTRACTIndium tin oxide (ITO) films coated on float glass slides were exposed to 5 eV hyperthermal atomic oxygen at room temperature with increasing fluences: 2×1019, 6×1019 and 2×1020 O-atoms/cm2. We characterized the structure of the ITO films after room temperature atomic oxygen exposure with scanning electron microscope (SEM) and atomic force microscope (AFM), synchrotron X-ray diffraction (XRD), and cross-sectional transmission electron microscope (X-TEM). The unexposed ITO films were found to possess a nano-crystalline surface, and clean and abrupt ITO/SiO2 interfaces without interfacial phase. Surface roughness of the exposed ITO films increased with the increasing AO influences. The interface- sensitive peaks in XRD measurements with grazing incidence revealed that the crystallinity of the ITO was modified near the interface. Cross-sectional TEM confirmed that many ITO particles with diameters ranging from 2-10 nm formed in the SiO2 substrate near the interface after AO exposure. These findings suggest that O atoms can travel through the ITO films, where the boundaries of columnar-grown grains may supply the pathway.

Gas Sensing Properties of Nanocrystalline ITO Thick Films with Different Particle Sizes

Nano-sized materials, have much bigger surface-bulk ratio than coarse materials. Thus, surface properties become paramount, which makes these materials particularly appealing in applications in which such properties are exploited, as in gas sensors. The purpose of this work is that investigates the gas sensing characteristics of the nanocrystalline ITO thick films with various particle sizes. At first, we synthesized nano-sized ITO powders with particle size of 15, 30 and 70nm in an equivalent diameter via coprecipitation method. And then, the sensitivity of ITO thick films was measuresd for ethanol(C2H5OH) as target gas and some Volatile Organic Compounds(VOCs) such as Toluene, Methanol, Benzene, Chloroform. XRD, BET, TEM, SEM, XPS were used to investigated characteristics of ITO powders and thick films.

P‐41: Novel Fabricating Process for Nanocrystalline Indium Tin Oxide Thin Film for Flexible Substrate by Low‐temperature One‐time Mixing and Oxidation LOMO

AbstractNanocrystalline indium‐tin‐oxide particles were successfully synthesized with the help of newly developed low‐temperature one‐time mixing and oxidation LOMO method. The process temperature did not exceed 300°C by the exclusion of chloride ions from the synthetic materials. The synthesized nanocrystalline particles showed the ultrafine size below 3 nm and ultrahigh specific surface area above 117 m2/g. Also, using the particles and ITO sol, nanocrystalline ITO thin film could be successfully fabricated with good optical transmittance over 83%.