Doped ITO Research Articles

Structural, Optical, and Sensing Properties of Nb-Doped ITO Thin Films Deposited by the Sol-Gel Method.

The aim of the present study was the development of Nb-doped ITO thin films for carbon monoxide (CO) sensing applications. The detection of CO is imperious because of its high toxicity, with long-term exposure having a negative impact on human health. Using a feasible sol-gel method, the doped ITO thin films were prepared at room temperature and deposited onto various substrates (Si, SiO2/glass, and glass). The structural, morphological, and optical characterization was performed by the following techniques: X-ray diffractometry (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV/Vis/NIR spectroscopic ellipsometry (SE). The analysis revealed a crystalline structure and a low surface roughness of the doped ITO-based thin films. XTEM analysis (cross-sectional transmission electron microscopy) showed that the film has crystallites of the order of 5-10 nm and relatively large pores (around 3-5 nm in diameter). A transmittance value of 80% in the visible region and an optical band-gap energy of around 3.7 eV were found for dip-coated ITO/Nb films on SiO2/glass and glass supports. The EDX measurements proved the presence of Nb in the ITO film in a molar ratio of 3.7%, close to the intended one (4%). Gas testing measurements were carried out on the ITO undoped and doped thin films deposited on glass substrate. The presence of Nb in the ITO matrix increases the electrical signal and the sensitivity to CO detection, leading to the highest response for 2000 ppm CO concentration at working temperature of 300 °C.

Analysis characteristic of cholesteryl acrylate conductivity with the addition of the PE-b-PEG doped ITO-nanoparticle in the development of liquid crystal technology

The study of liquid crystal material is very interesting and has the opportunity as a smart material such as cholesteryl acrylate. Liquid crystal cholesteryl acrylate can be made shynthesized by Acryloiloxy Butyloxy Benzoate (ABB) precursor and cholesterol. Cholesteryl acrylate was polymerized by the ultraviolet curing (UV-Curing) method to keep the crystal structure stable. During the polymerization process some ingredients are added which can increase and regulate the formation of liquid crystal structure phases. Cholesteryl acrylate can be doped by adding conductive oxide in the form of nano particle scale Indium Tin Oxide (18 nm). The optimum conductivity results were 5.70 × 10−7 S/m with the addition of ITO 10% w/w. The structure of the crystal phase formed can be directed by the addition of Polyethylene-block-Polyethylene Glycol during the UV-Curing process. The hydrophobic part of PE block will interact with hydrophobic liquid crystal molecules, while the hydrophilic part of the PEG block has a high affinity for the hydrophilic ITO electrode substrate. The added PE-b-PEG varies from 0.001 to 0.005 percent by weight of polymer cholesteryl acrylate composite. Conductance data is measured using LCR meters from a frequency of 50 Hertz to 5000 kHertz. The average conductance data for ITO is 0.09597838 S, cholesteryl acrylate is 5.20635 × 10−6 S, the polymer cholesteryl acrylate composite with doped ITO is 4.58284 × 10−6 S. When added PE-b-PEG 0,003 percent composite weight is obtained the highest average conductance data is 1.24234 × 10−5 S with an average conductivity value of 6.09 × 10−5 S/m. The varies composition of PE-b-PEG content is very influential to regulate the arrangement of crystals formed in electrical conductivity.

Room temperature ferromagnetism and crossover of negative magnetoresistance to positive magnetoresistance in the Co doped ITO films

The effects of Co doping on tuning optical, magnetic and transport properties of ITO films prepared by magnetron sputtering technique were investigated systematically by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–Vis, Hall effect, ρ-T, magnetoresistance (MR) and magnetic measurements. The detailed structural analyses reveal that the Co-doped ITO films have cubic bixbyite structure of space group Ia3‾ and Co dopant atoms are substitutionally incorporated into In2O3 lattice with the high spin divalent state of Co2+. The Co-doped ITO films display clear room-temperature (RT) ferromagnetism and Mott variable range hopping (VRH) transport behavior with n-type conductivity. The saturated magnetization (Ms) decreases from 4.52 emu/cm3 to 2.2 emu/cm3 with increasing Co concentration from 3.7 at% to 6.5 at%. Crossover of negative MR to positive MR and the red shift of optical bandgap Eg are also observed with Co doping, reflecting the occurrence of spin polarization and stronger s-d exchange interaction. The observed RT ferromagnetism of the films can consider being due to the Co2+-vacancy complexes induced magnetic interaction by the overlapping of bound magnetic polarons. The Co doping can cause the variation of localization effect of carrier, which remarkably influences the ferromagnetic order of the Co-doped ITO films.

Magnetic, optical and electrical properties of ITO thin films implanted by cobalt ions

The Co doped ITO samples are prepared by Co ions implanted ITO thin films. The implantation dosage of Co ions is 5 × 1015, 1 × 1016, 2 × 1016 cm−2, respectively. Then the samples are annealed by rapid thermal annealing in vacuum. The structure of the samples is characterized by glancing angle X-ray diffraction and high resolution transmission electron microscopy. The observed dislocation causes the lattice distortion and the interplanar distance becomes larger. The carrier density gradually decreases as the Co ions dosage increases. The optical and electrical properties of the samples are affected by the carrier density. The gradually reduced band gap can be explained by Burnstein-Moss effect. Though the electrical and optical properties are deteriorated after Co implanted ITO thin films, the strength of ferromagnetism enhances as the dosage of Co ions increase.

Relation Between Sputtering Parameters and Optical and Electrical Properties of Ga Doped ITO Transparent Conductive Oxide

A ceramic target with Ga:In:Sn=4:64:32 metal ratio has been sintered and used for RF sputtering process to develop high quality Ga doped ITO (GITO) transparent conductive oxide layers, particularly for photovoltaic applications. The sputtering parameters (sputtering power, oxygen flow, and substrate temperature) have been varied first and optimized with respect to the resistivity measurements. The layers deposited under optimized conditions were then post-annealed at different temperatures (200 – 500°C) either in the air or in nitrogen atmosphere in order to further improve the conductivity. The deposited 200nm thick GITO layer has high electron mobility (50 cm2/Vs) at relatively low resistivity (0.90mΩcm) although the free electron concentration is kept low (1.4×1020 cm-3) to prevent excessive free-carrier absorption. Thus, high transmission of the layer (∼80% at 400 – 1500nm) is obtained.

Ultrabroadband terahertz conductivity of highly doped ZnO and ITO

The broadband complex conductivities of transparent conducting oxides (TCO), namely aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO) and tin-doped indium oxide (ITO), were investigated by terahertz time domain spectroscopy (THz-TDS) in the frequency range from 0.5 to 18 THz using air plasma techniques, supplemented by the photoconductive antenna (PCA) method. The complex conductivities were accurately calculated using a thin film extraction algorithm and analyzed in terms of the Drude conductivity model. All the measured TCOs have a scattering time below 15 fs. We find that a phonon response must be included in the description of the broadband properties of AZO and GZO for an accurate extraction of the scattering time in these materials, which is strongly influenced by the zinc oxide phonon resonance tail even in the low frequency part of the spectrum. The conductivity of AZO is found to be more thickness dependent than GZO and ITO, indicating high importance of the surface states for electron dynamics in AZO. Finally, we measure the transmittance of the TCO films from 10 to 200 THz with Fourier transform infrared spectroscopy (FTIR) measurements, thus closing the gap between THz-TDS measurements (0.5-18 THz) and ellipsometry measurements (200-1000 THz).

Effect of Substrate Temperature on the Opto-Electrical Propertites of Ti Doped ITO Films Deposited by RF Magnetron Sputtering

Ti doped ITO (ITO:Ti) thin films were fabricated on glass substrates by RF magnetron sputtering using only one piece of ITO:Ti ceramic target at different substrate temperature (Ts). The effect of substrate temperature on structural, electrical, and optical properties of the films was investigated. It is confirmed that the resistivity of the films decreases with the increase of Ts till the minimum value of 2.5×10-4 Ω•cm and the transmittance in visible wavelengths is higher than 90%. "Blue shift" and "red shift" of UV absorption edge of the film were observed when Ts200 °CHeaders and footers

Stability of indium–tin-oxide and its optical properties: A first-principles study

Various doping sites of Sn in the In2O3 system have been modeled and simulated by the first-principles. The energy favorable site of Sn in In2O3 is found to be on the b-site, which is consistent with experiments. The doping of Sn into interstitial sites is experimentally possible due to the fluctuation in energy, and the intrinsic oxygen vacancies in In2O3 favor the formation of Sni. As Sni in doped ITO can drastically change the transparency in the visible light range, it is necessary to control the preparatory conditions to avoid Sn doping in interstitial sites for realizing ideal transparency in visible light range. By using the LDA+U approach, the band structures of In2−xSnxO3 (x≤0.125) are calculated, which are in substantially better agreement with the experimental values than previous first-principles results.

Effect of Sn Doping on the Crystal Growth of Indium Oxide Films

Heteroepitaxial growth of tin-doped indium oxide (ITO) and non-doped indium oxide (IO) thin films was carried out on single-crystal yttria-stabilized zirconia substrates by molecular beam epitaxy. The surface morphology of these epitaxial films was characterized by scanning electron microscopy. The doped ITO and non doped IO epitaxial films showed drastic changes in surface morphology, which suggested that Sn acted not only as a dopant but also as a growth modifier for IO films. The surface morphology analysis of IO and ITO films revealed a growth rate enhancement by Sn doping along the <111> direction.

Structural Studies of Tin-Doped Indium Oxide (ITO) and In4Sn3O12

Structural changes in the indium oxide lattice due to doping with Sn4+(ITO) were studied by Mössbauer spectroscopy, EXAFS, and neutron powder diffraction. There is a decrease in electrical conductivity as the tin content and oxygen partial pressure increase, which is related to a distortion in the first Sn–O shell. Doping with tin increases the oxygen/cation ratio and the lattice parameter and decreases the Sn–O distances, which disorders the host network. The low-conduction In4Sn3O12phase precipitates when the tin content exceeds 6 at.%. In4Sn3O12is rhombohedral (space groupR3,a=9.4604(2) Å, andc= 8.8584(2) Å in a hexagonal basis). There is a cation ordering with octahedral sites fully occupied by tin, the tin sites being equivalent in both highly doped ITO and In4Sn3O12.

Transparent conducting films

We present here a new technique, called vapour phase spray pyrolysis, for deposition ofto andito films. Undopedto film showed semiconducting nature, a sheet resistance of 1088 Ω/□, a donor ionization energy level of 40 meV, average visible transmittance of 75·4% andn-type conductivity. The indium doped (ito) film 10 wt % showed metallic nature, a sheet resistance of 15 Ω/□, average visible transmittance of 80·4 % andp-type conductivity. Thus theto andito films showed fairly good electro-optical qualities, comparable to those obtained by sophisticated and costly techniques.