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[en] Indium tin oxide thin films were deposited at room temperature on glass substrates by RF magnetron sputtering. The structural, electrical and optical properties of the films showed a dependence on target to substrate spacing and annealing temperature. Films deposited with a target to substrate spacing of 4 cm showed the lowest resistivity of 3.07x10-3 Ω cm and maximum band gap of 3.89 eV on annealing at a temperature of 250 deg. C under high vacuum for 1 h
[en] Indium tin oxide (ITO) is one of the widely used transparent conductive oxides (TCO) for application as transparent electrode in thin film silicon solar cells or thin film transistors owing to its low resistivity and high transparency. Nevertheless, indium is a scarce and expensive element and ITO films require high deposition temperature to achieve good electrical and optical properties. On the other hand, although not competing as ITO, doped Zinc Oxide (ZnO) is a promising and cheaper alternative. Therefore, our strategy has been to deposit ITO and ZnO multicomponent thin films at room temperature by radiofrequency (RF) magnetron co-sputtering in order to achieve TCOs with reduced indium content. Thin films of the quaternary system Zn–In–Sn–O (ZITO) with improved electrical and optical properties have been achieved. The samples were deposited by applying different RF powers to ZnO target while keeping a constant RF power to ITO target. This led to ZITO films with zinc content ratio varying between 0 and 67%. The optical, electrical and morphological properties have been thoroughly studied. The film composition was analysed by X-ray Photoelectron Spectroscopy. The films with 17% zinc content ratio showed the lowest resistivity (6.6 × 10−4 Ω cm) and the highest transmittance (above 80% in the visible range). Though X-ray Diffraction studies showed amorphous nature for the films, using High Resolution Transmission Electron Microscopy we found that the microstructure of the films consisted of nanometric crystals embedded in a compact amorphous matrix. The effect of post deposition annealing on the films in both reducing and oxidizing atmospheres were studied. The changes were found to strongly depend on the zinc content ratio in the films.
[en] Indium tin oxide (ITO) thin films were deposited on glass substrates by RF magnetron sputtering. The influence of substrate temperature on the structural, electrical and optical properties was investigated. With increase in substrate temperature, the crystallinity of the films increased. The films exhibited (111) and (100) preferred orientations. All the films showed high transmittance (>85%) in the visible region. The band gap of the films increased with increase in substrate temperature. Films deposited with a substrate temperature of 150 degC showed the lowest resistivity of 2.1 x 10-3 Ωcm and highest mobility of 17.8 cm2V-1s-1. (author)
[en] Zinc indium tin oxide (ZITO) transparent conductive oxide layers were deposited via radio frequency (RF) magnetron co-sputtering at room temperature. A series of samples with gradually varying zinc content was investigated. The samples were characterized with x-ray and ultraviolet photoemission spectroscopy (XPS, UPS) to determine the electronic structure of the surface. Valence and conduction bands maxima (VBM, CBM), and work function were determined. The experiments indicate that increasing Zn content results in films with a higher defect rate at the surface leading to the formation of a degenerately doped surface layer if the Zn content surpasses ∼50%. Furthermore, the experiments demonstrate that ZITO is susceptible to ultraviolet light induced work function reduction, similar to what was earlier observed on ITO and TiO2 films.
[en] Epitaxial (111) Ba0.5Sr0.5TiO3 (BST) thin films have been grown by pulsed laser deposition on (0001) Al2O3 substrate with ZnO as buffer layer. The x-ray ω-2θ, Φ-scan and reciprocal space mapping indicate epitaxial nature of BST thin films. The domain matched epitaxial growth of BST thin films over ZnO buffer layer was confirmed using Fourier filtered high resolution transmission electron microscope images of the film-buffer interface. The incorporation of ZnO buffer layer effectively suppressed the lattice mismatch and promoted domain matched epitaxial growth of BST thin films. Coplanar inter digital capacitors fabricated on epitaxial (111) BST thin films show significantly improved tunable performance over polycrystalline thin films
[en] Indium tin oxide (ITO) thin films were deposited onto glass substrates by rf magnetron sputtering of ITO target and the influence of substrate temperature on the properties of the films were investigated. The structural characteristics showed a dependence on the oxygen partial pressure during sputtering. Oxygen deficient films showed (4 0 0) plane texturing while oxygen-incorporated films were preferentially oriented in the [1 1 1] direction. ITO films with low resistivity of 2.05 x 10-3 Ω cm were deposited at relatively low substrate temperature (150 deg. C) which shows highest figure of merit of 2.84 x 10-3 square/Ω
[en] Yb3+/Er3+ co-doped Y2O3, YOF and YF3 upconversion (UC) phosphors were synthesized by co-precipitation method. The three upconversion phosphor samples show strong green (540 nm) and red (660 nm) emission bands visible to naked eyes even at the low intense incident light. The potential application of Y2O3, YOF, and YF3 UC phosphors was demonstrated by incorporating them in amorphous silicon thin film solar cells and they showed upconversion current densities of 0.36 mA/cm2, 0.23 mA/cm2, and 0.207 mA/cm2 respectively when the cell was illuminated with a 980 nm IR laser. Intensity-dependent J-V studies were carried out to understand the effectiveness of UC phosphors in improving solar cell parameters. An improvement of 7.5% in Jsc was obtained for amorphous silicon solar cell incorporated with YF3 UC phosphors under AM1.5 along with 980 nm NIR illumination.
[en] A transparent and conducting ZnO:Er:Yb thin film with upconversion properties has been achieved after being annealed with continuous laser radiation just before the ablation point of the material. This work demonstrates that the laser energy preserves the conductivity of the film and at the same time creates an adequate surrounding for Er and Yb to produce visible upconversion at 660, 560, 520, and 480 nm under 980 nm laser excitation. The relation between the structural, electrical and upconversion properties is discussed. It is observed that the laser energy melts part of the material, which recrystallizes creating rare earth oxides and two different wurtzite structures, one with substitutional rare earths and oxygen vacancies (responsible for the conductivity) and the other without substitutional rare earth ions (responsible for the upconversion emission).