Effect of N<Subscript>2</Subscript> gas annealing and SiO<Subscript>2</Subscript> barrier on the optical transmittance and electrical resistivity of a transparent Sb-doped SnO<Subscript>2</Subscript> conducting film

During the fabrication process of transparent conducting thin films of ATO (antimony-doped tin oxide) on a soda lime glass substrate by a sol-gel dip coating method, the effects of the SiO₂ buffer layer formed on the substrate and N₂ annealing treatment were investigated quantitatively. The deposited ATO thin film was identified as a crystalline SnO₂ phase and the film thickness was about 100 nm/layer at a withdrawal speed of 50 mm/min. Optical transmittance and electrical resistivity of the 400 nm-thick ATO thin film that was deposited on SiO₂ buffer layer/soda lime glass and then annealed under nitrogen atmosphere were 84% and 5.0 × 10^–3cm, respectively. The XPS analysis confirmed that a SiO₂ buffer layer inhibited Na ion diffusion from the substrate, preventing the formation of a secondary phase such as Na₂SnO₃ and SnO and increasing Sb ion concentration and ratio of Sb⁵⁺/Sb³⁺ in the film. It was found that N₂ annealing treatment leads to the reduction of Sn⁴⁺ as well as Sb⁵⁺, however the reduction of Sn⁴⁺ is more effective, and consequently results in a decrease in the electrical resistivity to produce excellent electrical properties in the film. © Springer Science + Business Media, Inc.     

Preparation and electrical properties of ITO thin films by dip-coating process

Indium tin oxide (ITO) thin films were prepared on quartz glass substrates by a dip-coating process. The starting solution was prepared by mixing indium chloride dissolved in acetylacetone and tin chloride dissolved in ethanol. The ITO thin films containing 0 20 mol% SnO₂ were successfully prepared by heat-treatment at above 400 °C. Chemical stability of sol were investigated by using a FTIR spectrometer. The electrical resistivity of the thin films decreased with increasing heat-treatment temperature, that is carrier concentration increased, and mobility decreased with increasing SnO₂ content. The ITO thin films containing 12 mol% SnO₂ showed the minimum resistivity of =1.2 × 10^–3 ( cm). It also showed high carrier concentration of N=1.2 × 10²⁰(cm^–3) and mobility _H=7.0(cm² V^–1 s^–1).     

Deposition of improved optically selective conductive tin oxide films by spray pyrolysis

Antimony-doped SnO₂ films with a resistivity as low as 9×10^–4 cm were prepared by spray pyrolysis. Structural, electrical and optical properties were studied by varying the antimony concentration, film thickness and deposition temperature. About 94% average transmission in the visible region and about 87% infrared reflectance were obtained for antimony-doped SnO₂ films by a systematic optimization of the preparation parameters. As the best combination, an average transmission of 88% in the visible region and an infrared reflectance of 76% was possible for the doped SnO₂ films.     

Pyrosol deposition of fluorine-doped tin dioxide thin films

Fluorine-doped tin dioxide (SnO₂F) films were deposited from a tin tetrachloride solution in methanol utilizing a pyrosol deposition process. It is shown from thermodynamic calculations that the atmosphere during deposition is oxygen-rich and also suggested that chlorine and hydrogen chloride, which are produced during the deposition reaction, influence crystal growth. Detailed electrical, optical and structural properties of the material with respect to varying film thickness and substrate temperature are presented and discussed. Resistivity of the films deposited at 450 °C decreased from 6×10^–4 to 2×10^–4 cm, while the mobility increased from 14 to 45 cm²V^–1s^–1, respectively, when the film thickness was varied from 100 to 1650 nm. The carrier concentration was relatively unchanged for film thicknesses higher than 200 nm. Optimized SnO₂F films (600 nm) having a resistivity of 6×10^–4 cm, a carrier mobility of 20 cm²V^–1s^–1, a carrier concentration of 8×10²⁰ cm^–3 and a transmittance in excess of 80% are quite suitable as electrodes for amorphous silicon solar cells.     

Morphological study by XPS and AFM of wide band gap β-ln2S3 thin films synthesized by a dry physical process

Wide band gap -ln₂S₃ thin films have interesting properties to substitute CdS as the buffer layer in thin film solar cells. They have n-type conductivity and their optical band gap is about 2.8 eV. In this paper, -ln₂S₃ thin films deposited on smooth glass and on rough SnO₂-coated glass substrates have been morphologically studied by X-ray photoelectron spectroscopy (XPS) and by atomic force microscopy (AFM). The results obtained show that on each substrate the films are continuous without any pinholes and cracks. Films deposited on glass cover homogenously the whole surface of the substrate. In the case of SnO₂ substrates, the material deposited preferentially fills the hollows of the rough surface inducing a decrease of its roughness value. It is shown that these morphological properties are very promising for buffer layer application.     

Characterization of ZrO2 and SiC ceramic thin films prepared by electrostatic atomization

ZrO₂ and SiC ceramic thin films and their bilayer have been successfully prepared by a newly developed electrostatic atomization technique. This technique can generate fine spray of ceramic suspensions in a micrometer sized range with a narrow size distribution which is crucial for preparation of uniform thin films of these ceramic materials. Compared to some other thin film deposition techniques, such as Chemical vapour deposition (CVD), physical vapour deposition (PVD) and plasma spray (PS) etc. the thin film deposition process using electrostatic atomization is not only cheap but also controllable. The prepared ZrO₂ and SiC thin films were investigated using scanning electron microscopy (SEM) and energy dispersion analysis (EDA) techniques. These thin films were observed to be homogenous with a particle size less than 10 m. The ZrO₂-SiC bilayer was found to have an abrupt interface, implying that the deposition process is controllable and also that functionally graded ceramic/ceramic materials can be prepared in this way if the thickness of each layer is accurately controlled.     

A heterostructured SnO2–TiO2 thin film prepared by Langmuir–Blodgett technique

SnO₂–TiO₂ heterostructure films were prepared through Langmuir–Blodgett (LB) route. LB films of octadecyl amine (ODA)–titanyl oxalate multilayer deposited on Si (100) and decomposed at 600 °C showed rutile and anatase phases of ultrathin TiO₂ film. Subsequently, multilayer LB film of ODA–stannate deposited on the pre deposited TiO₂ film after decomposition at 600 °C resulted in thin SnO₂ films on the TiO₂ thin film. The phase analysis of the SnO₂–TiO₂ film showed cassiterite phase of SnO₂ as well as the rutile/anatase mixture of TiO₂ indicating a SnO₂–TiO₂ heterostructured film. Surface morphology of the pure TiO₂ film and SnO₂–TiO₂ film were analyzed by using AFM. Electrical characterization by AC impedance analysis suggested SnO₂–TiO₂ heterostructure formation. DC current voltage measurement showed increase in photocurrent indicating visible light absorption and efficient charge separation under the sunlight type radiation.     

Sensor Properties of Pd-Doped SnO2 Films Deposited by Laser Ablation

Polycrystalline SnO₂ and SnO₂ films were surface-doped with palladium using laser ablation. The effect of the energy density of pulsed KrF laser radiation on the plasma generation process and Pd deposition rate was studied, and the depth profiles of Pd in the films were determined. The gas response of the Pd/SnO₂, SnO₂, and Pd/SnO₂ films was studied between 200 and 380°C using a mixture of 1 vol % H₂ with N₂. Surface doping with Pd was found to enhance the hydrogen sensitivity of SnO₂ by two orders of magnitude.     

Hybrid nanocomposite based on cellulose and tin oxide: growth,structure, tensile and electrical characteristics

Abstract

A highly flexible nanocomposite was developed by coating a regenerated cellulose film with a thin layer of tin oxide (SnO₂) by liquid-phase deposition. Tin oxide was crystallized in solution and formed nanocrystal coatings on regenerated cellulose. The nanocrystalline layers did not exfoliate from cellulose. Transmission electron microscopy and energy dispersive x-ray spectroscopy suggest that SnO₂ was not only deposited over the cellulose surface, but also nucleated and grew inside the cellulose film. Current–voltage characteristics of the nanocomposite revealed that its electrical resistivity decreases with deposition time, with the lowest value obtained for 24 h of deposition. The cellulose–SnO₂ hybrid nanocomposite can be used for biodegradable and disposable chemical, humidity and biosensors.     

Characterization of lead zirconate titanate thin film deposition onto Pt/Ti/SiO2/Si substrates

Lead zirconate titanate, (Pb(Zr_0.52Ti_0.48)O₃PZT) thin films were deposited onto a Pt/Ti/SiO_2/Si substrate using radio frequency (r.f.) planar magnetron sputtering in this study. The deposited PZT thin films were almost amorphous before the annealing processes and developed a perovskite structure after the annealing process. If the annealing temperature was too low or annealing time too short, pyrochlore would form. However, if the annealing temperature was too high or annealing time too long, the thin film structure would degrade due to the volatilization of PbO. The significant finding in this experiment is that high quality perovskite PZT thin films on Pt/Ti/SiO_2/Si substrates can be obtained by adjusting the annealing temperature to a range of 650 °C to 850 °C and annealing time to a range from 5 to 80 min. In this experiment, the optimal annealing condition was an annealing temperature of 650 °C and time of 20 min. The properties of PZT thin film annealed at 650 °C for 20 min were dielectric constant _r = 869 free dielectric constant ^T ₃₃ = 893 piezoelectric constant d₃₃ = 2.03p m V^-1 piezoelectric constant g₃₃ = 2.57 x 10^-4 V m N^-1, remanent polarization P₁ = 112.5 nC cm^-2 and coercive field E_c= 0.061 kV cm^-1.     

Hybrid nanocomposite based on cellulose and tin oxide: growth,structure, tensile and electrical characteristics

A highly flexible nanocomposite was developed by coating a regenerated cellulose film with a thin layer of tin oxide (SnO₂) by liquid-phase deposition. Tin oxide was crystallized in solution and formed nanocrystal coatings on regenerated cellulose. The nanocrystalline layers did not exfoliate from cellulose. Transmission electron microscopy and energy dispersive x-ray spectroscopy suggest that SnO₂ was not only deposited over the cellulose surface, but also nucleated and grew inside the cellulose film. Current–voltage characteristics of the nanocomposite revealed that its electrical resistivity decreases with deposition time, with the lowest value obtained for 24 h of deposition. The cellulose–SnO₂ hybrid nanocomposite can be used for biodegradable and disposable chemical, humidity and biosensors.     

Metalorganic chemical vapor deposition of SrRuO3 thin film and its characterization

Synthesis of conducting oxide strontium ruthenate is carried out in a hot-wall tubular reactor, using Sr(C₁₁H₁₉O₂)₂/Ru(C₅H₅)₂/O₂ reaction system. Owing to a large difference in depositing efficiency between strontium and ruthenium precursors, the stoichiometric ratio of thin film is controlled in one cycle of two consecutive depositions at different temperatures. Thin films of SrRuO₃ single phase are synthesized in the subsequent 700°C annealing. Thin films of SrRuO₃ with extra ruthenium oxide can also be prepared by adjusting the molar ratio of RuO₂ and SrO layers. The deposition sequence of ruthenium oxide first, strontium oxide later is preferred. If the deposition sequence is reverse, the thin film is plagued with unreacted oxides even when the annealing temperature is raised to 800°C. The relative ease of preparing SrRuO₃ thin films, when RuO₂ is under SrO, is attributed to evaporation of ruthenium oxide in O₂ and diffusion in its open columnar microstructure. The sheet resistivity of thin film decreases with the ruthenium content. The room temperature resistivity of SrRuO₃ film of Ru/(Sr + Ru) = 0.5 is around 910 ohm-cm. The room-temperature resistivity of Ru/(Ru + Sr) = 0.53 decreases to 470 ohm-cm. The root mean square surface roughness of 700°C synthesized SrRuO₃ thin film is 22 nm, in a 2 × 2 m² area of film thickness 280 nm.     

Interaction of Pb and Sn with Thin Films of Their Oxides on Single-Crystal Silicon

Experimental data are presented on the interactions between Pb and thin SnO and SnO₂ films and between Sn and thin PbO films during vacuum annealing and subsequent heat treatment in flowing oxygen. The Pb and Sn films were deposited by magnetron sputtering onto single-crystal Si substrates; the SnO and SnO₂ films were produced by heat-treating Sn in flowing oxygen at 470 and 870 K, respectively; and the PbO films were obtained by heat-treating Pb films at 520 K. During annealing of Pb/SnO₂/Si heterostructures at 870 K in a vacuum of 0.33 × 10^–2 Pa, Pb reacts with lead oxides to form PbSnO₃, whereas vacuum annealing of Sn/PbO/Si heterostructures leads to the formation of SnO and Pb metal. The lead stannates forming in vacuum persist during subsequent heat treatment in flowing oxygen at atmospheric pressure at temperatures of up to 1120 K.     

The crystallographic properties of PbTiO3 thin films fabricated by chemical vapour deposition

Lead titanate, PbTiO₃, is a well-known material having remarkable ferroelectric, piezoelectric and pyroelectric properties. Thin films of lead titanate have been successfully fabricated by chemical vapour deposition on a titanium substrate. Layers deposited on the titanium substrate using PbO vapour and O₂ gas grow along the (1 0 1) preferred orientation. The maximum dielectric constant and loss tangent of PbTiO₃ thin film deposited on a titanium substrate are about 90 and 0.02, respectively. The electrical resistivity of the PbTiO₃ is about 10⁹cm. The deposition rates of PbTiO₃ deposited on the titanium substrate were 10 to 15 mh^–1. A titanium dioxide interlayer formed between the PbTi0₃ film and titanium substrate materials. It might improve the adhesion of the film.     

Electron microscopic study on the oxidation ofβ-tin irradiated by electron beam

Effects of electron beam irradiation to-tin thin foils have been studied using high-resolution electron microscopy. By the beam irradiation, the-tin crystal at the extreme-thin foil region disappear, and amorphous oxide films covering the-tin crystal are converted into SnO₂ micro-crystallites of about 5 to 10 nm in diameter. The present study also shows that the causes for the development of SnO₂ are not due to the increment in the temperature of amorphous and-tin regions resulting from the electron irradiation. It seems that the conversion into SnO₂ is caused by the ionization action of electron beam to atom species.     

Growth of cubic and hexagonal CdTe thin films by pulsed laser deposition

The paper reports the growth of cadmium telluride (CdTe) thin films by pulsed laser deposition (PLD) using excimer laser (KrF, λ=248 nm, 10 Hz) on corning 7059 glass and SnO₂-coated glass (SnO₂/glass) substrates at different substrate temperatures (T_s) and at different laser energy pulses. Single crystal target CdTe was used for deposition of thin films. With 30 min deposition time, 1.8- to ∼3-μm-thick films were obtained up to 200 °C substrate temperature. However, the film re-evaporates from the substrate surface at temperatures >275 °C. Atomic force microscopy (AFM) shows an average grain size ∼0.3 μm. X-ray diffraction analysis confirms the formation of CdTe cubic phase at all pulse energies except at 200 mJ. At 200 mJ laser energy, the films show hexagonal phase. Optical properties of CdTe were also investigated and the band gap of CdTe films were found as 1.54 eV for hexagonal phase and ∼1.6 eV for cubic phase.     

Characteristics of PbTiO3 thin films on Pt/Ti/SiO2/Si by continuous cooling process

In order to introduce a new deposition process for ferroelectric thin film, the deposition temperature was continuously cooled down from 580°C to 400°C during the deposition which we call continuous cooling process (CCP). X-ray diffraction patterns showed that the PbTiO₃ thin films deposited by the CCP and at 480°C had polycrystallinity, but at substrate temperatures of 400°C and 580°C had poor crystallinity. Scanning electron microscopy of the CCP-deposited film surface showed larger granular-like micrograins than that of the film deposited at 480°C and smaller than that of the film at 580°C. While there was no other phase formation at the PbTiO₃-Pt interface in the CCP-deposited film, resulting in a sharp interface, there was severe interface reaction at the PbTiO₃-Pt and the Pt-Si in the film deposited at 580°C, resulting in an abrupt interface. Atomic force microscopy under ambient conditions showed smoother surface of the film by the CCP than that of the films at 580°C. Furthermore, the film by the CCP had higher packing density than that of the film at 480°C. Besides enhancement of the structural properties, the CCP deposition appeared to have improved the electrical properties such as dielectric constant, dissipation factor, leak current density and polarization. In the case of the film by the CCP, polarization-electrical field measurement showed the saturation polarization of 27 Ccm^–2, remanent of 14 Ccm^–2 and coercive of 150 kV. These results indicate that the CCP in metalorganic chemical vapour deposition has a possibility for fabrication of PbTiO₃ ferroelectric thin films.     

Formation and characteristics of lead lanthanum zirconium titanate thin films formed by using the r.f. sputtering method

PLZT (lead lanthanum zirconium titanate) thin films were prepared by using the r.f. magnetron sputtering method and post-annealing for crystallization at 650 C. The films which were annealed at 650 C for 10 min consisted of a metastable phase and a stable phase. However, another film which was annealed at 650 C for 20 min had only stable perfect perovskite phase. The stability of the post-annealed thin film and substrate interfaces was observed by using scanning electron microscopy. The longer the annealing time, the more unstable were the interfaces. By analysing the EDX data, the composition difference between the sputtering target and thin films, and the composition variation between as-deposited and post-annealed PLZT were studied. The films annealed at 650 C for 20 min showed good ferroelectric and electrical properties with a remanent polarization (P _r) of 11.5 C cm^–2, and a coercive field (E _c) of 164 kV cm^–1.     

Preparation and characterization of radio-frequency-sputtered Ba2Si2TiO8 thin films

Radio-frequency-sputtered barium titanium silicate (BST, Ba₂Si₂TiO₈) thin films were grown on crystalline Si (100) substrates and were characterized using wavelength-dispersive spectrometry (WDS), X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM), and diagonal techniques for dielectric properties. The chemical compositions of the films increasingly deviated from stoichiometry with film thickness. At the initial stage of deposition the grain configuration is dependent on the Si substrate texture. XRD analysis indicates that the BST films deposited at an optimum substrate temperature of 845 °C were strongly c-axis oriented, and that the film orientation is manipulated by substrate temperature and supersaturation. The corresponding film-growth rate in the direction normal to the film surface at 845 °C was 1.95 nm min^–1 at the initial stage, and decreased with sputtering time. The as-deposited films have a room-temperature bulk resistivity of 1.8 ×10⁷ m in the direction of thickness and an isotropic surface resistivity of 1.5×10³ m. The high-frequency relative dielectric constant, 0.05 at frequencies higher than 9 MHz, is lower than that of many typical piezoelectric materials. The high-frequency impedance character is typical of piezoelectric materials, giving a minimum impedance frequency of 9.0 MHz and a serial resonant frequency at about 9.5 MHz.