Effect of heat-treatment on LaNiO3 film electrode of PZT thin films derived by a sol–gel method

Lanthanum nickel oxide (LaNiO₃ or LNO) conducting thin films that could be used as electrodes for improving fatigue and aging properties of ferroelectric thin films were investigated. In this paper, LNO films were directly spin-coated onto SiO₂/Si(1 0 0) substrates followed by thermal treatment in air and in oxygen. It was found that crack-free dense and uniform films with good crystallinity and medium grains were obtained, preferentially (1 0 0)-oriented LNO thin films could be formed at a lower annealing temperature of 550 °C and that with the increase in thermal annealing temperature the LNO thin film possessed better electrical properties especially at 750 °C. However, the LNO film displayed a structure transformation above 850 °C. A phenomenon was found that the first heat-treatment temperature and time played a key role to determine the crystallite size of LNO films. A subsequent deposition of a sol–gel derived Pb(Zr_0.53Ti_0.47)O₃ (PZT53/47) thin film on the LNO-coated SiO₂/Si(1 0 0) substrates was also found to have a (1 0 0)-oriented texture. Moreover, the Au/PZT/LNO capacitor was found to significantly improve the fatigue and the effects of the LNO electrodes to the fatigue were discussed.     

Structural and electrical properties of RuO2 thin films prepared by rf-magnetron sputtering and annealing at different temperatures

Conductive ruthenium oxide (RuO₂) thin films have been deposited at different substrate temperatures on various substrates by radio-frequency (rf) magnetron sputtering and were later annealed at different temperatures. The thickness of the films ranges from 50 to 700 nm. Films deposited at higher temperatures show larger grain size (about 140 nm) with (200) preferred orientation. Films deposited at lower substrate temperature have smaller grains (about 55 nm) with (110) preferred orientation. The electrical resistivity decreases slightly with increasing film thickness but is more influenced by the deposition and annealing temperature. Maximum resistivity is 861 μΩ cm, observed for films deposited at room temperature on glass substrates. Minimum resistivity is 40 μΩ cm observed for a thin film (50 nm) deposited at 540°C on a quartz substrate. Micro-Raman investigations indicate that strain-free well-crystallized thin films are deposited on oxidized Si substrates.     

Influence of the annealing in nitrogen atmosphere on the XRD, EDX, SEM and electrical properties of chemical bath deposited CdSe thin films

The influence of annealing in nitrogen atmosphere on the structure, optical and electrical properties of cadmium selenide (CdSe) thin films deposited by chemical bath deposition (CBD) onto glass substrates was studied. The samples were annealed in nitrogen atmosphere at various temperatures. A transition from metastable nanocrystalline cubic to stable polycrystalline hexagonal phase has been observed after annealing. The as-deposited CdSe thin films grow in the nanocrystalline cubic phase with optical band gap 1.93 eV. The electrical resistivity of the thin films has been measured in order of 10⁶ Ω cm. The activation energy of the samples has been found to be 0.26–0.19 eV at low temperature region, and 0.36–0.56 eV at high temperature region. It was also found that the activation energy and the resistivity of the films decrease with the increasing annealing temperature.     

Electrical and optical properties of annealed gallium arsenide thin films on glass substrates

The effects of annealing in vacuum on the electrical and optical properties of GaAs thin films deposited by the flash evaporation method were studied. Thin films of compound GaAs deposited upon glass substrates at room temperature were annealed in a vacuum of 2×10^–6 torr at different temperatures up to 350° C. The properties of the films depended strongly on annealing temperature. The lowest resistivity measured was about 1.6 × 10⁴ cm at an annealing temperature of about 240° C. The activation energy of as-deposited and annealed films were measured and compared. Optical absorption measurements of the asdeposited samples and the samples annealed at a temperature of 240° C were made as a function of photon energy.     

Effect of heat-treatment on LaNiO3 film electrode of PZT thin films derived by a sol–gel method

Lanthanum nickel oxide (LaNiO₃ or LNO) conducting thin films that could be used as electrodes for improving fatigue and aging properties of ferroelectric thin films were investigated. In this paper, LNO films were directly spin-coated onto SiO₂/Si(1 0 0) substrates followed by thermal treatment in air and in oxygen. It was found that crack-free dense and uniform films with good crystallinity and medium grains were obtained, preferentially (1 0 0)-oriented LNO thin films could be formed at a lower annealing temperature of 550 °C and that with the increase in thermal annealing temperature the LNO thin film possessed better electrical properties especially at 750 °C. However, the LNO film displayed a structure transformation above 850 °C. A phenomenon was found that the first heat-treatment temperature and time played a key role to determine the crystallite size of LNO films. A subsequent deposition of a sol–gel derived Pb(Zr_0.53Ti_0.47)O₃ (PZT53/47) thin film on the LNO-coated SiO₂/Si(1 0 0) substrates was also found to have a (1 0 0)-oriented texture. Moreover, the Au/PZT/LNO capacitor was found to significantly improve the fatigue and the effects of the LNO electrodes to the fatigue were discussed.     

Electrical properties of thin metal zinc films

Thin metal zinc films 40 to 200 nm thick are deposited by thermal evaporation at room temperature onto glass substrates with a deposition rate of 0.2 to 0.7 nm sec^–1. The electrical resistivity is measured as a function of film thickness, deposition rate and annealing temperature. The experimental results show that electrical resistivity decreases as the film thickness, deposition rate and annealing temperature increase, while the temperature coefficient of resistivity increases with the increase in the film thickness. The calculated values of the activation energy for the conduction electrons increases as the film thickness and deposition rate increase. The well known Fuchs-Sondheimer model is applied for zinc films. The theoretically calculated values for the electrical resistivity and the temperature coefficient of resistivity are in good agreement with the experimental results.     

Thickness dependence of H2 gas sensor in amorphous SnQx films prepared by ion-beam sputtering

Amorphous SnO_x films were deposited by ion-beam sputtering on sintered alumina substrates. Amorphous film sensors were prepared by annealing the films at 300° C for 2 h in air. The thickness dependence of resistivity and hydrogen gas sensitivity were measured at 150° C over the thickness range 1 to 700 nm. A resistivity maximum was observed in ultrathin films. Resistivity increased by three orders of magnitude with increasing film thickness from 0.9 to 7.4 nm and then decreased by five orders of magnitude from 7.4 to 35 nm. Ultrathin film sensors showed sensitivity maxima around a thickness of 10 nm. Sensitivity and resistivity of ultrathin films were significantly influenced by the thermal expansion coefficient and the surface state of the substrate.     

Effects of temperature on the resistivity of vacuum deposited Cu-MgF2 cermet thin films: an investigation of conduction mechanism

Cermet thin films of Cu-MgF₂ were deposited onto glass substrates using a conventional resistive heating co-evaporation technique. Films of starting compositions 40, 60 and 80 vol % Cu and average thicknesses 60, 145 and 285 nm were deposited at elevated substrate temperatures between 300 and 393 K in a vacuum of 1.33 × 10^–3 Pa. Room temperature D.C. resistivity measurements were performed at atmospheric pressure from which activation energies and TCRs for the cermet films were determined. It was observed that the resistivity () data fitted into the ln 1/T relationship. The activation energies were found to decrease with increase in film thickness and increase in metallic content of the cermet films whilst the TCRs were all negative. From the trends in both activation energies and TCRs it was concluded that the predominant conduction mechanism was tunnelling of thermally activated charge carriers.     

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.     

Electrical properties of stacked CuInSe<Subscript>2</Subscript> thin films

CuInSe₂ thin films have been prepared by the processing of stacked elemental layer (SEL) on glass substrates followed by annealing in air for different times. Films produced at 300 and 350 ^∘C showed n-type semiconductor due to indium interstitial donors. Electrical properties (resistivity) of the CuInSe₂ films have been systematically studied in terms of annealing temperatures and times. The resistivity was in the interval 10¹–10⁴ Ω cm and influenced by the heating time and decreased with temperature. The activation energy ranged from 0.046 to 0.154 eV in the range 300–600 K. The scattering process due to the energy barriers that exist between adjacent grains was considered.     

Si（111）衬底上沉积LaNiO3薄膜的取向控制和导电性能研究

通过金属有机物沉积的方法在Si（111）衬底上成功制备出了高度（100）和（110）取向的LaNiO3薄膜。研究了不同热处理过程、薄膜厚度、前驱体溶液对LaNiO3取向的影响,以及厚度热处理温度、（100）方向的取向度与薄膜方阻之间的关系。LaNiO3薄膜的相结构由XRD（X射线衍射）分析,薄膜的晶粒大小和表面粗糙度由AFM（原子力显微镜）分析。     

Structural,electrical and optical properties of copper selenide thin films deposited by chemical bath deposition technique

A low cost chemical bath deposition (CBD) technique has been used for the preparation of Cu_2–xSe thin films on glass substrates. Structural, electrical and optical properties of these films were investigated. X-ray diffraction (XRD) study of the Cu_2–xSe films annealed at 523 K suggests a cubic structure with a lattice constant of 5.697 Å. Chemical composition was investigated by X-ray photoelectron spectroscopy (XPS). It reveals that absorbed oxygen in the film decreases remarkably on annealing above 423 K. The Cu/Se ratio was observed to be the same in as-deposited and annealed films. Both as-deposited and annealed films show very low resistivity in the range of (0.04–0.15) × 10^–5 -m. Transmittance and Reflectance were found in the range of 5–50% and 2–20% respectively. Optical absorption of the films results from free carrier absorption in the near infrared region with absorption coefficient of 10⁸ m^–1. The band gap for direct transition, E_g.dir varies in the range of 2.0–2.3 eV and that for indirect transition E_g.indir is in the range of 1.25–1.5 eV.     

Properties of indium tin oxide films deposited using High Target Utilisation Sputtering

Indium tin oxide (ITO) films were deposited on soda lime glass and polyimide substrates using an innovative process known as High Target Utilisation Sputtering (HiTUS). The influence of the oxygen flow rate, substrate temperature and sputtering pressure, on the electrical, optical and thermal stability properties of the films was investigated. High substrate temperature, medium oxygen flow rate and moderate pressure gave the best compromise of low resistivity and high transmittance. The lowest resistivity was 1.6 × 10^− 4 Ω cm on glass while that on the polyimide was 1.9 × 10^− 4 Ω cm. Substrate temperatures above 100 °C were required to obtain visible light transmittance exceeding 85% for ITO films on glass. The thermal stability of the films was mainly influenced by the oxygen flow rate and thus the initial degree of oxidation. The film resistivity was either unaffected or reduced after heating in vacuum but generally increased for oxygen deficient films when heated in air. The greatest increase in transmittance of oxygen deficient films occurred for heat treatment in air while that of the highly oxidised films was largely unaffected by heating in both media. This study has demonstrated the potential of HiTUS as a favourable deposition method for high quality ITO suitable for use in thin film solar cells.     

Effect of substrate temperatures on the electrical resistivity of thermally evaporated Mn thin films

Resistivity measurements have been performed on three samples of Mn thin films from 300 to 1.4 K using the van der Pauw four probe technique. The films were grown by thermal evaporation onto glass substrates held at 523, 323 and 77 K, respectively in a bell jar held at 6 × 10⁻⁶ Torr. The resistivity-temperature results of the three specimens reveal a variety of low temperature behaviours. A behaviour typical of the bulk α-Mn is obtained with the film grown at a substrate temperature of 523 K whilst with the film grown at a substrate temperature of 323 K, the resistivity tends to a saturation at low temperatures exhibiting a behaviour reminiscent of Kondo scattering. The resistivity-temperature behaviour of the sample held at a substrate temperature of 77 K may be regarded as typical of a metallic alloy glass with a negative temperature coefficient of resistivity at high temperatures and this turns to a T² dependence of resistivity at very low temperatures.     

Semiconducting behaviour of thin bismuth films vacuum-deposited at different substrate temperatures

Thin bismuth films (thickness 25 nm) have been vacuum-deposited onto glass substrates at different substrate temperatures in a vacuum of 2×10^–5 torr. The resistance of the films has been measured as a function of temperaturein situ during and after annealing. It is found that the resistance of all the annealed films decreases with increasing temperature thus showing a semiconducting type of behaviour. The films do not show a resistivity minimum observed in thicker films [1]. The absence of a resistivity minimum is attributed to the thinness of the films and consequent larger energy band gap and smaller grain size.     

Electrical conductivity and optical properties of ZnO films annealed in hydrogen atmosphere after chemical vapor deposition

The d.c. electrical conductivity and optical properties of polycrystalline zinc oxide films (220–450 nm thick) annealed in hydrogen after chemical vapor deposition are investigated. A minimum film resistivity after the annealing gives 0.31 cm for the film as-deposited at a substrate temperature of 823 K. From the temperature dependence of conductivity, band conduction is confirmed for the films at temperatures above 250 K. The effect of grain-boundary scattering is due to thermionic emission of electrons over grain boundary barriers. At temperatures below 250 K, variable-range hopping transport is found to be dominant. The films are transparent in the wavelength range 400 to 1000 nm and have sharp ultraviolet absorption edges at 380 nm. The absorption edge analysis reveals the optical band gap energy for the films to be 3.18–3.23 eV. The Urbach tail analysis gives the width of localized states E_e=0.06-0.14eV.     

Low-temperature epitaxial growth of conductive LaNiO3 thin films by RF magnetron sputtering

Epitaxial growth of LaNiO₃ (LNO) thin films was successful on CeO₂/YSZ/Si(100), MgO(100) and SrTiO₃ (STO)(100) substrates by RF magnetron sputtering at 300 °C, although pulsed laser deposition requires 600 °C to prepare epitaxial LNO films according to the literature. Epitaxial LNO films deposited on CeO₂/YSZ/Si(100) and STO(100) had single orientation of LNO[100]//CeO₂[110]//YSZ[110]//Si[110]) and LNO[100]//STO[100], respectively. On the other hand, epitaxial LNO films deposited on MgO(100) had mixed orientations of LNO[100]//MgO[100] and LNO[100]//MgO[110]. The lattice parameter, composition and resistivity of the LNO thin films were strongly dependent on the substrate temperature. The minimum resistivity of LNO films was approximately 5×10⁻⁶ Ω m, which value almost agrees with the resistivity in the literature. It was found that the temperature to achieve minimum resistivity was 200 °C, irrespective of the type of substrate. The surface of the LNO films was smooth and flat.     

Optical and structural properties of (Ba, Sr)TiO3 thin films grown by radio-frequency magnetron sputtering

We studied the structural and optical properties of (Ba, Sr)TiO₃ (BST) films deposited on the transparent substrates at various temperatures of 350–650°C and annealed at 450–650°C. Improved crystallization can be observed on 650°C annealed film whose substrate temperature is 350°C. The refractive index increased from 2.17 to 2.59 at =410 nm for the BST films deposited at 350–650°C and it varied from 2.17 to 2.25 after annealing up to 650°C. In addition, the refractive-index dispersion data related to the short-range-order structure of BST films obeyed the single-oscillation energy model. The indirect energy gap of the films deposited on Al₂O₃ and quartz substrates was found to be about 3.5 eV. According to the analysis of reflectance data, the optical inhomogeneity of films can be reduced by depositing the films at intermediate temperatures 450–550°C.     

Correlation Between the Morphology of Ag and the Contact Resistivity of the Ag/YBa2Cu3O7?δ Thin Film Contact

The morphology of the silver films deposited and annealed on laser ablated YBa₂Cu₃O_7– thin films and the corresponding contact resistivity have been systematically investigated. A minimum contact resistivity of 6 × 10^–8 cm² was reached at 77 K by annealing Ag/YBa₂Cu₃O_7– contact at the optimum temperature. The effect of the annealing temperature on the contact resistivity was explained by considering the morphology of the silver films and the diffusion of silver into YBa₂Cu₃O_7– film, etc. The difference of the contact resistivity for Ag contact to polycrystalline, single crystal and thin film of YBa₂Cu₃O_7– were also explained.     

Bias voltage dependence properties of cadmium oxide films deposited by d.c. reactive magnetron sputtering

Cadmium oxide films were grown on glass substrates using d.c. reactive magnetron sputtering technique by sputtering from a metallic cadmium target in an oxygen partial pressure of 1×10^–3 mbar under various substrate bias voltages. The substrate bias voltage significantly influences the crystallographic structure of the deposited films. The influence of substrate bias voltage on the electrical and optical properties of the films was systematically studied. The films formed at a substrate temperature of 473 K and bias voltage of –80 V showed an electrical resistivity of 1×10^–3 cm, optical transmittance of 86%, optical band gap of 2.47 eV and a figure of merit of 7×10^{–3 –1}.