Optical and electrical properties of heat-resistant Sb-doped Sn1 − xHfxO2 transparent conducting films

To examine variations in the transparent conducting properties after annealing at high temperatures, 300-nm thick Sb-doped Sn_1 − xHf_xO₂ (x = 0.00-0.10) films were deposited onto silica glass substrates by the RF sputtering method and annealed in air up to 1000 °C at 200 °C increments. After annealing, all the Sb-doped SnO₂ films were transparent and electrically conductive, but large cracks, which decreased the electrical conductivity, were generated in several films due to crystallization or the thermal expansion difference between the film and substrate. Only the film deposited at room temperature in an Ar and O₂ mixed atmosphere did not crack after annealing, and its electrical conductivity exceeded 100 S cm^− 1 even after annealing at 1000 °C in air. Hf-doping blue shifted the fundamental absorption edges in the UV region in the Sb-doped Sn_1 − xHf_xO₂ films. Additionally, the optical transmission at 310 nm, T₃₁₀, increased as the Hf concentration increased, whereas the electrical conductivity was inversely proportional to the Hf concentration. On the other hand, thinner films (150-nm thick) with x = 0.00 showed both a high electrical conductivity over 100 S cm^− 1 and a high transparency T₃₁₀ = 65% after high temperature annealing.     

Structural and optical properties of Ti-doped ZnO thin films prepared by the cathodic vacuum arc technique with different annealing processes

Highly transparent Ti-doped ZnO thin films were prepared on glass substrates at a deposition rate of approximately 33 nm/min using the cathodic vacuum arc technique with a Zn target power of 550 W and a Ti target power of 750 W, respectively. X-ray diffraction measurements have shown that the Ti-doped ZnO thin film with a vacuum post-annealing condition is c-axis oriented but an amorphous phase at the other post-annealing atmosphere and as-deposited condition. Transmittance measurements show that the best optical quality of the Ti-doped ZnO thin films occurred at a post-annealing atmosphere of N₂/H₂ mixed gases. Additionally, the optical transmittance of all films has been found more than 85% in a range of 500-700 nm. The lowest electrical resistivity was 3.48 × 10⁻³ Ω cm, obtained on as-deposited films. However, the post-annealing condition greatly increased the resistivity.     

Structural and electrical characteristics of chemical solution derived (Bi3.2La0.4Nd0.4)Ti3O12 thin films

(Bi_3.2La_0.4Nd_0.4)Ti₃O₁₂ (BLNT) thin films were prepared on Pt/Ti/SiO₂/Si substrates by using chemical solution deposition technique, and the effects of annealing temperatures in the range of 550-750 °C on structure and electrical properties of the thin films were investigated. X-ray diffraction analysis shows that the thin films have a bismuth-layered perovskite structure with preferred (117) orientation. The surface morphology observation by field-emission scanning electron microscopy confirms that films are dense and smooth with uniformly distributed grains. The grain size of the thin films increases with increasing annealing temperature; meanwhile, the structural distortion of the thin films also increases. It was demonstrated that the thin films show good electrical properties. The dielectric constant and dielectric loss are 191 and 0.028, respectively, at 10 kHz for the thin film annealed at 600 °C, and the 2Pr value of the thin film annealed at 700 °C is 20.5 μC/cm² at an electric field of 500 kV/cm.     

Effect of substrate temperature and annealing treatment on the electrical and optical properties of silver-based multilayer coating electrodes

Multilayer coatings consisting of thin silver layers sandwiched between layers of transparent conducting metal oxides are investigated from the view point of low-resistance electrodes for use in flat panel displays, solar cells, etc. ZnO/Ag/ZnO multilayer films were prepared on glass substrates by simultaneous RF magnetron sputtering of ZnO and dc magnetron sputtering of Ag. Optimization of the deposition conditions of both ZnO layers and metallic layers were performed for better electrical and optical properties. The structural, electrical and optical properties of the films (deposited at room temperature, different substrate temperature and annealed at different conditions) were characterized with various techniques. We could not produce high-quality transparent conductive electrodes simply by annealing at various temperatures. However, improved electrical properties and a considerable shift in the transmittance curves was observed after heat treatment. The experimental results show that the electrical resistivity of as-grown films can be decreased to 10^− 5 Ω cm level with post-annealing at 400 °C for 2 h in vacuum atmosphere. After heat treatment, the sheet resistance was reduced as much as 20% which was due to the increased grain size of Ag film. The samples heat treated at 200-400 °C under vacuum or nitrogen atmosphere showed the best electrical properties. The key to the superior electrical and optical properties of the multilayer is the optimization of growth conditions of the silver layer by careful control of the oxide properties and the use of appropriate annealing temperature and atmosphere.     

Preparation of anatase TiO2 thin films by vacuum arc plasma evaporation

Anatase titanium dioxide (TiO₂) thin films with high photocatalytic activity have been prepared with deposition rates as high as 16 nm/min by a newly developed vacuum arc plasma evaporation (VAPE) method using sintered TiO₂ pellets as the source material. Highly transparent TiO₂ thin films prepared at substrate temperatures from room temperature to 400 °C exhibited photocatalytic activity, regardless whether oxygen (O₂) gas was introduced during the VAPE deposition. The highest photocatalytic activity and photo-induced hydrophilicity were obtained in anatase TiO₂ thin films prepared at 300 °C, which correlated to the best crystallinity of the films, as evidenced from X-ray diffraction. In addition, a transparent and conductive anatase TiO₂ thin film with a resistivity of 2.6 × 10^− 1 Ω cm was prepared at a substrate temperature of 400 °C without the introduction of O₂ gas.     

Growth and characterization of Bi2Se3 thin films by pulsed laser deposition using alloy target

Bi₂Se₃ thin films were deposited on the (100) oriented Si substrates by pulsed laser deposition technique at different substrate temperatures (room temperature −400 °C). The effects of the substrate temperature on the structural and electrical properties of the Bi₂Se₃ films were studied. The film prepared at room temperature showed a very poor polycrystalline structure with the mainly orthorhombic phase. The crystallinity of the films was improved by heating the substrate during the deposition and the crystal phase of the film changed to the rhombohedral phase as the substrate temperature was higher than 200 °C. The stoichiometry of the films and the chemical state of Bi and Se elements in the films were studied by fitting the Se 3d and the Bi 4d5/2 peaks of the X-ray photoelectron spectra. The hexagonal structure was seen clearly for the film prepared at the substrate temperature of 400 °C. The surface roughness of the film increased as the substrate temperature was increased. The electrical resistivity of the film decreased from 1 × 10⁻³ to 3 × 10⁻⁴ Ω cm as the substrate temperature was increased from room temperature to 400 °C.     

Reaction of Al/Mo thin films

Intermixing and compound formation by means of annealing have been studied for Al/Mo thin films. With annealing at 300° C, only intermixing between aluminium and molybdenum films occurs due to mutual diffusion. With annealing at over 350° C, Al₁₂Mo and AlMo₃ compounds were formed. The electrical resistivity of the film increases with intermixing and compound formation. The electrical resistivity increase is proportional to the annealing time,t ^1/2. In low vacuum annealing, molybdenum oxide film forms on aluminium film. It is assumed that molybdenum atoms diffuse through the aluminium film due to their chemical affinity with oxygen in the atmosphere.     

Growth and characterization of Ba(Cd1/3Ta2/3)O3 thin films

We have synthesized stoichiometric Ba(Cd_1/3Ta_2/3)O₃ [BCT] (100) dielectric thin films on MgO (100) substrates using Pulsed Laser Deposition. Over 99% of the BCT film was found to be epitaxial [BCT (100) || MgO (100) and BCT (010) || MgO (010)] when grown with an elevated substrate temperature of 635 °C, an enhanced oxygen pressure of 53 Pa and a Cd-enriched BCT target with a 1 mol BCT: 1.5 mol CdO composition. A dielectric constant of 32 was inferred from low-frequency capacitance measurements of a planar interdigital metal pattern. Analysis of ultra violet optical absorption results indicates that BCT has a bandgap of 4.9 eV; while the interference pattern in the visible range is consistent with a refractive index of 2.1. Temperature-dependent electrical measurements indicate that the BCT films have a room temperature conductivity of 3 × 10^− 12 Ω^− 1 cm^− 1 with a thermal activation energy of 0.7 eV. A mean particle size of ~ 100 nm and a root mean square surface roughness of 5 to 6 nm were measured using Atomic Force Microscopy.     

Effects of deposition temperature on structure and properties of mo-doped indium oxide by radio frequency magnetron sputtering

Transparent conductive oxide (TCO) thin films of Mo-doped In₂O₃ (IMO) were prepared on glass substrates by radio frequency magnetron sputtering from the 2 wt% Mo-doped In₂O₃ ceramic target. The depositions were carried out under an oxygen-argon atmosphere by varying the deposition temperature from 200 °C to 350 °C. The crystal structure and thickness of IMO thin films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effects of deposition temperature on the electrical and optical transmittance properties of IMO thin films were investigated by four-point probe Hall system and UV-VIS-NIR spectrophotometer separately. The optimum deposited IMO thin films were obtained with resistivity of 6.9 × 10⁻⁴ Ω cm and carrier mobility 45 cm²v⁻¹s⁻¹ at 350 °C. The average optical transmittance of IMO films on glass substrates are over 80% in the near-infrared region.     

The effect of annealing on Al-doped ZnO films deposited by RF magnetron sputtering method for transparent electrodes

In this study, transparent conducting Al-doped zinc oxide (AZO) films with a thickness of 150 nm were prepared on Corning glass substrates by the RF magnetron sputtering with using a ZnO:Al (Al₂O₃: 2 wt.%) target at room temperature. This study investigated the effects of the post-annealing temperature and the annealing ambient on the structural, electrical and optical properties of the AZO films. The films were annealed at temperatures ranging from 300 to 500 °C in steps of 100 °C by using rapid thermal annealing equipment in oxygen. The thicknesses of the films were observed by field emission scanning electron microscopy (FE-SEM); their grain size was calculated from the X-ray diffraction (XRD) spectra using the Scherrer equation. XRD measurements showed the AZO films to be crystallized with strong (002) orientation as substrate temperature increases over 300 °C. Their electrical properties were investigated by using the Hall measurement and their transmittance was measured by UV-vis spectrometry. The AZO film annealed at the 500 °C in oxygen showed an electrical resistivity of 2.24 × 10^− 3 Ω cm and a very high transmittance of 93.5% which were decreased about one order and increased about 9.4%, respectively, compared with as-deposited AZO film.     

Microstructure and electrical properties of Al2O3-ZrO2 composite films for gate dielectric applications

Al₂O₃-ZrO₂ composite films were fabricated on Si by ultrahigh vacuum electron-beam coevaporation. The crystallization temperature, surface morphology, structural characteristics and electrical properties of the annealed films are investigated. Our results indicate that the amorphous and mixed structure is maintained up to an annealing temperature of 900 °C, which is much higher than that of pure ZrO₂ film, and the interfacial oxide layer thickness does not increase after annealing at 900 °C. However, a portion of the Al₂O₃-ZrO₂ film becomes polycrystalline after 1000 °C annealing and interfacial broadening is observed. Possible explanations are given to explain our observations. A dielectric constant of 20.1 is calculated from the 900 °C-annealed ZrO₂-Al₂O₃ film based on high-frequency capacitance-voltage measurements. This dielectric characteristic shows an equivalent oxide thickness (EOT) as low as 1.94 nm. An extremely low leakage current density of ∼2×10⁻⁷ A/cm² at a gate voltage of 1 V and low interface state density are also observed in the dielectric film.     

Influences of post-annealing on structural and electrical properties of Bi1.5Zn1.0Nb1.5O7 thin films prepared by pulsed laser deposition

Bi_1.5Zn_1.0Nb_1.5O₇ (BZN) thin films were prepared on Pt/TiO₂/SiO₂/Si(100) substrates at 650 °C under an oxygen pressure of 10 Pa by using pulsed laser deposition process. The crystallinity, microstructure and electrical properties of BZN thin films were investigated to verify the influences of post-annealing thermal process on them. The X-ray diffractometer (XRD) results indicate that all Bi_1.5Zn_1.0Nb_1.5O₇ thin films without post-annealing process or with post-annealing in situ vacuum chamber and in oxygen ambient exhibit a cubic pyrochlore structure. The improved crystallinity of BZN thin films through post-annealing was confirmed by XRD and scanning electron microscope (SEM) analysis. Dielectric constant and loss tangent of the as-deposited BZN thin films are 160 and 0.002 at 10 kHz, respectively. After annealing, dielectric properties of thin films are significantly improved. Dielectric constant and loss tangent of the in situ annealed films are 181 and 0.0005 at 10 kHz, respectively. But the films post-annealed in O₂ oven show the largest dielectric constant of 202 and the lowest loss tangent of 0.0002, which may attribute to the increase in grain size and the elimination of oxygen vacancies. Compared with the as-deposited BZN thin films, the post-annealed films also show the larger dielectric tunability and the lower leakage current density.     

Novel properties of AZO film sputtered in Ar+H2 ambient at high temperature

AZO (ZnO:Al) transparent conductive thin film was prepared by RF magnetron sputtering with a AZO (98 wt% ZnO 2 wt% Al₂O₃) ceramic target in the same Ar+H₂ ambient at different substrate temperatures ranging from 100 to 300 °C. The minimum resistivity of AZO films was 7.9×10⁻⁴ Ω cm at the substrate temperature of 200 °C. The average transmission in the visible rang was more than 90%. Scanning electron microscopy and XRD analyses showed that the surface morphology of the AZO samples altered with the increasing of the substrate temperature. AZO film prepared at 200 °C in the pure Ar ambient was also made as comparison about the resistivity, carrier concentration and the average crystallite size. The resistivity became about 3 times higher. The carrier concentration became lower and the average crystallite size was smaller.     

Effect of post-annealing treatment in oxygen on dielectric properties of K0.5Na0.5NbO3 thin films prepared by chemical solution deposition

K_0.5Na_0.5NbO₃ thin films were prepared on Pt/Ti/SiO₂/Si substrates by chemical solution deposition method with different annealing temperatures of 550 °C, 600 °C, 700 °C. The post-annealing treatment was introduced at 550 °C for 3 min in oxygen ambient. It is found that the films were composed of pure provskite phase, and the post-annealing treatment promoted the crystallization and improved the quality of the films, which resulted in the enhancement of the dielectric property of the films. The effect of the post-annealing on the dielectric properties of the films was also discussed.     

Enhancement on effective piezoelectric coefficient of Bi3.25Eu0.75Ti3O12 ferroelectric thin films under moderate annealing temperature

Bi_3.25Eu_0.75Ti₃O₁₂ (BET) thin films were deposited on Pt/Ti/SiO₂/Si(111) substrates by a metal-organic decomposition method. The effects of annealing temperatures 600-800 °C on microstructure, ferroelectric, dielectric and piezoelectric properties of BET thin films were studied in detail. The spontaneous polarization (87.4 × 10^− 6 C/cm² under 300 kV/cm), remnant polarization (65.7 × 10^− 6 C/cm² under 300 kV/cm), the dielectric constant (992.9 at 100 kHz) and the effective piezoelectric coefficient d₃₃ (67.3 pm/V under 260 kV/cm) of BET thin film annealed at 700 °C are better than those of the others. The mechanisms concerning the dependence of the enhancement d₃₃ are discussed according to the phenomenological equation, and the improved piezoelectric performance could make the BET thin film a promising candidate for piezoelectric thin film devices.     

Temperature dependent Raman scattering of the epitaxial Sr1.9Ca0.1NaNb5O15 film

Epitaxial ferroelectric Sr_1.9Ca_0.1NaNb₅O₁₅ (SCNN) thin films have been fabricated successfully by pulsed laser deposition on (100)MgO substrates. Temperature dependency of the vibrational modes of these films was investigated for the first time using Raman scattering technique. For temperatures ranging between 50 °C and 450 °C, two strong and broad A₁(TO) phonons around 238 and 608 cm^− 1, and one weak B₁(TO) phonon around 142 cm^− 1 were observed. Changes in the temperature dependency of the peak position, the full-width at half maximum and integrated intensity of the Raman modes were observed in different temperature ranges. These changes are attributed to the structural phase transitions between 200 °C and 325 °C for the SCNN films as well as their relaxor properties.     

Preparation of LaNiO3 thin films with very low room-temperature electrical resistivity by room temperature sputtering and high oxygen-pressure processing

LaNiO₃ (LNO) thin films were deposited by radio frequency magnetron sputtering on n-type Si (100) wafers at room temperature (RT). The as-sputtered LNO thin films were amorphous and had very high RT electrical resistivity even after post-annealing at 800 °C. The amorphous as-sputtered LNO films could be transformed to polycrystalline LNO films in rhombohedral phase by heating at 400 °C in an O₂ atmosphere at pressure ranging from 1.5 to 8.0 MPa. Very low RT resistivity of LNO films were obtained by this high oxygen-pressure processing. The lowest value was as low as 1.09 × 10^− 4 Ω cm by processing at oxygen pressure of 8 MPa. Such preparation of LNO thin films is compatible with the Si-based readout integrated circuits. Highly (100)-oriented perovskite structure of Pb(Zr_0.52Ti_0.48)O₃ thin films was formed on this rhombohedral phase LNO, and good ferroelectricity could also be obtained on these HOPP-processed rhombohedral phase LNO films.     

The influence of annealing temperatures on the properties of Bi2VO5.5/LaNiO3/Si thin films

Bi₂VO_5.5 ferroelectric thin films were fabricated on LaNiO₃/Si(100) substrate via chemical solution deposition. Ferroelectric and dielectric properties of the thin films annealed at 500-700 °C were studied. The thin film annealed at 700 °C exhibited more favorable ferroelectric and dielectric properties than those annealed at lower temperatures. The values of remnant polarization 2P_r and coercive field E_c for the film annealed at 700 °C are 10.62 µC/cm² and 106.3 kV/cm, respectively. The leakage current of the film is about 1.92 × 10^− 8 A/cm² at 6 V. The possible mechanism of the dependence of electrical properties of the films on the annealing temperature was discussed.     

Thermal treatment effects on interfacial layer formation between ZrO2 thin films and Si substrates

This paper describes the growth condition of stoichiometric ZrO₂ thin films on Si substrates and the interfacial structure of ZrO₂ and Si substrates. The ZrO₂ thin films were prepared by rf-magnetron sputtering from Zr target with mixed gas of O₂ and Ar at room temperature followed by post-annealing in O₂ ambient. The stoichiometric ZrO₂ thin films with smooth surface were grown at high oxygen partial pressure. The thick Zr-free SiO₂ layer was formed with both Zr silicide and Zr silicate at the interface between ZrO₂ and Si substrate during the post-annealing process due to rapid diffusion of oxygen atoms through the ZrO₂ thin films. After post annealing at 650-750 °C, the multi-interfacial layer shows small leakage current of less than 10⁻⁸ A/cm² that is corresponding to the high-temperature processed thermal oxidized SiO₂.     

Dip coated 12CaO·7Al2O3 thin films through sol-gel process using metal alkoxide

Transparent nanostructured 12CaO·7Al₂O₃ thin films with cubic structure have been prepared on soda lime glass substrates via the sol-gel dip coating using the precursor sol solution at low temperature. The structural, compositional, morphological and optical properties of the 12CaO·7Al₂O₃ films and powder were studied using X-ray diffractometry (XRD), X-ray photoelectron spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy. Optical properties of 12CaO·7Al₂O₃ films have been investigated using UV-visible spectroscopy. Two different precursor sols were prepared using calcium-2-ethyl hexonate and aluminium isopropoxide as precursor materials in isopropanol and ethylene glycol monomethyl ether solvents. Dip coated gel like films were dried at 120 °C for 15 min and subsequently heat-treated at 450 °C for 1 h in air atmosphere. The influence of films thickness and optical transparency with use of different solvent and sol concentration on microstructure of the films were established. In addition, XRD patterns revealed that 12CaO·7Al₂O₃ films have been composed of cubic phase. SEM observations exhibited that the films structure becomes more homogeneous using isopropanol as compared to ethylene glycol monomethyl ether solvent. The 12CaO·7Al₂O₃ films prepared using 2 (wt.%) sol in isopropanol had high transparency nearly 88% in wide visible range with maximum of 90% at 600 nm wavelength.