Synthesis of high-quality AZO polycrystalline films via target bias radio frequency magnetron sputtering

The deposition rate, transmittance and resistivity of aluminium-doped zinc oxide (AZO) films deposited via radio frequency (r.f.) sputtering change with target thickness. An effective method to control and maintain AZO film properties was developed. The strategy only involved the regulation of target bias voltage of r.f. magnetron sputtering system. The target bias voltage considerably influenced AZO film resistivity. The resistivity of the as-deposited AZO film was 9.82×10⁻⁴ Ω cm with power density of 2.19 W/cm² at target self-bias of −72 V. However, it decreased to 5.98×10⁻⁴ Ω cm when the target bias voltage was increased to −112 V by applying d.c. voltage. Both growth rate and optical band gap of AZO film increased with the absolute value of target bias voltage – growth rate increased from 10.54 nm/min to 25.14 nm/min, and band gap increased from 3.57eV to 3.71 eV when target bias voltage increased from −72 V to −112 V at r.f. power density of 2.19 W/cm². The morphology of AZO films was slightly affected by the target bias voltage. Regulating target bias voltage is an effective method to obtain high-quality AZO thin films deposited via r.f. magnetron sputtering. It is also a good choice to maintain the quality of AZO film in uptime manufacturing deposition.     

Aluminum doped zinc oxide sputtering targets obtained from nanostructured powders: Processing and application

This work reports the production of ceramic targets based on nanostructured Al-doped ZnO (AZO) powders for sputtering applications. The nanostructured powder is obtained by a new patented process based on the detonation of an emulsion containing both Zn and Al metal precursors in the final proportion of 98:2 wt% (ZnO:Al₂O₃), through which the Al contains is highly uniform distributed over ZnO. Due to the nanostructured powder characteristics, the targets can be sintered at substantially lower temperatures (1150–1250 °C) by conventional sintering, contributing to production costs reduction of ceramic targets and consequently the costs of photovoltaic and displays industries. Electrical resistivity values around 3.0–7.0 × 10^?3 Ω cm have been obtained depending on final microstructure of the targets. The electro-optical properties of the films produced at room temperature with thicknesses around 360 nm, besides being highly uniform exhibit a resistivity of about 1 × 10^?3 Ω cm and a transmittance in the visible range above 90%.     

Preparation and characterization of transparent indium- doped TiO2 films deposited by MOCVD

Titanium dioxide (TiO₂) films doped with different indium (In) concentrations have been prepared on SrTiO₃ (STO) substrates by high vacuum metalorganic chemical vapor deposition (MOCVD). X-ray diffraction (XRD) analyses revealed the TiO₂ films doped with low In concentrations to be [001] oriented anatase phase and the films with high In concentrations to present polycrystalline structures. The 1.8% In-doped TiO₂ film exhibited the best electrical conductivity properties with the lowest resistivity of 8.68×10⁻² Ω cm, a Hall mobility of 10.9 cm² V⁻¹ s⁻¹ and a carrier concentration of 6.5×10¹⁸ cm⁻³. The films showed excellent transparency with average transmittances of over 85% in the visible range.     

The Sintering Trajectory and Electrical Properties of Niobium‐Doped Titania Sputtering Targets

Nb‐doped TiO₂ (TNO) films, which are highly conductive and transparent, can be used as transparent conductive oxide (TCO) films. A predominant manufacturing method for TCO film is magnetron sputtering, and the material of the sputtering target affects the performance of the film. The objective of this study was to investigate the sintering densification, microstructure, and electrical properties of TNO and TiO₂ sputtering targets. The results showed that the segregation of Nb at the grain boundary in TNO helps to facilitate densification and inhibit grain growth. After 1200°C sintering, the sintered density of TNO target achieves almost 100% of the theoretical density. Moreover, the Nb₂O₅ additive greatly improves the electrical properties, decreasing the resistivity of TiO₂ from >10⁸ Ωcm to 4.6 × 10¹ Ωcm. Correlations between TNO sputtering target investigated in this study and TNO sputtered film reported in the literature are also preliminarily established. The resistivity of TNO film with an anatase structure is obviously lower than that of TNO target with a rutile structure.     

Highly conducting and transparent antimony doped tin oxide thin films: the role of sputtering power density

Sb doped SnO₂ thin films were deposited on quartz substrates by magnetron sputtering at 600 °C and the effects of sputtering power density on the preferential orientation, structural, surface morphological, optical and electrical properties had been studied. The XRD analyses confirm the formation of cassiterite tetragonal structure and the presence of preferential orientation in (2 1 1) direction for tin oxygen thin films. The dislocation density analyses reveal that the generated defects can be suppressed by the appropriate sputtering power density in the SnO₂ lattice. The studies of surface morphologies show that grain sizes and surface roughness are remarkably affected by the sputtering power density. The resistivity of Sb doped SnO₂ thin films gradually decreases as increasing the sputtering power density, reaches a minimum value of 8.23×10⁻⁴ Ω cm at 7.65/cm² and starts increasing thereafter. The possible mechanisms for the change in resistivity are proposed. The average transmittances are more than 83% in the visible region (380–780 nm) for all the thin films, the optical band gaps are above 4.1 eV. And the mechanisms of the variation of optical properties at different sputtering power densities are addressed.     

Influence of a Ni interlayer on the optical and electrical properties of trilayer GZO/Ni/GZO films

Trilayer GZO/Ni/GZO films were deposited onto polycarbonate (PC) substrates with RF and DC magnetron sputtering, and then the influence of a Ni interlayer on the optical and electrical properties of the films was investigated. A 2-nm-thick Ni interlayer decreased the resistivity to 6.4×10⁻⁴ Ω cm and influenced the optical transmittance.Although optical transmittance deteriorated with Ni insertion, the films showed a relatively high optical transmittance of 74.5% in the visible wavelength region. The figure of merit (FOM) of a GZO single layer film was 1.2×10⁻⁴ Ω⁻¹, while that of the GZO/Ni/GZO films reached a maximum of 8.2×10⁻⁴ Ω⁻¹.Since a higher FOM results in higher quality transparent-conductive oxide (TCO) films, it is concluded that GZO films with a 2 nm Ni interlayer have better optoelectrical performance than single-layer GZO films.     

Sputtering deposition of transparent conductive F-doped SnO2 (FTO) thin films in hydrogen-containing atmosphere

F-doped SnO₂ (FTO) thin films have been prepared by sputtering SnO₂-SnF₂ target in Ar+H₂ atmosphere. The effects of H₂/Ar flow ratio on the structural, electrical and optical properties of the films were investigated at two substrate temperatures of 150 and 300 °C and two base pressures of 3.5×10⁻³ and 1.5×10⁻² Pa. The results show that introducing H₂ into sputtering atmosphere can lead to the formation of a FTO film with a (101) preferred orientation and produce oxygen vacancy (V_O) at lower H₂/Ar flow ratios, but SnO phase at higher H₂/Ar flow ratios in the films. Accordingly, the resistivity of the films first decreases and then increases, but the transmittance decreases continuously with increasing H₂/Ar flow ratio. When H₂/Ar flow ratio is increased above a certain value, more amorphous SnO phase forms in the films, resulting in a big decrease in conductivity, transmittance, and band gap (E_g). Increasing substrate temperature can increase the Hall mobility due to the improvement of film crystallinity, but decrease the carrier concentration due to outward-diffusion of fluorine in the films. At a base pressure of 3.5×10⁻³ Pa, high substrate temperature (300 °C) can hinder the formation of SnO and thus improve the transparent conductive properties of the films. At a base pressure of 1.5×10⁻² Pa, the range of H₂/Ar flow ratio for forming the SnO₂ phase and hence for obtaining high transparent conductive FTO films is widened at both substrate temperatures of 150 and 300 °C.     

Structural,electrical and optical properties of molybdenum-doped TiO2 thin films

Molybdenum doped TiO₂ (MTO) thin films were prepared by radio frequency (RF) magnetron sputtering at room temperature and followed by a heat treatment in a reductive atmosphere containing 90% N₂ and 10% H₂. XRD and FESEM were employed to evaluate the microstructure of the MTO films, revealing that the addition of molybdenum enhances the crystallization and increases the grain size of TiO₂ films. The optimal electrical properties of the MTO films were obtained with 3 wt% Mo doping, producing a resistivity of 1.1×10^?3 Ω cm, a carrier density of 9.7×10²⁰ cm^?3 and a mobility of 5.9 cm²/Vs. The refractive index and extinction coefficient of MTO films were also measured as a function of film porosity. The optical band gap of the MTO films ranged from 3.28 to 3.36 eV, which is greater than that of the un-doped TiO₂ film. This blue shift of approximately 0.14 eV was attributed to the Burstein–Moss effect.     

Low sintering of X7R ceramics based on barium titanate with SiO2–B2O3–Li2O sintering additives in reducing atmosphere

Development of a low-temperature sintered dielectric material derived from barium titanate for X7R characterized dielectric ceramics application is discussed in this paper. By addition of SiO₂–B₂O₃–Li₂O sintering additives to commercial BaTiO₃ powder, more than 95% of the theoretical density was obtained at a sintering temperature of 950 °C in H₂/N₂ atmosphere. The influence of the composition and procedures on the microstructures, lattice parameters and properties of ceramics materials were systemically studied. After explaining the reason for lower isolated resistivity (IR) in the previous experiment, several methods are tried out to improve the IR properties, which have reached the application requirement level of 10¹² Ω cm. These ceramics sintered between 900 °C and 950 °C in H₂/N₂ atmosphere are promising candidates for fabrication of Cu electrode MLCCs.     

Structural,electromagnetic, and dielectric properties of lithium-zinc ferrite ceramics sintered by pulsed electron beam heating

Structural, electromagnetic, and dielectric properties of Li_0.4Fe_2.4Zn_0.2O₄ lithium-zinc ferrite sintered by 2.4 MeV pulsed electron beam heating at 1050 °С for 2 h were investigated. The formation of ferrite with a single-phase cubic spinel structure was confirmed by X-ray diffraction analysis. The average grain size of ferrite ceramic was determined by SEM analysis and its value was 1.7 µm. The radiation-thermal sintered samples are characterized by a saturation magnetization of 67.8 emu/g, the Curie temperature of 508 °C, AC electrical resistivity of 2.4×10⁴ Ω cm (at 25 °C). The frequency dependences of permittivity and the loss tangent were obtained in (20 – 2×10⁶) Hz frequency range. The behavior of ε′ is characterized by high dispersion caused by relaxation polarization in the investigated frequency range. The results were compared to the LiZn ferrite characteristics sintered by traditional thermal heating.     

TiN modified SiC with enhanced strength and electrical properties

SiC based composites were manufactured with varying TiN content (0–50 V%) using Al₂O₃ and Y₂O₃ sintering aids. Basic dilatometry measurements were performed to determine when densification begins within the composite system. Samples were consolidated via uni-axial hot pressing at 1900 °C to produce ceramic composites with >98% theoretical density. Electrical measurements show increasing TiN additions reduce resistivity and begin to plateau at 40–50V%. Resistivity decreased from 2.0 × 10⁵ Ω − cm (0% TiN) to 2.0 × 10⁻⁴ Ω − cm (50V% TiN). Flexural strengths were characterized and compared against a baseline (0% TiN) SiC. Strengths increased gradually with TiN content. A maximum strength 921 MPa was observed at 40V% TiN content vs. 616 MPa for the baseline SiC. This was a gain of 50% over baseline. Additions beyond that range did not produce further gains in strength.     

Electrical resistivity of silicon carbide ceramics sintered with 1 wt% aluminum nitride and rare earth oxide

The influence of additive composition on the electrical resistivity of hot-pressed liquid-phase sintered (LPS)-SiC was investigated using AlN–RE₂O₃ (RE = Sc, Nd, Eu, Gd, Ho, Er, Lu) mixtures at a molar ratio of 60:40. It was found that all specimens could be sintered to densities >95% of the theoretical density by adding 5 wt% in situ-synthesized nano-sized SiC and 1 wt% AlN–RE₂O₃ additives. Six out of seven SiC ceramics showed very low electrical resistivity on the order of 10^?4 Ω m. This low electrical resistivity was attributed to the growth of nitrogen-doped SiC grains and the confinement of non-conducting RE-containing phases in the junction areas. The SiC ceramics sintered with AlN–Lu₂O₃ showed a relatively high electrical resistivity (～10^?2 Ω m) due to its lower carrier density (～10¹⁷ cm^?3), which was caused by the growth of faceted grains and the resulting weak interface between SiC grains.     

The sintering behavior,microstructure, and electrical properties of gallium-doped zinc oxide ceramic targets

The properties of sputtering targets have recently been found to affect the performances of sputtered films and the sputtering process. To develop high-quality GZO ceramic targets, the influences of Ga₂O₃ content and sintering temperature on the sintering behavior, microstructure, and electrical properties of GZO ceramic targets were studied.The results showed that the increase in Ga₂O₃ content from 3 wt% (GZO-3Ga) and 5 wt% (GZO-5Ga) not only inhibited the densification but retarded grain growth. During sintering, ZnGa₂O₄ phase formed before 800 °C, and Zn₉Ga₂O₁₂ phase was found after sintering at 1000 °C. Moreover, after sintering at 1200 °C, the number of Zn₉Ga₂O₁₂ precipitates increased at the expense of ZnGa₂O₄ and ZnGa₂O₄ disappearing completely. The relative density, grain size, and resistivity of GZO-3Ga sintered at 1400 °C in air were 99.3%, 3.3 μm, and 2.8 × 10⁻³ Ω cm, respectively. These properties of GZO ceramics are comparable to properties reported in the literature for AZO sintered in air.     

Studies on the properties of Ni0.6Cu0.4Mn2O4 NTC ceramic due to Fe doping

The influence of the Fe on the microstructure, electrical and dielectric properties of Ni_0.6Cu_0.4Fe_yMn_2?yO₄ (0.1 ≤ y ≤ 0.5) negative temperature coefficient (NTC) thermistors prepared by well known simple chemical co-precipitation method were studied. The replacement of manganese by iron plays an important role in changing the lattice parameter, X-ray density, sintered density, porosity, DC resistivity at different temperatures and dielectric properties at different frequencies. The X-ray and sintered density increased linearly and porosity decreased with iron. The room temperature resistivity of nickel copper manganite NTC ceramic decreased from 1 MΩ cm to 68 KΩ cm and dielectric constant increased from ～9 × 10⁷ to 1.5 × 10⁹ at 20 Hz as iron content increased.     

Fabrication of highly efficient TiO2/Ag/TiO2 multilayer transparent conducting electrode with N ion implantation for optoelectronic applications

Fabrication of highly conductive and transparent TiO₂/Ag/TiO₂ (referred hereafter as TAT) multilayer films with nitrogen implantation is reported. In the present work, TAT films were fabricated with a total thickness of 100 nm by sputtering on glass substrates at room temperature. The as-deposited films were implanted with 40 keV N ions for different fluences (1×10¹⁴, 5×10¹⁴, 1×10¹⁵, 5×10¹⁵ and 1×10¹⁶ ions/cm²). The objective of this study was to investigate the effect of N⁺ implantation on the optical and electrical properties of TAT multilayer films. X-ray diffraction of TAT films shows an amorphous TiO₂ film with a crystalline peak assigned to Ag (111) diffraction plane. The surface morphology studied by atomic force microscopy (AFM) and field emission scanning electron microscope (FESEM) revealed smooth and uniform top layer of the sandwich structure. The surface roughness of pristine film was 1.7 nm which increases to 2.34 nm on implantation for 1×10¹⁴ ions/cm² fluence. Beyond this fluence, the roughness decreases. The oxide/metal/oxide structure exhibits an average transmittance ~80% for pristine and ~70% for the implanted film at fluence of 1×10¹⁶ ions/cm² in the visible region. The electrical resistivity of the pristine sample was obtained as 2.04×10⁻⁴ Ω cm which is minimized to 9.62×10⁻⁵ Ω cm at highest fluence. Sheet resistance of TAT films decreased from 20.4 to 9.62 Ω/□ with an increase in fluence. Electrical and optical parameters such as carrier concentration, carrier mobility, absorption coefficient, band gap, refractive index and extinction coefficient have been calculated for the pristine and implanted films to assess the performance of films. The TAT multilayer film with fluence of 1×10¹⁶ ions/cm² showed maximum Haacke figure of merit (FOM) of 5.7×10⁻³ Ω⁻¹. X-ray photoelectron spectroscopy (XPS) analysis of N 1s and Ti 2p spectra revealed that substitutional implantation of nitrogen into the TiO₂ lattice added new electronic states just above the valence band which is responsible for the narrowing of band gap resulting in the enhancement in electrical conductivity. This study reports that fabrication of multilayer transparent conducting electrode with nitrogen implantation that exhibits superior electrical and optical properties and hence can be an alternative to indium tin oxide (ITO) for futuristic TCE applications in optoelectronic devices.     

ZnMgBeO/Ag/ZnMgBeO transparent multilayer films with UV energy bandgap and very low resistance

The ZnMgBeO/Ag/ZnMgBeO multilayer structures were sputter grown and their electrical and optical properties have been investigated in detail. Results indicated that the ZnMgBeO(30 nm)/Ag(10 nm)/ZnMgBeO(30 nm) optimum structure shows energy bandgap of ~4.5 eV, electrical resistivity of ~6.5×10⁻⁵ Ωcm, and optical transmittance of 78–90% over the visible wavelength range and 74–90% over 300–400 nm range, representing a significant improvement over the previously reported transparent conducting films. High resistivity (~0.12 MΩcm) of the ZnMgBeO layer did not critically affect the conductivity of the multilayer, because the Ag films act as the conducting path. It was also observed that the properties were substantially deteriorated at the Ag thickness of 5 nm, as the Ag film is only partly continuous, resulting in very rough interfaces and surfaces.     

Preparation and ionic conduction of CaZr1−xScxO3−α ceramics

A series of CaZr_1−xSc_xO_3−α (x=0, 0.05, 0.10, 0.15) perovskite oxide ceramics were successfully fabricated at 1400 °C for 10 h and then further sintered at 1650 °C for 10 h via a solid-state reaction sintering process. Conductivities of the ceramics were measured under the atmosphere that contains 1% H₂/Ar and 5.63 kPa H₂O/Ar by the electrochemical impedance spectra technique. It was found that the conductivities of CaZr_1−xSc_xO_3−α (x=0, 0.05, 0.10, 0.15) ceramics increased with the increase of the measuring temperature, and the conductivity achieved its maximum value of 2.03×10⁻⁵–6.5×10⁻³ S cm⁻¹ when the doping amount of Sc (x) was 0.10. Additionally, element doping can increase the conductivities and decrease the conductivity activation energies of CaZr_1−xSc_xO_3−α ceramics. The results of transport number measurement indicated that the CaZr_0.9Sc_0.1O_3−α is almost a pure protonic conductor at 500–750 °C, while it is a mixed protonic-oxygen ionic-electronic conductor at 750–1300 °C.     

Preparation of dual-phase composite BaCe0.8Y0.2O3/Ce0.8Y0.2O2 and its application for hydrogen permeation

Dual-phase ceramic membranes composed of BaCe_0.8Y_0.2O₃ (BCY) and Ce_0.8Y_0.2O₂ (CYO) were successfully synthesized by solid state reaction method for hydrogen permeation. The influences of the BCY/CYO volume ratios on phase composition, microstructure, chemical stability and electrical property were investigated. The hydrogen permeation of the dual-phase composite was characterized as a function of temperature and feed side hydrogen partial pressure. The results showed that there was no reaction between the two constituent oxides observed under the preparation conditions. The dual-phase composite with different BCY/CYO volume ratios after sintering at 1550 °C exhibited dense structure, as well as good stability in 4% H₂/Ar, wet Ar and pure CO₂ atmosphere. The conductivity of the dual-phase composite increased with the content of CYO increasing and 30BCY–70CYO exhibited the highest total conductivity of 2.6×10⁻² S cm⁻¹ at 800 °C in 4% H₂/Ar. The hydrogen permeability of 30BCY–70CYO sample was improved as the temperature and the hydrogen partial pressure in feed gas increased. The hydrogen permeation flux of 1.7 μmol cm⁻² s⁻¹ was achieved at 850 °C.     

Deposition of highly oriented lanthanum nickel oxide thin film on silicon wafer by CSD

This paper describes the orientation control and the electrical properties of the chemical solution deposition (CSD) derived LaNiO₃ (LNO) thin film. The LNO precursor solutions were prepared using lanthanum nitrate and nickel acetate as La and Ni source, and ethanol or 2-methoxyethanol and 2-aminoethanol mixed solution as solvents. The LNO films were spin-coated using these precursor solutions and annealed at the temperature from 500 to 700 °C. The resulting LNO film annealed at 700 °C derived from 2-methoxyethanol and 2-aminoethanol mixed solvent exhibited (1 0 0)-orientation, with some surface cracks and pores, and relatively higher resistivity of 2.49 × 10⁻³ Ω cm. The LNO film derived from 2-methoxyethanol and 2-aminoethanol mixed solvent annealed at 700 °C in an oxygen atmosphere showed highly (1 0 0)-orientation, with higher density, a few cracks and pores, and exhibited a good electrical resistivity of 7.27 × 10⁻⁴ Ω cm.     

Highly conductive SiC ceramics containing Ti2CN

Highly conductive SiC ceramics were fabricated by sintering β-SiC and TiN powder mixture in N₂ atmosphere. SiC ceramics exhibited decreased electrical resistivity (ρ) with increasing TiN content. X-ray diffraction data indicated that the specimens consisted of β-SiC grains without a detectible secondary phase for low TiN content (≤2 vol%) but contained a Ti₂CN phase as the TiN content increased. The temperature-dependent resistivity ρ(T) of specimens revealed semiconductor-like behavior for TiN content up to 10 vol% and metal-like behavior above 20 vol%. For the specimen with TiN content of 15 vol%, ρ(T) remained almost constant (2.06 ± 0.01 × 10⁻³ Ω cm) in the 4–300 K range. The resistivity of metal-like specimens were as low as 3.5 × 10⁻⁴ Ω cm for TiN content of 20 vol%. For semiconductor-like specimens, ρ(T) was primarily affected by N donors in the β-SiC grains. Metal-like specimens were primarily affected by metallic Ti₂CN clusters.