Effect of growth temperature on properties of transparent conducting gallium-doped ZnO films

Transparent conducting gallium-doped ZnO films are deposited on glass substrates by magnetron sputtering of conducting ceramic targets. The dependences of structural, electric, and optical characteristics of ZnO:Ga films on the substrate temperature are investigated during the deposition. Stability of resistivity of films is considered during annealing in air. It is found that the films deposited at the substrate temperature of 250°C have the lowest resistivity of 3.8 × 10⁻⁴ Ω cm, while those deposited at 200°C have the highest thermal stability.     

Highly transparent and conducting zinc oxide films deposited by activated reactive evaporation

Highly transparent and conducting undoped zinc oxide films have been obtained with a best resistivity of ～1.1 × 10^-3 Ω cm, a carrier density of ～1.5 × 10²⁰ cm^?3 and a mobility of ～38 cm²V^{?1s ?1}. These were produced by activated reactive evaporation at a deposition rate of 2 to 8Å/s with a substrate temperature ≤200° C. The films deposited by this process were found to have resistivities that were thickness independent and also were relatively insensitive to deposition parameters. In terms of conductivity, it was found that films deposited at higher temperatures (T > 300°+ C) were always inferior to the films deposited below 200° C. High temperature vacuum annealing (350° C) significantly degraded the resistivity of the undoped films deposited at low temperature; this was attributable to a drop in both the electron concentration and the mobility. Aluminum doping was found to be able to stabilize the electron concentration while the drop in mobility was found to be related to the choice of substrate.     

The effect of post-deposition thermal processing on MOS gate oxides formed by remote PECVD

The effects of post-deposition thermal exposure, at temperatures typical of MOS fabrication processes, on gate oxides formed by remote plasma enhanced chemical vapor deposition (RPECVD) is discussed. SiO₂ films were prepared by (1) thermal oxidation of silicon at temperatures from 700 to 1150° C, and (2) by RPECVD at a substrate temperature of 350° C. Post deposition thermal processing was achieved by rapid thermal annealing for 100 sec from 850–1200° C. Film properties were studied by infrared spectroscopy (IR), ellipsometry, and by measurements of stress, capacitance voltage characteristics, and dielectric breakdown. Post-formation, thermal processing in the range of 850–1200° C was shown to modify both thermally grown and deposited oxides, but it has been shown that RPECVD films could be stabilized against post-deposition changes by rapid thermal annealing at temperatures of about 900° C for periods of at least 100 sec.     

Effect of post deposition heat treatment on microstructure parameters,optical constants and composition of thermally evaporated CdTe thin films

Thin film microstructure and its properties can be effectively altered with post deposition heat treatments. In this respect, CdTe thin films were deposited on glass substrates at a substrate temperature of 200 °C using thermal evaporation technique, followed by air annealing at different temperatures from 200 to 500 °C. Structural analysis reveals that CdTe thin films have a cubic zincblend structure with two oxide phases related to CdTe₂O₅ and CdTeO₃ at annealing temperature of 400 and 500 °C respectively. Regardless of the annealing temperature, the plane (111) was found to be the preferred orientation for all films. The crystallite size was observed to increase with annealing temperature. All films were found to display higher lattice parameters than the standard, and hence found to carry a compressive stress. Optical measurements suggest high uniformity of films both before and after post deposition heat treatment. Films annealed at 400 °C displayed superior optical properties due to its high refractive index, optical conductivity, relative density and low disorder. Furthermore, according to the compositional measurements, CdTe thin films were found to exhibit Te rich and Cd rich nature at regions near the substrate and center of the film respectively, for all annealing temperatures. However, composition of the regions near the substrate was found to become more Te rich with increasing annealing temperature. The study suggests that changing the annealing temperature as a post deposition treatment affects structural and optical properties of CdTe thin film as well as its composition. According to the observations, films annealed at 400 °C can be concluded to be the best films for photovoltaic applications due to its superior optical and structural properties.     

Optical and electrical properties of nickel oxide thin films synthesized by sol–gel spin coating

Nickel oxide thin films were prepared by the sol–gel technique combined with spin coating onto glass substrates. The as-deposited films were pre-heated at 275 °C for 15 min and then annealed in air at different temperatures. The effects of the annealing temperature on the structural and optical properties of the films are studied. The results show that 600 °C is the optimum annealing temperature for preparation of NiO films with p-type conductivity and high optical transparency. Then, by using these optimized deposition parameters, NiO thin films of various thicknesses were deposited at the same experimental conditions and annealed under different atmospheres. Surface morphology of the films was investigated by atomic force microscopy. The surface morphology of the films varies with the annealing atmosphere. Optical transmission was studied by UV–vis spectrophotometer. The transmittance of films decreased as the thickness of films increased. The electrical resistivity, obtained by four-point probe measurements, was improved when NiO layers were annealed in N₂ atmosphere at 600 °C.     

Low-temperature growth of RuO2 films for conductive electrode applications

Conductive ruthenium oxide films are considered as possible candidate for electrodes in complementary metal oxide semiconductor and random-access memory applications. We have succeeded in growth of highly conducting RuO₂ films by metal organic chemical vapour deposition on silicon substrates at deposition temperatures between 250°C and 500°C. Structural and electrical properties of the films were studied as a function of deposition temperature. Room temperature resistivity of the films increased from 40 μΩcm for the deposition temperature 500°C to above 100 μΩcm for the deposition temperature 250°C. The films prepared at temperatures below 300°C exhibit smooth surface and excellent step coverage. These films could be used in the above-mentioned applications.     

Formation and study of buried SiC layers with a high content of radiation defects

Protons with energy E=100 keV were implanted with doses ranging from 2×10¹⁷ to 4×10¹⁷ cm^?2 into 6H-and 4H-SiC n-type samples at room temperature. The samples were subjected to various types of postimplantation heat treatment in the temperature range 550–1500°C. The parameters of the samples were studied by measuring the capacitance-voltage and current-voltage characteristics and by analyzing the photoluminescence spectra. Blistering on the surface of the sample is observed after annealing the samples at a temperature of 800°C only after implantation of protons with a dose of ≤3×10¹⁷ cm^?2. A decrease in the resistivity of the compensated layer sets in after annealing at a temperature of ～1200°C and is completed after annealing at a temperature of ～1500°C. A drastic decrease in the photoluminescence intensity is observed after implantation for all types of samples. Recovery of the photoluminescence intensity sets in after annealing at temperatures ≥800°C and is complete after annealing at a temperature of 1500°C.     

Effect of annealing temperature on structural,electrical and optical properties of spray pyrolytic nanocrystalline CdO thin films

Nanocrystalline CdO thin films were prepared onto a glass substrate at substrate temperature of 300 °C by a spray pyrolysis technique. Grown films were annealed at 250, 350, 450 and 550 °C for 2.5 h and studied by the X-ray diffraction, Hall voltage measurement, UV-spectroscopy, and scanning electron microscope. The X-ray diffraction study confirms the cubic structure of as-deposited and annealed films. The grain size increases whereas the dislocation density decreases with increasing annealing temperature. The Hall measurement confirms that CdO is an n-type semiconductor. The carrier density and mobility increase with increasing annealing temperature up to 450 °C. The temperature dependent dc resistivity of as-deposited film shows metallic behavior from room temperature to 370 K after which it is semiconducting in nature. The metallic behavior completely washed out by annealing the samples at different temperatures. Optical transmittance and band gap energy of the films are found to decrease with increasing annealing temperature and the highest transmittance is found in near infrared region. The refractive index and optical conductivity of the CdO thin films enhanced by annealing. Scanning electron microscopy confirms formation of nano-structured CdO thin films with clear grain boundary.     

Amorphous chromium silicide formation in hydrogenated amorphous silicon

The interaction between thin films of hydrogenated amorphous silicon and sputter-deposited chromium has been studied. Following deposition of the chromium films at room temperature, the films were annealed over a range of times and temperatures below 350°C. It was found that an amorphous silicide was formed only a few nanometers thick with the square of thickness proportional to the annealing time. The activation energy for the process was 0.55±0.05 eV. The formation process of the silicide was very reproducible with the value of density derived from the thickness and Cr surface density being close to the value for crystalline CrSi₂ for all films formed at temperatures ≤300°C. The specific resistivity of the amorphous CrSi₂ was ≈600 μΩ·cm and independent of annealing temperature.     

Investigations about the effect of annealing temperatures in the presence of oxygen flow on optical and electronic properties of titanium nano-layers by using Kramers–Kronig and DFT methods

Nano-layers of titanium were deposited on glass substrates by resistive evaporation at room temperature. Thickness of the layers was measured 66.8 nm, by a quartz crystal method. Deposition conditions such as deposition rate, vacuum pressure, incidence of angle and substrate temperature were the same for all layers. After producing pure Ti layers a post-annealing method was used in the presence of a uniform oxygen flow of 6 cm³/s and different 100 °C, 200 °C and 300 °C annealing temperatures. Optical reflectance and transmittance of the layers were measured in the wave length of 200–4100 nm by a spectrophotometer. Kramers–Kronig relations were used to calculate the optical constants. The influence of annealing temperature and oxygen flow on optical properties is investigated. Also to make the obtained optical results clearer, a full-potential linearized augmented plane wave (FP-LAPW) method within the generalized gradient approximation (GGA) has been used. Comparison results confirm that in higher annealing temperatures the obtained structure is more similar to anatase crystalline one. According to AFM images, by increasing annealing temperature in the presence of oxygen flow, configuration of layers change and due to high annealing temperature and surface diffusion effect, void fraction increases. With increase in annealing temperature to 300 °C, anatase phase structure (A(004)) gets clearer and sharper also other phase structures are about to grow.     

Preparation of PbTiO3 thin films by plasma enhanced MOCVD and the effect of rapid thermal annealing

Dielectric PbTiO₃-thin films were prepared on p-Si(100) substrate by plasma enhanced metalorganic chemical vapor deposition using high purity Ti(O-i-C₃H₇)₄, Pb(tmhd)₂, and oxygen. As-deposited films were post-treated by rapid thermal annealing method, and the effect of annealing was examined under various conditions. The deposition process was controlled by mixed-control scheme at temperatures lower than 350°C, but controlled by heterogeneous surface reaction at temperatures greater than 350°C. The as-deposited films showed PbO structure at 350∼400°C, but (100) and (101) PbTiO₃ orientations started to appear at 450°C. The deposition rate was increased with rf power due to the enhanced dissociation of Ti and Pb precursors. It was found that the concentration of oxygen plays an important role in crystallization of PbTiO₃ during the rapid thermal annealing. A linear relationship was obtained between the dielectric constant of PbTiO₃ films and the annealing temperature. However, the surface roughness and leakage current density increased mainly due to the defects caused by volatilization of lead and the interface layer formed during the high temperature annealing.     

Dislocation-free undoped semi-insulating GaAs epilayers prepared by chloride chemical vapor deposition and successive wafer annealing

Dislocation-free (DF) undoped semi-insulating GaAs epilayers have been realized by chloride chemical vapor deposition and successive wafer annealing. It was found that undoped conductive DF GaAs epilayers grown on Si-doped n-type DF GaAs substrates can be converted to semi-insulating by wafer annealing at temperatures higher than 950°C. The resistivity of these semi-insulating epilayers was higher than 10⁷ Ωcm. The outdiffusion of Si from the substrate to the epilayer was analyzed by secondary ion mass spectrometry and it was found that the thickness of the outdiffusion region was only 1μm.     

High conductivity copper-boron alloys obtained by low temperature annealing

The electrical behavior during annealing of copper films with a nominal concentration of 2 at.% boron has been investigated. The evolution of the resistivity of the film was monitored using an in situ technique, in which the film was rampannealed at constant ramp rates. At temperature of 150–200°C, the resistivity of the Cu(B) undergoes a first drop. This is followed by one or two such drops in resistivity, so that after completion of a ramp-anneal from 50°C to 750°C, the room temperature resistivity decreases from the initial value of 13 μΩ cm to 2.1 μΩcm, close to that of bulk copper. Isothermal annealing of the film also leads to substantial decreases in resistivity, from 13 μΩcm to 3 μΩ cm after annealing at 350°C for 8 h and to 2.5 μΩ cm at 400°C for 4 h. These results show that a dramatic reduction in resistivity of Cu(B) alloys takes place at temperatures below 400°C, suggesting possible applications for silicon device interconnections.     

Low-Temperature Synthesis of High-Adhesion Cu(Mg) Alloy Films on Glass Substrates

Cu(0.5 at.%Mg) alloy films were deposited on glass substrates, and annealed at 200–400 °C in vacuum. The resistivity of the Cu(Mg) films was reduced to about 3.0 μΩcm after annealing at 200 °C for 30 min, and the tensile strength of adhesion of the Cu(Mg) films to the glass substrates was increased to 30–40 and 35–55 MPa after annealing at 250 and 300 °C, respectively. The reduction in resistivity can be explained as reduced impurity scattering and grain-boundary scattering, since Mg segregation to the film surface and Cu(Mg)/glass interface, and consequent Cu grain growth, were observed. Increased adhesion of the Cu(Mg) films to glass substrates after annealing was also explained by the strong segregation of Mg atoms, and the formation of a reaction layer at the interface. Mg atoms were observed to have reacted with the glass substrates and formed a thin crystalline MgO layer at the interface in the samples annealed at 300 °C, while Mg atoms were highly concentrated above the Cu(Mg)/glass interface without oxide formation at the interface in the samples annealed at 250 °C. Thus, the process temperature and time to obtain low-resistivity and high-adhesion Cu alloy films on glass substrates could be reduced to 250 °C and 30 min using Cu(Mg) films.     

Effect of Temperature on Structural and Morphologic Properties of ZnO Films Annealed in Ammonia Ambient

ZnO thin films were prepared on Si(111) substrates by pulsed laser deposition (PLD). Then, the samples were annealed at different temperatures in NH₃ ambient and their properties were investigated particularly as a function of annealing temperature. The structure, morphology, and optical properties of ZnO films were studied by x-ray diffraction (XRD), Fourier transform infrared spectroscope (FTIR), scanning electron microscope (SEM), and photoluminescence (PL). The results show that the increase of annealing temperature makes for the improvement in the crystal quality and surface morphology below the temperature of 650°C. However, when the annealing temperature is above 650°C, the ZnO films will volatilize and, especially at 750°C, ZnO will volatilize completely.     

Electrical Properties of Isotropic Conductive Adhesives Composed of Silicone-Based Elastomer Binders Containing Ag Particles

The electrical properties of isotropic conductive adhesives (ICAs) with two different types of silicone-based binder containing Ag particles were examined. The ICAs were printed on glass substrates in order to prepare specimens for evaluating the electrical properties. In the case of adhesives containing a denatured silicone binder, both the curing and cooling steps in the isothermal curing process generated electrical conductivity. Adhesives that were cured at 120°C to 200°C exhibited similar values of electrical resistivity regardless of the different curing temperatures. By contrast, electrical conductivity was generated only during the cooling step when adhesives containing a dimethyl methylvinyl siloxane were isothermally cured. In this case, adhesives cured above 160°C exhibited high electrical resistivity. In evaluating the temperature dependence of the electrical resistivity, we found physical annealing to have significantly different effects on these specimens. In addition, we were able to make small sensitive variations in the properties of silicone-based ICAs by controlling the isothermal annealing and thermal cycling processes.     

Microstructures of YSZ and CGO Thin Films Deposited by Spray Pyrolysis: Influence of Processing Parameters on the Porosity

Microstructures of yttria‐stabilized zirconia (YSZ) thin films deposited by spray pyrolysis at 370 °C on sapphire are investigated. The as‐deposited films are predominantly amorphous and crystallize upon heating at temperatures above 370 °C, developing grains in the range of 5 nm to several 100 nm. During post‐deposition heat treatment up to 800 °C, ～ 50 vol% porosity develops in the center of the films with gradients towards almost dense interfaces to the air and substrate. The reason for this porosity is the decomposition of residues from the precursor and the free volume liberated due to crystallization. Dense YSZ thin films consisting of one monolayer of grains are obtained with annealing temperatures exceeding 1200 °C. In gadolinium‐doped‐ceria (CGO) thin films similar microstructures and porosity are found after low‐temperature heat treatments indicating that the precursor residues due to the deposition method are the main cause of the porosity. Grain growth stagnation in annealed thin films is observed in both the YSZ and in CGO thin films. Stagnating grain growth in the thin films is rather caused by reduced grain boundary mobility, here predominately due to a “secondary phase”, i.e., pores, than to other effects. The stagnation ceases at higher annealing temperatures after densification has taken place.     

Structure and electrical properties of polycrystalline SiGe films grown by molecular beam deposition

The structural and electrical properties of polycrystalline Si_0.5Ge_0.5 films 150 nm thick grown by molecular beam deposition at temperatures of 200–550°C on silicon substrates coated with amorphous layers of silicon oxynitride were studied. It is shown that the films consist of a mixture of amorphous and polycrystalline phases. The amorphous phase fraction decreases from ～50% in films deposited at 200°C to zero in films grown at 550°C. Subsequent 1-h annealing at a temperature of 550°C results in complete solid-phase crystallization of all films. The electron transport of charge carriers in polycrystalline films occurs by the thermally activated mechanism associated with the energy barrier of ～0.2 eV at grain boundaries. Barrier lowering upon additional annealing of SiGe films correlates with an increase in the average grain size.     

The effects of incomplete annealing on the temperature dependence of sheet resistance and gage factor in aluminum and phosphorus implanted silicon on sapphire

The temperature coefficient of resistivity (TCR) of ion implanted silicon can be significantly reduced by partially annealing the crystal damage produced during implantation. The extent to which this method can be used to temperature compensate the resistivity and the gage factor has been determined for 300 ohm-cm silicon on sapphire implanted with either 100 keV Al²⁷ or P³¹ ions. The implantations were made at room temperature parallel to the 〈100〉 axis and in four fluences ranging from 1 × 10¹³cm^?2 to 1·25 × 10¹⁵ cm^?2. Sheet resistance, Hall coefficient, and effective mobility were measured from ?150°C to 150°C for various anneal temperatures. It was possible to obtain very low temperature dependences of sheet resistance at 300°K for all dopant fluences by appropriate partial annealing. On samples having the lowest temperature dependence of sheet resistance, the gage factor was measured from ?75°C to 75°C. The measurements were made along the 〈100〉 direction for phosphorus doped samples, and along the 〈110〉 direction for aluminum doped samples for all four fluences. The gage factor and its temperature dependence for these crystal orientations are not drastically affected by the crystal damage. These results are interpreted in terms of a model previously developed to explain the effect of electron damage on the temperature dependence of the resistivity and the piezoresistance of silicon.     

Nanostructured thin films of the La0.7Sr0.3MnO3 manganite obtained using the extraction pyrolytic method

The extraction pyrolytic method is used to fabricate thin (100–300 nm) films of the lanthanum manganites La_0.7Sr_0.3MnO₃ on fused silica substrates. The films are deposited on the substrate using the alternate sessions of the centrifuging of solution and pyrolysis. The annealing of thin films at temperatures of greater than 650°C yields the single-phase La_0.7Sr_0.3MnO₃ material. It is demonstrated that the annealing temperature substantially affects the magnetic properties of the resulting films: the films exhibit the properties of spin glasses and ferromagnetic properties at temperatures of less than 700°C and greater than 700°C, respectively.