Effects of ultrasound on perovskite phase developments, microstructures, and dielectric properties of sol-gel-processed PbTiO3 thin films

PbTiO₃ thin films were prepared by spin coating of untreated and sonicated sol (from Pb-Ti stock solution) on Si substrates. The films were fired at different temperatures and were analyzed by scanning electron microscopy, X-ray diffraction and atomic force microscopy. Dried gel and thin films prepared through the two different processing routes were compared in terms of phase developments, microstructures, and dielectric properties. Films prepared from the sonicated sol were found to be superior than those from the untreated sol.     

Study on chemical vapor deposited copper films on cyano and carboxylic self-assembled monolayer diffusion barriers

Thin copper films were produced by chemical vapor deposition using the precursor Cu^IIbis-hexafluoroacetylacetonate on the SiO₂/Si substrate modified with cyano and carboxylic self-assembled monolayers (SAMs) as diffusion barriers. The characterizations of the deposited copper films were measured by various thin film analysis techniques, i.e., scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy and X-ray diffraction. The comparison between copper deposited on SiO₂ and on the SAM-modified SiO₂ substrates indicates that the copper films tend to be deposited onto the SAM-modified substrate, which is further proved by the calculation results of the interaction energies of copper and the SAMs with density functional theory method.     

Development of crystallinity and morphology in hafnium dioxide thin films grown by atomic layer epitaxy

The structural development of HfO₂ thin films grown from HfCl₄ and water onto glass substrates by atomic layer epitaxy at 500 °C was studied with X-ray diffraction, atomic force microscopy and scanning electron microscopy. The films were found to contain two regions of different crystallinity: a thin amorphous starting layer and a subsequent preferentially oriented polycrystalline layer. The films were built up of densely packed grains. Substantial surface roughening occurred along with increasing film thickness. The films were chlorine free as analyzed by Rutherford backscattering spectrometry.     

Optimizing growth conditions for electroless deposition of Au films on Si(111) substrates

Electroless deposition of Au films on Si(111) substrates from fluorinated-aurate plating solutions has been carried out at varying concentrations, deposition durations as well as bath temperatures, and the resulting films were characterized by X-ray diffraction, optical profilometry, atomic force microscopy and scanning electron microscopy. Depositions carried out with dilute plating solutions (< 0.1 mM) at 28°C for 30 min produce epitaxial films exhibiting a prominent Au(111) peak in the diffraction patterns, while higher concentrations or temperatures, or longer durations yield polycrystalline films. In both epitaxial and polycrystalline growth regimes, the film thickness increases linearly with time, however, in the latter case, at a rate an order of magnitude higher. Interestingly, the surface roughness measured using atomic force microscopy shows a similar trend. On subjecting to annealing at 250°C, the roughness of the film decreases gradually. Addition of poly (vinylpyrrolidone) to the plating solution is shown to produce a X-ray amorphous film with nanoparticulates capped with the polymer as evidenced by the core-level photoelectron spectrum. Nanoindentation using AFM has shown the hardness of the films to be much higher (∼ 2.19 GPa) than the bulk value.     

Microstructural and transport properties of LaNiO3−δ films grown on Si (111) by chemical solution deposition

Electrically conductive LaNiO_3−δ (LNO) thin films with typical thickness of 200 nm were deposited on Si (111) substrates by a chemical solution deposition method and heat-treated in air at 700 °C. Structural, morphological, and electrical properties of the LNO thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), field-emission scanning electron microscopy (FEG-SEM), and electrical resistivity ρ(T). The thin films have a very flat surface and no droplet was found on their surfaces. The average grain size observed by AFM and FEG-SEM was approximately 100 nm in excellent agreement with XRD data. The ρ(T) data showed that these thin films display a good metallic character in a large range of temperature. These results suggest the use of this conductive layer as electrode in the integration of microelectronic devices.     

Development of smooth CuInGa precursor films for CuIn1 − xGaxSe2 thin film solar cell applications

CuInGa precursor thin films were deposited using a CuGa (75-25 at.%) and an In 3″ diameter target material simultaneously by RF magnetron sputtering. The precursor films were deposited on Si and glass substrates at − 80 °C and room temperature, and characterized by Rutherford backscattering spectroscopy, Auger electron spectroscopy, scanning electron microscopy, atomic force microscopy and X-ray diffraction. The effects of gun power density and substrate temperatures on resulting precursor film properties were investigated. Precursor films deposited at − 80 °C have a smooth morphology with a 75% reduction in all roughness values and are more dense and homogeneous in structure compared to precursors deposited at room temperature. Therefore these precursors will result in better selenization process reproducibility.     

Enhanced field emission characteristics of nitrogen-doped carbon nanotube films grown by microwave plasma enhanced chemical vapor deposition process

Nitrogen-doped carbon nanotube (CNT) films have been synthesized by simple microwave plasma enhanced chemical vapor deposition technique. The morphology and structures were investigated by scanning electron microscopy and high resolution transmission electron microscopy. Morphology of the films was found to be greatly affected by the nature of the substrates. Vertically aligned CNTs were observed on mirror polished Si substrates. On the other hand, randomly oriented flower like morphology of CNTs was found on mechanically polished ones. All the CNTs were found to have bamboo structure with very sharp tips. These films showed very good field emission characteristics with threshold field in the range of 2.65-3.55 V/μm. CNT film with flower like morphology showed lower threshold field as compared to vertically aligned structures. Open graphite edges on the side surface of the bamboo-shaped CNT are suggested to enhance the field emission characteristics which may act as additional emission sites.     

氨化Si基Ga2O3/In制备GaN薄膜

研究了Ga2O3/In 膜反应自组装制备GaN薄膜,再将Ga2O3/In膜在高纯氨气气氛中氨化反应得到GaN薄膜,用X射线衍射(XRD),傅里叶红外吸收(FTIR),扫描电镜(SEM),原子力显微镜(AFM),透射电镜(TEM)对样品进行结构,形貌的分析.测试结果表明:用此方法得到了六方纤锌矿结构的GaN多晶膜,且900℃时成膜的质量最好.     

Influence of Sputtering Gas on Morphological and Optical Properties of Magnesium Films

The influence of sputtering gas(He & Ar) on the structural properties of Mg thin films has been investigated.The optical property(reflectance) that results from the growth of films at varying substrate temperatures(Tsub) was also studied.The deposited films were characterized by using X-ray diffraction(XRD),field emission scaning electron microscopy(FE-SEM),atomic force microscopy(AFM) and UV-Vis-NIR spectrophotometer.The smaller crystallite size and lower deposition rate were observed in the presence of Helium atmosphere compared to Argon.Morphology of the films shows 2D hexagonal geometry of grains in the deposition temperature range(Tsub≈50-150℃) in both the sputtering gases.The surface roughness of the polycrystalline films were found to increase with increase in the deposition temperature of both ambient gases.Optical reflectance of Mg films was measured in near infrared region and larger reflectance was observed from Mg films sputtered in He atmosphere compared to that in argon.     

Influence of sputtering parameters and nitrogen on the microstructure of chromium nitride thin films deposited on steel substrate by direct-current reactive magnetron sputtering

Chromium nitride thin films were deposited on SA-304 stainless steel substrates by using direct-current reactive magnetron sputtering. The influence of process conditions such as nitrogen content in the fed gas, substrate temperature, and different sputtering gases on microstructural characteristics of the films was investigated. The films showed (200) preferred orientation at low nitrogen content (< 30%) in the fed gas. The formation of Cr₂N and CrN phases was observed when 30% and 40% N₂ were used, with a balance of Ar, respectively. Field emission scanning electron microscopy and atomic force microscopy were used to characterize the morphology and surface topography of the thin films, respectively. Microhardness tests showed a maximum hardness of 16.95 GPa for the 30% nitrogen content.     

Control of morphology and optical properties of PbS nanostructured thin films by deposition parameters: study of mechanism

PbS thin films were grown on glass substrates by chemical bath deposition (CBD) using lead nitrate, thiourea and sodium hydroxide in aqueous solutions at three different temperatures (22, 36 and 50?°C). The microstructure and morphology evolution of the films were investigated using X-ray diffraction, scanning electron microscopy and atomic force microscopy. Optical properties were studied using UV–Vis–IR spectroscopy. The results indicate that temperature plays an important role in controlling the morphology and optical properties of nanostructured PbS thin films through changing deposition mechanism. The active deposition mechanism changed from cluster to ion-by-ion mechanism with an increase in deposition temperature from 22 to 50?°C, and consequently, film properties such as morphology, optical absorption and preferred orientation changed completely.     

Influence of thermal annealing on microstructural,morphological, optical properties and surface electronic structure of copper oxide thin films

In this study, effect of the post-deposition thermal annealing on copper oxide thin films has been systemically investigated. The copper oxide thin films were chemically deposited on glass substrates by spin-coating. Samples were annealed in air at atmospheric pressure and at different temperatures ranging from 200 to 600°C. The microstructural, morphological, optical properties and surface electronic structure of the thin films have been studied by diagnostic techniques such as X-ray diffraction (XRD), Raman spectroscopy, ultraviolet–visible (UV–VIS) absorption spectroscopy, field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The thickness of the films was about 520 nm. Crystallinity and grain size was found to improve with annealing temperature. The optical bandgap of the samples was found to be in between 1.93 and 2.08 eV. Cupric oxide (CuO), cuprous oxide (Cu₂O) and copper hydroxide (Cu(OH)₂) phases were observed on the surface of as-deposited and 600 °C annealed thin films and relative concentrations of these three phases were found to depend on annealing temperature. A complete characterization reported herein allowed us to better understand the surface properties of copper oxide thin films which could then be used as active layers in optoelectronic devices such as solar cells and photodetectors.     

Transformation of the buffer layer grown on 4H-SiC to single-layer graphene by ex situ hydrogen intercalation

Abstract

The buffer layer samples grown on the Si-face of the 4H- and 6H-SiC substrates were heated in a hydrogen flow at different temperatures (600–900?°C) and heating times (40–60?min) in order to obtain quasi-freestanding monolayer graphene. Their structural properties were characterized before and after heating by using the methods of Raman spectroscopy, atomic force microscopy, Kelvin probe force microscopy, and low-energy electron diffraction. The dependence of the degree of coverage of the sample with quasi-freestanding graphene and the number of defects in the resulting films on the heating temperature was studied. As a result of optimization of the technological parameters, it is shown that the highest quality of the resulting quasi-freestanding graphene can be achieved by using the following parameters: heating time of 40?minutes and temperature of 800?°C.     

Surface topography and hydrogen sensor response of APCVD grown multilayer graphene thin films

Atmospheric pressure chemical vapour deposition was employed to deposit graphene thin films on thermally oxidized p-silicon substrates. Raman spectroscopy and energy dispersive spectroscopy revealed the multilayer nature and the composition of the grown graphene films respectively. The defective nature and the defect density of the graphene films were determined from the Raman experiments. Field effect scanning electron microscopy, transmission electron microscopy and atomic force microscopy were used to study the surface morphology of the multilayer graphene films. The film topography was sensitive to temperature and time of growth. A suitable growth mechanism has been proposed to explain the topographical observations. The large surface area of the multilayer films was found to be suitable for hydrogen sensor applications and the sensing results were correlated with the morphology of the grown films.     

Nanosecond UV laser graphitization and delamination of thin tetrahedral amorphous carbon films with different sp/sp content

We have produced hydrogen-free tetrahedral amorphous carbon films with different densities and Young's modulus by coating silicon with a filtered vacuum arc under different angles. The films were modified with a pulsed laser (wavelength 355 nm) into sp² rich amorphous carbon and nano crystalline carbon films. The graphitization threshold of the films depends on the film thickness as well as on the carbon density. Simulations of the optical absorption of the different carbon films permitted to confirm the experimental results. On the other side, the delamination threshold of carbon films increases with the film thickness and was found to be controlled by thermal properties of the film. The thin film graphitization and delamination is investigated by optical microscopy, atomic force microscopy, scanning electron microscopy and Raman spectroscopy.     

Structural characterization of CdS thin film on quartz formed by femtosecond pulsed laser deposition at high temperature

CdS thin films have been grown on quartz substrates using femtosecond pulsed laser deposition. The structural and optical properties of the CdS thin films were characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. The results indicate that the compositional segregation of the CdS films could be drawn from the selective evaporation of sulfur from the film surface as a result of heating up the substrates. Growth temperature played an important role on changing crystal structure and optical properties of the CdS films.     

Effects of ceria nanoparticle concentrations on the morphology and corrosion resistance of cerium–silane hybrid coatings on electro-galvanized steel substrates

This work investigates the effect of the ceria nanoparticle concentration on the morphology and electrochemical behavior of cerium–silane hybrid coatings deposited on electro-galvanized steel substrates. The substrates were pre-treated with 3-glycidoxypropyl-trimethoxysilane and bisphenol A, modified with cerium ion-activated CeO₂ nanoparticles. The morphology of the coating before and after corrosion tests was examined using atomic force microscopy and scanning electron microscopy. The results indicate the formation of nanostructured surfaces with relatively uniform thicknesses and nanoparticle distribution. Microscopic observations explain the increased durability of the silane coating doped with the lowest content of activated ceria nanoparticles after short-term corrosion tests (456 h). The corrosion behavior of the sol–gel coatings was also investigated using natural salt spray tests, electrochemical impedance spectroscopy, and potentiodynamic polarization tests. The results show that the concentration of nanoparticles has a significant impact on the barrier properties of the silane films, which are improved for films with lower nanoparticle contents.     

Morphology and microstructure of textured SnO2 thin films obtained by spray pyrolysis and their effect on electrical and optical properties

Tin dioxide thin films on glass substrate with different Zn doping levels were obtained by spray pyrolysis. Their microstructure, preferred crystallographic orientation, electrical and optical properties were extensively studied. The characterization techniques employed were scanning electron microscopy, transmission electron microscopy, atomic force microscopy, X-ray diffraction, electrical conductivity and optical transmission measurements. It was found that the material obtained has a nano-scale texture which characteristic size and orientation strongly depend on the Zn doping level. Doping-induced variations in texture and structure modify both the electrical and optical properties of films (namely, refractive index and transparency). The results obtained are relevant for potential applications of the studied films in gas sensing and photoconductive devices.     

A study of size dependent structure, morphology and luminescence behavior of CdS films on Si substrate

Size tunable cadmium sulfide (CdS) films deposited by a dip coating technique on silicon (100) and indium tin oxide/glass substrates have been characterized using X-ray diffraction, X-ray reflectivity, transmission electron microscopy, atomic force microscopy and photoluminescence spectroscopy. The structural characterization indicated growth of an oriented phase of cadmium sulfide. Transmission electron microscopy used to calculate the particle size indicated narrow size dispersion. The tendency of nanocrystalline CdS films to form ordered clusters of CdS quantum dots on silicon (100) substrate has been revealed by morphological studies using atomic force microscopy. The photoluminescence emission spectroscopy of the cadmium sulfide films has also been investigated. It is shown that the nanocrystalline CdS exhibit intense photoluminescence as compared to the large grained polycrystalline CdS films. The effect of quantum confinement also manifested as a blue shift of photoluminescence emission. It is shown that the observed photoluminescence behavior of CdS is substantially enhanced when the nanocrystallites are assembled on silicon (100) substrate.     

Pulsed Laser Deposition of YBa2Cu3O7 Superconducting Film on MgO Templates Spray Pyrolyzed on Hastelloy C276

Pulsed laser deposition (PLD) was used to deposit YBCO on MgO-buffered C276 substrates in order to evaluate the quality of the deposited MgO films which were deposited by spray pyrolysis. The characterization of the thin films was done using scanning electron microscopy, atomic force microscopy, electron backscattered diffraction, X-ray diffraction 2??-scans, rocking curve (??-scans), phi scan, pole-figure measurements, and AC susceptibility. It was found that c-axis oriented YBCO films were grown on c-axis oriented MgO films which confirm that the deposited YBCO films copied the out-of-plane texture of the spray pyrolyzed MgO buffer. However, MgO and YBCO films have a very weak in-plane texture. The AC susceptibility measurements show that the YBCO films have a broad superconducting transition temperature which may be attributed to the weak in-plane texture.