Increasing Substrate Temperature Research Articles

Micromorphology of sputtered aluminum thin films: A fractal analysis

Abstract In this article, the surface analyses of topography, microstructure and mechanical behavior of Al thin films sputtered on glass are presented to understand the influence of varying low substrate temperatures at high radio-frequency (RF) power. The films were prepared by RF magnetron sputtering process at different substrate temperatures of 55°C, 65°C, and 95°C and at a constant RF power of 350 W. The topography, microstructure and mechanical properties were characterized by atomic force microscope (AFM), field emission scanning electron microscope (FESEM) and nanoindentation method respectively. The results revealed that at a higher substrate temperature of 95°C the microstructure consists of dense and globular dominant aluminum structures and higher interface width (roughness) as compared to the other temperatures. Nanoindentation results showed that films deposited at 95°C exhibited the highest values of average hardness and elastic moduli and a lowest maximum depth of displacement. A fractal analysis on the topography and surface microstructure revealed a decrease of the fractal dimension with the increase in substrate temperature and that the films exhibited a mono-fractal behavior at all the substrate temperatures investigated in the present study. A description based on the sputtering theory for the monofractal nature of the aluminum films is provided.

Ultra-high-density silicon nanocone arrays with sharp tips by Ar+ sputtering at low temperature

ABSTRACTUltra-high-density silicon nanocone arrays with sharp tips have been fabricated by Ar+ sputtering at low temperatures. The investigation of SEM and AFM indicates that with an increasing substrate temperature from room temperature, 200 to 400°C, the density of silicon nanocone increases from 1–2 × 109, 3–4 × 109 to 1–2 × 1010 cm−2, respectively. The rooter diameter of the cones decreases from 120–150 to 40–50 nm and the tip angle of cones decreases from 32–36° to 20–26°. As predicted by the Bradley–Harper theory, the ripple wavelength decreases with substrate temperature during the carbon ripple formation process, which leads to an increase in the silicon nanocone density and a decrease in the silicon nanocone rooter diameter.

Effect of deposition temperature on structural, optical and electrical properties of chemically deposited thermochromic Cu<SUB align="right">2HgI<SUB align="right">4 thin films

Copper mercury tetraiodide thin films were grown by the chemical bath deposition technique at different deposition temperatures varying from 300 K to 345 K. The structural properties of the prepared Cu2HgI4 thin films show that the Cu2HgI4 films have a polycrystalline nature. The compositional analysis confirmed the nearly stoichiometric structure of the deposited Cu2HgI4 thin films. Homogeneous and regular surface morphology, including of circular-shaped grains with a size range from 31 to 46 nm, was revealed. Thermal stability and phase transition were studied by means of thermogravimetric analysis (TGA) and differential thermal analysis (DSC), respectively. The effects of deposition temperature on the optical properties and D.C. electrical conductivity of the Cu2HgI4 films have been studied. The films were found to have an indirect optical energy gap of values increases with increasing substrate temperature. The electrical conductivity increases with increasing temperature according to grain boundary trapping model.

Effect of deposition temperature on structural, optical and electrical properties of chemically deposited thermochromic Cu<SUB align="right">2HgI<SUB align="right">4 thin films

Copper mercury tetraiodide thin films were grown by the chemical bath deposition technique at different deposition temperatures varying from 300 K to 345 K. The structural properties of the prepared Cu2HgI4 thin films show that the Cu2HgI4 films have a polycrystalline nature. The compositional analysis confirmed the nearly stoichiometric structure of the deposited Cu2HgI4 thin films. Homogeneous and regular surface morphology, including of circular-shaped grains with a size range from 31 to 46 nm, was revealed. Thermal stability and phase transition were studied by means of thermogravimetric analysis (TGA) and differential thermal analysis (DSC), respectively. The effects of deposition temperature on the optical properties and D.C. electrical conductivity of the Cu2HgI4 films have been studied. The films were found to have an indirect optical energy gap of values increases with increasing substrate temperature. The electrical conductivity increases with increasing temperature according to grain boundary trapping model.

Modeling Diffusion of Impurities in Molybdenum Thin Films as a Function of Substrate Temperature

Alkali ions are key to improving the performance of polycrystalline Cu(In,Ga)Se2 (CIGS) solar cells. Typically, a soda–lime glass substrate acts as an intrinsic source for many alkali ions. For these ions to reach the CIGS layer, diffusion through a metallic back contact is necessary. Typically deposited via sputtering, the morphology of this metallic back contact is dependent on multiple deposition parameters, including substrate temperature. By preparing films with varying deposition parameters, and utilizing both, multiple material characterizations (X-ray diffraction, scanning electron microscopy, and secondary ion mass spectrometry) and numerical modeling, we demonstrate here that effective paths of diffusion are just as important as diffusion rate for the alkali ions. As the substrate temperature increases, the mechanism that hinders the ability for alkali ions to diffuse switches effectively from diffusion rate to effective path of diffusion. It is shown that the lack of viable diffusion paths at substrate temperatures above 100 °C becomes the dominant factor for the transport of alkali ions.

Nanostructured and mechanical properties of high-entropy alloy nitride films prepared by magnetron sputtering at different substrate temperatures

ABSTRACT(AlCrNbSiTiV)N high-entropy alloy (HEA) nitride coatings have been grown on cermet tools inserts and glass substrates. Using reactive direct current magnetron sputtering with an equimolar AlCrNbSiTiV HEA target and Ar plasma and N2 reactive gases. In this study, the influence of (AlCrNbSiTiV)N coatings varied substrate temperature (room, 100, 200, 300, 400°C), on the structure, mechanical properties and cutting performance of the cermet cutting tools was investigated in dry machining of a SCM440 steel. The (AlCrNbSiTiV)N films coated was homogeneous, very compact and shows good adhesion strength (classified as HF1). The TEM image results indicate that the (AlCrNbSiTiV)N films are simple face-centre-cubic structures. As the substrate temperature increases, the films hardness increases, reaching the maximum value of 2493 HV at 100°C, and then decreases with further increase in the substrate temperature. The cutting performance improves when coated tools are used. The machined surface with the coated tool using a substrate temperature 100°C deposition parameters, show less surface defects and the tool flank wear is reduced.

Influence of the Initial Powder’s Specific Surface Area on the Properties of Sm-Doped Ceria Thin Films

The influence of a specific surface area of evaporating powder on the properties of thin Sm-doped cerium (SDC) oxide films has not yet been sufficiently investigated. Therefore, SDC films were deposited by e-beam evaporation using Sm0.2Ce0.8O2-δ powders of 6.2 m2/g, 11.3 m2/g, and 201.3 m2/g specific surface area on SiO2, and Al2O3 substrates. X-Ray Diffraction (XRD) analysis showed that SDC thin films deposited on 600 °C SiO2 substrates changed their preferred orientation from (111) to (311), (200), and (220) when evaporating 6.2 m2/g and 11.3 m2/g powders and using 0.2 nm/s, 1.2 nm/s, and 1.6 nm/s deposition rates. However, thin films deposited by evaporating powder of 201.3 m2/g specific surface area do not change their preferred orientation. The crystallite size of the SDC thin films depends on the substrate temperature and specific surface area of the evaporating powder. It increases from 6.40 nm to 89.1 nm with increasing substrate temperature (50–600 °C). Moreover, crystallites formed by evaporating a powder of 201.3 m2/g specific surface area are 1.4 times larger than crystallites formed by evaporating a powder of 6.2 m2/g specific surface area. An impedance analysis revealed that the normalized resistance of “grains” is higher than the normalized resistance of grain boundaries. Moreover, a total conductivity depends on crystallite size. It changes from 4.4 × 10−7 S/cm to 1.1 × 10−2 S/cm (600 °C) when the crystallite sizes vary from 6.40 nm to 89.10 nm. In addition, the optical band gap becomes wider with increasing crystallite size proving that the Ce3+ concentration decreases with an increasing crystallite size.

Substrate temperature-dependent properties of sprayed cobalt oxide thin films

Cobalt oxide (Co3O4) thin films were deposited onto amorphous glass substrates using a home-made pneumatic spray pyrolysis system (SPT) from aqueous solution of cobalt chloride salt (CoCl2) as a source of cobalt. The films were deposited at different substrate temperatures ranging from 250 to 450 °C in steps of 50 °C. The effect of substrate temperature on structural, electrical and optical properties was studied. The characterization of samples was carried out by X-ray diffraction (XRD), UV–Vis spectroscopy, energy dispersive spectroscopy (EDS), scanning electron microscopy and four probe points measurements. The XRD study showed that all the films were polycrystalline consisting of Co3O4 spinel cubic phase. The preferred orientation of the crystallites changed from (311) to (111) when the substrate temperature increases. The average calculated grain size was about 40.38 nm. Morphological studies exposed that the films surface morphology is almost homogeneous and well-covered. Peaks associated with Co and O elements are present in EDS analysis witch confirm the composition of the films. The optical transmittance and the band gaps energy increase with the increase of substrate temperature. The measured electrical conductivity at room temperature was found in the order of 10−1 (Ω cm)−1.

UV-Protective TiO2 Thin Films with High Transparency in Visible Light Region Fabricated via Atmospheric-Pressure Plasma-Enhanced Chemical Vapor Deposition.

This article focuses on control of film thickness and roughness to improve the ultraviolet (UV)-protective performance of TiO2 films prepared by atmospheric-pressure plasma-enhanced chemical vapor deposition using titanium(IV) isopropoxide (TTIP) as the precursor and argon as the plasma working gas. The relationship between the film morphology and UV-protective performance suggested that a decrease in roughness is the key factor to achieve performance improvement. The effects of substrate temperature and precursor concentration were investigated, and the results showed that an increase in both substrate temperature and precursor concentration reduced the roughness and improved the transparency to visible light without reducing the ability to block UV light. Finally, a TiO2 film with greater than 99% UV light blockage and greater than 95% transmittance of visible light was obtained.

Investigation of wettability of Li on 316L SS surface and interfacial interactions for fusion device

Improved liquid Li wettability on a solid substrate surface is a necessary component for the research and development of blanket coolants, tritium breeders, and first wall materials for fusion device. A systemic investigation of Li wetting a 316 L SS surface, along with interfacial interactions has been successfully carried out. The results indicate that base vacuum pressure of the vessel, substrate temperature, and surface conditions of the substrate are the main factors that influence Li wetting property. It has been found that poor vacuum (>10−1Pa) along with high impurity content, especially water, can prevent Li wetting due to the formation of a layer of complex Li compounds, such as LiOH, Li3N and Li2CO3. Also, Li wetting can be gradually improved with an increase of substrate temperature, mainly due to a decrease in surface tension of Li droplets. Moreover, Li wetting can be further improved by effective surface conditioning. It has been demonstrated that baking was beneficial in order to release impurity gas by thermal desorption and thereby achieve high vacuum during Li wetting, which resulted in a reduction of > 50 °C in Li wetting temperature on the SS substrate. He-GDC and Li coating can further decrease Li wetting temperatures to the Li melting point (∼180 °C) by avoiding the formation of Li2O at the interfacial surface during Li wetting. This is achieved primarily because these conditioning techniques can effectively remove and isolate the SS surface oxide layer (Cr2O3), respectively, which was verified by the related testing of interfacial interactions between liquid Li and SS. Finally, surface textured structures with trenches ∼μm in size, are demonstrated to promote Li spreading along the groove direction, driven by capillary forces. These results provide the technical support for liquid Li applications in future fusion reactors.

Deposition of polycrystalline zinc substituted hydroxyapatite coatings with a columnar structure by RF magnetron sputtering: role of in-situ substrate heating

Zn incorporation into hydroxyapatite structure leads to enhanced osteointegration and antibacterial activity of deposited coatings. Radiofrequency magnetron sputtering is a physical vapor deposition technique which can be used to create thin coatings with a controlled level of crystallinity. The material state is a crucial parameter for biocoatings as it governs cell response. Bioactive Zn substituted hydroxyapatite coatings were deposited onto Ti by radiofrequency magnetron sputtering at increased substrate temperatures (100, 200, 300 and 400°C). XRD showed crystallization of the coatings at elevated substrate temperatures starting from 300°C. Cross-section transmission electron microscopy showed a polycrystalline columnar grain structure of Zn substituted coatings deposited at 400°C substrate temperature. An amorphous TiO2 sublayer of several monolayers thickness was detected in the interface between the polycrystalline coating and the Ti substrate. In-column energy dispersive X-ray analysis revealed coatings to be substoichiometric with the average Ca/P ratio being 1.5. It is established that it is possible to deposit Zn substituted hydroxyapatite in a form of a well-crystalline coating when the substrate temperature is exceeding 400°C.

Boron doped Zinc Oxide for Ethanol and CO Gas Sensing

This paper presents study of the properties of ZnO and ZnO:B deposited at 450oC on glass substrates by chemical spray pyrolysis (CSP) with thickness(150±5 nm) as a gas sensor for vapor ethanol and CO gases. The structure of ZnO:B films has been found to exhibit the hexagonal wurtzite structure. The increase of boron concentration caused to decrease the grain size. The structural details were obtained from X-ray diffraction. The surface morphology of the films was studied by using the Scanning Electron Microscopy (SEM), and the Transmission electron microscopy (TEM). Sensitivity of the films is increases with the increase of boron concentration and substrate temperature

Influence of substrate temperature on properties of pyrite thin films deposited using a sequential coevaporation technique

A series of pyrite thin films were deposited in-situ in a monolayer-by-monolayer fashion using sequential evaporation of iron under high vacuum, followed by sulfidation at a sulfur pressure of 133 Pa, as a function of substrate temperature. The stoichiometry, crystallinity, topographic smoothness, and phase purity of the deposited pyrite thin films improve with increasing substrate temperature up to 420 °C, the highest temperature studied. Characterization of the films deposited at 420 °C using selected-area precession electron diffraction, Raman Spectroscopy, and conventional X-ray diffraction indicated that the pyrite layer is phase pure, with no evidence of a secondary marcasite phase, and grew in columnar grains with a preferential (100) orientation on the (100) silicon substrates. This novel sequential evaporation technique has the potential to make useful low-cost semiconducting pyrite materials for large-area electronic applications.

Synthesis and structural evolution of hydrogenated amorphous silicon carbide thin film with carbon nanostructures

A new hydrogenated amorphous silicon carbide (a-SiCx:H) thin film with carbon nanostructure is grown through plasma enhanced chemical vapor deposition (PECVD) method. The structural evolution and growth mechanism of the as deposited a-SiCx:H thin film are explored and further discussed with different substrate temperatures. The results show that the structure of the a-SiCx:H thin film is a multiphase structure of carbon nanostructures embedded into CSiO(H) amorphous matrix, and the carbon nanostructure is a spheroidal graphite-like structure. With increasing substrate temperature, the carbon nanostructure gradually grows up through incorporation with surrounding nanostructures. When the substrate temperature increases further to 300 °C, the ultrafine basic structure units of graphite are found within the carbon nanostructure. In addition, the disorder of the thin film first increases and then decreases with increasing substrate temperature, which give rise to band tail states among the π-π⁎ band gap. The change of structure of as synthesized a-SiCx:H thin film with different substrate temperatures supports the sub-plantation model. Furthermore, a tunable optical band gap depended on structure of the carbon nanostructures is demonstrated at different substrate temperatures, which may bring about a potential of application.

Substrate temperature effect during the deposition of (Cu/Sn/Cu/Zn) stacked precursor CZTS thin film deposited by electron-beam evaporation

Kesterite-Cu2ZnSnS4 (CZTS) thin films were deposited on molybdenum (Mo) coated glass substrates using electron-beam evaporation from stacked layer precursor (Cu/Sn/Cu/Zn). Influence of substrate temperatures during the deposition on the morphological, optical and structural properties of CZTS thin films were investigated using FE-SEM, EDS, Raman, UV–Vis and XRD methods. X-ray diffraction studies revealed that CZTS films deposited at 310 °C possess kesterite structure with preferential growth along (112) plane. FE-SEM studies revealed that the surface of the CZTS film contains spherical shaped grains distributed on the surface, the surface becomes smooth and the grain size increases with increase of the substrate temperature. Size, shape, and distribution of the elements and their effect on the CZTS films surface were studied as a function of substrate temperature. With increase of substrate temperature, the band gap value of CZTS thin films reduce from 1.46 to 1.11 eV. At 310 °C, Hall coefficient study showed that the CZTS film has p-type conductivity with low resistivity of 4.23 Ω cm. Solar cells were fabricated on a soda lime glass (SLG) substrate with the following structure SLG/Mo/Cu2ZnSnS4/CdS/i-ZnO Al:ZnO/Al. The optimized solar cell has a conversion efficiency of 2.4% with Jsc = 12.5 mA/cm2, Voc = 332 mV and FF = 58.0.

Adhesion force behaviors between two silica surfaces with varied water thin film due to substrate temperature studied by AFM

ABSTRACT The adhesion force between two silica surfaces was measured to investigate the effect of substrate temperature using an atomic force microscope (AFM) at various relative humidities (RH). Results show that the adhesion force behavior largely depends on the thickness of water thin film and surface conditions. At different RHs, the adhesion force decreases with the increase of substrate temperature, which was attributed to the decrease of water film thickness on surfaces due to dehydration and/or dehydroxylation. However, a hysteresis of adhesion force was observed by increasing and decreasing substrate temperature. When the substrate temperature returns back to a low value, the adhesion force becomes abnormally large, which was attributed to rehydroxylation, rehydration, and the evaporation of organic contaminants. At low RH (5 ± 1 %), the adhesion force also becomes abnormally large after cooling, which was attributed to the formation of siloxane bonds between the cantilever and sample surfaces. These results may help facilitate the anti-adhesion design of small-scale silicon-based systems under different conditions.

Effects of Heating Mode and Temperature on the Microstructures, Electrical and Optical Properties of Molybdenum Thin Films.

In this paper, molybdenum (Mo) thin films are deposited on soda-lime glass (SLG) substrates by direct current magnetron sputtering and heated in three different modes at different temperatures, including substrate heating, annealing treatment, and both substrate heating and annealing treatment. The effects of heating temperature and heating mode on the structures, morphology, optical and electrical properties of Mo thin films were systematically investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM), atomic force microscope (AFM) and UV-visible spectrophotometer (UV-vis spectra). It is shown that as the substrate and annealing temperature increase, the crystallinity of Mo thin films is improved, and the grain sizes become bigger. Especially in the mode of both substrate heating and annealing treatment at higher temperature, the obtained Mo thin films show higher crystallinity and conductivity. Moreover, with the increase of substrate and annealing temperature in different heating modes, both the surface compactness of Mo films and the optical reflectance increase correspondingly. Furthermore, the Mo film, prepared at the substrate heating temperature of 400 °C and annealed at 400 °C, showed excellent comprehensive performance, and the resistivity is as low as 1.36 × 10−5 Ω·cm. Using this optimized Mo thin film as an electrode, copper indium gallium selenium (CIGS) solar cells have a maximum photo-conversion efficiency of 12.8%.

Magnetic Field MEMS-Sensor: Functional Characteristics Control during the Formation of Magnetosensitive Structures

In this work the results of substrate temperature effects on coercivity and magnetoresistance in ferromagnetic structures are shown. It was found that with an increase of the substrate temperature from 270 to 390 °C the magnetoresistance increases from 1.2 to 2.3% and the coercive force from 1.6 to 5.3 Oe. A new topology of anisotropic magnetoresistive structures is proposed. In these structures the shape of ferromagnetic elements repeats the shape of nonmagnetic conducting shunts. Sensitivity values obtained for both types of magnetic structures are compared.

Physical properties of nebulized spray pyrolysised SnO2 thin films at different substrate temperature

Using nebulized spray pyrolysis technique, we investigate tin oxide (SnO2) thin films had been coated with different substrate temperature (300–500 °C) onto microscopic glass substrate. All the prepared films have tetragonal crystalline structure with preferential orientation (110) observed by X-ray diffraction analysis. The reduced strain due to the increase of substrate temperature from 300 to 450 °C increased the average crystalline size from 27.40 to 42.99 nm and then decreased further. All the films display high transmittance in the visible and also in IR region. As the substrate temperature had increased from 300 to 500 °C, the average transmittance of SnO2 thin films varied between 79 and 90%. The energy band gap values had diminished from 3.91 to 3.75 eV by increasing the substrate temperature. The refractive index (n) of these films had increased from 2.11 to 2.32 with increase in substrate temperature from 300 to 450 °C and then decreased further. The optical static and high frequency dielectric constants (eo and e∞) have been determined as a role of substrate temperature. The surface morphology of these thin films exhibited polyhedron-shaped grains obtained by scanning electron microscope. Energy dispersive X-ray analysis proved the presence of Sn and O elements in the as-prepared SnO2 films. Hall effect measurements shows that the film had deposited at 450 °C exhibited lowest resistivity 6.53 × 10−3 Ω cm and highest figure of merit 9.14 × 10− 3 (Ω/sq)−1 among all the samples. Activation energy varied between 0.14 and 0.20 eV with the increase of substrate temperature from 300 to 500 °C.

Structural and optical properties of ZnO films grown on ion-plated Ga doped ZnO buffer layers by atmospheric-pressure chemical vapor deposition using Zn and H2O as source materials

Zinc oxide (ZnO) films were grown on glass substrates with ion-platedGa-doped ZnO (GZO) buffer layers at various substrate temperatures by atmospheric-pressure chemical vapor deposition using Zn powder and water as precursors. All the X-ray diffraction patterns of the ZnO/GZO films were dominated by a ZnO(002) peak, indicating the successful growth of highly c-axis oriented films. The substrate temperature dependence of growth rate was divided into three regions with the different activation energies, i.e.re-evaporation, mass-transport controlled and surface-controlled regions. Scanning-electron-microscope observations revealed that the films grown at the substrate temperature in the mass-transport-controlled region exhibited the terrace-like surface morphology with rock-like structures. Photoluminescence spectra of the ZnO/GZO films were composed of a near-band-edge (NBE) emission at a wavelength of about 380 nm and a broad-band emission spreading over the visible wavelength region, as regardless of the substrate temperature. The visible-broad-band emissions observed on many samples could be decomposed into two or three peak emissions with the Lorentzian shapes. With increasing substrate temperature, the wavelength of the emission showing the strongest intensity, which was obtained by the decomposition of the visible-broad-band emission, shifted towards longer wavelengths together with the broadening of its width.