Increasing Deposition Temperature Research Articles

Investigation of Antireflection Nb₂O₅ Thin Films by the Sputtering Method under Different Deposition Parameters.

In this study, Nb2O5 ceramic was used as the target to deposit the Nb2O5 thin films on glass substrates with the radio frequency (RF) magnetron sputtering method. Different deposition temperatures and O2 ratios were used as parameters to investigate the optical properties of Nb2O5 thin films. The deposition parameters were a pressure of 5 × 10−3 Torr, a deposition power of 100 W, a deposition time of 30 min, an O2 ratio (O2/(O2 + Ar), in sccm) of 10% and 20%, and deposition temperatures of room temperature (RT), 200, 300 and 400 °C, respectively. We found that even if the deposition temperature was 400 °C, the deposited Nb2O5 thin films revealed an amorphous phase and no crystallization phase was observed. The optical properties of transmittance of Nb2O5 thin films deposited on glass substrates were determined by using a ultraviolet-visible (UV-vis) spectrophotometer (transmittance) and reflectance spectra transmittance (reflectance, refractive index, and extinction coefficient) in the light wavelength range of 250–1000 nm. When the O2 ratio was 10% and the deposition temperature increased from RT to 200 °C, the red-shift was clearly observed in the transmittance curve and the transmission ratio had no apparent change with the increasing deposition temperature. When the O2 ratio was 20%, the red-shift was not observed in the transmittance curve and the transmission ratio apparently decreased with the increasing deposition temperature. The variations in the optical band gap (Eg) values of Nb2O5 thin films were evaluated from the Tauc plot by using the quantity hν (the photon energy) on the abscissa and the quantity (αhν)r on the ordinate, where α is the optical absorption coefficient, c is the constant for direct transition, h is Planck’s constant, ν is the frequency of the incident photon, and the exponent r denotes the nature of the transition. As the O2 ratio of 10% or 20% was used as the deposition atmosphere, the measured Eg values decreased with the increase of the deposition temperature. The reflectance ratio, extinction coefficient, and refractive index curves of Nb2O5 thin films were also investigated in this study. We would show that those results were influenced by the deposition temperature and O2 ratio.

Synergetic combination of Te content and deposition temperature to optimize thermoelectric properties using sputtered bismuth telluride films

Bismuth telluride films were prepared on the quartz glass by magnetron sputtering at various temperatures. Co-sputtering method with the alloying Bi2Te3 and Te targets was adopted to adjust the content of Te. The influence of Te content and deposition temperature on microstructure and thermoelectric performance was investigated systematically. Irregular hexagonal grains were observed in the surface of films prepared at 300 °C, but part of irregular hexagonal grains became to triangular and truncated triangular morphology with layered structure at elevated temperature when only one alloying Bi2Te3 target was used. However, lamellar grains could be observed at 300 °C and 350 °C particularly when films were prepared by the alloying Bi2Te3 and Te targets, which indicated that Te content had an obvious effect on surface morphology. In addition, the Seebeck coefficient and power factor of films which prepared by co-sputtering increased, compared with the films prepared at the same temperature only by the alloying Bi2Te3 target. And the Seebeck coefficient and power factor of films were higher with increase of deposition temperature. Maximum Seebeck coefficient and power factor of bismuth telluride films have been prepared at 400 °C by the alloying Bi2Te3 and Te targets, which attributed to the optimum of Te content and deposition temperature.

High-speed deposition of oriented orthorhombic NaTaO3 films using laser chemical vapor deposition

We demonstrated the high-speed laser chemical vapor deposition of orthorhombic NaTaO3 (o-NaTaO3) films. The orientation of the o-NaTaO3 films was changed from (101) to (112) to (001) plane as the increase of deposition temperature from 823 to 913K. o-NaTaO3 films had faceted surfaces and columnar cross sections. The deposition rates of o-NaTaO3 films were 48–120µmh−1, which are 192–6000 times higher than those offered by wet-chemical routes.

Effect of deposition temperature on the structural, morphological and optical band gap of lead selenide thin films synthesized by chemical bath deposition method

Lead selenide (PbSe) nanocrystalline thin films have been deposited on silica glass substrates by the chemical bath deposition technique. The samples were deposited at the bath temperatures of 60, 75 and 90 °C respectively and characterized by a variety of techniques. The XRD results revealed that the PbSe thin film deposited at 60 °C was amorphous in nature. Films deposited at higher temperatures exhibited sharp and intense diffraction peaks, indicating an improvement in crystallinety. The deposition temperature also had a strong influence on the preferred orientation of the crystallites as well as other structural parameters such as microstrain and dislocation density. From the SEM study it was observed that film deposited at 90 °C had well defined crystallites, uniformly distributed over the entire surface of the substrate. The EDAX study confirmed that the samples deposited at the higher temperature had a better stoichiometric ratio. The optical band gap varied from 2.26 eV to 1.13 eV with increasing deposition temperature.

Characterization and sensing properties of ZnO film prepared by single source chemical vapor deposition

A novel deposition technique has been used to grow ZnO films. Good quality films were obtained on glass substrates by single source chemical vapor deposition (SSCVD), for gas sensing applications. The properties of ZnO films were investigated at different deposition temperatures 300, 350 and 400°C. X-ray diffraction results show that all deposited films were polycrystalline. The morphological, structural, optical and electrical properties of the films have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), cathodoluminescence (CL) and Hall effect techniques. The morphology of the deposited films evolves from columnar grains, to parallel plates as the substrate temperature increases. A significant increase in the relative intensities of the green and red emission with increasing deposition temperature has been observed. Electrical properties, relevant for gas sensing behavior have been investigated as well. In the particular case of CO an operating temperature of 300°C seems to yield the best sensitivity.

Characterization and analysis of wheat-like CdS nanostructures under temperature effect for solar cells applications

CdS nanostructures have grown by chemical bath deposition (CBD) method onto glass substrates. The morphological, structural, optical and electrical properties are investigated for CdS nanostructures synthesised at different temperatures; 65, 75, 85 and 95°C. The X-ray diffraction (XRD) has proved that polycrystalline structure is (002) orientation. Field-Effect Scanning Electron Microscopy (FE-SEM) results have revealed smooth morphology with few cracks at low temperature. Homogeneous surface morphology includes large particles is emerged as temperature increases. The optical band gap was decreased from 3.59 to 3.0eV as temperature increases. Photoluminescence spectra (PL) has shown the band gap shifts to longer wavelength as deposition temperature increases. Refractive index and optical dielectric constant are calculated using specific models. The transmittance shows temperature dependence. The conductivity was measured at the optimal temperature 95°C.

Metalorganic chemical vapor deposition of few-layer sp2 bonded boron nitride films

A systematic study of the growth of atomically smooth few-layer sp2 bonded BN on 50mm sapphire substrates by metalorganic chemical vapor deposition (MOCVD) using Triethylboron (TEB) and NH3 as precursors is described. Based on the experimental results obtained using Raman spectroscopy, atomic force microscopy (AFM), X-ray reflectance measurements and transmission electron microscopy, we explored the growth parameter space and identified three different growth modes: random three-dimensional (3D) growth, a self-terminating few-layer growth mode, and a very slow layer-by-layer mode. The growth mode depends on the temperature, pressure, V/III ratio, and surface nitridation conditions, as follows: 3D island growth is dominant in the low V/III range and is characterized by a decreasing growth rate with increasing deposition temperature. When the V/III ratio is increased this 3D island growth mode transitions to a self-terminating few-layer growth mode. An additional transition from self-terminating growth to 3D growth occurs when the growth pressure is increased. Very slow layer by layer growth is found at high temperature and low pressure. Finally, substrate surface nitridation promotes self-terminating growth that results in atomically smooth films.

Mechanical properties and fractal analysis of the surface texture of sputtered hydroxyapatite coatings

This aim of this work is to establish a relationship between the surface morphology and mechanical properties of hydroxyapatite coatings prepared using RF magnetron sputtering at temperatures in the range from 400 to 800°C. The topography of the samples was scanned using atomic force microscopy, and the obtained 3D maps were analyzed using fractal methods to derive the spatial characteristics of the surfaces. X-ray photoelectron spectroscopy revealed the strong influence of the deposition temperature on the Ca/P ratio in the growing films. The coatings deposited at 600–800°C exhibited a Ca/P ratio between 1.63 and 1.69, close to the stoichiometric hydroxyapatite (Ca/P=1.67), which is crucial for proper osseointegration. Fourier-transform infrared spectroscopy showed that the intensity of phosphate absorption bands increased with increasing substrate temperature. Each sample exhibited well defined and sharp hydroxyapatite band at 566cm−1, although more pronounced for the coatings deposited above 500°C. Both the hardness and elastic modulus of the coated samples decrease with increasing deposition temperature. The surface morphology strongly depends on the deposition temperature. The sample deposited at 400°C exhibits circular cavities dug in an otherwise flat surface. At higher deposition temperatures, these cavities increase in size and start to overlap each other so that at 500°C the surface is composed of closely packed peaks and ridges. At that point, the characteristics of the surface turns from the dominance of cavities to grains of similar size, and develops in a similar manner at higher temperatures.

EFFECT OF DEPOSITION TEMPERATURE ON THE PROPERTIES OF TIO2 THIN FILMS DEPOSITED BY MOCVD

Crystal structure, microstructure, and optical properties of TiO2 thin films deposited on quartz substrates by metal-organic chemical vapor deposition (MOCVD) in the temperature range from 250[Formula: see text]C to 450[Formula: see text]C have been studied. The crystal structure, thickness, microstructure, and optical properties have been carried out using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), atomic force microscope (AFM), and UV-visible transmittance spectroscopy, respectively. XRD patterns show that the obtained films are pure anatase. Simultaneously, the crystal size calculated using XRD peaks, and the grain size measured by AFM decrease with the increase in deposition temperature. Moreover, the texture of the films change and roughness decrease with the increase in deposition temperature. The spectrophotometric transmittance spectra have been used to calculate the refractive index, extinction coefficient, dielectric constant, optical energy gap, and porosity of the deposited films. While the refractive index and dielectric constant decrease with the increase of deposition temperature, the porosity shows the opposite.

Influence of deposition temperature on luminescent efficiency of Y2O3:Eu3+ thin films deposited on quartz fabric by EBE

Y2O3:Eu3+ thin films were grown on quartz fabric substrate by electron beam evaporation (EBE) at different deposition temperatures. It was found that an increase of deposition temperature from room temperature (R.T.) to 250°C results in improved morphologies of the films, such as reduced defects, spherical particle shape and dense surface topography. A change in the predominant orientation of Y2O3:Eu3+ thin films was detected from (222) at low temperatures of R.T.–150°C to (400) at higher temperatures of 200–250°C. The luminescent intensity of the films was gradually improved with an increase in deposition temperature and the optimal brightness was observed when the films were grown at 250°C and improved by 32.67% in comparison with that of the films grown at R.T. The results reveal that the improved morphologies and effective crystallization can contribute to the enhanced luminescent properties of the Y2O3:Eu3+ thin films.

MD simulation of effect of crystal orientations and substrate temperature on growth of Cu/Ni bilayer films

We prepare Cu/Ni bilayer films by depositing the incident atoms on Cu substrates with various surface orientations and under different temperatures and investigate interfacial structure, surface roughness, radial distribution function and hardness of the films. We find that the incident atoms can penetrate (001) substrate more easily than other surfaces, resulting in a transitional layer consisting of two kinds of atoms. Stacking faults are generated in the bilayer films deposited on the (111) substrate, which can reduce misfit strain and thus account for the layer growth mode of the films. The surface roughness decreases with the increase in deposition temperature. Moreover, we also find that a certain degree of roughness benefits the formation of coherent interface due to the tilted-layer epitaxial growth. The hardness differs for the films deposited at different temperatures.

Deposition and XPS studies of dual sputtered BCN thin films

Thin films of boron carbon nitride (BCN) are deposited by co-sputtering of B4C (Direct Current—DC) and BN (Radio frequency—RF) targets with varying N2/Ar gas flow ratio and DC target power. BCN being a low-k material and a potential inter layer dielectric (ILD), the deposition and surface analysis become prime factors for ultra large scale integration (ULSI) process and device integration. In this study, a thorough analysis on deposition rate of BCN thin films is conducted as a function of various N2/Ar gas flow ratios, target powers and substrate deposition temperatures. XPS studies are conducted to ascertain the chemical composition and bonding of the deposited BCN films for the various deposition parameters. The deposition rate is found to show a decreasing trend with an increase in substrate deposition temperature but showed an increasing trend at 400°C. As the sputtering yield of B4C target is far greater than that of BN target, the deposition rate and XPS studies are conducted for the target powers of 20W and 40W for the B4C target. The deposition rate showed a decreasing trend from N2/Ar=0.25 to 0.75, but increases at N2/Ar=1. The XPS characterization indicates the formation of BCN phase distinctly with few separate phases of CN and BN.

Anodic deposition of CoOOH films with excellent performance for electrochemical capacitors

Amorphous CoOOH films were fabricated on hexagonal graphite substrates in 0.2 M CoSO4 at a constant anodic deposition potential of 1.60 V vs Ag/AgCl (3 M KCl) under different deposition temperatures, and their electrochemical behaviors in 1 M NaOH and 1 M NaCl were systematically studied. The results showed that the deposition temperature had a significant effect on the electrochemical behaviors of the CoOOH films. For the four CoOOH films prepared under different deposition temperatures, when tested either in 1 M NaOH or 1 M NaCl, their area specific capacitance (C A) and cycle stability increased monotonously, their mass specific capacitance (C M) first increased and then decreased, while their bulk resistance (R bulk) and charge-transfer resistance (R ct) first decreased and then increased with increasing deposition temperature. In addition, the CoOOH films had high C M, good electrical conductivity, low faradic charge-transfer resistance, and low diffusive resistance. Among the four CoOOH films fabricated under different deposition temperatures, the film prepared under a deposition temperature of 45 °C (Sample 3) had the highest C M, the lowest R bulk, the lowest R ct, and good rate capability which can be ascribed to its structure with nanoparticles and nodules on its surface as well as its appropriate thickness. As a result, the CoOOH film fabricated by anodic deposition is a very promising electrochemical capacitor material for applications.

Preparation, microstructure of B film and its applications in MgB2 superconducting Josephson junction

Magnesium diboride is a binary compound with a simple AlB2 type crystal structure and a high-Tc (nearly 40 K) superconductor. The rather high Tc value and the specific properties make it a potential material for electronic applications. The key structure for the application is a Josephson junction. The growth of tri-layer structure consisting of MgB2 film and tunneling barrier layer is a key technology for a Josephson junction. Boron is a kind of good insulating medium. Preparation of MgB2/B/MgB2 tri-layer structures by chemical vapor deposition (CVD) method is investigated. The experimental results indicate that the depositing temperature will influence the microstructure of boron film significantly and different crystal structures of boron films are obtained at different temperatures.The boron film is an amorphous film while the deposition temperature is lower than 500 ℃, and the amorphous B film can be transformed into MgB2 superconducting film by annealing in Mg vapor. For precursor B films deposited at 470 ℃ and 500 ℃, the critical temperatures of the relevant MgB2 films are 39.8 K and 38.5 K, respectively. As the deposition temperature is higher than 550 ℃, the boron film becomes crystallized, and increasing deposition temperature will increase the crystallinity of the B film as can be seen from the samples deposited at 550 ℃, 600 ℃, 650 ℃ and 680 ℃. The boron film turns out to be of -phase crystalline texture, which is verified by X-ray diffraction and scanning electron microscope. What is more, the crystalline boron film is a kind of inert film, and it does not react with Mg in Mg vapor, thus it cannot be transformed into superconducting film in the subsequent annealing steps. By utilizing the property of the crystallized boron film, a square-shaped Josephson junction with a size 100 m100 m of MgB2/B/MgB2 structure is prepared. The thickness of boron dielectric layer is about 10 nm, and the DC Josephson effect is observed by the I-V measurement of the junction. Compared with other tri-layer structure based on MgB2 material, such as the MgB2/MgO/MgB2, the structure in which B film serves as a barrier layer eliminates the oxygen and can be fabricated in-situ easily by CVD method, and reliable Josephson junctions can be expected by such a technology.

Defect studies of Mg films deposited on various substrates

In the present work the structure of Mg films deposited by RF magnetron sputtering was characterized using variable energy positron annihilation spectroscopy combined with scanning electron microscopy and X-ray diffraction. The effect of deposition parameters, namely temperature, type of substrate and deposition rate, on the microstructure was examined. All Mg films studied grow with the basal (0001) plane parallel with the substrate and exhibit only negligible in-plane stress. Films deposited at room temperature are characterized by nanocrystalline structure with high volume fraction of grain boundaries. and positrons are preferentially trapped in open volume defects present at grain boundaries. In these films positrons are trapped predominantly in open-volume defects present at grain boundaries. With increasing deposition temperature the mean grain size increases and the volume fraction of grain boundaries decreases. Hence, in Mg films prepared at elevated temperatures positrons are trapped mainly at misfit dislocations compensating different atomic spacing in the films and the substrate. Moreover, it was found that slow deposition rate leads to higher density of defects compared to fast deposition rate. By annealing of Mg film with thin 20 nm Pd overlayer at 300°C for 1 hour Pd layer is mixed with Mg film forming a Mg-Pd compound. The Mg-Pd phase likely contains structural open-volume defects which trap positrons.

Effects of deposition temperature on structural, optical and electrical properties of TEA complexed nanocrystalline films of PbS prepared from lead acetate with reduced concentration

A number of researchers have been synthesising thin films of PbS on glass substrates by reaction of 1 M CH4N2S with of 0.50 M Pb(CH3COO)2.3H2O complexed by 1 M triethanolamine (TEA) at different deposition temperatures and reported various temperature dependent properties of the films. In our work, we followed the same recipe but reduced the concentration of Pb(CH3COO)2.3H2O by 0.10 M. The pH of the bath was adjusted at 12. The deposition has been carried out at five different temperatures—30, 40, 50, 64 and 70 °C. We wish to study how structural, optical and electrical properties of the films prepared with reduced concentration of Pb(CH3COO)2.3H2O change with temperature. We have observed that at 30 and 40 °C, no crystalline PbS phase was formed, only elemental S was detected. The PbS phase formation was noticed only from 50 °C. The elemental S has been subdued and the crystalline PbS phase formation has been enhanced with increase of temperature. The average crystallite sizes were determined from XRD by Debye–Scherrer formula, lattice constants from Nelson–Riley plot, band gaps by the derivative method and electrical conductivities from current–voltage characteristics. It has been found that with the increase of deposition temperature, the crystallite size increases, strain decreases, band gap reduces and conductivity improves. The average crystallite sizes were found 35.79, 42.51 and 42.67 nm at 50, 64 and 70 °C respectively. The band gaps for these three films were noted as 1.74, 1.67 and 1.66 eV respectively indicating blue-shift from the bulk value. The tail widths of localised states in the forbidden band were observed in the range of (0.70–0.76) eV. The strains in the films were ~10−3 and conductivities were ~10−7–10−6 (Ω cm)−1.

Novel carbon felt composites with pyrocarbon deposited on carbon fiber: Hierarchical microstructure for improved phenol-adsorption

ABSTRACTCarbon felt composites were prepared by chemical vapor deposition (CVD) method using Ni(NO3)2 as a catalyst and methane as a pyrocarbon precursor. The pyrocarbon which has been deposited on fiber surface increased gradually with increase in deposition temperature. Besides, the surface of the deposited pyrocarbon was seen to contain many micropores. The phenol-adsorption capability evaluation of the composites showed that the adsorption equilibrium was achieved in 90 min, and the maximum adsorption quantity reached was 13.37 mg/g. The Langmuir isotherm model was preferred in fitting the adsorption data compared with the Freundilch isotherm model. The theoretical maximum adsorption was calculated to be 17.45 mg/g. At pH = 5, the adsorption quantity was a minimum of 10.66 mg/g. Moreover, the phenol-adsorption quantity increased with increasing deposition temperature. The adsorption quantity on carbon felt composites without pyrolytic carbon deposition was minimum, being 9.11 mg/g, while that of carbon fiber produced at 950°C reached the maximum of 13.37 mg/g.

Study of deposition temperature on high crystallinity nanocrystalline silicon thin films with in-situ hydrogen plasma-passivated grains

This paper studies the effect of deposition temperature on the growth of nanocrystalline silicon (nc-Si) films deposited by 13.56MHz plasma enhanced chemical vapor deposition (PECVD) with in-situ hydrogen (H) passivation. A high crystalline volume fraction (XC) of 80% was found in the ~100nm nc-Si film deposited at 260°C with 99% H2 diluted SiH4 at intermediate RF power between the power-limited and precursor-limited regimes. Based on these optimized deposition conditions, 300–400nm nc-Si films deposited at 75–260°C also showed a high XC of 82–85%, an intrinsic-like dark-conductivity (σdark) of ~10−6S/cm, and even a low mean oxygen content (CO) of 1017–1018at./cm3. Although material properties were similar, deposition temperature appeared to change the qualitative structure of the nanocrystalline grains. The preferred grain orientation changed from 〈111〉 to 〈220〉 as the deposition temperature was increased from 75 to 260°C due to enhanced surface diffusion of deposition precursors. This reflected in more compact and lateral columnar growth of nc-Si films with increasing deposition temperature. We successfully demonstrated high field-effect hole and electron mobilities of 33.8 and 225cm2/Vs, respectively, in top-gate thin-film transistors (TFTs) employing the ~100nm nc-Si channel layer deposited at 260°C.

Effect of deposition temperature on structural and optical properties of chemically grown nanocrystalline Ni doped ZnS thin films

ZnS:Ni thin films with high purity in composition and crystallographic sense were deposited by chemical bath deposition method at temperatures ranging from 40 to 80 °C. The effect of deposition temperature on the average crystal size, lattice constant, lattice strain, optical, and photoluminescence properties of the films is followed and discussed. The band gap energy of the ZnS:Ni thin films deposited at 40 °C is blue-shifted by about 0.14 eV with respect to the bulk value, while with increasing deposition temperature to 80 °C it converges to 3.6 eV. The photoluminescence (PL) spectra of the ZnS:Ni thin films exhibited three emission peaks, two intense peaks located at 430 nm and 523 nm and a weak shoulder peak over 325–400 nm range. The intensity of photoluminescence emission is enhanced with increasing deposition temperature. X-ray diffraction analysis shows that the ZnS:Ni films constituted from nanocrystals possessing average radii close to, and partially larger than, the radius of a bound exciton in the corresponding bulk semiconductor. Finally, a subsequent analysis based on effective mass approximation model permits determination of the reduced effective mass of the electron–hole pair (μeff∗) and the relative dielectric constant (εr) for the ZnS:Ni nanocrystals in thin film from.

Tailoring the resonance wavelength and loss of highly Ga doped ZnO plasmonic materials by varied doping content and substrate temperature

In this paper, Ga-doped ZnO (GZO) thin films are deposited on glass substrates by radio frequency magnetron sputtering for low loss plasmonic applications. The effects of Ga2O3 content in the target and substrate temperature on the electrical, structural and optical properties of GZO films are investigated. Film with the highest carrier concentration of 7.0×1020cm−3 was obtained at a Ga2O3 content of 5wt% in the target under room temperature deposition. With increasing deposition temperature, the lowest electrical resistivity of 3.8×10−4Ωcm was acquired at a deposition temperature of 200°C. The values of plasmonic resonances wavelength could be changed from 1.35 to 2.39μm by adjusting the carrier concentration. Material absorption losses in these GZO films are 10 times lower than that of conventional Ag films at telecommunication wavelengths. These results make GZO a promising low-loss plasmonic material operating at telecommunication wavelengths.