Search

In this paper, we report a systematic study on effect of film thickness and substrate temperature on structural and magnetic behaviour of Fe-Ga films with Cu buffer layer, deposited on Si and Si/SiO2 substrates at room and high substrate temperatures. Grazing incidence X-ray diffraction studies reveal that all the films are crystalline with disordered alpha-Fe phase, which is BCC A2 phase. At 300 °C of substrate temperature, films deposited on Si/SiO2 substrate found to nucleate L12 phase from matrix of A2 phase, which is not seen in Si based films. Irrespective of substrate material, Fe-Ga films found to exist in dual phases at 500 °C substrate temperature. Lattice strains of the films were calculated from X-ray diffraction patterns, using Williamson-Hall method. From X- ray reflectivity analysis of all the films, film density, thickness and roughness of Fe-Ga layer and buffer layer were obtained after fitting the reflectivity data. Presence of an oxide layer is also evident from reflectivity fitting analysis. From magnetization studies it is clear that, all the films exhibited strong in-plane anisotropy. Saturation magnetization of films was found to vary with change in film density and oxide layer thickness of films. Saturation magnetization of films deposited on Si substrates found to decrease with decrease in film density. Coercivity of films found to vary with change in crystallite size, interface roughness and lattice strain of films. Films deposited on Si substrates are sensitive to strain with change in film thickness and films deposited on Si/SiO2 substrates are sensitive to strain with change in deposition temperature. Coercivity in films found to decrease with decrease in film roughness, increase in crystallite size and lowering the tensile lattice strain. [ABSTRACT FROM AUTHOR]

Diamond-like-carbon "DLC" coatings can be deposited in many different ways, giving a large range of material properties suitable for many different types of applications. Hydrogen content significantly influences the mechanical properties and the tribological behavior of DLC coatings, but its determination requires techniques that are not available in many research centers. Thus, it is important to find alternative indirect techniques, such as Raman spectroscopy or nanoindentation (hardness measurements), which can give comparative and indicative values of the H contents in the coatings, particularly when depositions with a reactive gas flow are being studied. In this work, "DLC" composite coatings with varying H content were deposited via Physical Vapor Deposition (PVD) magnetron sputtering in a reactive atmosphere (Ar + CH4). An Ion Beam Analysis was used to determine the elemental depth profile across the coating thickness (giving both average C:W:H ratios and film density when combined with profilometer measurements of film thickness). The hardness was evaluated with nanoindentation, and a decrease from 16 to 6 GPa (and a decrease in the film density by a factor of two) with an increasing CH4 flow was observed. Then, the hardness and Raman results were correlated with the H content in the coatings, showing that these indirect methods can be used to find if there are variations in the H content with the increase in the CH4 flow. Finally, the adhesion and tribological performance of the coatings were evaluated. No significant differences were found in the adhesion as a function of the H content. The tribological properties presented a slight improving trend with the increase in the H content with a decrease in the wear rate and friction. [ABSTRACT FROM AUTHOR]

HfxZr1−xO2 (HZO) thin films have excellent potential for application in various devices, including ferroelectric transistors and semiconductor memories. However, such applications are hindered by the low remanent polarization (Pr) and fatigue endurance of these films. To overcome these limitations, in this study, HZO thin films were fabricated via plasma-enhanced atomic layer deposition (PEALD), and the effects of the deposition and post-annealing temperatures on the density, crystallinity, and electrical properties of the thin films were analyzed. The thin films obtained via PEALD were characterized using cross-sectional transmission electron microscopy images and energy-dispersive spectroscopy analysis. An HZO thin film deposited at 180 °C exhibited the highest o-phase proportion as well as the highest density. By contrast, mixed secondary phases were observed in a thin film deposited at 280 °C. Furthermore, a post-annealing temperature of 600 °C yielded the highest thin film density, and the highest 2Pr value and fatigue endurance were obtained for the film deposited at 180 °C and post-annealed at 600 °C. In addition, we developed three different methods to further enhance the density of the films. Consequently, an enhanced maximum density and exceptional fatigue endurance of 2.5 × 107 cycles were obtained.

The piping systems used for the transportation of liquids and gases in power stations, petroleum petrochemical facilities, and chemical plants are significantly impacted by corrosive processes. One of the most destructive forms of corrosion is pitting corrosion, which produces holes on piping metal surfaces. Monitoring pit depth is necessary in order to prevent leakage in the piping system, especially during operation. However, measuring pit depth as a part of periodical inspections is complicated since the pit depth on the outside wall of a pipe may vary. Non-destructive testing (NDT) methods such as ultrasonic, liquid penetrants, and magnetic particles are used to detect defects in industrial components; however, they first require the removal of insulation and the shutdown of the pipe system. Another alternative NDT technique, tangential radiography technique (TRT), offers a solution to this problem as tests can be conducted without removing piping insulation, allowing testing while the piping system is online. In this study, we tested TRT using an X-ray radiation source, which has good controllability (i.e., intensity and exposure time) and a lower impact on the human body than do γ-ray sources. We focused on the comparison of film density measurements using a density meter and a light meter. The magnification of pit diameter was used to obtain an equation for small-diameter pipes (i.e., diameter of less than 50 mm). The working voltage was varied (200, 230, and 260 kV) in order to generate appropriate X-ray energies to measure various pit depth (20, 40, and 60%, receptively) of a stepped steel pipe specimen. Film density measurements using the density and light meters showed similar results; however, the film density result using the density meter was more accurate. All tangential side edges of the specimen burned off for film densities above 3.5. Degrees of magnification (1.0123, 1.0254, and 1.0379) varied as a function of distance from the midpoint of the X-ray target (30, 60, or 90 mm, respectively). Using the results, a linear equation with three variables was obtained to determine the actual diameter of pitting: 0.000385436a + 0.038350128b + 0.000467083c = d; where the actual diameter = film diameter/d. High working voltage produced low film contrast, high film definition, and low scatter. Low working voltage produced high film contrast, low film definition, and high scatter. Based on our results, a working voltage of 260 kV is most appropriate for effective analysis. [ABSTRACT FROM AUTHOR]

Abstract SiO x N y barrier films were deposited at low temperature of ~ 23 °C using inductively coupled plasma chemical vapor deposition (ICP-CVD). When radio frequency power increased at constant ratios of Ar/SiH 4 and O 2 /(O 2 + N 2), respectively, of 4.5 and 0.1, the aggregation tendency of nanoparticles slightly decreased, whereas when the ratio of Ar/SiH 4 was changed from 4.5 to 41, almost spherical nanoparticles, each of which was isolated without aggregation, were observed. Such a near spherical nanoparticle without aggregation produced highly dense films with enhanced barrier property. However, heavily aggregated nanoparticles produced very porous films with deteriorated barrier property. In other words, the film density and barrier property depended significantly on whether nanoparticles were isolated or aggregated. To investigate the formation mechanism of dense SiO x N y barrier film, a transmission electron microscope grid membrane was exposed for 5 s to capture nanoparticles generated in the gas phase using a shutter above the grid membrane during ICP-CVD and the grid membrane was observed by scanning transmission electron microscope. The formation mechanism of the barrier film could be best explained by non-classical crystallization of CVD films, where nanoparticles formed in the gas phase contribute to the film formation. Highlights • SiO x N y barrier films were deposited by ICP-CVD. • Effects of gas ratio and plasma power on the nanoparticle characteristics were studied. • Gas ratio and plasma power greatly affect the film density and barrier property. • The formation of dense film could be explained by non-classical crystallization of CVD. [ABSTRACT FROM AUTHOR]

Among the various thin film coating techniques, atomic layer deposition (ALD) has features of good controllability of the thickness, excellent step-coverage in 3-dimensional object even in the sub-nm thickness range at the relatively low deposition temperature. In this study, SnO2 thin films were grown by ALD in the variation of substrate temperatures from 150 to 250°C. Even such a low temperature may influence on the growth kinetics of the ALD reaction and thus the physical characteristics of thin films, such as crystallinity, film density and optical band gap, etc. We observed the decrease of the growth rate with increasing substrate temperature, at the same time, the density of the film was decreased with increasing temperature. Steric hindrance effect of the precursor molecule was attributed to the inverse relationship of the growth temperature and growth rate as well as the film density. Optical indirect band gap energy (~3.6 eV) of the ALD-grown amorphous SnO2 films grown at 150°C was similar with that of the literature value, while slightly lower band gap energy (~3.4 eV) was acquired at the films grown at higher temperature.

Abstract The low deposition rate of the high power impulse magnetron sputtering (HiPIMS) somewhat limits its commercial applications in thin film and coating industries. In this work, an effective way to improve the deposition rate of TiN film by superimposing the middle-frequency (MF) pulses during off-time of HiPIMS pulsing was discussed. Superimposition of HiPIMS and MF fabricated TiN films with relatively smooth surface. All samples were found to have a single phase TiN according to the chemical composition and crystallographic analyses. The highest film hardness of ~ 31 GPa, elastic modulus of 313 GPa, and a density of 5.35 g/cm3 were obtained in the sample grown at a MF pulse duration of 150 μs in each superimposed cycle. The higher the deposition rate was achieved with longer MF pulse duration. This superimposition technique successfully improved the power-normalized deposition rate from 4.5 to 17.2 nm/kW·min without significantly declining the mechanical properties and adhesion quality of deposited films. The role of MF pulse duration and average MF power were further studied in this work. It can be concluded that the MF pulse duration played a more significant role and showed a dominant influence on the plasma characteristics and resulting properties of deposited TiN films. Highlights • The single phase TiN films are fabricated by the superimposed HiPIMS and MF deposition process. • Introduction of MF pulses during off-time of HiPIMS improves the deposition rate from 4.5 to 17.2 nm/kW·min. • MF pulse duration influences the plasma characteristics and resulting properties of TiN films. • A hardness of 31 GPa and a density of 5.35 g/cm3 TiN film is grown at a 150 μs MF on-time in each superimposed cycle. [ABSTRACT FROM AUTHOR]

In this study, we investigate the relationship between the physical densification and sub-gap density-of-states (DOS) distribution of a-IGZO films prepared under various deposition pressures. For TFTs with a-IGZO channel films, the field effect mobility increases from 10.9 to 24.8 cm 2 /V·s, and the on-current increases from 1.5 to 20.8 μA as the deposition pressure for the channel films decreases from 7 to 1 mTorr. The sub-gap DOS distributions obtained from the electrical characteristics indicate the changes in the density of accepter-like tail states with deposition pressure. Further, the physical densification of the channel films increases as the deposition pressure decreases. Our study demonstrates that the lower density of accepter-like tail states and the higher physical densification contribute to the improved performance of a-IGZO TFTs. [ABSTRACT FROM AUTHOR]

Among the various thin film coating techniques, atomic layer deposition (ALD) has features of good controllability of the thickness, excellent step-coverage in 3-dimensional object even in the sub-nm thickness range at the relatively low deposition temperature. In this study, SnO2 thin films were grown by ALD in the variation of substrate temperatures from 150 to 250°C. Even such a low temperature may influence on the growth kinetics of the ALD reaction and thus the physical characteristics of thin films, such as crystallinity, film density and optical band gap, etc. We observed the decrease of the growth rate with increasing substrate temperature, at the same time, the density of the film was decreased with increasing temperature. Steric hindrance effect of the precursor molecule was attributed to the inverse relationship of the growth temperature and growth rate as well as the film density. Optical indirect band gap energy (~3.6 eV) of the ALD-grown amorphous SnO2 films grown at 150°C was similar with that of the literature value, while slightly lower band gap energy (~3.4 eV) was acquired at the films grown at higher temperature. [ABSTRACT FROM AUTHOR]

Silicon oxide (SiOx) barrier films were deposited on polyethylene terephthalate (PET) substrate at 20 °C using reactive dual magnetron sputtering system. The oxygen flow rate, input sputtering power and film thickness were changed to optimize the barrier properties of SiOx films. Details of sputtering power and film thickness effects on the SiOx properties in terms of residual stress, surface, roughness, density, interface of SiOx/PET, and water vapor transmission rate (WVTR) were investigated. Especially, we focused our attention on the effects of sputtering power on the final barrier properties. A high density of 2.42 g/cm 3 SiOx film with high transmittance of 92% was obtained. Even at low substrate temperature of 20 °C, the 300 nm-thick SiOx barrier film exhibited superior WVTR value of 7.7 × 10 − 3 g/m 2 /day as a single barrier layer using roll to roll reactive sputtering. These experimental observations showed that the encapsulation barrier properties of SiOx films were significantly enhanced due to the change of effect of ion bombardment, which affected film density, surface roughness, and the interface of SiOx/PET. [ABSTRACT FROM AUTHOR]

A family of first-generation dendrimers containing 3,5-bis(carbazolyl)phenyl dendrons attached to a green emissive fac -tris(2-phenylpyridyl)iridium(III) core were prepared. The solubility of the dendrimers was imparted by the attachment of tert -butyl surface groups to the carbazole moieties. The dendrimers differed in the number of dendrons attached to each ligand (one or two dendrons) as well as the degree of rotational restriction within the dendrons. The densities of the films containing the doubly dendronized materials were higher than those of their mono-dendronized counterparts, with the dendrimer containing two rotationally constrained dendrons per ligand having the highest density at 1.12 ± 0.04 g cm -3 . The dendrimers were found to have high photoluminescence quantum yields (PLQYs) in solution of between 80 and 90%, with the doubly dendronized materials having the lower values and a red-shifted emission. The neat film PLQY values of the dendrimers were less than those measured in solution although the relative decrease was smaller for the doubly dendronized materials. The dendrimers were incorporated into solution-processed bilayer organic light-emitting diodes (OLEDs) composed of neat or blend emissive layers and an electron transport layer. The best-performing devices had the dendrimers blended with a host material and external quantum efficiencies as high as 14.0%, which is higher than previously reported results for carbazole-incorporating emissive dendrimers. A feature of the devices containing blends of the doubly dendronized materials was that the maximum efficiency was relatively insensitive to the concentration in the host between 1 and 7 mol %.

SiCN films were deposited by hot-wire chemical vapor deposition (HWCVD) method using hexamethyldisilazane (HMDS). These films contain a lot of oxygen. Using HMDS with NH 3 , low oxygen content films can be obtained. It is found from the structure determination that Si‐N bonds are the vital bonds of SiCN films. It is also found that the highest amount of Si‐N bonds content SiCN has the highest amount of nitrogen and the amount of nitrogen is directly related to the properties of the films. The amount of oxygen, film density, the refractive index and optical band gap are strong functions of the amount of nitrogen in the films. With increasing nitrogen, the amount of oxygen decreases and with decreasing nitrogen, the amount of oxygen increases. The film density and optical band gap also increase with increasing nitrogen. On the other hand with increasing nitrogen, the refractive index decreases. [ABSTRACT FROM AUTHOR]

Cu and Ag redox reactions at the interfaces with Ta2O5 and the impact of Ta2O5 film density on the forming process of Cu,Ag/Ta2O5/Pt atomic switch structures are investigated. Cyclic voltammetry measurements revealed that under positive bias to the Cu (Ag) electrode, Cu is preferentially oxidized to Cu2+, while Ag is oxidized to Ag+ ions. Subsequent negative bias causes a reduction of oxidized Cu (Ag) ions at the interfaces. The diffusion coefficient of the Cu and Ag ions in the Ta2O5 film is estimated from the results from different bias voltage sweep rates. It is also found that the redox current is enhanced and the forming voltage of the Cu/Ta2O5/Pt cell is reduced when the density of the Ta2O5 film is decreased. This result indicates the importance of the structural properties of the matrix oxide film in understanding and controlling resistive switching behavior. [ABSTRACT FROM AUTHOR]

Through detailed analyses, the structure of c-axis-aligned crystalline (CAAC) IGZO, which is a dense, stable crystal morphology, is found to differ from single-crystal and amorphous structures. We propose a model for determining its film deposition mechanism. CAAC-IGZO field-effect transistors find application in displays for use as human-machine interfaces. [ABSTRACT FROM AUTHOR]

Abstract: Strontium-containing titanium films were synthesized by non-reactive magnetron sputtering from elemental targets. Three series of depositions were carried out at (1) different relative Sr-to-Ti target powers, (2) different sputter-gas pressures, and (3) different bias voltages. Large amounts of oxygen were detected in films with high Sr concentrations as well as in films exhibiting a porous morphology. By the addition of Sr, amorphous regions appeared in the coatings with a corresponding reduction of the crystalline volume fraction. The amorphous phase fraction increased with increasing Sr content. Upon increasing the Sr contents to 7.2at.% and higher, completely X-ray amorphous coatings were obtained. However, from high-resolution transmission electron microscopy imaging of the film containing 7.2at.% Sr, Ti nanocrystals of the order ~6nm embedded in an amorphous matrix were observed. Furthermore, the absolute value of the floating potential increased with decreasing sputter-gas pressure, resulting in a more energetic ion bombardment of the growing films. Strong resputtering of strontium resulted in very low Sr concentrations in films deposited at floating potential and low gas pressures or with an applied bias voltage. Films deposited at floating potential and high gas pressures exhibited a porous columnar morphology and had low degrees of crystallinity with correspondingly small grain sizes (~9nm), whereas denser and more crystalline films with larger grains (~18nm) were obtained from depositions at floating potential and low gas pressures and from depositions with an applied bias voltage. Film hardness scaled linearly with film electron density, as evidenced from nanoindentation and X-ray reflectivity measurements. [Copyright &y& Elsevier]

Highlights: [ • ] Crystalline WO3 thin films by reactive sputtering technique. [•] Characterizations include: optical emission spectra from sputter plasma XRD, Raman, UV–vis, scanning electron microscopy and cyclic voltammetry. [ • ] Oxygen chamber pressure strongly influences structure and morphology of films. [•] Enhanced electrochromic activity in porous and less density films. [Copyright &y& Elsevier]