Microstructure and characterization of La2O3 and CeO2 doped diamond-like carbon nanofilms

Seven kinds of hydrogen-free La₂O₃ and CeO₂ doped DLC films with thickness of 220-280 nm were deposited on Si (100) substrates by unbalanced magnetron sputtering. Nanoparticles with diameter of 20-30 nm are formed on the surface of films. The surface roughness Ra of films is in the range of 1.5-2.0 nm. C, La, Ce and O elements distribute uniformly along the depth direction, and C, La, and Ce elements diffuse into the Si substrate at the interface. X-ray photoelectron spectroscopy confirms that the La₂O₃ and CeO₂ form within the DLC amorphous films, and Raman spectra indicate the obvious amorphous characteristics of DLC films. High-resolution transmission electron microscopy shows the nanocrystallines structure with diameter of 2-3 nm of 16% La₂O₃ and 10% CeO₂ doped DLC films, and Fourier transformation spectroscopy also exhibits the obvious crystalline characteristics. In this work, the microstructure of two kinds of rare earth oxides doped DLC composite films is measured and analyzed.     

Mechanical properties of La2O3 doped diamond-like carbon films

Twelve La₂O₃ doped diamond-like carbon (DLC) nanofilms were deposited using unbalanced dual-magnetron sputtering. AFM, XRD, Raman spectroscopy, AES, XPS, TEM, contact surface profiler and nanoindenter were employed to investigate the structure and tribological properties of deposited films. The results show that the La₂O₃ doped DLC films are amorphous. La₂O₃ doping obviously decreases internal stress, and effectively increases the elastic modulus. This results from the dissolving and dissolution of La₂O₃ within the amorphous DLC matrix. Furthermore, the friction coefficient of the doped DLC films decreases, and adhesion strength increases. These are attributed to the lubrication function of La₂O₃ and the formation of transition layer at interface, respectively.     

Microwave ECR plasma CVD of cubic Y2O3 coatings and their characterization

Yttrium oxide (Y₂O₃) thin films are deposited by microwave electron cyclotron resonance (ECR) plasma assisted metal organic chemical vapour deposition (MOCVD) process at a substrate temperature of 350 °C using indigenously developed metal organic precursors (2,2,6,6-tetra methyl-3,5-heptane dionate) yttrium, commonly known as Y(thd)₃ synthesized by ultrasound method. The deposited coatings are characterized by X-ray photoelectron spectroscopy, glancing angle X-ray diffraction, scanning electron microscopy, EDS and infrared spectroscopy. The characterization results indicate that it is possible to deposit non-porous coatings with excellent uniformity of a single phase cubic Y₂O₃ on various substrates by this process at reasonably low substrate temperature that is desirable in various manufacturing processes.     

Synthesis of nanocrystalline nickel-zinc ferrite (Ni0.8Zn0.2Fe2O4) thin films by chemical bath deposition method

The nickel-zinc ferrite (Ni_0.8Zn_0.2Fe₂O₄) thin films have been successfully deposited on stainless steel substrates using a chemical bath deposition method from alkaline bath. The films were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), static water contact angle and cyclic voltammetry measurements. The X-ray diffraction pattern shows that deposited Ni_0.8Zn_0.2Fe₂O₄ thin films were oriented along (3 1 1) plane. The FTIR spectra showed strong absorption peaks around 600 cm⁻¹ which are typical for cubic spinel crystal structure. SEM study revealed compact flakes like morphology having thickness ∼1.8 μm after air annealing. The annealed films were super hydrophilic in nature having a static water contact angle (θ) of 5°.The electrochemical supercapacitor study of Ni_0.8Zn_0.2Fe₂O₄ thin films has been carried out in 6 M KOH electrolyte.The values of interfacial and specific capacitances obtained were 0.0285 F cm⁻² and 19 F g⁻¹, respectively.     

Controlling the particle size of nanobrookite TiO2 thin films

In this study, pure nanobrookite TiO₂ thin films were successfully deposited on glass substrates with the spin-coating method using titanium butoxide and acetic acid. The particle size of TiO₂ films was controlled by the water:AcAc volume ratio. This study shows that it is possible to obtain single oriented pure brookite films. The structural and optical properties of the nanobrookite TiO₂ thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), ultraviolet-visible spectroscopy (UV-vis), scanning electron microscopy (SEM), spectrophotometer (NKD), and Fourier transform infrared spectrometer (FTIR).     

Surfactant assisted electrodeposition of MnO2 thin films: Improved supercapacitive properties

In order to obtain a high specific capacitance, MnO₂ thin films have been electrodeposited in the presence of a neutral surfactant (Triton X-100). These films were further characterized by means of X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM) and contact angle measurement. The XRD studies revealed that the electrodeposited MnO₂ films are amorphous and addition of Triton X-100 does not change its amorphous nature. The electrodeposited films of MnO₂ in the presence of the Triton X-100 possess greater porosity and hence greater surface area in relation to the films prepared in the absence of the surfactant. Wettability test showed that the MnO₂ film becomes superhydrophilic from hydrophilic due to Triton X-100. Supercapacitance properties of MnO₂ thin films studied by cyclic voltammetry, galvanostatic charge-discharge cycling and impedance spectroscopy showed maximum supercapacitance for MnO₂ films deposited in presence of Triton X-100 is 345 F g⁻¹.     

O2 plasma treatment of mesoporous and compact TiO2 photovoltaic films: Revealing and eliminating effects of Si incorporation

Radio frequency (13.56 MHz) O₂ plasmas were used to modify the surface of mesoporous and compact TiO₂ films. The effects of substrate location in the plasma, applied rf power, and plasma mode (pulsed or continuous wave) were explored. X-ray photoelectron spectroscopy, contact angle measurements, and scanning electron microscopy were used to characterize changes to the TiO₂ films. For mesoporous materials, O₂ plasma treatment was found to increase oxygen content in the films, but Si content increased with applied rf power as a result of sputtering and redeposition of Si species from the reactor walls. XPS depth profiling using ion sputtering as well as O₂ plasma treatment of dyed materials revealed that Si was deposited throughout the mesoporous network, not as a surface SiO₂ layer. Pulsing the plasma with pulse duty cycles < 40% resulted in the elimination of Si and a reduction of damage in the modified films.     

Microstructure and tribological properties of the a-C:H films deposited by magnetron sputtering with CH4/Ar mixture

Hydrogenated amorphous carbon (a-C:H) films were deposited on steel and silicon wafers by unbalanced magnetron sputtering under different CH₄/Ar ratios. Microstructure and properties of the a-C:H films were investigated via Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Atomic force microscopy (AFM) and substrate curvature method. The results revealed that CH₄/Ar ratio played an important role in the H content but acted a little function on the sp³/sp² ratio of the films. Also, the internal stress of those films was relatively low (< 1 GPa), and the deposition rate decreased firstly and then increased with the decrease of the CH₄ fraction. The film deposited under CH₄/Ar = 1/1 (55 sccm/55 sccm) with moderate sp³ C-H / sp³ C-C had the best tribological properties. The composition, microstructure and properties of the a-C:H films were strongly dependent on the deposition process and composition of reactant gases.     

Synthesis-structure relations for reactive magnetron sputtered V2O5 films

V₂O₅ films were grown onto MgO (100) substrates by reactive magnetron sputtering between 26 °C to 300 °C to establish a detailed synthesis-structure relation. The effect of deposition temperature on structural characteristics and surface morphology was characterized using X-ray diffraction, Raman spectroscopy, atomic force microscopy and scanning and transmission electron microscopy. Films prepared at room temperature are amorphous while those deposited above 80 °C exhibit a polycrystalline structure with the orthorhombic symmetry of the V₂O₅ phase.     

Influence of O2/Ar flow ratio on the structure and optical properties of sputtered hafnium dioxide thin films

Hafnium dioxide (HfO₂) thin films were deposited on a quartz substrate by RF reactive magnetron sputtering. The influence of O₂/Ar flow ratio on the deposition rate, structure and optical properties of HfO₂ thin films were systematically studied using X-ray diffraction (XRD), scan electron microscopy (SEM) and UV-visible spectroscopy. The results show that the deposition rate decreases obviously when the O₂/Ar flow ratio increases from 0 to 0.25 and then, decreases little as the O₂/Ar flow ratio further increases to 0.50. The HfO₂ thin films prepared are all polycrystalline with a monoclinic phase. The thin film deposited with pure argon shows a preferential growth and has considerably improved crystallinity and much larger crystallite size. Meanwhile, after oxygen is introduced into the deposition, the thin films prepared have random orientation, weakened crystallinity and smaller crystallite size. The refractive index is higher for the thin film deposited without oxygen and increases as the O₂/Ar flow ratio increases from 0.25 to 0.50. The band gap energy of the thin film increases with an increasing O₂/Ar flow ratio.     

Influence of heat treatment on the particle size of nanobrookite TiO2 thin films produced by sol-gel method

Pure nanobrookite titania (TiO₂) thin films were deposited on glass substrates by the spin-coating method using titanium butoxide and acetic acid. The particle sizes of TiO₂ films were controlled by heat treatment temperatures. The activation energy for particle growth was calculated as 23.1 kJ/mol. The structural and optical properties of the nanobrookite TiO₂ thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), ultraviolet-visible absorption spectroscopy (UV-vis), and Fourier transform infrared spectroscopy (FTIR).     

Low temperature growth of nanocrystalline TiO2 films with Ar/O2 low-field helicon plasma

TiO₂ thin films were deposited on silicon wafer substrates by low-field (1 < B < 5 mT) helicon plasma assisted reactive sputtering in a mixture of pure argon and oxygen. The influence of the positive ion density on the substrate and the post-annealing treatment on the films density, refractive index, chemical composition and crystalline structure was analysed by reflectometry, Rutherford backscattering spectroscopy (RBS) and X-ray diffraction (XRD). Amorphous TiO₂ was obtained for ion density on the substrate below 7 × 10¹⁶ m^− 3. Increasing the ion density over 7 × 10¹⁶ m^− 3 led to the formation of nanocrystalline (~ 15 nm) rutile phase TiO₂. The post-annealing treatment of the films in air at 300 °C induced the complete crystallisation of the amorphous films to nanocrystals of anatase (~ 40 nm) while the rutile films shows no significant change meaning that they were already fully crystallised by the plasma process. All these results show an efficient process by low-field helicon plasma sputtering process to fabricate stoichiometric TiO₂ thin films with amorphous or nanocrystalline rutile structure directly from low temperature plasma processing conditions and nanocrystalline anatase structure with a moderate annealing treatment.     

P-type transparent conducting SnO2:Zn film derived from thermal diffusion of Zn/SnO2/Zn multilayer thin films

Highly transparent, p-type conducting SnO₂:Zn thin films are prepared from the thermal diffusion of a sandwich structure of Zn/SnO₂/Zn multilayer thin films deposited on quartz glass substrate by direct current (DC) and radio frequency (RF) magnetron sputtering using Zn and SnO₂ targets. The deposited films were annealed at various temperatures for thermal diffusion. The effect of annealing temperature and time on the structural, electrical and optical performances of SnO₂:Zn films was studied. XRD results show that all p-type conducting films possessed polycrystalline SnO₂ with tetragonal rutile structure. Hall effect results indicate that the treatment at 400 °C for 6 h was the optimum annealing parameters for p-type SnO₂:Zn films which have relatively high hole concentration and low resistivity of 2.389 × 10¹⁷ cm^− 3 and 7.436 Ω cm, respectively. The average transmission of the p-type SnO₂:Zn films was above 80% in the visible light range.     

Optical properties of thermally evaporated Bi2Se3 thin films treated with AgNO3 solution

Bismuth selenide (Bi₂Se₃) thin films have been prepared onto clean glass substrates by the thermal evaporation technique. The deposited films were then immersed in silver nitrate solution for different periods of time, followed by annealing in Argon atmosphere at 473 K for 1 h, to obtain Ag/Bi₂Se₃ samples. The prepared films have been examined by X-ray and transmission electron microscopy for structural determination. The optical transmission and reflection spectra of the deposited films have been recorded within the wavelength range 400-2500 nm. The variation of the optical parameters of the prepared films, such as refractive index, n, and the optical band gap, E_g as a function of the immersion duration times has been determined. The refractive index dispersion in the transmission and low absorption region is adequately described by the well-known Sellmeier dispersion relation, whereby the values of the oscillator strength, oscillator position, the high-frequency dielectric constant, ε_∞ as well as the carrier concentration to the effective mass ratio, N/m* were calculated as a function of the immersion duration time.     

Corrosion characteristics of LiBH4 film exposed to a CO2/H2O/O2/N2 mixture

LiBH₄ films were prepared by pulsed laser deposition using a LiB target in a background pressure of hydrogen. The corrosion characteristics of LiBH₄ films were measured by exposing them to a gas mixture of CO₂/H₂O/O₂/N₂ at ambient temperature for 1–24 h. Scanning electron microscopy images show some cracks on the surface of corrosion films, which could act as easy paths for H₂O and CO₂ to further react with Li⁺ and B³⁺. The X-ray photoelectron spectroscopy results and theoretical analysis show that LiBH₄ tends to react with H₂O and CO₂ to form Li₂B₄O₇, Li₂CO₃ and LiOH during the corrosion process.     

Study of bactericidal efficiency of magnetron sputtered TiO2 films deposited at varying oxygen partial pressure

TiO₂ thin films have been deposited at different Ar:O₂ gas ratios (20:80,70:30,50:50,and 40:60 in sccm) by rf reactive magnetron sputtering at a constant power of 200 W. The formation of TiO₂ was confirmed by X-ray photoelectron spectroscopy (XPS). The oxygen percentage in the films was found to increase with an increase in oxygen partial pressure during deposition. The oxygen content in the film was estimated from XPS measurement. Band gap of the films was calculated from the UV-Visible transmittance spectra. Increase in oxygen content in the films showed substantial increase in optical band gap from 2.8 eV to 3.78 eV. The Ar:O₂ gas ratio was found to affect the particle size of the films determined by a transmission electron microscope (TEM). The particle size was found to be varying between 10 and 25 nm. The bactericidal efficiency of the deposited films was investigated using Escherichia coli (E. coli) cells under 1 h UV irradiation. The growth of E. coli cells was estimated through the Optical Density measurement by UV-Visible absorbance spectra. The qualitative analysis of the bactericidal efficiency of the deposited films after UV irradiation was observed through SEM. A correlation between the optical band gap, particle size and bactericidal efficiency of the TiO₂ films at different argon:oxygen gas ratio has been studied.     

Structural, morphological and electrical properties of spray deposited nano-crystalline CeO2 thin films

Nanocrystalline, uniform, dense, and adherent cerium oxide (CeO₂) thin films have been successfully deposited by a simple and cost effective spray pyrolysis technique. CeO₂ films were deposited at low substrate and annealing temperatures of 350 °C and 500 °C, respectively. Films were characterized by differential thermal analysis, X-ray diffraction, scanning electron microscopy, atomic force microscopy; two probe resistivity method and impedance spectroscopy. X-ray diffraction analysis revealed the formation of single phase, well crystalline thin films with cubic fluorite structure. Crystallite size was found to be in the range of 10-15 nm. AFM showed formation of smooth films with morphological grain size 27 nm. Films were found to be highly resistive with room temperature resistivity of the order of 10⁷ Ω cm. Activation energy was calculated and found to be 0.78 eV. The deposited film showed high oxygen ion conductivity of 5.94 × 10⁻³ S cm⁻¹ at 350 °C. Thus, the deposited material shows a potential application in intermediate temperature solid oxide fuel cells (IT-SOFC) and might be useful for μ-SOFC and industrial catalyst applications.     

Structural characterization of amorphous hydrogenated-carbon nitride (aH-CNx) film deposited by CH4/N2 dielectric barrier discharge plasma: C, H solid state NMR, FTIR and elemental analysis

The chemical composition and bond structure of polymer like amorphous hydrogenated carbon nitride (aH-CN_x) thin films was studied by solid-state ¹³C and ¹H MAS NMR spectroscopy, FTIR spectroscopy and elemental analysis. The hydrogenated CN_x film was deposited on Si (100) substrate by CH₄/N₂ gas mixture dielectric barrier discharge (DBD) plasma. The broad ¹H signals obtained even at 33 kHz spinning speed with spinning side bands indicates the existence of a large proton proportion in the film. The ¹H and ¹³C signals are strongly broadened due to homo- and heteronuclear dipolar couplings and also due to amorphous nature of the deposited film. The local structure of the amorphous aH-CN_x film is dominated by C-C and C-N single bonds i.e. carbon is mainly in the sp³ hybridized state. The Fourier Transform infrared (FTIR) spectroscopy of the film indicates the typical regions for -C≡N, -(CO), -NH, vibrations together with overlapping NH and OH stretching bonds. CH₃ and C-N groups as well as species with CN conjugated double bonds are present in the deposited CN_x film. From elemental analysis it is obtained that the composition of the film is (in wt.%): C: 61.8, H: 8.4, N: 17.7.     

Characterization of nanostructured Cr2Nx/Cu multilayers deposited by reactive DC magnetron sputtering

Nitride/metal nanostructured multilayers of Cr₂N_x/Cu were deposited by reactive DC magnetron sputtering with various bilayer periods (2.5-30 nm) and substrate temperatures (25-400 °C). All films had a total thickness of about 470 nm and the overall chemical composition of the chromium nitride layers was close to Cr₂N_0.8. The deposited films were characterized by Rutherford Backscattering (RBS), low-angle X-ray reflectivity (XRR), high-angle X-ray diffraction (XRD) and transmission electron microscopy (TEM). The hardness and elastic modulus were measured by nanoindentation. The films deposited at 25 °C had a well-defined multilayer structure and the chromium nitride layers were found to crystallize into N-deficient fcc CrN_0.4 with traces of hexagonal Cr₂N_0.8. The layers were strongly textured with fcc CrN_0.4[002] and Cu[002] oriented along the growth direction — the fcc CrN_0.4 and Cu grains growing with a cube-on-cube relationship. The measured hardness values were about 8 GPa, and showed no dependence on the bilayer period. Higher deposition temperatures caused the multilayer structure to degrade, and at 400 °C the films were better described as non-textured nanocomposites with the chromium nitride crystallized entirely into the equilibrium hexagonal Cr₂N_0.8 structure. Hardness values of the high-temperature films in the range of 4-8 GPa were measured. Multilayer films deposited at 25 °C were found to be thermally stable against post-deposition annealing at temperatures up to about 400 °C. Annealing at 500 °C caused severe structural changes — the fcc CrN_0.4 phase transformed into hexagonal Cr₂N_0.8 accompanied by degradation of the periodic multilayer structure. The hardness decreased from the originally 8 GPa to about 5 GPa upon annealing.     

Microstructures of SiO2 and TiOX films deposited by atmospheric pressure inductively coupled micro-plasma jet

Atmospheric-pressure inductively coupled micro-plasma jet was used for deposition of SiO₂ and TiO_x thin films. Si and Ti alkoxides respectively were vaporized into Ar gas to be decomposed thermally in the Ar plasma jet, being deposited as the metal oxide films. Microstructures of the films were investigated as changing the plasma conditions such as Ar gas flow rate and concentration of the alkoxides in Ar gas. The SiO₂ and TiO_x films deposited at higher Ar gas flow rates were composed of particles of micron or submicron sizes. The SiO₂ film was composed of a single layer of the particles and the particles sometimes formed unique aggregation structures. On the other hand, the TiO_x film had a structure in which the particles were piled up randomly. The structures suggested that the SiO₂ particles grew on the substrate whereas TiO_x particles were formed in plasma gas phase.