Synthesis of nano-crystalline zirconium aluminium oxynitride (ZrAlON) composite films by dense plasma Focus device

Zirconium aluminium oxynitride multiphase composite film is deposited on zirconium substrate using energetic nitrogen ions delivered from dense plasma Focus device. X-ray diffractometer (XRD) results show that five Focus shots are sufficient to initiate the nucleation of ZrN and Al₂O₃ whereas 10 Focus shots are sufficient to initiate the nucleation of AlN. XRD results reveal that crystal growth of nitrides/oxides increases by increasing Focus shots (up to 30 Focus shots) and resputtering of the previously deposited film is taken place by further increase in Focus shots (40 Focus shots). Scanning electron microscopic (SEM) results indicate the uniform distribution of spherical grains (∼35 nm). A smoother surface is observed for 20 Focus shots at 0° angular position. SEM results also show a net-type microstructure (thread like features) of the sample treated for 30 Focus shots whereas rough surface morphology is observed for 40 Focus shots. Energy dispersive spectroscopic profiles show the distribution of different elements present in the deposited composite films. A typical microhardness value of the deposited composite films is 5255 ± 10 MPa for 10 grams imposed load which is 3.3 times than the microhardness values of unexposed sample. The microhardness values of the exposed samples increases with increasing Focus shots (up to 30 Focus shots) and decreases for 40 Focus shots treatment due to resputtering of the previously deposited composite film. The microhardness values of the composite films decreases by increasing the sample's angular position.     

Mechanical properties of Al/a-C nanocomposite thin films synthesized using a plasma focus device

The Al/a-C nanocomposite thin films are synthesized on Si substrates using a dense plasma focus device with alu- minum fitted anode and operating with CH4/Ar admixture. X-ray diffractometer results confirm the formation of metallic crystalline Al phases using different numbers of focus shots. Raman analyses show the formation of D and G peaks for all thin film samples, confirming the presence of a-C in the nanocomposite thin films. The formation of Al/a-C nanocomposite thin films is further confirmed using X-ray photoelectron spectroscopy analysis. The scanning electron microscope results show that the deposited thin films consist of nanoparticles and their agglomerates. The sizes of th agglomerates increase with increasing numbers of focus deposition shots. The nanoindentation results show the variations in hardness and elastic modulus values of nanocomposite thin film with increasing the number of focus shots. Maximum values of hardness and elastic modulus of the composite thin film prepared using 20 focus shots are found to be about 10.7 GPa and 189.2 GPa, respectively.     

Synthesis of composite TiN/Ni3N/a-Si3N4 thin films using the plasma focus device

Composite films of TiN/Ni₃N/a-Si₃N₄ were synthesized using the Mather-type plasma focus device with varying numbers of focus deposition shots (5, 15, and 25) at 0° and 10° angular positions. The composition and structural analysis of these films were analyzed by using Rutherford backscattering (RBS) and X-ray diffraction (XRD). Scanning electron microscope and atomic force microscope were used to study the surface morphology of films. XRD patterns confirm the formation of composite TiN/Ni₃N/a-Si₃N₄ films. The crystallite size of TiN (200) plane is 11 and 22 nm, respectively, at 0° and 10° angular positions for same 25 focus deposition shots. Impurity levels and thickness were measured using RBS. Scanning electron microscopy results show the formation of net-like structures for multiple focus shots (5, 15, and 25) at angular positions of 0° and 10°. The average surface roughness of the deposited films increases with increasing focus shots. The roughness of the film decreases at higher angle 10° and the films obtained are smoother as compared with the films deposited at 0° angular positions.     

Nano-structured Fe thin film deposition using plasma focus device

This paper reports the deposition of nano-structured Fe thin films using 3.3 kJ Mather-type plasma focus. The conventional hollow copper anode was replaced by anode fitted with solid Fe top and the deposition was done using different numbers of deposition shots at two different angular positions. Scanning Electron Microscopy shows that the size of nano-phase agglomerate is smaller when the sample is deposited using either lesser number of deposition shots or at higher angular position with respect to anode axis. X-ray Diffraction shows that crystal structure characteristics change with increase in number of deposition shots. Measurements of magnetic properties using Vibrating Sample Magnetometer identify intermediate magnetization and coercivity in Fe thin films deposited at smaller angular position with respect to anode axis. It is concluded that the morphological, structural and magnetic characteristics of Fe thin films deposited using plasma focus device depend not only on the number of focus deposition shots but also on the angular position of the sample.     

Deposition of Au/TiO2 film by pulsed laser

Au nanoparticles, which were photoreduced by a Nd:YAG laser in HAuCl₄ solution containing TiO₂ colloid and accompanied by the TiO₂ particles, were deposited on the substrate surface. The film consisting of Au/TiO₂ particles was characterized by the absorption spectra, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The adhesion between the film and substrate was evaluated by using adhesive tape test. It was found that the presence of TiO₂ dramatically enhanced the adhesion strength between the film and the substrate, as well as the deposition rate of film. The mechanism for the deposition of Au/TiO₂ film was also discussed.     

Formation of silicon carbide in silicon substrates during CF4/H2 dry etching

Silicon specimens which had been reactive ion etched in CF₄/X%H₂ (0≤ X ≤40) and subsequently air exposed have been characterised by X-ray photoelectron emission spectroscopy. Angular rotation was used to study films deposited by the plasma process onto the Si surface. In agreement with previous studies it is found that plasma exposure of Si specimens leads to the deposition of a fluorocarbon film. An intriguing new finding was the discovery of subsurface silicon carbide. The existence of this carbide layer was found to be independent of gas composition from 0–40% H₂ for a one-minute plasma exposure. Helium ion channeling studies of the same specimens show Si near-surface disorder. A silicon-carbide formation mechanism is suggested according to which carbon is deposited below the Si surface by the bombardment of carbon containing ions, thus enabling silicon-carbon bonding.     

Effect of the oxygen flow rate on the structure and the properties of Ag-Cu-O sputtered films deposited using a Ag/Cu target with eutectic composition

Ag-Cu-O films were deposited on glass substrates by reactive sputtering of a composite Ag₆₀Cu₄₀ target in various Ar-O₂ mixtures. The films were characterised by energy dispersive X-ray analysis, X-ray diffraction, UV-visible spectroscopy and using the four point probe method. The structure of the films is strongly dependent on the oxygen flow rate introduced in the deposition chamber. The variation of the oxygen flow rate allows the deposition of the following structures: Ag-Cu-(O) solid solution, nc-Ag + nc-Cu₂O, nc-Ag + nc-(Ag,Cu)₂O and finally X-ray amorphous. UV-visible reflectance measurements confirm the occurrence of metallic silver into the deposited films. The increase of the oxygen flow rate induces a continuous increase of the film oxygen concentration that can be correlated to the evolution of the film reflectance and the film electrical resistivity. Finally, the structural changes vs. the oxygen content are discussed in terms of reactivity of sputtered atoms with oxygen.     

Low energy repetitive miniature plasma focus device as high deposition rate facility for synthesis of DLC thin films

Diamond-like carbon (DLC) films were deposited on Si (1 0 0) substrate using a low energy (219 J) repetitive (1 Hz) miniature plasma focus device. DLC thin film samples were deposited using 10, 20, 50, 100 and 200 focus shots with hydrogen as filling gas at 0.25 mbar. The deposited samples were analyzed by XRD, Raman Spectroscopy, SEM and XPS. XRD results exhibited the diffraction peaks related to SiO₂, carbon and SiC. Raman studies verified the formation amorphous carbon with D and G peaks. Corresponding variation in the line width (FWHM) of the D and G positions along with change in intensity ratio (I_D/I_G) in DLC films was investigated as a function of number of deposition shots. XPS confirmed the formation sp² (graphite like) and sp³ (diamond like) carbon. The cross-sectional SEM images establish the 220 W repetitive miniature plasma focus device as the high deposition rate facility for DLC with average deposition rate of about 250 nm/min.     

Photosensitization of nanocrystalline TiO2 film electrode with cadmium sulphoselenide

Nanocrystalline titanium dioxide (TiO₂) thin films composed of densely packed nanometer-sized grains have been successfully deposited onto an indium-doped-tin oxide (ITO) substrate. Then cadmium sulphoselenide (CdSSe) thin film was deposited onto pre-deposited TiO₂ to form a TiO₂/CdSSe film, at low temperature using a simple and inexpensive chemical method. The X-ray diffraction, selected area electron diffraction, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and water contact angle techniques were used for film characterization. Purely rutile phase of TiO₂ with super-hydrophilic and densely packed nanometer-sized spherical grains of approximate diameter 30-40 (±2) nm was observed. The increase in optical absorption was observed after CdSSe film deposition. Nest like surface morphology of CdSSe on TiO₂ surface results in air trapping in the crevices which prevents water from adhering to the film with increase in water contact angle. Photosensitization of TiO₂ with CdSSe was confirmed with light illumination intensity of 80 mW/cm².     

Effect of substrate and annealing on the structural and optical properties of ZnO:Al films

ZnO:Al thin films with c-axis preferred orientation were deposited on glass and Si substrates using RF magnetron sputtering technique. The effect of substrate on the structural and optical properties of ZnO:Al films were investigated. The results showed a strong blue peak from glass-substrate ZnO:Al film whose intensity became weak when deposited on Si substrate. However, the full width at half maxima (FWHM) of the Si-substrate ZnO:Al (0 0 2) peaks decreased evidently and the grain size increased. Finally, we discussed the influence of annealing temperature on the structural and optical properties of Si-substrate ZnO:Al films. After annealing, the crystal quality of Si-substrate ZnO:Al thin films was markedly improved and the intensity of blue peak (∼445 nm) increased noticeably. This observation may indicate that the visible emission properties of the ZnO:Al films are dependent more on the film crystallinity than on the film stoichiometry.     

Dielectric property of CaCu3Ti4O12 thin film grown on Nb-doped SrTiO3(100) single crystal

Thin film of CaCu₃Ti₄O₁₂ (CCTO) has been deposited on Nb-doped SrTiO₃(100) single crystal using pulsed laser deposition. The dielectric constant and AC conductivity of CCTO film in the metal–insulator–metal capacitor configuration over a wide temperature (80 to 500 K) and frequency (100 Hz to 1 MHz) range have been measured. The small dielectric dispersion with frequency observed in the lower temperature region (<300 K) indicates the presence of small defects in the deposited CCTO thin film. The frequency-dependent AC conductivity at lower temperature indicates the hopping conduction. The dielectric dispersion data has been analyzed in the light of both conductivity relaxation and Debye type relaxation with a distribution of relaxation times. Origin of dielectric dispersion is attributed to the distribution of barrier heights such that some charge carriers are confined between long-range potential wells associated with defects and give rise to dipolar polarization, while those carriers which do not encounter long-range potential well give rise to DC conductivity.     

Mössbauer study of the pulsed laser deposition of polycrystalline magnetic films

Polycrystalline magnetite films were grown by pulsed laser deposition from an α-Fe₂O₃ target at 450 °C. X-ray diffraction analysis showed the presence of a single-phase spinel film with preferred orientation when the deposition was performed at low oxygen pressure. Mössbauer spectroscopy at both room temperature and 120 K was used to identify the hyperfine parameters of the magnetite film deposited on glass at 450 °C and at an oxygen partial pressure of 10⁻⁴ Torr.     

Evolution of the structural and optical properties of silver oxide films with different stoichiometries deposited by direct-current magnetron reactive sputtering

Nitrogen doping of silver oxide(AgxO) film is necessary for its application in transparent conductive film and diodes because intrinsic AgxO film is a p-type semiconductor with poor conductivity.In this work,a series of AgxO films is deposited on glass substrates by direct-current magnetron reactive sputtering at different flow ratios(FRs) of nitrogen to O2.Evolutions of the structure,the reflectivity,and the transmissivity of the film are studied by X-ray diffractometry and sphectrophotometry,respectively.The specular transmissivity and the specular reflectivity of the film decreasing with FR increasing can be attributed to the evolution of the phase structure of the film.The nitrogen does not play the role of an acceptor dopant in the film deposition.     

Pulsed laser deposition of NiTi shape memory effect thin films

2 O₃(100) substrates. We also produced free-standing NiTi films by deposition on KBr substrates and subsequent substrate removal by immersion in water. The presence of the solid-solid phase transformation responsible for the shape memory effect has been demonstrated through temperature-dependent X-ray diffraction and four-probe resistance versus temperature measurements. On cooling the deposited film, the austenite-martensite transformation was measured at around 195 K; on heating the film the reverse transformation was around 250 K. Evidence of the shape-memory effect for free-standing films was obtained in a bending deformation-shape recovery experiment. Received: 31 July 1996/Accepted: 6 January 1997     

Structural and mechanical properties of Al–C–N films deposited at room temperature by plasma focus device

The Al–C–N films are deposited on Si substrates by using a dense plasma focus(DPF) device with aluminum fitted central electrode(anode) and by operating the device with CH_4/N_2 gas admixture ratio of 1:1. XRD results verify the crystalline Al N(111) and Al_3CON(110) phase formation of the films deposited using multiple shots. The elemental compositions as well as chemical states of the deposited Al–C–N films are studied using XPS analysis, which affirm Al–N, C–C, and C–N bonding. The FESEM analysis reveals that the deposited films are composed of nanoparticles and nanoparticle agglomerates. The size of the agglomerates increases at a higher number of focus deposition shots for multiple shot depositions. Nanoindentation results reveal the variation in mechanical properties(nanohardness and elastic modulus)of Al–C–N films deposited with multiple shots. The highest values of nanohardness and elastic modulus are found to be about 11 and 185 GPa, respectively, for the film deposited with 30 focus deposition shots. The mechanical properties of the films deposited using multiple shots are related to the Al content and C–N bonding.     

X-ray photoelectron spectroscopy of Se films grown by hot wall epitaxy

The X-ray photoelectron spectroscopy (XPS) performed on Se films obtained by vacuum deposition and hot wall epitaxy (HWE) indicated shifts in the binding energies of the core-levels. The observed shift of 3.5 eV in the XPS spectrum of 3d level towards the higher binding energy in vacuum deposited film was associated with the Se₈ molecular state. On the other hand, the 3d-level XPS spectrum of Se films grown by HWE indicated an assymmetrical doublet. From the peak positions it was ascertained that the film was retained its bulk characteristic and a partial shift of 2.6 eV was interpretated for the presence of Se₆ molecules.     

Simultaneous determination of thermal conductivities of thin film and substrate by extending 3ω-method to wide-frequency range

A technique using 3ω-method with a wide-frequency range from 0.5 Hz to 0.5 MHz was developed to determine simultaneously the thermal conductivities of individual layers in a two-layered structure. The technique utilizes 3ω measurements in high and low frequency ranges separately. To evaluate the validity and accuracy of the technique, we performed measurements on a double-layered specimen consisting of a SiO₂-film on a Si-substrate, and found that the measured conductivities of both the film and substrate agree well with literature values. Uncertainty analysis was given finally. This new technique overcomes a critical shortcoming of conventional techniques, which cannot measure the thermal conductivity of both film and substrate simultaneously.     

Prototype electrochromic device and dye sensitized solar cell using spray deposited undoped and ‘Li’ doped V2O5 thin film electrodes

Lithium (Li) (0–5 wt%) doped V₂O₅ thin films were spray deposited at 450 °C onto ITO substrates. Structural analysis using X-ray diffraction and Raman spectroscopy revealed orthorhombic phase of the films. In addition to the V₂O₅ phase, presence of VO₂ peaks due to high deposition temperature is also evident from structural and optical characterization. The non-stoichiometric nature of the films due to loss of the terminal O atom was confirmed from Raman spectroscopy. The direct band gap, indirect bandgap, and phonon energies were also calculated from optical studies. Different charge states of vanadium ions present in the film were identified from X-ray photoelectron spectroscopy study. Results from cyclic voltammetry experiments reflected significant differences between the undoped and Li doped V₂O₅ samples. Transport properties by Hall-effect measured at room temperature indicated significant increase in conductivity, carrier concentration and mobility of V₂O₅ thin films on doping with Li. A Dye Sensitized Solar Cell (DSSC) was fabricated using mobility enhanced 5 wt% Li doped V₂O₅ film as photoanode and its efficiency was found to be 2.7%. A simple electrochromic cell is fabricated using undoped V₂O₅ thin film to demonstrate the colour change.     

Properties of Fe/Si heterostructure grown by MOCVD

An Fe film was grown on an Si(100) substrate by metalorganic chemical vapor deposition (MOCVD) using thermal decomposition of iron pentacarbonyl, Fe(CO)₅. The X-ray diffraction and cross-sectional high resolution electron microscopy (HREM) show that the Fe deposited film is a single crystal Fe film on Si(100). Single crystal Fe/Si Schottky barrier diodes exhibit good rectification.     

Pulsed laser deposition of high temperature protonic films

Pulsed laser deposition has been used to fabricate nanostructured BaCe_0.85Y_0.15O_3−δ films. Protonic conduction of the fabricated BaCe_0.85Y_0.15O_3−δ films was compared to the sintered BaCe_0.85Y_0.15O_3−δ. Sintered samples and laser targets were prepared by sintering BaCe_0.85Y_0.15O_3−δ powders derived by solid state synthesis. Films 1 to 8 μm thick were deposited by KrF excimer laser on porous Al₂O₃ substrates. Thin films were fabricated at deposition temperatures of 700 to 950 °C at O₂ pressures up to 200 mTorr using laser pulse energy densities of 1.4–3 J/cm². Fabricated films were characterized by X-ray diffraction, electron microscopy and electrical impedance spectroscopy. Single phase BaCe_0.85Y_0.15O_3−δ films with a columnar growth morphology are observed with preferred crystal growth along the [100] or [001] direction. Results indicate [100] growth dependence upon laser pulse energy. Electrical conductivity of bulk samples produced by solid state sintering and thin film samples were measured over a temperature range of 100 to 900 °C. Electrical conduction behavior was dependent upon film deposition temperature. Maximum conductivity occurs at deposition temperature of 900 °C; the electrical conductivity exceeds the sintered specimen. All other deposited films exhibit a lower electrical conductivity than the sintered specimen. Activation energy for electrical conduction showed dependence upon deposition temperature, it varied from 115 to 54 kJ. Film microstructure was attributed to the difference in electrical conductivity of the BaCe_0.85Y_0.15O_3−δ films.