Focus Shots Research Articles

Process Development and Optimization of Carbon-Based Thin Film Deposition through Ablation of Graphite

This paper reports the deposition of carbon nanomaterials on silicon substrate using a dense plasma focus device. The film property is studied using a field emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDX). The first test was deposited using 1, 3, 5, and 7 focus shots while the second test was carried out using 1 focus shot at 2, 3, 4, 5 and 7 Torr. Both tests were conducted with neon as filling gas at 7 Torr at distance of 8cm from the anode tip. In the first test, FESEM images exhibit a non-homogenous, non-uniformed and largely agglomerated carbon deposition at all films as pressure of filling gas increases. The EDX mapping confirms that carbon content in substrate increases from 10% to 30% as number of shot increases, and there is more carbon content detected in the centre position than the off-centre position. There is also a decrease in carbon content 35% to 25% as pressure of gas increases.

Structural, morphological and mechanical properties of niobium nitride thin films grown by ion and electron beams emanated from plasma

ABSTRACTThe influence of variation in plasma deposition parameters on the structural, morphological and mechanical characteristics of the niobium nitride films grown by plasma-emanated ion and electron beams are investigated. Crystallographic investigation made by X-ray diffractometer shows that the film synthesized at 10 cm axial distance with 15 plasma focus shots (PFS) exhibits better crystallinity when compared to the other deposition conditions. Morphological analysis made by scanning electron microscope reveals a definite granular pattern composed of homogeneously distributed nano-spheroids grown as clustered particles for the film synthesized at 10 cm axial distance for 15 PFS. Roughness analysis demonstrates higher rms roughness for the films synthesized at shorter axial distance and by greater number of PFS. Maximum niobium atomic percentage (35.8) and maximum average hardness (19.4 ± 0.4 GPa) characterized by energy-dispersive spectroscopy and nano-hardness analyzer respectively are observed for film synthesized at 10 cm axial distance with 15 PFS.

Characterization of nanostructured zinc oxide thin films synthesized at room temperature using low energy plasma focus device

Nanocrystalline zinc oxide (ZnO) thin films were synthesized on glass substrates under extremely non-equilibrium conditions of energetic ion condensation during the focus phase in a low energy plasma focus (PF) device. The samples were deposited using multiple focus shots (5, 10 and 20), at constant axial and angular positions with respect to the tip of anode and anode axis (8cm and 0°), respectively. The argon:oxygen admixture (in 7:3 ratio) was used as a working gas. The structural, morphological, electrical and optical properties of the ZnO deposited thin films were investigated. The results obtained from XRD and SEM analyzes indicated that the size of nanoparticles/agglomerates and the thickness of the ZnO thin films strongly depend on number of shots. AFM analysis revealed that the size of grains and surface roughness of ZnO samples increase with the number of shots. Measurement of the electrical parameters indicated that electrical resistivity is reduced and carrier mobility enhanced with increasing the shots, with no noticeable variations in the carrier concentration. Moreover, the results from optical transmission patterns revealed that optical transmittance and band gap energy decrease with more shots.

Dense Plasma Focus Device Based High Growth Rate Room Temperature Synthesis of Nanostructured Zinc Oxide Thin Films

High-energy-density plasmas in plasma focus device are now routinely being used as nonconventional plasma nanotechnology tool with novel processing and deposition parameters which are not available in conventional lowtemperature plasma facilities. This paper reports the synthesis of multilayered polycrystalline intrinsic defects-free nanostructured zinc oxide (ZnO) thin film onto room-temperature silicon substrates at high growth rates using pulsed high-energy-density dense plasma focus device. The device was operated in pure oxygen environment and the ablation target used was a pure zinc rod fitted onto the anode top. Thin films of ZnO were deposited at room temperature using different numbers of dense plasma focus shots and at different distances from the anode top. The as-deposited ZnO showed the formation of polycrystalline hexagonal phase ZnO thin films with strong c-axis orientation. The scanning electron microscopy results showed either uniformly laid nanoparticles or cauliflower aggregates of nanoparticles on the surface of the thin-film samples with average nanoparticle size varying between 23.3 ± 6.1 and 69.7 ± 16.5 nm. The average thicknesses of the multilayered thin films were measured to be in a range of 1.06 ± 0.14 to about 2.82 ± 0.32 μm. The complete disappearance of deep level emission band in photoluminescence spectrum of ZnO thin-film sample deposited using 30 focus shots at deposition distance of 15 cm showed successful synthesis of high crystalline quality intrinsic defects-free as-deposited ZnO thin film. One of the key features of the ZnO thin-film synthesis using nonconventional plasma focus device is the very high average growth rate of about 0.1 μm/shot. At one plasma focus shot per minute operation, the average growth rate comes out to be 0.1 μm/min, which is either higher or comparable with commonly used ZnO deposition methods; but at 10 Hz operation extreme growth rates of about 60 μm/min could be achieved.

Role of Nitrogen Pressure on the Structural and Mechanical Properties of ZrON Composite Films Deposited by Plasma Focus Device

Polycrystalline zirconium oxy-nitride (P-ZrON) composite films are deposited on Zr substrates by plasma focus device. The focusing efficiency of plasma focus is maximum at 1.5 mbar nitrogen pressure (NP) due to more intense signal of high voltage probe. The P-ZrON composite films are deposited for 25 focus shots at different NP. The XRD patterns confirm the evolution of ZrN (111), Zr3N4 (230), Zr3N4 (320), Zr3N4 (140), Zr3N4 (340) and ZrO2 (200) diffraction planes. The peak intensity of different diffraction planes and their broadening are associated with increasing NP. The (N + O)/Zr atomic ratio’s are found to be 0.78, 0.88, 1.31, 0.66 and 0.55 at 0.5, 1.0, 1.5, 2.0 and 2.5 mbar NP respectively. The variation in crystallite size of different planes and strain transformation observed in various planes are attributed to varying ion energy fluxes which are associated with the increase of NP. The lattice parameter of ZrN is found to be 0.461 nm at 0.5 mbar NP which is decreased to 0.457 nm at 1.5 mbar NP. The weight fractions of ZrN, Zr3N4 and ZrO2 phases deposited at 2.5, 2 and 1.5 mbar NP are found to 30.5, 28.5 and 41 % respectively. The SEM microstructures reveal that the size and shape of nano-particles and the formation of complicated network of nano-wires (diameter = ~ 55 nm) and nano-combs are associated with increasing NP. The AFM images show the maximum rms surface roughness of P-ZrON composite film when deposited at 1.5 mbar NP. The micro-hardness (8623 ± 0.95 MPa) of P-ZrON composite film deposited at 1.5 mbar NP is found to be four times the micro-hardness of virgin Zr.

Investigation of Effective Parameters on Metal Nitride Deposition by Plasma Focus Device: Number of Shots and Substrate Axial and Angular Positions

Plasma focus (PF) technique is potentially promising candidate for the materials processing and surface modification because of the radiations in a wide range of energies. In this review paper, we discuss and report the use of PF device for transition hard metal nitrides thin film synthesis and investigation of some effective deposition parameters in PF. In this paper, we focus on tungsten nitride film, which has promising industrial and scientific applications. A systematic study has been performed to investigate the effect of the number of focus shots and substrate axial and angular positions on the physical properties of tungsten nitride film deposited by PF device. It is indicated that these parameters are effective in order to obtain good quality tungsten nitride film and estimating the optimum conditions for growing these films with desired physical properties.

Growth and Study of Plasma Assisted Nanostructured Hard Tantalum Nitride Thin Films

Plasma assisted growth of tantalum nitride films in Mather type dense plasma focus device is reported in the current research. Effects of variation in number of plasma focus shots on structural, compositional and mechanical characteristics of synthesized tantalum nitride thin films have been investigated. Better crystallinity with thermally assisted coagulated growth patterns are observed for films synthesized by maximum (fifteen) plasma focus shots. Nano-hardness of films is observed to increase with increasing plasma focus shots whereas the maximum nano-hardness of 16.24 ± 01.54 GPa is observed for film synthesized with fifteen plasma focus shots. Film roughness investigated by atomic force microscopy revealed influence of variation in plasma focus shots on surface roughness which is found to be increased with increase in plasma focus shots.

Deposition of AlN on Nimonic 75 by PFD device

In this study, thin films of aluminium nitride (AlN) are deposited on Nimonic 75 substrates using a 4 kJ Mather type plasma focus device (PFD) for 5, 10 and 15 focus shots. For the deposition of AlN films, a solid aluminium fitted anode was used instead of a copper anode. The PFD was operated with nitrogen gas at a pressure of 2 torr. X-ray diffraction results reveal the formation of a nanocrystalline AlN coating on the surface of the substrate. The crystallite size is dependent on the number of focus shots. The density of grains increased with an increase in the number of focus deposition shots, as illustrated by field emission scanning electron microscopy (FESEM). The FESEM images confirm the distribution of spherical grains for 15 focus shots. Energy dispersive X-ray spectroscopy spectra indicate the presence of expected constituent elements such as N and Al.

Structural and Mechanical Properties of Zirconia Film Deposited by Plasma Focus Device

Nano-crystalline ZrO2/ZrSiO4 composite films are deposited on Si by the irradiation of energetic oxygen ions by plasma focus operation. The XRD patterns confirm the development of different phases (ZrO2 and ZrSiO4) which grow along various orientations and their peak intensities strongly depend on increasing focus shots and sample angular positions. The average crystallite size of the films deposited at 0° angular position is increased with increasing focus shots while it is decreased for the films deposited at 10° angular position. The dislocation density in ZrSiO4 (2 0 4) plane is increased from 3.51 × 10−5 to 8.67 × 10−5 (nm)−2 while it is decreased from 8.85 × 10−5 to 0.011 × 10−5 (nm)−2 in m-ZrO2 (1 2 3) plane when the samples are treated at 0° and 10° angular positions for five focus shots respectively. The FESEM analysis confirms the formation of rounded nano-particles, complicated network of nano-rods, formation of compact, uniform and smooth multi-layers. The EDS analysis confirms the presence of Si, Zr and O in the composite films deposited for different focus shots and sample angular positions. The maximum microhardness of the composite film deposited for 25 focus shots is found to be 10.56 ± 0.51 GPa which definitely will improve the life time of the coated material.

Study of Structural and Mechanical Properties of WN/a-Si3N4 Hard Coatings Grown by Plasma Focus

WN/a-Si3N4 thin films have been synthesized by utilizing the energetic ion/electron species emanated from hot, dense pinched plasma column in UNU/ICTP plasma focus operated with nitrogen gas. Structural, chemical, morphological and mechanical properties of synthesized films are studied using X-ray diffraction (XRD), X-ray photoelectron spectroscopic (XPS), field emission scanning electron microscopy (FESEM) and nano-indentation respectively. XRD spectra show WN2, WN, WSi2 phases on exposed samples. XPS results confirm W–Si–N chemical bonding in synthesized films. FESEM micrographs show uniform granular structure of synthesized WN/a-Si3N4 thin films. Surface morphology of synthesized thin films shows that increase in focus shots strongly affects the grain size due to change in ion energy flux. Nano-indentation results show significant increase in hardness with increase in focus shots with maximum hardness of 23.5 ± 1 GPa is observed for 45 focus shots.

Deposition of magnesium nitride thin films on stainless steel-304 substrates by using a plasma focus device

In this research, for the first time, we synthesize magnesium nitride thin films on 304-type stainless steel substrates using a Mather-type (2 kJ) plasma focus (PF) device. The films of magnesium nitride are coated with different number of focus shots (like 15, 25 and 35) at a distance of 8 cm from the anode tip and at 0° angular position with respect to the anode axis. For investigation of the structural properties and surface morphology of magnesium nitride films, we utilized the X-ray diffractometer (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) analysis, respectively. Also, the elemental composition is characterized by energy-dispersive X-ray (EDX) analysis. Furthermore, Vicker’s microhardness is used to study the mechanical properties of the deposited films. The results show that the degree of crystallinity of deposited thin films (from XRD), the average size of particles and surface roughness (from AFM), crystalline growth of structures (from SEM) and the hardness values of the films depend on the number of focus shots. The EDX analysis demonstrates the existence of the elemental composition of magnesium in the deposited samples.

Investigation on the structural properties and corrosion inhibition of W coatings on stainless steel AISI 304 using PF device

In this paper, thin films of tungsten are coated on 304 type stainless steel substrates using a low energy (1.6kJ) plasma focus device. 35 focus shots are applied each at 6, 8, 10 and 12cm axial distances from the top of the anode and at 0° angular position with respect to anode axis to deposit the W films on SS-304 substrates. X-ray diffraction (XRD) patterns show that the degree of crystallinity of W films strongly depends on axial distances from the anode tip. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) results demonstrate that the sample deposited at 8cm distance has a relatively smooth, uniform and homogeneous surface. Also, energy dispersive X-ray (EDX) analysis reveals the existence of the elemental composition of W in the exposed samples. The corrosion test of samples shows that the highest corrosion resistance belongs to the sample deposited at 8cm distance. Moreover, in order to observe the effect of corrosion on the surface of samples, we have utilized SEM analysis after the corrosion test.

Study on neutron emission from 2.2 kJ plasma focus device

The neutron emission from a low energy (2.2 kJ) plasma focus device operated in deuterium medium has been investigated by employing photo-multiplier tube (PMT) and bubble dosimeter. The neutron emission is found to be pressure dependent and anisotropic in nature. In most cases of plasma focus shots, the PMT signal shows double pulses of neutron emission with different intensities and widths. An interesting relation between intensity of hard X-ray and neutron emission is also observed.

Influence of Different CH4/N2 Ratios on Structural and Mechanical Properties of a-CNx:H Film Synthesized Using Plasma Focus

Carbon nitride films were synthesized by operating the dense plasma focus device with different CH4/N2 admixture gas ratios and fixed 20 focus shots. The pressure and axial distance from anode tip were kept constant at 3 mbar and 8 cm respectively. Raman and X-ray photoelectron spectroscopy (XPS) techniques were used to observe the effect of CH4/N2 ratio on carbon nitride bonding. The XPS analysis showed that the terminating group C≡N is more dominant for the films synthesized using higher concentration of nitrogen which gives softer films. Field emission scanning electron microscopy results showed that the deposited films consist of nanoparticles and their agglomerates. The size of agglomerates increases with decreasing concentration of nitrogen in CH4/N2 admixture gas. Nanoindentation results showed the increase in hardness and elastic modulus values of films with decreasing concentration of nitrogen in CH4/N2 admixture gas. The hardness and elastic modulus values were found to be dependent on sp3 content in the film as well as the C≡N. The hardness and elastic modulus values of 10.7 and 229.8 GPa respectively were achieved for the films deposited with fixed 20 focus deposition shots and using CH4/N2 admixture gas ratio of 7:3.

AFM, XRD and Optical Studies of Silver Nanostructures Fabricated under Extreme Plasma Conditions

This paper reports the deposition of silver on silicon and glass substrates using ions generated in a 3.3 KJ dense plasma focus device. The hot and dense argon plasma formed during the focus phase ionizes the silver disc placed above the top of the anode. Glass and silicon substrates are placed at an axial position of 4.0 cm and 5.0 cm from the top of the anode and are exposed by two focus shots. The deposited materials obtained were characterized using X-ray diffraction, Atomic Force Microscopy (AFM) and UV-vis Spectroscopy. The X-ray diffraction shows the [111] and [200] reflections of silver deposited on silicon substrates whereas on glass only [111] plane is observed. The AFM of silver deposited on silicon substrates shows nanostructures which have triangular like shape. The UV spectra for silver nanostructures placed at 4.0 cm and 5.0 cm on glass substrate shows the absorption peak which originates from the surface plasmon absorption of nanosized silver particles. A red shift of ~13 nm is observed for silver deposited on glass substrate placed at the distance of 5.0 cm from the top of anode.

Synthesis of ZrSiN composite films using a plasma focus device

ZrSiN thin films are synthesized by using plasma focus through various numbers of focus shots (10, 20, and 30), with samples placed at 9 cm away from the tip of the anode. Crystal structures, surface morphologies, and elemental compositions of ZrSiN films are characterized by an X-ray diffractometer (XRD) and scanning electron microscope (SEM) attached with energy dispersive X-ray spectroscopy (EDS). XRD patterns confirm the formations of polycrystalline ZrSiN films. Crystallinity of nitride increases with the increase of focus shot number. The average crystallite size of zirconium nitride increases from 27 ± 3 nm to 73 ± 8 nm and microstrain decreases from 2.28 to 1.0 with the increase of the focus shot number. SEM results exhibit the formations of granular and oval-shaped microstructures, depending on the number of focus shots. EDS results confirm the presences of silicon, zirconium, nitrogen, and oxygen in the composite films. The content values of Zr and N in the composite films increase with the increase of the focus shot number.

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 aluminum 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.

Post-annealing effect on the structural and mechanical properties of multiphase zirconia films deposited by a plasma focus device

Nanostructured multiphase zirconia films (MZFs) are deposited on Zr substrate by the irradiation of energetic oxygen ions emanated from a plasma focus device. The oxygen operating gas pressure of 1 mbar (1 bar = 105 Pa) provides the most appropriate ion energy flux to deposit crystalline ZrO2 films. X-ray diffraction (XRD) patterns reveal the formation of polycrystalline ZrO2 films. The crystallite size (CS), crystal growth, and dislocation densities are attributed to increasing focus shots, sample axial distances, and working gas pressures. Phase and orientation transformations from t-ZrO2 to m-ZrO2 and c-ZrO2 are associated with increasing focus shots and continuous annealing. For lower (200 °C) annealing temperature (AT), full width at half maximum (FWHM) of diffraction peak, CS, and dislocation density (δ) for (020) plane are found to be 0.494, 16.6 nm, and 3.63 × 10−3 nm−2 while for higher (400 °C) AT, these parameters for (111) plane are found to be 0.388, 20.87 nm, and 2.29 × 10−3 nm−2, respectively. Scanning electron microscope (SEM) results demonstrate the formation of rounded grains with uniform distribution. The estimated values of atomic ratio (O/Zr) in ZrO2 films deposited for different axial distances (6 cm, 9 cm, and 12 cm) are found to be 2.1, 2.2, and 2.3, respectively. Fourier transform infrared (FTIR) analysis reveals that the bands appearing at 441 cm−1 and 480 cm−1 belong to m-ZrO2 and t-ZrO2 phases, respectively. Maximum microhardness (8.65±0.45 GPa) of ZrO2 film is ∼ 6.7 times higher than the microhardness of virgin Zr.

Role of Ion Beam Irradiation and Annealing Effect on the Deposition of AlON Nanolayers by Using Plasma Focus Device

AlON nanolayers are synthesized on Al substrate by the irradiation of energetic nitrogen ions using plasma focusing. Samples are exposed to multiple (5, 10, 15, 20 and 25) focus shots. Ion energy and ion number density range from 80 keV to 1.4 MeV and 5.6×1019 m−3 to 1.3×1019 m−3, respectively. Moreover, the effect of continuous annealing (473 K and 523 K) on an AlN surface layer synthesized with 25 focus shots is also examined. The main features of the X-ray diffraction (XRD) patterns with increasing focus shots are: (i) variation in the crystallinity of AlN along (111), (200) and (311) planes, (ii) increasing average crystallite size of AlN (111) plane, and (iii) stress relaxation observed in AlN (111) and (200) planes. The crystallinity of AlN surface layer is comparatively better at 473 K annealing temperature. A broadened diffraction peak related to an aluminium oxide phase showing weak crystallinity is observed for 15 focus shots while non-bounded oxides are present in all other deposited layers. Raman and Fourier transform infrared spectroscopy (FTIR) analysis confirm the presence of AlN and Al2O3 for the surface layer annealed at 473 K temperature. Raman analysis shows that the overlapping of AlN and Al2O3 results in the development of residual stresses. Scanning electron microscope (SEM) results demonstrate that the formation of rounded grains (range from 20 nm to 200 nm) and variations in their microstructures features depend on the increasing number of focus shots. Decomposition of larger clusters into smaller ones is observed.