Synthesis of nanostructured multiphase (Ti,Al)N/a-Si3N4 thin films using dense plasma focus device

A 2.3 kJ pulsed plasma focus device was used to prepare thin films of nc-(Ti,Al)N/a-Si₃N₄ at room temperature. The plasma focus device, fitted with copper anode encapsulated with Ti_0.5Al_0.5 anode, was operated with nitrogen as the filling gas. Films were deposited with various number of focus shots, at 90 mm from top of the anode and at zero angular position with respect to anode axis. XRD patterns show the growth of polycrystalline (Ti,Al)N thin films with orientations in the (1 1 1), (2 0 0), (2 2 0) and (3 1 1) crystallographic planes. Behavior of lattice constant, grain size and film roughness of deposited film as a function of variation in number of focus shots is discussed. SEM micrographs of film deposited with 15 number of focus shots exhibit well-developed net like structure of nc-(Ti,Al)N/a-Si₃N₄ and possibly nc-(Ti,Al)N/a-Si₃N₄/a-AlN or nc-TiN/a-Si₃N₄/a-AlN. Surface Roughness ranging 64 nm to 89 nm was also observed.     

Preparation of Titanium Carbide Thin Film Using Plasma Focus Device

In this work, we report titanium carbide (TiC) formation on the stainless steel—304 substrates by using a low energy (2 kJ) Mather-type plasma focus (PF) device. The argon–acetylene admixture (in 3:1 ratio) was used as the filling gas at a pressure of 1 torr. The thin films were deposited with different number of focus deposition shots (5, 15 and 25 shots), at 0° angular position with respect to the anode axis and at constant distance from the anode tip (10 cm). Deposited thin films have been investigated for their structure by X-Ray diffractometry (XRD) and surface morphology by scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis. The average size of crystallites (from XRD), crystalline growth of structures (from SEM), and size of grains and surface roughness (from AFM) were investigated, which increase by increasing the number of focus deposition shots.     

Growth and surface morphology of ion-beam sputtered Ti-Ni thin films

Titanium-nickel thin films have been deposited on float glass substrates by ion beam sputtering in 100% pure argon atmosphere. Sputtering is predominant at energy region of incident ions, 1000 eV to 100 keV. The as-deposited films were investigated by X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM). In this paper we attempted to study the surface morphology and elemental composition through AFM and XPS, respectively. Core level as well as valence band spectra of ion-beam sputtered Ti-Ni thin films at various Ar gas rates (5, 7 and 12 sccm) show that the thin film deposited at 3 sccm possess two distinct peaks at binding energies 458.55 eV and 464.36 eV mainly due to TiO₂. Upon increasing Ar rate oxidation of Ti-Ni is reduced and the Ti-2p peaks begin approaching those of pure elemental Ti. Here Ti-2p peaks are observed at binding energy positions of 454.7 eV and 460.5 eV. AFM results show that the average grain size and roughness decrease, upon increasing Ar gas rate, from 2.90 μm to 0.096 μm and from 16.285 nm to 1.169 nm, respectively.     

Deposition of tungsten nitride on stainless steel substrates using plasma focus device

Tungsten nitride (WN) films were deposited on the stainless steel-304 substrate by a 2 kJ Mather-type plasma focus device. The preparation method and characterization data are presented. X-ray diffractometer (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed for the characterization of the samples obtained with different number of focus shots, respectively. The average size of crystallites (from XRD), sub-micro-structures (from SEM) and particles (from AFM images) increase when the number of shots increase from 10 to 20 then 30, then they decrease when the substrate is exposed to 40 shots.     

Structural and Morphological Investigations of Deposited Tungsten Nitride Thin Films Using Plasma Focus Device

Tungsten nitride thin films were deposited on the stainless steel-304 substrates by a 2 kJ Mather-type plasma focus device. The preparation method and characterization data are presented. The average size of crystallites, sub-micro structures and size of grains were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) respectively, which increases by increasing the number of focus shots from 10 to 20 then 30 shots.     

Deposition of zirconium carbonitride composite films using ion and electron beams emitted from plasma focus device

Nanocrystalline zirconium carbonitride (ZrCN) composite films were deposited on zirconium substrates for multiple (10, 20, 30, 40 and 50) focus shots. X-ray diffraction analysis shows diffraction peaks corresponding to nitrides (ZrN, Zr₂N and Zr₃N₄), carbide (ZrC) and carbonitride (Zr₂CN), confirming the formation of ZrCN composite films. The average crystallite size estimated for ZrN (2 0 0) and Zr₂CN (1 1 1) planes are found to vary from 10 to 20 nm. Maximum compressive stresses of ∼3.9 GPa in Zr₂N (0 0 2) plane for 30 focus shots and maximum tensile stresses of ∼6.5 GPa in ZrN (2 0 0) plane for 20 focus shots are observed. Tensile stresses observed in Zr₂CN (1 1 1) plane are transformed to compressive stresses for higher (40 and 50) focus shots. Raman analysis reveals the emergence of D and G bands related to carbide phases during the film deposition process. Scanning electron microscope analysis exhibits the nanocrystalline microstructure patterns of the composite films. Microstructure patterns showing agglomerates of 30-300 nm dimensions are also observed. Microhardness values of ZrCN composite films increases with increasing number of focus shots and is equal to 5.6 ± 0.45 GPa for 10 g imposed load, which is 4.5 times that of the virgin one.     

Surface roughness of ion-bombarded Si(1 0 0) surfaces: Roughening and smoothing with the same roughness exponent

We have carried out scanning tunneling microscopy experiments under ultrahigh vacuum condition to study the roughness of pristine as well as ion-bombarded Si(1 0 0) surfaces and of ultrathin Ge films deposited on them. One half of a Si(1 0 0) sample (with native oxide layer) was irradiated at room temperature using 45 keV Si⁻ ions at a fluence of 4 × 10¹⁵ ions/cm² while the other half was masked. STM measurements were then carried out on the unirradiated as well as the irradiated half of the sample. Root-mean-square (rms) roughness of both the halves of the sample has been measured as a function of STM scan size. Below a length scale of ∼30 nm we observe surface smoothing and surface roughening is observed for length scales above this value. However, the surface is self-affine up to length scales of ∼200 nm and the observed roughness exponent of 0.46 ± 0.04 is comparable to earlier cases of ion sputtering studies where only roughening [J. Krim, I. Heyvart, D.V. Haesendonck, Y. Bruynseraede, Phys. Rev. Lett. 70 (1993) 57] or only smoothing [D.K. Goswami, B.N. Dev, Phys. Rev. B 68 (2003) 033401] was observed. Preliminary results involving morphology for Ge deposition on clean ion-irradiated and pristine Si(1 0 0) surfaces are presented.     

Ion beam characterization of rf-sputter deposited AlN films on Si(1 1 1)

Aluminum nitride (AlN) thin films have been deposited on Si(1 1 1) substrates by using reactive-rf-magnetron-sputtering at 250 °C. The crystalline quality and orientation of the films have been studied by X-ray diffraction (XRD). We have observed that the films grow with c- or a-axis orientation. The composition, film thickness, impurities and stress are considered to be factors affecting the orientation and have been analyzed by Rutherford backscattering spectroscopy (RBS), nuclear reaction analysis (NRA) and XRD. Their effects on the film growth will be discussed. Surface morphology of the films will be also presented.     

Effect of swift heavy ion irradiation on spray deposited CdX (X = S, Te) thin films

Cadmium sulfide and cadmium telluride thin films are irradiated with high energy heavy ion beam to study the irradiation induced effects in these films. The polycrystalline thin film samples deposited by spray pyrolysis are irradiated with 60 MeV Oxygen ions using tandem Pelletron accelerator. The X-ray diffraction patterns exhibit a reduction in peak intensities in both CdS and CdTe films. The grain size decrease with fluence is observed for both CdS and CdTe films, with more decrease for CdTe films. The AFM results support this observation. The films show opposite trend in the variation of electrical resistivity with irradiation fluence. A decrease in resistivity is observed for CdS films due to an increase of carrier concentration arising by the creation of sulfur vacancies during the irradiation. The creation of sulfur vacancies is confirmed by XPS studies. The stoichiometric changes seen from XPS studies support this observation. An enhancement of grain boundary scattering due to the reduction of grain size leads to the increase of electrical resistivity for CdTe films.     

The Effect of Substrate Temperature on the Structure and Morphology of Titanium Nitride Compounds Grown by DC Magnetron Sputtering

The TiN thin films were deposited on p-type silicon (100) substrates using reactive planar DC magnetron sputtering system. The target was 99.99% pure Ti. The reactive sputter gas was a mixture of Ar (99.999%) and N₂ (99.999%) with the ratio Ar (97%) and N₂ (3%) by volume. Structural characterization of the coating was done using X-ray diffraction (XRD). The surface roughness of the coating was determined using an Atomic Force Microscope (AFM). The reflectivity of thin films was investigated by a spectrophotometer system. The X-ray diffraction measurements showed that by increasing the substrate temperature during the growth, change in crystalline structure will occur. The crystallite size of the films determined by Scherrer’s equation, and the crystallite size measured by AFM also increased by increasing the substrate growth temperature. The surface reflectivity measurements indicate that by increasing the substrate growth temperature, the optical properties of the films changes. The change in optical properties and crystalline structure of the films indicate that substrate growth temperature plays an important role in structure and morphology of the grown layers.     

Using Mather-Type Plasma Focus Device for Fabrication of Tungsten Thin Films

Tungsten (W) thin films were deposited on stainless steel–304 substrates using a low energy (2?kJ) plasma focus device. The samples were synthesized at various distances with respect to anode tip (7, 10 and 13?cm) and using same number of focus deposition shots (25 shots). X-ray diffraction (XRD), energy dispersive X-ray atomic force microscopy (AFM) and micro hardness were used to investigate the prepared samples. XRD analysis revealed that the degree of crystallinity of deposited thin films decrease with increasing the distance from the anode tip. AFM results showed that size of the grains on the surface of the films and the surface roughness of deposited samples constantly increase with the increasing of the axial position. Moreover, the hardness measurements revealed that the highest mechanical hardness is obtained when the film is deposited at 7?cm axial position.     

Deposition of Chromium Thin Films on Stainless Steel-304 Substrates Using a Low Energy Plasma Focus Device

In this paper, we study thin films of chromium deposited on stainless steel-304 substrates using a low energy (1.6 kJ) plasma focus device. The films of chromium are likewise deposited with 25 focus shots each at various axial distances from the top of the anode (3, 5, 7, 9 and 11 cm). We also consider different angular positions with respect to the anode axis (0°, 15° and 30°) at a distance of 5 cm from the anode tip to deposit the chromium films on the stainless steel substrates. To characterize the structural properties of the films, we benefit from X-ray diffraction (XRD) analysis. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) are applied as well to study the surface morphology of these deposited films. Furthermore, we make use of Vicker’s micro-hardness measurements to investigate the mechanical properties of chromium thin films. The XRD results show that the degree of crystallinity of chromium thin films depends on the substrate axial and angular positions. The AFM images illustrate that the film deposited at the distance of 5 cm and the angular position of 0° has quite a uniform surface with homogeneous distribution of grains on the film surface. From the hardness results, we observe that the sample deposited at the axial distance of 5 cm from the anode tip and at the angle of 0° with respect to the anode axis, is harder than the other deposited films.     

Deposition of Alumina Films on Si (1 0 0) Substrate Using a Low Energy Dense Plasma Focus Device

A 1.5 kJ pulsed low energy Mather type plasma focus (PF) is used to deposit thin films of alumina (α-Al₂O₃) on Si (1 0 0) substrates. The PF device with its anode made of aluminum was operated with argon-oxygen mixture as the filling gas. The Al₂O₃ thin film samples were prepared using 10, 20 and 30 successive shots with substrates placed at 60 mm from the top of the anode at approximately zero angular position with respect to the anode axis. The crystallography of the as-deposited and annealed samples was studied by X-ray diffractometry (XRD). Raman Spectroscopy studies verified the formation of α-Al₂O₃ phase in the annealed films. Scanning electron micrographs (SEM) of the annealed films present many different sized particulates (50–300 nm) distributed upon the film surface. The cross-sectional SEM micrographs show that the thickness of deposited alumina film is linear with a typical rate of 45 nm/shot at focus storage energy of 850 J.     

Computer simulation of sputtering at the low index (1 0 0), (1 1 0) and (1 1 1) surfaces of Ni3Al in a STEM

The present study is relevant to the preferential Al sputtering and/or enhancement of the Ni/Al ratio in Ni₃Al observed by the scanning transmission electron microscopy fitted with a field emission gun (FEG STEM). Atomic recoil events at the low index (1 0 0), (1 1 0) and (1 1 1) surfaces of Ni₃Al through elastic collisions between electrons and atoms are simulated using molecular dynamics (MD) methods. The threshold energy for sputtering, E_sp, and adatom creation, E_ad, are determined as a function of recoil direction. Based on the MD determined E_sp, the sputtering cross-sections for Ni and Al atoms in these surfaces are calculated with the previous proposed model. It is found that the sputtering cross-section for Al atoms is about 7-8 times higher than that for Ni, indicating the preferential sputtering of Al in Ni₃Al, in good agreement with experiments. It is also found that the sputtering cross-sections for Ni atoms are almost the same in these three surfaces, suggesting that they are independent of surface orientation. Thus, the sputtering process is almost independent of the surface orientation in Ni₃Al, as it is controlled by the sputtering of Ni atoms with a lower sputtering rate.     

Studies on the high electronic energy deposition in polyaniline thin films

We report here the physico-chemical changes brought about by high electronic energy deposition of gold ions in HCl doped polyaniline (PANI) thin films. PANI thin films were synthesized by in situ polymerization technique. The as-synthesized PANI thin films of thickness 160 nm were irradiated using Au⁷⁺ ion of 100 MeV energy at different fluences, namely, 5 × 10¹¹ ions/cm² and 5 × 10¹² ions/cm², respectively. A significant change was seen after irradiation in electrical and photo conductivity, which may be related to increased carrier concentration, and structural modifications in the polymer film. In addition, the high electronic energy deposition showed other effects like cross-linking of polymer chains, bond breaking and creation of defect sites. AFM observations revealed mountainous type features in all (before and after irradiation) PANI samples. The average size (diameter) and density of such mountainous clusters were found to be related with the ion fluence. The AFM profiles also showed change in the surface roughness of the films with respect to irradiation, which is one of the peculiarity of the high electronic energy deposition technique.     

Structural distortion effect in the cobalt ions implanted TiO2 films

TiO₂ thin films were prepared by direct current magnetron sputtering on glass substrates, then were implanted by cobalt ions, and finally annealed at 400 and 500 °C for 50 min, respectively. They were identified as an anatase structure by X-ray diffraction (XRD). Scanning electron microscope (SEM) images showed that the grain sizes of the films grow with increasing annealing temperature. The energy dispersive X-ray (EDX) measurements indicated that the ratio of the cobalt atoms number and total atoms number of cobalt and titanium in the Co-TiO₂ films was about 2.51%, and X-ray photoelectron spectroscopy (XPS) results revealed that the cobalt existed in the films as Co²⁺. The element distribution of cobalt along cross-section of the films was studied by EDX, as the results showed that the cobalt diffused deeply into the films after annealing. The high resolution transmission electron microscopy (HRTEM) images were used to affirm the anatase structure of the Co-TiO₂ films, and edge dislocations were further found in the HRTEM images, which could be attributed to the effect of the implantation.     

Enhanced susceptibility of CaF2(1 1 1) to adsorption due to ion irradiation

We have investigated morphological changes of freshly cleaved CaF₂(1 1 1) single crystal surfaces before and after ion irradiation. We show that with or without irradiation the surface undergoes serious changes within minutes after the cleavage if the samples are exposed to ambient conditions. This is most likely due to the adsorption of water and could be avoided only if working under clean ultra-high-vacuum conditions. Ion-induced modifications on this surface seem to act as centers for an increased rate of adsorption so that any quantitative numbers obtained by atomic force microscopy in such experiments have to be treated with caution.     

Middle-frequency magnetron sputtering for GaN growth

A middle-frequency magnetron sputtering system was designed and constructed for GaN growth, in which a pair of back cooled pool-shaped twin magnetrons were used for Ga metal targets. GaN films were prepared using this system under various gas pressure (0.5-3.0 Pa) in a mixture of N₂ and Ar with N₂/Ar ratio of 6:1. X-ray diffraction showed that the GaN films had a strong (0 0 0 2) orientation, and the film deposited at 1.5 Pa had two more weak peaks attributed to and . The full width at half maximum (FWHM) of the (0 0 0 2) peak for the GaN film deposited at 1.5 Pa and 0.5 Pa is ∼721 and ∼986 arcsec, respectively. The deposition rate was in the range of 43.5-87.8 nm/min and was mainly influenced by the deposition pressure. The films deposited at higher pressures are columnar in structure. A root-mean-square roughness of 4.4 nm was obtained from the atomic force microscopy (AFM) surface morphology of the film deposited at 0.5 Pa.     

Synthesis of nanodimensional TiO2 thin films using energetic ion beam

Nanophases of TiO₂ are achieved by irradiating polycrystalline thin films of TiO₂ by 100 MeV Au ion beam at varying fluence. The surface morphology of pristine and irradiated films is studied by atomic force microscopy (AFM). Phase of the film before and after irradiation is identified by glancing angle X-ray diffraction (GAXRD). The blue shift observed in UV-vis absorption edge of the irradiated films indicates nanostructure formation. Electron spin resonance (ESR) studies are carried out to identify defects created by the irradiation. The nanocrystallisation induced by SHI irradiation in polycrystalline thin films is studied.     

Surface morphology influence on deuterium retention in beryllium films prepared by thermionic vacuum arc method

In a plasma-confinement device, material eroded from plasma facing components will be transported and re-deposited at other locations inside the reaction chamber. Since beryllium from the first wall of the ITER fusion reactor will be eroded, ionized in the scrape-off layer plasma and finally re-deposited on divertor surfaces flowing along the magnetic field, it is important to study the properties of divertor armour materials (C, W) coated with beryllium.By applying different bias voltages (−200 V to +700 V) to the substrates during deposition, the morphology of the obtained films was modified. The films’ morphology was characterized by means of AFM and SEM, and it was found that the coatings prepared using negative bias voltage at the substrate during deposition are more compact and have a smoother surface compared to the samples prepared with positive bias voltage. The thickness and composition of each film were measured using Rutherford backscattering spectrometry (RBS). A study of deuterium implantation and retention into the prepared films was performed at IPP Garching in the high current ion source.