Influence of ion-bombardment-energy on thin zirconium oxide films prepared by dual frequency oxygen plasma sputtering

Thin ZrO₂ films were prepared using dual frequency oxygen reactive plasma sputtering for wear-resistance coating of ceramics products. Influences of ion-bombardment-energy E_i were investigated for improvement of film characteristics. The results revealed that the deposition rate and the hardness of the prepared ZrO₂ thin films gradually increased with increasing E_i for E_i < 220-250 eV and then decreased, whereas the water-contact-angle on ZrO₂ thin films was about 90 °, having a good water-repellent nature.     

Influence of bias voltage on morphology and structure of MgO thin films prepared by cathodic vacuum arc deposition

MgO thin films with high optical transmittance were prepared by cathodic vacuum arc deposition technique. Rutherford backscattering spectroscopy, atomic force microscopy and X-ray diffraction were used to investigate the influences of the negative pulse bias voltage on the composition, the morphology and the crystal structure of MgO thin films, respectively. AFM images show that the grain growth is influenced by high energy ions under bias voltage and that the grains deposited at the pulse bias voltage with set value of |V_p| = 600 V stack densely and look the largest as compared to those prepared at different set V_p. The RBS spectra indicate that the Mg/O ratio is about 0.95-1.00 in MgO thin films which is nearly the stoichiometric composition of bulk MgO. The Mg/O ratio increases with set |V_p| until |V_p| is 450 V, and then keeps almost unchanged with set |V_p| up to 750 V. The MgO thin films have a combined orientation of (100) and (110). Below − 150 V, the (100) orientation is predominant and the intensity ratio of I₂₂₀/I₂₀₀ increases with set |V_p|.     

Secondary electron suppression in nitrogen plasma ion implantation using a low DC magnetic field

Experiments aiming at the reduction or even total suppression of secondary electrons during the plasma immersion ion implantation were carried out using a plasma device with low DC magnetic field. Comparison of ion implantations in B = 0 and another case with B = 43 G, indicated that the magnetic field was effective to suppress SE flow in the direction transversal to B but only partial suppression was attained in the longitudinal direction. However, these results are already significant since the efficiency of implantation was increased and the flow of SE to the walls became localized to the regions with B crossing the walls.     

Characteristics of copper oxide films deposited by PBII&D

Copper oxide films were deposited by plasma based ion implantation and deposition using a copper antenna as rf sputtering ion source. A gas mixture of Ar + O₂ was used as working gas. During the process, copper that was sputtered from the rf antenna reacted with oxygen and was deposited on a silicon substrate. The composition and the chemical state of the deposited films were analyzed by XPS. The structure of the films was detected by XRD. It is observed that Cu₂O film has been prepared on the Si substrate. It is found that the microstructure of the deposited film is amorphous for the applied voltage of − 5 kV. The surface layer of the deposited films is CuO. This is because the surface layer absorbs the oxygen from ambient air after the treated sample was removed from the vacuum chamber. An appropriate applied voltage, 2 kV under the present conditions, brings the lowest resistance. It is also seen that the maximum absorbance of the deposited films moves to a lower wavelength with increased applied voltage.     

The influence of plasma power on the temperature-dependant conductivity and on the wet chemical etch rate of sputter-deposited alumina thin films

Aluminum oxide (Al₂O₃) thin films are synthesized by reactive d.c. magnetron sputter deposition on silicon substrates. The impact of varying plasma power P_p (i.e. 400 to 1000 W) and of thin film temperatures T up to 540 °C on the electrical performance are evaluated, as these dielectric layers with a thickness of 450 nm are targeted as potential candidates for high temperature sensor applications. From 150 °C to 500 °C, the current-voltage measurements show a leakage current behavior according to the Poole-Frenkel electron emission with an activation energy of 1.16 eV. At T > 500 °C, the conductivity increases above average, in respect to the extrapolated Poole-Frenkel behavior at T < 500 °C, most probably due to the migration of charged ions, such as Ar⁺, incorporated into the film during deposition. Basically, samples synthesized at higher plasma levels show an enhanced electrical insulation behavior. This result is supported by measurements applying optical ellipsometry as well as by the determination of the wet chemical etching behavior in phosphoric-based acid at different bath temperatures. At higher plasma power, the refractive index shows a slight tendency to increase, staying, however, below the value of single-crystalline Al₂O₃. In contrast, the etch rate decreases by a factor of 1.5 at samples deposited at 1000 W when lowering the temperature of the etchant from 90 °C to 60 °C. These results indicate an enhanced film density at higher P_p values as the microstructure of the Al₂O₃ films is X-ray amorphous independent of plasma power and post-deposition annealing temperatures up to 650 °C.     

Fabrication of amorphous silicon films for arrayed waveguide grating application

Amorphous silicon (a-Si) optical films were deposited on a silicon substrate by ICP-PECVD at the temperature of 300 °C, using argon (Ar) and silane (SiH₄) as gas precursors, with the influences of precursors' flow rate, RF power and operating vacuum pressure on the optical properties and microstructure evolutions of a-Si films as the object of our investigation in this study. Optical characteristics of a-Si films indicated that optimum refractive index and extinction coefficient at 1550 nm wavelength can be achieved by using the process parameters of argon/silane flow rate of 400 sccm, RF power wattage of 40 W with an operating vacuum pressure of 60 Pa, respectively. Microstructure evolutions show that the few defects and silicon nano-crystallized structures existing in a-Si films might increase the extinction coefficient. We strongly suggest adopting the optimum process parameters and thermal annealing to fabricate a rib-type a-Si arrayed waveguide grating device with 8 channels and 1.6 nm channel spacing; and its coupling loss and propagation loss were about − 0.74 dB and − 0.14 dB/cm, respectively.     

Effect of deposition temperature on structural, surface, optical and magnetic properties of pulsed laser deposited Al-doped CdO thin films

The objective of this work is to study the influence of deposition temperature on structural, surface, optical and magnetic properties of the Al doped CdO thin films prepared by pulsed laser deposition (PLD) technique. KrF excimer laser (λ = 248 nm, τ_l = 20 ns, ν = 10 Hz, ?_l = 2.5 J/cm²) was employed for the deposition of thin films. It is observed by XRD results that films grown at room temperature and 100 °C show preferential growth along (1 1 1) and (2 0 0) directions while high temperatures (200-400 °C) lead to preferential growth along the (2 0 0) direction only. The optical constants (n, k, α, and optical band gap energy) of films measured by spectroscopic ellipsometry show strong dependence upon deposition temperature. M-H loop of films, measured by vibrating sample magnetometer, deposited at 25 °C and 100 °C show paramagnetic nature while films deposited at temperatures (200-400 °C) exhibit ferromagnetic character. Scanning electron micrographs show degraded elongated grains at lower deposition temperatures, while smooth and compact surface is observed for films deposited at higher deposition temperatures.     

Nitrogen-PBII modification of ultra-high molecular weight polyethylene: Composition, structure and nanomechanical properties

Plasma based ion implantation of nitrogen was performed on mechanically polished UHMWPE model samples by applying 27.13 MHz RF energized low pressure N₂ plasma with 15-30 kV pulses and fluences up to 5 · 10¹⁷ ions/cm². Surface compositional and structural alterations and nanomechanical property changes were investigated by XPS, Raman and by nano-indentation and nano-scratch techniques. The implanted N amounted up to 13-20 at.% (N/C = 0.18-0.30), while a significant amount of oxygen could also be detected on the surface. Three types of chemical states of the incorporated nitrogen were detected, related to linear sp² CN-C and to planar and non-planar sp³ type C-N bonds. The applied PBII treatment led to severe dehydrogenation of the polyethylene resulting in conversion of the surface into a nitrogen-containing DLC type structure. Up to four-fold increase of the hardness at 50-100 nm depth was measured compared to the untreated samples. The scratch volume, characterising the wear resistance, decreased also significantly down to 25-35% of the original value.     

Development and characterization of single wire-arc-plasma sprayed coatings of nickel on carbon blocks and alumina tube substrates

A single wire-arc-plasma spray torch has been used to develop metal coatings on carbon and alumina substrates under argon atmosphere for various applications. Nickel coatings of around 1 mm thickness have been deposited on selected area (60 mm × 200 mm on each side) of large size carbon blocks by intermittent arc spraying and cooling to reduce thermal stresses and possibility of coating de-lamination from the base substrate. The same process is also used for depositing about 3 mm thick nickel metal coatings (8 mm dia. × 40 mm long) on alumina tubes for developing electrical feed throughs. The nickel coated alumina tubes were tested for the vacuum compatibility of the coated material with the base tube. The coated assemblies could withstand vacuum of the order of 1 × 10^− 6 Torr and the leak rate was found to be less than 1 × 10^− 9 Std. cc/s for Helium gas, indicating excellent bonding of the coated metal with alumina ceramics and no connected open porosity in the coatings. X-ray diffraction studies were conducted for identifying the phases and the optical microscope with image analysis technique was used for studying the microstructure and porosity in the coatings.     

Investigation of cytocompatibility of surface-treated cellulose nitrate films by using plasma immersion ion implantation

The alpha-particle sensitive colorless cellulose nitrate films (commercially available as LR 115 films from DOSIRAD, France) have been proposed as cell-culture substrates for alpha-particle radiobiological experiments. Cytocompatibility of the substrate is a key factor to the success of such experiments. The present work aims to investigate the cytocompatibility of surface-treated cellulose nitrate films by using plasma immersion ion implantation-deposition. The films were placed in a vacuum chamber, into which nitrogen gas was continuously bled and where the pressure was kept at 2 × 10^− 3 Torr. Implantation was carried out by igniting the nitrogen plasma at 100 W radio-frequency and applying high bias voltage in pulse with 20 μs pulse width and 50 Hz (with 20 kV or no voltage). HeLa cervix cancer cells were then cultured on both the plasma-treated and untreated cellulose nitrate films. Our tests showed that the plasma-treated films are in general more cytologically compatible.     

Parametric study of nitrided AISI 304 austenite stainless steel prepared by plasma immersion ion implantation

This paper investigates the characteristics of plasma immersion nitrogen-ion implanted AISI 304 austenite stainless steel against such processing parameters as bias voltage (5-20 kV), substrate temperature (300-500 °C), and implantation fluence (1.4 × 10¹⁸-4.2 × 10¹⁸ cm^− 2). Characteristics of the as-implanted specimens under investigation included elemental depth profile, hardness depth profile, crystallographic structure, and corrosion behavior and were determined using glow discharge spectrometry (GDS), the Vickers hardness tester, X-ray diffractometry (XRD), and the potentiodynamic polarization test, respectively. The results show that nitrogen depth profiles strongly depend on these processing parameters and closely relate to the corresponding chromium depth profiles. The hardness depth profiles increase and widen as substrate temperature, bias voltage, and implantation fluence increase. In particular, an improvement in hardness is accompanied by a reduction in corrosion resistance when substrate temperature reaches 500 °C. The corrosion-resistance degrader, CrN, precipitates as substrate temperature exceeds 450 °C, a phenomenon which is clearly evident in the chromium depth profiles as well as the XRD results.     

Mechanical properties of silicon-doped diamond-like carbon films prepared by pulse-plasma chemical vapor deposition

Silicon-doped diamond-like carbon (Si-DLC) films were prepared by dc pulse-plasma chemical vapor deposition (CVD), using a mixture of acetylene (C₂H₂) and tetramethylsilane (TMS) as the material gas. The pulse voltage was varied from − 2 to − 5 kV, and the TMS flow ratio (TMS/(C₂H₂ + TMS)) was varied from 0 to 40%. At a pulse voltage of − 2 kV, an increase in TMS flow ratio leads to a decrease in hardness. In contrast, at a pulse voltage of − 5 kV, an increase in TMS flow ratio leads to a slight increase in hardness. The high hydrogen concentration in the films due to an increase in TMS flow ratio promotes the formation of polymeric sp³ C―H bonds, resulting in the fabrication of soft films at a low pulse voltage of − 2 kV. However, an increase in the effect of ion peening on the growth face results in the formation of hard films at a high pulse voltage of − 5 kV. Then, at a pulse voltage of − 5 kV fabricating hard Si-DLC films, an increase in TMS flow ratio leads to an increase in the silicon content in the films, resulting in a decrease in the friction coefficient. Therefore, it is clarified that Si-DLC films fabricated by dc pulse-plasma CVD under a high pulse voltage and high TMS flow ratio exhibit high hardness and a low friction coefficient. Moreover, to investigate the friction coefficient of Si-DLC films fabricated by dc pulse-plasma CVD, films deposited by dc plasma CVD were also evaluated. To obtain the same low friction coefficient, dc pulse-plasma CVD requires less TMS than dc plasma CVD. Hence, it is also clarified that Si-DLC films can be fabricated at a low cost by dc pulse-plasma CVD.     

The effect of the microstructure and the surface topography on the electrical properties of thin Ag films deposited by high power pulsed magnetron sputtering

In this work thin silver (Ag) films are grown employing high power pulsed magnetron sputtering (HPPMS) for various pulse on/off time configurations, as well as by dc magnetron sputtering (dcMS), for reference. It is shown that the increase of the pulse off-time from 450 μs to 3450 μs, while the pulse on-time is kept constant at 50 μs, results in an increase of the peak target current (I_Tp) from 3 A to 22 A. The increase of I_Tp is accompanied by an increase of the ion flux towards the growing film. This is particularly pronounced for I_Tp > 11 A. The microstructure, the surface topography and the electrical properties of Ag films grown at I_Tp = 11 A, I_Tp = 22 A and by dcMS are investigated, as a function of the film thickness d. It is shown that for d > 20 nm the electrical resistivity of films sputtered at I_Tp = 22 A is similar to that of films grown by dcMS. Slightly higher values are measured for films grown at I_Tp = 11 A. It is found that in this thickness range the film conductivity is strongly affected by the vertical grain size and the scattering of the charged carriers at the film interfaces. For d < 15 nm the resistivity of films deposited at I_Tp = 22 A is substantially lower as compared to that of films grown by dcMS. Films deposited at I_Tp = 11 A exhibit also in this case a higher conductivity. In this thickness regime the electronic transport and, thus the conductivity are profoundly determined by the surface topography and the film density.     

Amorphous-like nanocrystalline γ-Al2O3 films prepared by MOCVD

Alumina (Al₂O₃) films were prepared by metalorganic chemical vapor deposition using aluminum tri-acetylacetonate as a precursor. The effects of deposition conditions on film phase, microstructure, and deposition rate were investigated. γ-Al₂O₃ films were obtained at substrate temperatures ranging between 1173 and 1373 K and total chamber pressures ranging between 400 and 1000 Pa, whereas α-Al₂O₃ films incorporating a small amount of the γ phase were obtained at 1373 K and 800 Pa. Al₂O₃ films prepared at 1173 K showed a halo in X-ray diffraction patterns, consistent with amorphous structures. However, TEM observations suggested that these films consisted of a nanocrystalline γ-Al₂O₃ phase containing trace amounts of carbon.     

Influence of deposition conditions on mechanical and tribological properties of nanostructured TiN/CNx multilayer films

Nanostructured TiN/CN_x multilayer films were deposited onto Si (100) wafers and M42 high-speed-steel substrates using closed-filed unbalanced magnetron sputtering in which the deposition process was controlled by a closed loop optical emission monitor (OEM) to regulate the flow of N₂ gas. Multilayers with different carbon nitride (CN_x) layer thickness could be attained by varying the C target current (0.5 A to 2.0 A) during the deposition. It was found that the different bilayer thickness periods (i.e. the TiN layer thickness Λ_TiN was fixed at 3.0 nm while the CN_x layer thickness Λ_CNx was varied from 0.3 to 1.2 nm) significantly affected the mechanical and tribological properties of TiN/CN_x multilayer films. These multilayer films were characterized and analyzed by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy (AFM), Rockwell-C adhesion test, scratch test, pin-on-disc tribometer, and nanoindentation measurements. XPS analyses revealed that the chemical states, such as TiN, TiC, TiN_xO_y and TiO_2, existed in a TiN layer. Nanoindentation results showed that the hardness was highly dependent on the bilayer thickness. A maximum hardness of ~ 41.0 GPa was observed in a multilayer film at bilayer thickness Λ_TiN = 3.0 nm and Λ_CNx = 0.9 nm. All multilayer films exhibited extreme elasticity with elastic recoveries as high as 80% at 5 mN maximum load. The compressive stresses in the films (in a range of 1.5-3.0 GPa) were strongly related to their microstructure, which depended mainly on the incorporation of nitrogen in the films. By scratch and Rockwell-C adhesion tests, the multilayer films with smaller bilayer thicknesses (Λ_TiN = 3.0 nm, Λ_CNx = 0.3 and 0.6 nm) exhibited the best adhesion and cohesive strength. The critical load value obtained was as high as ~ 78 N for the films with Λ_TiN = 3.0 nm, Λ_CNx = 0.9 nm. The friction coefficient value for a multilayer at Λ_TiN = 3.0 nm and Λ_CNx = 0.9 nm was found to be low 0.11. These adhesive properties and wear performance are also discussed on the basis of microstructure, mechanical properties and tribochemical wear mechanisms.     

Novel application of nanocrystalline nickel electrodeposit: Making good diamond tools easily, efficiently and economically

Electrodeposition has been identified as a feasible and economical technique for nanomaterials application. This article details an improved approach to producing better diamond tools at lower cost and with higher productivity. Pulse-electroformed nanocrystalline nickel was used as the new matrix. The pulse parameters were determined after examination of the microstructure, grain size, hardness and tensile strength of the deposits obtained at different average current densities (J_m) with constant pulse-on time and pulse-off time. It is shown that, with J_m ranging from 1 Adm^− 2 to 14 Adm^− 2, the grain size decreases sharply from 180 nm to about 10 nm while the hardness and tensile strength significantly increase at first and then reach their peaks respectively, although the strength fails to stay long. Current density J_m that produced the highest hardness and strength of deposit (with grain size of 20 nm) was chosen for new diamond tools that exhibited 20.2% longer service life than their usual Ni-Co counterparts. Therefore, nanocrystalline electrodeposits are expected to be an upgrading substitute for conventional polycrystalline matrix.     

Growth, stress and hardness of reactively sputtered tungsten nitride thin films

Tungsten nitride (WN_x) thin films were deposited on Si(100) substrates using direct current reactive magnetron sputtering in discharging a mixture of N₂ and Ar gas. The effects of nitrogen flow rate (F_N2) and substrate bias voltage (V_b) on the composition, phase structure, and mechanical properties for the obtained films were evaluated by means of X-ray photoelectron spectroscopy, X-ray diffraction, high-resolution transmission electron microscopy and nanoindentation. The evolution of phase structure is found closely correlated to N concentration in the films. When V_b = −40 V, with increasing F_N2, the N/W atomic ratio gradually increases in the film, accompanied by a phase transition from cubic β-W to hexagonal WN through face centered-cubic (fcc)-W₂N. At F_N2 = 15 sccm, the N/W atomic ratio gradually decreases with increasing the absolute value of V_b, resulting in a transition from fcc-W₂N to cubic β-W(N) through a mixture of fcc-W₂N + β-W(N). In addition, the increase in implanted nitrogen causes the increase in the compressive stress with increasing F_N2. In contrast, although with increasing the absolute value of V_b from 80 to 160 V the N/W atomic ratio decreases, the increase of the defects caused by increasing ion bombarding energy, dominates the increase of the compressive stress. Furthermore, the maximum hardness value for the films arrives at 38.9 GPa, which is obtained at V_b = −120 V when fcc-W₂N + β-W(N) mixed structure is formed.     

Influence of oxygen partial pressure on electrical and optical properties of Zn0.93Mn0.07O thin films

The Zn_1−xMn_xO (x = 0.07) thin films were grown on glass substrates by direct current reactive magnetron cosputtering. The influence of oxygen partial pressure on the structural, electrical and optical properties of the films has been studied. X-ray-diffraction measurement revealed that all the films were single phase and had wurtzite structure with c-axis orientation. The experimental results indicated that there was an optimum oxygen partial pressure where the film shows relative stronger texture, better nano-crystallite and lower surface roughness. As the oxygen partial pressure increases, the carrier concentration systematically decreases and photoluminescence peaks related to zinc interstitials gradually diminish. The minimal resistivity of 70.48 Ω cm with the highest Hall mobility of 1.36 cm² V⁻¹ s⁻¹ and the carrier density of 6.52 × 10¹⁶ cm⁻³ were obtained when oxygen partial pressure is 0.4. All films exhibit a transmittance higher than 80% in the visible region, while the deposited films showed a lower transmittance when oxygen partial pressure is 0.4. With the increasing of oxygen partial pressure, the peak of near-band-edge emission has firstly a blueshift and then redshift, which shows a similar trend to the band gap in the optical transmittance measurement.     

Dependence of magnetic properties on the film thickness and Pt atomic fraction of post-annealed Fe1−xPtx-C granular films on MgO(1 0 0) and SiO2/Si(1 0 0) substrates

The Fe_1−xPt_x-C granular films with different Pt atomic fractions (0.09 ≤ x ≤ 0.52) and film thicknesses (5 nm ≤ t ≤ 100 nm) were deposited on MgO(1 0 0) and SiO₂/Si(1 0 0) substrates by facing-target sputtering and post-annealing. With the increasing x, the ordered L1₀ FePt grains form. All of the films are ferromagnetic, and the easy axis is in the film plane. With the decrease of t, the films turn from hard ferromagnetic to soft ferromagnetic. The maximum coercivity of the 100-nm thick Fe_1−xPt_x-C granular films measured at a 10-kOe field is 3.7 kOe at x = 0.48. The coercivity of the Fe_0.56Pt_0.44-C granular films increases, and the magnetization measured at a 10-kOe field decreases with the increasing t. The reversal mechanism of the 100-nm thick Fe_1−xPt_x-C granular films turns from the domain wall motion to the Stoner-Wohlfarth rotation mode as x increases. However, the reversal mechanism of the Fe₅₆Pt₄₄-C granular films with different t approaches the Stoner-Wohlfarth rotation mode, and is film-thickness independent.     

Enhanced electrical properties of Pb(Zr0.80Ti0.20)O3 thick films prepared by a modified sol-gel technique

Ferroelectric Pb(Zr_0.80Ti_0.20)O₃ thick films (5.0 μm) were grown on Pt/Ti/SiO₂/Si substrates by a modified sol-gel technique. In this process, PZT nanopowders were prepared via sol-gel, and then these powders were dispersed in a precursor sol to form a slurry. Slurry and PZT precursor solution were spin-coated alternately to form uniform and crack-free thick films. The microstructure and electrical properties of the PZT thick films were investigated. The results in this work show that the PZT thick films possess typical polycrystalline perovskite structures, good pyroelectric coefficient (8.0 × 10^− 8C/cm² K), high remnant polarization (30 μC/cm²), and low coercive field (50 kV/cm).