Ion Beam Sputtering Method Research Articles

Correlation between morphology and transport properties of Au/Co/Au/Si wedge ultra-thin film

We report the thermoelectric power (TEP) and electrical resistivity characterization supported by structural and surface morphological properties on a wedge shaped ultra-thin sample of Au/Co/Au/Si (100) with Co have varying thickness from 0.5 nm to 4 nm across the sample. The sample was prepared by Ion Beam Sputtering method, with an ultrathin layer of Co sandwiched between two layers of Au (3 nm thicknesses each). The observed TEP results showed that the system is semiconductor in nature and the concentration of the charge carrier is inversely proportional to the Seebeck coefficient (S) and also concentration of charge carrier modifies with the film thickness leading to a change in thermo power, which is found to be higher at lower thicknesses of Co sandwiched layer. The type of charge carrier was also determined to be electrons in this system. The observed results are in good agreement with the resistivity measurement carried out as a function of film thickness indicating a decrease in resistivity as a function of film thickness due to enhancement in charge carrier mobility. The thermal activation energy was seen to increase from ∼29.5 meV to ∼280.3 meV as the film thickness increased from the minimum to the highest. Corresponding Atomic Force Microscopy (AFM) measurement revealed island type grain growth with the introduction of a significant amount of roughness, while Magnetic Force Microscopy (MFM) experiments exhibit randomly oriented magnetic domain structures. The overall results suggest that lowest thickness film shows semiconducting nature, while variable range hopping phenomena due to some localized energy levels near the valence and conduction band is observed in the highest thickness film. This result is also well supported by XRD measurement, which revealed crystalline nature of the films. Such low cost, easy to fabricate materials may find applications in Peltier cooling or energy harvesting applications without the harmful carbon dioxide emission. For this, advance experiments will be done in future.

Study of surface morphology of Ag thin films prepared by sputtering and irradiation with keV Ar ion beam

In this paper, the possibility of preparing silver nanostructures with a high area density of nanoparticles of various shapes by the ion beam sputtering (IBS) method, using a glancing angle deposition (GLAD) configuration, and subsequent irradiation with heavy ions, was tested. In the experiment, keV Ar+ ions were used for both IBS and bombardment. The prepared nanostructures were analyzed by RBS and microscopic methods of SEM and AFM. It turned out that IBS/GLAD makes it possible to create silver nanostructures (networks of individual silver nanoparticles), but only with relatively low areal densities (∼ 70 µm2). The bombardment led to changes in the porosity only after high ion fluences, but also to disruption of the nanostructures. Even so, the IBS method with GLAD configuration has been shown to be a promising way to prepare high-porosity nanostructures. Nevertheless, further experimental efforts will be needed to find the optimal technology.

Microstructure, mechanical properties and thermal stability of Cr/WC nano-multilayered coating synthesized by ion beam sputtering

Cr/WC nano-multilayered coatings with fixed period ratio (Cr:WC=1:2) were synthesized by using ion beam sputtering method. The microstructure, mechanical properties and the thermal stability of coatings were investigated by X-ray diffraction, Scanning Electron Microscopy, Transmission Electron Microscopy and nanoindentation. Well-defined laminar amorphous microstructure and uniform monolayers, which consists of amorphous WC1-x and Cr, can be found in the as-deposited nano-multilayered coatings with series modulation period. Although the hardness of Cr/WC nano-multilayered coating increases with the increasing of modulation period, it is still lower than the value predicted by Hill model. Almost all the toughness of Cr/WC nano-multilayered coatings are lower than that of monolayer Cr coating, however, they are higher than that of monolayer WC coating, indicating that the addition of Cr and nano-multilayered architecture can improve the toughness of monolayer WC coating. Both microstructure and mechanical properties of Cr/WC nano-multilayered coatings were stable when the vacuum heat treatment temperature was lower than 400 °C. As the heat treatment temperature was 600 °C, some nanocrystalline W2C, W and WC1-x were enclosed in the amorphous WC sublayer which is beneficial to its hardness enhancement while it is harmful to its toughness. As the heat treatment temperature was 800 °C, the nano-multilayered structure was destroyed completely and its mechanical properties were seriously degraded.

Tandem GCIB-ToF-SIMS and GCIB-XPS analyses of the 2-mercaptobenzothiazole on brass

Surface analysis of 2-mercaptobenzothiazole (MBTH) adsorbed on brass from 3 wt.% NaCl solution was performed by means of X-ray photoelectron spectroscopy and tandem (MS/MS) time-of-flight secondary ion mass spectrometry (ToF-SIMS). These surface analytical techniques were used in association with the gas cluster ion beam (GCIB) sputtering method at various acceleration energies and cluster sizes, which slowly removes the surface layer and leaves the chemical information intact during the sputtering of the very thin surface layer. In addition, MS1 ToF-SIMS was used for 2D and 3D imaging to show the molecular and elemental distribution of the surface species. Using the tandem ToF-SIMS capability, the MS2 spectra clearly confirmed the presence of MBTH on the surface. Moreover, organometallic complexes were indicated, which formed between the MBTH and Cu ions released due to the corrosion of the brass. These analyses were performed based on the fragmentation products identified in the MS2 spectra.

Effect of annealing treatment on response characteristics of Pd-Ni alloy based hydrogen sensor

The response rate and anti-interference performance are crucial to the detect performance for Pd-based hydrogen sensors. In this study, a resistance- type palladium-nickel (Pd90Ni10) thin film hydrogen sensors were prepared by the ion beam sputtering method. Sensors with an optimized Pd90Ni10 thickness (90 nm) which showed the fastest response for hydrogen were selected to study the effect of annealing treatment to the response rate and anti-interference performance. Four groups of samples were annealed at 250°C, 300°C, 350°C, and 400°C in air atmosphere for 4 hours, respectively. The impact of annealing treatment on base resistance stability and hydrogen response characteristics were studied. SEM, EDS and XRD analysis were carried out to reveal the relationship between response characteristics and microstructures. Results show that annealing treatment was beneficial to the base resistance stability and response rate. Samples annealed at 350°C showed the best base resistance stability and response rate. Furthermore, the difference of response rate ∆ was improved for the annealing treatment, indicating the improvement of the hydrogen sensor regarding the anti-interference effect to other gases. Meanwhile, a new mechanism including mutli-factors of Pd-Ni alloy about the anti-interference of oxygen was proposed based on our study. Besides, the sensors with the optimized fabrication process were tested in mixed standard gas with various hydrogen concentrations. This work provides an outstanding guidance to fabricate of hydrogen sensors of high response rate and anti-interference performance.

Optical AR Coatings of the Mid-IR Band for ZnGeP2 Single Crystals Based on ZnS and Oxide Aluminum

In this work, the parameters of antireflection interference coatings based on alternating layers of ZnS/Al2O3 on the laser-induced damage threshold (LIDT) of ZGP crystals under the action of Ho:YAG laser radiation at a wavelength of 2.097 μm were determined. The coating deposition was carried out using the ion-beam sputtering method. The LIDT of the sample with a coating based on alternating layers ZnS and Al2O3 was equal to WoE = 3.45 J/cm2, and the LIDT of the uncoated sample was equal to WoE = 2.23 J/cm2. An increase in the optical breakdown threshold by ~55% was observed after the deposition of an AR coating based on ZnS and Al2O3 materials. An assumption was made about the absence of local fluctuations in the composition and mechanical stresses in the case of the coated sample, namely that this leads to good adhesion of the multilayer coating to the polished surface of the crystal, and as a result to an increase in the optical breakdown threshold as compared to the uncoated sample due to closure of the dangling chemical bonds and bulk defects emerging on the polished surface.

Structural, vibrational and photodegradation properties of CuAl2O4 films

Cu–Al–O thin films were grown on Si (111) substrates by using the reactive ion-beam sputtering (RIBS) method within the temperature range 80 to 380 °C. The effect of thermal annealing of Cu–Al–O films under various regimes of cooling on the microstructure, morphology, optical properties and photocatalytic activity were examined. The properties of annealed Cu–Al–O films were studied using atomic force microscope (AFM), energy dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectrometry (FTIR). The X-ray diffraction patterns show appearance only CuAl2O4 phase after thermal annealing of Cu–Al–O thin films at 900 °C. Raman scattering confocal measurements have also confirmed the presence of CuO phases in annealed Cu–Al–O samples. AFM results have indicated that the greatest RMS roughness is observed in CuAl2O4 films after temperature annealing under the fast cooling regime. Photodegradation of CuAl2O4 films was investigated using methyl orange as model pollutant. Present results indicate that CuAl2O4 photocatalysts are potential candidate for the practical application in photocatalytic degradation of organic compounds.

A 4×4 metal-semiconductor-metal rectangular deep-ultraviolet detector array of Ga2O3 photoconductor with high photo response

A 4×4 beta-phase gallium oxide (β-Ga2O3) deep-ultraviolet (DUV) rectangular 10-fingers interdigital metal-semiconductor-metal (MSM) photodetector array of high photo responsivity is introduced. The Ga2O3 thin film is prepared through the metalorganic chemical vapor deposition technique, then used to construct the photodetector array via photolithography, lift-off, and ion beam sputtering methods. The one photodetector cell shows dark current of 1.94 pA, photo-to-dark current ratio of 6×107, photo responsivity of 634.15 A⋅W−1, specific detectivity of 5.93×1011 cm⋅Hz1/2⋅W−1 (Jones), external quantum efficiency of 310000%, and linear dynamic region of 108.94 dB, indicating high performances for DUV photo detection. Furthermore, the 16-cell photodetector array displays uniform performances with decent deviation of 19.6% for photo responsivity.

Influence of the Characteristics of Multilayer Interference Antireflection Coatings Based on Nb, Si, and Al Oxides on the Laser-Induced Damage Threshold of ZnGeP2 Single Crystal

In this work, the effect of the defect structure and the parameters of antireflection interference coatings based on alternating layers of Nb2O5/Al2O3 and Nb2O5/SiO2 layers on the laser-induced damage threshold of ZGP crystals under the action of Ho:YAG laser radiation at a wavelength of 2.097 μm was determined. Coating deposition was carried out using the ion-beam sputtering method. The laser-induced damage threshold of the sample with a coating based on alternating layers Nb2O5 and SiO2 was W0d = 1.8 J/cm2. The laser-induced damage threshold of the coated sample based on alternating layers of Nb2O5 and Al2O3 was W0d = 2.35 J/cm2. It has been found that the presence of silicon conglomerates in an interference antireflection coating leads to a decrease in the laser-induced damage threshold of a nonlinear crystal due to local mechanical stresses and the scattering of incident laser radiation.

Investigation of UV, ns-laser damage resistance of hafnia films produced by electron beam evaporation and ion beam sputtering deposition methods

Laser-induced damage in coating materials with a high index of refraction, such as hafnia, limits the performance of high power and high energy laser systems. Understanding the underlying physics responsible for laser damage holds the key for developing damage-resistant optical films. Previous studies have reported a substantial difference in laser damage onset for hafnia films produced by different deposition methods, yet the underlying mechanisms for the observed difference remain elusive. We combined laser damage testing with analytical characterizations and theoretical simulations to investigate the response of hafnia films produced by electron (e-) beam evaporation vs ion beam sputtering (IBS) methods upon UV ns-laser exposure. We found that e-beam produced hafnia films were overall more damage resistant; in addition, we observed a polarization anisotropy associated with the onset of damage in the e-beam films, while this effect was absent in the latter films. The observed differences can be attributed to the stark contrast in the pressure inside the pores inherent in both films. The high pressure inside the IBS-induced nanobubbles has been shown to reduce the threshold for laser-induced plasma breakdown leading to film damage. The polarization effects in the e-beam coatings can be related to the asymmetric electric field intensification induced by the columnar void structure. Our findings provide a fundamental basis for developing strategies to produce laser damage-resistant coatings for UV pulsed laser applications.

Influence of the autoirradiation on nanosized gold layers formation by the ion-beam deposition

2–13 nm gold films were obtained by the method of ion-beam sputtering on silicon and quartz substrates. It is shown that the use of an additional operation of deposition followed by the sputtering of a gold layer of 2–3 nm thickness makes it possible to reduce the electrical resistance and surface roughness of the metal films, in comparison with similar films obtained without its use. The results of measuring the temperature coefficient of resistance of nanosized gold films on silicon substrates allowed us to conclude that the films deposited become continuous at a thickness of 6-8 nm. The results of optical measurements of 10 nm gold films, obtained on quartz substrates, showed that the reflection coefficient of electromagnetic radiation at a wavelength of 850 nm is 2.8 % higher than the corresponding coefficient for the same films obtained without using this operation, and is 83 %. An important role in the formation of nanoscale gold layers is played by the processes of self-irradiation of the growing layer of the high-energy component of the gold atoms flux. When using an additional operation of deposition/sputtering, high-energy gold atoms are implanted into the substrate to a depth of about 2 nm. On the one hand, these atoms are point defects in the surface damaged layer of the substrate; on the other hand, they serve as additional centers of cluster formation. This ensures strong adhesion of the metal layer to the substrate and, therefore, the gold films become continuous and more homogeneous in microstructure. The method of ion-beam deposition can be successfully applied to obtain high-quality conductive optically transparent nanosized gold films.

Reducible oxide and allotropic transition induced by hydrogen annealing: synthesis routes of TiO2 thin films to tailor optical response

Optical properties of hydrogenated TiO2 thin films deposited by the ion beam sputtering method are reported. By reducing the oxide by hydrogenation in situ (during deposition) and ex situ (by means of posterior thermal annealing) a controlled phase modification allows to manipulate optical properties to improve photoactivity for solar energy conversion and catalytic applications. The hydrogenation procedure prompts remarkable structural changes and optical properties of the TiO2 hierarchical thin films. Photoemission electron spectroscopy (XPS) results show the presence of titanium in Ti4+ into Ti3+ state of oxidation, i.e., compatible with oxygen vacancies and titanium interstitials. Vibrational properties inspected by IR absorption and Raman spectroscopy allowed identifying potentially catalytic sites and vibration modes associated with hydrogen. The vibrational spectra show that both in situ and ex situ hydrogenation routes contribute to prompt (dis)order in the films, involving the presence of anatase crystalline phase embedded in an amorphous matrix or mixed-phase (anatase + rutile) crystalline TiO2. To avoid debate about the TiO2 theoretical (indirect) and expected and measured (direct, normally reported) optical gap (Egap), the absorption coefficient spectra were analyzed by a recently developed method based on the Boltzmann sigmoidal function. From these analyses, conclusions about defects states prompted by the hydrogenation processes are presented.

Fano-like resonances in nanostructured thin films for spatial filtering

Fano-like resonant coupling of electromagnetic radiation with planar waveguiding modes of nanostructured thin films is proposed and realized experimentally. Different from conventional Fano coupling to compact resonators with the discrete spectrum, we report Fano-like coupling to infinitely extended planar waveguiding modes of the spatially unbound system. We fabricated the films by the ion beam sputtering method on nano-modulated substrates. The observed Fano-like process shows extremely strong sensitivity with respect to the wavelength and especially to the incidence angle of the radiation and can potentially be used for frequency and spatial filtering of light in transmission/reflection through/from such nanostructured thin films.

Structural Features of Textured Zinc-Oxide Films Obtained by the Ion-Beam Sputtering Method

Textured ZnO films obtained on amorphous substrates using the ion-beam sputtering method are studied. X-ray diffraction and atomic-force microscopy methods show that the resulting films have a polycrystalline structure immediately after deposition. It is established that further annealing of the samples in the temperature range from 200°C to 500°C results in recrystallization, which leads to changes in the grain size and surface roughness. A dependence of the crystallization intensity on the deposition conditions is found, which is related to the number of defects in the unannealed films. In films with an initially more perfect structure, heat treatment at 500°C results in the growth of grains by more than 2 times and a decrease in the roughness by ∼40%.

Improvement of the lubrication properties of grease with Mn3O4/graphene (Mn3O4#G) nanocomposite additive

Although grease can effectively lubricate machines, lubrication failure may occur under high speed and heavy load conditions. In this study, Mn3O4/graphene nanocomposites (Mn3O4#G) were synthetized using a hydrothermal method as lubricant additives. The lubrication properties of compound grease with Mn3O4#G nanocomposite additive under heavy contact loads of 600–900 N (3.95–4.59 GPa) were investigated. First, the nanocomposites were dispersed into L-XBCEA 0 lithium grease via successive electromagnetic stirring, ultrasound vibration, and three-roll milling. Compound grease with additives of commercial graphene (Com#G) was also investigated for comparison. Tribological test results revealed that the trace amounts of Mn3O4#G (as low as 0.02 wt%) could reduce the coefficient of friction (COF) of grease significantly. When the concentration of Mn3O4#G was 0.1 wt%, the COF and wear depth were 43.5% and 86.1%, lower than those of pure graphene, respectively. In addition, under the effect of friction, the microstructure of graphene in Mn3O4#G nanocomposites tends to be ordered and normalized. Furthermore, most of the Mn3O4 transformed into Mn2O3 owing to the high temperature generated from friction. Using the Ar gas cluster ion beam sputtering method, the thickness of the tribofilm was estimated to be 25–34 nm. Finally, the improvement of the lubrication properties was attributed to the synergistic effect of the adsorbed tribofilm, i.e., the graphene island effect and the filling effect of Mn3O4#G.

Gamma-ray irradiation effects on tantalum thin film for improved mechanical compatibility and cytocompatibility.

In this work, tantalum thin films were prepared on titanium substrates by an ion beam sputtering method. Tantalum thin films were irradiated by gamma-ray with different total dose levels. The effect of irradiation on the phase composition, microstructure, surface morphology, and chemical resistance were analyzed. Besides, in vitro cytocompatibility of tantalum films treated with different radiation doses were evaluated via 3T3-E1 cells. Experimental results showed that higher radiation dose resulted in reductions in crystalline nature, denser morphology, lower elastic modulus, less oxygen vacancies and better corrosion resistance. Additionally, 3T3-E1 cells adhered and spread well on the surface of tantalum film with irradiation exposure to 10kGy. The dense surface morphology, less density of chemical defects and amorphous phase produced by the gamma-ray irradiation played a major role in the improvement of mechanical compatibility, electrochemical stability property along with the cytocompatibility of the tantalum films.

Ion sputtering for preparation of thin MAX and MXene phases

Thin films of MAX and MXene phases were prepared by ion beam sputtering followed by thermal annealing in vacuum. For this purpose, a Low Energy Ion Facility (LEIF) using heavy ions for target irradiation was developed, and the DC ion beam sputtering method was implemented. The process for preparing MAX and MXene thin composites consists of two steps. First step: bombarding the elemental targets with low-energy ions (either all targets together, each with the corresponding size, or each target separately and repeatedly); it results in synthesis of either homogeneous layers of mixed phases or multilayer arrays of individual phases. Second step: thermal annealing under vacuum with a suitable temperature and time to induce a diffusion process, mutual phase interaction and finally the formation of MAX or MXene composites with the desired structure. After installation of the LEIF system and the introduction of the two-step method, i.e. DC ion sputtering with subsequent thermal processing, the first Ti-based MAX and MXene carbides, Ti2SnC and Ti2C, in thin films of composites were prepared and analyzed.

Свойства мемристивных структур на основе нанокомпозита (Co-=SUB=-40-=/SUB=-Fe-=SUB=-40-=/SUB=-B-=SUB=-20-=/SUB=-)-=SUB=-x-=/SUB=-(LiNbO-=SUB=-3-=/SUB=-)-=SUB=-100-x-=/SUB=-, синтезированных на SiO-=SUB=-2-=/SUB=-/Si-подложках

The structural features and I-V curves of a metal/nanocomposite/metal (M/NC/M) sandwiches based on NC (Co40Fe40B20)x(LiNbO3)100-x synthesized on SiO2/Si substrates are investigated. Samples M/NC/M were obtained by the method of ion beam sputtering of a composite target which allows to form NC of different composition in the range x = 5–48 at. %. Electron microscopic analysis showed that the matrix consists of metal granules in an amorphous nonstoichiometric matrix. The granules have a size of d~2–3 nm and have a shape close to spherical with a slight elongation along the growth direction. The local chemical composition of NC films was studied by X-ray photoelectron spectroscopy. The structures demonstrate the effect of resistive switching with the maximum value Roff / Ron≈10, observed at the metal content is x ~ 13 at. %. The number of write/erase cycles was more than 10^4. Observed effect of resistive switching is explain by the oxygen vacancies action on the tunnel conductivity of the contacts of granules percolation chains with one of structure electrode separated from the NC by a strongly oxidized layer.

The impact of nano-bubbles on the laser performance of hafnia films deposited by oxygen assisted ion beam sputtering method

Hafnia is a high refractive index material used in the manufacturing of dielectric coatings for next generation lasers. The formation of defects during deposition is the major barrier to realizing high laser-damage resistant coatings for future high energy density laser applications. Understanding the precursors responsible for laser-induced damage in hafnia is therefore critical. In this work, we investigate the mechanism of laser-induced damage in 90-nm thick hafnia films produced by an oxygen assisted dual ion beam sputtering (IBS) process. Under pulsed, nanosecond ultraviolet laser exposure (355 nm, 8 ns), the laser-induced damage onset is found to be strongly dependent on the amount of argon and excessive oxygen entrapped in the nanobubbles within the hafnia films. The presence of nanobubbles is revealed and confirmed by small angle X-ray scattering and scanning/transmission electron microscopy coupled with high-angle annular dark-field. The damage onset is stable initially but decreases as the energy of oxygen goes beyond 100 eV. The damage initiation is ascribed to a laser-induced plasma generation within the nanobubbles through multiphoton ionization. The results reveal that nanobubbles formed in the IBS produced coatings are a potent precursor. Although nanobubbles are commonly present in IBS films, their negative impact on laser damage resistance of hafnia films has not been previously recognized. Our findings provide a fundamental basis for the development of potential mitigation strategies required for the realization of laser damage resistant hafnia films.

Enhancement of laser-induced damage threshold of optical coatings by ion-beam etching in vacuum environment

Ion-beam sputtering (IBS) method was used to etch the different thickness of the outer layer overcoat for high reflection film. Laser resistance improvements enabling to exceed 1.5× have been observed on high reflection coatings. The smoothing process of surface and subsurface convex defect induced by ion-beam etching caused the decreasing electric field intensity. A process model was presented to understand the smoothing process of surface and subsurface convex defect. The decreasing electric field intensity, accompanying with small surface roughness value, low defect density and organic contamination adsorption concentration of sample surface, was attributed to the high laser-induced damage threshold in vacuum environment.