Ion Beam Assistance Research Articles

Effects of ion energy on ion beam assisted deposition textured yttria stabilized zirconia buffer layer of coated conductor

High quality biaxially textured yttria stabilized zirconia (YSZ) thin films, as buffer layers of coated conductors, were deposited on hastelloy substrates by ion beam assisted deposition (IBAD) method with different assisting ion energy E i. The roles of assisting ion beam and the influences of ion energy E i on the structure of the films were studied. It was found that both the out-of-plane alignment and in-plane texture of the IBAD-YSZ films are sensitive to the variation of E i. The results are explained in the paper by different damage tolerance of the differently oriented grains to ion bombardment.

Tungsten doped chromium nitride coatings

Chromium tungsten nitride films were deposited using magnetron sputtering with ion beam assistance. The content of the films was controlled through the power supplied to the chromium and tungsten targets. Results indicate that the tungsten atoms incorporated into chromium nitride films and formed the chromium tungsten nitride solid solution phase. Moreover, results of this study provide further insight into how various concentrations of tungsten affect the lattice constant, preferred orientation, crystallite size, surface morphology, hardness, internal stress, and adhesion of the films.

Effect of assist ion beam voltage on intrinsic stress and optical properties of Ta 2O 5 thin films deposited by dual ion beam sputtering

The optical properties and intrinsic stress of Ta 2O 5 thin films deposited by dual ion beam sputtering (DIBS) were studied as a function of the assist ion beam voltage (250–650 V). When the assist ion beam voltage was in the range of 350–450 V, the transmittance at the quarter-wave point reached its highest value (lowest absorption). The refractive index increased to 2.185 as the assist ion beam voltage increased from 250 to 350 V, but decreased as the assist ion beam voltage was further increased from 350 to 650 V.

Oxygen Ion Beam Assisted Deposition법에 의해 형성된 AC PDP용 MgO 보호막의 특성 연구

MgO layer plays an important role for plasma display panels (PDPs). In this experiment, ion beam assisted deposition (IBAD) methode was uesed to deposit a MgO thin film and the assisting oxygen ion beam energy was varied from 100 eV to 500 eV. In order to investigate the relationship between the secondary electron emission and the defect levels of the MgO layer, we measured the cathodoluminescence (CL) spectra of the MgO thin films, and we analyzed the CL peak intensity and peak transition. The results showed that the assisting ion beam energy played an important role in the peak intensity and the peak transition of the CL spectrum. The properties of MgO thin film were also analyzed using XRD and SEM, these results showed the assisting ion beam energy had direct effect on characteristics of MgO thin film.

MgF 2 and LaF 3 thin film formation with gas cluster ion beam assisted deposition

Gas cluster ion beams (GCIB), containing huge aggregates with several thousands of atoms or molecules, were employed as assist ion beams for fluoride film formation. As gas cluster ions shows low-energy effects, chemical reaction enhancement and strong surface smoothing effects, GCIB-assisted deposition can be a desirable deposition technique for thin film multilayer structures for the ultra-violet region. In this work, SF6-GCIB was employed as the assist ion beam for deposition of fluoride films (MgF 2 and LaF 3). For fluoride films, it had been difficult to use energetic ions during deposition because of damage induced by ion bombardments. With SF 6-GCIB irradiation, the surface roughness of LaF 3 and MgF 2 films decreased with increasing ion current density. From cross-sectional images, the film structure changed from columnar to bulk-like structure with high-dose SF 6-GCIB irradiation.

Influence of plasma ion-beam assistance on TiO 2 and MgF 2 thin films deposited by plasma ion-assisted deposition

Influences of plasma ion-beam assistance on the optical, structural and chemical properties of TiO 2 films, MgF 2 films and TiO 2/MgF 2 narrow band-pass filters deposited by conventional e-beam evaporation (CE) and plasma ion-assisted deposition (PIAD), respectively, were investigated. The results show that PIAD for the TiO 2 film induces a high refractive index, low extinction coefficient, and smooth surface. Also, PIAD changes the TiO 2 film from tensile stress to compressive. In the case of MgF 2 film, the results show that the plasma ion-beam assistance exhibits large extinction coefficient, high optical absorption, and smooth surface. High tensile stress in the CE MgF 2 film is decreased by PIAD. As an application, a TiO 2/MgF 2 multilayer filter, consisting of PIAD TiO 2 films and CE MgF 2 films, has a small total stress and does not exhibit microcracks, while a filter with CE TiO 2 films shows many microcracks due to high tensile stress. In conclusion, it is found that the plasma ion-beam assistance for TiO 2 films is very useful in achieving stable TiO 2/MgF 2 multilayer optical coatings due to the dense microstructure, high refractive index, low extinction coefficient, smooth surface, and compressive stress.

Enhanced visible-light absorption from PdO nanoparticles in nitrogen-doped titanium oxide thin films

Composite films were made by embedding nanoparticles of p-type PdO semiconductor in a n-type titanium oxide matrix. With the assistance of nitrogen ion beam, these PdO nanoparticles were confined to less than a couple of nanometers. The resulting nanocomposite films demonstrated an unusual “redshift” in the optical absorption spectrum, contrary to the well-known quantum size effect from semiconductor nanoparticles. The absorption in the visible-light range is shown to result from absorption by metallic-like nanoparticles as palladium changed its valence state from Pd2+ to Pd in nitrogen-doped titanium oxide matrix under visible-light illumination.

Low-energy ion-assisted control of interfacial structures in metallic multilayers

A molecular dynamics method has been used to simulate the argon ion-assisted deposition of Cu/Co/Cu multilayers and to explore ion beam assistance strategies that can be used during or after the growth of each layer to control interfacial structures. A low-argon ion energy of 5–10 eV was found to minimize a combination of interfacial roughness and interlayer mixing (alloying) during the ion-assisted deposition of multilayers. However, complete flattening with simultaneous ion assistance could not be achieved without some mixing between the layers when a constant ion energy approach was used. It was found that multilayers with lower interfacial roughness and intermixing could be grown either by modulating the ion energy during the growth of each metal layer or by utilizing ion assistance only after the completion of each layers deposition. In these latter approaches, relatively high-energy ions could be used since the interface is buried and less susceptible to intermixing. The interlayer mixing dependence upon the thickness of the over layer has been determined as a function of ion energy.

Low energy ion assisted deposition of Ta∕Cu films

A combination of molecular dynamics simulations and experiments has been used to investigate the use of various low energy ion assisted vapor deposition approaches for controlling the interfacial structures of a model copper∕tantalum multilayer system. Films were grown using argon ion beam assistance with either a fixed or modulated ion energy during metal deposition. The effect of sequential ion assistance (after layer’s deposition) was also investigated. The argon ion energy was varied between 0 and 50eV and the effect on the atomic scale structure of Ta∕Cu film interfaces and the film electrical resistivity were studied. The use of simultaneous argon ion assistance with an ion energy of ∼10eV and an ion∕metal atom flux ratio of ∼6 resulted in atomically sharp interfaces with little intermixing, consistent with simulation predictions. Ion impacts in this range activated surface atom jumping and promoted a step flow film growth mode. Higher energies were also successful at interface flattening, but they caused significant intermixing between the layers and increased film’s resistivity. This could be reduced using modulated ion energy and sequential ion beam assistance. This was again consistent with atomic scale simulations, which indicated that metal layers deposited over an interface before ion assistance was initiated impeded atom exchange across interfaces and therefore intermixing.

Ion-Beam Assist Nano-Texturing of Films

AbstractWe present an ion-beam based fabrication method for growth of single-crystal-like films that does not utilize epitaxy on single crystal substrates. We use ion-beam assisted texturing to obtain biaxial crystalline alignment in a film. This ion-beam assisted deposition (IBAD) texturing can be done on arbitrary, but smooth substrates, including flexible polycrystalline metal tapes. With IBAD texturing of MgO and subsequent homoepitaxial growth we have demonstrated an in-plane mosaic spread FWHM as low as 2° and out-of-plane alignment of 1°. The deposition system we use includes reel-to-reel tape transport for a linear transport of substrate materials through the deposition zones. This allows for high-throughput experimentation via a linear combinatorial experimental design.

Nanometric inclusions of carbonates in Kokchetav diamonds from Kazakhstan: A new constraint for the depth of metamorphic diamond crystallization

Abstract Previous studies have revealed that microdiamonds from the Kokchetav ultra-high pressure metamorphic terrane of Kazakhstan contain nanometric scale inclusions of Si-, Fe-, Ti-, and Cr-oxides. Because the structure of SiO 2 inclusions was not confirmed to be coesite or stishovite due to their very small size, such diamonds formerly served only as an indicator of a minimum pressure, ca. 4 GPa. Geothermobarometry applied to Kokchetav diamond-bearing rocks yielded a wide range of conditions: T = 700 °C–1250 °C, and P = 4–9 GPa. Our paper presents transmission electron microscopy studies with focused ion beam assistance that indicate that diamonds from marbles contain inclusions of aragonite (CaCO 3 ) and magnesite (MgCO 3 ), and that aragonite and nitrogen-bearing nanometric particles are associated with dislocations reflecting diamond growth at relatively high-temperature conditions. We determined the boundary of dolomite stability using the reaction CaMg(CO 3 ) 2 (dolomite) = CaCO 3 (aragonite) + MgCO 3 . This allowed us to utilize available experimental data to evaluate the pressure at which diamond was crystallized. Taking into consideration uncertainties existing between experimental data produced in different laboratories, we propose the pressure for Kokchetav diamond crystallization to be ∼ 6 to 9 GPa. This evaluation is based on the assumption that temperature was determined correctly as 980 °C (minimum) and 1250 °C (maximum) for diamond-grade dolomitic marbles. Our data provide strong evidence that the metasedimentary rocks of the Kokchetav massif containing diamonds were subducted to the depth of ∼ 190–280 km.

Mechanical properties of YBaCuO formed on Ni-based alloy substrates with IBAD buffer layers

Mechanical properties of YBaCuO superconducting tape produced by a multi-stage metal-organic chemical vapor deposition (MOCVD) technique have been investigated. It is important for YBaCuO superconducting tape to tolerate stress strain and maintain flexibility in order to be used for electric power applications, magnetic applications, and so on. At this time, we have produced an approximately 0.25 /spl mu/m YBaCuO layer on a pulse laser deposition (PLD)-CeO/sub 2//ion beam assisted (IBAD)-Gd/sub 2/Zr/sub 2/O/sub 7//Ni-based alloy substrate by an MOCVD technique, and approximately 4 /spl mu/m Ag was sputtered on it as a protective layer. The thickness of each layer was approximately 1.0 /spl mu/m, 1.0 /spl mu/m and 0.1 mm respectively. Its critical current was about 50 A. The mechanical properties of YBaCuO tape formed on Ni-based alloy substrates with a CeO/sub 2//Gd/sub 2/Zr/sub 2/O/sub 7/ buffer layer will be described. Tensile or compressive bend stress tests were conducted, and normalized critical current and the value n were evaluated. The degradation of its critical current was confirmed not to be in the big problem level in manufacturing applications. In addition, the surfaces of YBaCuO layers were observed by scanning electron microscopy and no crack was observed on them. Next, axial tensile stress tests were conducted and the YBaCuO tape was compared with biaxially textured Ni-3at.%W alloy substrates and YBaCuO layers on Ag substrates. Axial tensile stress characteristics of the YBaCuO tape were confirmed to be much higher than others. The YBaCuO tape was confirmed to have adequate axial tensile stress characteristics for designing a coil which can tolerate electromagnetic force.

Effect of thermal annealing on the optical properties and residual stress of TiO_2 films produced by ion-assisted deposition

The effects of thermal annealing of titanium oxide films deposited by ion-beam assistance at annealing temperatures from 100 degrees C to 300 degrees C on the residual stress and optical properties of the films was investigated. The refractive indices and extinction coefficients increased gradually as the temperature was increased from 100 degrees C to 200 degrees C and then declined gradually as the temperature was increased further from 200 degrees C to 300 degrees C. The film lost oxygen and slowly generated lower suboxides as the annealing temperature was reduced below 200 degrees C, as determined by x-ray photoelectron spectroscopy (XPS). As the annealing temperature increased above 200 degrees C, the lower suboxides began to capture oxygen and form stable oxides. XPS measurements were made to verify both the binding energy associated with the Ti 2p line and the variation of the O 1s line. A Twyman-Green interferometer was employed for phase-shift interferometry to study the residual stress. The residual stress declined as the temperature was reduced from 100 degrees C to 200 degrees C because the lower suboxides reduced the stress in the film. Above 200 degrees C, the film began to capture oxygen, so the residual stress rose. At 300 degrees C, the film was no longer amorphous as the anatase was observed by x-ray diffraction.

Synthesis of carbon nitride thin films by low-energy ion beam assisted evaporation: on the mechanisms for fullerene-like microstructure formation

Carbon nitride (CN x ) thin films were grown at different substrate temperatures by low-energy (<100 eV) ion beam assistance deposition (LE-IBAD) in order to discern possible formation mechanisms of a fullerene-like (FL) microstructure. The samples are compared to those of well-structured FL-CN x films synthesized by reactive magnetron sputtering (MS). The comparison yields similar trends for both techniques, such as limitation of the nitrogen content at 20–25 at.%, dominance of sp 2 hybrids, as well as thermally activated chemical desorption of C x N y species from the substrate during growth. However, CN x films produced by LE-IBAD are amorphous. The lack of FL structural features correlates with a lower degree of sp 2 clustering, attributed to the promotion of nitrile groups. Therefore, low-energy ion bombardment is shown not to be a sufficient condition for the growth of FL-CN x . This result reinforces the eventual relevance of pre-formed C x N y species at the sputtering target in MS for the introduction and/or evolution of FL arrangements.

Electron field emission and surface morphology of a-C and a-C:H thin films

Hydrogen-free amorphous carbon (a-C) and hydrogenated amorphous carbon (a-C:H) films have been deposited on (100)-oriented single crystal Si substrates by cathodic-arc vacuum deposition (CAVD) with and without ion beam assistance and also plasma-enhanced chemical vapour deposition. The field emission characteristics of films were measured by a diode technique. Prior to emission characteristics measurements, the films were annealed under vacuum for 1 h at 350 and 950 °C. On the basis of Raman spectroscopy analyses, it was established that the field emission takes place for films with high content of sp 2 carbon sites. The increase in sp 2 carbon sites is the result of application of the ion beam assistance during deposition of films and effect of the annealing treatment at 950 °C. The a-C films formed by CAVD method with ion-beam assistance having developed surface morphology possesses improved emission characteristics. It was observed that in annealed a-C:H films, the activating emission centers are active as a direct electrical field of 12 V/μm is applied to their surface.

Mechanical behaviour of metallic thin films on polymeric substrates and the effect of ion beam assistance on crack propagation

The mechanisms of crack propagation in metallic films on polymeric substrates have been studied through in situ atomic force microscopy observations of thin films under tensile stresses and finite element stress calculations. Two series of films – ones deposited with ion beam assistance, the others without – have been investigated. The observations and stress calculations show that ion beam assistance can change drastically the propagation of cracks in coated materials: by improving the adhesion film/substrate, it slows down the delamination process, but in the same time enhances the cracks growth in the thickness of the material.

Field emission from hafnium oxynitride films prepared by ion beam-assisted deposition

HfN x O y films are deposited by ion beam-assisted deposition on (1 0 0) silicon substrates at room temperature. According to X-ray diffraction analysis, at least two phases exist in HfN x O y film, and X-ray photoelectron spectroscopy results are in good agreement with these analysis. Both annealing and increasing assisting ion beam current increase the concentration of the β-Hf 7O 8N 4 phase in HfN x O y films. Field emission with low turn on field is reported. Field emission results suggest that the concentration of β-Hf 7O 8N 4 plays an important role in field emission properties. Hydrogen plasma treatment also enhances field emission properties. These results indicate that the HfN x O y film is an excellent material for field emitter.

Influence of Ar ion-beam assistance and annealing temperatures on properties of TiO2 thin films deposited by reactive DC magnetron sputtering

TiO2 thin films were prepared by using a reactive DC magnetron sputtering method with Ar ion-beam assistance. The effect of the Ar ion-beam current on the structural and optical properties of the reactive magnetron sputtered TiO2 thin films was studied. The as-deposited films were subjected to annealing with the atmospheric environment, and the change of film properties after annealing was investigated. When the Ar ion-beam assistance was applied, the deposited TiO2 thin films were found to induce a higher deposition rate, a higher packing density and refractive index, a lower extinction coefficient, and a smoother surface than that of the film deposited without ion-beam assistance. The structures of all as-deposited films were amorphous. In the annealing process, the ion-beam-assisted TiO2 thin films had a phase transition from amorphous to anatase polycrystalline with a strong TiO2 anatase (101) peak at a temperature of 400 °C. At above 400 °C, the refractive index of deposited films increased by an anatase structure and the extinction coefficient increased due to a reduction in the oxidation of TiO2 thin films.

Incident angle effects on microstructure and magnetic properties of Fe–Nb thin films using IBAD

The effects of the incident angle on the microstructure and magnetic properties of Fe–Nb thin films grown by Ar ion beam assisted deposition have been investigated. A new metastable crystalline bcc phase and an amorphous phase were obtained at 45° ion incident angle, while a mixture of bcc Nb and bcc Fe was formed under the incident angles of the assisting ion beam of 30° and 60°. The difference caused by the variation of incident angle is discussed on the basis of energy transfer and competition between the effects of surface energy and ion beam channeling.

Area-selective formation of Si nanocrystals by assisted ion-beam irradiation during dual-ion-beam deposition

We investigate the effect of Ar-ion-beam irradiation during the deposition of SiOx films by dual-ion-beam deposition system. Ion-beam irradiation effectively increases the oxygen content, x, in SiOx films indicative of the preferential sputtering of Si phase as compared to SiO2 phase in SiOx films. We observe the intense photoluminescence from nonirradiated sample after postdeposition annealing at 1100°C indicating the formation of Si nanocrystals as shown by a cross-sectional transmission electron microscope. However, the increased oxygen content in ion-beam-irradiated sample results in small optical volume of small Si nanocrystals not sufficient for yielding appreciable photoluminescence intensity after postdeposition annealing. The property is utilized for achieving the area-selective formation of Si nanocrytals by inserting a shadow mask in assist ion beam during deposition.