Ion Beam Assisted Deposition Research Articles

Fabrication of single TiO2 nanotube devices with Pt interconnections using electron- and ion-beam-assisted deposition

Device fabrication using nanostructured materials, such as nanotubes, requires appropriate metal interconnections between nanotubes and electrical probing pads. Here, electron-beam-assisted deposition (EBAD) and ion-beam-assisted deposition (IBAD) techniques for fabrication of Pt interconnections for single TiO2 nanotube devices are investigated. IBAD conditions were optimized to reduce the leakage current as a result of Pt spreading. The resistivity of the IBAD-Pt was about three orders of magnitude less than that of the EBAD-Pt, due to low carbon concentration and Ga doping, as indicated by X-ray photoelectron spectroscopy analysis. The total resistances of single TiO2 nanotube devices with EBAD- or IBAD-Pt interconnections were 3.82 × 1010 and 4.76 × 108 Ω, respectively. When the resistivity of a single nanotube is low, the high series resistance of EBAD-Pt cannot be ignored. IBAD is a suitable method for nanotechnology applications, such as photocatalysis and biosensors.

Biaxial Texture Evolution in MgO Films Fabricated Using Ion Beam-Assisted Deposition

The growth of multifunctional thin films on flexible substrates is important technologically, because flexible electronics require such a platform. In this study, we examined the evolution of biaxial texture in MgO films prepared using ion beam-assisted deposition (IBAD) on a Hastelloy substrate. Texture and microstructure developments were characterized through in situ reflection high-energy electron diffraction monitoring, x-ray diffraction, and atomic force microscopy, which demonstrated that biaxial texture was developed during the nucleation stage (~2.2 nm). The best biaxial texture was obtained with a thickness of approximately 12 nm. As MgO continued to grow, the influence of surface energy was reduced, and film growth was driven by the attempt to minimize volume free-energy density. Thus the MgO grains were subsequently rotated at the (002) direction toward the ion beam. In addition, an approach was developed for accelerating in-plane texture evolution by pre-depositing an amorphous MgO layer before IBAD.

Structure, Composition and Adhesion Strength of Hf Coatings Deposited on Mo Substrate by Ion Beam Sputtering

Hafnium films were prepared on the molybdenum substrate at room temperature by ion beam assisted deposition (IBAD) and post-annealing was conducted to know their status under high temperature. The structure and composition of Hf coatings were confirmed by XRD, STEM and EDX, respectively. The adhesion strength between the coating and the substrate was evaluated by a nanoscratch tester. The results show that some dilution occurs at the coating/substrate interface and that Mo combines with Hf to form a HfMo2 alloy after high temperature annealing. The adhesive force of the Hf coating was increased from 120 mN to 160 mN after annealing.

Activities of HIP joining of plasma-facing armors in the blanket first-wall in Korea

Joining technology for dissimilar materials was developed for the fabrication of an ITER blanket first-wall, which consisted of Be, CuCrZr, and stainless steel (SS). The Be/CuCrZr/SS joint was fabricated using a hot isostatic pressing (HIP) method. Beryllium armor was joined to the CuCrZr/SS block at 580°C under 100MPa. The optimal interlayer coatings of Cr/Cu and Ti/Cr/Cu were developed using an ion-beam assisted physical vapor deposition. Beryllium is also a candidate armor material for the TBM first-wall. Successful joining of Be to ferritic-martensitic steel (FMS) was accomplished using an HIP method by introducing the thick diffusion barrier. A thick diffusion barrier of a Cu foil(10μm) limited the excessive diffusion and prevented the formation of brittle phases at the Be/FMS interface. Be and FMS were bonded at 650–850°C; however, a temperature of lower than 750°C was recommended to avoid material degradation of FMS. In addition, the joining of W to FMS has been developed. Tungsten is another armor material applicable to more severe plasma conditions. The large difference in the thermal expansion between W and FMS was resolved by introducing the Ti interlayer and Mo separator. Moreover, the double-staged HIP (the first stage at 900°C and 100MPa and the second stage at 750°C and 70MPa) was applied to suppress the edge delamination of W/FMS joints during thermal history.

Growth of simplified buffer template on flexible metallic substrates for YBa2Cu3O7-δ coated conductors

A much simplified buffer structure, including a three-layer stack of LaMnO3/MgO/composite Y2O3–Al2O3, was proposed for high performance YBa2Cu3O7-δ (YBCO) coated conductors. In this structure, biaxially textured MgO films were prepared on solution deposition planarized amorphous substrate through ion-beam-assisted deposition (IBAD) technology. By the use of in situ reflection high-energy electron diffraction monitor, X-ray diffraction and atomic force microscope, the influence of deposition parameters, such as film deposition rate, ion penetrate energy and ion beam flux, on crystalline orientation, texture, lattice parameter and surface morphology was systematically investigated. Moreover, stopping and range of ion in mater simulation was performed to study the effects of ion bombardment on MgO films. By optimizing IBAD process parameters, the best biaxial texture showed ω-scan of (002) MgO and Φ-scan of (220) MgO yield full width at half maximum values of 2.4° and 3.7°, indicating excellent biaxial texture. Subsequently, LaMnO3 films were directly deposited on the IBAD-MgO template to improve the lattice mismatch between MgO and YBCO. Finally, YBCO films grown on this simplified buffer template exhibited a critical current density of 2.4 MA/cm2 at 77 K and self-field, demonstrating the feasibility of this buffer structure.

Self-heating technique of metallic substrate for reel-to-reel and double-sided deposition of YBa2Cu3O7−δ films

A new, simple, and highly efficient heating technology for metal tape substrates is proposed and applied to reel-to-reel and double-sided film deposition. In this technology, direct electrical current (I DC) is conducted into the metal layer of oxide-buffered metal substrate to induce heat. Different substrate surface temperatures were achieved by varying I DC from 22 to 25 A. At these temperatures, a series of 1-μm-thick and 5-cm-long YBa2Cu3O7−δ (YBCO) films were fabricated on ion-beam-assisted deposition (IBAD) templates through metal organic chemical vapor deposition. X-ray diffraction analysis on the samples revealed that the YBCO film changed its growth mode from mixed a-axis and c-axis to purely c-axis with increasing I DC. The optimal out-of-plane and in-plane texture reached ~1.4° and 3.5°, respectively. A 30-m-long and 500-nm-thick single-sided YBCO-coated conductor was also prepared through reel-to-reel deposition using the proposed heating method. The fabricated conductor presented homogeneous crystallization and texture and exhibited a critical current density at self-field and 77 K (J c 77K, 0T ) of 2.8–3.2 MA/cm2. Moreover, 500-nm-thick YBCO films were fabricated simultaneously on both sides of the double-sided IBAD template. The two sides of films demonstrated uniform texture and J c 77K, 0T of 3.2 MA/cm2. Results demonstrated that the proposed substrate heating technology can be used for reel-to-reel and double-sided deposition of YBCO-coated conductors.

이온빔을 이용한 STS304와 알루미나 브레이징 접합효과

Abstract Using a surface modification technique, ion beam assisted deposition (IBAD) of Ti thin film it becomes possible to prepare an active ceramic surface to braze Al 2 O 3 -STS304 with conventional Ag-Cu eutectic compositionfiller metal. Researches on bonding formations at interfaces of ceramic joints were mainly related on the developmentof filler metals to ceramic, the process parameters, and clarifications of reaction products. From the results, the reactive brazing is a very convenient technique compared to the conventional Mn-Mo method. However melting pointof reactive filler is still higher than that of Ag-Cu eutectic and it forms the brittle inter metallic compound. Recently several new approaches are introduced to overcome the main shortcomings of the reactive metal brazing in ceramic-metal, metal vapor vacuum arc ion source was introduced to implant the reactive element directly into the ceramics surface, and sputter deposition with sputter etching for the deposition of active material.

The challenge and promise of low-temperature bioceramic coatings: An editorial

Abstract Low-temperature coating deposition is carried out at or near ambient temperature temperatures, much below the incongruent melting point of hydroxyapatite. However, frequently post-depositional heat treatment must be applied to either crystallise amorphous calcium phosphate (ACP), transform (dehydrated/dehydroxylated) precursor phases such as octacalcium phosphate to hydroxyapatite, and/or to remove organic compounds used in coating preparation, for example during sol–gel, dip coating, electrochemical, and electrophoretic deposition. The contributions to this Special Issue deal predominately with low-temperature deposition of hydroxyapatite coatings applied by electrochemical deposition (ECD), plasma electrolytic oxidation (PEO), electrophoretic deposition (EPD), and ion-beam assisted deposition (IBAD) to the surfaces of Ti6Al4V, cp-Ti, CoCrMo, Mg, as well as Zr and PEEK substrates.

Preparation, characterization and in vitro response of bioactive coatings on polyether ether ketone.

Polyether ether ketone (PEEK) is a highly heat-resistant thermoplastic with excellent strength and elastic modulus similar to human bone, making it an attractive material for orthopedic implants. However, the hydrophobic surface of PEEK implants induces fibrous encapsulation which is unfavorable for stable implant anchorage. In this study, PEEK was coated via ion-beam-assisted deposition (IBAD) using a two-layer design of yttria-stabilized zirconia (YSZ) as a heat-protection layer, and hydroxyapatite (HA) as a top layer to improve osseointegration. Microstructural analysis of the coatings showed a dense, uniform columnar grain structure in the YSZ layer and no delamination from the substrate. The HA layer was found to be amorphous and free of porosities in its as-deposited state. Subsequent heat treatment via microwave energy followed by autoclaving crystallized the HA layer, confirmed by SEM and XRD analysis. An in vitro study using MC3T3 preosteoblast cells showed improved bioactivity in heat-treated sample groups. Cell proliferation, differentiation, and mineralization were analyzed by MTT assay and DNA content, osteocalcin expression, and Alizarin Red S (AR-S) content, respectively. Initial cell growth was increased, and osteogenic maturation and mineralization were accelerated most on coatings that underwent a combined microwave and autoclave heat treatment process as compared to uncoated PEEK and amorphous HA surfaces. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 560-567, 2017.

Enhanced visible light adsorption of heavily nitrogen doped TiO2 thin film via ion beam assisted deposition

Nitrogen doping is widely used to enhance the visible light absorption of TiO2 by narrowing the bandgap. It is recognized that this modification is sensitively affected by the spatial distribution of anion doping. In order to explore the effects of nitrogen distributions in TiO2, we synthesized nitrogen-doped TiO2 thin films via the ion-beam assisted deposition (IBAD) technique and calcinations in NH3 atmosphere. The morphology and crystal structure of these thin films were characterized by scanning electron microscope and X-ray diffraction respectively. The chemical states and spatial distributions of nitrogen in the TiO2 were investigated by X-ray photoelectron spectroscopy. The nitrogen can be heavily and uniformly doped in anatase thin film by the IBAD technique with the N/Ti atomic ratio ranging from 61.3 to 51.9 %, much higher than that calcinated at 500 °C under NH3 atmosphere, which fluctuated from 23.2 to 4.5 %. The time-dependent depth profile of the N 1s spectrum shows that the doped nitrogen in the TiON thin film synthesized via IBAD distributes from the surface to the inner layer. Compared to the traditional calcinations synthesized methods, the as-synthesized TiON thin film, shows a much higher absorption in the visible-light range. Its light absorbance spectrum extends to over 700 nm, covering most of the visible-light region.

Highly efficient colloid–solution deposition planarization of Hastelloy substrate for IBAD-MgO film

A simple and efficient way to planarize Hastelloy substrate for high-temperature superconductors has been developed. The colloid–solution deposition planarization (CSDP) method consists of two steps: colloid deposition planarization and subsequent precursor solution deposition planarization. The surface roughness of Hastelloy belt decreased from 4.0 to 0.8 nm after Y2O3 colloid deposition and then to 0.3 nm after further yttrium acetate solution deposition. The shrinkage percentage of the colloid deposition layer and solution deposition layer was 20 and 77 %, respectively. Compared with traditional solution deposition planarization, the higher planarization efficiency of CSDP can be attributed to the lower shrinkage percentage of the colloid deposition layer. As a result, ion-beam-assisted deposition (IBAD)-MgO on Hastelloy substrate with CSDP coating showed crystal orientation. Hastelloy belt planarized by the CSDP method will provide a low-cost substrate for high-temperature superconductors.

Copper thin films by ion beam assisted deposition: Strong texture, superior thermal stability and enhanced hardness

Nanocrystalline metals generally exhibit exceptionally high strength. However, their susceptibility to grain growth restricts their applications in high temperature environments. The current study presents that nanocrystalline Cu thin films produced by ion beam assisted deposition (IBAD) are able to sustain their as-deposited microstructure and high hardness upon annealing at high temperatures. IBAD-Cu films exhibit a strong (111) fiber texture, which is caused by the ion beam induced effects of substrate cleaning, preferential damage and preferential sputtering. The microstructure of the IBAD-Cu films is stable at temperatures up to 800°C (80% of the melting point of Cu). The hardness of the as-deposited IBAD-Cu films can reach a maximum value of 3.85GPa. Even after annealing, their hardness is still much higher than that of the normally deposited (without ion beam) films as well as their bulk nanocrystalline counterparts before heat treatment. The excellent thermal stability of microstructure is attributed to the formation of nanometer-sized voids and their pinning effect on grain boundary migration. The kinetics of void formation, the contribution of twin boundaries and ion beam induced defects to the hardness are analyzed and discussed. The findings in this study demonstrate that IBAD is an effective method for the stabilization of microstructure and mechanical properties of nanocrystalline metal thin films.

Biomechanical evaluation of different hydroxyapatite coatings on titanium for keratoprosthesis

Stable tissue integration is important to keratoprosthesis (KPro). The aim of this study was to evaluate the tissue bonding ability of hydroxyapatite (HAp)-coated titanium KPro. The samples were divided into three groups: test groups (IBAD group and AD group) and Ti control. The coated samples had a HAp layer created by ion beam assisted deposition (IBAD) or aerosol deposition (AD). The surface characteristics were analyzed with SEM, AFM, and XRD. The samples were surgically inserted into the muscles of rabbits. Eight weeks after healing, the attachment to the tissue was tested with a universal test device. The three samples exhibited distinctive surface morphology. The force to remove the HAp implants from the muscles was significantly greater than that of Ti group (P < 0.01), with the AD samples requiring the greatest force (P < 0.01). After removal, SEM showed that the tissue was firmly attached to the surface of AD samples. Photomicrographs of the peri-implant muscles showed a layer of aligned fibrous tissue without severe inflammation. The AD samples had more fibroblasts. Results indicate that because of enhanced mechanical adhesion of soft tissue to the implants, HAp-coated Ti by AD is a suitable KPro skirt material.

Improvement and characterization of high-reflective and anti-reflective nanostructured mirrors by ion beam assisted deposition for 944 nm high power diode laser

Single-layer and multi-layer coatings were applied on the surface of diode laser facets as mirrors. This thin film mirrors were designed, deposited, optimized and characterized. The effects of mirrors on facet passivation and optical properties of InGaAs/AlGaAs/GaAs diode lasers were investigated. High-Reflective (HR) and Anti-Reflective (AR) mirrors comprising of four double-layers of Al2O3/Si and a single layer of Al2O3, respectively, were designed and optimized by Macleod software for 944nm diode lasers. Optimization of Argon flow rate was studied through Alumina thin film deposition by Ion Beam Assisted Deposition (IBAD) for mirror improvement. The nanostructured HR and AR mirrors were deposited on the front and back facet of the laser respectively, by IBAD system under optimum condition. Atomic Force Microscope (AFM), Vis-IR Spectrophotometer, Field Emission Scanning Electron Microscopy (FESEM) and laser characterization Test (P–I) were used to characterize various properties of mirrors and lasers. AFM images show mirror’s root mean square roughness is nearly 1nm. The Spectrophotometer results of the front facet transmission and the back facet reflection are in good agreement with the simulation results. Optical output power (P) versus driving current (I) characteristics, measured before and after coating the facet, revealed a significant output power enhancement due to optimized AR and HR optical coatings on facets.

Development of Long REBCO Coated Conductors by PLD-REBCO/Sputter-CeO2/IBAD-MgO at SJTU and SSTC

Through collaboration with SJTU, a pilot REBCO coated conductor fabrication line has been set up at the Shanghai Superconductor Technology Corporation Ltd., in 2013. To reduce the cost of coated conductor tapes, simplified tape architecture was developed, i.e., PLD-REBCO/Sputter-CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /IBAD-MgO on metal tapes with amorphous oxide barrier layer. High-quality long REBCO coated conductors have been successfully fabricated by pulsed laser deposition (PLD) plus magnetron sputter and ion-beam-assisted deposition (IBAD) processes. Under optimized conditions, the IBAD-MgO layers showed pure (001) orientation and excellent in-plane texture. AFM observation showed MgO layer had very smooth surface. The RMS is less than 1 nm. On the textured MgO layer, sputter deposited single CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> cap layer showed pure (001) orientation and excellent in-plane texture of 47-6°. A reel-to-reel PLD process with high deposition rate was already scaled up to 100-m/h tape speed. One-micrometer-thick REBCO films had a high critical current density of over 3.0 MA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (at 77 K, self-field). The critical current density of 2 μm thick films is still more than 2.5 MA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Hundred-meterlong coated conductor tapes with over 500 A/cm performance have been routinely fabricated. Currently, the process optimization for kilometer-long coated conductor tapes is underway.

Development of a 66 kV-5 kArms Class HTS Power Cable Using REBCO Tapes With High Critical Current

High temperature superconducting (HTS) cables are able to achieve large power capacity and low-loss power transmission. Fujikura Ltd. worked on developing a 66 kV-5 kArms HTS power cable using high critical current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) REBCO tapes in the Japanese national project. One of the technical targets in this project was to reduce AC loss to less than 2 W/m at 5 kArms. REBCO tapes with 240 A/4 mm-width of I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> at 77 K, self field, which were fabricated by ion-beam-assisted-deposition (IBAD) and pulsed laser deposition (PLD) methods, were applied to the HTS power cable. As a result, we succeeded in developing the 20 m-long 66 kV-5 kArms HTS power cable. The measured AC loss was achieved 1.4 W/m at 77 K and 1.0 W/m at 67 K at 5 kArms. On the other hand, it is considered that the eddy current loss of the stainless-steel cryostat pipe of HTS cable become obvious in the case of the single-core cable with the large current capacity. It is suggested that the eddy current loss of the stainless-steel cryostat pipe is due to the internal magnetic flux. Therefore, the eddy current loss of the stainless-steel cryostat pipe as well as uniform current distribution of HTS conductor and shield layer should be taken into account for designing the winding direction and pitch of HTS conductor and shield layer of HTS cable. In this work, the measured eddy current loss of the stainless-steel cryostat pipe is also compared with the calculated one.

The Permeation Behavior of Deuterium through 1Cr18Ni9Ti Stainless Steel with TiN+TiC+TiN Multiple Films

TiN+TiC+TiN multiple films are deposited on the surface of 1Cr18Ni9Ti stainless steel by ion-beam assisted deposition technology. The characteristics of films are tested by XPS, SEM and XRD, which showed that the film are compact and uniform with a thickness of about 15μm, and have a good adherence with the substrate below 773 K. The diffraction peaks in the XRD patterns for TiC and TiN are broadened, implying that the multiple films are deposited on the surface of 1Cr18Ni9Ti stainless steel. Meanwhile, the C-H bonded CH4-appears in the infrared spectra of multiple films, suggesting that the CH4- is in a static state, so hydrogen atom cannot migrate from the site bonded with carbon to a neighboring site. The deuterium permeability in 1Cr18Ni9Ti stainless steel coated with multiple films is 2-3 orders of magnitude lower than that in pure 1Cr18Ni9Ti stainless steel substrate from 473 K to 773 K.

High-performance irreversibility field and flux pinning force density in BaHfO3-doped GdBa2Cu3Oy tape prepared by pulsed laser deposition

The high irreversibility field Bi and strong flux pinning force were obtained for BaHfO3-doped GdBa2Cu3Oy tapes on a metallic Hastelloy substrate with an ion beam-assisted deposition MgO buffer layer. At 77.3 K, Bi of 15.8 T and the maximum flux pinning force density of 23.5 GN/m3 for B ∥ c were achieved for the 1.5 vol % BaHfO3-doped GdBa2Cu3Oy tape, which are the world's highest recorded values for REBa2Cu3Oy-coated conductors on metallic substrates (RE = rare earth). From the flux pinning analysis, the c-axis correlated pinning by well-aligned BaHfO3 nanorods plays an important role in achieving the high irreversibility field and flux pinning force density performance.

Optimization of bandpass optical filters based on TiO2nanolayers

The design and realization of high-quality bandpass optical filters are often very difficult tasks due to the strong correlation of the optical index of dielectric thin films to their final thickness, as observed in many industrial deposition processes. We report on the optimization of complex optical filters in the visible and NIR spectral ranges as realized by ion beam-assisted electron beam deposition of silica and titanium oxide multilayers. We show that this process always leads to amorphous films prior to thermal annealing. On the contrary, the optical dispersion of TiO2 nanolayers is highly dependent on their thickness, while this dependence vanishes for layers thicker than 100 nm. We demonstrate that accounting for this nonlinear dependence of the optical index is both very important and necessary in order to obtain high-quality optical filters.

Thermoelectric Figures of Merit of Zn4Sb3 and Zrnisn-based Half-heusler Compounds Influenced by Mev Ion-beam Bombardments

Semiconducting β-Zn4Sb3 and ZrNiSn-based half-Heusler compound thin films with applications as thermoelectric (TE) materials were prepared using ion beam assisted deposition (IBAD). High-purity solid zinc (Zn) and antimony (Sb) were evaporated by electron beam to grow the β-Zn4Sb3 thin film while high-purity zirconium (Zr) powder and nickel (Ni) tin (Sn) powders were evaporated by electron beam to grow the ZrNiSn-based half-Heusler compound thin film. Rutherford backscattering spectrometry (RBS) was used to analyze the composition of the thin films. The grown thin films were subjected to 5 MeV Si ions bombardment for generation of nanostructures in the films. We measured the thermal conductivity, Seebeck coefficient, and electrical conductivity of these two systems before and after 5 MeV Si ions beam bombardment. The two material systems have been identified as promising TE materials for the application of thermal-to-electrical energy conversion, but the efficiency still limits their applications. The electronic energy deposited due to ionization in the track of MeV ion beam couldcause localized crystallization. The nanostructures produced by MeV ion beam can cause significant change in both the electrical and the thermal conductivity of thin films, thereby improving the efficiency. We used the 3ω-method (3rd harmonic) measurement system to measure the cross-plane thermal conductivity, the van der Pauw measurement system to measure the electrical conductivity, and the Seebeck-coefficient measurement system to measure the cross-plane Seebeck coefficient. The thermoelectric figures of merit of the two material systems were then derived by calculations using the measurement results. The MeV ion-beam bombardment was found to decrease the thermal conductivity of thin films and increase the efficiency of thermal-to-electrical energy conversion.