Ion Beam Assisted Deposition Research Articles

Self-Healing Phenomenon and Dynamic Hardness of C60-Based Nanocomposite Coatings

The phenomenon of surface self-healing in C60-based polymer coatings deposited by ion-beam assisted physical vapor deposition was investigated. Nanoindentation of the coatings led to the formation of a protrusion rather than an indent. This protrusion was accompanied by an abnormal shape of the force-distance curve, where the unloading curve lies above the loading curve due to an additional force applied in pulling the indenter out of the media. The coatings exhibited a nanocomposite structure that was strongly affected by the ratio of C60 ion and C60 molecular beam intensities during deposition. The coatings also demonstrated the dynamic hardness effect, where the effective value of the hardness depends significantly on the indentation speed.

Effect of nitrogen atomic percentage on N+-bombarded MWCNTs in cytocompatibility and hemocompatibility.

N+-bombarded multi-walled carbon nanotubes (N+-bombarded MWCNTs), with different nitrogen atomic percentages, were achieved by different N ion beam currents using ion beam-assisted deposition (IBAD) on MWCNTs synthesized by chemical vapor deposition (CVD). Characterizations of N+-bombarded MWCNTs were evaluated by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Raman spectroscopy, and contact angle. For comparison, the in vitro cytocompatibility of the N+-bombarded MWCNTs with different N atomic percentages was assessed by cellular adhesion investigation using human endothelial cells (EAHY926) and mouse fibroblast cells (L929), respectively. The results showed that the presence of nitrogen in MWCNTs accelerated cell growth and proliferation of cell culture. The higher nitrogen content of N+-bombarded MWCNTs, the better cytocompatibility. In addition, N+-bombarded MWCNTs with higher N atomic percentage displayed lower platelet adhesion rate. No hemolysis can be observed on the surfaces. These results proved that higher N atomic percentage led N+-bombarded MWCNTs to better hemocompatibility.

Exchange bias magnetism in films of NiFe/(Ni,Fe)O nanocrystallite dispersions

Ni3Fe/(Ni,Fe)O thin films having a nanocrystallite dispersion morphology were prepared by a reactive ion beam-assisted deposition technique. The crystallite sizes of these dispersion-based films were observed to decrease from 8.4 ± 0.3 nm to 3.4 ± 0.3 nm as the deposition flow-rate increased from 2.78% to 7.89% O2/Ar. Thin film composition was determined using selective area electron diffraction images and Multislice simulations. Through a detailed analysis of high resolution transmission electron microscopy images, the nanocrystallites were determined to be Ni3Fe (a ferromagnet), NiO, and FeO (both antiferromagnets). It was determined that the interfacial molar Ni3Fe ratio in the nanocrystallite dispersions increased slightly at first, then decreased as the oxygen content was increased; at 7.89% O2/Ar, the interfacial molar ratio was essentially zero (only NiO and FeO remained). For nanocrystallite dispersion films grown with O2/Ar flow-rate greater than 7.89%, no interfacial (intermixed) Ni3Fe phase was detected, which resulted in no measurable exchange bias. Comparing the exchange bias field between the nanocrystallite dispersion films at 5 K, we observed a decrease in the magnitude of the exchange bias field as the nanocrystallite size decreased. The exchange bias coupling for all samples measured set in at essentially the same temperature (i.e., the exchange bias blocking temperature). Since the ferromagnetic/anti-ferromagnetic (FM/AFM) contact area in the nanocrystallite dispersion films increased as the nanocrystallite size decreased, the increase in the magnitude of the exchange bias could be attributed to larger regions of defects (vacancies and bond distortions) which occupied a significant portion of the FM/AFM interfaces in the nanocrystallite dispersion films.

MeV Si ion modifications on the thermoelectric generators from Si/Si + Ge superlattice nano-layered films

Abstract The performance of thermoelectric materials and devices is characterized by a dimensionless figure of merit, ZT = S 2 σT / K , where, S and σ denote, respectively, the Seebeck coefficient and electrical conductivity, T is the absolute temperature in Kelvin and K represents the thermal conductivity. The figure of merit may be improved by means of raising either S or σ or by lowering K . In our laboratory, we have fabricated and characterized the performance of a large variety of thermoelectric generators (TEG). Two TEG groups comprised of 50 and 100 alternating layers of Si/Si + Ge multi-nanolayered superlattice films have been fabricated and thoroughly characterized. Ion beam assisted deposition (IBAD) was utilized to assemble the alternating sandwiched layers, resulting in total thickness of 300 nm and 317 nm for 50 and 100 layer devices, respectively. Rutherford Backscattering Spectroscopy (RBS) was employed in order to monitor the precise quantity of Si and Ge utilized in the construction of specific multilayer thin films. The material layers were subsequently impregnated with quantum dots and/or quantum clusters, in order to concurrently reduce the cross plane thermal conductivity, increase the cross plane Seebeck coefficient and raise the cross plane electrical conductivity. The quantum dots/clusters were implanted via the 5 MeV Si ion bombardment which was performed using a Pelletron high energy ion beam accelerator. We have achieved remarkable results for the thermoelectric and optical properties of the Si/Si + Ge multilayer thin film TEG systems. We have demonstrated that with optimal setting of the 5 MeV Si ion beam bombardment fluences, one can fabricate TEG systems with figures of merits substantially higher than the values previously reported.

Ion beam assisted sputter deposition of ZnO for silicon thin-film solar cells

Ion beam assisted deposition (IBAD) is a promising technique for improving the material quality of ZnO-based thin films. The operation of an auxiliary Ar+ ion source during deposition of ZnO : Ga thin films by dc magnetron sputtering led to an improvement in crystalline texture, especially at low temperatures due to momentum transfer from the ions to the growing film. Etching of IBAD-ZnO : Ga films in diluted HCl revealed crater-like surface structures with crater diameters of up to 600 nm. These structures are usually achieved after deposition at high substrate temperatures. This is an indication that the grain structure was remarkably changed by bombarding these films during deposition in terms of increasing the compactness of the ZnO : Ga films. Subsequent annealing procedures led to an improvement in the electrical and optical properties. Hydrogenated microcrystalline silicon (µc-Si : H) solar cells exhibited enhanced efficiency as compared to cells on other low-temperature sputtered reference ZnO films. This improvement was ascribed to light trapping by the modified etching behaviour of the IBAD-ZnO : Ga films as well as improved transparency after the vacuum annealing step.

Enhancement of the magnetic interfacial exchange energy at a specific interface in NiFe/CoO/Co trilayer thin films via ion-beam modification

A series of ferromagnetic Ni80Fe20(55 nm)/antiferromagnetic CoO (25 to 200 nm)/ferromagnetic Co (55 nm)/SiO2(substrate) trilayer thin films were fabricated by ion-beam assisted deposition in order to understand the role of ion beam modification on the interfacial and interlayer coupling. The microstructural study using transmission electron microscopy, X-ray reflectometry, and polarised neutron reflectometry showed that ion-beam modification during the deposition process led to an oxygen-rich Co/CoO nanocomposite interface region at the bottom layer. This interface caused a high exchange bias field for the ferromagnetic cobalt. However, the exchange bias for top permalloy ferromagnet remained low, in line with expectations from the literature for the typical interfacial energy. This suggest that the ion-beam enhancement of the magnetic exchange bias is localized to the Co/CoO interface where local microstructural effects provide the dominant mechanism.

Fourier transform infrared spectroscopy analysis of thin boron nitride films prepared by ion beam assisted deposition

AbstractThin boron nitride (BN) films were synthesized by ion beam assisted deposition (IBAD). From Fourier transform infrared spectroscopy (FTIR) analysis results, it was found that: the films with the co‐presence of explosion‐phase BN (E‐BN) and sp2‐bonded hexagonal BN (h‐BN), and those with pure h‐BN were formed in the respective substrate temperature regions of 20–85 °C and 350–400 °C, under nitrogen ion irradiation (ion energy from 500 to 1000 eV), while the substrate temperature at 400 °C and mixed nitrogen and argon ion irradiation were necessary for the formation of sp3‐bonded cubic BN (c‐BN). To our knowledge, the E‐BN phase was formed firstly by IBAD in this study. The crystalline phase identification through the FTIR results was in line with X‐ray diffraction results. The shift of the c‐BN peak position is usually attributed to remaining compressive stress in the film. In this work, the downward shift of the c‐BN peak position and the broadening of the c‐BN peak, which were observed when the film thickness increased, can be interpreted using a phenomenological description of structural disordering in the c‐BN sites. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Low energy ion beam assisted deposition of controllable solid state electrolyte LiPON with increased mechanical properties and ionic conductivity

Lithium phosphorus oxynitride (LiPON) solid state amorphous film electrolytes were synthesized by ion beam assisted deposition (IBAD) using Li3PO4 target under nitrogen reactive plasma. IBAD presents an advantage of controllable nitrogen content of the films by adjusting N2 and Ar flow ratio. X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), nanoindenter, and profiler were employed to characterize LiPON films. Our results indicate that the film at N2 and Ar flow ratio of 1:8 showed the best surface morphology and mechanical properties. The highest N atomic percentage of 2.32% was also obtained at this synthesis circumstance, and the resultant LiPON film electrolyte showed higher ionic conductivity of 4.5 × 10−6 S/cm at room temperature, as well as the highest hardness of 6.8 GPa and the lowest compressive stress of 147.2 MPa. It is believed that as-prepared LiPON solid state electrolyte film optimized can effectively prevent delamination from electrodes, showing some promising application in thin film lithium ion batteries.

The influence of change in structural characteristics induced by beam current on mechanical properties of LiPON solid-state electrolyte films

Lithium phosphorus oxynitride (LiPON) solid-state electrolyte films were synthesized by ion beam assisted deposition (IBAD) system from Li3PO4 target in nitrogen reactive plasma. Extensive measurements were taken to investigate the change in structural characteristics caused by beam current as well as the effects on mechanical properties of LiPON films. The existence of the triply coordinated nitrogen atoms in structure of LiPON films induced by ion beam bombardment was proved by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), which can produce the positive effects on Li+ mobility. Analysis of nanoindentation indicated that the hardness and elastic modulus of LiPON solid-state electrolyte films varies with the beam current. The highest hardness of 5.8 GPa and the highest critical fracture load of 3.01 mN with lower compressive stress occurred at equal atomic percentage of nitrogen and phosphorus, i.e. N/P = 1 at the beam current of 18 mA. The higher hardness and lower stress are important parameters to prevent LiPON solid-state electrolyte films delamination from electrodes, which is crucial in evaluating the electrochemical performance of thin-film lithium ion battery.

Preparation of Epitaxial MgO Films Deposited by RF Magnetic Sputtering on the IBAD-MgO Substrate

We deposited epi-MgO films on the textured ion beam assisted deposition (IBAD)-MgO substrates by RF magnetic sputtering at different substrate temperatures (600–850 °C), RF powers (110–224 W) and oxygen partial pressures (19.5–58.6 mTorr). The microstructure and surface morphology of epi-MgO films were characterized by X-ray diffraction (XRD) and atom force microscope (AFM). It was found that epi-MgO films with c-axis orientation could be easily fabricated for broad parameter ranges. But the in-plane full width half maximum (FWHM) of the epi-MgO film was dependent on the parameters, and the epi-MgO film with the smallest FWHM value of 5.22° was obtained at the optimum parameters. What’s more, the GdBa2Cu3O7 films deposited on the epi-MgO/IBAD-MgO substrate by RF magnetic sputtering showed c-axis orientation.

Stress induced phase transition in Gd2O3 films by ion beam assisted reactive electron beam-physical vapor deposition (EB-PVD)

The structural evolution of thick polycrystalline gadolinium oxide (Gd2O3) films deposited by reactive electron beam-physical vapor deposition (EB-PVD) is investigated. High deposition rates (>5Å/s) lead to the growth of mixed phase films which are of the cubic phase near the film/substrate interface before forming monoclinic phase as distance from the interface increases. By decreasing the deposition rate to <1Å/s for films grown at temperatures of 650°C, films up to one micron thick have been grown in the pure cubic phase. The growth of the thermodynamically stable cubic phase under these conditions is attributed to both higher surface mobility of the adatoms during growth and to increased tensile stress within the film. Ion beam assisted deposition (IBAD) was then performed to introduce compressive stress into the film resulting in the formation of the monoclinic phase. Wafer curvature, X-ray diffraction, confocal Raman spectroscopy, and scanning electron microscopy are utilized to characterize the film and present evidence for the existence of a stress-induced phase transition in the Gd2O3 films.

Growth modes and epitaxy of FeAl thin films on a-cut sapphire prepared by pulsed laser and ion beam assisted deposition

FeAl films around equiatomic composition are grown on a-cut (112¯0) sapphire substrates by ion beam assisted deposition (IBAD) and pulsed laser deposition (PLD) at ambient temperature. Subsequent successive annealing is used to establish chemical order and crystallographic orientation of the films with respect to the substrate. We find a strongly [110]-textured growth for both deposition techniques. Pole figures prove the successful preparation of high quality epitaxial films by PLD with a single in-plane orientation. IBAD-grown films, however, exhibit three in-plane orientations, all of them with broad angular distributions. The difference of the two growth modes is attributed to the existence of a metastable intermediate crystalline orientation as concluded from nonassisted sputter depositions at different substrate temperatures. The formation of the chemically ordered crystalline B2 phase is accompanied by the expected transition from ferromagnetic to paramagnetic behavior of the films. In accordance with the different thermally induced structural recovery, we find a step-like magnetic transition to paramagnetic behavior after annealing for 1 h at TA = 300 °C for IBAD deposition, while PLD-grown films show a gradual decrease of ferromagnetic signals with rising annealing temperatures.

Effect of ion beam assisted deposition on the growth of indium tin oxide (ITO) nanowires

We developed a method to control the alignment and density of indium tin oxide (ITO) nanowires by using ion beam assisted deposition (IBAD).

Development of a 66 kV-5 kA Class HTS Power Cable with IBAD/PLD REBCO Tapes

High temperature superconducting (HTS) cables are able to achieve large power capacity and low-loss power transmission. In the Japanese national project, Fujikura Ltd. worked on developing a 66 kV-5 kArms HTS power cable using high critical current (Ic) REBa2Cu3Ox (REBCO, RE = rare earth) tapes. One of the technical targets in this project is to reduce AC loss to less than 2W/m at 5 kArms. The REBCO tapes with 240 A/4mm-width of Ic at 77K, self field, which were fabricated by Ion-beam-assisted-deposition (IBAD) and Pulsed Laser Deposition (PLD) method, were applied to a HTS power cable in order to achieve extremely low AC loss. As a result, we have succeeded in developing a 20 m-long 66 kV-5 kArms HTS power cable. The measured AC loss was achieved 1.4W/m at 77K and 1.0W/m at 67K at 5 kArms.

Progress in research and development for REBCO coated conductors by reactive co-evaporation

This paper reviews recent progress in research and development (R&D) of reactive co-evaporation for high performance REBCO coated conductors in Korea. Two types of reactive co-evaporation methods were developed for the deposition of SmBCO and GdBCO superconducting layers respectively on the IBAD (Ion Beam Assisted Deposition)-MgO template in the Korean coated conductor project. Batch type reactive co-evaporation equipment and its processing were developed for SmBCO coated conductors at Korea Electrotechnology Research Institute (KERI) in conjunction with the Korea Advanced Institute of Science and Technology (KAIST), and a very high critical current exceeding 1,000 A/cm at 77 K in the self field was achieved through the optimization of deposition parameters. Reel-to-reel type reactive co-evaporation processing with a high conversion rate was also developed, while long length GdBCO coated conductors have been routinely produced by SuNAM Co. The minimum critical current of 422 A/cm-w at 77 K in self field was confirmed for 1 km-long GdBCO tape.

Fabrication of long-length ion beam-assisted deposited MgO templates for YBCO-coated conductors

The biaxially textured ion beam-assisted deposited (IBAD)-MgO templates were successfully prepared on polycrystalline Hastelloy metal substrate with reel-to-reel system for YB2Cu3O7−δ (YBCO)-coated conductors. By the solution deposition planarization technique, amorphous Y2O3 films were coated on untreated Hastelloy substrate as the bed layer to obtain smooth, dense, and crack-free surface for subsequent IBAD-MgO deposition. The 50 m long IBAD-MgO and homo-epitaxial (epi)-MgO buffer layers deposited on Y2O3 films exhibit excellent crystallographic consistency along the scope with full width half maximum (FWHM) values of (110) ΔΦ and (200) Δω in the range of 5.5°–6.0° and 3.0°–3.5°, respectively. To match the lattice constant of YBCO material, LaMnO3 cap layer was fabricated on IBAD-MgO templates by radio frequency (rf) magnetron sputtering with the FWHM values of in-plane and out-of-plane of 6.8° and 3.7°, respectively, indicating excellent biaxial texture.

Intérêt et précision d’un logiciel de navigation dans la mise en place de prothèse de hanche : à partir d’une série prospective de 75 cas

In this article, we report a highly efficient bilayer OLED with a maximum luminance up to 62 000 cd/m2 and a threshold voltage of 3.8 V. The device structure is indium-tin-oxide (ITO)/N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-diphenyl-4,4′-diamine (TPD)/tris-(8-hydroxyquinoline) aluminum (Alq3)/LiF/Al. Ion beam assisted deposition (IBAD) process is used to deposit the aluminum cathode on the LiF layer. The IBAD process improves the OLED performance both by increasing the maximum luminance by a factor of 3 and by reducing the threshold voltage for light-emission. The IBAD process also enhances the microstructure and morphology of the Al layer and leads to denser and more homogeneous layers. The resulting highly-packed microstructure acts as a barrier to moisture and oxygen and inhibits their penetration into the Alq3 layer, leading to the OLED lifetime and stability increasing. In order to optimize the IBAD process parameters, prior to the OLED deposition, we have characterized aluminum films deposited on glass substrates by using atomic force microscopy and X-ray diffraction.

Comparative investigation on the adhesion of hydroxyapatite coating on Ti–6Al–4V implant: A review paper

Hydroxyapatite (HA) has been used in clinical bone graft procedures for the past 25 years. Although a biocompatible material, its poor adhesion strength to substrate makes it unsuitable for major load-bearing devices. Investigations on various deposition techniques of HA coating on Ti–6Al–4V implants have been made over the years, in particular to improve its adhesion strength to the metal alloy and its long-term reliability. This review comprehensively analyzes nine techniques mostly used for deposition of HA onto Ti–6Al–4V alloys. The techniques reviewed are Plasma sprayed deposition, Hot Isostatic Pressing, Thermal Spray, Dip coating, Pulsed Laser deposition (PLD), Electrophoretic deposition (EPD), Sol–Gel, Ion Beam Assisted deposition (IBAD), and Sputtering. The advantages and disadvantages of each method over other techniques are discussed. The adhesion strength and the factors affecting the adhesion of HA coating on Ti–6Al–4V implants are also compared.

Properties of Ta2O5 thin films prepared by ion-assisted deposition

Tantalum penta-oxide (Ta2O5) thin films were deposited onto highly polished and clean, fused silica glass substrates via ion beam-assisted deposition at room temperature using a high-vacuum coater equipped with an electron beam gun. The effects of ion beam parameters, oxygen flow rate, and deposition rate on the optical and structural properties as well as the stress of Ta2O5 films were studied. It has been revealed that Ta2O5 thin films deposited at 300eV ion beam energy, 60μA/cm2 ion current density, 20sccm oxygen flow rate and 0.6nm/s deposition rate demonstrated excellent optical, structural and compressive stress.

Influence of Silver Incorporation on Toughness Improvement of Diamond-Like Carbon Film Prepared by Ion Beam Assisted Deposition

Six silver-containing diamond-like carbon films (Ag-DLC), each with a particular content of Ag, were deposited on M2 high speed steel substrates in an ion beam assisted deposition (IBAD) system. Systematic investigation of the influence of the incorporation of Ag on the adhesion and impact-resistant properties of Ag-DLC films was conducted, and the toughness of individual films was revealed. Results verified that the doping of silver distinctly influenced the toughness of Ag-DLC films. Typically: (i) the variation of Ag contents and nanocrystallites dispersed in the DLC matrix tended to induce change of film toughness as a result of changing the film adhesion and impact-resistance behaviors; (ii) the evidence of improvement in the toughness of the film (especially for the film containing 15.2% silver) could be clearly seen by the larger critical adhesion forces, and the better adhesion performance and impact-resistant properties. The failure mechanism of both scratch and impact tests served to reveal how the toughness of the Ag-DLC films was affected by Ag content.