Metalorganic Deposition Process Research Articles

Microstructure of Er<sub>2</sub>O<sub>3 </sub>Coating Layer of Hydrogen Penetration Control

Erbium oxide (Er2O3) was shown to be a high potential candidate for tritium penetration barrier and electrical insulator coating for advanced breeding blanket systems such as liquid Li, Li-Pb or molten-salt blankets. Recently, Hishinuma et. al. succeeded to form Er2O3 coating layer on large interior surface area of metal pipe using Metal Organic Chemical Vapor Deposition (MOCVD) process. In this work, Er2O3 coating layer of hydrogen penetration control on stainless steel 316 (SUS 316) substrate have been investigated to the effect of hydrogen penetration and using SEM, TEM and SAED patterns. Er2O3 coating layer of before hydrogen penetration was granular structures from SEM observation. Er2O3 coating layer was columnar grains from TEM observation. TEM image and SAED patterns obtained from Er oxide film can be understood that the growth direction of Er2O3 film was [110].

Solution-processed perfect uniaxial orientation of perovskite titanate (Ca0.65Sr0.35)0.997Pr0.002TiO3 phosphor thin films

We report the preparation of perfect uniaxially-oriented (Ca0.65Sr0.35)0.997Pr0.002TiO3 phosphor thin films on glass substrates with an oriented Dion–Jacobson perovskite RbLaNb2O7 seed layer prepared using an excimer-laser-assisted metal organic deposition process. The obtained phosphor thin films on the seed layer exhibited perfect uniaxial (010)-orientation below 40 mJ/cm2. At 40 mJ/cm2, the film showed intense red luminescence at 612 nm. The luminance was evaluated to be 14.5 cd/m2 under 300 nm excitation light at 3.5 mW/cm2, and this value was 26% higher than that of unoriented film. Above 45 mJ/cm2, the phosphor thin films had a mud-crack pattern. Thus, the crystal orientation quality and luminescence intensity was lowered. The precise control of preparation conditions is necessary for preparation of heterostructures with good orientation quality.

Study of thermal stability of distributed Bragg reflectors based on epitaxial rare-earth oxide and silicon heterostructures

Thermal stability of rare-earth oxide/silicon multilayer heterostructure-based distributed Bragg reflectors under typical metal organic chemical vapor deposition process temperatures with an ambience of typical process gases was studied. Gadolinium oxide or erbium oxide based two period (¼λ oxide, ¾λSi) blue light (λ = 450 nm) mirrors with Si layer on the top were annealed in H2, N2, and H2 + NH3 gases for 20 min at 1015 °C in a metal organic chemical vapor deposition chamber. Changes in the structure were analyzed using x-ray diffraction and transmission electron microscopy. Reflectivity measurements were used for evaluation of optical properties of the reflectors before and after annealing. Chemical reaction between gadolinium oxide and silicon are revealed by reduction of reflectivity of Gd2O3/Si based distributed Bragg's reflector and GdSi2-x attributed peaks detected by x-ray diffraction. No major changes were detected in the Er2O3/Si heterostructure-based reflector, indicating good chemical and crystal stability of erbium oxide.

Evaluation of Adhesion Strength of Er<sub>2</sub>O<sub>3 </sub>Coating Layer for an Advanced Breeding Blanket System Applied to Thermal Cycles using Nano-Scratch Method

The electrical insulator and hydrogen permeation barrier coatings are important materials to realize the liquid metal and molten-salt typed breeding blanket systems. We found that erbium oxide (Er2O3) is one of the promising materials as the electrical insulator and hydrogen permeation restraint coatings. Establishing the mechanical property evaluation method for these coating is extremely important to certify the durability of coating material in the blanket systems. The adhesion strength property, which is one of the key mechanical properties of coating materials, was investigated using the nano-scratch method. From the results, it was found that the nano-scratch test was able to evaluate the adhesion strength of the Er2O3 coating synthesized by the Metal Organic Chemical Vapor Deposition (MOCVD) process with high reproducibility. Furthermore, the adhesion strength of the Er2O3 coating before and after thermal cycling was evaluated using this method. The adhesion strength after 50 thermal cycles at 700 ◦ C was kept around 70% compared with that before thermal cycling.

A comparative study on the flux pinning properties of Zr-doped YBCO film with those of Sn-doped one prepared by metal-organic deposition

We investigated the flux pinning properties of both 10 mol% Zr-and Sn-doped <TEX>$YBa_2Cu_3O_{7-{\delta}}$</TEX> (YBCO) films with the same thickness of ~350 nm for a comparative purpose. The films were prepared on the <TEX>$SrTiO_3$</TEX> (STO) single crystal substrate by the metal-organic deposition (MOD) process. Compared with Sn-doped YBCO film, Zr-doped one exhibited a significant enhancement in the critical current density (<TEX>$J_c$</TEX>) and pinning force density (<TEX>$F_p$</TEX>). The anisotropic <TEX>$J_{c,min}/J_{c,max}$</TEX> ratio in the field-angle dependence of <TEX>$J_c$</TEX> at 77 K for 1 T was also improved from 0.23 for Sn-doped YBCO to 0.39 for Zr-doped YBCO. Thus, the highest magnetic <TEX>$J_c$</TEX> values of 9.0 and <TEX>$2.9MA/cm^2$</TEX> with the maximum <TEX>$F_p$</TEX> (<TEX>$F_{p,max}$</TEX>) values of 19 and <TEX>$5GN/m^3$</TEX> at 65 and 77 K for H // c, respectively, could be achieved from Zr-doped YBCO film. The stronger pinning effect in Zr-doped YBCO film is attributable to smaller <TEX>$BaZrO_3$</TEX> (BZO) nanoparticles (the average size <TEX>${\approx}28.4$</TEX> nm) than <TEX>$YBa_2SnO_{5.5}$</TEX> (YBSO) nanoparticles (the average size <TEX>${\approx}45.0$</TEX> nm) incorporated in Sn-doped YBCO film since smaller nanoparticles can generate more defects acting as effective flux pinning sites due to larger incoherent interfacial area for the same doping concentration.

Preparation by MOCVD and Microwave Absorbing Properties of CF@Fe

The CF@Fe composites were prepared by depositing precusor Fe(CO)5 on carbon fiber (CF) to form continuous α-Fe film through metal organic chemical vapor deposition (MOCVD) process. The X-ray diffraction (XRD), scanning electron microscope (SEM) and a vector network analyzer were used to characterize the structure and electromagnetic properties of the powder and to study absorbing properties, The results showed that the film layer deposited on the surface of carbon fibers was pure α-Fe phase, at about 0.7 μm in thickness. After being deposited by consecutive α-Fe film, the CF electromagnetic properties changed significantly with the absorbing capacity being improved. By using electromagnetic parameters of the coaxial ring samples, the reflectance curves of the CF and CF@Fe coating at thickness of 2 mm were calculated, The curves showed that absorption peak of the samples deposited by the consecutive α-Fe film moved to the high frequency, the value of the minimum reflection peak reduced, and the bandwidth (less than −10 dB) increased 4.2 GHz.

RF plasma MOCVD of Y2O3 thin films: Effect of RF self-bias on the substrates during deposition

Yttrium oxide (Y2O3) thin films have been deposited by radio frequency plasma assisted metal organic chemical vapor deposition (MOCVD) process using (2,2,6,6-tetramethyl-3,5-heptanedionate) yttrium (commonly known as Y(thd)3) precursor in a plasma of argon and oxygen gases at a substrate temperature of 350°C. The films have been deposited under influence of varying RF self-bias (−50V to −175V) on silicon, quartz, stainless steel and tantalum substrates. The deposited coatings are characterized by glancing angle X-ray diffraction (GIXRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry and scanning electron microscopy (SEM). GIXRD and FTIR results indicate deposition of Y2O3 (BCC structure) in all cases. However, XPS results indicate nonstoichiometric cubic phase deposition on the surface of deposited films. The degree of nonstoichiometry varies with bias during deposition. Ellipsometry results indicate that the refractive index for the deposited films is varying from 1.70 to 1.83 that is typical for Y2O3. All films are transparent in the investigated wavelength range 300–1200nm. SEM results indicate that the microstructure of the films is changing with applied bias. Results indicate that it is possible to deposit single phase cubic Y2O3 thin films at low substrate temperature by RF plasma MOCVD process. RF self-bias that decides about the energy of impinging ions on the substrates plays an important role in controlling the texture of deposited Y2O3 films on the substrates. Results indicate that to control the structure of films and its texture, it is important to control the bias on the substrate during deposition. The films deposited at high bias level show degradation in the crystallinity and reduction of thickness.

Microstructural characterization of TFA-MOD processed Y1−xGdxBa2Cu3O7−y with BaZrO3

Y1−xGdxBa2Cu3O7−y with BaZrO3 film was fabricated on CeO2 buffered LaMnO3/ion beam assisted deposition-MgO/Gd2Zr2O7/Hastelloy C276TM substrates by the metal organic deposition process using trifluoroacetates. Both microstructural and analytical characterizations were performed by transmission electron microscopy with selected area electron diffraction method and energy dispersive X-ray spectroscopy. The thickness of Y1−xGdxBa2Cu3O7−y with BaZrO3 film was found approximately 700nm and the film was composed of c-axis oriented Y1−xGdxBa2Cu3O7−y grains. Several types of particles, (Y,Gd)2Cu2O5, CuO and BaZrO3, were formed within the Y1−xGdxBa2Cu3O7−y film, whose sizes were about 100–200nm for (Y,Gd)2Cu2O5 and CuO particles, and about 10–20nm for BaZrO3 particles, respectively. In the Y1−xGdxBa2Cu3O7−y film, (Y,Gd)2Cu2O5 and CuO particles were dispersed heterogeneously, whereas BaZrO3 nanoparticles were found dispersed homogeneously with random orientation. In addition, electron tomographic observation was carried out to attain the three-dimensional information of polyhedral BaZrO3 nanoparticles.

Three-dimensional imaging using fast micromachined electro-absorptive shutter

A 20-MHz switching high-speed light-modulating device for three-dimensional (3-D) image capturing and its system prototype are presented. For 3-D image capturing, the system utilizes a time-of-flight (TOF) principle by means of a 20-MHz high-speed micromachined electro-absorptive modulator, the so-called optical shutter. The high-speed modulation is obtained by utilizing the electro-absorption mechanism of the multilayer structure, which has an optical resonance cavity and light-absorption epilayers grown by metal organic chemical vapor deposition process. The optical shutter device is specially designed to have small resistor–capacitor–time constant to get the high-speed modulation. The optical shutter is positioned in front of a standard high-resolution complementary metal oxide semiconductor image sensor. The optical shutter modulates the incoming infrared image to acquire the depth image. The suggested novel optical shutter device enables capturing of a full high resolution-depth image, which has been limited to video graphics array (VGA) by previous depth-capturing technologies. The suggested 3-D image sensing device can have a crucial impact on 3-D–related business such as 3-D cameras, gesture recognition, user interfaces, and 3-D displays. This paper presents micro-opto-electro-mechanical systems-based optical shutter design, fabrication, characterization, 3-D camera system prototype, and image evaluation.

In situ measurement of crystallization of oxide thin films during irradiation with pulsed UV laser in chemical solution deposition process

The epitaxial and polycrystalline growth of lanthanum strontium manganite films on single crystalline strontium titanate and lanthanum aluminate substrates, respectively, under the irradiation with XeCl lasers in the excimer laser-assisted metal organic deposition (ELAMOD) process have been previously reported. In order to investigate the growth phenomena, we monitored the thermal radiation from the sample surfaces irradiated with a pulsed ultraviolet laser in situ with near-infrared sensors. The cooling of the lanthanum strontium manganite films on strontium titanate substrates was significantly slower than that of films on lanthanum aluminate substrates. A similar behavior was also observed by the numerical simulation study. This difference in the cooling decay curves may play an important role in the mode by which crystal growth occurs in the ELAMOD process.

Intrinsic strain effect on critical current in Cu-stabilized GdBCO coated conductor tapes with different substrates

The intrinsic strain effect on critical current, Ic in Cu-stabilized GdBCO coated conductor (CC) tapes under bending and uniaxial tension has been investigated. The bending deformation tolerance of Ic in GdBCO CC tapes, fabricated by reactive co-evaporation by deposition and reaction (RCE-DR) with substrate materials of Hastelloy and stainless steel and fabricated by the metal organic chemical vapour deposition (MOCVD) process was evaluated. The intrinsic strain response of Ic under bending was found to be independent of the fabrication process, the substrate material and the geometry of the sample. For samples with a Hastelloy substrate, the intrinsic strain response of Ic/Icmax under bending was well correlated with those under uniaxial tension. However, for samples with a stainless steel substrate, these had a large strain sensitivity for Ic under uniaxial tension even though this showed a much higher irreversible strain limit up to 1.05%.

Three-Dimensional Characterization of BaZrO&lt;sub&gt;3&lt;/sub&gt; Precipitates in Y&lt;sub&gt;1-x&lt;/sub&gt;Gd&lt;sub&gt;x&lt;/sub&gt;Ba&lt;sub&gt;2&lt;/sub&gt;Cu&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;7-y&lt;/sub&gt; Prepared by TFA-MOD Using STEM-Tomography

Y1-xGdxBa2Cu3O7-yfilm with BaZrO3was fabricated on CeO2buffered LaMnO3/ion beam assisted deposition MgO/Gd2Zr2O7/Hastelloy C276TMsubstrates by the trifluoroacetates metal organic deposition process, whose microstructural and elemental analyses were performed by transmission electron microscopy. Y1-xGdxBa2Cu3O7-yfilm with the thickness about 700 nm was found composed of c-axis oriented grains and large numbers of randomly oriented precipitates, such as (Y,Gd)2Cu2O5, CuO and BaZrO3. (Y,Gd)2Cu2O5and CuO precipitates were heterogeneously dispersed in the Y1-xGdxBa2Cu3O7-ymatrix with their sizes ranging between 100 and 200 nm, and BaZrO3precipitates were uniformly dispersed with their sizes ranging between 10 and 20 nm. Electron tomography with elemental information was performed further to reveal the three-dimensional information of BaZrO3 precipitates.

Second Generation Wire Development at AMSC

AMSC has established a Second Generation (2G) High-Temperature Superconductor (HTS) wire manufacturing technology based on the Rolling Assisted Biaxially Textured Substrate and Metal Organic Deposition processes. AMSC's 2G wire (Amperium) has been used by a wide range of customers for development and testing of initial commercial HTS-based applications. Although the Amperium wire properties and quantities satisfy the requirements for these initial projects, improvements in critical current, field performance, and cost are beneficial for large-scale commercial and military applications. As Amperium wire manufacturing continues to ramp up, AMSC's R&amp;D program has focused on increasing critical current, and the development of nonmagnetic substrates. The R&amp;D process developed for a single-coat, 1.2 &amp;#x03BC;m YBCO film has been transferred to production-scale equipment, resulting in the first Amperium wires with critical currents reaching 500 A/cm-w (77 K, self-field) in production length. A nonmagnetic substrate, which minimizes ferromagnetic substrate losses in ac cable applications, has been produced in R&amp;D lengths and demonstrated in an Amperium cable wire.

Multifunctional Manganese Single Source Precursor for the Selective Deposition of MnF2 or Mn3O4

Abstract A novel Mn(II) precursor, the Mn(hfa)2●tmeda, was successfully applied to the deposition of manganese containing nanostructures in Metal Organic Chemical Vapor Deposition (MOCVD) processes at atmospheric and reduced pressure. Experimental data evidenced that different phases were obtained, selectively and reproducibly, on varying the operating pressure. Manganese difluoride (MnF2) nanorod assemblies were obtained under atmospheric pressure, while hausmannite (Mn3O4) nanostructured films were obtained under reduced pressure. X-ray diffraction patterns in grazing incidence mode and energy dispersive X-ray analyses confirmed the phase nature and composition of the manganese containing nanostructures. Field-emission scanning electron microscopy images evidenced the nanostructure morphology of both the MnF2 and Mn3O4 phases.

High Performance of YBCO Films Prepared by Fluorine-Free MOD Method and a Direct Annealing Process

Chemical solution-deposited (CSD) is a cost-effective non-vacuum method for YBCO coated conductor fabrication. We developed a new fluorine-free metal-organic deposition (MOD) method with metal acetates, propionic acid and xylene as the starting materials. Using this non-fluorine MOD method, we were able to get high performance YBCO superconducting films within a shortened heat treatment time, which was reduced by at Least 5 h in comparison with that for pyrolysis-annealing non-fluorine MOD process. Superconducting property, with a critial current density (Jc) over 0.55MA/cm2at 77K, self-field has been obtained for 380 nm epitaxial YBCO thin films on (00l) LaAlO3(LAO) single crystal substrate. Owing to the low price of starting materials and shorter heat treatment time, fluorine-free MOD method is a very effective and cost-cutting process.

Flux pinning characteristics of Sn-doped YBCO film by the MOD process

Compared with the undoped YBa2Cu3O7−δ (YBCO) film, 10mol% Sn-doped YBCO film exhibited significantly enhanced critical current densities (Jc) in magnetic fields up to 5T at 65 and 77K for H//c, indicating that the Sn-doped YBCO film possesses more effective flux pinning centers. Both samples were grown on the SrTiO3 (STO) (100) single crystal substrates by the metal-organic deposition (MOD) process. Larger Jc (77K, 1T) values of Sn-doped YBCO film are observed over a wide field-orientation angle (θ) except the field-orientations close to the ab-plane of YBCO (85°<θ<95°). Smaller Jc values for 85°<θ<95° in Sn-doped YBCO film are most probably caused by a reduced intrinsic pinning effect along the ab-plane due to high density Sn-containing nanoparticles trapped in the YBCO matrix. The effective pinning centers in Sn-doped YBCO film are attributable to Sn-containing nanoparticles trapped in the YBCO matrix which could be identified as the YBa2SnO5.5 (YBSO) phase by STEM (scanning transmission electron microscopy)-EDS (energy dispersive X-ray spectroscopy) analysis. Further analyses by HR-TEM (high resolution-transmission electron microscopy) revealed that YBSO nanoparticles completely surrounded by the YBCO matrix had random orientation with YBCO while those located at the interface of YBCO/STO substrate had epitaxial relationship with YBCO.

Preparation of YBa2Cu3O7-δ Patterned Film Using Metal Organic Deposition with Electron Beam Irradiation

A microfabrication method to produce YBa2Cu3O7-δ (YBCO) was investigated using the metal organic deposition (MOD) process with electron beam (EB) irradiation. EB irradiation causes decomposition of the C–H and –COO– bonds and desorption of oxygen atoms in the metal octylate precursors. Therefore, oxidation of metal atoms could become harder for the MOD with EB irradiation than for the conventional MOD because of lack of oxygen, and consequently a longer prefiring time is required to ensure oxidation of the metal atoms. Additionally, the heating rate for crystallization was increased to improve film coverage. Finally YBCO film with superconductivity was successfully obtained.

Effect of Annealing Temperature on the Structural and Electrical Properties of a-Axis-Oriented SrTiO3 Films

Strontium titanate films with high a-axis-orientation [a(100) = 94.1%] were deposited on (111) Pt/Ti/SiO2/Si substrates by the metal organic deposition process. X-ray diffraction shows that the degree of a-axis orientation increases with increasing annealing temperature. It is found that the dielectric properties are improved by a higher annealing temperature, while the leakage currents are also enhanced, and the possible causes of temperature dependence are discussed.

Pulsed Laser Assisted Polycrystalline Growth of Oxide Thin Films for Efficient Processing

ABSTRACTWe have investigated the polycrystalline growth by means of an excimer laser assisted metal organic deposition process and the strategy for the efficient growth. It was revealed that the pulsed photo thermal heating properties must be controlled by changing the laser fluence according to the substrate properties, such as thermal diffusivity. The threshold of the teff value for initial crystal nucleation is approximately 70 ns for oxide thin films. For the fabrication of good quality films with high crystallinity and without a laser ablation of the film surface, it is necessary that the irradiated laser fluence is adjusted to the conditions of teff (efficient annealing time) &gt; 70 ns and Tmax (maximum temperature) &lt; Tm (melting point). Obtained oxide films by using the pulsed UV laser has large crystallite size, and it well functioned to enhance physical properties of films. For further efficient growth for polycrystalline growth of the oxide films, the starting solution containing nanoparticles is very useful: it is named as photo-reaction of nanoparticles process.

Friction and wear properties of copper matrix composites reinforced by tungsten-coated carbon nanotubes

Carbon nanotubes (CNTs) were coated by tungsten layer using metal organic chemical vapor deposition process with tungsten hexacarbonyl as a precursor. The W-coated CNTs (W-CNTs) were dispersed into Cu powders by magnetic stirring process and then the mixed powders were consolidated by spark plasma sintering to fabricate W-CNTs/Cu composites. The CNTs/Cu composites were fabricated using the similar processes. The friction coefficient and mass wear loss of W-CNTs/Cu and CNTs/Cu composites were studied. The results showed that the W-CNT content, interfacial bonding situation, and applied load could influence the friction coefficient and wear loss of W-CNTs/Cu composites. When the W-CNT content was 1.0 wt.%, the W-CNTs/Cu composites got the minimum friction coefficient and wear loss, which were decreased by 72.1% and 47.6%, respectively, compared with pure Cu specimen. The friction coefficient and wear loss of W-CNTs/Cu composites were lower than those of CNTs/Cu composites, which was due to that the interfacial bonding at (W-CNTs)-Cu interface was better than that at CNTs-Cu interface. The friction coefficient of composites did not vary obviously with increasing applied load, while the wear loss of composites increased significantly with the increase of applied load.