In-plane XRD Research Articles

Suppression of in-plane (001) texture component in FePt-oxide granular films by adding a carbon buffer layer

Investigation of magnetic properties and nanostructure of FePt-B2O3 granular film with carbon buffer layer (BL) of various thicknesses is reported. When the thickness of carbon BL is varied from 0 to 0.6 nm, saturation magnetization (Msfilm) is almost constant at around 750 emu/cm3 and perpendicular magnetic anisotropy (Ku⊥film) changes from around 1.0×107 to 2.0×107 erg/cm3. For the granular film with the carbon BL thicker than 0.6 nm, both Msfilm and Ku⊥film decrease. The reduction of Msfilm for the granular film by adding a carbon BL may be due to the alloying of carbon into the FePt magnetic grains. The enhancement of Ku⊥film for the film with a 0.6 nm carbon BL is considered due to the reduction of the in-plane texture component which is supported by the in-plane XRD. The reduction of Ku⊥film for the film with a carbon BL thicker than 0.6 nm is considered due to random growth of magnetic grains on a continuous carbon BL which is supported by the TEM cross-section images. According to these results, the employment of an un-continuous thin carbon BL is a promising method to enhance c-axis texture orientation of the FePt-oxide granular films.

Current State and Perspectives of Exfoliated Zeolites.

Zeolites are highly efficient industrial catalysts and sorbents with microporous framework structures. Approximately 10% of the frameworks, but eventually all in the long run, have produced both 3D crystals and 2D layers. The latter can be intercalated and expanded like all 2D materials but proved difficult to exfoliate directly into suspensions of monolayers in solution as precursors for unique synthetic opportunities. Successful exfoliations have been reported recently and are overviewed in this perspective article. The discussion highlights 3 primary challenges in this field, namely finding suitable 2D zeolite preparations that exfoliate directly in high yield, proving uniform layer thickness in solution and identifying applications to exploit the unique synthetic capabilities and properties of exfoliated zeolite monolayers. Four zeolites have been confirmed to exfoliate directly into monolayers: 3 with known structures-MWW, MFI, and RWR and one unknown, bifer with a unit cell close to ferrierite. The exfoliation into monolayers is confirmed by the combination of 5-6 characterization techniques including AFM, in situ and in-plane XRD, and microscopies. The promising areas of development are oriented films and membranes, intimately mixed zeolite phases, and hierarchical nanoscale composites with other active species like nanoparticles and clusters that are unfeasible by solid state processes.

(Digital Presentation) Oxygen Evolution Activity of RuO2/MO2/TiO2(110) (M = Ir, Sn) Surfaces in Acidic Electrolyte

Introduction Developing highly active and durable electrocatalysts for oxygen evolution reaction (OER) are required for efficient hydrogen production by polymer electrolyte membrane water electrolysis (PEMWE). While RuO2 shows the highest OER activity among pure transition metal oxides catalysts, the low durability hinders its practical application as OER catalyst for PEMWE. Recent studies demonstrated that RuO2 mixed with other metal oxides, such as IrO2 and SnO2 etc. showed higher activity and durability than pure RuO2 (1-3). When the RuO2 deposited on the other metal oxides, interfacial resistance and lattice strain which derives from the lattice mismatch should influence on the OER properties. In this study, to clarify the influence of interface between different rutile-type oxides, we fabricated RuO2/MO2/TiO2(110) (M = Ir or Sn) single crystal model catalyst and evaluated the oxygen evolution activity and durability. Experimental Nb-doped TiO2(110) (Nb: 1 wt%) single crystal substrate was etched in 20 % HF solution for 10 min and annealed at 1000 ℃ in air. After the sample transfer to the APD chamber, 2 nm-thick Ir or Sn was deposited onto the substrate at room temperature under 0.5 Pa-O2 partial pressure and annealed at 350 ℃ for 30 min under the same O2 pressure. After that, 4 nm-thick Ru was deposited on the MO2/TiO2(110) and was annealed under the same condition of the MO2 layer. Hereafter, the sample was denoted as RuO2/MO2/TiO2.Oxygen evolution activity was measured by linear sweep voltammetry (LSV) at a scan rate of 1 mV/s in N2-purged 0.1 M HClO4 at room temperature. The electrochemical impedance spectroscopy was conducted at 1.5 V vs. reversible hydrogen electrode (RHE) to measure the resistance of solution (Rs), electrodes (Re), and charge transfer for OER (Rct). The LSV curves were corrected using the measured Rs. Chronopotentiometry was conducted at 0.5 mA/cm2 for 120 min to evaluate the durability. In-plane XRD analysis was performed for estimating lattice strain in the surface RuO2 layer. Results and Discussions XRD analysis showed that both of the MO2 interlayer and RuO2 catalyst layer grow with (110) orientation on the TiO2(110) substrate. Figure 1(a) shows initial LSV curves for OER. The onset potential of RuO2/SnO2/TiO2 samples clearly shifted to lower potential side relative to the RuO2/IrO2/TiO2 and RuO2/TiO2 samples. The overpotential at 0.1 mA cm-2 of the RuO2/SnO2/TiO2 (b) was ca. 25 mV lower than the other two samples. The chronopotentiometric curves (c) showed the overpotential of RuO2/TiO2 increased by 250 mV after 120 min. On the other hand, change in the overpotential of the RuO2/SnO2/TiO2 was only 25 mV, indicating the high durability.Cole-cole plots at 1.5 V (d) revealed that both of the Re and Rct were significantly reduced owing to SnO2 interlayer, while the IrO2 layer slightly increased the Re and decreased the Rct. In-plane XRD results showed the compressive lattice strain was induced in [001] direction in RuO2 layer on TiO2 substrate and decreased by insertion of IrO2 and SnO2 layer. However, the lattice spacing in [-110] direction was almost the same for all the samples. Figure 1 (e) shows the relation between Rct and the lattice strain in [001] direction. The Rct tended to decrease with decreasing the compressive strains, suggesting the OER activity of RuO2(110) surface is related to the anisotropic strains in [001] direction. The results demonstrated that the activity and durability of RuO2/TiO2 catalysts can be improved by insertion of SnO2 layer at the catalyst/substrate interface.AcknowledgmentsThis study was partly supported by JSPS KAKENHI Grant Number 21H01661 and Toyota Mobility Foundation Hydrogen Initiative. References R. V. Genova-Koleva, F. Alcaide, G. Álvarez, P. L. Cabot, H.-J. Grande, M. V. Martínez-Huerta and O. Miguel, Journal of Energy Chemistry, 34, 227 (2019).J. Li, X. Qin, G. Chen and G. Chen, Journal of the Taiwan Institute of Chemical Engineers, 125, 186 (2021).R. Samanta, P. Panda, R. Mishra and S. Barman, Energy & Fuels, 36, 1015 (2022). Figure 1

Effect of phosphorus ion implantation on electrical conductivity and local lattice distortions in diamond

In this work, phosphorus ions have been implanted with various doses at an energy 100 keV on single crystal (100) diamond. We try to understand the local lattice distortions (disorder) induced in the implanted layer post annealing (at 850 °C) as a result of ion impact with the help of out-of-plane as well as in-plane XRD techniques and its corresponding effect on the electrical conductivity in diamond crystal. While a low dose of 1014cm−2 increases the lattice parameter along the out-of-plane direction and leads to formation of isolated point defects (mostly interstitials) in the lattice without introducing much disorder, a moderate dose of 1015cm−2 initiates the process of clustering of these defects in the implanted/defected layer. An out-of-plane tensile strain that is present in low dose case is eventually released with moderate dose implantations. With high doses of phosphorus in diamond, the crystallinity in the implanted layer drops, the damage propagates to the extent that it forms small amorphous pockets within this defected layer; although the lattice is not completely amorphous as it still retains the long range order as confirmed from X-ray absorption results. Our data indicate that the electrical transport in diamond is mainly due to substitutional phosphorus when implanted at low dose of 1014cm−2 and also highlights that damage or ‘localized amorphization’ takes place at a critical implantation dose of 1016cm−2 and therefore the critical phosphorus ion dose of 1015cm−2 (in 100 keV energy regime) i.e. a damage threshold of 8 × 1021vacancies/cm3 is the limit beyond which chances of amorphization is prevalent and the electronic properties in diamond are solely due to sp3 bond breakage.

Evaluation of Reduced Graphene Oxide Film Using In-Plane XRD Measurement

This work reports the synthesis of rGO using magnetron sputtering followed by the annealing process in argon. Raman mapping analysis helped confirm the existence of D, G and 2D band after annealing which indicating the formation of rGO and not a monolayer of graphene. Out of plane XRD measurement observed 21.5°, 30.1° and 35.5° corresponding to d-spacing and 0.412 nm, 0.296 nm and 0.253 nm respectively and for in plane XRD measurement are observed at are 2θ peaks at 30.1°, 35.5° and 62.4° corresponding to d-spacing 0.296 nm ,0.253 nm and 0.148 nm respectively. All the spectrum shows shifted due to the presence of defect in the deposited rGO structure. Thus, the in plane measurement are successfully demonstrated as an alternative method to evaluate the thin rGO film.

Highly Oriented Growth of AlxSc1-X N Ferroelectric Film on W Bottom Electrodes

Ferroelectric materials have been utilized for non-volatile memory applications [1]. Beside extensive works on ferroelectric HfO2 thin film [2, 3], recent works on nitride-based materials have proven that AlxSc1-xN (ASN) also shows ferroelectricity with a box-like characteristic [4]. A high remnant polarization of over 100 µC/cm2 is attractive for future non-volatile memory applications. However, the leakage current is still high for ASN thin films. Thus, a better-oriented growth method or an insulator is needed. The purpose of this study is to evaluate the impact of adding an AlN seed layer which also acts as an insulator for ASN thin film.ASN films, AlN films, and ASN films with 3nm AlN seed layer, three samples were fabricated in this research. A W layer was deposited on an n+Si substrate. Then, 50-nm-thick films of ASN and AlN films were deposited by DC reactive sputtering, respectively. For ASN films with a 3nm AlN seed layer, a W layer was deposited on an n+Si substrate. Then, 3-nm-thick AlN films were deposited by DC reactive sputtering. In the end, 50-nm-thick ASN films were deposited by DC reactive sputtering. All fabrication processes were kept constant at 400oC. XRD and XRC measurements were performed on these three samples. The source of the x-ray was CuKa with a divergence angle of 0.04o. The out-of-plane and in-plane XRD patterns of these three samples are shown in fig. 1(a) and (b), respectively. In out of plane XRD patterns, the (002) peak for the ASN sample is at 35.52 o, yielding parameter c = 0.505nm, which is slightly larger than the reported value of c = 0.4989 ± 0.0005nm [5]. On the other hand, in in-plane XRD patterns, the (100) peak for the AlN sample is at 33.07 o, yielding parameter a = 0.313nm, which is in perfect agreement with the reported value for pure AlN [6]. The (100) peak for the ASN sample is at 31.64 o, yielding parameter a = 0.327nm, which the composition of Sc x= 0.205 by following the reported Gaussian fitting [5]. However, the results didn't show any improvement in the oriented growth of adding the AlN seed layer. Further analyses such as JV, CV, and PV measurements are needed. XRC results of the AlScN (002) plane are shown in fig. 1(c). The results revealed a full-width half-maximum (FWHM) of 7.28o, 15.90o, and 16.17 for ASN, AlN, and ASN/AlN samples, respectively, indicating the oriented growth for these films. Moreover, the seven times higher intensity obtained with the ASN sample suggests a highly oriented film to (00l) plane.In conclusion, XRD and XRC results for ASN films, AlN films, and ASN films with a 3nm AlN seed layer were performed. The results for AlN films met the reported value for pure AlN. ASN grew highly oriented when directly deposited on W electrodes. Further measurements such as JV, CV, and PV are needed.

Metalorganic chemical vapor deposition of aluminum nitride on vertical surfaces

Metalorganic chemical vapor deposited (MOCVD) aluminum nitride (AlN) on vertical sidewalls can be used to implement piezoelectric in-plane actuation and sensing in microelectromechanical system (MEMS) sensors. The AlN films should optimally cover conformally the sidewalls and have good crystal quality with c-axis oriented microstructure for optimal piezoelectric properties. Previous MOCVD AlN research has focused on using AlN as a buffer layer for other III-nitrides and so far, AlN growth has not been studied on large vertical surfaces. In this study, AlN thin films were grown using MOCVD on vertical sidewalls of fabricated templates and the conformality and crystal quality was characterized. The growth template fabrication was optimized with respect to surface roughness, the conformal coverage was analyzed by measuring the thickness profiles of the films, and the crystal quality was investigated using in-plane XRD and TEM. The AlN films have good crystal quality (FWHM 1.70°–3.44°) and c-axis orientation on vertical Si(1 1 1) sidewalls. However, the thicknesses of the films reduce approximately at a rate of 0.8–1.2 nm/μm down the sidewall. Lowering the reactor pressure improved the conformal coverage while changing the growth mode from columnar to step-flow, which also improved the film morphology.

ORR Properties of Tensile-Strained Pt/Zr/Pt(111) Bimetallic Surfaces Prepared By Arc-Plasma Depositions of Pt and Zr on Pt (111)

Introduction Pt-based alloys with group 9 – 11 elements M (M = Fe, Co, Ni, etc.) are widely studied as cathode catalyst materials for the polymer electrolyte fuel cell (PEFC), because such the Pt-M alloys improves the oxygen reduction reaction (ORR) activity per unit area (area-specific activity) with reduction of Pt usage. However, the drawback of the Pt-M catalysts is easy elution of the M under the operating conditions of PEFC, i.e., low pH and severe potential fluctuations. Hurken et al. [1] investigated the electrochemical stability of Zr in acidic environments and showed that the formation of passive layers of Zr stabilizes the Zr surface. Therefore, in this study, ORR activity and structural stability are investigated for the Pt/Zr/Pt(111) bimetallic surfaces prepared through alternating depositions of Zr and Pt on the Pt(111) substrate by an arc-plasma deposition (APD) method. Experimental The bimetallic surface synthesis procedure is described elsewhere [2]. After the surface cleaning of the Pt (111) substrate in ultra-high vacuum (UHV; ~10-8 Pa), the alternating APDs of Zr and Pt were carried out on the surface cleaned Pt(111) to synthesize Pt/Zr/Pt(111) bimetallic surfaces; the deposition sequences of Pt and Zr are schematically shown in Fig. 1(a). The total thicknesses of Pt and Zr and the top Pt layer thickness were fixed to be 6.0 and 1.6 nm respectively. The second-layer Zr thicknesses were changed from 0.4 to 3.2 nm. The Pt/Zr/Pt(111) bimetallic surfaces thus synthesized were designated hereafter by the second-layer Zr thicknesses (m nm) as “m-nm-Zr”. After the surface structural analysis, e.g., cross-sectional STEM, XPS and in-plane XRD, the Pt/Zr/Pt(111) bimetallic surfaces were transported to an electrochemical three-electrode-cell without air exposure to avoid surface contamination and oxidation. Then, CV and LSV measurements were conducted in N2–purged and O2–saturated 0.1 M HClO4. The ORR activity was evaluated from jk values at 0.9 V vs. RHE by using Koutecky–Levich equation. The surface electrochemical stability was discussed on the basis of ORR activity changes during applying the 5000 potential cycles (PCs) of 0.6-1.0 V vs. RHE in O2–saturated solution at a room temperature. Results and Discussion In-plane XRD results revealed that tensile strain less than 0.8 % relative to Pt(111) worked on the Pt(111)-shell layers for the synthesized Pt/Zr/Pt(111) bimetallic surfaces. Cross-sectional STEM image of the 3.2 nm-Zr is shown in Fig. 1(b). The atomically-resolved image reveals that the Pt(111)-shell layer is epitaxially grown on the Pt-Zr(111) alloy layers. One might notice that a twin boundary (black dashed line), where the stacking sequence of (111) planes is changed from ABC to CBA, is located at 10-stacking layers of (111) from the top surface. Therefore, estimated tensile strains of the Pt/Zr/Pt(111) bimetallic surfaces (less than 0.8 %) are probably caused by such the twin boundary generation that might release the surface strains of the Pt(111)-shell. CVs of the synthesized Pt/Zr/Pt(111) bimetallic surfaces (Fig. 1(c)) show decrease in hydrogen adsorption charges (QH; around 0.05 to 0.35 V) as well as lower shifts of onset potentials of the hydrogen adsorption for all the surfaces, though the features are insensitive to the underlying Zr deposition thicknesses. Furthermore, positive-shifts of the onset potentials due to hydroxyl-related (OH) species adsorption (ca. 0.6 V) can be seen on the CVs, while “so-called” butterfly peaks for each bimetallic surfaces shifted only slightly relative to that of the clean Pt(111) (0.8 V). The ORR activity trends during applying the PCs are summarized in Fig. 1(d). The pristine activities are ca. 3 to 5 fold higher than the clean Pt (111): the 0.8nm-Zr sample surface shows the maximum enhancement factor of 5. Furthermore, except for the changes in very early stage of the PCs (100 cycles), the activities are remained nearly unchanged by the PCs application, indicating high electrochemical stabilities of the Pt/Zr/Pt(111) bimetallic surfaces. The results obtained in this study suggest that alloys of Pt with 4 – 6 group early transition metal elements, e.g., Zr, should be considered for effective cathode ORR catalysts of PEFC. Acknowledgement This study was supported by new energy and industrial technology development organization (NEDO) of Japan.

Oxygen Reduction Reaction Activity for Surface-Magnetic-Anisotropy-Controlled Pt-Co/Pt(111) Bimetallic Surface

Introduction Developments in effective oxygen reduction reaction (ORR) catalysts for the cathode of Polymer Electrolyte Fuel Cell is important to achieve “hydrogen society”. Because oxygen molecules (O2), the reactant of ORR, is paramagnetic having a triplet spin state, ORR that proceeds on the cathode catalyst surfaces might modify by magnetism of the catalyst materials. Indeed, ORR activity was improved by the influence of an external magnetic field applied to the catalyst [1]. The alloys of 3d transition magnetic elements M (M=Co, Fe, Ni) are known to exhibit ferromagnetism. Etz et al. reported that the direction of magnetization easy axis of the epitaxial Co/Pt(111) surface depends on the Co deposition thickness [2]. However, to our best knowledge, relation between the magnetic anisotropy of the cathode electrode surface and ORR activity is yet to be clarified. Therefore, to investigate influence of spontaneous magnetization of the material’s surface on the ORR should cast some light on the ORR activity enhancement mechanisms for such the Pt-M alloy surfaces with the magnetic. In this study, we fabricate Pt-Co/Pt(111) ferromagnetic bimetallic surfaces under ultra-high vacuum (UHV) through 1 monolayer(ML)-thick epitaxial growth of Co on the clean Pt(111) substrate at various temperatures and discuss the influence of magnetic anisotropy of the Pt-Co/Pt(111) bimetallic surface on corresponding ORR activity. Experimental The sample fabrication process of Pt-Co/Pt(111) bimetallic surface is as follows. After surface cleaning of the Pt(111) single crystal substrate through Ar+ sputtering and annealing at 1173 K in ultra-high vacuum (UHV: 10-8 Pa), 1ML-thick-Co was deposited on the clean Pt(111) by the molecular-beam epitaxy (MBE) method at elevated substrate temperature (723 K to 973 K) to generate the Pt(111)-skin through the surface segregation of substrate Pt atoms [3]. The Pt-Co/Pt(111) bimetallic surfaces are described hereafter by the Co deposition temperatures, for example Pt-Co773K/Pt(111), etc. The resulting surface structures were verified by the scanning tunneling microscopy (STM) and low-energy ion scattering spectroscopy (LE-ISS) in UHV. Then, polar magneto optical Kerr effect (polar MOKE), and in-plane XRD measurements are conducted in air to evaluate the surface magnetic anisotropies and compressive strains of the generated Pt(111)-skin surfaces. The MBE-prepared samples were transferred to electrochemical evaluation systems set in a N2–purged glove box without being exposed to air. Then, cyclic voltammetry (CV) and linear sweep voltammetry (LSV) measurements were conducted in N2–purged and O2–saturated 0.1 M HClO4, respectively, in the glove box. ORR activities of the samples were evaluated based on j k values at 0.9 V vs. RHE by using Koutecky–Levich equation. Results and Discussion An LE-ISS spectrum of the Pt-Co773K/Pt(111) is shown in Fig. 1(a). Only the signal due to of the Pt atoms at the topmost surface is appeared on the spectrum, indicating that the Pt(111)-skin is generated for the Pt-Co773K/Pt(111) surface and the deposited Co should be located below the second atomic layer of the Pt-Co773K/Pt(111) as a result of surface segregation of the substrate Pt atoms at deposition temperature (of 773 K). Fig. 1(b) shows an STM image of the corresponding Pt-Co773K/Pt(111) surface. As shown in Fig. 1(b), the sample surface is atomically flat. One might notice that Moiré-pattern-like surface corrugations on the image (highlighted by white line), probably stemming from the lattice mismatch between Pt(111)-skin and underlying Co (Pt-Co alloy) [4]. The result also supports the Pt(111)-skin. Fig. 1(c) shows the polar MOKE curves of the Pt-Co773K/Pt(111) (red) and Pt-Co823K/Pt(111) (blue). Both the samples show the hysteresis loops of Kerr rotation angle vs. magnetic field H, indicating that perpendicular magnetic anisotropy (PMA) of the sample surfaces. Relation between the ORR activities and in-plane-XRD-estimated compressive strains of the Pt-Co773K/Pt(111) (red) and Pt-Co873K/Pt(111) (blue) surfaces are shown in Fig. 1(d). For comparison, the DFT-calculated ORR activities of the strained Pt(111) surfaces (green) are plotted in the figure [5]. The estimated ORR activities for both the Pt-Co773K/Pt(111) and Pt-Co873K/Pt(111) are 20 to 30 % higher than the DFT-calculated ones. The results suggest that PMA might affect ORR activity enhancements for the prepared PMA surfaces of the Pt-Co/Pt(111). At the meeting, effects of magnetic anisotropies (perpendicular and in-plane) are discussed more in detail.

Rapid-throughput solution-based production of wafer-scale 2D MoS2

Two-dimensional semiconductors, such as MoS2, are leading candidates for the production of next-generation optoelectronic devices such as ultrathin photodetectors and photovoltaics. However, the commercial application of 2D semiconductors is hindered by growth techniques requiring hours of heating and cooling cycles to produce large-area 2D materials. We present here a growth technique that leverages high-intensity optical irradiation of a solution-processed (NH4)2MoS4 precursor to synthesize MoS2 in one-tenth the time of typical furnace-based CVD. From start to finish, the technique produces uniform 2D MoS2 across 4-in. wafers within 15 min. Raman spectroscopy, in-plane XRD, and XPS show a 2H MoS2 crystal structure with a stoichiometry of 1.8:1 S:Mo. AFM scans show that the films are 2.0 nm thick MoS2 with a roughness of 0.68 nm. Photoluminescence spectroscopy reveals the characteristic 1.85 eV bandgap. The as-grown films were used to make field-effect transistors with a mobility of 0.022 cm2 V−1 s−1 and photodetectors with a responsivity of 300 mA/W and an external quantum efficiency of 0.016%, demonstrating their potential for optoelectronic device development. This rapid thermal processing growth technique reduces MoS2 synthesis time by an order of magnitude relative to comparable techniques and enables greater accessibility to 2D semiconductors for researchers and developers.

Significant Structural Distortion in the Surface Region of 4H-SiC Induced by Thermal Oxidation and Recovered by Ar Annealing

The impacts of O2-oxidation and Ar-annealing processes on the local lattice distortion at surface of thermally-oxidized 4H-SiC (0001) were investigated by using in-plane XRD. The surface oxidation induces a significant increase of the lattice constant, whereas Ar-annealing results in a gradual relaxation of it. From the x-ray penetration depth dependence of the observed lattice constant, those anomalous changes of lattice constants occur only in the surface region of SiC substrate.

Monocrystalline Si Thin Film for Solar Cells Grown on Double Layer Porous Si Treated By Zone Heating Recrystallization

The recent development in monocrystalline Si solar cell technology is significant both for reducing the cost and for developing the power generation efficiency. The reduction of Si thickness is one of the key to achieve the further cost reduction. Bottom up technics such as epitaxy and layer transfer process is promising approach to get less than 50 µm-thick Si thin film. Si layer is deposited epitaxially on a seed monocrystalline wafer with a thin sacrificial layer, and then an epitaxial thin film is detached from the seed layer (Fig. 1). This process on double layer porous Si (DLPS), a top low porosity seed layer and a bottom high porosity sacrificial layer, have been widely studied, but there are two challenging issues to be solved. One is the long process time of epitaxy by chemical vapor deposition and another is the quality of the epitaxial film. Rapid vapor deposition (RVD) have been realized to grow epitaxial Si layer at ~10 µm/min deposition rate by the evaporation of Si source with >2000 °C [1]. On the other hand, the crystallographic quality of epitaxial film will depend on the roughness of the seed layer because such roughness will make lattice mismatch during the crystal growth. The effect of the surface roughness is supposed to be larger when the film growth rate get bigger, so to control the roughness become more important to obtain the high quality Si thin film with high speed, low cost process such as RVD. We have developed the zone-heating recrystallization (ZHR) method, the high-speed scanning lamp heating below the melting point of Si, for the selective heat treatment of the Si surface (Fig. 2) [2]. By applying ZHR to the epitaxy and layer transfer process on DLPS by RVD, we obtained the 9 µm-thick monocrystalline Si thin film with only 1-min epitaxy [3]. In this work, we controlled nanometer-size roughness of DLPS surface by ZHR and investigated the properties of Si thin film grown with RVD. To investigate the quality of thin film Si by both XRD and electron spin resonance (ESR), RVD were carried out with intrinsic Si wafer as Si source to avoid the signal of electron from the dopant. ~9 µm intrinsic Si thin films were grown and they could be easily detached by transferring to scotch tape. The Si films with different root mean square roughness (Rms), pore size and pore number density which were grown on DLPS with/without ZHR in several condition were picked up and analyzed. DLPS were formed on p-type monocrystalline Si (100) wafer by two-step anodization. ZHR were carried out with different input power into bottom heater and scanning rate of top lamp heater, and DLPS with different Rms (0.23-0.39 nm) observed by AFM were obtained as described in the previous report [3]. In Si film grown by RVD on the DLPS by each ZHR condition, in-plane XRD Φ-scan of (022) diffraction showed clear four fold symmetry, which proves that the epitaxial monocrystalline film of Si(100) obtained regardless of ZHR conditions. The effect of the surface roughness of DLPS on the crystallographic quality of epitaxial Si films will be discussed. In summary, the epitaxial monocrystalline film by RVD was obtained by the selective heat treatment of Si surface of DLPS by ZHR. The intrinsic monocrystalline film with 9 µm by RVD on DLPS could be easily detached from Si wafer to evaluate crystallographic quality by ESR. [1] Y. Yamasaki et al., CrystEngComm 18, 2016. 3404. [2] A. Lukianov et al., Appl. Phys. Lett. 108, 2016, 1. [3] C. Takazawa et al., ECS Trans. 75, 2017, 11. Figure 1

Si(001)基板上のβ-FeSi2(100)ナノカーペットの面内XRD測定による歪み評価

Si(001)基板上のβ-FeSi2(100)ナノカーペットの面内XRD測定による歪み評価

Formation of Ge quantum dots on Si substrate using consecutive deposition of Ge/C and in situ post annealing

Effects of intermediate carbon between amorphous Ge and Si surface on formation of Ge dots recrystallized through post-annealing were studied. The samples were prepared by solid-source molecular beam epitaxy system with electron beam gun for C sublimation and K-cell for Ge evaporation. C and Ge were deposited sequentially at 200°C and Ge/C/Si was subsequently annealed in MBE chamber. Ge dots were formed at annealing temperature (TA) of 400°C for Ge(1nm)/C(0.25ML)/Si. The dot size increased with TA, and both Ge(220) peak intensity measured by in-plane XRD and dot density were the highest at TA of 700°C. A strong correlation between dot density and surface roughness indicated recrystallization of Ge occurred during the dot formation promoted by Si–C bonds. Concerning the effect of C coverage, there was an optimum at 0.25ML which gave good crystallinity of Ge dots. Coalesced dots with bad crystallinity were observed for less or more C coverage. This was considered that dot formation combined with S–K growth mode due to large bare Si surface occurred at small C coverage and excess C incorporated into Ge dots at large C coverage. In terms of Ge thickness, there was also an optimum at 1nm to provide sufficient Ge atoms without excess.

Assembly of Surface-Confined Homochiral Helicates: Chiral Discrimination of DOPA and Unidirectional Charge Transfer

Surface-confined double-helical polymers are generated by dynamic covalent assembly with preservation of chirality, metal coordination environment, and oxidation state of the precursor complexes. This one-step procedure involves both in solution and solution-to-surface assembly and resulted in chiral interfaces where pairs of ligands are wrapped around arrays of metal ions. In-plane XRD experiments revealed the formation of a highly ordered structure along the substrate surface. The chirality of the surfaces is expressed by the selective recognition of 3,4-dihydroxyphenylalanine (DOPA). The CD measurements show a response of the Δ-polymer-modified quartz substrates toward D-DOPA, whereas no change was observed after treatment with L-DOPA. These coordination-based interfaces assembled on metal-oxide substrates in combination with a redox-probe, [Os(bpy)3](PF6)2, in solution can resemble the behavior of a rectifier.

Fabrication of Ordered Poly[1,6-bis(3-nonyl-9-carbazolyl)-2,4-hexadiyne] Thin Film via Simple Spin-coating Process

Abstract Diacetylene derivative, 1,6-bis(3-nonyl-9-carbazolyl)-2,4-hexadiyne was designed and synthesized. Compared with nonsubstituted 1,6-di(N-carbazolyl)-2,4-hexadiyne, the solubility was drastically improved, which allowed us the fabrication of a smooth crystalline thin film via a simple spin-coating process. The resulting film was easily polymerized by photoirradiation after thermal annealing. UV–vis absorption and Raman scattering spectra suggested topochemical polymerization. Out-of-plane XRD measurement of spin-coated film showed a strong diffraction. It suggests the interdigitation structure of alkyl chain. In-plane XRD measurements of spin-coated polymerized films showed two small peaks which were not identical to the result of out-of-plane XRD. These results indicated edge-on orientation. AFM image suggests that the film is composed of an aggregation consisting of needle-like nanostructures of polymer crystals.

High Resolution X-Ray Diffraction Analyses of (La,Sr)MnO<sub>3</sub>/ZnO/Sapphire(0001) Double Heteroepitaxial Films

The epitaxial relationships of lattices and crystalline qualities of LSMO/ZnO/sapphire double-hetero systems were thoroughly analyzed using X-ray diffraction techniques with a modern high resolution XRD system. It was revealed that the epitaxial growth of the LSMO (110) phase was promoted under higher temperature accompanying the suppression of other competitive growth of the LSMO (001) and (111) phases. Supplying the plasma oxygen accelerated the suppression of the LSMO (111) phase. The complex epitaxial orientational relationships in these three growth modes were revealed from the precise analyses with the high resolution out-of-plane XRD and the in-plane XRD measurements, pole figure measurements, and reciprocal space mappings measurements, as [112ˉ](111)LSMO//[11ˉ00](0001)ZnO//[112ˉ0](0001)Sap, [110ˉ](111LSMO)//[11ˉ00](0001)Zno//[112ˉ0](0001)Sap, and [110](001)LSMO//[11ˉ00](0001)Zno//[112ˉ0](0001)Sap. The validity of this model for the epitaxial orientational relationships in LSMO/ZnO/sapphire double heteroepitaxial layers was confirmed identically with the data ana- lyses of the out-of-plane wide-range Reciprocal Space Mapping using the 2-dimensional X-ray detector.

Fabrication of Graphene-based Electrodes for Supercapacitors in Magnetic Fields

Abstract Graphene-based electrodes have been fabricated in 1 and 2 T perpendicular and parallel magnetic fields, respectively. By out-of-plane and in-plane XRD analyses, it could be found that in perpendicular magnetic fields, graphene sheets are induced to align perpendicular to the mesh and that the arrangement makes more edge planes exposed to the surface. N2 adsorption–desorption measurements show that the perpendicular arrangement brings about an increase in surface area and pore size. More important is that the electrochemical performance, such as specific capacitance, cycle stability, and impedance of electrodes, improves as a result of the perpendicular arrangement. However, parallel magnetic fields lead to a decrease in the electrochemical performance and surface properties because of the parallel arrangement of graphene sheets.

The influence of pressure on the growth of a-plane GaN on r-plane sapphire substrates by MOCVD

Nonpolar a-plane (1\( \bar 2 \)0) GaN films have been grown on r-plane (1\( \bar 1 \)02) sapphire by metal-organic chemical vapor deposition (MOCVD) under different growth pressures. The as-grown films are investigated by optical microscopy, high-resolution X-ray diffraction (HRXRD) and Raman scattering. As growth pressure rises from 100 mbar to 400 mbar, the surface gets rougher, and the in-plane XRD full width at half maximum (FWHM) along the c-axis [0001] increases while that along the m-axis [\( \bar 1 \)100] decreases. Meanwhile, residential stresses are reduced along both the c-axis and the m-axis. The structural anisotropy feature under 400 mbar is inverted with respect to 100 mbar, and the weakened anisotropy is achieved under a moderate pressure of 200 mbar, probably due to the suppressed Ga atomic migration along the c-axis under a larger pressure. We propose that pressure can affect a-plane growth through the V/III ratio.

Fabrication of Mixed Monolayer of Biodegradable Polymers and Organo-modified Montmorillonite

We investigated formation of ultrathin hybrid films composed of a biodegradable polymers (ex. poly(ethylene succinate), poly(L-lactide), and poly(e-caprolactone)) and organo-modified montmorillonite nanosheet at an air/water interface. When a chloroform solution of the biodegradable polymer was spread onto a surface of an pure water in a Langmuir trough, a mixed monolayer of biodegradable polymer was formed by hybridization with the clay nanosheets at the air/water interface. These results indicated that some ammonium cations spread onto the clay suspension were dissolved into the aqueous subphase before the hybridization with the clay nanosheets. The hybrid monolayers were transferred onto a mica substrate by Langmuir-Blodgett method to form a mixed monolayer. Interestingly, the densities of dimethyl dioctadecyl (DMDO) ammonium determined by the thermogravimetric analysis were constant in the hybrid multilayers prepared from the clay suspensions at the same concentration, regardless of the concentrations of the amphiphilic ammonium salt solutions. Out-of plane and in-plane XRD profiles of the films showed that the cations of DMDO would lie down on the clay layer in the hybrid film.