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We report the fabrication of highly crystalline, large-grained organic-inorganic perovskite [CH(NH2)2]0.8Cs0.2PbI3 thin films on TiO2 layers by a one-step method using 1-Cyclohexyl-2-pyrrolidone and thiosemicarbazide as additives without using an antisolvent. The perovskite thin films have no pinhole, grain size of micrometer order, and high crystallinity, with a crystallite size greater than 200 nm. An n-i-p structured [CH(NH2)2]0.8Cs0.2PbI3 thin film solar cell exhibits power conversion efficiencies of 17.8% and 13.8% during reverse and forward scanning, respectively.

Onion (Allium cepa L.) produces a fructose-based oligosaccharide (fructan) in the bulb as the major reserve carbohydrate. We previously found varietal differences in fructan quantity in the harvested bulbs; ‘Kita-momiji 2000’ accumulated a high level of fructans with a high degree of polymerization, while ‘Pole Star’ had low amounts and accumulated mainly monosaccharides and sucrose. In this study, we examined fructan accumulation and enzymatic activities involved in the fructan metabolic pathway in more detail in both aerial and subterranean tissues that were harvested throughout onion development. Analyses of fructan levels in the two cultivars revealed that levels in fructan accumulation were almost the same in aerial and basal leaves before bulb formation, but fructan levels differed significantly in the late stage after bulb formation; varietal differences in fructan content in the harvested bulb were apparent only during the 2 or 3 weeks before harvest. At an early developmental stage, fructan levels in ‘Pole Star’ were equivalent to those in ‘Kita-momiji 2000’, indicating that ‘Pole Star’ can synthesize highly polymerized fructans. In analyses of enzymatic activities, ‘Pole Star’ had high activity for synthesizing fructan after bulb formation compared to ‘Kita-momiji 2000’ and also greater potential for degrading sucrose and fructan before bulb formation, leading to less sucrose accumulation both in aerial and basal leaves. These results suggest that high activities for fructan degradation enzymes in ‘Pole Star’ cause less fructan accumulation in the bulb than in ‘Kita-Momiji 2000’ because this cultivar cannot sustain high levels of sucrose, the starting substrate for fructan synthesis.

The dichlorogallyliron complexes Cp’(OC)2FeGaCl2 (Cp’ = Cp* (4a), Cp (4b), Cp*: η5-C5Me5, Cp: η5-C5H5), when treated with LiPPh2 and/or Me3SiPPh2 in Et2O, produce the four-membered Ga2P2 cyclic diiron complexes [Cp’(OC)2FeGa(Cl)PPh2]2 (Cp’ = Cp* (5a), Cp (5b)) in 64% and 47% yields, respectively. Crystal structure analysis using X-ray crystallography revealed that the four-membered Ga2P2 cyclic structure in cis-5a is slightly puckered. The four-membered Ga2P2 cyclic structure remains undisturbed in a solution of complex 5a in C6D6 and C7D8. 5a exists as a mixture of the cis/trans geometric isomers in these solutions. The photochemical reaction with complex 5b in C6D6 produces a complex mixture. However, the photochemical reaction with complex 5a in C6D6 afforded the six-membered Fe-Ga-Fe-P-Ga-P cyclic diiron complex [{Cp*(OC)Fe}2(μ-Ga)(μ-Ph2PGaCl2PPh2)] (6a) in 61% yield (NMR yield). Crystal structure analysis revealed that complex 6a contains the Ga atom-bridged Fe-Ga-Fe fragment with two Fe−Ga multiple bonds.

Volatile, CH3NH3+-free, [CH(NH2)2]0.9Cs0.1PbI3 organic-inorganic perovskite thin films were treated with fluorinated ammonium iodide {4-fluoro-phenethylammonium iodide (4F-PEAI)} solution and thin two-dimensional (4F-PEA)2PbI4 films were formed on the surface, resulting in a significant improvement in photoluminescence intensity. When applied to low-temperature-processed PSCs with planar structure, untreated PSCs exhibited PCEs of 18.6% and 17.0% during reverse and forward scanning, respectively. The PSCs treated with 4F-PEAI showed improved open-circuit voltage, fill factor, and PCEs of 20.6% and 18.5% during reverse and forward scanning, respectively.

We firstly investigated efficient poly(3,4-ethylenedioxythiophene): poly(styrenesulfonic acid) (PEDOT:PSS)/n-type polycrystalline silicon (p-Si) heterojunction solar cells fabricated by chemical mist deposition (CMD) using a high-pressure H 2 O-vapor-treated p-Si prior to organic film deposition. High-pressure H 2 O vapor treatment of the p-Si efficiently suppressed grain boundary defects and improved carrier transport at the PEDOT:PSS/p-Si interface. Furthermore, compared to spin coated devices, the CMD devices demonstrated a more uniform photovoltaic performance. The power conversion efficiency of the PEDOT:PSS/p-Si heterojunction solar cells was 9.7% with a short-circuit current density of 33.5 mA/cm 2 , an open-circuit voltage of 0.54 V, and a fill factor of 0.53. These findings suggest that CMD with a negatively charged mist precursor provides uniform adhesion of PEDOT:PSS on p-Si, resulting in increased photovoltaic performance.

We prepare transparent, self-assembled polygonal silver nanowire (AgNW) mesh by bubble template and transferred as top electrode in poly(3,4-ethylenedioxythiophene):poly(stylenesulfonate) (PEDOT:PSS)/n-silicon hybrid solar cell, which shows power conversion efficiency of 10.62% under 100 mW/cm 2 of AM 1.5G illuminations. The self-assembled AgNW mesh electrode exhibited a low sheet resistance (50 Ω/square) with high transmittance (87%) at a wavelength of 550 nm. In self-assembled AgNW mesh, AgNWs are well packed making continuous path for charge collection and transportation. Nevertheless, studies have also been carried out to transfer AgNWs from donor (glass or plastic) to receiver substrates (thermal release tape) and an expected reason for the transfer of AgNWs from thermal release tape to the top of PEDOT:PSS has also been proposed.

Hydroaroylation of methyl acrylate 2a to give the α-aroyl esters 4 took place in the three-component reaction of 2a , aroyl chlorides 1 , and Et 2 MeSiH in the presence of 1 mol % of [Rh(cod)(PR 3 ) 2 ]OTf (cod = 1,5-cyclooctadiene, OTf = OSO 2 CF 3 , R = Ph ( 3a ), OPh ( 3b )) in CH 2 Cl 2 . GC and 1 H NMR investigation revealed that the rhodium-catalyzed hydroaroylation proceeds via two successive transformations, that is, hydrosilylation of 2a to afford silyl enol ether 5a followed by C–C bond formation between 5a and 1a .

The initial growth stage of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films by the electrospray deposition (ESD) method was investigated using 70% N , N -dimethylformamide (DMF) as a solvent solution through the real-time spectroscopic ellipsometric (SE) characterization. The uniaxial anisotropic optical property was prominent for the film growth on c-Si wafer, whereas the homogeneous growth occurred with random molecular orientation on indium-tin-oxide (ITO) coated glass. These findings probably originate from a preferential orientation of the polymer chains as obtained in the preparation process, sort of substrate, its morphology, and film thickness.

Depth profiles of the optical constants, carrier mobility, and carrier density of spin-coated 3,4-polyethylenedioxythiophene:polystyrenesulfonic acid (PEDOT:PSS) films were investigated by real-time characterization by the spectroscopic ellipsometry (SE) during argon plasma etching at atmospheric pressure. Spectral analysis revealed that homogeneous etching occurred within 10–15 nm of the top surface, followed by the appearance of a conductive PEDOT phase and surface roughning, which originated from the depth profile of the PEDOT-to-PSS molar concentration ratio. The use of the plasma-etched PEDOT:PSS layer improved relatively the performance of the copper phtalocyanine (CuPc)/C60 organic thin-films solar cells as a hole-transport layer with higher optical transmittance by adjusting the plasma etching condition.

The gallane-Lewis base adduct H 3 Ga·L is employed as a σ-Ga–H ligand for the group 6 carbonyl metal complexes (OC) 5 M(H 3 Ga·L) (M = Cr, Mo, W) and the manganese complex Cp*(OC) 2 Mn(H 3 Ga·L). Group 6 carbonyl metal derivatives (OC) 5 M(H 3 Ga·L) are synthesized by the reaction of (OC) 5 M(THF) and H 3 Ga·L. The photochemical reaction of Cp*(OC) 3 Mn and H 3 Ga·L affords the gallane manganese σ-complex Cp*(OC) 2 Mn(H 3 Ga·L). The structural properties of these complexes can be understood in terms of the coordination mode of σ-Ga–H bond to (OC) 5 M and Cp*(OC) 2 Mn fragments being depicted as η 1 -HGaH 2 ·L and η 2 -HGaH 2 ·L, respectively. The contribution of σ-donation from the Ga–H σ-bond to d σ orbital on M occurs in both systems, however, the participation of π-back donation from filled d π orbital to Ga–H σ* orbital is negligible for the (OC) 5 M(H 3 Ga·L) complexes but important for Cp*(OC) 2 Mn(H 3 Ga·L) complex. Such distinctive characteristics of the σ-H 3 Ga·L ligand provides a sharp contrast to that of H 3 B·L and silane ligands.

We studied the effect of the substrate materials on the solution-mediated vacuum deposition of organic semiconductor rubrene using liquid flux with a low vapor pressure. We found that bis-2-ethylhexyl phthalate was suitable as the liquid flux. It was revealed that the microscopic crystal shape completely changed when different substrates were used. This result clearly indicates the nucleation of the crystals occurs on the substrate surface submerged in the solution. Epitaxially oriented needle crystals as long as 5 mm were obtained by using Au(1 1 1) substrate.

A dinuclear complex bridged by a substituent-free gallium atom, Cp∗(dmpe)Fe–Ga–Fe(CO)4 (1b: Cp∗ = η-C5Me5, dmpe = Me2PCH2CH2PMe2), was synthesized by the reaction of Cp∗Fe(dmpe)GaCl2 with K2[Fe(CO)4]. Crystal structure analysis of complex 1b showed that the geometry around the gallium atom is essentially linear and the two Fe–Ga bonds are significantly shorter than those of usual single bonds, indicating the multiple bonding character of the Fe–Ga bonds. Comparison of the structure and IR data of 1b and those of Cp∗(dppe)Fe–Ga–Fe(CO)4 (1a: dppe = Ph2PCH2CH2PPh2) revealed that the Fe–Ga bond is sensitive to the electronic character of the metal fragment. The Fe–Ga bond is shortened upon introducing a more π-basic metal fragment.

Tetra- and penta-fructooligosaccharide (FOS) isomers and their hydrolysis parameters––% hydrolysis, hydrolysis rate constant ( k obs ) and half-lifes ( t 1/2 ) in onion bulb tissues kept for 6 months at 10, 15, and 20 °C, were investigated. The hydrolysis of the tetra- and pentaFOS isomers ranged between 67% and 86% and isomers of b type 4b and 5b were hydrolyzed preferentially. The k obs showed large variation from 51 × 10 −3 week −1 (lowest value) to 82 × 10 −3 week −1 (highest value), while the half-life t 1/2 of the isomers ranged between 8.5 and 16.6 weeks. DP 4 content showed close correlation at 15 and 20 °C but different at 10 °C. At 10 °C, DP 4 isomers decreased sharply during the first 2 months but remained stable during the last 4 months. At 15 and 20 °C, DP 4 increased slightly within the first month, and then decreased during the second month. During the last 4 months, the 4a isomer remained stable, while 4b and 4c increased slightly. PentaFOS isomers varied in a similar fashion to tetraFOS isomers. At 10 °C, DP 5 isomers decreased sharply during the first 2 months and remained stable during the last 4 months except for a slight increase observed during month 3 for 5b and 5c + 5d . At 15 and 20 °C, they showed a similar pattern to those of the tetra-isomers. It was concluded that pentaFOS isomers are preferentially hydrolyzed with respect to tetraFOS isomers, because they have a relatively high content of fructosyl ends chain. Results also allow us to distinguish that the DP x b (type b) isomers are preferentially hydrolyzed.

Methyl-terminated Si(1 1 1) (Me–Si(1 1 1)) and bilayer-GaSe terminated Si (BGS) surfaces were investigated to explore their usefulness as the protection layer in the fabrication process of nanometer-scale self-assembled monolayers (SAMs). BGS was not stable in the reagent involved in the alkyl SAM formation, whereas Me–Si(1 1 1) was suitable for the protection layer. Anodization using atomic force microscope (AFM) and following HF and hexadecene treatments were performed to form nano-scale alkyl SAM lines on the Me–Si(1 1 1) surface. It was found from AFM observation and frictional force measurement that only the patterned areas were selectively covered with hexadecyl SAMs.

CsCl has been known to show extraordinary photoemission by visible (VIS) light only after ultraviolet (UV) light irradiation. To elucidate this phenomenon, photo yield and photoemission spectrum of a single-crystalline CsCl thin film were measured in ultrahigh vacuum. Photo yield measurements confirmed that photoelectrons were emitted from F-centers induced in the CsCl thin film by preceding UV irradiation. Absence of the similar phenomenon in the NaCl film indicated that VIS photoemission in alkali halides was caused not only by defect formation but also by negative electron affinity.

As a stable and 'epitaxial' passivation of a Si surface, we propose the bilayer-GaSe termination of a Si(111) surface. This surface is fabricated by depositing one monolayer of Ga on a clean Si(111) surface and subsequent annealing in a Se flux at around 520 degreesC, which results in unreconstructed 1 x 1 termination of the Si(111) surface by bilayer-GaSe. We found by scanning tunneling microscopy observation that slow cooling of the clean Si(111) surface from 850 to 520 degreesC with simultaneous deposition of a Ga flux results in better termination of the Si(111) surface. It was also found that this surface is stable against heating around 400 degreesC in O-2 atmosphere of 3 x 10(-3) Pa. By utilizing these properties of the bilayer-GaSe terminated surface, we have succeeded in fabricating ZnO quantum dots on this substrate. (C) 2002 Elsevier Science B.V. All rights reserved.

The anionic ruthenium and iron complexes Li[(η5-C5Me5)M(CO)2] (M=Ru (1-Ru), Fe (1-Fe)) were generated by deprotonation of the transition metal hydride (η5-C5Me5)M(CO)2H with n-BuLi in tetrahydrofuran (THF). The reaction proceeded at −45 °C immediately. Reactions of 1 with various electrophiles (Me3SiCl, pTol2HSiCl, Me2SiCl2, MeSiCl3, SiCl4, Me3SiSiMe2Cl, and Ph2GeCl2) afforded the corresponding nucleophilic substitution products (η5-C5Me5)M(CO)2ER3 (E=Si, Ge) via salt-elimination.

The characteristics of interaction between C 60 molecules and Si(1 1 1)-7×7, Ag/Si(1 1 1)-√3×√3 R 30° and layered material MoS 2 surfaces have been investigated using electron-energy-loss spectroscopy (EELS). The EEL spectrum of C 60 /Si(1 1 1)-7×7 shows a new peak at loss energy of 2.7 eV. This indicates the existence of charge transfer from the substrate to C 60 molecules. The EEL spectrum of a C 60 monolayer film grown on a cleaved surface of MoS 2 is almost the same as that of bulk C 60 . The EEL spectrum of a C 60 monolayer film on an Ag/Si(1 1 1) surface is quite different from that on a clean Si(1 1 1)-7×7 surface, although the films on those substrates have the same epitaxial arrangement. Furthermore, intensities of energy-loss peaks of C 60 /Ag/Si(1 1 1) are slightly smaller than those of C 60 /MoS 2 in spite of having the same loss-energy. This suggests that the interaction between C 60 molecules and the Ag/Si(1 1 1) surface is stronger than that between C 60 molecules and the MoS 2 surface.

Sub-monolayer films of layered semiconductor InSe were grown on MoS2 substrates by molecular beam epitaxy, and the change in their growth features with Se/In flux ratio was investigated using scanning tunneling microscope in vacuum. It was found that InSe domains grown at 340 degrees C have a hexagonal shape when the Se/In ratio is about 17. Detailed images of the hexagonal InSe domains have revealed that adjacent sides of the hexagon have different structures; one is a straight edge and the other is a disordered edge. When the Se/In ratio was decreased, the disordered edges became predominant, the straight edges disappeared, and the InSe domain became triangular. On the contrary, when the Se/In ratio was increased, InSe domains became triangular ones consisting of only straight edges. The growth mechanism of InSe domains is discussed by considering the crystal structure of InSe and the reactivity of each side with incoming atoms. It is suggested that the balance of incorporation rate of In and Se atoms determines the structure of InSe domains. (C) 2000 Elsevier Science B.V. All rights reserved.

Single crystalline Ga 2 Se 3 thin films were grown on GaAs(1 0 0) by molecular beam epitaxial (MBE) under Se-rich atmosphere. Reflection high-energy electron diffraction (RHEED) analysis suggests that the Ga 2 Se 3 thin film is epitaxially grown on GaAs(1 0 0) with their 〈1 0 0〉 crystallographic directions aligned with each other. The electronic structure determined by the ultraviolet photoelectron spectroscopy (UPS) and electron energy loss spectroscopy (EELS) revealed the forbidden band gap of 2.7 eV. Transmission electron microscopy has shown that vacancies are distributed on one set of {1 1 1} crystal planes of α-Ga 2 Se 3 structure by forming a 3 × 3 configuration, resulting in the three times larger modulation periodicity along one of the 〈1 1 0〉 crystal directions into vacancy ordered β-Ga 2 Se 3 structure. The crystal structure was consistent to a model proposed by Lubbers and Leute (J. Solid State Chem. 43 (1982) 339). There are two sets of planar defects, microtwin with {1 1 1} type twin planes and stacking faults. High population of planer defects observed in the thin film was regarded as a result of Ga vacancy ordering in the crystal structure of Ga 2 Se 3 .

C-60 molecules were deposited on a submonolayer InSe film which was grown on a MoS2 substrate. In the previous experiment on the growth of a C-60 thin film on a GaSe/MoS2 heterostructure, C-60 grew only on exposed MoS2 regions and never nucleated on GaSe domains at substrate temperature above 180 degrees C. In the present case, however, C-60 molecules grow only on InSe domains and do not nucleate on the exposed MoS2 when the substrate temperature is higher than 80 degrees C. Using this method, C-60 domains whose dimension is smaller than 100 nm could be fabricated on each InSe domain. The selectivity of the C-60 growth is supposed to originate not from the surface morphology of those heterostructures, but from the difference in adsorption energy and surface diffusion energy of C-60 molecules on the surfaces of three different layered materials and a C-60 film. (C) 1998 Elsevier Science B.V. All rights reserved.

The lattice mismatch at the heterostructure CdS/Si(111) is close to 8%. To relieve the structural stress at this interface, an InSe van der Waals-type buffer layer was grown between the Si substrate and the CdS film. After the Si(111) substrate surface was passivated by hydrogen, the InSe-buffer layer was grown on top by molecular beam epitaxy with high crystalline quality. The lattice orientations of the InSe film are in registry with the Si substrate, as shown by reflection high energy electron diffraction. As seen in the atomic force microscope, the InSe films have roughly the same terrace width of 50–70 nm as the Si substrate due to the wafer miscut. By contrast the step edges of the InSe film are more regular than those of the silicon. The CdS-film was grown on the InSe. The crystal axis of the film is in full registry with the InSe substrate as monitored by reflection high energy electron diffraction. The film morphology is determined as simultaneous growth of multilayers observed by atomic force microscope.

NH 4 F treatment of a Si(111) substrate gives a very flat and chemically inactive surface because of the regular termination of each active dangling bond by a hydrogen atom. On this inactive surface, layered semiconductor GaSe and molecular crystal C 60 grow through weak Van der Waals interaction. As a result their epitaxial films can be grown with their own lattice structures in spite of the large difference in their lattice constants from the substrate. Atomic force microscope (AFM) analysis of the GaSe thin film revealed many triangular spiral structures, indicating screw dislocation growth mechanism. In contrast, AFM observation of the C 60 film showed that it grows in the island growth mode, and each island has a two-dimensional dendritic shape.

29Si NMR coupling constants in a disilanyliron complex CpFe(CO)2SiMe2SiMe(OtBu)2 (1: CP = η5C5H5), a bis(silylene)iron complex Cp(OC)Fe{SiMe2 ⋯ O(tBu) ⋯ SiMeOtBu)} (2), and a cis-bis(silyl)iron complex (OC)4Fe{SiMe2CH2CH2SiMePh} (3) were measured by the INEPT-INADE-QUATE technique. The coupling constant for 2 (28.6 Hz) is much smaller than that for 1 (128 Hz) with a direct Si-Si bond, but larger than that for 3 (2.7 Hz) where there is no direct Si-Si bond. Model calculations using the extended Huckel method indicate that there is no direct bond between the two silicon atoms in the bis(silylene)iron complex Cp(OC)Fe{SiH2 ⋯ O(H) ⋯ SiH2}. This means that the coupling in 2 can be described as the sum of the two geminal couplings, 2J(SiFeSi) and 2J(SiOSi).

Growth of layered III-VI compound semiconductor GaSe on a GaAs(111)B substrate has been investigated for the purpose of an effective passivation of the GaAs surface. Although GaSe and GaAs have completely different lattice structures, it has been found that a good GaSe film having its own lattice constant grows epitaxially. The growth proceeds by weak Van der Waals forces between each layer of GaSe so that the lattice matching condition is drastically relaxed. The photoluminescence intensity of the GaAs(111)B surface covered by the GaSe film is larger than that of an as-etched surface, even after the sample has been left in air for a month. The decay of the photoluminescence intensity of the GaSe-covered surface has been found to be slower than that of the sulfur-passivated surface, indicating its excellent ability for the passivation. This seems to result from the stability of covering GaSe film in addition to the proper termination of dangling bonds by selenium atoms at the GaSe/GaAs interface.

The lattice matching condition usually encountered in heteroepitaxial growth has been found to be relaxed greatly when the interface between constituent materials has Van der Waals nature and forms no direct chemical bonds. Layered transition metal dichalcogenides are the typical materials having that nature, and a variety of heterostructures can be grown by using them. This kind of approach has been proved to be applied also to heteroepitaxial growth between such quasi-one-dimensional materials as tellurium and selenium, that onto dangling-bond terminated three-dimensional material substrates, and that of organic materials forming Van der Waals type crystals.

The concept of Van der Waals epitaxy that has been recently introduced removes severe lattice matching requirement by using materials which only have strong bonding in two dimensions. We demonstrate that an epilayer of MoSe2 deposited on various substrates can produce films of high crystalline quality despite of large mismatch. RHEED oscillation, observed in-situ for growing MoSe2 epilayers, shows a layer-by-layer growth with evidence for bilayer type growth, from which the 2Hb polytype is determined. STM provides real space images of the morphology of the epilayer, and shows novel structures resulting from the large lattice mismatch where the epilayer atoms are commensurated.

structures. In the case of Van der Waals epitaxy, single crystalline Se film has grown epitaxially on Van der Waals epitaxy has opened a new way Te substrate in spite of the lattice mismatch as to fabricate ultrathin heterostructures consisting large as 18%. of layered materials. In this method, epitaxial In the present work, we have tried to fabricate growth proceeds with Van der Waals force, since more heterogeneous systems by Van der Waals the layered materials have no dangling bonds on epitaxy. Growth of ultrathin NbSe2 or MoSe2 their cleaved surfaces. In previous work we sue- films have been carried out on an air-cleaved face ceeded in growing an ultrathin selenium film on a of mica (muscovite, KA12(OH)2(Si3AlO10)). Alcleaved face of tellurium and ultrathin NbSe2 or though mica has the same layered structure as MoSe2 films on a cleaved face of MoS2 [1,2]. The transition metal dichalcogenides (TX2 such as most prominent advantage of this method is that NbSe2 or MoSe2), its surface atomic structure is the use of layered materials as constituent compo- quite different from those of TX2 as shown in fig. nents removes the strict requirement for the lattice 1. Mica has a pseudohexagonal lattice with its matching condition, which is always encountered lattice constant larger by 50% or 58% than that of in the conventional method of growing hetero- NbSe2 or MoSe2, respectively. In addition, half a