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A series of xBaO–yB2O3–zBi2O3 (x + y + z = 100, mol%) glasses were synthesized and added to BaTiO3 ceramics as a sintering aid to reduce the sintering temperature. The thermal and dielectric properties of the glasses and glass structures were characterized. Glasses with a high △T (difference between crystallization start temperature and glass-transition temperature) were the focus of this work. Composites with 70-mass% BaTiO3 and 30-mass% glasses and composites with high relative density and excellent dielectric properties were obtained after sintering at 600 °C. Secondary phases were formed in most of the composites; three glasses with a high △T value were formed without a secondary phase at 800 °C. Raman analysis showed that the glasses with a high △T contained Bi–O–Bi and B–O–B networks, which likely influence the thermal stability of the glasses, resulting in glasses suitable for sintering aids for BaTiO3 powders.

We investigated the multiscale characters of the crystal structure of the oxynitride perovskite LaTiO2N. While X-ray diffraction results identified the average structure as being centrosymmetric, we detected a signature of unknown structural deformation. By viewing the local structure, we unveiled the formation of a polar structure at the nanoscale.

In this study, high purity n-type Mg2Ge single crystals are grown in graphite crucibles under nitrogen atmosphere using a facile growth process. X-ray diffraction proves that the grown crystal consists of only Mg2Ge single phase without any other additional impurity peaks. The clear symmetrical Laue diffraction pattern of the cleaved substrate demonstrates the single crystalline nature of the grown Mg2Ge crystal ingot. The Hall Effect measurement of the polished Mg2Ge wafer shows that the latter had a moderate carrier density (5.66 * 1016 cm−3), mobility (253 cm2/V) and electrical resistivity (0.5 Ω. cm) at room temperature. Detailed analysis of the temperature dependence of the carrier density demonstrates that the shallow donor level, which gives rise to the n-type conduction of grown Mg2Ge crystals is due to the unintentional Al impurities from Mg source material. Mg2Ge pn-junction photodiodes are also manufactured for the first time by thermal diffusion of silver thin layer into n-Mg2Ge at 550 °C for 5 min in an argon atmosphere. The results reveal that the fabricated p-n photodiodes had a clear rectifying behavior and a remarkable spectral response in the wavelength range from 0.8 to 1.7 μm with a maximum room temperature zero-biased photoresponse of 7 mA/W at 1.2 μm. These outcomes indicate that the fabricated Mg2Ge photodiodes are promising to detect short-wavelength infrared (SWIR) light in the above-mentioned wavelength domain.

International audience; Transition metal nitrides (TMN) form a class of materials with unique physical and chemical properties. Among them, molybdenum nitrides are mainly used as high-performance magnets or catalysts for a wide range of reactions. This work aims at developing innovative syntheses to prepare nanostructured TMN from metallic clusters for heterogeneous catalysis. The use of a nanoscale precursor such as (TBA)(2) Mo6Br14 (TBA = tetrabutylammonium = (C4H9)(4)N+) enables us to reach different molybdenum nitride compositions (Mo2N, Mo5N6) by thermal reaction under ammonia at relatively low temperatures. Such a novel synthetic approach highlights the prime importance of the starting material to stabilize specific stoichiometries. The impact of this new synthetic route is characterized by several techniques including electron probe microanalysis and high-resolution transmission microscopy. Moreover,catalytic properties of these potential cost-effective catalysts are investigated for the Water-Gas Shift Reaction.

Ca3TaAl3Si2O14 (CTAS) single crystal is attracting much attention for high temperature sensor applications due to its high electrical resistivity and excellent piezoelectric properties. However, it is a big challenge to grow high quality CTAS single crystals. In this work, its growth conditions are optimized. Crack- and inclusion-free crystals are grown, achieving even a high quality single crystal with a width over 2 in. In addition, the temperature dependence of electro-elastic properties is systematically studied. This crystal presents a high thermal stability of structure and electro-elastic properties. The dielectric loss is less than 3% from room temperature to 650 °C. Therefore, CTAS single crystal is promising for high temperature sensor applications.

In this study, the low-temperature sintering of BaTiO 3 (BT) and densification were achieved by introducing glass-phase 40BaO-20Bi 2 O 3 -40B 2 O 3 (BBB, mol%). This incorporation of BBB glass in BT, by varying the particle size and amount of composites, significantly affected the sintering behavior and the final dielectric performance of BT. In the sintering route, the optimum BBB glass particle size was slightly larger than that of the BT host powders. Such liquid-phase glasses, when used as a sintering aid, not only visibly improved the grain refinement of the BT ceramics, but also greatly reduced the sintering temperature of BT from 1300 to 600 °C without forming a secondary phase. Notably, the dielectric properties and fine densification of the samples were optimal at a sintering temperature of 800 °C. Therefore, BBB glass as a sintering aid is promising and beneficial for lowering the sintering temperature of BT.

Bulk gallium monosulfide (GaS) single crystals are increasingly required for research on optical devices used in the mid-infrared (IR) region and for 2D GaS. In this work, a GaS single crystal was grown in an evacuated quartz ampoule and characterized by the X-ray Laue backscattering method, differential thermal analysis (DTA), X-ray rocking curve, Raman spectroscopy, optical transmission spectroscopy, and scanning electron microscope-energy dispersive X-ray microanalysis (SEM-EDX). First, polycrystalline GaS was synthesized using our previously improved process, on a common horizontal furnace. Before the crystal growth of GaS, its melting point was measured via DTA of the synthesized polycrystalline GaS and was determined to be 965 °C. Based on the data obtained, GaS single crystals were grown in evacuated quartz ampoules using the vertical Bridgman method without a seed crystal. The X-ray Laue backscattering pattern and Raman spectra revealed that the grown GaS crystal was indeed a single crystal and that the growth direction was parallel to the (0 0 1) face. The optical transmittance range was found to be 0.48–14 μm.

ScN films were grown on MgO(110) substrates and α-Al 2 O 3 ( 10 1 ¯ 0 ) substrates by a molecular beam epitaxy method, and their crystalline orientation, crystallinity, and electric properties were examined. (110)-oriented ScN films were epitaxially grown on MgO(110) substrates with the same crystal orientations, and ScN films with an orientation relationship (110)ScN || ( 10 1 ¯ 0 )α-Al 2 O 3 and [001]ScN || [ 1 2 ¯ 10 ]α-Al 2 O 3 were epitaxially grown on α-Al 2 O 3 ( 10 1 ¯ 0 ) substrates. Remarkably, electric-resistivity anisotropy was observed for ScN films grown on MgO(110) substrates, and the anisotropy depended on the growth temperature. The carrier concentration and Hall mobility of the ScN films grown on α-Al 2 O 3 ( 10 1 ¯ 0 ) substrates ranged from 10 19 –10 21 cm -3 and 10–150 cm 2 V -1 s -1 , respectively. The crystallinity, crystalline-orientation anisotropy, and electric properties of the films were strongly affected by growth conditions. For the growth of ScN films with high mobility on α-Al 2 O 3 ( 10 1 ¯ 0 ) substrates, a high temperature and an appropriate ratio of source materials were necessary.

Effects of the nature of substrates, either crystalline or non-crystalline, on the structure and properties of ZnO films deposited by sputtering were investigated. This study focuses mainly on the role of the external electric bias applied to substrates during magnetron sputtering deposition in controlling crystalline polarity, i.e., Zn-face or O-face, and the resulting film properties. It was found that polarity control was achieved on silica and silicon substrates but not on sapphire substrates. The substrate bias did influence the lattice parameters in the structural formation; however, the selection of the substrate type had a significant influence on the defect structures and the film properties.

The electronic and structural characteristics of the octahedral molybdenum cluster-based ternary compound, Cs2[Mo6Cl14], were investigated based on density functional theory (DFT) and subsequent comparisons with experimentally observed results. The geometry optimization and band structure calculations of Cs-2[Mo6Cl14] were performed using three standard functionals: local density approximation, Perdew-Burke-Ernzerhof (PBE) as a generalized gradient approximation, and PBE revised for solid compounds (PBEsol). The validity of the calculated results was experimentally examined via X-ray powder diffraction, ultravioletvisible (UV-vis) diffuse reflection, and X-ray photoemission spectra (XPS) measurements. PBEsol was found to show the best performance in terms of reproducing the experimentally refined lattice structure of the compound. The calculated band gap energy (E-g) was consistent with the value evaluated from the UV-vis measurement. Furthermore, the XPS valence spectrum of the compound was well reproduced by the calculated projected density of state weighted with the photoionization probabilities of Al K-alpha. Although the spectral shapes simulated using the three functionals were similar, PBEsol reproduced the energy levels of the electronic states of both [Mo6Cl14](2-) and Cs+ ion with greater consistency. Therefore, it was concluded that PBEsol is the most appropriate functional for DFT calculations of the metal cluster-based lattice system. (C) 2017 The Ceramic Society of Japan. All rights reserved.

The integration by a solution deposition process of tantalum octahedral clusters in multifunctional nanocomposite materials and devices for smart windows is investigated for the first time in this study. Two [Ta6Bri12]n+ cluster core-based highly transparent visible UV and NIR filters are realized. Films are fabricated by incorporation of clusters in a polymer matrix and coating them on an ITO substrate. The electrochromic cell consists of a Ta6-based electrolyte inserted between two transparent conductive electrodes. In both cases, the modification of the absorption properties in the visible and NIR spectral range is possible by altering and controlling the oxidation state of the tantalum cluster. The stabilization of reduced [Ta6Bri12]2+ or oxidized [Ta6Bri12]3+/4+ species leads to green-emerald or slight brown filters having a slight or a strong red-NIR absorption respectively. Their efficiency in energy saving is estimated by the determination of figures of merit and color coordinates. This highlights that [Ta6Bri12]n+-based composites are promising absorbers for energy saving applications.

High quality colorless Ca 3 TaGa 3−x Al x Si 2 O 14 (CTGAS) single crystals are successfully grown by the Czochralski technique within the full solid solution range. The influence of Al content on the electrical resistivity, dielectric and piezoelectric properties is systematically investigated for the first time at room temperature, as well as a function of temperature up to 700 °C. With the increase of Al content the resistivity, the electromechanical coupling factor k 12 and the piezoelectric coefficient d 11 increase, while the dielectric permittivity e 11 T / e 0 decreases. CTGAS single crystals exhibit a very low dielectric loss ( 10 Ω cm at 400 °C for all samples, i.e. more than two orders of magnitude higher than that of the considered material La 3 Ta 0.5 Ga 5.5−x Al x O 14 . Present results indicate that, among the langasite family, Ca 3 TaAl 3 Si 2 O 14 is at present the most promising crystal for high temperature sensor applications, since it exhibits the highest resistivity and a good piezoelectric response.

A new pulverization process utilizing thermal treatment in controlled atmosphere was developed. The samples, including SrTiO3 single crystals, TiO2 single crystals and BaTiO3 ceramic, were pulverized into nano-sized powder by heating in gas stream containing air and ammonia (NH3) at high temperature. Although the detailed mechanism for this pulverization process is still unclear but it is evident that thermal treatment in NH3 based atmosphere containing small fraction of air (5–10%) causes not sintering but pulverization. Efficient synthesis of an oxynitride compound, LaTiO2N, was demonstrated by using nano-sized La2Ti2O7 precursor prepared by utilizing this new powder preparation process.

In this work the partial substitution of Ca by Sr in the known langasite single crystal Ca3TaAl3Si2O14 is investigated from the point of view of crystal growth in order to improve the piezoelectric properties. For it, a (SrxCa1-x)3TaAl3Si2O14 (SCTAS) single crystal with x = 0.25 was grown by the Czochralski method. The grown crystal was strongly faceted, highly transparent, and of a high crystalline quality, as indicated by a full width at half maximum of the X-ray rocking curve as small as 31 arcsec. On the other hand, the crystal exhibited a high resistivity, with a value over 1010 Ω cm at 400 °C. Temperature dependent piezoelectric measurements confirmed the effective enhancement of the d11 piezoelectric coefficient at any temperature, while maintaining the dielectric loss below 1% up to 600 °C. Therefore, SCTAS exhibits superior properties compared with other piezoelectric materials for high temperature applications.

The floating zone method was used to obtain single crystals several mm in size of the low-temperature rhombohedral form of Y2C rather than its typical rocksalt-type cubic form. This was achieved through optimization of the chemical compositions of the starting materials with the aim of producing a two-dimensional electride material. The crystals obtained exhibited a paramagnetic temperature-dependence at 1.8–300 K, with no trace of any obvious magnetic ordering.

We investigated the effects of thermal annealing for high-density subgap states in amorphous In–Ga–Zn–O (a-IGZO) films by focusing on low-quality defective films deposited without O 2 supply (LQ films). It was found that most of the subgap states were thermally unstable and decreased dramatically by annealing at ≤ 400 °C in O 2 . These defects (but with different shapes) were further reduced by 600 °C annealing, whose subgap states appeared similar to that of a-IGZO films deposited at an optimum condition (high quality, HQ films) and annealed at 300 °C. However, electron Hall mobilities and field-effect mobilities of their thin-film transistors (TFTs) were low for the LQ films/TFTs even annealed at 600 °C compared to those for the HQ films/TFTs. It implies that not only the subgap states but also heavier structural disorder deteriorated the electron transport in the LQ films. The present results also suggest that although a-IGZO deposition without O 2 supply is sometimes employed in particular for DC sputtering, supplying some O 2 gas would be better to produce good TFTs at lower temperatures.

To drive the research and development of two-dimensional (2-D) germanium monosulfide (GeS) applications, a more facile method for obtaining (GeS) single crystals is required. To that end, we first improved the method for synthesizing polycrystalline GeS to reduce the reaction time and prevent the explosion of the quartz ampoule, and this step was carried out inside a horizontal furnace. We also successfully grew a GeS single crystal without a seed crystal by melting this polycrystalline GeS inside a closed, evacuated quartz ampoule using a two-zone horizontal furnace and then employing a vapor transport method. The growth ampoule was specifically designed to prevent the molten GeS from flowing from the evaporation side to the growth side, where the crystal grew through an evaporation–recondensation transition in the temperature range of 654 to 660 ℃. Single-crystal X-ray diffraction was carried out to precisely determine the crystal structure, which revealed that the grown crystal was a GeS single crystal with an orthorhombic structure of the GeS-type (space group Pnma) and lattice parameters of a = 10.5284 (10), b = 3.6584 (3), and c = 4.3166 (4) A. A differential thermal analysis confirmed that the melting point of the grown GeS crystal was 664 ℃.

Hexanuclear tantalum bromide cluster units [{Ta6Bri12}La6] (i = inner, a = apical, L = ligand OH or H2O) are embedded into SiO2 nanoparticles by a reverse microemulsion (RM) based method. [{Ta6Bri12}Bra2 (H2O)a4]·nH2O (noted TBH) and tetraethyl orthosilicate (TEOS) are used as the starting cluster compound and the precursor of SiO2, respectively. The RM system in this study consists of the n-heptane (oil phase), Brij L4 (surfactants), ethanol, TEOS, ammonia solution and TBH aqueous sol. The size and morphology of the product namely {Ta6Br12}@SiO2 nanoparticles are analyzed by HAADF-STEM and EDS mappings. The presence and integrity of {Ta6Br12} in the SiO2 nanoparticles are evidenced by EDS mapping, ICP-OES/IC and XPS analysis. The optical properties of {Ta6Br12}@SiO2 nanoparticles are analyzed by diffuse reflectance UV-vis spectroscopy, further evidencing the integrity of the embedded {Ta6Br12} and revealing their oxidation state. Both {Ta6Br12}2+ and {Ta6Br12}3+ are found in SiO2 nanoparticles, but the latter is much more stable than the former. The by-products in this RM-based synthesis, as well as their related factors, are also discussed.

La 3 Ta 0.5 Ga 5.5-x Al x O 14 (LTGA) is a piezoelectric crystal from the langasite family which presents advantageous properties for high temperature sensor applications. It possesses a high piezoelectric constant and its structure remains stable up to 1500 °C. In this work, a LTGA single crystal has been grown by using the Czochralski technique under N 2 atmosphere with 1% O 2 . The high crystalline quality of grown crystal is confirmed by the 26 arcsec FWHM of X-ray rocking curves. High temperature X-ray diffraction measurements indicate the absence of phase transitions up to 1300 °C. The thermal properties of the crystal, including thermal expansion, specific heat, thermal diffusivity and thermal conductivity, are investigated as a function of temperature. The average thermal expansion coefficients are α a = 8.48 × 10 −6 K −1 and α c = 6.32 × 10 −6 K −1 . The thermal conductivities along the a and c axes at 50 °C are 1.2 and 2.0 W m −1 K −1 , respectively. The resistivity of grown crystal decreases from 4 × 10 10 to 2 × 10 5 Ω cm between 200 and 900 °C. The measured piezoelectric coefficient d 11 , electromechanical coupling factor k 12 and corresponding mechanical quality factor Q at room temperature are 6.94 pC/N, 17% and 12,000, respectively.

ZnO films were deposited using a spin-spray method with the source solution containing zinc nitrate and an oxidizing solution containing trisodium citrate onto glass substrates under various pH conditions. A ZnO film with a columnar structure was obtained at pH higher than 7.0, while no ZnO film was formed at a mixed solution pH of 6.7. The transparent and conductive ZnO film obtained from a mixed solution with pH 10.7 exhibited the lowest resistivity of 9.9 × 10−3 Ω cm with a high transmittance above 90%.

International audience; Among the solution deposition techniques, electrophoretic deposition (EPD) is a fairly rapid and low cost two-step process well-known for ceramic shaping and conductive surface coating. Recently we have reported the fabrication of transparent inorganic thin film composed of octahedral molybdenum clusters and shown that the stabilization of the cluster solutions during EPD is very important to obtain high quality films. In this study, we selected the Cs2Mo6Br i 8Br a 6 or ((n-C4H9)4N)2Mo6Br i 8Br a 6 clusters compound (i = inner ligands, a = apical ligands) as precursors in a Methyl Ethyl Ketone (MEK) solution to fabricate the inorganic Mo6 cluster transparent film on a conductive indium tin oxide (ITO) glass substrate. For the first time, the mechanism for the deposition process of metal clusters is proposed based on results obtained by the combination of complementary techniques such as infrared spectroscopy, X-ray analysis and electron microscopy. The Mo6 film on the ITO glass substrate exhibiting a Br-rich layer is quickly deposited during the first stage of the EPD followed by a multilayer structure consisting of two types of cluster compounds, [Mo6Br i 8Br a 4(H2O) a 2] and (H3O)2[Mo6Br i 8Br a 4(OH) a 2].

International audience; This study reports the first integration of inorganic tantalum octahedral metal atom clusters into multifunctional nanocomposite coating materials and devices for window technology and energy saving applications. [Ta6Br12i](n+) (n = 2, 3 or 4) cluster-based high visible transparency UV and NIR filters are realized. Green and brown colored films are fabricated by coating on an indium-doped tin oxide glass substrate by electrophoretic deposition, an industrialized solution process. The efficiency in energy saving of the new UV-NIR filters was estimated by the determination of different figure of merit (FOM) values, such as Tvis, Tsol and Tvis/Tsol (Tsol = solar transmittance and Tvis = visible transmittance), and the color coordinates (x, y, z and L*a*b). The Tvis/Tsol ratio is equal to 1.25 for the best films. Such values are evidence of a higher energy saving efficiency than most of the inorganic composites reported in the literature. These promising results pave the way for the use of transition metal clusters as a new class of nanocoatings in energy saving window-based applications.

We observed surface segregation of W (0.05–4 mol%) doped in ZnO films by annealing above 900 K. The segregation coefficient was related to the crystal quality of the film, where slower segregation occurs in higher-quality crystalline films. Using low-energy He + ion scattering spectroscopy for structure analysis, we found that the W–ZnO surface terminates with an O-layer, and W is located in a substitutional site of Zn at the second surface layer as a consequence of segregation. On the other hand, we observed no indication that W occupies certain sites in the ZnO lattice at the subsurface. Ultraviolet photoelectron spectroscopy (He I) on the W-segregated ZnO surface indicates that W is hexavalent at the Zn site. The segregation of the W atom is likely accompanied by two Zn vacancies. Ion beam mixing followed by annealing of the ZnO surface deposited with W provides a surface electronic structure similar to that of W-segregated ZnO.

The effect of crystalline polarity on the microstructure of gallium-doped zinc oxide (GZO) deposited using magnetron sputtering onto glass substrates was investigated. X-ray photoelectron spectroscopy was used to determine the crystalline polarity of c-axis textured GZO films. Grains whose radii were more than 1 μm grew abnormally in 0.2 mol% doped GZO when the film was thicker than ~ 1 μm, and the radius of the grains was much smaller than 100 nm in the heavily (i.e., 4 mol%) doped GZO, regardless of the film thickness. Such abnormal growth of the grains in the 0.2 mol% doped GZO films coincided with a change in the crystalline polarity: the surfaces of unusually large GZO grains were terminated with the (000 1 ¯ ) face, and those of normal GZO grains were terminated with the (0001) face. The results indicated that polarity flipping is a very important event for controlling the texture of doped zinc oxide films.

Simultaneoushighcapacitanceandlow dielectric loss are absolutely necessary for thin-film capaci-tors (TFCs). In addition, the fatigue behavior, which currentlylimits both the device reliability and lifetime, also has to beimproved for the utilization of perovskite-type titanate in TFCs.As suggested by earlier studies

Tin oxide (SnO2) hollow nanofibers doped with cerium oxide (CeOx) were synthesized to study the impact of CeO2 additives on their chemical sensing response. X-ray diffraction analysis and Raman scattering spectroscopic analysis showed that crystallization of CeO 2 in the fiber composites was observed only when the Ce concentration was greater than 6 mol%. Also, maximum sensing response to ethanol was seen in the fiber composites with 6 mol% addition of Ce. Accordingly, we have discussed the possible explanations for this, including the role of crystalline CeO 2 as a surface catalyst, and the role of hydrogen liberated during the dehydrogenation reaction of ethanol diffusing into the SnO2 lattice. The results obtained in this study indicate that SnO 2-CeO2 nanofiber composites are potential candidates for use as high-sensitivity gas sensors. � 2013 Elsevier B.V. All rights reserved.

*National Institute for Materials Science (NIMS), 1–1 Namiki, Tsukuba, Ibaraki 305–0044, Japan **Isotope Imaging Laboratory, Creative Research Institution, Hokkaido University, Sapporo 001–0021, Japan ***Natural History Sciences, Hokkaido University, Sapporo 060–0810, Japan ****Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226–8503, Japan

We investigated the effect of zinc oxide addition for the defects in the dense SnO2 ceramics. Cathode and photoluminescence properties revealed the luminescence originated to oxygen vacancies in SnO2 grains and the presence of non-radiative defect at the grain boundaries. The oxygen diffusion profile showed that the oxygen diffusion was controlled by the limited process at the surface and uniform concentration of 18O at the grain boundaries inner side of sample. This sample exhibited a low Zn concentration in grains and a high Zn concentration at grain boundaries. We conclude that segregation of Zn at grain boundaries prevents SnO2 from decomposing at high temperatures, enabling dense SnO2 ceramics to be obtained.

Isotopic ZnO thin films were deposited on the c -plane of ZnO single crystals by pulsed laser deposition. The isotopic abundance of Zn in the films was determined with a secondary ion mass spectrometry before and after the films was diffusion annealed. The diffusion profiles across the film/substrate interface behaved smooth features. The zinc diffusion coefficient ( D Zn ) was obtained by analyzing the slope of the profile in the annealed sample. The temperature dependence of D Zn was determined to be D Zn (cm 2 /s)=8.0×10 4 exp(−417[kJ/mol])/RT, where R and T are gas constant and temperature. The zinc ion diffusion coefficients were of the same order as that in a ZnO single crystal. A comparison of the experimental and theoretical values indicated that the zinc ions diffused in the thin film and the single crystal through a vacancy mechanism.

High electric conductivity was achieved in ZnO films prepared by a low-temperature (

The high frequency characteristics of hybrid structures made from indium tin oxide (ITO) films and very fine gold (Au) lines were theoretically and experimentally investigated to develop invisible coplanar waveguide (CPW) structures for microwave and millimeter-wave applications. After optimizing the Au/ITO hybrid structures, we achieved fabrication of an invisible CPW structure showing both high transmission and low reflection characteristics in the GHz range. Electromagnetic simulations by using a finite elements method explained the reason for the improved characteristics of the optimized Au/ITO hybrid CPW.

The surface structure of a single-crystal ZnO wafer was studied by angle-resolved x-ray photoelectron spectroscopy (ARXPS) using synchrotron radiation. As a result, well-defined x-ray photoelectron diffraction (XPD) patterns were obtained for the (0001) and (0001¯) polar surfaces using the photoemission from the Zn 2p3/2 and O 1s core levels. The XPD patterns were indexed assuming forward scattering of photoelectrons by neighboring ions. Further, the XPD patterns for the (0001) and (0001¯) surfaces were different from each other, indicating the possibility for using the XPD technique for polarity determination.

The crystalline polarity of undoped and impurity-doped ZnO films grown on SiO2 glass substrates was investigated with the goal of achieving polarity-selective growth of ZnO films on non-crystalline substrates. We first demonstrated that hard X-ray photoelectron spectroscopy (HX-PES) is an appropriate method for determining the crystalline polarity of ZnO. We then characterized the ZnO films grown by pulsed laser deposition using HX-PES. The resulting films deposited with a 1 mol% Al-doped ZnO target had the (0001) surface, whereas films grown with nominally undoped, 0.1 mol% Al-doped, 1 mol% Ga-doped, and 1 mol% In-doped ZnO targets had the (000 1 ¯ ) surface. Since a clear polarity change due to Al-doping was seen at the ZnO/glass structure, we conclude that the essential parameter governing the polarity of the ZnO films is unlikely lattice matching (alignment of the lattice on the atomic scale) at the heterointerface between the ZnO films and substrates.

Tin sulfide (SnS) single crystal was successfully grown using the horizontal gradient freeze method. Characterization of the grown crystal revealed a single SnS phase and an orthorhombic structure with lattice parameters a = 4.327, b = 11.18, and c = 3.981 A. Composition analysis revealed a stoichiometric composition equivalent to a congruent melt composition. The grown SnS crystal was confirmed to be single crystal by the X-ray Laue pattern. The melting point of the SnS was measured by differential thermal analysis and found to be 878 °C. The grown crystal had p-type conductivity, a carrier concentration of 8 × 10 17 cm − 3 , electrical resistivity of 0.08 Ω cm, and hole mobility perpendicular to the (0 1 0) direction of 98 cm 2 /V s at room temperature.