Crystal Growth & Design最新文献

In order to solve the current energy and environmental crisis, the design of efficient catalyst materials is a highly effective solution. In this paper, the photocatalytic performance of TiO₂/g-C₃N₄ composites was improved by regulating their microstructure, such as by constructing nanosheet structures, defect sites, and contact interfaces. Although TiO₂ had limited activity in H₂ production under visible light irradiation, it could serve as an electron acceptor of g-C₃N₄, and it greatly increased the photocatalytic activity of g-C₃N₄. The optimal TiO₂/g-C₃N₄ composite showed good photocatalytic performance (436.3 μmol h^–1 g^–1), which was 23.8 and 3 times that of T400 and g-C₃N₄, respectively. The increased photocatalytic activity of the TiO₂/g-C₃N₄ composite could be attributed to the higher separation rate of the photogenerated charge carriers (PCCs), more active sites for the reaction, and a lower energy barrier than that of g-C₃N₄. Through many characterization and testing technologies, this work deeply studies the relationship between the fine structure and reaction mechanism of 2D/2D TiO₂/g-C₃N₄, providing a new direction and understanding for the design and development of 2D materials with highly efficient activity.

Here, we report on the low-pressure chemical vapor deposition synthesis of multilayer BN films on single crystalline Ni(111) films. We highlight the crucial role of substrate pretreatment to stabilize the Ni(111) thin film on YSZ/Si(111) prior to BN precursor exposure at high temperature. We show that an in situ double-step thermal process under primary vacuum allows us to obtain clean and flat nickel surfaces suitable for homogeneous BN growth. Scanning and transmission electron microscopies, Raman spectroscopy, and atomic force microscopy have been used to characterize statistically the BN film from the atomic to the millimeter scale. We show that we obtain a sp²-hybridized BN film with a rhombohedral ABC stacking sequence. The 3 nm-thick film is continuous at the millimeter scale, with a mean roughness of 0.9 nm and no wrinkles.

EuCa₄O(BO₃)₃ (EuCOB) crystals were grown by the Bridgman method for the first time. The purpose of this work is to evaluate the visible laser application prospect of EuCOB single crystal. The phase structure, thermal properties, and optical properties of EuCOB were studied, and the density of states was calculated by the first principles. The cell parameters of the EuCOB crystal are a = 8.0966 Å, b = 16.0309 Å, c = 3.5670 Å, and β = 101.29°, respectively. The thermal conductivity of the EuCOB crystal is 2.98 W m^–1K^–1, which has a significant advantage in RCOB series crystals. The melting point of EuCOB crystal is 1480 °C. The maximum absorption cross-section of the EuCOB crystal is 1.0123 × 10^–21 cm² (@393 nm), the maximum emission cross-section along the Y direction is 2.644 × 10^–21 cm² (@610 nm), and the fluorescence decay time τ is 1.04 ms. A series of data and analyses prove that the EuCOB crystal is a potential red laser gain material and has great potential in the field of subsequent lasers.

Two D-A-D diphenothiazine derivatives, 24DPTCN and 26DPTCN, were prepared to investigate the impact of molecular isomerization on the luminescent behaviors in solution and crystalline states and the response to the external force stimuli. It was found that the two compounds had two emission bands in solutions. The quantum chemical calculations suggest that the coexistence of two configurations results in two emission bands, the short-wavelength bands are from the axial–equatorial (ax-eq) form for 24DPTCN and 26DPTCN, and the long-wavelength emission bands are ascribed to those molecules in equatorial–equatorial (eq-eq) form. In the crystalline phase, 24DPTCN adopts an ax-eq form and emits very weak blue fluorescence, and 26DPTCN has an eq-eq conformation and emits green fluorescence. More importantly, they also possess distinct response to force stimulus. 24DPTCN had a large redshift of 85 nm in the emission band under mild force stimulus, accompanied by an enhancement in the emission intensity because of the configuration conversion from ax-eq to eq-eq. On the other hand, only a shift of 28 nm was observed, and the fluorescence weakened after 26DPTCN crystals were ground because a small number of eq-eq 26DPTCN transferred into ax-eq ones.

Despite the record-high efficiency of GaAs solar cells, their terrestrial application is limited due to both the particularly high costs related to the required single-crystal substrates and epitaxial growth. A water-soluble lift-off layer could reduce costs by avoiding the need for toxic and dangerous etchants, substrate repolishing, and expensive process steps. Sr₃Al₂O₆ (SAO) is a water-soluble cubic oxide, and SrTiO₃ (STO) is a perovskite oxide, where a_SAO ≈ 4 × a_STO ≈ (2√2)a_GaAs. Here, the pulsed laser-deposited epitaxial growth of SrTiO₃/Sr₃Al₂O₆ templates on STO and Ge substrates for epitaxial GaAs growth was investigated, where SAO works as a sacrificial layer and STO protects the hygroscopic SAO during substrate transfer between deposition chambers. We identified that the SAO film quality is strongly dependent on the growth temperature and the O₂ partial pressure, where either a high T or a high P(O₂) improves the quality. XRD spectra of the films with optimized deposition parameters showed an epitaxial STO/SAO stack aligned to the STO (100) substrate, and TEM analysis revealed that the grown films were epitaxially crystalline throughout the thickness. The STO/SAO growth on Ge substrates at a high T with no intentional O₂ flow resulted in some nonepitaxial grains and surface pits, likely due to partial Ge oxidation. GaAs was grown by metalorganic vapor-phase epitaxy (MOVPE) on STO/SAO/STO templates. Lift-off after dissolving the sacrificial SAO in water resulted in free-standing ⟨001⟩ preferentially oriented polycrystalline GaAs.

GaAs was epitaxially lifted off from a SrTiO₃ substrate using Sr₃Al₂O₆ as a water-soluble sacrificial layer, resulting in ⟨001⟩ preferentially oriented polycrystalline free-standing GaAs films.