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[Display omitted] • The surface chemical composition of β-Ga 2 O 3 films is discussed in depth. • The component of O 1s with the binding energy around 531.8 eV is attributed to surface lattice O atoms. • The defects inside the β-Ga 2 O 3 films were analyzed by HRTEM. β gallium oxide (β-Ga 2 O 3) is an ultrawide bandgap semiconductor with great potential for solar-blind ultraviolet detection, power devices, and gas sensing. However, the understanding of the surface properties of β-Ga 2 O 3 remains insufficient. Here, epitaxial growth of β-Ga 2 O 3 films was carried by metal–organic chemical vapor deposition (MOCVD) on sapphire substrates. The surface chemical composition, surface layer crystalline properties, and surface morphology of the β-Ga 2 O 3 films were discussed and analyzed in detail. By comparing the atomic ratios of O/Ga, the surface morphology, and the crystalline properties of the films, we attribute the component of O 1s with the binding energy around 531.8 eV to surface lattice O atoms. Moreover, the one-dimensional defects inside the surface layers and the near-interface regions of the films were observed at atomic scale by high resolution transmission electron microscopy (HRTEM). By comparing the lattice fringes of different facets, the geometric phase uniformity, and the distribution of strain, we found that the crystalline quality of the surface layers is much higher than the near-interface regions. [ABSTRACT FROM AUTHOR]

[Display omitted] • A PDMS coated PTFE separation membrane for gaseous aromatic water was explored. • Effective separation properties of the prepared PDMS/PTFE membranes were found. • The medicinal components of the obtained essential oils meet the EP standard. • Membrane separation mechanism of gaseous peppermint aromatic water was revealed. This study harnessed polydimethylsiloxane (PDMS)-coated polytetrafluoroethylene (PTFE) composite (PDMS/PTFE) membranes for the separation of peppermint aromatic water in vapor state. The effects of the PDMS coatings' morphology structure on the separation performance of the membrane were investigated. The vapor permeation process, selective-permeation mechanism, and membrane stability were explored. Results showed that the separation effect of the membranes depended on the degree of polymerization of PDMS coating. Almost no water molecules can pass through the membrane during the 6 h separation process, and the separation factor was as high as 668. The main pharmacodynamic components in the separated permeate were L-menthol, L-menthone, and menthyl acetate, accounting for 49.16 %, 26.3 %, and 5.46 %, respectively, which conformed to the standard of the European Pharmacopoeia. The parameters of membrane separation showed that the maximum permeability coefficients of L-menthol, L-menthone, menthyl acetate, and water were 40.80, 20.28, 4.211, and 0.3945, respectively, at 105 °C and 65 kPa. This finding indicated that the large difference in permeability coefficient was the key to the excellent selectivity of the PDMS/PTFE membrane for separating volatile pharmaceutical components and water molecules in the peppermint aromatic-water system. [ABSTRACT FROM AUTHOR]