We report on van der Waals epitaxy of single-crystalline α-MoO3 sheets with single-unit-cell thickness on the mica substrate. The crystalline lattice structure, growth habits, and Raman spectra of the grown α-MoO3 sheets are analyzed. The anisotropic growth of α-MoO3 sheets can be understood by period bond chains theory. Unlike monolayer MoS2 or graphene, Raman spectra of α-MoO3 do not possess frequency shift from bulk crystal to single-unit-cell layer. The relative intensities of two Raman modes (Ag) at 159 and 818 cm−1 are sensitive to the polarization of incident light. This scenario provides a quick approach to determine the lattice orientation of α-MoO3 crystals. Our studies indicate that van der Waals epitaxial growth is a simple and effective way to fabricate high-quality ultrathin α-MoO3 sheets for physical property investigations and potential applications.
Tibet is located on the Qinghai-Tibetan Plateau in China, the highest and largest plateau in the world. It is in the Cold and Severe Cold zones according to the Chinese climatic division for building design and has unique climatic characteristics and traditional cultural background. In order to obtain a comprehensive understanding about the real indoor thermal environment and the residents' thermal comfort status in Tibet, a field investigation of residential buildings was conducted in the Tibetan Alpine region with on-site environmental parameter measurements and a simultaneous survey using a subjective thermal comfort questionnaire. Based on the analysis of the data collected from the field study, the value of the adaptive coefficient λ in the adaptive thermal comfort model aPMV= PMV 1+λPMV suitable to the Tibet area has been obtained as-0.34; and thus the acceptable thermal comfort temperature range for residential buildings in this area has been produced. The research findings provide comprehensive knowledge and a useful reference for the development of a design and evaluation standard for indoor thermal environments in the Tibet region.
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