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   https://doi.org/10.1088/2053-1583/ac8435  

   Shehzad, M Arslan; Lee, Yea-Shine; Cheng, Matthew; Lebedev, Dmitry; Tyner, Alexander C; Das, Paul Masih; Gao, Zhangyuan; Goswami, Pallab; dos Reis, Roberto; Hersam, Mark C; et al (August 2022, 2D Materials)

   Abstract Transition metal dichalcogenides (TMDs) are known for their layered structure and tunable functional properties. However, a unified understanding on other transition metal chalcogenides (i.e. M 2 X) is still lacking. Here, the relatively new class of copper-based chalcogenides Cu 2 X (X = Te, Se, S) is thoroughly reported. Cu 2 X are synthesized by an unusual vapor–liquid assisted growth on a Al 2 O 3 /Cu/W stack. Liquid copper plays a significant role in synthesizing these layered systems, and sapphire assists with lateral growth and exfoliation. Similar to traditional TMDs, thickness dependent phonon signatures are observed, and high-resolution atomic images reveal the single phase Cu 2 Te that prefers to grow in lattice-matched layers. Charge transport measurements indicate a metallic nature at room temperature with a transition to a semiconducting nature at low temperatures accompanied by a phase transition, in agreement with band structure calculations. These findings establish a fundamental understanding and thrust Cu 2 Te as a flexible candidate for wide applications from photovoltaics and sensors to nanoelectronics. 

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2. Stepwise Sulfurization from MoO ₃ to MoS ₂ via Chemical Vapor Deposition

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3. High-temperature low-pressure chemical vapor deposition of β-Ga ₂ O ₃

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4. Coherent Spin Dynamics in Vapor-Deposited CsPbBr ₃ Perovskite Thin Films

   https://doi.org/10.1021/acs.chemmater.1c04382  

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5. Vapor Deposition of Perovskite Precursor PbI ₂ on Au and Graphite

   https://doi.org/10.1557/adv.2020.65  

   Ecker, Benjamin; Wang, Ke; Gao, Yongli (January 2020, MRS Advances)

   Abstract The energy level alignment that occurs at the interfaces in planar-hetero structured perovskite photovoltaic devices strongly influences the charge transport across the interface, and thus plays a crucial role in overall device performance. To directly observe the energy level alignment requires pristine homogeneous surfaces that are free of contamination including adventitious carbon. Co-evaporation offers the ability to grow perovskite thin films in-situ, and the method involves thermally evaporating the perovskite precursors such as PbI 2 and CH 3 NH 3 I. Early reports have shown that the perovskite film formation and stoichiometry are problematic at ultralow coverages. In particular, it was reported that there was excessive PbI 2 and a deficiency in CH 3 NH 3 I. Using photoemission spectroscopy, we investigated the perovskite precursor PbI 2 on gold and highly oriented pyrolytic graphite (HOPG) surfaces. Results show that the nature of the surface and the deposition conditions can strongly influence the film formation. Excessive iodine observed in the initial evaporation stages appears to be substrate dependent, and this may influence the overall energy level alignment. 

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