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Centimeter‐size single‐crystalline Nb3I8, a new family of two‐dimensional materials, is first synthesized by a vapor transport reaction of niobium and iodine. Through the mechanical exfoliation method, the bulk Nb3I8 crystal is cleaved to monolayer and multi‐layered flakes. It is confirmed to consist of numerous monolayers of Nb3I8 bonded by weak van der Waals interaction. By utilizing atomic force microscopy (AFM) and scanning Kelvin probe microscopy (SKPM), the information on structure and electrical properties is obtained at the same time. The analysis results show that the surface potential difference and the work function tend to increase as the Nb3I8 becomes thicker due to the interlayer screening effect. The results for the work function variation dependence on thickness are useful for selecting a suitable metal electrode for future Nb3I8‐based nano‐devices which can have a significant impact on performance. Centimeter‐size single‐crystalline Nb3I8 crystal, a new family of 2D materials, is firstly realized by a controlled solid‐state reaction of niobium and iodine. Since each layer of Nb3I8 is linked by a weak vdW forces, bulk Nb3I8 crystal is easily cleaved to monolayer and multi‐layered flakes by mechanical exfoliation. By utilizing the scanning Kelvin probe microscopy, the authors confirm that the surface potential difference and the work function tended to increase as the Nb3I8 become thicker due to the interlayer screening effect. [ABSTRACT FROM AUTHOR]

The two-dimensional (2D) inorganic material Nb 3 I 8 , which can be separated into atomic planes, was synthesized through a vapor transport reaction between niobium and iodine. High-purity and cm scale large Nb 3 I 8 crystals were obtained by controlling the growth temperature (600–700 °C) and the stoichiometric ratio between niobium and iodine (using excess I 2 condition, niobium: iodine = 3:9). The semiconductor characteristics were measured by the change of electrical conductivity with temperature (increased conductivity with temperature in the range of 100 K–300 K), and have a band gap of ∼1 eV (∼1200 nm) through Infrared (IR)-visible light absorption analysis. Based on these characteristics, the device characteristics of detecting IR near 1200 nm region were verified. Besides few-layers of Nb 3 I 8 was acquired by the mechanical exfoliation method, and experimentally observed by atomic force microscopy (AFM). This 2D material is expected to have an important role in developing another 2D materials and in new nano-optoelectronic devices using it. • Synthesis of 2D material Nb 3 I 8 in centimeter scale. • Experimental estimation of band gap of Nb 3 I 8 about (∼1 eV) and application to IR detectors. • Bulk to few-layers separation of Nb 3 I 8 sheet using mechanical exfoliation method. [ABSTRACT FROM AUTHOR]