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Abstract Highly oriented Bi 2-x Sb x Te 3 (x = 0, 0.7, 1.1, 1.5, 2) ternary nanocrystalline films were fabricated using vacuum thermal evaporation method. Microstructures and morphologies indicate that Bi 2-x Sb x Te 3 films have pure rhombohedral phase with well-ordered nanopillars array. Bi, Sb and Te atoms uniformly distributed throughtout films with no precipitation. Electrical conductivity of Bi 2-x Sb x Te 3 films transforms from n-type to p-type when x > 1.1. Metal-insulator transition was observed due to the incorporation of Sb in Bi 2 Te 3. Bi 2-x Sb x Te 3 film with x = 1.5 exhibits optimized electrical properties with maximum electrical conductivity σ of 2.95 × 105 S m−1 at T = 300 K, which is approximately ten times higher than that of the undoped Bi 2 Te 3 film, and three times higher than previous report for Bi 0.5 Sb 1.5 Te 3 films and bulk materials. The maximum power factor PF of Bi 0.5 Sb 1.5 Te 3 nanopillars array film is about 3.83 μW cm−1 K−2 at T = 475 K. Highly oriented (Bi,Sb) 2 Te 3 nanocrystalline films with tuned electronic transport properties have potentials in thermoelectric devices. [ABSTRACT FROM AUTHOR]

The development of high-performance room temperature sensors for detecting trace nitrogen dioxide (NO 2) levels is critical for Internet of Things based environmental monitoring. We present a novel NO 2 gas sensor based on tin selenide (SnSe) nanosheet arrays films deposited on a variety of substrates using vacuum thermal evaporation. The nanosheets formed well-oriented arrays and had a thickness of about 10 nm and lateral size of 0.2–1 µm. The films' synthesis was well controlled, and the NO 2 gas sensors' performance was tuned by adjusting the microstructure of the films. The gas sensors were highly responsive to NO 2 concentrations ranging from 100 to 300 ppb, it can achieve a response of 155% towards 300 ppb concentration of NO 2 at room temperature; the gas sensing performance is affected by film thickness and microstructure. At a high NO 2 gas concentration of 10 ppm, a response time of 12 s and response rate of 700% were achieved at room temperature. Furthermore, the high selectivity and repeatability of the SnSe nanosheet arrays film gas sensor were demonstrated. Because of its ease of fabrication and high performance, the NO 2 gas sensor described here has promising applications. • A novel tin selenide (SnSe) nanosheet arrays film gas sensor has been fabricated. • The sensors show a high response for sensing NO 2 with ppb level at room temperature. • The sensors performance was optimized by adjusting the microstructures of the films. [ABSTRACT FROM AUTHOR]