Successful growth of molybdenum trioxide (a-MoO 3 ) nanostructures by thermal evaporation method for thermoelectricity production

This manuscript has reported the successful growth of MoO3 nanostructures using the horizontal tube furnace. A series of samples were prepared at different source‑to‑substrate distances (SSD) in order to optimise the highest value of power factor. The experimental conditions during the growth process were set as follows: constant oxygen flow rate (100 sccm), base pressure of the tube (2.5 × 10−3Torr), temperature of boat (800°C) and variable SSD (5–14 cm). The structural information obtained by Raman spectroscopy and X‑ray diffraction (XRD) suggested the crystallinity of α-MoO3 nanostructures by increasing the SSD which is because of the generation of secondary phases. The thermoelectric parameters (Seebeck coefficient, conductivity and power factor) of grown samples were found to increase from 32.07–89.23 μV/oC, 2.46–7.81 S/cm and 2.53 × 10−7-6.21 × 10−6 Wm−1C−2 respectively, with increasing SSD. The enhancement of thermoelectric properties with distance is related to the creation of secondary phases, which was already established by XRD and Raman data. The interface of two secondary phases can act as barrier where slow‑moving carrier is not able to cross this barrier. Only the carriers having high mobility are able to cross it and resulted in the enhancement of electrical conductivity and Seebeck coefficient simultaneously.