Structural, morphological, optical and sensing properties of SnSe and SnSe2 thin films as a gas sensing material

Abstract

In this work, orthorhombic tin selenide thin films were grown onto three different substrates using an organophosphorus precursor (Ph3PSe) via chemical vapor deposition. Structural, microstructural and morphological properties of the as-grown films were systematically investigated using XRD, ESEM and AFM respectively. Grain size, microstrain and dislocation were calculated and correlated with different factors. The effects of selenization temperature and substrate type on different film properties and gas sensing response of films deposited onto alumina substrates were investigated. XRD analysis reveals the appearance of a mixed phase as a function of temperature. Furthermore, substrate type plays a key role in the rate of appearance of each phase. EDAX analysis confirms the existence of the desired elements and detect the evaporation of selenium and the appearance of oxygen at higher temperatures. Atomic force microscopy (AFM) was used to investigate the surface topography of the grown thin films.Optical properties of the films grown onto glass and silicon substrates were studied. From the recorded optical data, a direct optical band gap in the range of 0.9–1.3 eV was obtained with an absorption coefficient α > 104 cm−1 throughout large spectral regions. Optical studies were remarkably affected by the obtained phase as well as the selenization temperature. Gas sensing properties of the samples deposited onto alumina substrates were examined as a new sensing material for detection of methane gas at different concentrations. SnSe sensors show high sensitivity, are reversible and exhibit fast response and recovery times compared to SnSe2 sensors. Keywords: Triphenylphosphine selenide, CVD, SnSe thin film, XRD, Optical properties, Sensing properties