Copper sulphide (CuxS) as an ammonia gas sensor working at room temperature

A solution growth technique (SGT) has been used to deposit CuxS (x = 1, 1.4, and 2) thin films on glass substrates at room temperature (300 K). These as-deposited thin films are characterized for their structural, optical and electrical properties by X-ray diffraction (XRD), energy dispersive analysis of X-rays (EDAX), scanning electron microscopy (SEM) and atomic force microscopy (AFM), optical absorption and current–voltage (I–V) measurements. XRD shows that the CuxS layer grew with hexagonal and monoclinic phases for x = 1 and 2, respectively. SEM and AFM show the nano-particles (x = 1 and 1.4) and nano-discs (x = 2) formation. The optical band gaps (Eg) of thin films are 1.26 eV (CuS), 1.96 eV (Cu1.4S), and 2.31 eV (Cu2S). In addition, surface wettability is studied by using double-distilled water drops for contact angle measurements. It is observed that the contact angle for Cu1.4S is larger than those for CuS and Cu2S films. It suggests that the x = 1.4 films have high-surface energy. Ammonia gas sensors are fabricated by using these copper sulphide thin films with silver metal contacts. Based on the time-dependent experimental results nanostructured CuxS serve as sensor material for the detection of NH3 molecules at room temperature.