Synthesis and Characterization of Aluminium Sulphide (Al2S3) Thin Films

The synthesis of Al2S3 thin film was carryout using electrodeposition technique. The electrodeposition bath system is composed of a source of cation (i.e. AlSO4.17H2O for Al2+) and a source of anion (i.e.  Na2SO4 for S2-).  Indium doped Tin Oxide (ITO)  was  used  as  the  cathode  while  the  anode  was  carbon and fluorine electrode. The temperature was varied by heating the entire precursor using a standard heating mantle with temperature ranges from 20 °C- 120 °C and the growth of Al2S3 thin films was carried out using the temperature range from 50 °C-80 °C at interval of 10 °C which later was converted to Kelvin. The XRD was found to be of wurtzite-like structure as hexagonal crystal structure that corresponds to 100, 110 and 111 plane. All the samples deposited at different temperature are crystalline in nature with lattice constant, (). Scanning electron microscopy (SEM) was carried out to reveal the micro-structural properties of aluminium sulphide thin films material. It was observed that as the wavelength of the incident radiation increases the absorbance of the material decreases. The sample deposited at 353 K recorded the highest absorbance at 380 nm. The sample deposited at 333 K recorded the highest transmittance at 1180 nm. Al2S3 film has a low transmittance less than 30% in the visible wavelength 520–720 nm and less than 60% transmittance in the near infrared wavelength 760–1200 nm which showed that as the wavelength of the incident radiation increases the transmittance of the films increases. The resistivity of the material decreases as the temperature and thickness of the materials increases while the conductivity of the material increases as the temperature and thickness of the material increases. The band gap energy of Al2S3 thin films deposited at (323 K-353 K) as obtained from the plot is given as 2.4-3.0 eV.