Effect of Argon-Oxygen Flow Rate Ratio in Magnetron Sputtering on Morphology and Hygroscopic Property of SnO₂ Thin Film

摘要

Thin films of tin dioxide (SnO2) were deposited by DC magnetron sputtering on quartz substrate atroom temperature in different argon-oxygen gas flow rate ratio i.e. Ar:O2 = 100:20 sccm, 90:30 sccm,80:40 sccm, 70:50 sccm and 60:60 sccm. X-ray diffraction (XRD) patterns show that as-depositedSnO2 thin films are amorphous. Post-annealing process in air at 500C for 1 h resulted insemicrystalline SnO2 that has tetragonal structure with spatial group of P42/mnm (136). Transmissionelectron microscope (TEM) analysis confirmed that the semicrystalline nature of the films afterannealing was due to crystal growth. The surface morphology studied by field emission scanningelectron microscope (FESEM) shows that the increase of argon flow rate lead to increment of thethickness and the crack size on the films surface. From the humidity response test, SnO2 thin film thatwas deposited at maximum argon flow and minimum oxygen flow rate i.e Ar:O2 = 100:20 showednegative sensitivity gradient. This shows that it has an opposing behaviour from n-type semiconductordue to its non-stoichiometric state caused by high oxygen vacancies. While SnO2 thin film that wasdeposited at minimum argon flow and maximum oxygen flow rate i.e. Ar:O2 = 60:60 showed thehighest sensitivity (positive gradient) with slight fluctuation of repeatability. It was determined that atargon-oxygen flow rate ratio of Ar:O2 = 70:50 yielded a SnO2 thin film with high sensitivity (positivegradient) and good repeatability towards relative humidity showing it is environmentally stable.