Variation Resistance of different operation temperature of NO2 and NH3 gases for the Ag-doped SiC gas sensor

Abstract

A pure and Ag-doped silicon carbide (SiC) films on the p-type silicon (110) wafers were prepared with various dopant ratios (1, 3, 5 and 7%) using pulsed laser deposition technique (PLD) with the Nd: YAG laser (= 1064 nm, 500 mJ, 6 Hz). The samples were deposited under high pressure up to (10−4 mbar) at a substrate temperature of 250 °C. The thin films have been examined for (NO2 and NH3) sensing at different operating temperatures. The maximum sensitivity of pure SiC of NH3 gas about (12%) at 200 oC and (14.42%) for NO2 gas at 100°C while the maximum sensitivity of Ag-doped samples about (24.39%) of NH3 gas at 200°C for (1%wt) and (62.98%) of NO2 gas at 25°C for (3%wt). For the pure sample, we found that the fastest response time was (18.9 s, 22.5 s) for NH3 and NO2 gases at (300 °C,100 °C), respectively, while for impure samples (3% wt) about (12.6 s, 13.5 s) of NH3 and NO2 at 100°C. The results also showed that the lowest recovery time for the pure film was 33.3 s for NH3 gas at 100°C, while for NO2 gas its value was (30.6 s) at 200°C. Also for the SiC: Ag (3% wt, 5%), it was found that the fastest recovery time was about (45 s) for NH3 gas at 25 °C and (41.4 s) for NO2 gas at 100 °C.