The characteristics and gas-sensing property of bis[phthalocyaninato] rare earth complexes based charge-flow transistor

A new kind of sandwich-like bis[2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyaninato] rare earth complexes RE[Pc∗]2 (Pc∗=Pc(OC8H17)8, RE=Sm, Pr, Er) are used to film-forming material. Pure RE[Pc∗]2 and mixture of RE[Pc∗]2 and auxiliary film-forming solvents—stearic acid (SA) and octadecanol (OA) deposited from both pure water and 10−4 M Cd2+ subphases are investigated. It is found that a mixture of Sm[Pc∗]2 and OA forms an excellent material for the fabrication of gas-sensing LB film by studying the film-forming characteristics. A new gas sensor has been fabricated by incorporating the different multilayer LB films into the gate electrode of a MOSFET, forming an array of charge-flow transistor (CFT). On the application of a gate voltage (VGS), greater than the threshold voltage (VTH), a delay is observed in the response of the drain current. It is due to the time taken for the resistive gas-sensing film to charge up to VGS. This delay characteristic has been found to depend on the concentrations of NO2, suggesting that the CFT device can be used as an effective gas sensor. Results are presented of studies the dc operating and turn-on characteristics as well as gas-sensing property, showing that the device can detect reversibly concentration of NO2 gas down to 5 ppm at room temperature.