Gas-sensing properties of oxide semiconductors improves by using then in nanocrystalline forms. The sensitivity of gas-sensor has also been modified by adding metals or metal oxides as catalytic agents. Using the In2O3 and Ag nanoparticles as the precursor; In2O3: Ag composite nanoparticle layers have been grown. It has been demonstrated that a decreasing particle size leads to an increased sensitivity and a decreased response time. At C2H5OH concentration of 1000 ppm in air and at an operating temperature of 400 C, sensitivity and response time of 325 and 8 s, respectively have been achieved...