AVS 49th International Symposium
    Organic Films and Devices Wednesday Sessions
       Session OF+EL-WeP

Paper OF+EL-WeP9
Mg-Phthalocyanine Thin Films with High Sensitivity for Chlorine Gas

Wednesday, November 6, 2002, 11:00 am, Room Exhibit Hall B2

Session: Organic Films and Devices
Presenter: T. Miyata, Kanazawa Institute of Technology, Japan
Authors: T. Miyata, Kanazawa Institute of Technology, Japan
S. Kawaguchi, Kanazawa Institute of Technology, Japan
T. Minami, Kanazawa Institute of Technology, Japan
Correspondent: Click to Email
There has been considerable interest in the study of organic substances such as phthalocyanines in thin film form for use as the active layer in gas sensor devices. In particular, the electronic properties of metal phthalocyanine (MPc) thin films are known to be affected by the presence of a foreign gas. Recently, we have demonstrated newly developed high-sensitivity chlorine (Cl@sub 2@) gas sensors using Cu-phthalocyanine (CuPc) thin films. However, these CuPc thin film gas sensors still have several unsolved problems such as low sensitivity at operating temperatures above 150@super o@C and the necessity of a heat treatment process for repeated operation. In this paper, we introduce newly developed chlorine gas sensors that can be operated at high temperatures using Mg-phthalocyanine (MgPc) thin films. The Mg-phthalocyanine thin films (thickness from 30 to 180 nm) were evaporated onto substrates; Au thin films were deposited as electrodes. The substrate temperature was varied from RT to 180@super o@C. Gas sensitivity is defined as ratio (I-I@sub 0@)/I@sub 0@. Here, I@sub 0@ and I are the currents through the sensors before and after gas introduction, respectively. The sensor resistance decreased when exposed to chlorine gas; MgPc thin film gas sensors exhibited high sensitivity at the operating temperatures as high as 230@super o@C. The characteristics of MgPc thin film sensors were strongly dependent on the preparation conditions of the MgPc thin films. For example, sensitivity increased as the substrate temperature of the MgPc thin films was increased from RT to 180@super o@C: maximum sensitivity at a thin film deposition temperature of 180@super o@C. At an operating temperature of 200@super o@C, the sensitivity of the optimized MgPc thin film gas sensor linearly increased with the Cl@sub 2@ gas concentration in the range of 0.35 to 35 ppm.