Optical and electrical properties of nanostructured heterojunction (Au|PdPc|ClAlPc|Al) and using as O₂ sensor

Applied Physics Division, Physics Department, Tarbiat Moallem University, 49 Mofateh Avenue, Tehran, Islamic Republic of Iran

^a email: Ebrahim_kk@yahoo.com

Received: 29 September 2010
Revised: 26 April 2011
Accepted: 6 June 2011
Published online: 18 August 2011

Abstract

Nanostructure thin films and sandwich devices of palladium phthalocyanine (PdPc) and chloro-aluminum-phthalocyanine (ClAlPc) were prepared by thermal evaporation technique. Optical and struc- tural properties of nanostructure thin films were investigated by XRD, SEM and optical absorption. The SEM images demonstrated PdPc (40–60 nm) and ClAlPc (30–50 nm) nanostructures. XRD pat- terns showed that thin films are in α-phase at room temperature. Also, optical bandgap energy of thin films was calculated by optical absorption spectra. Heterojunction (Au|PdPc|ClAlPc|Al) and single layer (Au|PdPc|Al and Au|ClAlPc|Al) devices were fabricated. Electrical measurements demonstrated the semi-conducting and photo-conducting behavior of thin films. After that, devices were exposed to different concentrations of O₂ at 300 K and 350 K and conductivity of thin films was increased on exposure to O₂ . Heterojunction devices were more sensitive than other thin films and had better response and reversibility in comparison with single layer devices at 350 K. Finally, 10% O₂ was mixed with different percentages of relative humidity and all results showed that the conductivity of thin films is reduced on exposure to O₂ mixed to humidity.