Comparison studies of thermally evaporated PbPc and CuPc thin films

Abstract

In this research work attention has been given to Lead Phthalocyanine (PbPc) and Copper Phthalocyanine because of its characteristic structural and electrical properties. Lead and Copper Phthalocyanine is an attractive material for device applications in various field such as Opto electronics, gas sensors, Organic Light Emitting Devices (OLEDs), Field Effect Transistors (FETs), etc.The thin film of Lead Phthalocyanine (PbPc) and Copper Phthalocyanine (CuPc) on glass are prepared by Vacuum deposition method. Deposition of PbPc and CuPc on pre-cleaned glass substrates under the pressure of 10-6 Torr are achieved by slowly varying the current. The rate of evaporation is properly controlled and maintained constant during all the evaporations. The thicknesses of the films are 150 nm, 300 nm and 450 nm on glass substrate. The sample of thickness 450 nm is annealed at 323 K and 373 K temperature. The structural and compositional analysis of the PbPc and CuPc thin films were investigated by X-Ray Diffraction (XRD), Energy Dispersive Analysis using X-Rays (EDAX), Fourier Transform Infrared spectroscopy (FTIR) for different thickness and annealed temperature. XRD analysis confirmed that thermally evaporated PbPc and CuPc films at room temperature are of monoclinic nature at lower thickness and a mixture of monoclinic and triclinic nature at higher thicknesses. These evaporated films are polycrystalline in nature. Thickness increases, grain size increases and defects like dislocation density and strain decreases due to the improvement in crystallinity in the films. From the XRD patterns at different annealed temperature it is concluded that as temperature increases the number of peaks for triclinic phase increases. Annealing at 373 K changes the structure to triclinic with (100) as the direction of preferential orientation.