Introduction

Synthesis of nanoparticles on the surface and embedded in the matrix by thermal annealing (leading to diffusion of nanoparticles into polymer matrix) and ion beam irradiation is a promising method as reported in the literature [1].The formation of spherical and uniform Pt nanoparticles on SiO2 surface have been reported as a result of 800 keV Kr ions irradiation of thin Pt film [2]. The synthesis of Au nanoparticles at the surface and embedded in the carbon rich matrix by low-energy ion-beam irradiation with 150 keV Ar ions at varying ?uences of thin Au ?lm on the PET substrate has been reported. The isolated Au nanoparticles (45 ± 20 nm) appeared at the surface at the ion ?uence of 5 × 1016 ions cm-2 [3]. Formation of self assembled Au nanoparticles with controlled size and distributions was reported using focused ion beam (FIB) irradiation (5 keV Ga+) of thin Au films on amorphous carbon films [4].    

However, a very limited data is available for the modification of optical properties by ion beam irradiation. The optical energy band gap and crystalline size of polymer nano composite can be controlled by ion beam treatment by controlling beam parameters (current, energy, fluences etc.). The main objective of this work was to study the optical properties of Cadmium Sulphide nano crystalline films on poly (3,4ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) irradiated by Ar ions at various fluences.

Materials and Methods

The samples for the present work were prepared on quartz glass substrates of dimensions: 15 mm x 15 mm x 1mm. Slides were first cleaned in de-ionized (DI) water and acetone to remove the impurities from the surface of the slides. Slides were further cleaned in a solution of trichloroethylene (TCE) for 10 minutes and rinsed in hot water.   A programmable spin coater (Model No. Spin NXG-P1, Apex Equipment, Kolkata, India) was used to prepare the PEDOT: PSS films on quartz glass substrates. The acceleration time (second), rotation time (second) and revolution per minutes (rpm) during spin coating process were 5, 60 and 1500 respectively. The Electron Beam Gun Evaporation system (HINDHIVAC VACUUM COATING UNIT MODEL “12A4D” and an Electron Beam Power Supply Model “EGC-3kW” has been used in the present work to deposit a thin films of germanium (Ge) of different thickness 50 nm, 75 nm and 100 nm on the spin coated surface of PEDOT: PSS. The thickness of the germanium (Ge) film was measured by quartz digital thickness monitor. The samples prepared by electron beam gun system were implanted with 200 keV Ar++ ions using Electron Cyclotron Resonance Ion Sources (ECRIS) at T.I.F.R., Mumbai, India. The samples were implanted for various ion fluences varying from 1 x 1013 to 1 x 1015 ions cm-2 at room temperature. After implantation, the samples were cleaned in electronic grade Trichloroethylene, Acetone and Methanol and rinsed in de-ionized water. The samples were dried and stored in desiccators for characterization. The effect of argon ion implantation on the structural and optical properties of PEDOT:PSS/ Ge composite thin films were investigated  for non implanted and samples implanted with various ion fluencies using Fourier Transform Infrared Spectroscopy (FTIR).

Results

Conclusion

The decrement of transmittance in spectra recorded by Fourier Transform Infrared Spectroscopy was seen in the deposited germanium layer which is less transparent as compared to PEDOT: PSS. Percentage transmittance 56 %, 65 % and 73% were found for samples implanted with 200 keVAr++ ions for various fluences (1 x 1013, 1 x 1014 and 1 x 1015 ions cm-2 respectively).The formation of different types of clusters inside the materials has been found at higher ion fluences.