HMDSO plasma polymerization and thin film optical properties |
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Authors: | Rogrio Pinto Mota Douglas Galvo Steven F Durrant Mrio A Bica De Moraes Socrates de Oliveira Dantas Mauricio Canto |
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Affiliation: | a Departamento de Fisica e Química, Faculdade de Engenharia, UNESP, 12500-000, Guaratinguetá, SP, Brazil b Institute de Física Gleb Wataghin, UNICAMP, 13083-970, Campinas, SP, Brazil c Departamento de Física, Universidade Federal de Juiz de Fora, Juiz de Fora, MG, Brazil |
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Abstract: | Thin films were deposited from hexamethyldisiloxane (HMDSO) in a glow discharge supplied with radiofrequency (rf) power. Actino-metric optical emission spectroscopy was used to follow trends in the plasma concentrations of the species SiH (414.2 nm), CH (431.4 nm), CO (520.0 nm), and H (656.3 nm) as a function of the applied rf power (range 5 to 35 W). Transmission infrared spectroscopy (IRS) was employed to characterize the molecular structure of the polymer, showing the presence of Si-H, Si-O-Si, Si-O-C and C-H groups. The deposition rate, determined by optical interferometry, ranged from 60 to 130 nm/min. Optical properties were determined from transmission ultra violet-visible spectroscopy (UVS) data. The absorption coefficient , the refractive index n, and the optical gap E04 of the polymer films were calculated as a function of the applied power. The refractive index at a photon energy of 1 eV varied from 1.45 to 1.55, depending on the rf power used for the deposition. The absorption coefficient showed an absorption edge similar to other non-crystalline materials, amorphous hydrogenated carbon, and semiconductors. For our samples, we define as an optical gap, the photon energy E04 corresponding to the energy at an absorption of 104 cm?1. The values of E04 decreased from 5.3 to 4.6 as the rf power was increased from 5 to 35 W. |
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Keywords: | Optical properties Plasma processing and deposition |
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