Thin polymer films prepared by plasma immersion ion implantation and deposition Elidiane C. Rangel a, * , Paulo A.F. Silva b , Roge ´rio P. Mota b , Wido H. Schreiner c , Nilson C. Cruz a a Laborato ´rio de Plasmas Tecnolo ´gicos, UNESP-Unidade Diferenciada Sorocaba/Ipero ´, 18087 180 Sorocaba, SP, Brazil b Laborato ´rio de Plasmas, Departamento de Fı ´sica e Quı ´mica, UNESP, 12516 180 Guaratingueta ´, SP, Brazil c Laborato ´rio de Superfı ´cies e Interfaces, Departamento de Fı ´sica, UFPR, 81531 990 Curitiba, PR, Brazil Received 16 November 2002; received in revised form 23 July 2004; accepted 28 July 2004 Available online 11 September 2004 Abstract This work describes an investigation of the properties of polymer films prepared by plasma immersion ion implantation and deposition. Films were synthesized from low pressure benzene glow discharges, biasing the samples with 25 kV negative pulses. The total energy deposited in the growing layer was varied tailoring simultaneously pulse frequency and duty cycle. The effect of the pulse characteristics on the chemical composition and mechanical properties of the films was studied by X-ray photoelectron spectroscopy (XPS) and nanoindentation, respectively. Analysis of the deconvoluted C 1s XPS peaks demonstrated that oxygen was incorporated in all the samples. The chemical modifications induced structural reorganization, characterized by chain cross-linking and unsaturation, affecting material properties. Hardness and plastic resistance parameter increased under certain bombardment conditions. An interpretation is proposed in terms of the total energy delivered to the growing layer. D 2004 Elsevier B.V. All rights reserved. PACS: 52.75R; 81.15G Keywords: Plasma immersion ion implantation and deposition; Mechanical properties; Chemical composition 1. Introduction Plasma polymer films are versatile materials since one can select their composition, thickness and hence their properties through the control of the deposition parameters (plasma composition, frequency, power, pressure, etc). In addition, the overall process is very simple and cost- effective, even for large-scale production. As many polymer films are mechanically fragile, however, some technological applications are restricted. Polymer films are soft and present low resistance to scratching. Furthermore, the adhesion to many substrates is weak and considerable stress may be generated during the deposition process. This factor limits the maximum thickness of the layer and sometimes its application. A way of changing polymer properties is through post- deposition treatment by ion implantation [1]. This technique is well established and frequently performed in ion implanters, which promote implantation with high purity, uniformity and repeatability. Ion implanters, however, are expensive, sophisticated and the scaling-up to commercial production is complicated. Plasma immersion ion implantation, PIII, developed by Conrad [2] and Tendys [3], is an alternative method for the ion bombardment of solids. The sample is placed directly in contact with the ion source, the plasma, and polarized with high voltage negative pulses. Positive ions from the glow are attracted and implanted in the biased target [2,3]. The degree of modification induced by this treatment depends on the ion energy and mass, dose, incidence angle and can be adjusted by the pulse characteristics and plasma parameters [4]. 0040-6090/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.tsf.2004.07.078 * Corresponding author. Laboratœrio de Plasmas Tecnolœgicos, Uni- versidade Estadual Paulista-UNESP, Av. Tres de Marco, 511, 18087 180 Sorocaba, Brazil. Tel.: +55 1532383404; fax: +55 152282842. E-mail address: elidiane@sorocaba.unesp.br (E.C. Rangel). Thin Solid Films 473 (2005) 259 – 266 www.elsevier.com/locate/tsf