title: Identification of the Chemical Bonding Prompting Adhesion of a-C:H Thin Films on Ferrous Alloy Intermediated by a SiCx:H Buffer Layer.
abstract: Amorphous carbon (a-C) and several related materials (DLCs) may have ultralow friction coefficients that can be used for saving-energy applications. However, poor chemical bonding of a-C/DLC films on metallic alloys is expected, due to the stability of carbon-carbon bonds. Silicon-based intermediate layers are employed to enhance the adherence of a-C:H films on ferrous alloys, although the role of such buffer layers is not yet fully understood in chemical terms. The chemical bonding of a-C:H thin films on ferrous alloy intermediated by a nanometric SiCx:H buffer layer was analyzed by X-ray photoelectron spectroscopy (XPS). The chemical profile was inspected by glow discharge optical emission spectroscopy (GDOES), and the chemical structure was evaluated by Raman and Fourier transform infrared spectroscopy techniques. The nature of adhesion is discussed by analyzing the chemical bonding at the interfaces of the a-C:H/SiCx:H/ferrous alloy sandwich structure. The adhesion phenomenon is ascribed to specifically chemical bonding character at the buffer layer. Whereas carbon-carbon (C-C) and carbon-silicon (C-Si) bonds are formed at the outermost interface, the innermost interface is constituted mainly by silicon-iron (Si-Fe) bonds. The oxygen presence degrades the adhesion up to totally delaminate the a-C:H thin films. The SiCx:H deposition temperature determines the type of chemical bonding and the amount of oxygen contained in the buffer layer.
authors.affiliation: †Centro de Ciências Exatas e Tecnologia, Universidade de Caxias do Sul, 95070-560 Caxias do Sul, RS, Brazil.
authors.forename: F
authors.initials: F
authors.lastname: Cemin
authors.affiliation: †Centro de Ciências Exatas e Tecnologia, Universidade de Caxias do Sul, 95070-560 Caxias do Sul, RS, Brazil.
authors.forename: L T
authors.initials: LT
authors.lastname: Bim
authors.affiliation: †Centro de Ciências Exatas e Tecnologia, Universidade de Caxias do Sul, 95070-560 Caxias do Sul, RS, Brazil.
authors.forename: L M
authors.initials: LM
authors.lastname: Leidens
authors.affiliation: ‡Instituto de Física "Gleb Wataghin", Universidade Estadual de Campinas, 13083-970 Campinas, SP, Brazil.
authors.forename: M
authors.initials: M
authors.lastname: Morales
authors.affiliation: §Instituto de Física, Universidade Federal do Rio Grande do Sul, 91509-970 Porto Alegre, RS, Brazil.
authors.forename: I J R
authors.initials: IJ
authors.lastname: Baumvol
authors.affiliation: ‡Instituto de Física "Gleb Wataghin", Universidade Estadual de Campinas, 13083-970 Campinas, SP, Brazil.
authors.forename: F
authors.initials: F
authors.lastname: Alvarez
authors.affiliation: †Centro de Ciências Exatas e Tecnologia, Universidade de Caxias do Sul, 95070-560 Caxias do Sul, RS, Brazil.|∥Plasmar Tecnologia Ltda., 95030-775 Caxias do Sul, RS, Brazil.
authors.forename: C A
authors.initials: CA
authors.lastname: Figueroa
keywords: DLC; XPS; adhesion; buffer layer; chemical bonding; hydrogenated amorphous carbon; hydrogenated silicon carbide; interface