Conduction mechanism for sputtered a-C:H based structures I. Lazar, G. Lazar * Bacau University, Calea Marasesti 157, 600115 Bacau, Romania Received 16 July 2004; received in revised form 21 February 2006 Available online 3 May 2006 Abstract Metal–insulator–metal (MIM) and metal–insulator–semiconductor (MIS) structures fabricated by magnetron sputtering deposition of insulating hydrogenated amorphous carbon are analyzed by measuring their current–voltage characteristics in order to find the con- duction mechanism. For MIM structures, the linearity of the logarithmic dependencies between current density and electric field intensity (log J–log E) for higher fields indicate a space charge limited current (SCLC) conduction mechanism. The calculated values of the effective mobility are in agreement with other literature results. For MIS structures, the power-law dependence between current and voltage also indicate a space–charge limited currents based conduction mechanism. Ó 2006 Elsevier B.V. All rights reserved. PACS: 73.61.Jc; 73.40.Rw; 73.40.Qv Keyword: Electrical and electronic properties 1. Introduction In the last years, much attention has been given to amor- phous carbon films owing to their interesting properties. Hydrogenated amorphous carbon (a-C:H) films have attracted considerable attention due to their wide range of technological uses, for example, as low wearing and hard low-friction coatings in engineering and medical applica- tions [1]. Amorphous carbon has a particular potential in magnetic head devices for hard disks, as a hard, low wear or anti-corrosion coating [2]. Amorphous carbon films, both hydrogenated and hydrogen-free (a-C), have shown in recent years to be suitable for electronic applications [3]. Its electronic properties have raised interest for field emission and, more recently, for dielectric applications such as low k planarization layers and non-volatile memories [4,5]. The potential advantage of a-C:H over other insula- tors lies in the higher thermal conductivity, which is critical as device dimensions decrease [6]. The usefulness of semi- conducting amorphous carbon films for an electronic appli- cation has been enhanced by the demonstration of n-type doping by nitrogen and phosphorus or p-type doping by boron [7,8]. Due to the allotropic character of carbon, which can take either sp 3 or sp 2 electronic hybridisation, the hydrogen incorporated in the material during deposition is then known to control the respective proportions of the sp 3 and sp 2 carbon sites, and consequently the network C–C connection in the a-C:H films [9]. Such a microstructure, which plays a crucial role in the observed properties, is found to be deeply dependent on the techniques and condi- tions of depositions [10]. Among the various deposition techniques, room temperature radio frequency (RF) mag- netron sputtering is a very efficient technique for the pro- duction of amorphous carbon films, since depending on the deposition conditions, the film properties may vary from soft-polymer-like (high hydrogen content and high sp 3 proportion) and graphitic (low hydrogen content and high sp 2 proportion) forms to hard diamond-like a-C:H which has mixed bonding, a low hydrogen content and a large degree of cross linking and structural rigidity [11–14]. 0022-3093/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2006.02.044 * Corresponding author. Tel.: +40 234576316. E-mail address: glazar@ub.ro (G. Lazar). www.elsevier.com/locate/jnoncrysol Journal of Non-Crystalline Solids 352 (2006) 2096–2099