Section 15. Wide band gap materials. III. Silicon carbon alloys Influence of deposition parameters and post-deposition plasma treatments on the photoluminescence of polymorphous silicon carbon alloys V. Suendo a, * , G. Patriarche b , P. Roca i Cabarrocas a a Laboratoire de Physique des Interfaces et des Couches Minces, UMR 7647, CNRS, Ecole Polytechnique, Route de Saclay, 91128 Palaiseau cedex, France b Laboratoire de Photonique et de Nanostructures, UPR20, CNRS, Route de Nozay, 91460 Marcoussis, France Available online 19 April 2006 Abstract We have studied the photoluminescence (PL) of a nanostructured material consisting of silicon nanocrystals embedded in an amor- phous matrix that we call polymorphous silicon carbon (pm-Si 1x C x :H). The presence of silicon nanocrystals in the a-Si 1x C x :H matrix is confirmed by high resolution transmission electron microscopy (HRTEM) as well as by their PL emission features, in particular a strong room temperature emission and a broad spectrum, which are characteristic of silicon nanocrystals. Moreover, the PL intensity was found to be closely related with the number of nanocrystals in the film, which depends on the deposition conditions, in particular the RF power. Possible ways to enhance the PL efficiency and a model of the recombination routes are discussed. Ó 2006 Elsevier B.V. All rights reserved. PACS: 81.07.Bc; 78.67.Bf; 78.55.m; 81.65.Rv Keywords: Polymorphous silicon carbon alloys; Photoluminescence; Silicon nanocrystals; Particle formation; Hydrogen plasma treatment 1. Introduction Among amorphous semiconductor materials, hydroge- nated amorphous silicon carbon (a-Si 1x C x :H) has been studied for optoelectronic applications such as electrolumi- nescent devices [1,2]. However, despite all the efforts car- ried out, the development of this material has not yet translated into commercial applications. Meanwhile, we have developed a new material: hydrogenated polymor- phous silicon (pm-Si:H), which has improved properties with respect to hydrogenated amorphous silicon (a-Si:H), related to the presence of silicon nanocrystals in the amor- phous matrix [3–6]. The incorporation of silicon nanocrys- tals produced in plasma phase has been related to the increase of the order of the amorphous matrix [4]. While strong room temperature PL is well-known to be observed from nanostructured silicon films, such as porous silicon [7] and porous amorphous silicon [8], the PL properties of nanocrystals in pm-Si:H have not yet been exploited. In order to use the embedded nanocrystals as luminescent centers, we have taken advantage of the wider band gap of a-Si 1x C x :H with respect to that of a-Si:H to: (i) achieve a strong confinement of carriers within the crystallites and (ii) reduce the absorption form the matrix. Based on this idea, we have deposited hydrogenated polymorphous sili- con carbon alloys (pm-Si 1x C x :H), which consist of silicon nanocrystals embedded in an a-Si 1x C x :H matrix [9]. This material shows a strong room temperature PL as observed in other systems based on silicon nanocrystals. In this work, we present the relation between the pres- ence of nanocrystals and the PL properties of the films, which includes their dependence on the deposition condi- tions. This study is limited to the effect of the RF power 0022-3093/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2005.12.037 * Corresponding author. Tel.: +33 6 1889 6331; fax: +33 1 6933 3006. E-mail addresses: Veinardi.Suendo@polytechnique.edu, suendo@ gmail.com (V. Suendo), roca@poly.polytechnique.fr (P. Roca i Cabarro- cas). www.elsevier.com/locate/jnoncrysol Journal of Non-Crystalline Solids 352 (2006) 1357–1360