Diamond and Related Materials 13 (2004) 923–928 0925-9635/04/$ - see front matter  2003 Elsevier B.V. All rights reserved. doi:10.1016/j.diamond.2003.12.014 Raman and photoluminescence analysis of CVD diamond films: influence of Si-related luminescence centre on the film detection properties M.G. Donato , G. Faggio , G. Messina *, S. Santangelo , Marco Marinelli , E. Milani , G. Pucella , a a a, a b b b G. Verona-Rinati b INFM—Dipartimento di Meccanica e Materiali, Facolta di Ingegneria, Universita di Reggio Calabria, Via Graziella, Localita Feo di Vito, a ` ` ` 89100 Reggio Calabria, Italy INFM—Dipartimento di Ingegneria Meccanica, Universita di Roma ‘Tor Vergata’, Italy b ` Abstract The performance of detectors based on CVD diamond films strongly depends on the material quality, which, in turn, is extremely sensitive to even slight variations of the deposition conditions. In this work, a careful Raman and photoluminescence (PL) study has been carried out on diamond films grown on Si substrates by microwave plasma CVD under nominally identical deposition conditions, but exhibiting, quite surprisingly, different detection sensitivity. Micro-PL measurements performed on the growth surface and on the cross-section of the samples have shown higher incorporation of Si impurities in films having lower detection performance. Optical microscopy on the nucleation side of such films has evidenced a lower nucleation density, leading to diamond grains of greater size, but also to higher incorporation of Si atoms. Thus, a greater grain size does not necessarily guarantee a higher film quality, if the nucleation density is low. On the basis of these results, the nucleation density is identified as the ‘hidden’ variable in the growth process of our CVD diamond films, determining, ultimately, their detection sensitivity.  2003 Elsevier B.V. All rights reserved. Keywords: CVD diamond; Raman spectroscopy; Photoluminescence; Si-related defects 1. Introduction Because of the many exceptional properties of natural diamond, synthetic diamond films grown by various chemical vapour deposition (CVD) techniques have a great potential for advanced applications in several fields. Among the various applications, particle detection is particularly demanding in terms of film quality. In fact, an efficient particle detection requires high drift lengths of the carriers produced by the ionising particles, which may be strongly reduced by the presence of impurities, defects and grain boundaries. Slight varia- tions of the deposition parameters may affect even strongly the phase purity and the concentration of crystallographic defects of CVD diamond films. At present, therefore, the sensitivity of diamond-based par- ticle detectors is strongly influenced by the growth conditions. The synthesis of high-purity material with *Corresponding author. Tel.: q39-0965-875485yq39-0965- 875317; fax: q39-0965-875201. E-mail address: messina@unirc.it (G. Messina). well-controlled and highly reproducible characteristics represents a crucial step for a successful utilisation of CVD diamond in particle detection applications. The possibility of producing high quality films is strictly connected to a better understanding of the influence of the growth conditions on the microscopic structure of the films. Characterisation studies, clarifying the relationships among growth conditions, structure and physical properties of CVD diamond films, constitute a prerequisite for the synthesis of ‘detector-grade’ material. In this work, optical techniques such as Raman spectroscopy and photoluminescence (PL) were employed to investigate the nature and distribution of defects in CVD diamond films grown on silicon sub- strates by microwave plasma enhanced chemical vapour deposition. In particular, careful micro-PL measurements were carried out to shed light on the causes of the different sensitivity of particle detectors built using diamond films grown under nominally identical con- ditions.