Ion Beam Enhanced Formation and Luminescence of Si Nanoclusters from a -SiO x
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Ion Beam Enhanced Formation and Luminescence of Si Nanoclusters from a-SiOx Yohan Sun1, Se-Young Seo1, Jung H. Shin1, T. G. Kim2, C. N. Whang2 and J. H. Song3 1 Dept. of Physics, Korea Advanced Institute of Science and Technology (KAIST) 373-1 Kusung-dong, Yusung-Gu, Taejon Korea 2 Dept. of Physics, Yonsei University, Seoul, Korea 3 Advanced Analysis Center, Korea Institute of Science and Technology, Seoul, Korea ABSTRACT The effect of ion beams on the formation of Si nanoclusters from a-SiOx films and their luminescence properties is investigated. a-SiOx films with Si content ranging from 33 to 50 at. % were deposited by Electron Cyclotron Resonance Plasma Enhanced Chemical Vapor Deposition (ECR-PECVD) of SiH4 and O2. Prior to anneal, some samples were implanted with 380 keV Si to a dose ranging from 5.7 × 1014 cm-2 to 5.7 × 1016 cm-2. All films were rapid thermal annealed under flowing Ar environment, and hydrogenated after anneals to passivate defects and to enhance the luminescence of Si nanoclusters. For films with Si content less than 40 at. %, ion beam slightly reduces the photoluminescence (PL) intensity and induces a slight blueshift of the luminescence. For films with Si content greater than 40 at. %, ion beam greatly increases the PL intensity. Based on the effect of the ion beams dose and the ion specie, we propose that ion beams damage greatly promotes nucleation of small Si clusters from the a-SiOx matrix. INTRODUCTION Spurred on by their novel properties and functionalities due to quantum confinement effects, Si nanocrystals have been the subject of intense study [1-3]. A widely used method to prepare a dense and robust array of well-passivated Si nanocrystals is precipitating them out of SiOx (x < 2) [4-6]. While this method has the advantage of being compatible with standard Si processing technology, it often requires long anneals at temperatures in excess of 1100 °C [4], which is undesirable from the process point of view. The thermal budget can be reduced by increasing the excess Si content of the a-SiOx films, but this leads to larger Si cluster sizes and lower luminescence efficiencies. Thus, the controllability of the formation of Si nanoclusters and their luminescence properties is limited once the Si content of the a-SiOx is fixed. In this article, we investigate the effect of ion irradiation prior to anneals upon the formation and luminescence properties of Si nanoclusters from a-SiOx films deposited by electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD) of SiH4 and O2. We find that the effects of ion irradiation are dependent upon the Si content. For Si-poor a-SiOx films, the ion beam slightly reduces the PL intensities, but also blueshifts the PL spectra. For Si-rich a-SiOx films, the ion beam greatly increases the PL intensities. Based on the results, we identify ion beam induced damage as a possible candidate responsible for the observed effects. EXPERIMENTAL DETAILS Films were deposited by ECR-PECVD of SiH4 and O2. The base pressure and the deposition pres
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