Energy transfer from luminescent centers to Er 3+ in erbium-doped silicon-rich oxide films
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NANO EXPRESS
Open Access
Energy transfer from luminescent centers to Er3+ in erbium-doped silicon-rich oxide films Lu Jin1,2, Dongsheng Li1,2*, Luelue Xiang1,2, Feng Wang1,2, Deren Yang1,2 and Duanlin Que1,2
Abstract The energy transfer mechanism between luminescent centers (LCs) and Er3+ in erbium-doped silicon-rich oxide (SROEr) films prepared by electron beam evaporation is investigated. Intense photoluminescence of the LCs (weak oxygen bonds, neutral oxygen vacancies, and Si=O states) within the active matrixes is obtained. Fast energy transfer from Si=O states to Er3+ takes advantage in the SROEr film and enhances the light emission from Er3+. The introduction of Si nanoclusters, which induces the Si=O states and facilitates the photon absorption of the Si=O states, is essential to obtain intense photoluminescence from both Si=O states and Er3+. Keywords: Luminescence centers; Silicon nanoclusters; Erbium ion; Energy transfer; Silicon-rich oxide
Background In the recent years, a great amount of researchers have focused on the luminescent materials of Si-based light sources to obtain efficient light emission, which is a critical step for the achievement of the Si-based optical interconnections [1]. These materials include silicon-rich oxide (SRO) [2-6], silicon-rich nitride [6,7], Ge-on-Si luminescent materials [8], and rare-earth-doped Si-based materials [9-14]. Among all these Si-based materials, erbium-doped SRO (SROEr) films have attracted a great research interest in these years as the 1.54-μm luminescence of Er3+ is compatible with both the optical telecommunication and the Si-based microphotonics [11-18]. The excitation mechanism of Er3+ in SROEr has been basically discussed, while three indirect excitation mechanisms of Er3+ have been proposed in the literatures: (1) slow energy transfer process (τr = approximately 4 to 100 μs) from exciton recombination in silicon nanoclusters (Si NCs) followed by internal relaxation to Er3+ [11,16,18,19], (2) fast energy transfer process (nanosecond and faster) between hot carriers inside the Si NCs and Er3+ [20,21], (3) fast energy transfer process (very fast, sub-nanosecond) from luminescent centers (LCs) in the SROEr matrixes to Er3+ [17]. * Correspondence: [email protected] 1 State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027, People’s Republic of China 2 Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, People’s Republic of China
The Si NCs acting as the classical sensitizers embedded in the SROEr films can provide large excitation cross-section and efficient energy transfer to Er3+, from which the luminescence of Er3+ can be improved significantly [11]. Both light emitting diodes [12] and optical gain [13] have been achieved from the Si NC-sensitized SROEr systems. However, the luminescence intensity and optical gain of Er3+ are still limited due to the low fraction of Er3+ ions sensitized by the Si NCs [15]. Moreover, the confined carrier absorption (CCA) process that exists in the Si NC-sen
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