Correlation between Surface Charge Accumulation and Excitation Intensity Dependent Red-Shifted Micro-Photoluminescence o
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A4.37.1
Correlation between Surface Charge Accumulation and Excitation Intensity Dependent Red-Shifted Micro-Photoluminescence of Si-Implanted Quartz with Embedded Si Nanocrystals Chun-Jung Lin, Kuo-Cheng Yu, Hao-Chung Kuo, Miao-Jia Ou-yang and Gong-Ru Lin* Institute of Electro-Optical Engineering, National Chiao Tung University, 1001, Ta Hsueh Rd., Hsinchu, Taiwan 300, R.O.C. ABSTRACT The excitation intensity dependency of nanocrystallite Si (nc-Si) related micro-photoluminescence (µ-PL) from the multi-recipe Si-implanted quartz is characterized. The µ-PL at 724 nm contributed by nc-Si with 3-4 nm diameter is maximized after annealing at 1100oC for 3 hours. By increasing the excitation intensity from 10 kW/cm2 to 300 kW/cm2, the µ-PLs of 1-hr and 3-hr annealed quartz significantly red-shift from 723 nm to 725 nm and from 724 nm to 735 nm, respectively. This can be explained by the anomalous quantum stark effect due to a surface electric field oriented from photo-ionized nc-Si dots to quartz surface. After 1-hr illumination at power of 300 kW/cm2, the µ-PL peak wavelength of 3-hr annealed sample is further red-shifted by 2.5 nm. By measuring the accumulated surface charges built up during optical excitation process, the correlation between excitation -intensity dependent PL wavelength red-shift and the photo-ionized nc-Si surface electric-field related quantum stark effect is primarily elucidated. INTRODUCTION Si ion implantation has recently been emerged as an alternative technique to synthesize Various Si nanocrystals (nc-Si) in SiO2 matrix due to its processing flexibility. + photoluminescence (PL) bands from Si-implanted SiO2 materials (SiO2:Si ) were reported. The neutral oxygen vacancy (NOV, or chemically denoted as O3≡Si–Si≡O3) with PL at 410-460 nm1, and the E’δ defects (the precursor of nc-Si, denoted as Si↑Si–Si) with PL at 520-550 nm2 have been identified as the principle defects in the as implanted SiO2:Si+ materials. The high-temperature annealing of SiO2:Si+ usually leads to the quenching of defects and the formation of nc-Si. This results in a dominated PL band at near infrared wavelengths of 700-900 nm. The nc-Si related PL wavelength is strongly dependent with the size of nc-Si. Such a Si-rich SiO2:Si+ material with self-assembled Si quantum dots (QDs) has attracted considerable interests for fabrication of novel light-emitting and charge-storage devices. Later on, the electric-field dependent luminescence from materials containing QDs due to the change in charge distribution beneath or inside the QDs were provided, which has been attributed to the quantum-confined Stark effect.3,4 These investigations indicate that the sign of Stark shift strongly depends on the change in external electric field or the built-in dipole momentum of the single QD.5,6 Sheng et al.7 observed an anomalous Stark shift of the stacked InAs/GaAs self-assembled QD structure in which the hole states were drastically modified by three-dimensional strain field. Micro-PL (µ-PL) characterizations of QDs further reveal some extrao
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