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Self-aggregated Si quantum dots in amorphous Si-rich SiC
Authors:Tzu-Chieh Lo  Ling-Hsuan Tsai  Chih-Hsien Cheng  Po-Sheng Wang  Yi-Hao Pai  Chih-I Wu  Gong-Ru Lin
Institution:Graduate Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University, No. 1, Roosevelt Road Sec. 4, Taipei 10617, Taiwan, ROC;Nagoya University;Hokkaido University;Tokyo Institute of Technology;Gifu University;Hiroshima University
Abstract:Amorphous silicon quantum dots (Si-QDs) self-aggregated in silicon-rich silicon carbide are synthesized by growing with plasma-enhanced chemical vapor deposition on (100)-oriented Si substrate. Under the environment of Argon (Ar)-diluted Silane (SiH4) and pure methane (CH4), the substrate temperature and RF power are set as 350 °C and 120 W, respectively, to provide the Si-rich SiC with changing fluence ratio (R = CH4 ]/SiH4] + CH4]). By tuning the fluence ratio from 50% to 70%, the composition ratio x of Si-rich Si1 ? xCx film is varied from 0.27 to 0.34 as characterized by X-ray photoelectron spectroscopy (XPS), which reveals the component of Si2p decreasing from 66.3 to 59.5%, and the component of C1s increasing from 23.9% to 31% to confirm the formation of Si-rich SiC matrix. Annealing of the SiC sample from 650 °C to 1050 °C at 200 °C increment for 30 min induces the very tiny shift on the wavenumber of the crystalline Si (c-Si) related peak due to the precipitation of Si-QDs within the SiC matrix, and the Raman scattering spectra indicate a broadened Raman peak ranging from 410 to 520 cm? 1 related to the amorphous Si accompanied with the significant enhancement for Sisingle bondC bond related peak at 980 cm? 1. From the high resolution transmission electron microscopy images, the critical temperature for Si-QD precipitation is found to be 850 °C. The self-assembly of the crystallized Si-QDs with the size of 3 ± 0.5 nm and the volume density of (3 ± 1) × 1018 (#/cm3) in Si-rich SiC film with R = 70% are observed after annealing at higher temperature.
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