Optimized O/Si Composition Ratio for Enhancing Si Nanocrystal Based Luminescence in Si-rich SiO x Grown by PECVD with Ar
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1066-A18-11
Optimized O/Si Composition Ratio for Enhancing Si Nanocrystal Based Luminescence in Si-rich SiOx Grown by PECVD with Argon Diluted SiH4 Chung-Hsiang Chang1, Chin-Hua Hsieh2, Li-Jen Chou2, and Gong-Ru Lin1 1 Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, No. 1, Roosevelt Rd. Sec. 4, Taipei, 10617, Taiwan 2 Department of Materials Science and Engineering, National Tsing Hua University, No. 101, Section 2, Kuang Fu Rd., Hsinchu, 300, Taiwan ABSTRACT Effect of O/Si composition ratio on near-infrared photoluminescence (PL) of PECVD grown Si-rich SiOX after 1100oC annealing are analyzed by Rutherford backscattering (RBS) and Fourier-transformed infrared spectroscopy (FTIR) to show nonlinear relationship with strongest PL at 760 nm at optimized O/Si = 1.24, total Si concentration of 44.6 atom.%, and N2O/SiH4 fluence ratio of 4.5. A nearly Gaussian function of the normalized PL intensity vs. O/Si composition ratio has been observed due to the significant variation on the Si nanocrystals size with the density of the excessive Si atoms. INTRODUCTION Versatile technologies have been proposed for synthesizing Si-rich oxide (SiOX) or nitride (SixNy) with buried Si nanocrystals (nc-Si), such as electron-beam evaporation, rf-magnetron sputtering, Si-ion implantation, and plasma-enhanced chemical-vapor deposition (PECVD) [1-4]. The nc-Si related room-temperature PL obtained from electrochemically etched porous Si, PECVD-grown Si-rich SiO2, and Si-ion-implanted SiO2 (SiO2:Si+) has stimulated comprehensive investigations on versatile nc-Si based light-emitting devices. The most intriguing synthesis is the PECVD deposition associated with subsequent heat treatment, since it enables the easy deposition of a Si-rich SiOx film with a sufficiently high density of excess Si atoms by controlling the fluence of reactant gases. As SiO is thermodynamically less stable than the Si and SiO2 phases, thermal annealing treatment leads to the formation of the silicon particles, as shown in a previous study [5]. Besides, Surface passivation techniques, such as oxidation and hydrogenation [5-7], have been applied to decrease defects and increase the PL efficiency. Cheylan and Elliman [7] studied the effect of hydrogen on the photoluminescence of Si nanocrystals embedded after the sample was exposed in forming gas (95% N2 + 5% H2, 500oC, 1 h) because of the hydrogen passivation of non-radiative defects in nanocrystals. Many researchers studied the reaction between Si–SiO2 interface with atomic hydrogen or molecular hydrogen [8-9]. However, there are few detailed studies on the correlation between the N2O/SiH4 fluence ratio and the O/Si composition ratio for optimizing the nc-Si precipitation. In this work, the Rutherford backscattering (RBS), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FTIR), X-ray Photoelectron spectroscopy (XPS) and near-infrared PL are employed to study the effects of the N2O/SiH4 fluence ratio on the com
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