Optical Properties of Si and Ge/Si Nanocrystals in Silicon Oxide Matrix
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0958-L10-28
Optical Properties of Si and Ge/Si Nanocrystals in Silicon Oxide Matrix Shin-ichiro Uekusa and Atsuhiko Kushida Science and Technology, Meiji University, A816 1-1-1 Higashimita Tama-ku, Kawasaki-shi, 214-8571, Japan
ABSTRACT The contribution of oxide-related emission in Photoluminescence (PL) spectra from Ge and Si nanocrystals embedded in silicon oxide (Ge/Si-SiO2) and Si nanocrystals embedded in silicon oxide (Si-SiO2) thin film prepared by RF-magnetron co-sputtering method is investigated. All as-deposited thin films were annealed for 1 hour in the temperature range from 300 to 1100 o C in an Ar atmosphere. The samples were evaluated by using PL, Energy dispersive spectroscopy (EDX), Raman scattering and X-ray photoelectron spectroscopy (XPS) measurements. All the measurements were performed at room temperature. The PL spectrum of the Ge/Si-SiO2 thin films increased more than Si-SiO2 thin film by approximately 10 times at the low annealing temperature of 500 oC. From the results of Raman scattering and XPS measurements, it is consider that the luminescence centers increased due to film relaxation under annealing, and the relaxation occurred due to diffusion of Ge. An increase in the PL intensity of Ge/Si-SiO2 thin film is systematically discussed. INTRODUCTION Since a report of efficient photoluminescence (PL) from porous silicon, Si-based light emitting materials have been continuing interest for the purpose of developing the full color displays and the integrated optoelectronics [1,2]. Si nanocrystals embedded in silicon oxide (SiSiO2) and Ge nanocrystals embedded in silicon oxide (Ge-SiO2) thin film show a strong PL which doesn’t usually appear in the bulk materials and visible strong PL at room temperature [13]. Recently, light emitting device of the Si-SiO2 and the Ge-SiO2 thin film structures can be prepared by several methods, such as plasma enhanced chemical vapor deposition (PECVD), magnetron co-sputtering, ion implantation, and laser ablation [2,4]. The Si-SiO2 thin films show PL of red (1.3-1.5 eV) emission. This PL emission can be attributable to connect with carrier recombination in Si nanocrystals, and when the increase in size of Si nanocrystals arose, the PL peak position shifts to high energy side [3,5]. In addition, the Ge-SiO2 thin films show PL of violet (3.1-3.2 eV) and blue (2.58-2.95 eV) emission. It is reported that these PL emissions can be attributable to Ge-related oxygen defect centers [1,2,4,6]. Moreover, it is reported that PL of green (~2.25 eV) and red (~2.00 eV) emission are caused by oxygen defect centers and non-bridging oxygen hole centers (NBOHC) in host material SiO2, respectively [3,6]. But, optical properties of Ge nanocrystals and Si nanocrystals embedded in silicon oxide thin film (Ge/Si-SiO2) has not been studied yet. Consequently, we prepared the Ge/Si-SiO2 and the Si-SiO2 thin film, and compared the optical properties. In this paper, we report a novel strong PL of green emission from the Ge/Si-SiO2 thin film prepared by RF-magnetron co-sputtering method.
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