CHARACTERISATION OF Ge NANOCRYSTALS IN CO-SPUTTERED GeSiO 2 SYSTEM USING RAMAN SPECTROSCOPY, RBS AND TEM Y.W. Ho, 1 V. Ng, 1 W.K. Choi, 1 S.P. Ng, 1 T. Osipowicz, 2 H.L. Seng, 2 W.W. Tjui 3 and K. Li 3 1 Microelectronics Laboratory, Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 2 Research Center for Nuclear Microscopy, Department of Physics, National University of Singapore, Lower Kent Ridge, Singapore 119260 3 Institute of Materials Research and Engineering, 3 Research Link, Singapore 117602 (Received August 21, 2000) (Accepted in revised form December 13, 2000) Keywords: Rutherford backscattering; Germanium; Nanocrystal; Transmission electron microscopy; Raman spectroscopy 1. Introduction The attraction of silicon-based optoelectronics application has spurred research efforts in the areas of growth, synthesis and characterization of group IV (Si, Ge) nanocrystals. In this paper, germanium nanocrystals (nc-Ge) were synthesized by rapid thermal annealing (RTA) rf-cosputtered thin film composed of silicon dioxide and germanium. The synthesis of nc-Ge via this method was previously reported [1,2], where Raman spectroscopy was used to estimate the size of the nanocrystals synthesized. In this paper we present the results from Raman spectroscopy, analyzed with data from Rutherford backscattering (RBS) and HRTEM. Raman spectroscopy has been used extensively to estimate the size of the nanocrystals and the crystallinity of germanium because of its convenience and non-destructive nature. One interesting feature was the broadening of the Raman spectra for samples annealed at 900 and 1000°C. We correlated these results with HRTEM analysis and RBS experiments to fine tune the phonon confinement theory for our system. 2. Experiment The samples were prepared by rf-cosputtering of SiO 2 and Ge (99.99%) on to a 100 n-type Si substrate. Six pieces of Ge (10  10  0.3 mm 3 each) were attached to a 4“ SiO 2 target and cosputtered in an Anelva sputtering system (SPH-210H) in argon ambient. The sputtering pressure was maintained at 3  10 -3 Torr with rf sputtering power set to 100W. The process time of 30 minutes yielded film of approximately 3000Å. RTA was carried out in an A.S.T. rapid thermal processor (SHS 10). The annealing temperature used ranged from 600-1000°C with annealing time of 300s and ramp-up and ramp-down rates fixed at 30°C/s. Raman measurements were made on a Renishaw 2000 Micro-Raman spectroscopy system with a 514.5nm argon laser. The Raman spectrum had a resolution of 0.74cm -1 . Scripta mater. 44 (2001) 1291–1295 www.elsevier.com/locate/scriptamat 1359-6462/01/$–see front matter. © 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved. PII: S1359-6462(01)00743-6