Paramagnetic defects and amorphous network reconstruction of magnetron sputtered a-SiO{sub 2}:Ge films

Journal Article · Wed Aug 15 00:00:00 EDT 2007 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.2769780· OSTI ID:21057513

Pereira, R N; Skov Jensen, J; Chevallier, J; Bech Nielsen, B; Nylandsted Larsen, A ^[1]

---

1. Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus, Denmark and Walter Schottky Institute, Technical University Munich, Am Coulombwall 3, 85748 Garching (Germany)

We have investigated the paramagnetic defects and the structure of magnetron sputtered amorphous SiO{sub 2} films containing 3.8 at. % Ge (a-SiO{sub 2}:Ge) over the 500-1000 deg. C annealing temperature range using electron paramagnetic resonance (EPR), Fourier-transform infrared (FTIR) absorption, and transmission electron microscopy (TEM). The EPR spectra of as-grown a-SiO{sub 2}:Ge films reveal three different defects: Si-E{sup '} centers with g{sub parallel}=2.0019 and g{sub perpendicular}=2.0004, Ge{identical_to}Si{sub 3} dangling bonds with g{sub parallel}=2.001 and g{sub perpendicular}=2.024, and Si{identical_to}Si{sub 2}O or Si{identical_to}SiO{sub 2} defects with g=2.004. While the Si-E{sup '} and g=2.004 lines are removed by heat treatments at 500 deg. C, the signal from Ge{identical_to}Si{sub 3} dangling bonds persists up to annealing temperatures of 700 deg. C. The structural changes induced upon annealing on the a-SiO{sub 2}:Ge films have been studied by monitoring the frequency and linewidth of the asymmetric stretching vibration of the Si-O-Si linkage using FTIR. We find that the rearrangement of the amorphous oxide network occurs primarily within the 500-700 deg. C temperature range and no further significant recovery happens upon annealing at temperatures above 700 deg. C, in line with the EPR results. TEM images reveal the formation of Ge nanocrystals (Ge ncs) with diameters of 2-4 nm already upon heat treatments at 500 deg. C. Moreover, it is shown that the mean size of the Ge ncs increases quite significantly as the temperature of the heat treatments increases. The mean diameter of Ge ncs observed after annealing at temperatures above 600 deg. C is above that expected for Ge ncs with efficient photoluminescence properties. The implications of our experimental results for the understanding of the quenching of the photoluminescence from quantum-confined excitons within Ge ncs are briefly discussed.

• OSTI ID: 21057513
• Journal Information: Journal of Applied Physics, Vol. 102, Issue 4; Other Information: DOI: 10.1063/1.2769780; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ABSORPTION
ABSORPTION SPECTROSCOPY
ANNEALING
CRYSTAL DEFECTS
ELECTRON SPIN RESONANCE
FOURIER TRANSFORM SPECTROMETERS
GERMANIUM
GERMANIUM ALLOYS
INFRARED SPECTRA
NANOSTRUCTURES
PARAMAGNETISM
PHOTOLUMINESCENCE
SEMICONDUCTOR MATERIALS
SILICON ALLOYS
SILICON OXIDES
SPUTTERING
SURFACE COATING
TEMPERATURE RANGE 0400-1000 K
THIN FILMS
TRANSMISSION ELECTRON MICROSCOPY