Influence of RF-sputtering power on formation of vertically stacked Si1−xGex nanocrystals between ultra-thin amorphous Al2O3 layers: structural and photoluminescence properties

The authors would like to thank Professor David J Barber (University of Essex) for his helpful discussions and critical reading of this manuscript, and Engineer José Santos for technical support at Thin Film Laboratory.In this work, we investigate the structural and photoluminescence (PL) properties of (SiGe+Al2O3)/Al2O3 multi-layer films with layer thicknesses in the range of a few nanometres. The films were prepared by magnetron sputtering deposition at room temperature followed by an annealing process to promote the formation of small SiGe nanocrystals (NCs) (∼ 3 to 5 nm) embedded between ultra-thin (∼ 6 nm thickness) Al2O3 layers. Our results show that the structural and compositional properties of the films can be tuned by changing the RF-power. It is found that nearly spherical and well confined isolated SiGe NCs (∼ 5 nm) are obtained for an RF-power value of 80 W. The PL properties of the films were studied and optical emission in the blue visible wavelength region was observed.FEDER through the COMPETE Programme and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Project PEst-C/FIS/UI607/2011 and PEst-C/CTM/LA0025/2011.ELETTRA Synchrotron Radiation Center for the measurements at the SAXS beamline.European COST Actions MP0901-NanoTP and MP0903-NanoAlloy.Electron microscopy work at ORNL was supported by the Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, US Department of Energy.Croatian Ministry of Science, Higher Education and Sport, (project number 098-0982886-2895).Karlsruhe Nano Micro Facility (KNMF, www.kit.edu/knmf), a Helmholtz Research Infrastructure at Karlsruhe Institute of Technology (KIT, www.kit.edu).FCT and POPH grant SFRH/BD/45410/2008.Spanish CSIC JAE-DOC-070/01 programme co-funded by FSE.Spanish MICINN/MEC (projects TEC2011-29120-C05-03 and CONSOLIDER INGENIO CSD2009-00013) and the Junta de Andalucía (PAI research group TEP-120; project P08-TEP-03516).European Research Council Starting Investigator Award ‘STEMOX’