Raman study of stress effect on Ge nanocrystals embedded in Al2O3

Ge nanocrystals (NCs) embedded in Al2O3 were grown by RF-sputtering. X-ray diffraction, high resolution transmission electron microscopy, and Raman spectroscopy techniques were used to characterize the stresses on the NCs. While small NCs ( 17 nm) demonstrated a compressive stress effect. This could be linked to the crystal structure of the adjacent Al2O3 matrix

Structural study of Si1−xGex nanocrystals embedded in SiO2 films

We have investigated the structural properties of Si1 − xGex nanocrystals formed in an amorphous SiO2 matrix by magnetron sputtering deposition. The influence of deposition parameters on nanocrystal size, shape, arrangement and internal structure was examined by X-ray diffraction, Raman spectroscopy, grazing incidence small angle X-ray scattering, and high resolution transmission electron microscopy. We found conditions for the formation of spherical Si1 − xGex nanocrystals with average sizes between 3 and 13 nm, uniformly distributed in the matrix. In addition we have shown the influence of deposition parameters on average nanocrystal size and Ge content x

Multilayers of Ge nanocrystals embedded in Al2O3 matrix: Structural and electrical studies

In this paper, Ge/Al2O3 multilayer systems were grown by pulsed laser ablation. The grown samples were annealed at 900 °C to promote the formation of Ge nanocrystals. Rutherford backscattering spectroscopy and transmission electron microscopy confirmed the presence of a multilayer system. Grazing incidence small angles X-ray scattering technique demonstrates the formation of Ge nanoclusters formed between alumina layers. Room temperature I–V measurements showed weak carrier trapping in the system. This was explained by the leakage caused by Ge diffusion through the multilayer

Shadowed off-axis production of Ge nanoparticles in Ar gas atmosphere by pulsed laser deposition: morphological, structural and charge trapping properties

The authors would like to thank A. Tarazaga for scientific discussion and José António Santos for technical support.In this work, a novel customized shadowed off-axis deposition set-up is used to perform an original study of Ge nanoparticles (NPs) formation in an inert Ar gas atmosphere by pulsed laser deposition at room temperature varying systematically the background Ar gas pressure (Pbase(Ar)), target–substrate distance (d) and laser repetition rate (f). The influence of these parameters on the final NPs size distributions is investigated and a fairly uniform droplets-free and non-agglomerated NPs distribution with average height〈h〉= 2.8 ± 0.6 nm is obtained for optimized experimental conditions (Pbase(Ar) = 1 mbar; d = 3 cm; f = 10 Hz) with a fine control in the NPs density (from 3.2 × 10^9 cm^−2 to 1.1 × 10^11 cm^−2). The crystalline quality of as-deposited NPs investigations demonstrate a strong dependence with the Ar gas pressure and a crystalline to amorphous phase volume fraction χc > 50% is found for Pbase(Ar) = 2 mbar. The NPs functionality for charge trapping applications has been successfully demonstrated by capacitance–voltage (C–V) electrical measurements.This work has been partially funded by: (i) FEDER funds through the COMPETE program “Programa Operacional Factores de Competitividade” and by Portuguese funds through Portuguese Foundation for Science and Technology (FCT) in the frame of the Project PTDC/FIS/70194/2006; (ii) Scientific and Technological Cooperation Program between Portugal (FCT) and Morocco (CNRST)-2010/2011; (iii) European COST MP0901- NanoTP Action. E.M.F.V. and S.R.C.P. are grateful for financial support through FCT/POPH grants SFRH/BD/45410/2008 and SFRH/BPD/73548/2010, respectively. J.M.-S. is grateful for financial support through grant CSIC JAE-DOC-070/01. The authors would like to thank A. Tarazaga for scientific discussion and José Santos for technical support

A shadowed off-axis production of Ge nanoparticles in Ar gas atmosphere by pulsed laser deposition

In this work, we report on the production of Ge nanoparticles (NPs) in an inert Ar gas atmo- sphere by pulsed laser deposition (PLD) at room tem- perature (RT). The direct deposition of energetic par- ticles / droplets resulting from the ablation process of the target material has been avoided by using an origi- nal and customized o -axis shadow mask (shadowed o - axis) deposition set-up where the NPs deposition on the substrate takes place by means of scattering between the NPs formed in the vapour phase and the background Ar atoms. It is found that the Ar gas pressure parameter has a relevant role on the crystallization process, with better crystallinity obtained as the background Ar pressure is raised for the given experimental conditions.This work has been partially funded by: (i) FEDER funds through the COMPETE program Programa Op- eracional Factores de Competitividade and by Portuguese funds through Portuguese Foundation for Science and Technology (FCT) in the frame of the Project PTDC / FIS / 70194 / 2006; (ii) Scienti c and Technological Cooperation Program between Portugal (FCT) and Mo- rocco (CNRST)-2010/2011; (iii) European COST MP0901- NanoTP Action. E.M.F.V., J.M.S and S.R.C.P. are grate- ful for nancial support through the FCT grants SFRH / BD / 45410 / 2008, SFRH / BPD / 64850 / 2009 and SFRH/BPD/73548/2010, respectively. The authors would like also to thank Jos e Santos for technical sup- port

Charge storage behavior of nanostructures based on SiGe nanocrystals embedded in Al2O3 matrix

The authors would like to thank Professor David 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.The charge storage behavior of nanostructures based on Si1−xGex (0 ≤ x ≤ 1) nanocrystals (NCs) in an Al2O3 matrix was investigated. The structures have been grown by RF magnetron sputtering and subsequently annealed at temperatures ranging from 700 ºC to 1000 ºC for 30 min in nitrogen ambient. The stoichiometry of the SiGe NCs and the alumina crystalline structure were found to be significantly dependent on the RF power and the annealing temperature. The sizes of the SiGe NCs and their distribution were investigated by grazing incidence small angle X-ray scattering (GISAXS). The capacitance-voltage (C-V) and conductance-voltage (G-V) measurements were performed to investigate the charge trapping characteristics of the memory structures. The C-V hysteresis width depends on variations in the crystalline structure resulting from different annealing temperatures. It is also shown that charge injection is governed by the Fowler-Nordheim tunnel mechanism for higher electric fields.European COST Actions MP0901-NanoTPEuropean COST Actions MP0903-NanoAlloyELETTRA Synchrotron Radiation Center for the measurements at the SAXS beamlineFEDER through the COMPETE Program and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Projects PEST-C/FIS/UI607/2011 and PEst-C/CTM/LA0025/2011E.M.F.V. is grateful for financial support through the FCT and POPH of the Grant SFRH/BD/45410/2008M.B. acknowledges support from the Ministry of Science Education and Sports, Republic Croatia (Project No. 098-0982886-2895)