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Descripción
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| Group IV (Si or Ge) nanocrystals embedded in a dielectric medium have potential applications in electronic and optoelectronic devices. Previous results indicate that low pressure chemical vapour deposition (LPCVD) of amorphous discontinuous SiGe films in SiO2 on top of Si-substrates and their subsequent crystallization permit to obtain a homogeneous distribution of SiGe nanocrystals, the process being fully compatible with CMOS technology [1]. In this work, Si-Ge-O films were deposited by LPCVD and furnace annealed at temperatures from 600 to 1100 ºC for times up to 1 hour in a N2 atmosphere to segregate the expected excess of Si and/or Ge in the form of nanocrystals embedded in an oxide matrix. High-resolution transmission electron microscopy (HREM) and electron-diffraction pattern simulation by fast Fourier transform was used to analyze the crystal structure and distribution of the nanoparticles and their stability under in situ electron irradiation. TEM observation and electron beam irradiation were performed in a Philips Tecnai 20F FEG microscope operating at 200 kV. In the as-deposited samples an amorphous layer containing Si, Ge, and O is observed. After annealing at 600ºC a distribution of Ge-rich nanocrystals embedded in SiO2 is obtained. In Figure 1 a cross-sectional multibeam image of a sample annealed at 600ºC along the <110> direction of the Si-substrate is shown. As a general fact, electron beam irradiation induces heating and/or generation of defects, from either direct atoms displacement or dangling bonds reorganization. TEM ¿in situ¿ electron irradiation modifies the crystal structure and gives useful information on the stability of SiGe nanostructures [2]. We have study the structure modifications induced by TEM electron irradiation on the Ge-rich nanostructures. Figure 1b,c shows the effect of 1 min electron beam irradiation on sample annealed at 600ºC. Electron beam irradiation induces structural alternate order-disorder transitions in annealed crystallized Ge-rich nanoparticles and the formation of nanocrystals in the as-deposited amorphous layers | |
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Internacional
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Si |
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Nombre congreso
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14 th European Microscopy Congress |
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Tipo de participación
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960 |
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Lugar del congreso
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Aachen, Alemania |
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Revisores
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Si |
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ISBN o ISSN
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978-3-540-85301-5 |
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DOI
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Fecha inicio congreso
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01/09/2008 |
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Fecha fin congreso
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05/05/2008 |
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Desde la página
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467 |
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Hasta la página
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468 |
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Título de las actas
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Proceeding of EMC 2008. 14th European Microscopy Congress |