Synthesis of localized 2D-layers of silicon nanoparticles embedded in a SiO 2 layer by a stencil-masked ultra-low energy ion implantation process (original) (raw)
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Superlattices and Microstructures, 2008
We propose an original approach called a "stencil-masked ion implantation process" for performing a spatially localized synthesis of a limited number of Si nanocrystals within a thin SiO 2 layer. In this process, the SiO 2 layer is irradiated with 1 keV silicon ions through a stencil mask containing apertures (from 100 nm to 2 µm), and subsequently thermally annealed to create Si nanocrystals. Scanning electron microscopy images show that the implanted areas mimic the mask geometry. Energy-filtered transmission electron microscopy and photoluminescence spectroscopy studies confirm that only the implanted areas are Si nanocrystal rich and light emitting. The smaller nanocrystal size detected near the edges of the implanted areas is attributed to dose reduction effects. This feature leads to a blueshift of the PL energy. Electrical properties of the structures produced are investigated using Al gate MOS capacitors. Room temperature I -V and I -t characteristics exhibit discrete current peaks that are associated with single-electron charging of the nanocrystals and electrostatic interaction of the trapped charges with the tunnelling current.
Electrochemical and Solid-State Letters, 1999
Two-dimensional (2-D) arrays of silicon nanocrystals were fabricated in thermally grown SiO 2 films by 1 keV 28 Si + ion implantation and subsequent thermal annealing. The nanocrystals characteristics (size, shape, and spatial distribution) as a function of the implanted dose and annealing conditions were investigated by transmission electron microscopy. The nanocrystals were located at a tunneling distance from the oxide surface. With increasing size, the nanocrystals changed from quasi-spheres to faceted platelets. With a reduction in the implantation dose and the annealing temperature, the size of the nanocrystals decreased, their size distribution became more narrow, while their spatial arrangement remained 2-D.
Structural and Optical Characterization of Silicon Nanocrystals Obtained by Ion Implantation
Abstract Photoluminescence (PL) was used to investigate the luminescence mechanism in Si nanocrystals. Si ions were implanted in SiO2 films at 100 keV to a dose of 5x1016/cm2. An intense photoluminescence band in (1.2-1.6) eV was observed after implanted films were annealed at 1000oC in nitrogen. Deconvolution of photoluminescence suggests that others recombination centers possibly are present into the samples.
Optical and structural properties of encapsulated Si nanocrystals formed in SiO2 by ion implantation
2002
A possible mechanism for the photoemission from Si nanocrystals in an amorphous SiO matrix fabricated by ion implantation 2 is reported. We have measured the implantation dose dependence on the photoluminescence behavior images of Si nanocrystals in SiO layers, fabricated by ion implantation and a subsequent annealing step. After annealing, a photoluminescence band, 2 peaking just below 1.7 eV, was observed. The peak energy of the photoluminescence was found to be affected by the dose of implanted Si ions, but to be independent of annealing time. We also present experimental results of high-resolution transmission electron microscopy (HRTEM) for each annealing step. The size of Si nanocrystals increases with increasing ion dose and annealing time. These results indicate that whilst the excitation photons are absorbed by Si nanocrystals, the emission is not simply due to electron-hole recombination inside the Si nanocrystals, but is related to the presence of some kind of defects, most likely located at the interface between the Si nanocrystals and the SiO , for which the characteristic energy levels are affected by 2 cluster-cluster interactions. ᮊ
Si-nanoparticle synthesis using ion implantation and MeV ion irradiation
physica status solidi (c), 2015
A dielectric matrix with embedded Si-nanoparticles may show strong luminescence depending on nanoparticles size, surface properties, Si-excess concentration and matrix type. Ion implantation of Si ions with energies of a few tens to hundreds of keV in a SiO 2 matrix followed by thermal annealing was identified as a powerful method to form such nanoparticles. The aim of the present work is to optimize the synthesis of Si-nanoparticles produced by ion implantation in SiO 2 by employing MeV ion irradiation as an additional annealing process. The luminescence properties are measured by spectrally resolved photoluminescence including PL lifetime measurement, while X-ray reflectometry, atomic force microscopy and ion beam analysis are used to characterize the nanoparticle formation process. The results show that the samples implanted at 20%-Si excess atomic concentration display the highest luminescence and that irradiation of 36 MeV 127 I ions affects the luminosity in terms of wavelength and intensity. It is also demonstrated that the nanoparticle luminescence lifetime decreases as a function of irradiation fluence.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
Experiments were undertaken to verify a recent claim of optical gain produced by photo-excited silicon nanocrystals. This was achieved by propagating an optical probe beam (wavelength of 800 nm) through a slab waveguide containing silicon nanocrystals and measuring this signal as the nanocrystals were optically excited by a high energy density (3.5-3500 lJ/cm 2) pump beam (wavelength 355 nm). The probe signal was observed to decrease when the guide was subjected to optical pumping-no gain was observed. Indeed, the results are shown to be consistent with an excited state absorption process, in which photo-generated carriers induce ÔfreeÕ carrier absorption.
Efficient n-type doping of Si nanocrystals embedded in SiO2 by ion beam synthesis
Applied Physics Letters, 2013
It is shown that co-implantation, with overlapping projected ranges of Si and P or As, followed by a single thermal annealing step is an efficient way to form doped Si nanocrystals (Si-nc's) embedded in SiO 2 with diameters of a few nanometers. Atom probe tomography is used to image directly the spatial distribution of the various species at the atomic scale, evidencing that the P and As atoms are efficiently introduced inside the Si nanocrystals. In addition, we report on the influence of the dopant doses on the Si-nc's related photoluminescence as well as on the I(V) characteristics of MOS structures including these Si-nc's. V C 2013 American Institute of Physics.
Lamp annealing effects on the formation process of implanted silicon nanocrystals in SiO 2
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2007
Si ion implantation into SiO2 and subsequent high temperature anneals induce the formation of embedded luminescent Si nanocrystals. The potentialities of rapid thermal annealing to enhance the photoluminescence as well as those to induce low temperature formation of luminescent Si nanocrystals have been investigated. Si ion implantation was used to synthesize specimens of SiO2 containing supersaturated Si with different concentrations,