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 SiO2 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.
Co-implantation, with overlapping implantation projected ranges, of Si and doping species (P, As, and B) followed by a thermal annealing step is a viable route to form doped Si nanocrystals (NCs) embedded in silica (SiO2). In this paper, we investigate optical characterizations of both doped and un-doped Si-NCs prepared by this method. The effective NC presence in the oxide layer and their crystallinity is verified by Raman spectrometry. Photoluminescence (PL) and PL excitation measurements reveal quantum confinement effects and a gradual PL quenching with increasing dopant concentrations. In un-doped NC, the measured Stokes shift remains constant and its value ∼0.2 eV is almost twice the Si–O vibration energy. This suggests that a possible radiative recombination path is a fundamental transition assisted by a local phonon. PL lifetime investigations show that PL time-decays follow a stretched exponential. Using a statistical model for luminescence quenching, a typical NC diameter close to 2 nm is obtained for As- and P-doped samples, consistent with our previous atomic probe tomography (APT) analyses. APT also demonstrated that n-type dopant (P and As) are efficiently introduced in the NC core, whereas p-type dopant (B) are located at the NC/SiO2 interface. This last observation could explain the failure of the luminescence-quenching model to determine NC size in B-doped samples. All together, these experimental observations question on possible different carrier recombination paths in P or As doped NC compared to B one's.
Co-implantation, with overlapping implantation projected ranges, of Si and of the doping species (P, As, or B), followed by a single thermal anneal step, is proved to be a viable route to form doped Si-nc’s embedded in SiO2, with diameters of a few nanometers. Extensive results of the evolution of the Si-nc’s related photoluminescence, as a function of the dopant implanted dose, are presented and discussed. Atomic Probe Tomography (APT) is used to image directly the spatial distribution of the various species at the atomic scale. The 3D APT data demonstrate that n-type dopant atoms (P and As) are efficiently introduced in the "bulk" of the Sinanocrystals, whereas B atoms are preferentially located at their periphery, at the Si/SiO2 interface.
Our goal is to use the versatility of ion beam synthesis to grow nanocrystals of InxGa1‐xAs alloys embedded in a silicon substrate. We study, first, the annealing conditions necessary to grow well defined InAs and GaAs binary nanocrystals. High dose of As, Ga and In is implanted, respectively, at 130, 130 and 180 keV to have overlapping as‐implanted profiles. The nanocrystals growth is then achieved by rapid thermal annealing at various temperatures between 650 and 800 °C for 1 min under an argon gas flow. Rutherford backscattering spectroscopy profiles show that no significant impurity out‐diffusion occurs below 800 °C for both systems. In and As thermal redistributions lead to superposed profiles. Raman spectroscopy measurements prove that InAs nanocrystals are formed above 650 °C, while 800 °C annealing is necessary to obtain GaAs nanocrystals and show that these thermal budgets are enough to fully recrystallize the implanted layer. Grazing incidence X‐ray diffraction patterns exhibit clearly InAs and GaAs related peaks. These results prove that GaAs and InAs nanocrystals can be grown in a common temperature range (700‐800 °C), opening the route to the growth of ternary InxGa1‐xAs alloys in the same conditions. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Co‐implantation, with overlapping implantation projected ranges, of Si and doping species (P, As, B) followed by a thermal annealing step is a viable route to form doped Si nanocrystals (NCs) embedded in SiO2. This presentation deals with optical characterizations of both doped and undoped Si‐NC prepared by this method. The NC effective presence in the oxide layer and their crystallinity is verified by Raman spectrometry. Photoluminescence (PL) and PL excitation measurements reveal quantum confinement effects and a gradual PL quenching with increasing dopant concentrations. The measured Stokes shift remains constant and its value ∼ 0.2 eV is almost twice the Si–O vibration energy. This suggests that a possible radiative recombination path is a fundamental transition assisted by a local phonon. Lifetime investigations show that PL time‐decays follow a stretched exponential. Atomic probe tomography analyses demonstrate that n‐type dopants (P, As) are efficiently introduced in the NC core, whereas p‐type dopant (B) are located at the NC/SiO2 interface. All together these experimental observations question on possible different carrier recombination paths in P or As doped NC compared to B one's. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
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