Papers by Keyword: Silicon Nanocrystals

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Authors: M.D. Efremov, Vladimir A. Volodin, D.V. Marin, Sofia A. Arzhannikova, M.G. Ivanov, S.V. Gorajnov, A.I. Korchagin, V.V. Cherepkov, A.V. Lavrukhin, S.N. Fadeev, R.A. Salimov, S.P. Bardakhanov
Abstract: Silicon nanopowders were produced using electron-beam-induced evaporation of bulk silicon ingots in various gas atmosphere. Optical properties of the nanopowders were studied with the use of photoluminescence and Raman spectroscopy techniques. Photoluminescence peaks in the visible region of the spectrum have been detected at room temperature in silicon nanopowders, produced in argon gas atmosphere. Strong short-wavelength shift of the photoluminescence peaks can be result of quantum confinement effect for electrons and holes in small silicon nanocrystals (down to 2 nm in diameter). The size of silicon nanocrystals was estimated from Raman spectroscopy data. The calculated in frame of effective mass model optical gaps for silicon nanocrystals of spherical shape are in good correlation with experimental photoluminescence data. The attempts of deposition of silicon nanocrystal films from the nanopowders on silicon substrates were carried out.
Authors: M.D. Efremov, G.N. Kamaev, G.A. Kachurin, A.V. Kretinin, Vladimir A. Volodin, D.V. Marin, Sofia A. Arzhannikova, V.V. Malutina-Bronskaya, S.G. Yanovskaya
Authors: Manuel Schnabel, Philipp Löper, Mariaconcetta Canino, Sergey A. Dyakov, Marco Allegrezza, Michele Bellettato, Julià López-Vidrier, Sergi Hernández, Caterina Summonte, Blas Garrido, Peter R. Wilshaw, Stefan Janz
Abstract: Silicon nanocrystals (Si NCs) are a promising candidate for the top cell of an all-Si tandem solar cell with a band gap from 1.3-1.7 eV, tuneable by adjusting NC size. They are readily produced within a Si-based dielectric matrix by precipitation from the Si excess in multilayers of alternating stoichiometric and silicon-rich layers. Here we examined the luminescence and transport of Si NCs embedded in SiC. We observed luminescence that redshifts from 2.0 to 1.5 eV with increasing nominal NC size. Upon further investigation, we found that this redshift is to a large extent due to Fabry-Pérot interference. Correction for this effect allows an analysis of the spectrum emitted from within the sample. We also produced p-i-n solar cells and found that the observed I-V curves under illumination could be well-fitted by typical thin-film solar cell models including finite series and parallel resistances, and a voltage-dependent current collection function. A minority carrier mobility-lifetime product on the order of 10-10 cm2/V was deduced, and a maximum open-circuit voltage of 370 mV achieved.
Authors: Anton A. Konakov, Vladimir A. Belyakov, Vladimir A. Burdov
Abstract: Using the envelope-function approximation the electronic states and the optical gap of silicon nanocrystals heavily doped with phosphorus have been calculated. Assuming the uniform impurity distribution over the crystallite volume we have found the fine structure of the electron ground state (induced by the valley-orbit interaction) and the optical gap as a function of the crystallite size and donor concentration. It is shown that the energy of the ground singlet state decreases almost linearly as the concentration increases, while the valley-orbit splitting increases nonlinearly. Phosphorus doping also results in the decrease of the nanocrystal gap with increasing the impurity concentration.
Authors: G. Benassayag, M. Shalchian, Jeremie Grisolia, Caroline Bonafos, S.M. Atarodi, A. Claverie
Abstract: In this paper, we present a study on the contribution of silicon nanocrystals to the electrical transport characteristics of large (100 m x 100 m) and small (100 nm x 100 nm) metaloxide- semiconductor (MOS) capacitors at room temperature. A layer of silicon nanocrystals is synthesized within the oxide of these capacitors by ultra-low energy ion implantation and annealing. Several features including negative differential resistance (NDR), sharp current peaks and random telegraph signal (RTS) are demonstrated in the current-voltage and current-time characteristics of these capacitors. These features have been associated to charge storage in silicon nanocrystals and to the resulting Coulomb interaction between the stored charges and the tunneling current. Clear transition from a continuous response of large capacitors to a discrete response of small capacitors reveals the quantized nature of the charge storage phenomenon in these nanocrystalline dots. The effect of the nanocrystal density from nearly continuous layer to isolated nanodots is also presented.
Authors: K. Dohnalová, K. Luterová, J. Valenta, Jiří Buršík, M. Procházka, V. Křesálek, B. Hönerlage, I. Pelant
Abstract: Recent reports on experimental observation of optical gain in silicon nanostructures in the visible region, performed at several laboratories all over the world, have triggered an extraordinary surge of interest in silicon lasing. However, attempts aimed at reproducing the red stimulated emission from „standard“silicon nanocrystals (sized 3-5 nm) at some other laboratories either failed, or. did not come to definite conclusions. Therefore, more detailed measurements of optical gain in a wider variety of samples containing Si nanocrystals are required in order to unravel whether or not the observation of optical gain is an intrinsic property of Si nanocrystals. We have performed a detailed study of optical gain in layers of densely packed Si nanocrystals in SiO2, prepared on the basis of porous Si, using the variable-stripe-length (VSL) method in combination with the shifted-excitation-spot (SES) method. In selected samples we have observed a distinct difference in behaviour between VSL and SES curves, indicating the occurrence of positive optical gain of ~ 24 cm-1. Preliminary reports on transport and electroluminescence measurements in thin films of SiO2 doped with porous silicon grains, prepared by spin-coating technique, are also discussed.
Authors: Sofia A. Arzhannikova, M.D. Efremov, Vladimir A. Volodin, G.N. Kamaev, D.V. Marin, S.A. Soldatenkov, V.S. Shevchuk, S.A. Kochubei, A.A. Popov, Yu. A. Minakov
Abstract: The laser assisted formation of silicon nanocrystals in SiNx films deposited on quartz and silicon substrates is studied. The Raman spectroscopy revealed creation of the Si cluster and crystallite after excimer laser treatments. Photoluminescence signal from the samples was detected at room temperatures. I-V and C-V measurements were carried out to examine carries transfer through dielectrics film as well as recharging of electronics states.
Authors: Talivaldis Puritis, J. Kaupuzs
Authors: D.H. Jang, Gil Ho Gu, Chan Gyung Park
Abstract: Bulk silicon is the material for microelectronics fabrication such as memory device. However, its optical properties are poor due to its indirect band gap. Since the photoluminescence from porous silicon at room temperature was first reported by Canham, silicon nanostructures have attracted considerable interest due to their potential applications in optoelectronic devices such as Si-based LEDs, solar cell. In the present study, the nanocrystalline silicons were synthesized by non-thermal plasma from gas phase. And Nitrogen plasma was applied to reduce the nonraidative recombination center which related to the emission efficiency. To confirm the effect of nitrogen plasma, the compositional, electrical and optical analysis of silicon nanocryatals layer were also investigated.
Authors: F. Iacona, G. Franzò, E.C. Moreira, D. Pacifici, F. Priolo
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