Search query: Doping silicon nanocrystals and quantum dots

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abstract: The ability to incorporate a dopant element into silicon nanocrystals (NC) and quantum dots (QD) is one of the key technical challenges for the use of these materials in a number of optoelectronic applications. Unlike doping of traditional bulk semiconductor materials, the location of the doping element can be either within the crystal lattice (c doping) on the surface (s doping) or within the surrounding matrix (m doping) A review of the various synthetic strategies for doping silicon NCs and QDs is presented, concentrating on the efficacy of the synthetic routes, both in situ and post synthesis, with regard to the structural location of the dopant and the doping level. Methods that have been applied to the characterization of doped NCs and QDs are summarized with regard to the information that is obtained, in particular to provide researchers with a guide to the suitable techniques for determining dopant concentration and location, as well as electronic and photonic effectiveness of the dopant.
author_names: Brittany L Oliva-Chatelain

Thomas M Ticich

Andrew R Barron
title: Doping silicon nanocrystals and quantum dots.
venue: Nanoscale
year: 2016

abstract: Abstract As the most fundamental material for microelectronics, silicon (Si) has bourgeoned in the past more than half a century. However, given the indirect bandgap of Si, the use of Si in optoelectronics is relatively limited due to its mediocre optical absorption and rather poor optical emission. During many years of efforts for extending the use of Si in optoelectronics Si nanocrystals (NCs) that are one type of the most important Si nanostructures have attracted significant attention owing to their remarkable electronic and optical properties. Si NCs are actually crystalline Si nanoparticles, which may be called Si quantum dots if their size is smaller than ~10 nm. With the manipulation of the size, surface and doping of Si NCs great tunability for the light emission from Si NCs with the quantum yield of more than 60% has been realized. Based on the efficient light emission from Si NCs high performance Si NC light emitting devices have been demonstrated. In the meantime, the efficient light emission from Si NCs has also been utilized for synaptic simulations in neuromorphic computing and down shifting in photovoltaics. Broadband optical absorption ranging from the ultraviolet to mid infrared has been recently obtained for Si NCs mainly by taking advantage of doping. This has enabled the use of Si NCs in novel solar cells, photodetectors and optoelectronic synaptic devices. The continuous improvement of the electronic and optical properties of Si NCs has made Si NCs unfading Si materials for optoelectronics, contributing to the development of Si based optoelectronic integration.
author_names: Zhenyi Ni

Shu Zhou

Shuangyi Zhao

Wenbing Peng

Deren Yang

Xiaodong Pi
title: Silicon nanocrystals: unfading silicon materials for optoelectronics
venue: Materials Science and Engineering: R: Reports
year: 2019

abstract: Silicon nanocrystals, also known as silicon quantum dots, are regarded as green alternatives to traditional quantum dots composed of heavy metal elements. While it is well known that the semiconductor properties of these materials can be tuned by doping with p/n type dopants (i.e. boron and phosphorus) there is a lack of systematic understanding of their potential environmental impact if released into the ecosystem. Here, we demonstrate that introduction of dopants, especially phosphorus, cause doped silicon nanocrystals to produce reactive oxygen species, resulting in significant toxicity to a model microorganism, Shewanella oneidensis MR 1. In addition, the interaction between bacteria cells and silicon nanocrystals was investigated using dark field microscopy and bio TEM. Interestingly, boron doped silicon nanocrystals tended to attach to the cell surface while this phenomenon was not observed for undoped or phosphorus doped silicon nanocrystals.
author_names: Bo Zhi

Sadhana Mishra

Natalie V Hudson-Smith

Uwe R Kortshagen

Christy L Haynes
title: Toxicity Evaluation of Boron and Phosphorus Doped Silicon Nanocrystals toward Shewanella oneidensis MR 1
year: 2018

abstract: Doping with donor and acceptor impurities is an effective way to control light emission originated from quantum size effect in Si nanocrystals. Combined measurements of photoluminescence intensity and kinetics give valuable information on mechanisms of the doping influence. Phosphorus, boron, and nitrogen were introduced by ion implantation into Si+ implanted thermal SiO2 films either before or after synthesis of Si nanocrystals performed at Si excess of about 10 at. and annealing temperatures of 1000 and 1100 degrees C. After the implantation of the impurity ions the samples were finally annealed at 1000 degrees C. It is found that, independently of ion kind, the ion irradiation (the first stage of the doping process) completely quenches the photoluminescence related to Si nanocrystals (peak at around 750 nm) and modifies visible luminescence of oxygen deficient centers in the oxide matrix. The doping with phosphorus increases significantly intensity of the 750 nm photoluminescence excited by a pulse 337 nm laser for the annealing temperature of 1000 degrees C, while introduction of boron and nitrogen atoms reduces this emission for all the regimes used. In general, the effective lifetimes (ranging from 4 to 40 micros) of the 750 nm photoluminescence correlate with the photoluminescence intensity. Several factors such as radiation damage, influence of impurities on the nanocrystals formation, carrier impurity interaction are discussed. The photoluminescence decay is dominated by the non radiative processes due to formation or passivation of dangling bonds, whereas the intensity of photoluminescence (for excitation pulses much shorter than the photoluminescence decay) is mainly determined by the radiative lifetime. The influence of phosphorus doping on radiative recombination in Si quantum dots is analyzed theoretically.
author_names: Alexey N Mikhaylov

David Tetelbaum

Vladimir A Burdov

Oleg N Gorshkov

A I Belov

D A Kambarov

Vladimir Alekseevich Belyakov

V K Vasiliev

Anatoly Kovalev

D M Gaponova
title: Effect of ion doping with donor and acceptor impurities on intensity and lifetime of photoluminescence from SiO2 films with silicon quantum dots.
venue: Journal of nanoscience and nanotechnology
year: 2008

abstract: Experimental results on photoluminescence spectra and kinetics obtained in the studies of SiO2 oxide layers nanostructured by ion implantation of silicon with subsequent doping and annealing are systematized. It is shown that phosporus doping by ion implantation leads to a severalfold increase in the intensity and decay time of nonstationary photoluminescence at l 750 nm because of an increase in the probability of radiative recombination at Si doped quantum dots and of passivation of dangling bonds at the nanocrystal matrix interfaces.
author_names: A I Belov

Vladimir Alekseevich Belyakov

Vladimir A Burdov

A N Mikhailov

David Tetelbaum
title: Phosphorus doping as an efficient way to modify the radiative interband recombination in silicon nanocrystals
year: 2009

abstract: Doping of Si nanocrystals is an important topic in the emerging field of Si nanocrystals based all Si tandem solar cells. Boron doped Si nanocrystals embedded in a silicon dioxide matrix were realized by a co sputtering process, followed by high temperature annealing. The x ray photoelectron spectroscopy B 1s signal attributable to Si B (187 eV) and/or B B (188 eV) indicates that the boron may exist inside Si nanocrystals. A higher probability of effective boron doping was suggested for Si rich oxide films with a low oxygen content, Then, structural and optical properties were characterized with a focus on the effects of the boron content on Si quantum dots. The results show that as the boron content increases, the nanocrystal size is slightly reduced and the Si crystallization is suppressed. The photoluminescence intensity of the films is decreased as the boron content increases. This is due to boron induced defects and/or Auger processes induced by effective doping. These results can provide optimal conditions for future Si quantum dot based solar cells.
author_names: Xiaojing Hao

Eun-Chel Cho

Chris Flynn

Y S Shen

Gavin Conibeer

M a Green
title: Effects of boron doping on the structural and optical properties of silicon nanocrystals in a silicon dioxide matrix.
venue: Nanotechnology
year: 2008

abstract: Silicon nanocrystal quantum dots in a dielectric matrix form a material with higher band gap than silicon, but still compatible with silicon technology. So far, devices using silicon nanocrystals have been realized either on silicon wafers, or using in situ doping in the superlattice deposition which may hinder the nanocrystal formation. In this paper, a vertical PIN device is presented which allows to investigated the electrical and photovoltaic properties of nanocrystal quantum dot layers. The device structure circumvents any influence of a substrate wafer or dopants and provides full flexibility in the material choice of both, i.e. electron and hole, contacts. Furthermore, not high temperature stable contact materials can be applied. Devices have been realized using SiC/Si nanocrystal multilayers as the i region and doped a SixC1 x:H layers as electron and hole contacts. First devices show open circuit voltage of up to 400mV.
author_names: Philipp Loper

A Witzky

Andreas Hartel

Sebastian Gutsch

Daniel Hiller

Jan Christoph Goldschmidt

Stefan Janz

Stefan W Glunz

Margit Zacharias
title: Photovoltaic properties of silicon nanocrystals in silicon carbide
venue: OPTO
year: 2012

abstract: While the literature for the doping of silicon quantum dots (QDs) and nanocrystals (NCs) is extensive, reports of doping their germanium analogs are sparse. We report a range of attempts to dope Ge QDs both during and post synthesis. The QDs have been characterized by TEM, XPS, and I/V measurements of SiO 2 coated QD thin films in test cells using doped Si substrates. The solution synthesis of Ge QDs by the reduction of GeCl 4 with LiAlH 4 results in Ge QDs with a low level of chlorine atoms on the surface; however, during the H 2 PtCl 6 catalyzed alkylation of the surface with allylamine, to enable water solubility of the Ge QDs, chlorine functionalization of the surface occurs resulting in p type doping of the QD. A similar location of the dopant is proposed for phosphorus when incorporated by the addition of PCl 3 during QD synthesis; however, the electronic doping effect is greater. The detected dopants are all present on the surface of the QD s type) suggesting a self purification process is operative. Attempts to incorporate boron or gallium during synthesis were unsuccessful.
author_names: Brittany L Oliva-Chatelain

Andrew R Barron
title: Experiments towards size and dopant control of germanium quantum dots for solar applications
year: 2015

abstract: The analysis of original works devoted to preparation and investigation of nanocrystalline silicon (nc Si) films containing Si quantum dots (QDs) that exhibit photoluminescence (PL) within the range 1.4 3.2 eV at room temperature is presented. Thin films were prepared by pulse laser deposition (PLD) Offered by authors doping these nc Si films with gold in the growing process provided passivation of Si dangling bonds (DB) and some increase in the forbidden gap width of a barrier layer. Demonstrated are possibilities to explain and control stationary and kinetic characteristics of visible PL in the framework of the quantum dimensional model as well as radiative exciton annihilation with taking into account Si nanocrystals (NCs) size distribution pronounced in PL features.
author_names: E B Kaganovich

Sergey V Svechnikov

E G Manoilov

I M Kizyak
title: Formation of photoluminescent properties inherent to silicon quantum dots
year: 2006

abstract: The question about the mechanisms of the photoluminescence enhancement of the system of silicon nanocrystals embedded into silica matrix at phosphorus doping is described. Both the experimental and theoretical arguments are presented.
author_names: David Tetelbaum

Vladimir A Burdov

Alexey N Mikhaylov

Sergei A Trushin
title: About the phosphorus sensitization of silicon quantum dots in SiO2 photoluminescence
venue: Saratov Fall Meeting
year: 2003