Electrical Properties Of Silicon Nanowires Research Articles

Modification of Silicon Nanostructures by Cold Atmospheric Pressure Plasma Jets

Cold atmospheric plasma (CAP) jets with helium (He) and argon (Ar) plasma-forming gases were used to modify the structure, photoluminescence (PL), and electrical properties of arrays of silicon nanowires (SiNWs) with initial cross-section sizes of the order of 100 nm and length of about 7‒8 microns. The CAP source consisted of a 30 kHz voltage generator with a full power up to 5 W and the CAP treatment for 1‒5 min resulted in spattering of SiNWs’ tips followed by redeposition of silicon atoms. An increase of the silicon oxide phase and a decrease of the PL intensity were observed in the plasma processed SiNW arrays. A decrease of the free hole concentration and an increase in the free electron density were revealed in heavily boron and phosphorous doped SiNWs, respectively, as it was monitored by means of the Raman spectroscopy, considering a coupling of the light scattering by phonon and free charge carriers (Fano effect) in SiNWs. The obtained results demonstrate that the CAP treatment can be used to change the length, sharpness, luminescence intensity, and electrical properties of silicon nanowires for possible applications in optoelectronics and sensorics.

Study of the morphological, optical, structural and electrical properties of silicon nanowires at varying concentrations of the catalyst precursor

Silicon nanowires (SiNWs) were grown by metal-assisted chemical etching of a p-type (100) silicon wafer.

Fabrication of SiNWs-FET Nanostructure Via Atomic Force Microscopy Lithography

The unique electrical properties of silicon nanowires (SiNWs) is one of the reasons it become an attractive transducer for biosensor nowadays. Positive (holes) and negative (electron) charge carriers from SiNWs can simply interact with either positive or negative charge of sensing target. In this paper, we have studied the fabrication of silicon nanowires field effect transistor (SiNWs-FET) nanostructure patterned on 15 Ω resistivity of p-type silicon on insulator (SOI) wafer fabricated via atomic force microscopy lithography technique. To fabricate SiNWs-FET nanostructure, a conductive AFM tip, Cr/Pt cantilever tip, was used then various value of applied voltage, writing speed and relative humidity were studied. Subsequent, followed by wet etching processes, admixture of tetramethylammonium hydroxide (TMAH) and isopropyl alcohol (IPA) were used to remove the undesired of silicon layer and diluted hydrofluoric acid (HF) was used to remove the oxide layer. From the results, it shows that, cantilever tip at 9 V with 0.4 μm/s writing speed and relative humidity between 55% - 60% gives the best formation of silicon oxide to fabricate SiNWs-FET nanostructure.

Elucidating the Effect of Etching Time Key-Parameter toward Optically and Electrically-Active Silicon Nanowires.

In this work, vertically aligned silicon nanowires (SiNWs) with relatively high crystallinity have been fabricated through a facile, reliable, and cost-effective metal assisted chemical etching method. After introducing an itemized elucidation of the fabrication process, the effect of varying etching time on morphological, structural, optical, and electrical properties of SiNWs was analysed. The NWs length increased with increasing etching time, whereas the wires filling ratio decreased. The broadband photoluminescence (PL) emission was originated from self-generated silicon nanocrystallites (SiNCs) and their size were derived through an analytical model. FTIR spectroscopy confirms that the PL deterioration for extended time is owing to the restriction of excitation volume and therefore reduction of effective light-emitting crystallites. These SiNWs are very effective in reducing the reflectance to 9–15% in comparison with Si wafer. I–V characteristics revealed that the rectifying behaviour and the diode parameters calculated from conventional thermionic emission and Cheung’s model depend on the geometry of SiNWs. We deduce that judicious control of etching time or otherwise SiNWs’ length is the key to ensure better optical and electrical properties of SiNWs. Our findings demonstrate that shorter SiNWs are much more optically and electrically active which is auspicious for the use in optoelectronic devices and solar cells applications.

Atomic packing characteristics and electronic structures of Si nanowires from density functional tight binding calculations

Abstract The atomic packing and electrical properties of silicon nanowires are of great significance when advancing novel optoelectrical and thermoelectric materials. Atom packing and electrical structures in silicon nanowires of the same thickness but different widths were studied by density functional tight binding (DFTB) calculations. The variations of average energy per atom, pair distribution function, bond length, bond angle, Mulliken gross population, and electronic structure were investigated. The periodic atomic rearrangements occur in the surface of these nanowires, and there are different patterns seen when decreasing the width. In rearranged surfaces, the atoms present regular arrangement in dimers along the direction, whereas in the other surfaces, interval dimers and trimers appear. The surface structures affect the charge distribution and electronic structures in these nanowires with different packing patterns.

Nanoscale Mechanical and Mechanically-Induced Electrical Properties of Silicon Nanowires

Molecular dynamics (MD) simulation was employed to examine the deformation and phase transformation of mono-crystalline Si nanowire (SiNW) subjected to tensile stress. The techniques of coordination number (CN) and centro-symmetry parameter (CSP) were used to monitor and elucidate the detailed mechanisms of the phase transformation throughout the loading process in which the evolution of structural phase change and the dislocation pattern were identified. Therefore, the relationship between phase transformation and dislocation pattern was established and illustrated. In addition, the electrical resistance and conductivity of SiNW were evaluated by using the concept of virtual electric source during loading and unloading similar to in situ electrical measurements. The effects of temperature on phase transformation of mono-crystalline SiNWs for three different crystallographically oriented surfaces were investigated and discussed. Simulation results show that, with the increase of applied stress, the dislocations are initiated first and then the phase transformation such that the total energy of the system tends to approach a minimum level. Moreover, the electrical resistance of (001)- rather than (011)- and (111)-oriented SiNWs was changed before failure. As the stress level of the (001) SiNW reaches 24 GPa, a significant amount of metallic Si-II and amorphous phases is produced from the semiconducting Si-I phase and leads to a pronounced decrease of electrical resistance. It was also found that as the temperature of the system is higher than 500 K, the electrical resistance of (001) SiNW is significantly reduced through the process of axial elongation.

(Invited) Nanosensors for Electrical Interrogation of Tissue and Cells

The interface between nanoscale electronic devices and biological systems enables interactions at length-scales natural to biology, maximizing communication between these two diverse yet complementary systems. Nanostructures and nanostructured substrates show enhanced coupling to artificial membranes, cells, and tissue. Such nano-bio interfaces offer better sensitivity and spatial resolution as compared to conventional planar structures. I will present the electrical properties of silicon nanowires (SiNWs) interfaced with embryonic chicken hearts and cultured cardiomyocytes. Utilizing the bottom-up approach enabled subcellular electrical recordings using the smallest reported device ever and thus exceeded the spatial and temporal resolution limits of other electrical recording techniques. I will discuss the synthetic breakthrough and novel fabrication required to realize the first new electronic measurement tool for intracellular measurements since patch-clamp of the 1970s – a truly three-dimensional nanoscale transistor. Finally, I will discuss my group’s current efforts to overcome the limits of cell-nanodevices interfaces. We are tackling these challenges through unique materials synthesis and device platform geometries. The exceptional synthetic control and flexible assembly of nanomaterials provides powerful tools for fundamental studies and applications in life science, and opens up the potential of merging active transistors with cells such that the distinction between nonliving and living systems is blurred.

Controlling the Size of Interior Core of Silicon Nanowires

As the physical and electrical properties of silicon nanowires (SiNWs) are determined by their dimension, it is necessary to control their dimension to integrate them in a device. SiNWs were synthesized via Vapor-Liquid-Solid (VLS) mechanism in hot-wire chemical vapor process (HWCVP) technique using silane as a Si source and Sn as a catalyst. Different sizes of nano-template have been made by depositing of different amount of Sn using thermal evaporation method. The size of nano-template is found to be increased with the quantity of Sn. The diameter of resulted SiNWs depends on the size of the nano-template and it increases with the nano-template size. However, the diameter of SiNWs is found to be much larger than the used nano-template which is due to the deposition of silicon film on the sidewalls of the growing SiNWs. It is demonstrated here that the diameter of the interior core of SiNWs can be controlled desirable by adjusting the size of the nano-template.

Impact of the oxide layer on the electrical properties of silicon nanowires fabricated by metal‐assisted chemical etching

Silicon nanowires (SiNWs) have been obtained by metal‐assisted chemical etching (MACE) method from a monocrystalline Si substrate (100). The SiNWs were fabricated by etching the entire thickness of the silicon wafer, obtaining an extraordinary density of monocrystalline long SiNWs with lengths up to 300 microns and diameters ranging from 100 to 500 nm. Once fabricated, SiNWs were dispersed in ethanol. The structure, chemical composition, and surface morphology of the resulting SiNWs were characterized by field emission scanning electron microscopy, transmission electron microscopy, and energy‐dispersive X‐ray spectroscopy. Through these techniques, it was observed that the crystalline core of the nanowires was surrounded by an amorphous layer, which is thicker in the bigger SiNWs. By the chemical analysis of this amorphous layer it was determined that its composition is mainly silicon oxide. To measure the SiNWs electrical properties, single nanowire devices were fabricated aligning nanowires by AC dielectrophoresis between pre‐patterned electrodes. The I–V characteristics of SiNWs were obtained by this method. It was observed that the surface oxide layer produced during the MACE process strongly influences on the electrical conductivity of the SiNWs, producing larger currents in the thinnest nanowires than in the thickest ones, a counter intuitive result that can contribute to the optimization of the MACE process for industrial applications.

Nanowire nanoelectronics: Building interfaces with tissue and cells at the natural scale of biology

The interface between nanoscale electronic devices and biological systems enables interactions at length scales natural to biology, and thus should maximize communication between these two diverse yet complementary systems. Moreover, nanostructures and nanostructured substrates show enhanced coupling to artificial membranes, cells, and tissue. Such nano–bio interfaces offer better sensitivity and spatial resolution as compared to conventional planar structures. In this work, we will report the electrical properties of silicon nanowires (SiNWs) interfaced with embryonic chicken hearts and cultured cardiomyocytes. We developed a scheme that allowed us to manipulate the nanoelectronic to tissue/cell interfaces while monitoring their electrical activity. In addition, by utilizing the bottom-up approach, we extended our work to the subcellular regime, and interfaced cells with the smallest reported device ever and thus exceeded the spatial and temporal resolution limits of other electrical recording techniques. The exceptional synthetic control and flexible assembly of nanowires (NWs) provides powerful tools for fundamental studies and applications in life science, and opens up the potential of merging active transistors with cells such that the distinction between nonliving and living systems is blurred.

Effect of thermal treatments on the morphological and optoelectronic properties of the silicon nanowires

This work presents additional arguments about the enhancement of optical and electrical properties of SiNWs obtained by chemical etching and the beneficial effect of the formation of ultrathin film of SiO2 by a heat treatment at 900 and 1000 °C reported recently by Karyaoui et al. in [Eur. Phys. J. Appl. Phys. 58 , 20103 (2012)]. In the actual study, we report the effect of this thermal oxidation treatment on the morphological and optoelectronic properties of silicon nanowires (SiNWs). The SEM and AFM observations exhibit indeed a remarkable change of the surface shape after this oxidation. On the other hand, the LBIC measurements of the SiNWs reveal that the thermal treatment improves the optoelectronic response at 900 °C and the effective diffusion length increases from 150 μ m for untreated SiNWS to 235 μ m after thermal treatment.

Effect of rapid oxidation on optical and electrical properties of silicon nanowires obtained by chemical etching

In the present work, we report the investigation of passivated silicon nanowires (SiNWs) having an average radius of 3.7 μ m, obtained by chemical etching of p -type silicon ( p -Si). The surface passivation of the SiNWs was performed through a rapid oxidation conducted under a controlled atmosphere at different temperatures and durations. The morphology of the SiNWs was examined using a scanning electron microscope (SEM) that revealed a wave-like structure of dense and vertically aligned one-dimensional silicon nanostructures. On the other hand, optical and electrical characterizations of the SiNWs were studied using a UV-Vis-NIR spectrometer, the Fourier transform infrared spectroscopy (FTIR) and I - V measurements. The reflectance of SiNWs has been dropped to approximately 2% in comparison to that of bare p -Si. This low reflectance slightly increased after carrying out the rapid thermal annealing. The observed behavior was attributed to the formation of a SiO 2 layer, as confirmed by FTIR measurements. Finally, the electrical measurements have shown that the rapid oxidation, at certain conditions, contributes to the improvement of the electrical responses of the SiNWs, which can be of great interest for photovoltaic applications.

Surface Defects-Induced p-type Conduction of Silicon Nanowires

The fundamental properties of silicon nanowires (SiNWs) are highly dependent on dimension and surface states. Despite many studies of the surface effects on the important properties of SiNWs, the understanding of the interrelation between surfaces and properties remains unclear. Herein we used SiNWs etched from Si wafer as a paradigm to study the relationship of surface states and electrical properties of SiNWs. We showed that, besides hydrogen, SiNW surfaces also consist of adsorbed carbon species, water molecules, and surface defects (Pb center) with a spin density of Cspin = 9.7 × 1012 mg–1. Our first-principle calculations revealed that surface defects including Pb, Pb0, and Pb1, similar to H-defect dangling bonds, can provide acceptor levels to trap electrons, and account for the conversion of transport properties from intrinsic to p-type conduction in SiNWs. We further revealed that SiNW with a diameter of tens to 100 nm would show obvious p-type conduction. Additionally, our theoretical simulation showed that water molecule could increase p-type conduction by lowering the defect energy. Low-temperature I–V measurements showed the defect ionization energy in the p-type SiNW at 36.4 meV.

Atomically Smooth p-Doped Silicon Nanowires Catalyzed by Aluminum at Low Temperature

Silicon nanowires (SiNWs) are powerful nanotechnological building blocks. To date, a variety of metals have been used to synthesize high-density epitaxial SiNWs through metal-catalyzed vapor phase epitaxy. Understanding the impact of the catalyst on the intrinsic properties of SiNWs is critical for precise manipulation of the emerging SiNW-based devices. Here we demonstrate that SiNWs synthesized at low-temperature by ultrahigh vacuum chemical vapor deposition using Al as a catalyst present distinct morphological properties. In particular, these nanowires are atomically smooth in contrast to rough {112}-type sidewalls characteristic of the intensively investigated Au-catalyzed SiNWs. We show that the stabilizing effect of Al plays the key role in the observed nanowire surface morphology. In fact, unlike Au which induces (111) and (113) facets on the nanowire sidewall surface, Al revokes the reconstruction along the [112] direction leading to equivalent adjacent step edges and flat surfaces. Our finding sets the lower limit of the Al surface density on the nanowire sidewalls at ∼2 atom/nm(2). Additionally, despite using temperatures of ca. 110-170 K below the eutectic point, we found that the incorporation of Al into the growing nanowires is sufficient to induce an effective p-type doping of SiNWs. These results demonstrate that the catalyst plays a crucial role is shaping the structural and electrical properties of SiNWs.

Growth, Thermodynamics, and Electrical Properties of Silicon Nanowires

ADVERTISEMENT RETURN TO ISSUEPREVReviewNEXTGrowth, Thermodynamics, and Electrical Properties of Silicon Nanowires†V. Schmidt*‡, J. V. Wittemann‡, and U. Gösele‡§∥View Author Information Max Planck Institute of Microstructure Physics, Halle, Germany, and School of Engineering, Duke University, Durham, North Carolina* To whom correspondence should be addressed. E-mail: [email protected]†This article is dedicated to the memory of Professor Ulrich Gösele.‡MPI of Microstructure Physics.§Duke University.∥Deceased.Cite this: Chem. Rev. 2010, 110, 1, 361–388Publication Date (Web):January 13, 2010Publication History Received7 April 2009Published online13 January 2010Published inissue 13 January 2010https://doi.org/10.1021/cr900141gCopyright © 2010 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views9203Altmetric-Citations436LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (3 MB) Get e-AlertsSUBJECTS:Catalysts,Crystallization,Nanowires,Silicon,Wires Get e-Alerts

Silicon Nanowires: A Review on Aspects of their Growth and their Electrical Properties.

This paper summarizes some of the essential aspects of silicon-nanowire growth and of their electrical properties. In the first part, a brief description of the different growth techniques is given, though the general focus of this work is on chemical vapor deposition of silicon nanowires. The advantages and disadvantages of the different catalyst materials for silicon-wire growth are discussed at length. Thereafter, in the second part, three thermodynamic aspects of silicon-wire growth via the vapor-liquid-solid mechanism are presented and discussed. These are the expansion of the base of epitaxially grown Si wires, a stability criterion regarding the surface tension of the catalyst droplet, and the consequences of the Gibbs-Thomson effect for the silicon wire growth velocity. The third part is dedicated to the electrical properties of silicon nanowires. First, different silicon nanowire doping techniques are discussed. Attention is then focused on the diameter dependence of dopant ionization and the influence of interface trap states on the charge carrier density in silicon nanowires. It is concluded by a section on charge carrier mobility and mobility measurements.

On the properties of surface reconstructed silicon nanowires

We study by means of density-functional calculations the role of lateral surfacereconstructions in determining the electrical properties of silicon nanowires. The different lateral reconstructions are explored by relaxing all thenanowires with crystalline bulk silicon structure and all possible ideal facets thatcorrespond to an average diameter of 1.5 nm. We show that the reconstruction inducesthe formation of ubiquitous surface states that make the wires semi-metallic ormetallic.