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Proceedings of the 4th International Conference on
Nanostructures (ICNS4)12-14 March 2012, Kish Island, I.R. Iran
Abstract Book|INST| Sharif University of Technology|84
APP 001
APP
APP 002
In this work, we present atomic scale simulation of junctionless semi-
conducting singlewalled carbon nanotubes eld effect transistors
(CNTFETs) and compare their performance to silicon nanowire
(SiNW) transistors with similar dimensions. The energy dispersions
relations for ptype SiNW and CNT are compared. The response of the
transistors to sourcedrain bias and gate voltage is explored. Consider-
ing charge selfconsistency in the transport calculations enables us to
provide quantitative predictions of subthreshold slope.
Keywords:Ab initio calculations; Carbon nanotube; Electronic transport;Junctionless transistor; Nanowire
L. Ansari*, B. Feldman, G. Fagas, J. P. Colinge, and J. C. Greer
Tyndall National Institute, University College Cork, Lee Maltings, Cork, Ireland
Invesgaon of the Performance of Carbon Nanotubeand Silicon Nanowire Junconless Transistors using
FirstPrinciple Calculaons
solving 2D and 3D Maxwells equations, Newtonian equations of mo-
tion, piezoelectric phenomena, quantum devices, photonic, phononic,
and MEMS applications. In particular, it will be shown that, wherever
conventional approaches perform rather poorly in anisotropic media,
the proposed method powerfully maintains its rigor and elegance. The
method applies to problems with scales ranging from space antennas to
nano-antennas. The presentation continues with a discussion of authors
most recent results on the genesis of differential operators in mathemat-
ical physics and the construction of physicsbased Dirac delta functions
and their profound implications in modelling and simulation of classical
and quantum devices. Furthermore, the construction of problem-specif-
ic, physics-based analysis and synthesis functions including Wannier
functions will be discussed. The presentation concludes by revisiting
Feynmans propagators in the light of newly constructed Dirac delta
functions, and speculations for future research.
keywords: Small-scale devices; Boundary element method
The application of the popular Boundary Element Method (BEM) to
two- and three-dimensional near-eld phenomena in small-scale de-
vice modelling and ` simulation is typically plagued by a number of
computational difculties which may severely obscure the accuracy of
the resulting numerical data and their interpretation. The roots for these
difculties can be traced back to the strongand hyper-strong singulari-
ties of the involved dyadic Greens functions (GFs) and their spatial
derivatives evaluated in the direction normal to the bounding surface
of the problem of interest. Conventionally, the GFs are rst constructed
in spatial domain and then their near-eld asymptotic expansions are
determined a procedure which is inherently susceptive to large nu-
merical errors whenever the GFs are not available in closed-form. The
resulting (spatial domain) near-eld asymptotic expansions are nally
used to calculate the so-called self-action termsand the terms describ-
ing the interaction between closely-located boundary elements.
In this presentation an alternative procedure will be proposed which al-
lows the computation of self-action and interaction terms easily, robustly
and accurately, and thus, responds to the shortcomings innately present
in conventional techniques. The method permits gaining deep insight
into the nature of the nearelds in general, and consists of a number of
easy-to-implement steps which can be automated straightforwardly, ir-
respective of the availability of the involved dyadic GFs in closed-form.
The proposed method comprises the following essential steps:
(i) Diagonalize the governing and constitutive equations with respect
to a chosen direction in space.
(ii) Transform the resulting equations into the wave-number domain
(Wdomain).
(iii) Utilise a novel procedure, proposed in this presentation, for the de -
termination of the asymptotic expansions of the eigenpairs in Wdomain.
(Thereby, an obviously overlooked fact about generalized eigenfunc-
tions in the static limit will be discussed.)
(iv) Employ the resulting terms and construct the asymptotic expansions
of GFs in W-domain. It is this step, which constitutes the basic result of
the presentation: We observe that certain unwanted terms cancel out
automatically already in W-domain, a property which will be referred
to as the natural regularisation. A plausible physics-based explanation
for this effect will be provided. Furthermore, a relationship will be estab-
lished between this effect and the near-elds in spatial domain.(v) Beside natural regularization further schemes will be introduced to
handle the remaining singularities.
(vi) The W-domain asymptotic terms of the eigenpairs enable the con-
struction of asymptotic expansions of the GFs in W-domain.
(vii) The resulting functions, which can be transformed into real-space
simply-by-inspection, constitute the spatial domain near-eld as-
ymptotic expansion terms of GFs. Using the above theory, Universal
Functions (UFs) will be introduced for the calculation of interaction
elements in BEM applications. The UFs need to be calculated only
once and can be utilised for arbitrary geometry and frequencies. It turns
out that UFs are extraordinary smooth and thus convenient for data
processing and storage. The above steps will be illustrated in terms of
Alireza Baghai-Wadji
Electrical and Computer Engineering, RMIT University
Building 10, 376-392 Swanston Street, Melbourne
GPO Box 2476V, Melbourne VIC 3001 Australia
Zooming into the Near-eld: Customized Modelling and
Simulaon of Small-scale Devices
APP 003
This paper presents a comparative study on carbon nanotube led-effect transistors (CNTFETs) in terms of transfer and output charac-
teristics, transconductance, average velocity and quantum capacitance
with strain effect using a two-dimensional model. The theoretical work
predicts that the chirality and strain can both inuence on the bandgap
of a CNT. Chirality of a CNT expresses by (m, n), m-n=3l+p, thatp can
be -1, 0 or 1. In order to present the strain effect on band gap, it is sup-
posed thatp=1 which causes Eg be larger than the ideal diameter-based
calculated Eg. In this condition, the simulation results show that trans-
fer and output characteristics, transconductance and average velocity
at the top of the barriers decrease and quantum capacitance increases.
Keywords: Carbon nanotube; Strain effect; Field-effect transistor;
Two-dimensional (2-D) model
M. Fallaha*, R. Faezb, A. Sadrc
aDepartment of Electronics, Islamic Azad University of Qazvin, Qazvin, Iranb Electrical Engineering Faculty, Sharif University of Technology, Tehran, IrancElectrical Engineering Faculty, Iran University of Science &Technology,
Tehran, Iran
The Eect of Strain on Carbon Nanotube Filed EectTransistors (FETs)