TB_Sim is a k.p and tightbinding code developed at CEA Grenoble. It is able to compute the structural, electronic, optical and transport properties of various kinds of nanostructures such as semiconductor nanocrystals, nanowires and carbon nanotubes. 


The principle of the tightbinding method is to expand the wave functions of the electrons in a basis of atomic orbitals. Indeed, the physics of silicon for example is dominated (around the band gap) by the hybridization of the 3s, 3p (and 3d) orbitals of the Si atoms (see Fig. 1). Since atomic orbitals are localized in real space, their interactions are limited to a few nearest neighbors. Computing these interactions with a selfconsistent ab initio method such as density functional theory is, however, very expensive for a few thousand atoms. The interactions between atomic orbitals are, nonetheless, usually close to bulk interactions in such systems. In the semiempirical tightbinding framework, they are therefore adjusted to reproduce the bulk band structures, then transferred to the nanostructures. This approach is very efficient and accurate enough when the bonding does not differ too much from the bulk reference.
Fig. 1: (top) From silicon atoms to bulk silicon: links between then atomic orbitals and the bulk band structure. (bottom) The s, p, and d orbitals. 
Since the interactions between atomic orbitals are limited to first, second or third nearest neighbors, the tightbinding hamiltonian is "sparse" (most matrix elements are zero): This makes the tightbinding method very appropriate for the design of "order N" methods whose computational cost scales linearly with the number N of atoms. For example, the cost of a matrix/vector product scales as N for a sparse tightbinding hamiltonian instead of N^{2} for a dense matrix. The optical properties of a million atom system can therefore be computed within a few hours on a desktop computer.
Fig. 2: Multiscale modelling  Ab initio calculations on few atom systems are used to provide inputs to semiempirical atomistic methods such as tightbinding, then to largescale calculations based, e.g., on finiteelement modelling. These methods can also be coupled together to describe different parts of the system with very different length or time scales. 
As an atomistic approach, the tightbinding method is well suited to the description of atomicscale features such as impurities, defects, electronphonon coupling, etc... It can be used in a multiscale modelling strategy as a transition from ab initio to largescale finite element modelling (see Fig. 2).
Fig. 3: The capabilities of TB_Sim. 
The capabilities of TB_Sim are summarized on Fig. 3. In particular, TB_Sim features:
The code is parallelized for OpenMP and MPI architectures. It can also make use of graphics cards (GPU) accelerators. TB_Sim has received in 2012 the third prize in the BullFourier contest (high performance computing) for its parallel performances.
Coordinator and contact person:
Developers:
Other contributors:
Fig. 4: (left) The electron (a) and hole (b) energy levels in InAs/InP nanowire heterostructures with radius R=10 nm as a function of the thickness t_{InAs} of the InAs layer. (right) The corresponding conduction band wave functions for t_{InAs}=4 nm and t_{InAs}=16 nm. From Y. M. Niquet and D. Camacho Mojica, "Quantum dots and tunnel barriers in InAs/InP nanowire heterostructures: Electronic and optical properties", Phys. Rev. B 77, 115316 (2008). 
Fig. 5: (top) (a) Density of states of an ideal (dashed line) and borondoped graphene sheets for several boron concentrations C_{d}. (b, c) Local density of states on a boron and nitrogen impurity. (bottom) (a) Semiclassical conductivity at room temperature as a function of the carrier energy and C_{d}. Dotted lines correspond to the zero temperature limit. (b) Semiclassical conductivities for electrons and holes as a function of the carrier density and for C_{d}=0.5%. From A. Lherbier, X. Blase, Y. M. Niquet, F. Triozon and S. Roche, "Charge transport in chemically doped 2D graphene", Phys. Rev. Lett. 101, 036808 (2008). 
Electronic structure and transport properties of Si nanotubes.
J. Li, T. Gu, C. Delerue and Y. M. Niquet,
Journal of Applied Physics 114, 053706 (2013).
Residual strain and piezoelectric effects in passivated GaAs/AlGaAs coreshell nanowires.
M. Hocevar, L. T. T. Giang, R. Songmuang, M. den Hertog, L. Besombes, J. Bleuse, Y. M. Niquet and N. T. Pelekanos,
Applied Physics Letters 102, 191103 (2013).
Highly defective graphene: A key prototype of twodimensional Anderson insulators.
A. Lherbier, S. Roche, O. A. Restrepo, Y. M. Niquet, A. Delcorte and J. C. Charlier,
Nano Research 6, 326 (2013).
Performances of strained nanowire devices: Ballistic versus scatteringlimited currents.
V. H. Nguyen, F. Triozon, F. D. R. Bonnet and Y. M. Niquet,
IEEE Transactions on Electron Devices 60, 1506 (2013).
Size dependence of the exciton transitions in colloidal CdTe quantum dots.
E. Groeneveld, C. Delerue, G. Allan, Y. M. Niquet and C. de Mello Donega,
Journal of Physical Chemistry C 116, 23160 (2012).
Carrier
mobility in strained Ge nanowires.
Y.
M. Niquet and C. Delerue,
J. Appl. Phys. 112,
084301 (2012).
Effects
of strains on the mobility in silicon nanowires.
Y.
M. Niquet, C. Delerue and C. Krzeminski,
Nano Letters 12,
3545 (2012).
Strain
state of GaN nanodisks in AlN nanowires studied by medium energy ion
spectroscopy.
D.
Jalabert, Y. Curé, K. Hestroffer, Y. M. Niquet and B.
Daudin,
Nanotechnology 23,
425703 (2012).
Atomistic
Borondoped graphene fieldeffect transistors: A route toward
unipolar characteristics.
P.
Marconcini, A. Cresti, F. Triozon, G. Fiori, B. Biel, Y. M. Niquet,
M. Macucci and S. Roche,
ACS Nano 6,
7942 (2012).
Gatecontrollable
negative differential conductance in graphene tunneling
transistors.
V. H.
Nguyen, Y. M. Niquet and P. Dollfus,
Semicond. Sci. Technol. 27,
105018 (2012).
Transport
properties of graphene containing structural defects.
A.
Lherbier, S. M. M. Dubois, X. Declerck, Y. M. Niquet, S. Roche and
J. C. Charlier,
Physical Review B 86,
075402 (2012).
Detection
of a large valleyorbit splitting in silicon with twodonor
spectroscopy.
B. Roche, E.
DupontFerrier, B. Voisin, M. Cobian, X. Jehl, R. Wacquez, M. Vinet,
Y. M. Niquet and M. Sanquer,
Physical Review Letters 108,
206812 (2012).
Impuritylimited
mobility and variability in gateallaround silicon nanowires.
Y.
M. Niquet, H. Mera and C. Delerue,
Applied Physics Letters 100,
153119 (2012).
Fully
atomistic simulations of phononlimited mobility of electrons and
holes in <001>, <110> and
<111>oriented Si nanowires.
Y. M. Niquet,
C. Delerue, D. Rideau and B. Videau,
IEEE Transactions on
Electron Devices 59, 1480
(2012).
Band
offsets, wells, and barriers at nanoscale semiconductor
heterojunctions.
Y. M. Niquet and C. Delerue,
Physical
Review B 84, 075478 (2011).
Twodimensional
graphene with structural defects: Elastic mean free path, minimum
conductivity, and Anderson transition.
A. Lherbier, S.
M. M. Dubois, X. Declerck, S. Roche, Y. M. Niquet and J. C.
Charlier,
Physical Review Letters 106,
046803 (2011).
Atomistic
modeling of electronphonon coupling and transport properties in
ntype [110] silicon nanowires.
W. Zhang, C. Delerue, Y.
M. Niquet, G. Allan and E. Wang,
Physical Review B 82,
115319 (2010).
Charged
impurity scattering and mobility in gated silicon nanowires.
M.
P. Persson, H. Mera, Y. M. Niquet, C. Delerue and M.
Diarra,
Physical Review B 82, 115318 (2010).
The
structural properties of GaN/AlN coreshell nanocolumn
heterostructures.
K. Hestroffer, R. Mata, D.
Camacho, C. Lecrere, G. Tourbot, Y. M. Niquet, A.
Cros, C. Bougerol, H. Renevier and B.
Daudin,
Nanotechnology 21,
415702 (2010).
Accumulation
capacitance of narrow band gap metaloxidesemiconductor
capacitors.
E. Lind, Y. M. Niquet, H. Mera and L. E.
Wernersson,
Applied Physics Letters 96,
233507 (2010).
Stark
effect in GaN/AlN nanowire heterostructures: Influence of strain
relaxation and surface states.
D. Camacho and Y. M.
Niquet,
Physical Review B 81, 195313
(2010).
Quantum
transport in graphene nanoribbons: effects of edge reconstruction
and chemical reactivity.
S. Dubois, A. LopezBezanilla, A.
Cresti, F. Triozon, B. Biel, J.C. Charlier and S. Roche,
ACS
Nano 4, 1971 (2010).
Elastic
strain relaxation in GaN/AlN nanowire superlattice.
O.
Landré, D. Camacho, C. Bougerol, Y. M. Niquet, V.
FavreNicolin, G. Renaud, H. Renevier and B.
Daudin,
Physical Review B 81, 153306
(2010).
Analysis
of strain and stacking faults in single nanowires using Bragg
coherent diffraction imaging.
V. FavreNicolin, F.
Mastropietro, J. Eymery, D. Camacho, Y. M. Niquet, B.
M. Borg, M. E. Messing, L. E. Wernersson, R. E.
Algra, E. P. A. M. Bakkers, T. H. Metzger, R. Harder
and I. K. Robinson,
New Journal of Physics 12, 035013
(2010).
Simulation,
modeling and characterization of quasiballistic transport in
nanometer sized field effect transistors: from TCAD to atomistic
simulation.
S. Roche, T. Poiroux, G. Lecarval, S.
Barraud, F. Triozon, M. Persson and Y. M.
Niquet,
International Journal of Nanotechnology 7, 348
(2010).
Application
of Keating's valence force field model to nonideal wurtzite
materials.
D. Camacho and Y. M. Niquet,
Physica E 42,
1361 (2010).
The
structural properties of GaN insertions in GaN/AlN nanocolumn
heterostructures.
C. Bougerol, R. Songmuang, D.
Camacho, Y. M. Niquet, R. Mata, A. Cros and B.
Daudin,
Nanotechnology 20,
295706 (2009).
Chemically
induced mobility gaps in graphene nanoribbons: a route for upscaling
device performances.
B. Biel, F. Triozon, X. Blase and S.
Roche,
Nano Letters 9,
2725 (2009).
Chemical
functionalization effects on armchair graphene nanoribbon
transport.
A.
LopezBezanilla, F. Triozon and S. Roche,
Nano
Letters 9, 2537
(2009).
Carbon
nanotube chemistry and assembly for electronic devices.
V.Derycke,
S.Auvray, J.Borghetti, C.L.Chung, R.Lefèvre,
A.LopezBezanilla, K.Nguyen, G.Robert, G.Schmidt,
C.Anghel, N.Chimot, S.Lyonnais, S.Streiff,
S.Campidelli, P.Chenevier, A.Filoramo, M.
F.Goffman, L.GouxCapes, S.Latil, X.Blase,
F.Triozon, S.Roche and J.P.Bourgoin,
ComptesRendus
Physique 10, 330
(2009).
Multiscale
simulation of carbon nanotube devices.
C.
Adessi, R.Avriller,
X.Blase, A.Bournel, H.Cazin d?Honincthun,
P.Dollfus, S.Frégonèse, S.GaldinRetailleau,
A.LópezBezanilla, C.Maneux, H.Nha Nguyen,
D.Querlioz, S.Roche, F.Triozon and
T.Zimmer,
ComptesRendus Physique 10,
305 (2009).
Anomalous
doping effects on charge transport in graphene nanoribbons.
B.
Biel, X. Blase, F. Triozon and S. Roche,
Physical
Review Letters 102,
096803 (2009).
Effect
of the chemical functionalization on charge transport in carbon
nanotubes at the mesoscopic scale.
A. LopezBezanilla, F.
Triozon, S. Latil, X. Blase and S. Roche,
Nano
Letters 9,
940 (2009).
Band
structure effects on the scaling properties of [111] InAs nanowire
MOSFETs.
E.
Lind, M. Persson, Y. M. Niquet and L. E. Wernersson,
IEEE
Transactions on Electron Devices 56, 201
(2009).
Orientational
dependence of charge transport in disordered silicon nanowires.
M.
P. Persson, A. Lherbier, Y. M. Niquet, F. Triozon and S.
Roche,
Nano Letters
8, 4146
(2008).
Charge
transport in chemically doped 2D graphene.
A. Lherbier, X.
Blase, Y. M. Niquet, F. Triozon and S. Roche,
Physical
Review Letters 101, 036808 (2008).
Scanning
tunnelling spectroscopy of cleaved InAs/GaAs quantum dots at low
temperatures.
A. Urbieta, B. Grandidier, J. P.
Nys, D. Deresmes, D. Stiévenard, A. Lemaître, G.
Patriarche and Y. M. Niquet,
Physical Review B. 77, 155313
(2008).
Screening
and polaronic effects induced by a metallic gate and a surrounding
oxide on donor and acceptor impurities in silicon nanowires.
M.
Diarra, C. Delerue, Y. M. Niquet and G. Allan,
Journal
of Applied Physics 103, 073703 (2008).
Quantum
dots and tunnel barriers in InAs/InP nanowire
heterostructures:Electronic and optical properties.
Y.
M. Niquet and D. Camacho Mojica,
Physical Review B 77, 115316
(2008).
Quantum
transport length scales in siliconbased semiconducting
nanowires:Surface roughness effects.
A.
Lherbier, M. P. Persson, Y. M. Niquet, F. Triozon and
S. Roche,
Physical Review B. 77, 085301 (2008).
Transport
length scales in disordered graphenebased materials:Strong
localization regimes and dimensionality effects.
A.
Lherbier, B. Biel, Y. M. Niquet and S. Roche,
Physical
Review Letters 100, 036803 (2008).
Strain
and shape of epitaxial InAs/InP nanowires measured by grazing
incidence Xray techniques.
J. Eymery, F. Rieutord, V.
FavreNicolin, O. Robach, Y. M. Niquet, L.
Fröberg, T. Mårtensson and L. Samuelson,
Nano Letters
7, 2596
(2007).
Effects
of a shell on the electronic properties of nanowire
superlattices.
Y.
M. Niquet,
Nano
Letters 7, 1105
(2007).
Quantum
communication with quantum dots spins.
C.
Simon, Y. M. Niquet, X. Caillet, J. Eymery, J.
P. Poizat and J. M. Gérard,
Physical Review B 75, 081302(R)
(2007).
Ionization
energy of donor and acceptor impurities in semiconductor
nanowires:Importance of dielectric confinement.
M.
Diarra, Y. M. Niquet, C. Delerue and G. Allan,
Physical
Review B 75, 045301
(2007).
Electronic
and optical properties of InAs/GaAs nanowire
superlattices.
Y. M. Niquet,
Physical
Review B 74, 155304
(2006).
Electronic
structure of semiconductor nanowires.
Y. M. Niquet, A.
Lherbier, N. H. Quang, M. V. FernandezSerra, X.
Blase and C. Delerue,
Physical
Review B 73, 165319
(2006).
More publications and links to journal sites can be found here.
Last update: October 22, 2013.