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Latest Research


Calculating conductance of Si (111) 7 x 7 reconstructed surface by Nanodcal
Nanodcal has been applied to calculate the sheet conductivity of the Si(111)7x7 reconstructed surface to provide confirmation of recent experimental measurements. [PRL 112, 246802 (2014)].

Quantum transport with LDA+U
Nanodcal uses the LDA+U approach to analyze correlation effects in the atomic limit. This paper reports ab initio simulations of quantum transport properties of Fe/MgO/Fe trilayer structure with FeO0.5 buffer iron oxide layer,  where on-site Coulomb interaction in  the iron–oxygen layer can cause a dramatic drop of the tunnel magnetoresistance. [J. Phys. Condens. Matter 26 015002 (2014)].


Tunneling through high-k dielectric layers 
Quantum tunneling through amorphous HfO2 dielectric layer in the form of  n-Si/HfO2/Al has been analyzed by Nanodcal.  The simulated system contains 800 atoms in the scattering region. By analyzing transmission coefficients and projected density of states, microscopic physics of electron traversing the tunnel barrier with or without impurity atoms is revealed [J. Appl. Phys. 116, 023703 (2014)].


Modeling electrical control of spin in WSe2 field effect transistors by Nanodcal
Nanodcal solves spin-orbit physics within NEGF-DFT, and has been applied to study spintronics and valleytronics for FETs made of the 2D transition metal dichalcogenide WSe2. [].


Predicting device-to-device variability by Nanodsim

A new capability is released in Nanodsim for predicting device-to-device variability caused by random impurities. Quantum transport fluctuations due to disorder can now be predicted from first principles at nonequilibrium. The figure shows a calculated transmission versus electron energy for Cu interconnects. The band gives the transmission variability due to defects. [Phy. Rev. B 88, 085420 (2013)]


Modeling quantum transport in strained Si FET by Nanodsim
Nanodsim has been applied to calculate effects of strain in Si nanoFET. The parameter-free self-consistent NEGF-DFT calculations were quantitatively compared to Synopsys/Sentaurus, as shown in the figure. [IEEE Trans. Elec. Dev. 60, 3527 (2013)].



Calculating band offset of heterojunctions by Nanodsim
Nanodsim has been applied to quantitatively calculate both valance and conductoin band offset of GaAs/AlGaAs heerojunction for the entire range of the Al concentration, as shown in the figure [Appl. Phys. Lett. 102, 132109 (2013)].


Electronic structure of III-Vs by Nanodsim


 Using Nanodsim, electronic structures of all III-V zinc-blende semiconductor compounds have been calculated by DFT with the semilocal exchange [F. Tran and P. Blaha, Phys. Rev. Lett. 102, 226401 (2009)] and the linear muffin tin orbital scheme. The calculated band gaps and effective masses are quantitatively compared to the corresponding experimental data. [Phys. Rev. B 87, 235203 (2013)]


A generic tight-binding model for MoS2
A generic tight-binding (TB) model that accurately produces electronic structures for bulk, bilayer and monolayer MoS2, has recently been generated using our tool Nanoskif (not yet released). The TB model is based on Slater-Koster method with non-orthogonal sp3d5 orbitals, nearest-neighbor interactions and spin-orbit coupling [AIP ADVANCES 3, 052111 (2013)].


Simulating topological insulators by Nanodcal
Nanodcal has been applied to study topological insulators (TI). The figure shows the calculated spin-momentum locking in the helical states on the BiSe TI surface induced by strong spin-orbit coupling [Nano. Lett. 11, 2088 (2011)]. [Phys. Rev. B 85, 241402(R) (2012)].


Suppressing off-state leakage of Si nanoFET - a simulation by Nanodsim
By NEGF-DFT calculations using Nanodsim, it was shown that localized doping in nanoscale Si transistors can suppress the S/D leakage current [Phys. Rev. Lett. 109, 266803 (2012)].



Calculating conductance of metal-metal contacts by Nanodcal
/UserFiles/Image/5_20131022053224.png Nanodcal has been applied to reveal the microscopic scattering processes happening at the metal-metal contacts of gold and tungsten, and provided understanding of the experimental data [PNAS 109, 19097 (2012)].