New Method For First Principles Modeling of Electron Transport through Nanoelectronic Devices
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New Method For First Principles Modeling Of Electron Transport Through Nanoelectronic Devices. Mads Brandbyge, Kurt Stokbro, Jeremy Taylor, Jose-Luis Mozos1 and Pablo Ordej´on1 Mikroelektronik Centret, Technical University of Denmark, Lyngby, Denmark; 1 Institut de Ciencia de Materials de Barcelona - CSIC Campus de la U.A.B., Spain. ABSTRACT In this paper we present a new theoretical method for modeling electron transport through nanostructures under non-equilibrium conditions. The electronic structure of the nanostructures are modeled from first principles and are described selfconsistently under the non-equilibrium conditions by means of a Green’s function technique. The method is used to calculate the electron transport through benzene-dithiolate connected to two gold chains.
INTRODUCTION Part of the success of silicon technology is related to the development of reliable tools for device modeling. If nanoelectronics shall mature into replacing silicon it is necessary to develop new techniques that reliably model the transport in the devices. The dimensions of nanoelectronic components are such that it is important to take into account the atomic structure of the device and quantum chemical methods are needed for an accurate description. Since the devices operate under non-equilibrium conditions, quantum chemical methods must be developed that take into account the change in the electronic structure when a current is flowing through the device. In this paper we present a new method for first principles quantum chemical modeling of nanoelectronic devices under non-equilibrium conditions. The method is based on the non-equilibrium Green’s function technique [1] which has been interfaced with the SIESTA electronic structure package [2] in such a way that the density matrix of the system is calculated selfconsistently under the non-equilibrium conditions [3]. In this paper we will give a brief overview of the method and present results obtained for electron transport through benzenedithiolate between two gold chains.
THE METHOD We will consider the following situation: Two electrodes, left and right, are coupled via a contact region. All matrix elements of the Hamiltonian or overlap integrals between states situated in different electrodes are zero so the coupling takes place only via the contact region. The system can be separated into three parts, Left (L), Contact (C ) and Right (R). We will fix the overlap and matrix elements of the Hamiltonian to bulk values in region L and R.
D9.25.1
The part of the Left and Right electrode that has matrix elements with the region C will be denoted IL , IR , respectively. The coupling of IL and IR with the remaining part of the infinite electrodes is taken into account using selfenergies, L and R , in the Hamiltonian, thus we only need to include the atoms in region I L , C , and IR . In the direction parallel to the interface we impose periodic boundary conditions. From the Hamiltonian we can obtain the retarded Green’s function of the system using
0 [E S H (E )] B [
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