暑期系列前沿讲座(1)
Scenarios for Molecular Electronics
 

Speaker  Prof. Jorge M. Seminario

Texas A&M University

Professor  of Chemical Engineering and
Professor of Electrical Engineering
Texas A&M University
3122 TAMU
College Station, TX 77843-3122

     2005年74(周一) 下午1:30-2:30 (one hour)

   点:  计算中心B325

Abstract:

The nanoCell is one of the most important and viable concepts for the development of electronics beyond the deterministic or lithographic approach of present C-MOS integrated circuits. Very few scenarios have been proposed to use molecular-based devices to bypass problems undermining miniaturization or scaling-down processes for integrated circuits through the introduction of a revolutionary approach in which molecules or nanoclusters of atoms are used to perform logical operations complementing or extending the capabilities of deterministic ones. The nanoCell concept takes advantage of the great ability of chemistry to synthesize molecules with a arrangements of atoms in a molecule with tolerances of fractions of nanometer; such a tolerance is far from the reach of any IC fabrication technique, which presently feature sizes in the order of 45 nanometers and limited to practically two dimensions. It has been already shown in the literature that even two single molecules with strong non linear characteristics can perform programmable functions and thus compensating for the lack of addressability of single molecules. However, before practical molecular circuits beyond standard lithography can be implemented, we need to develop scenarios for information coding and transfer in molecular circuits which are able to operate at integration densities and speeds orders of magnitude higher than in present integrated circuits. Initial attempts have been already proposed; however, a simply adaptation to methods being used in present microelectronics devices does not offer much hope at the atomistic and nanoscopic levels due to the large energy dissipation densities that would be needed. We have proposed two new paradigms to process and transmit information in molecular circuits that can defeat the heat dissipation problem: One is based on the characteristic vibrational behavior of molecules and clusters [1,2] and the other is based on the molecular electrostatic potentials [3,4]. It is suggested that these two scenarios can be used for molecular signal processing and transfer in molecular circuits.


 

暑期系列前沿讲座(2)
Analysis, Design, and Simulation Methods for Molecular Electronic
 

Speaker  Prof. Jorge M. Seminario

Texas A&M University

Professor  of Chemical Engineering and
Professor of Electrical Engineering
Texas A&M University
3122 TAMU
College Station, TX 77843-3122

      74(周一) 下午3:00-4:00(one hour)

   点:   计算中心B325

Abstract:

The Green's function and density functional theory (DFT) are used to study the electron transport characteristics of several types of junctions or interfaces. Our procedure follows these steps: (a) The geometry of the extended molecule is optimized using GAUSSIAN 03 program until a local minimum is obtained. Usually, several initial geometries are tried at this stage, and thus several local minima are obtained. (b) a second derivative calculation is done (usually know as "frequency calculation") to guarantee the stability of the extended molecule, those with negative force constants are re-optimized using modified initial geometries until a global minimum is obtained. (c) a series of single-point calculations of the extended molecule including the applied bias electric field are run for each point for which we want to get the I-V, thus each point of the I-V curve correspond to a full ab initio calculation; the Hamiltonian and overlap matrices in electric field are obtained. Some molecules require that a geometry optimization with an applied electric field is run since their geometry may be modified. (d) The DOS for the bulk material is obtained using the CRYSTAL 03 program. (e) A Green's function transport procedure using the Hamiltonian and overlap matrices of the extended molecule as well as the DOS of gold contact as input is used to calculate the DOS, the electron transmission probabilities, and the I-V characteristics of the molecule. Care is taken that the electron transport procedure does not ignore the chemistry of the molecule as it occurs in most of the non-equilibrium Green function procedures. Using the applied electric field in a self-consistent manner on the extended molecule assures that the chemistry of the molecule is not lost in the calculation. We need to make sure that the extended molecule is enough to create an acceptable interface to the bulk. Several results will be presented.


 

暑期系列前沿讲座(3~7)
Lectures on Understanding and Modeling Nanoelectronics
 

主讲人:  Prof. Raphael Tsu

Distinguished Professor
         Dept. of Electrical and Computer Engineering
         University of North Carolina at Charlotte
         Charlotte, NC 28223, USA

     75,6,11,12,13, 每天下午1:30-2:30 (具体内容请见摘要后)

    点: 计算中心B325

  :

The commonality between the mature quantum devices represented by Superlattices and quantum wells, and quantum dots, yet to be implemented as devices, is the wave nature of electrons.  Unlike chemistry where nanoparticles always play an important role, in electronics, the same optimistic views have serious flaws. We need to look at the pros and cons of devices operating in the quantum domain. Certainly most devices in use today will not operate when size is below few nanometers.  For example, the discreteness of electrons, even without considering quantum effects can drastically alter the classical rules governed by the use of Gauss law. We cannot simply store charges because what we can store are electrons. Contacts change the symmetry of a quantum dot but as planar contacts to quantum wells, symmetry is preserved. This very fact is at the roots of the problems with implementation of nanoelectronics. Certainly most devices in use today will not operate when size is below few nanometers. We need to look at the pros and cons of devices operating in the quantum domain. Specific lectures include:

7/5 (周二): lecture 1: Mathematical description and modeling of superlattice and quantum wells

7/6 (周三): lecture 2: Mathematical description and modeling of superlattice and quantum wells

7/11(周一): lecture 3: Dielectric constant, capacitance and doping of quantum dots

7/12(周二):lecture 4: Why do we need to include damping represented by non-Hermitian Hamiltonian

7/13(周三):lecture 5: Problems with implementation of nanoelectronics: contacts, redundancy, robustness, reliability, and most of all, finding a niche.


联系人:杨海英
Tel:   86-21-55664548
Email: hy_yang@fudan.edu.cn
 

 

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