Kin-Yip Phoa and Vivek Subramanian

EECS Department, University of California, Berkeley

Technical Report No. UCB/EECS-2008-66

May 21, 2008

http://www2.eecs.berkeley.edu/Pubs/TechRpts/2008/EECS-2008-66.pdf

As the end of the International Technology Roadmap for Semiconductors (ITRS) is approaching, supplements to the existing silicon technology are sought. Molecular electronics presents itself as one of the most promising candidates in terms of projected device dimensions. This thesis is devoted to advance the current technology towards the ultimate paradigm of single molecule transistors. Firstly, we demonstrate field effect transistors with complete FET functionality formed within a self-assembled monolayer integrating both dielectric and semiconductor functionality within the same molecule. This is an attractive structure due to the potentially idealized characteristics that are achievable due to the intra-molecular semiconductor-dielectric interface. Grazing incidence X-ray diffraction (GIXD) is used to further study the morphology and the crystallinity of the monolayer deposited on different substrates. Furthermore, first-principle calculations are employed to provide additional physical understanding of this system, as well as to model the monolayer. Initial demonstration of dielectric-integrated monolayer FETs is achieved based on the proposed monolayer system, albeit with poor characteristics.

Moreover, to complete the picture of nanoscale organic electronics, we investigate the feasibility of the [2]rotaxane molecular memory reported by Heath and Stoddart in 2002. In particular, its switching performance is probed theoretically through the evaluation and estimation of the energy landscape, the ionization potentials and the dielectric constants. However, it is found that the switching time of this molecule is greatly limited by an intrinsic ¿shuttling¿ reaction to merely 3.7s under most conditions. Additionally, an alternative switching mechanism is proposed based on the new theoretical findings. With the successful deciphering of the information hidden behind the GIXD and the lucrative enhancement in physical understanding of the [2]rotaxane molecule using first principles calculations, further effort is invested in exploiting this computational technique to predict candidate molecules that display desirable functionalities. Several halogenated acene molecules are expected to pack in the face-to-face motif, in contrast to the commonly observed herringbone packing motif. This is believed to enhance the mobility. Synthesis of these candidate molecules is underway to allow experimental verification, with the goal of dramatically improving device performance to fully exploit the idealized electrostatics of these structures.

Advisors: Vivek Subramanian

---

BibTeX citation:

@phdthesis{Phoa:EECS-2008-66,
    Author= {Phoa, Kin-Yip and Subramanian, Vivek},
    Title= {Nanoscale organic electronics: Experimental and theoretical studies on alkyl thiophene and rotaxane},
    School= {EECS Department, University of California, Berkeley},
    Year= {2008},
    Month= {May},
    Url= {http://www2.eecs.berkeley.edu/Pubs/TechRpts/2008/EECS-2008-66.html},
    Number= {UCB/EECS-2008-66},
    Abstract= {As the end of the International Technology Roadmap for Semiconductors (ITRS) is approaching, supplements to the existing silicon technology are sought.  Molecular electronics presents itself as one of the most promising candidates in terms of projected device dimensions.  This thesis is devoted to advance the current technology towards the ultimate paradigm of single molecule transistors.
Firstly, we demonstrate field effect transistors with complete FET functionality formed within a self-assembled monolayer integrating both dielectric and semiconductor functionality within the same molecule.   This is an attractive structure due to the potentially idealized characteristics that are achievable due to the intra-molecular semiconductor-dielectric interface.  Grazing incidence X-ray diffraction (GIXD) is used to further study the morphology and the crystallinity of the monolayer deposited on different substrates.  Furthermore, first-principle calculations are employed to provide additional physical understanding of this system, as well as to model the monolayer.  Initial demonstration of dielectric-integrated monolayer FETs is achieved based on the proposed monolayer system, albeit with poor characteristics.

Moreover, to complete the picture of nanoscale organic electronics, we investigate the feasibility of the [2]rotaxane molecular memory reported by Heath and Stoddart in 2002.  In particular, its switching performance is probed theoretically through the evaluation and estimation of the energy landscape, the ionization potentials and the dielectric constants.  However, it is found that the switching time of this molecule is greatly limited by an intrinsic ¿shuttling¿ reaction to merely 3.7s under most conditions.  Additionally, an alternative switching mechanism is proposed based on the new theoretical findings.
With the successful deciphering of the information hidden behind the GIXD and the lucrative enhancement in physical understanding of the [2]rotaxane molecule using first principles calculations, further effort is invested in exploiting this computational technique to predict candidate molecules that display desirable functionalities.  Several halogenated acene molecules are expected to pack in the face-to-face motif, in contrast to the commonly observed herringbone packing motif.  This is believed to enhance the mobility.  Synthesis of these candidate molecules is underway to allow experimental verification, with the goal of dramatically improving device performance to fully exploit the idealized electrostatics of these structures.},
}

EndNote citation:

%0 Thesis
%A Phoa, Kin-Yip 
%A Subramanian, Vivek 
%T Nanoscale organic electronics: Experimental and theoretical studies on alkyl thiophene and rotaxane
%I EECS Department, University of California, Berkeley
%D 2008
%8 May 21
%@ UCB/EECS-2008-66
%U http://www2.eecs.berkeley.edu/Pubs/TechRpts/2008/EECS-2008-66.html
%F Phoa:EECS-2008-66