Mohammad Nasiri fard - Department of Physics, Imam Khomeini International University, Qazvin ۳۴۱۴۸۹۶۸۱۸, Iran.
Somaieh Ahmadi - Department of Physics, Imam Khomeini International University, Qazvin ۳۴۱۴۸۹۶۸۱۸, Iran
leila eslami - Plasma Physics Research Center, Science and Research Branch, Islamic Azad University

Polythiophene is a highly conductive molecule which possesses thermal and chemical stability showing great performance in electrical devices. Polythiophene also shows an uncommon highly demanding electrical property named negative differential resistance which is a decrease of electron current with increase of applied voltage. To address this issue, in this work we study theoretically electron transport properties of a polythiophene molecular bridge sandwiched between two metal leads in the presence of Nitrogen atom as a substitute for one or two of the Carbon atoms in the molecule. The results based on Green’s function formalism show that the presence of Nitrogen reduces the electron transmission coefficient. On the other hand, Nitrogen can lead to amplification of negative differential resistance. Strength of the resistance is affected by the positions and number of Nitrogen atoms in the system. Therefore, choosing right positions for locating impurities is very important. We found that by substituting a Carbon atom with Nitrogen in some positions the system shows notable negative differential resistance. Besides, when two Carbon atoms are replaced by Nitrogen atoms there are some special locations that not only the system shows negative deferential resistance but also it works as an electronic molecular switch which is highly demanding in electronic industry.

Green’s function method, Molecular device, Negative differential resistance, Polythiophene