The ever-decreasing size of transistors has reached a stage where leakage current has become a significant challenge to overcome. A great deal of work has gone into searching for molecular dielectric materials, which possess high dielectric constants yet low electronic transmission. This study takes a theoretical approach to design molecular dielectric materials based on monolayer-like structures. To serve the dual-requirement for dielectric materials, a “back-bone” structure of twisted biphenyl has been carefully chosen, as it both breaks conjugation and exhibits destructive quantum interference, thus limiting the electronic transmission through the system. Different substituents were investigated, with the aim of increasing the polarizability of the molecule, thence increasing the dielectric constant. Beside functioning as a way to fine-tune the dielectric constants, the substituted groups serves as “anchors” locking the benzene rings with a roughly 90 degree angle. The dielectric constants are observed to be unaffected by the twist in the structure. In contrast, it was found that by choosing optimal substituents, the dielectric constant could be increased. For a few selected molecules, with the most promising dielectric constants, transmission calculations were carried out to assure that the structures still function as molecular insulators. In all, a “back-bone” is presented, which possess the opportunity to optimize the dielectric constant while hindering electronic transmission through the system.

Exploiting quantum interference effects for designing new dielectric materials

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