  Computational methods are fast becoming an integral part of nanoelectronics
design process. With increasing computational power, electron transport
simulation methods such as Non-equilibrium Greens function (NEGF) methods now
hold promise in study and design of new electronic devices. Single molecule
circuits as optimized device size covers a significant electron transmission,
which originated of intrinsic molecular properties. In this study, we study and
design a single molecule switch based on a transition metal dichalcogenide
(TMD) electrode (molybdenum disulphide (MoS2)) and a photochromic molecule. The
chosen molecule, Diarylethene, is one of the only few thermally irreversible
photochromes. The 1T phase of TMD monolayer has metallic properties and can act
as a conducting electrode for these molecular switches. Further, the 1T phase
can be functionalized using thiol chemistry, which leads to the formation of
covalent C-S bonds that enable further addition of functional photochromic
groups to the TMD surface. In this report, we compare and contrast different
chemistry and spacer groups with respect to their response as a molecular
switch, focusing on the ON/OFF transmission ratio at the Fermi level. We
identify chemistries for further experimentation. If experimentally realized,
these switches are expected to become integral part of various applications
including molecular memories, photon detectors and logic devices.
