Organic—Inorganic Molecular Beam Epitaxy

Charge Transfer Exciton and Spin Flipping at Organic–Transition-Metal Dichalcogenide Interfaces

“…This lattice spacing agrees with previous STM studies of metal− phthalocyanine on MoS 2 . 35 The result shows that ZnPc molecules have a face-on orientation with respect to the MoS 2 surface. The ionization potential (IP) of thicker ZnPc thin films determined from the ultraviolet photoemission spectroscopy (UPS) is 5.14 eV (Supporting Information), which is consistent with the reported IP of lying-down metal− phthalocyanine molecules.…”

“…The sample was then transferred in situ to another UHV chamber with a base pressure of 8 × 10 −10 Torr, where the ZnPc deposition was done. For thicknesses less than 4 nm, the ZnPc molecules were deposited at a rate of 0.3 Å/min and a sample temperature of 90 °C to ensure a well-ordered film was formed (similar to the procedure reported in ref 35). For thicknesses beyond 4 nm, the growth rate was increased to 0.7 Å/min and the sample was kept at room temperature.…”

Organic-2D Material Heterostructures: A Promising Platform for Exciton Condensation and Multiplication

“…The results presented here are based on a ZnPc molecule adsorbed in a 5 3 3 × supercell of MoS 2 with the most favorable binding site, which is determined from calculations for an experimental geometry of six ZnPc molecules adsorbed in a 13 5 3 × supercell of MoS 2 . 19 (see SI Section S1 and Figure S1). The GW-BSE results for an alternative binding site are very similar (see SI).…”

“…Despite the narrow bandwidth (∼2.2 meV) of the ZnPc HOMO, this effective mass is still reasonably small (SI Section S7). We have also computed the effective mass for alternative geometries, including the experimentally observed, 19 large geometry of six ZnPc molecules adsorbed in a 13 5 3 × supercell of MoS 2 (Sections S8 and S9 of the SI). We estimate the excitonic mass of CT0 to be ∼10−20 m 0 in these geometric configurations.…”

“…On the other hand, due to the relatively nondispersive molecular HOMO or LUMO levels, the lowest energy CTEs in organic-2D material heterostructures are generally direct in momentum space and do not suffer from the decoherence 7,8 related to large exciton momenta in misaligned 2D TMD heterostructures. Organics such as stable phthalocyanine molecules can readily form ordered monolayers on TMDs, 19,40,41 thus providing clean interfaces for the formation of the exciton condensates. The existence of a large number of stable and even magnetic phthalocyanine molecules also provides tunability for the resulting condensate properties.…”