Molecular Electronic Junctions Achieved High Thermal Switch Ratios in Atomistic Simulations

XF Wei and R Hernandez, ACS APPLIED MATERIALS & INTERFACES, 16, 48103-48112 (2024).

DOI: 10.1021/acsami.4c09904

The development of devices that improve thermal energy management requires thermal regulation with efficiency comparable to the ratios R similar to 10(5) in electric regulation. Unfortunately, current materials and devices in thermal regulators have only been reported to achieve R similar to 10. We use atomistic simulations to demonstrate that Ferrocenyl (Fc) molecules under applied external electric fields can alter charge states and achieve high thermal switch ratios R = G(q)/G(0), where G(q) and G(0) are the high and low limiting conductances. When an electric field is applied, Fc molecules are positively charged, and the SAM-Au interfacial interaction is strong, leading to high heat conductance G(q). On the other hand, with no electric field, the Fc molecules are charge neutral and the SAM-Au interfacial interaction is weak, leading to low heat conductance G(0). We optimized various design parameters for the device performance, including the Au-to-Au gap distance L, the system operation temperature T, the net charge on Fc molecules q, the Au surface charge number Z, and the SAM number N. We find that G(q) can be very large and increases with increasing q, Z, or N, while G(0) is near 0 at L > 3.0 nm. As a result, R > 100 was achieved for selected parameter ranges reported here.

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