Work-function modification of PEG(thiol) adsorbed on the Au(111) surface: A first-principles study

Abstract

The possibility of modifying the work function of electrodes is important for optimizing the energy barriers for charge-injection (extraction) at the interface to an organic material. In this study, we perform density-functional-theory calculations to investigate the impact of dithiol-terminated polyethylene glycol (PEG(thiol)) based self-assembled monolayers (SAMs) with different numbers of PEG repeat units on the work function of the Au(111) surface. We find that a monolayer of PEG(thiol) decreases the work function of the Au(111) surface, where the magnitude of this reduction strongly depends on the length of the PEG backbone. The main contribution arises from the dipole due to the adsorption-induced charge rearrangement at the interface. Our work reveals a pronounced odd-even effect, which can be traced back to the dipole moment of the PEG(thiol) layer.

Disordered Mixture of Self-Assembled Molecular Functional Groups on Heterointerfaces with p-Si Leads to Multiple Key Generation in Physical Unclonable Functions

“…Self-assembled monolayers (SAMs) offer an easy-to-fabricate and low-cost process owing to their molecular assembly. , SAMs consist of a hydroxyl molecular “head group,” enabling self-assembled covalent bond formation with a target surface. , Furthermore, SAMs provide various functional groups in their molecular tail group. Depending on the functional groups, such as amine (−NH 2 ), methyl (−CH 3 ), , fluoromethyl (−CF 3 ), carboxyl (−COOH), , and thiol (−SH), , the dipole polarity or surface energy property can be controlled. , SAMs allow solution processing, which reduces the complexity of the fabrication process. , Despite these merits of SAMs, the use of SAMs as PUFs has not been attempted.…”

“…31,32 Furthermore, SAMs provide various functional groups in their molecular tail group. Depending on the functional groups, such as amine (−NH 2 ), 33 methyl (−CH 3 ), 34,35 fluoromethyl (−CF 3 ), 36 carboxyl (−COOH), 37,38 and thiol (−SH), 39,40 the dipole polarity or surface energy property can be controlled. 41,42 SAMs allow solution processing, which reduces the complexity of the fabrication process.…”