Pentacene multilayers on Ag(111) surface

TL;DR

This study uses density functional theory to investigate the growth, structure, and electronic properties of pentacene multilayers on Ag(111), revealing preferred adsorption modes and bulk-like growth patterns.

Contribution

First-principles calculations elucidate the initial growth modes and structural preferences of pentacene multilayers on Ag(111), highlighting bulk-like assembly tendencies.

Findings

Pentacene prefers a planar, aligned configuration on Ag(111) at 3.9 Å.

Second layer molecules become skewed, favoring a bulk-like tilting arrangement.

Growth pattern indicates bulk-like stacking with a planar first layer.

Abstract

The structural profiles and electronic properties of pentacene (C$_{22}$H$_{14}$) multilayers on Ag(111) surface has been studied within the density functional theory (DFT) framework. We have performed first-principle total energy calculations based on the projector augmented wave (PAW) method to investigate the initial growth patterns of pentacene (Pn) on Ag(111) surface. In its bulk phase, pentacene crystallizes with a triclinic symmetry while a thin film phase having an orthorhombic unit cell is energetically less favorable by 0.12 eV/cell. Pentacene prefers to stay planar on Ag(111) surface and aligns perfectly along silver rows without any molecular deformation at a height of 3.9 {\AA}. At one monolayer (ML) coverage the separation between the molecular layer and the surface plane extends to 4.1 {\AA} due to intermolecular interactions weakening surface--pentacene attraction. While the first ML remains flat, the molecules on a second full pentacene layer deposited on the surface rearrange so that they become skewed with respect to each other. This adsorption mode is energetically more preferable than the one for which the molecules form a flat pentacene layer by an energy difference similar to that obtained for bulk and thin film phases. Moreover, as new layers added, pentacenes assemble to maintain this tilting for 3 and 4 ML similar to its bulk phase while the contact layer always remains planar. Therefore, our calculations indicate bulk-like initial stages for the growth pattern.