Multiscale Analysis of Phase Transformations in Self-Assembled Layers of 4,4 '-Biphenyl Dicarboxylic Acid on the Ag(001) Surface

Multiscale Analysis of Phase Transformations in Self-Assembled Layers of 4,4 '-Biphenyl Dicarboxylic Acid on the Ag(001) Surface

WoS Article

Understanding the nucleation and growth kinetics of thin films is a prerequisite for their large-scale utilization in devices. For self-assembled molecular phases near thermodynamic equilibrium the nucleation-growth kinetic models are still not developed. Here, we employ real-time low-energy electron microscopy (LEEM) to visualize a phase transformation induced by the carboxylation of 4,4'-biphenyl dicarboxylic acid on Ag(001) under ultra-high-vacuum conditions. The initial (alpha) and transformed (beta) molecular phases are characterized in detail by X-ray photoemission spectroscopy, single-domain low-energy electron diffraction, roomtemperature scanning tunneling microscopy, noncontact atomic force microscopy, and density functional theory calculations. The phase transformation is shown to exhibit a rich variety of phenomena, including Ostwald ripening of the a domains, burst nucleation of the beta domains outside the alpha phase, remote dissolution of the alpha domains by nearby beta domains, and a structural change from disorder to order. We show that all phenomena are well described by a general growth-conversion-growth (GCG) model. Here, the two-dimensional gas of admolecules has a dual role: it mediates mass transport between the molecular islands and hosts a slow deprotonation reaction. Further, we conclude that burst nucleation is consistent with a combination of rather weak intermolecular bonding and the onset of an additional weak many-body attractive interaction when a molecule is surrounded by its nearest neighbors. In addition, we conclude that Ostwald ripening and remote dissolution are essentially the same phenomenon, where a more stable structure grows at the expense of a kinetically formed, less stable entity via transport through the 2D gas. The proposed GCG model is validated through kinetic Monte Carlo (kMC) simulations.

Understanding the nucleation and growth kinetics of thin films is a prerequisite for their large-scale utilization in devices. For self-assembled molecular phases near thermodynamic equilibrium the nucleation-growth kinetic models are still not developed. Here, we employ real-time low-energy electron microscopy (LEEM) to visualize a phase transformation induced by the carboxylation of 4,4'-biphenyl dicarboxylic acid on Ag(001) under ultra-high-vacuum conditions. The initial (alpha) and transformed (beta) molecular phases are characterized in detail by X-ray photoemission spectroscopy, single-domain low-energy electron diffraction, roomtemperature scanning tunneling microscopy, noncontact atomic force microscopy, and density functional theory calculations. The phase transformation is shown to exhibit a rich variety of phenomena, including Ostwald ripening of the a domains, burst nucleation of the beta domains outside the alpha phase, remote dissolution of the alpha domains by nearby beta domains, and a structural change from disorder to order. We show that all phenomena are well described by a general growth-conversion-growth (GCG) model. Here, the two-dimensional gas of admolecules has a dual role: it mediates mass transport between the molecular islands and hosts a slow deprotonation reaction. Further, we conclude that burst nucleation is consistent with a combination of rather weak intermolecular bonding and the onset of an additional weak many-body attractive interaction when a molecule is surrounded by its nearest neighbors. In addition, we conclude that Ostwald ripening and remote dissolution are essentially the same phenomenon, where a more stable structure grows at the expense of a kinetically formed, less stable entity via transport through the 2D gas. The proposed GCG model is validated through kinetic Monte Carlo (kMC) simulations.

self-assembly; low-energy electron microscopy; scanning probe microscopy; kinetic Monte Carlo; phase transformation; surfaces

self-assembly; low-energy electron microscopy; scanning probe microscopy; kinetic Monte Carlo; phase transformation; surfaces

PROCHÁZKA, P.; GOSALVEZ, M.; KORMOŠ, L.; DE LA TORRE, B.; GALLARDO, A.; ALBERDI-RODRIGUEZ, J.; CHUTORA, T.; MAKOVEEV, A.; SHAHSAVAR, A.; ARNAU, A.; JELÍNEK, P.; ČECHAL, J.

2021

23.06.2020

AMER CHEMICAL SOC

WASHINGTON

1936-0851

ACS Nano

14

6

United States of America

7269

7279

11

https://pubs.acs.org/doi/10.1021/acsnano.0c02491