Etching of Crystalline ZnO Surfaces upon Phosphonic Acid Adsorption: Guidelines for the Realization of Well-Engineered Functional Self-Assembled Monolayers

Journal article


Publication Details

Author(s): Ostapenko A, Klöffel T, Eussner J, Harms K, Dehnen S, Meyer B, Witte G
Journal: ACS Applied Materials and Interfaces
Publication year: 2016
Volume: 8
Journal issue: 21
Pages range: 13472-13483
ISSN: 1944-8244
eISSN: 1944-8252


Abstract

Functionalization of metal oxides by means of covalently bound self-assembled monolayers (SAMs) offers a tailoring of surface electronic properties such as their work function and, in combination with its large charge carrier mobility, renders ZnO a promising conductive oxide for use as transparent electrode material in optoelectronic devices. In this study, we show that the formation of phosphonic acid-anchored SAMs on ZnO competes with an unwanted chemical side reaction, leading to the formation of surface precipitates and severe surface damage at prolonged immersion times of several days. Combining atomic force microscopy (AFM), X-ray diffraction (XRD), and thermal desorption spectroscopy (TDS), the stability and structure of the aggregates formed upon immersion of ZnO single crystal surfaces of different orientations [(0001̅), (0001), and (101̅0)] in phenylphosphonic acid (PPA) solution were studied. By intentionally increasing the immersion time to more than 1 week, large crystalline precipitates are formed, which are identified as zinc phosphonate. Moreover, the energetics and the reaction pathway of this transformation have been evaluated using density functional theory (DFT), showing that zinc phosphonate is thermodynamically more favorable than phosphonic acid SAMs on ZnO. Precipitation is also found for phosphonic acids with fluorinated aromatic backbones, while less precipitation occurs upon formation of SAMs with phenylphosphinic anchoring units. By contrast, no precipitates are formed when PPA monolayer films are prepared by sublimation under vacuum conditions, yielding smooth surfaces without noticeable etching.


FAU Authors / FAU Editors

Klöffel, Tobias
Interdisziplinäres Zentrum für Molekulare Materialien
Meyer, Bernd Prof. Dr.
Professur für Computational Chemistry


Additional Organisation
Exzellenz-Cluster Engineering of Advanced Materials


External institutions with authors

Philipps-Universität Marburg


Research Fields

A3 Multiscale Modeling and Simulation
Exzellenz-Cluster Engineering of Advanced Materials


How to cite

APA:
Ostapenko, A., Klöffel, T., Eussner, J., Harms, K., Dehnen, S., Meyer, B., & Witte, G. (2016). Etching of Crystalline ZnO Surfaces upon Phosphonic Acid Adsorption: Guidelines for the Realization of Well-Engineered Functional Self-Assembled Monolayers. ACS Applied Materials and Interfaces, 8(21), 13472-13483. https://dx.doi.org/10.1021/acsami.6b02190

MLA:
Ostapenko, Alexandra, et al. "Etching of Crystalline ZnO Surfaces upon Phosphonic Acid Adsorption: Guidelines for the Realization of Well-Engineered Functional Self-Assembled Monolayers." ACS Applied Materials and Interfaces 8.21 (2016): 13472-13483.

BibTeX: 

Last updated on 2019-15-05 at 10:34