Atomic Force Microscopy and X-ray Studies of Three-Dimensional Islands on Monolayers

Abstract

The structure and morphology of the three-dimensional aggregates of arachidic acid were studied by atomic force microscopy (AFM) after transfer onto a silicon wafer and by synchrotron grazing incidence X-ray diffraction (GID) at the helium/water interface. The 3D aggregates on the wafer observed by AFM are islands of granulelike and platelike shapes. The plate islands consist of terraces of different heights. The crystal structure of the plate islands was determined through molecular resolution by AFM. They have the C-crystal structure of arachidic acid at the beginning of the relaxation. During further relaxation the B-crystal structure becomes apparent. The islands with B-crystal structure dominate at the end of the relaxation process. Regions with a disordered molecular structure are found beside the ordered crystal structures. In all ordered regions of a single island the same crystal structure is observed. Using GID, the B-and C-crystal structures of the 3D aggregates of arachidic acid were also found at the helium/water interface. No peaks of any crystal structure are observed until 20% of the monolayer material is transformed into 3D aggregates. Then first the peaks of the B-crystal structure appear, which increase with the relaxation time. Additionally small peaks corresponding to the C-crystal structure are found.

Growth of Preformed 3D Nuclei in Langmuir Monolayers below Critical Supersaturation

“…In the meantime, using highly sensitive techniques, numerous direct experiments on the texture of the 3D aggregates and their lattice structure have provided additional support for the concept of the 2D−3D transition during the relaxation kinetics. At different stages of the relaxation process, the morphology of the overgrown 3D aggregates has been visualized on a submicroscopic scale by AFM , and on a microscopic scale by Brewster angle microscopy (BAM). , The combination of X-ray reflectometry and AFM , provides further information on the structural features and transformations of the 3D aggregates.…”

“…At different stages of the relaxation process, the morphology of the overgrown 3D aggregates has been visualized on a submicroscopic scale by AFM 14,15 and on a microscopic scale by Brewster angle microscopy (BAM). 16,17 The combination of X-ray reflectometry and AFM 18,19 provides further information on the structural features and transformations of the 3D aggregates.…”

Self-assembly of metastable langmuir monolayers on planar solid surfaces

“…One has take into account that the surface pressure corresponding to the onset of the monolayer fracturing and the nucleation of separate regions of the three dimensional phase typically appears to be lower (sometimes, essentially) than the "macroscopic" col lapse pressure determined experimentally [14,24,47]. The morphology of collapsing monolayers is stud ied by methods that are used to investigate the two dimensional phase transitions, i.e., the Brewster angle microscopy [49][50][51], X ray diffraction [52,53], polar ization fluorescent microscopy [47,54], and atomic force and transmission or scanning electron micros copy [55][56][57] (for one layer LBfilms). These methods are traditionally combined with the measurements of pressure relaxation at a constant surface area (isother mal relaxation [54]) or area relaxation at a constant surface pressure (isobaric relaxation [58]).…”

Nanoparticles Change the Ordering Pattern of n-Carboxylic Acids into Nanorods on HOPG

“…40 The main difference between the B-and C-form is that in the B-form the unit cell dimension along the a-axis is expanded due to a rotation along the b-axis, while in the C-form, the unit cell dimension along the b-axis is expanded due to a tilt over the a-axis. 41 While both B-and C-forms can be obtained by fast crystallization, kinetics 42 and the solvent ethanol both favor the C-form. 43 We therefore use the C-form crystal structure to interpret the AFM topographical measurement results.…”