Scanning Tunneling Microscopy (STM) Study on Morphology of Regioregular Poly(3-alkylthiophene) Deposited on A(111) Surface

Abstract

We find a nonsupersymmetric dilatonic deformation of AdS 5 geometry as an exact nonsingular solution of the type-IIB supergravity. The dual gauge theory has a different Yang-Mills coupling in each of the two halves of the boundary spacetime divided by a codimension one defect. We discuss the geometry of our solution in detail, emphasizing the structure of the boundary, and also study the string configurations corresponding to Wilson loops. We also show that the background is stable under small scalar perturbations.

Two-Dimensional Supramolecular Organization in Oligomers of Dialkylterthiophenes—Effect of the Alkyl Substituent Position

“…It has been used for more than a decade for precise characterization of thiophene-containing oligomer and polymer monomolecular layers at a molecular resolution. [17][18][19][20] The molecular arrangement of various linear thiophene derivatives [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] and, more recently, also derivatives more complex in shape [33][34][35][36][37][38] has been investigated. In general, on substrates that interact weakly with thiophene units (for example, HOPG), highly ordered molecular adlayers were found.…”

“…As a result, the adlayers reveal a more disordered structure. 19,[30][31][32] STM investigations unequivocally indicate that the use of weakly interacting substrates together with appropriately designed molecules (macromolecules) can lead to the formation of a supramolecular aggregation with a controlled structure. Of course, this is of crucial importance for any application of these compounds in organic or molecular electronics.…”

“…STM is especially well suited for this type of investigation. It has been used for more than a decade for precise characterization of thiophene-containing oligomer and polymer monomolecular layers at a molecular resolution. − The molecular arrangement of various linear thiophene derivatives − and, more recently, also derivatives more complex in shape − has been investigated. In general, on substrates that interact weakly with thiophene units (for example, HOPG), highly ordered molecular adlayers were found. ,,− ,− These supramolecular aggregations, formed spontaneously for alkylthiophene derivatives, are usually stabilized and controlled via multiple van der Waals interactions of alkyl side groups, separating planes of π-stacked molecular backbones.…”

“…This is typical behavior also for alkyl derivatives of various organic molecules, for example, pyridine and annulene. , In the case of substrates, such as gold, that interact strongly with these molecules, a pronounced influence of the substrate on their supramolecular organization is observed, as expected. As a result, the adlayers reveal a more disordered structure. ,− …”