TY - JOUR

T1 - Growth morphologies of dihydro-tetraaza-acenes on c-plane sapphire

T2 - Englisch

AU - Matkovic, Aleksandar

AU - Cicek, Aydan

AU - Kratzer, Markus

AU - Kaufmann, Benjamin

AU - Thomas, Anthony

AU - Chen, Zhongrui

AU - Siri, Olivier

AU - Becker, Conrad

AU - Teichert, Christian

PY - 2018

Y1 - 2018

N2 - Dihydro-tetraaza-acenes are promising candidates for future applications in organic electronics, since these molecules form crystals through an interplay between H-bonding, dipolar, and van der Waals interactions. As a result, densely packed π−π structures – favorable for charge transport – are obtained, with exceptional stability under ambient conditions. This study investigates growth morphologies of dihydro-tetraaza-pentacene and dihydro-tetraaza-heptacene on vicinal c-plane sapphire. Submonolayers and thin films are grown using hot wall epitaxy, and the structures are investigated ex-situ by atomic force microscopy. Molecular arrangement, nucleation densities, sizes, shapes, and stability of the crystallites are analyzed as a function of the substrate temperature. The two molecular species were found to assume a different orientation of the molecules with respect to the substrate. An activation energy of (1.23 ± 0.12) eV was found for the nucleation of dihydro-tetraaza-heptacene islands (composed of upright standing molecules), while (1.16 ± 0.25) eV was obtained for dihydro-tetraaza-pentacene needles (composed of lying molecules). The observed disparity in the temperature dependent nucleation densities of the two molecular species is attributed to the different thermalization pathways of the impinging molecules.

AB - Dihydro-tetraaza-acenes are promising candidates for future applications in organic electronics, since these molecules form crystals through an interplay between H-bonding, dipolar, and van der Waals interactions. As a result, densely packed π−π structures – favorable for charge transport – are obtained, with exceptional stability under ambient conditions. This study investigates growth morphologies of dihydro-tetraaza-pentacene and dihydro-tetraaza-heptacene on vicinal c-plane sapphire. Submonolayers and thin films are grown using hot wall epitaxy, and the structures are investigated ex-situ by atomic force microscopy. Molecular arrangement, nucleation densities, sizes, shapes, and stability of the crystallites are analyzed as a function of the substrate temperature. The two molecular species were found to assume a different orientation of the molecules with respect to the substrate. An activation energy of (1.23 ± 0.12) eV was found for the nucleation of dihydro-tetraaza-heptacene islands (composed of upright standing molecules), while (1.16 ± 0.25) eV was obtained for dihydro-tetraaza-pentacene needles (composed of lying molecules). The observed disparity in the temperature dependent nucleation densities of the two molecular species is attributed to the different thermalization pathways of the impinging molecules.

KW - AFM

KW - DHTAP

KW - Dihydro-tetraaza-acenes

KW - H-bonding

KW - Oligoacene derivates

KW - Organic thin films

UR - http://www.scopus.com/inward/record.url?scp=85044281678&partnerID=8YFLogxK

U2 - 10.1016/j.susc.2018.03.009

DO - 10.1016/j.susc.2018.03.009

M3 - Article

AN - SCOPUS:85044281678

VL - 678.2018

SP - 128

EP - 135

JO - Surface Science

JF - Surface Science

SN - 0039-6028

IS - December

ER -