Ehrlich-Schwoebel Barriers and Island Nucleation in Organic Thin-Film Growth

Teichert, Christian; Hlawacek, Gregor; Winkler, Adolf; Puschnig, Peter; Ambrosch‐Draxl, Claudia

doi:10.1007/978-3-642-33848-9_4

Cited by 6 publications

(8 citation statements)

References 58 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Therefore, the observed deviations of the molecular arrangement from the ideal herringbone structure are most probably caused, besides the stepped substrate itself, by the larger molecular tilting, which is twice as large as in the 6P crystal bulk. This could also explain why the molecular structure is much more regular in one direction since the same tilting direction/azimuth of the molecular long axis within one island was pointed out in the literature …”

Section: Resultssupporting

confidence: 86%

See 1 more Smart Citation

Initial Stage of para-Hexaphenyl Thin-Film Growth Controlled by the Step Structure of the Ion-Beam-Modified TiO₂(110) Surface

et al. 2019

View full text Add to dashboard Cite

Organic electronics require a precise control over properties of a molecule–substrate interface as well as film growth morphology, from both fundamental points of view, when a clean vacuum environment is needed and also under ambient air conditions. In this paper, we present submonolayer molecular films of para-hexaphenyl (6P) formation on the rutile TiO2(110) substrates and ways of affecting the growth and morphology via ion-beam nanopatterning. Ultrahigh vacuum deposition and measurements are followed by the film evolution study upon air exposure. Strongly anisotropic TiO2(110) surfaces, in the form of terraced ripples with a preserved (1 × 1) structure, were controllably fabricated utilizing ion-beam bombardment and characterized by means of high-resolution scanning tunneling microscopy and low-energy electron diffraction. 6P thin films were prepared using organic molecular beam epitaxy and characterized in situ by noncontact atomic force microscopy. Ex situ characterization was performed by tapping-mode atomic force microscopy, scanning electron microscopy, and noncontact atomic force microscopy with molecular resolution. We have demonstrated that by changing the size of locally preserved (1 × 1) surface areas, determined by the ripple parameters, different 6P assemblies can be promoted. With the shrinking size of the uninterrupted (1 × 1) terminated areas, 6P changes its growth morphology from needlelike to islandlike accompanied by a reorientation of the molecules from flat-lying to upright-standing. The resulting morphology depends on the structure of a two-dimensional phase of lying molecules formed at the initial stage of deposition, which can be either a well-ordered wetting layer or a two-dimensional mobile lattice gas. The postgrowth remainders of these two-dimensional phases participate in additional nucleation processes forming small islands or clusters.

show abstract

Section: Resultssupporting

confidence: 86%

“…This could also explain why the molecular structure is much more regular in one direction since the same tilting direction/azimuth of the molecular long axis within one island was pointed out in the literature. 71…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Initial Stage of para-Hexaphenyl Thin-Film Growth Controlled by the Step Structure of the Ion-Beam-Modified TiO₂(110) Surface

et al. 2019

View full text Add to dashboard Cite

show abstract

“…A level dependent ESB (e.g. as described above and in [76,135]) often goes hand in hand with a change in tilt angle of the molecular backbone. However, the proposed Fosbury Flop-like step edge crossing can not explain the experimentally observed step edge barrier reduction.…”

Section: Mound Formationmentioning

confidence: 99%

Nucleation and growth of thin films of rod-like conjugated molecules

Hlawacek

Teichert

2013

J. Phys.: Condens. Matter

Self Cite

107

View full text Add to dashboard Cite

Abstract. Thin films formed from small molecules rapidly gain importance in different technological fields. To explain their growth, methods developed for zero-dimensional atoms as the film forming particles are applied. However, in organic thin film growth the dimensionality of the building blocks comes into play. Using the special case of the model molecule para-Sexiphenyl, we will emphasize the challenges that arise from the anisotropic and one-dimensional nature of building blocks. Differences or common features with other rodlike molecules will be discussed. The typical morphologies encountered for this group of molecules and the relevant growth modes will be investigated. Special attention is given to the transition between flat lying and upright orientation of the building blocks during nucleation. We will further discuss methods to control the molecular orientation and describe the involved diffusion processes qualitatively and quantitatively.

show abstract

“…The field of organic electronics has attracted large attention during the last decades because of its promising perspective for the fabrication of flexible thin-film devices. − Compared with covalently bound inorganic semiconductors, organic semiconductors (OSCs) are only weakly bound, which results in small sublimation enthalpies and low barriers for diffusion processes, , hence making the preparation of ordered (possibly crystalline) thin films and heterostructures challenging. , Owing to the shape anisotropy of the molecular entities, the optoelectronic properties of OSC solids are also rather anisotropic and further depend on the molecular and crystalline orientation , as well as on the adopted packing motifs (e.g., polymorphs), − which adds another complexity to the task of producing ordered OSC films for optoelectronic applications. OSC films on metal or insulator substrates often grow in a Stranski–Krastanov mode and exhibit a notable dewetting and island formation which originates from the structural mismatch between the first monolayer (i.e., wetting layer) and the OSC bulk crystal structure. , In addition, many OSCs exhibit a kinetic roughening upon thin-film deposition, which is attributed to the Ehrlich–Schwöbel barriers at terrace edges or grain boundaries, − and aggravates the preparation of smooth OSC films. Such growth instabilities are critical issues because discontinuity and defect-induced trap states significantly reduce the resulting charge carrier mobility in organic thin-film devices. , Besides such device requirements, the fabrication of smooth and crystalline films of homogeneous thickness is also of great interest for more fundamental studies such as time-resolved studies of photoexcitations in OSC films because it enables to obtain thickness-dependent transfer dynamics toward metallic electrodes. , …”

Section: Introductionmentioning

confidence: 99%

Titanylphthalocyanine Films on Ag(111): An Epitaxial Metal/Organic Heterosystem with an Exceptional Smooth Surface

2019

View full text Add to dashboard Cite

The fabrication of smooth organic semiconductor films with homogeneous thickness is of key importance for the improvement of organic electronic devices and realization of well-defined molecular heterostructures. Although many π-conjugated molecular materials form highly ordered monolayers on (single) crystalline metal substrates, further deposition typically obeys a Stranski–Krastanov growth and results in considerable layer roughness. Here, we examine the evolution of titanylphthalocyanine (TiOPc) films on Ag(111) for thicknesses ranging from an initial seed layer to thick multilayers (200 nm) by combining scanning probe microscopy [scanning tunneling microscopy (STM) and atomic force microscopy (AFM)] with X-ray diffraction and synchrotron-based photoelectron spectroscopy [X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption spectroscopy (NEXAFS)]. While the crystallinity of the TiOPc films increases with substrate temperature during growth, even at temperatures close to the onset of desorption, extended and molecularly flat islands are formed, which cover more than 80% of the substrate area resulting in exceptional smooth layers. The crystalline TiOPc films exclusively exhibit the phase I polymorph where molecular planes are oriented nearly parallel to the substrate surface and adopt an alternating (up/down) stacking of their titanyl groups forming stable bilayer units. Similar to the first bilayer, TiOPc multilayers are also epitaxially aligned with respect to the substrate. STM and AFM data further show that the macroscopic film roughness is essentially due to rotational domain boundaries in the seed layer which are not overgrown and result in characteristic macroscopic trenches. The high crystalline ordering and exceptional smoothness make this metal/organic heterosystem particularly suitable as a molecular spacer layer and allows for thickness-dependent studies of optoelectronic excitations and their dynamics.

show abstract

Ehrlich-Schwoebel Barriers and Island Nucleation in Organic Thin-Film Growth

Cited by 6 publications

References 58 publications

Initial Stage of para-Hexaphenyl Thin-Film Growth Controlled by the Step Structure of the Ion-Beam-Modified TiO₂(110) Surface

Initial Stage of para-Hexaphenyl Thin-Film Growth Controlled by the Step Structure of the Ion-Beam-Modified TiO₂(110) Surface

Nucleation and growth of thin films of rod-like conjugated molecules

Titanylphthalocyanine Films on Ag(111): An Epitaxial Metal/Organic Heterosystem with an Exceptional Smooth Surface

Contact Info

Product

Resources

About

Ehrlich-Schwoebel Barriers and Island Nucleation in Organic Thin-Film Growth

Cited by 6 publications

References 58 publications

Initial Stage of para-Hexaphenyl Thin-Film Growth Controlled by the Step Structure of the Ion-Beam-Modified TiO2(110) Surface

Initial Stage of para-Hexaphenyl Thin-Film Growth Controlled by the Step Structure of the Ion-Beam-Modified TiO2(110) Surface

Nucleation and growth of thin films of rod-like conjugated molecules

Titanylphthalocyanine Films on Ag(111): An Epitaxial Metal/Organic Heterosystem with an Exceptional Smooth Surface

Contact Info

Product

Resources

About

Initial Stage of para-Hexaphenyl Thin-Film Growth Controlled by the Step Structure of the Ion-Beam-Modified TiO₂(110) Surface

Initial Stage of para-Hexaphenyl Thin-Film Growth Controlled by the Step Structure of the Ion-Beam-Modified TiO₂(110) Surface