Structure and Ordering Principles of Ultrathin Organic Molecular Films on Surfaces of Layered Semiconductors Organic‐on‐Inorganic MBE
TL;DR: In this article, the conditions necessary for order formation are analyzed for hexabenzocoronene (HBC) and naphthalene-tetracarboxylic-dianhydride (NTCDA) on graphite, MoS 2 and GeS.
Abstract: Epitaxially ordered thin films of large planar organic molecules can be obtained on layered inorganic semiconductors by organic molecular beam deposition in UHV. Analysis by low energy electron diffraction (LEED) and thermal desorption spectroscopy (TDS) yields structural parameters and binding energies. The conditions necessary for order formation are analyzed. Epitaxial data are given for hexabenzocoronene (HBC) and naphthalene-tetracarboxylic-dianhydride (NTCDA) on graphite, MoS 2 and GeS.
Citations
More filters
TL;DR: In this article, the structural phases and the growth of self-assembled monolayers (SAMs) are reviewed from a surface science perspective, with emphasis on simple model systems, and a summary of the techniques used for the study of SAMs is given.
2,374 citations
TL;DR: The effect of room temperature ultraviolet-ozone (UV-O3) exposure of MoS2 on the uniformity of subsequent atomic layer deposition of Al2O3 is investigated in this paper.
Abstract: The effect of room temperature ultraviolet-ozone (UV-O3) exposure of MoS2 on the uniformity of subsequent atomic layer deposition of Al2O3 is investigated. It is found that a UV-O3 pre-treatment removes adsorbed carbon contamination from the MoS2 surface and also functionalizes the MoS2 surface through the formation of a weak sulfur-oxygen bond without any evidence of molybdenum-sulfur bond disruption. This is supported by first principles density functional theory calculations which show that oxygen bonded to a surface sulfur atom while the sulfur is simultaneously back-bonded to three molybdenum atoms is a thermodynamically favorable configuration. The adsorbed oxygen increases the reactivity of MoS2 surface and provides nucleation sites for atomic layer deposition of Al2O3. The enhanced nucleation is found to be dependent on the thin film deposition temperature.
166 citations
TL;DR: While most examples are related to small-molecule organic semiconductors, many of the ideas can be applied to other systems and comment on implications for device applications.
Abstract: We review basic concepts as well as recent examples and applications of organic–organic heterostructures. We organize the different types of heterostructures according to material A deposited on material B (A/B), A co-deposited with B (A:B), heterostructures in the monolayer regime including nanostructuring concepts and systems involving self-assembled monolayers, as well as various other architectures, including superlattices. While most examples are related to small-molecule organic semiconductors, many of the ideas can be applied to other systems. The central theme is growth and structure as well as optical and electronic properties. Finally, we comment on implications for device applications.
138 citations
TL;DR: In this paper, a growth temperature-dependent morphology transition from smooth films to well-separated islands has been observed which can be related to changes of the crystal structure, similar to the Nishiyama-Wassermann and Kurdjumov-Sachs relations.
Abstract: The planar organic molecule 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) deposited on Ag(111) has been used as a model system for organic molecular-beam epitaxy (OMBE). The crystal structure and morphology of thin films in the range of $50--200\mathrm{\AA{}}$ have been examined in detail as a function of the growth parameters by x-ray diffraction and noncontact atomic force microscopy. Evidence for the coexistence of $\ensuremath{\alpha}$- and $\ensuremath{\beta}$-like structures has been found for a variety of growth conditions. A growth temperature-dependent morphology transition from smooth films to well-separated islands has been observed which can be related to changes of the crystal structure. These changes of the crystal structure can be rationalized similar to the Nishiyama-Wassermann and the Kurdjumov-Sachs relations. The island density and size show a similar temperature-dependent behavior as observed for MBE-grown inorganic thin films. A rate-equation-based analysis is used to estimate an effective diffusion barrier for the surface self-diffusion of PTCDA.
96 citations
TL;DR: This Perspective will give an overview on optical reflectance spectroscopy of highly ordered organic thin films in the thickness range from submonolayers to several monolayers, as a tool to study the absorption behavior of such films and emphasize the relations between the physical layer structure and the resulting optical properties.
Abstract: This Perspective does not have the ambition to entirely review the subject of optical spectroscopy on thin organic films. What we will try to achieve instead is to give an overview on optical reflectance spectroscopy of highly ordered organic thin films in the thickness range from submonolayers to several monolayers, as a tool to study the absorption behavior of such films. By doing so, we will emphasize the relations between the physical layer structure and the resulting optical properties. More specifically, we intend to show on the basis of particular examples what physical effects can be favorably examined by means of real-time optical spectroscopy, i.e., applied during the actual film growth, especially differential reflectance spectroscopy (DRS). Epitaxial organic films on inorganic substrates (insulators and conductors) will be in focus, and also the perspectives of investigating organic-organic heteroepitaxial layers will be addressed.
92 citations
References
More filters
TL;DR: This paper is a review of recent progress made in organic thin films grown in ultrahigh vacuum or using other vapor-phase deposition methods and describes the most important work which has been published in this field since the emergence of OMBD in the mid-1980s.
Abstract: During the past decade, enormous progress has been made in growing ultrathin organic films and multilayer structures with a wide range of exciting optoelectronic properties. This progress has been made possible by several important advances in our understanding of organic films and their modes of growth. Perhaps the single most important advance has been the use of ultrahigh vacuum (UHV) as a means to achieve, for the first time, monolayer control over the growth of organic thin films with extremely high chemical purity and structural precision.1-3 Such monolayer control has been possible for many years using well-known techniques such as Langmuir-Blodgett film deposition,4 and more recently, self-assembled monolayers from solution have also been achieved.5 However, ultrahighvacuum growth, sometimes referred to as organic molecular beam deposition (OMBD) or organic molecular beam epitaxy (OMBE), has the advantage of providing both layer thickness control and an atomically clean environment and substrate. When combined with the ability to perform in situ highresolution structural diagnostics of the films as they are being deposited, techniques such as OMBD have provided an entirely new prospect for understanding many of the fundamental structural and optoelectronic properties of ultrathin organic film systems. Since such systems are both of intrinsic as well as practical interest, substantial effort worldwide has been invested in attempting to grow and investigate the properties of such thin-film systems. This paper is a review of recent progress made in organic thin films grown in ultrahigh vacuum or using other vapor-phase deposition methods. We will describe the most important work which has been published in this field since the emergence of OMBD in the mid-1980s. Both the nature of thin-film growth and structural ordering will be discussed, as well as some of the more interesting consequences to the physical properties of such organic thin-film systems will be considered both from a theoretical as well as an experimental viewpoint. Indeed, it will 1793 Chem. Rev. 1997, 97, 1793−1896
1,809 citations
TL;DR: In this article, the nucleation, growth, step site interaction, and superstructures of two perylene derivatives were investigated and compared using scanning tunnelling microscopy (STM) and low energy electron diffraction.
297 citations
TL;DR: In this article, the authors studied the epitaxial growth of vapor-deposited crystalline phthalocyanine films on single-crystal copper substrates using low-energy electron diffraction.
Abstract: Monolayer structures and epitaxial growth of vapor‐deposited crystalline phthalocyanine films on single‐crystal copper substrates were studied using low‐energy electron diffraction At monolayer coverage, ordered layers of copper‐, iron‐, and metal‐free phthalocyanines were observed on both Cu(100) and Cu(111) With increasing film thickness, ordered multilayer structures of these phthalocyanines were also seen on both substrates at 300 K surface temperature All three phthalocyanines had identical monolayer and multilayer surface structures on Cu(100) On the Cu(111) substrate, the three phthalocyanines exhibited slightly different surface structures, indicating the importance of the central metal atom in the interaction with the substrate that influences the monolayer surface structure and the ordering during crystal growth The multilayer crystalline films did not have surface structures characteristic of the bulk crystal structure but rather had a surface unit mesh compatible with a single molecule per unit mesh, oriented parallel to the surface Electron beam damage and space charge effects were negligible for film thicknesses up to 500–1000 A
158 citations
TL;DR: In this paper, it is shown that highly ordered monolayers and thin films of large organic molecules can be prepared by vapour deposition on inorganic single-crystal surfaces using complementary surface-sensitive techniques such as NEXAFS, LEED and STM.
133 citations
TL;DR: In this paper, it was shown that the epitaxial growth of organic films is possible on such technologically important materials as silicon and GaAs, if the surfaces of those substrates are changed into quasi van der Waals ones by the proper termination of surface dangling bonds with suitable atoms.
91 citations