https://is.muni.cz/el/1431/podzim2006/C7780/um/Read/2711172/SAM_str_grwth_ProgSurfSci00_151.pdf

Structure and growth of self-assembling monolayers

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.

/pdf/mos2-functionalization-for-ultra-thin-atomic-layer-deposited-1p48wu3wk1.pdf

MoS2 functionalization for ultra-thin atomic layer deposited dielectrics

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.

/pdf/organic-organic-heterostructures-concepts-and-applications-umfl7yuurb.pdf

Organic–Organic Heterostructures: Concepts and Applications

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.

Structure and growth morphology of an archetypal system for organic epitaxy: PTCDA on Ag(111)

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.

https://www.uv.es/wsetld/archivos/Wednesday/WS10-Fritz.pdf

Optical differential reflectance spectroscopy of ultrathin epitaxial organic films

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.

Ch. Guenther

Papers

Structure and Ordering Principles of Ultrathin Organic Molecular Films on Surfaces of Layered Semiconductors Organic‐on‐Inorganic MBE