Structure and morphology of sexiphenyl thin films grown on aluminium (1 1 1) (original) (raw)

Epitaxial Growth of Sexiphenyl on Al(111): From Monolayer to Crystalline Films

Langmuir, 2004

A combination of in situ surface sensitive-techniques, UV photoemission and low energy electron diffraction, with ex situ bulk sensitive X-ray diffraction reveals the formation of epitaxial thin films of sexiphenyl on Al(111) starting from the first monolayer. For room temperature growth, highly ordered films are formed with a unique alignment of the sexiphenyl molecules with the long axes of all molecules aligned parallel to both the surface and the 〈11 h0〉 azimuthal directions of Al(111). This is related to a densely packed highly commensurate first monolayer, which acts as a template for the unique (213 h) crystallite orientation observed.

Ordered mono- and multilayer films of sexiphenyl on Al(111): a LEED investigation

Thin Solid Films, 2003

Here we report the results of a low energy electron diffraction (LEED) investigation of monolayer and multilayer films of para-sexiphenyl grown on Al(111) at room and elevated substrate temperatures. For growth at room temperature an ordered monolayer is observed with LEED that indicates the molecules are oriented parallel to the substrate. For further growth up to 80 A (approx. 16 ML) the LEED pattern remains unaltered indicating a well-ordered film is formed, with the molecules remaining parallel to the substrate. At elevated substrate temperatures the first monolayer is identical to that at room temperature, however, growth on this wetting layer leads to a completely different diffraction pattern that can only be explained by 6P crystallites oriented such that the molecules are near perpendicular to the Al substrate. The two distinct 2D unit cells that are observed to coexist in this high temperature grown film indicate that the substrate causes a strong deviation from the bulk crystal structure of sexiphenyl. ᮊ

Molecular alignments in sexiphenyl thin films epitaxially grown on muscovite

Thin Solid Films, 2003

The epitaxial orientations of highly crystalline para-sexiphenyl (C H ) films on mica (001) surfaces are investigated by 36 26 selected area electron diffraction (SAED) and transmission electron microscopy (TEM). Films at the early growth stage (growth time 26 s) and at an advanced growth stage (growth time 10 min) are studied. Films at the early growth stage exhibit only threedimensional islands with an average size of 60=30=10 nm , whereas films at an advanced growth stage consist of long oriented 3 nano-fibres with a needle-like morphology. We identified three different types of epitaxial relations between the mica (001) substrate and the sexiphenyl crystallites, which are the same in both growth stages. Moreover, within a single island as well as within a single fibre crystalline domains with these three epitaxial orientations are observed. At the advanced growth stage, these domains are aligned antiparallel or perpendicular to the fibre axes; the typical size of the domains is 20 nm. ᮊ

Highly ordered anisotropic nano-needles in para-sexiphenyl films

Thin Solid Films, 2002

Atomic force microscopy (AFM) was used to investigate the early growth stage of highly ordered para-sexiphenyl thin films deposited by hot wall epitaxy on mica, in order to find the process controlling parameters. It was shown that the growth time and surface type are important parameters for controlling of the film morphology, in terms of the degree of anisotropy and long range order. X-Ray diffraction pole figure technique and transmission electron diffraction was also used to characterize the crystallographic structure of the thicker films. ᮊ

Investigation of the Temperature-Dependent Surface Morphology of p-Sexiphenyl Thin Films on KCl(001)

MRS Proceedings, 2001

ABSTRACTInvestigation into the temperature dependence of the surface morphology of a thin film of p-sexiphenyl (p-6P) on KCl(001) was carried out by atomic force microscopy (AFM). An individual p-6P film was prepared by vapor deposition at a base pressure of ∼1x10-8 mbar onto a KCl(001) surface which was maintained at 323 K during deposition. The AFM was carried out in a separate vacuum chamber, in situ, at a base pressure of ∼1x10-6 mbar. The p-6P film was cooled and maintained at discrete temperatures in the range from 294 K to 128 K as AFM measurements were performed. Similar surface morphologies are observed for film temperatures maintained at 294, 264, and 227 K, and 188 and 128 K during the AFM measurements. AFM images for the first set of film temperatures (294 - 227 K) indicate the presence of block-like islands of p-6P, with well-defined crystallite boundaries. AFM images of the films in the second set (188 and 128 K) indicate the presence of triangular wedge-shaped structu...

Structural relationship between epitaxially grown para-sexiphenyl and mica (0 0 1) substrates

Journal of Crystal Growth, 2002

This study focuses on structural properties of para-sexiphenyl (PSP) epitaxial thin films grown on freshly cleaved mica (0 0 1) substrates. The layers were prepared by hot wall epitaxy (HWE) technique resulting in highly ordered organic structures with a needle-like morphology on the substrates. X-ray diffraction (XRD) pole figure technique, transmission electron diffraction (TED) and atomic force microscopy were used to characterise the epitaxial growth. However, on not perfectly cleaved mica substrates the needle direction can change around 1201 when the films are grown on different terraces of mica (0 0 1) which are separated by cleavage steps. This behaviour can be referred to the properties of the monoclinic crystal structure of mica which is described in detail. r

In-plane alignment of para-sexiphenyl films grown on KCl(0 0 1)

Applied Surface Science, 2002

The three-dimensional growth of para-sexiphenyl (p-6P) on KCl(0 0 1) is characterized by a large polymorphism. Using grazingincidence diffraction, we have found that two of the known ®ve orientational phases feature preferential in-plane alignments along the [1 1 0] in-plane direction of the substrate: p-6P(1 1 À1) k KCl(0 0 1) with [1 À1 0] k KCl[1 1 0] as well as p-6P(0 0 1) k KCl(0 0 1) with [1 À1 0] k KCl[1 1 0]. The latter structure is a peculiar low-symmetry con®guration, which can be understood by analysis of the molecular crystal lattice and the substrate symmetry. #

Evolution of epitaxial order in para-sexiphenyl on KCl(100)

Journal of Crystal Growth, 2010

This work focuses on the structural and morphological studies of the evolution of epitaxially grown para-sexiphenyl (p-6P) thin films on freshly cleaved KCl(1 0 0) surfaces. The film growth is varied using growth times between 5 sec and 60 min and substrate temperatures in the range of 80-150 1C. The study is based on a combination of X-ray diffraction to derive structural information on the molecular scale, and atomic force as well as electron microscopy to obtain morphological information. The initial growth orientation of p-6P crystallites is identified to be ð2 0 3Þ-oriented, which consists of edge-on molecules aligned parallel to /0 1 1SKCl forming needles that are also parallel to these directions. Furthermore it is shown that surface step edges do not affect the needle growth, but those needles even overgrow step edges. The subsequent epitaxial growth turned out to be crucially dependent on the substrate temperature with respect to the quantitative ratios of material in different growth orientations, their in-plane alignment, the size of crystallites and the mosaicity of the films. It is shown that some crystallites start their growth using the initially grown needles as seeds, resulting in a different crystal orientation. For such crystallites a realignment of needles during their growth is identified, which is found to be strongly dependent on the growth temperature. Furthermore the heights of needles show distinct temperature dependence. In addition well-aligned terraced islands formed by standing molecules were observed. Finally a growth model for this system can be elucidated.