Profile structures of ultrathin organic films on germanium/silicon multilayer substrates by x-ray interferometry/holography
Ultrathin organic films adsorbed or deposited on the surface of solid substrates have important potential for modifying the macroscopic properties of the surface to produce electronic and optical devices, biochemical sensors, protective layers, etc. The 3-dimensional structure of such ultrathin films, at the microscopic level, is essential for understanding the collective properties of the molecular assemblies and their macroscopic behavior, and achieving the desired control thereof at the molecular level. Here, the author employs x-ray interferometry technique to directly and uniquely derive the profile structures of two kinds of ultrathin organic films. The first kind is the physisorbed Langmuir-Blodgett (LB) film containing one, two and three bilayers of Cd-arachidate deposited on alkylated magnetron sputtered Ge/Si multilayer substrates; the second kind is the chemisorbed alkylsiloxane self-assembled monolayer (SAM) film of sixteen, eighteen and twenty carbon (C16, C18 and C20) on molecular beam epitaxy (MBE) fabricated Ge/Si multilayer substrates. High resolution meridional x-ray diffraction data were recorded from the substrates with or without the subsequently deposited or adsorbed films. The so-derived relative electron density profiles of these LB films have proven the correctness of the upstroke-downstroke structural asymmetry in the Cd-arachidate bilayers associated with the Langmuir-Blodgett deposition process. In the SAM case, it was found that the alkyl chains are all-trans and tilted away from the surface normal of approximately 32[degrees], 31[degrees], and 30[degrees] for the C16, C18 and C20 chains, respectively. This work demonstrates the power of the x-ray interferometry technique for solving an unknown structure by placing a known structure beside it. The profiles derived via x-ray interferometry were further proven correct utilizing the Patterson function in analogy to off-axis Fourier holography.
- Research Organization:
- Pennsylvania Univ., Philadelphia, PA (United States)
- OSTI ID:
- 7017331
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
74 ATOMIC AND MOLECULAR PHYSICS
CADMIUM COMPOUNDS
HOLOGRAPHY
INTERFEROMETRY
TOPOGRAPHY
EICOSANOIC ACID
GERMANIUM
COATINGS
SILICON
SILOXANES
SURFACE PROPERTIES
THIN FILMS
CARBOXYLIC ACIDS
ELEMENTS
FILMS
METALS
MONOCARBOXYLIC ACIDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SILICON COMPOUNDS
SEMIMETALS
360602* - Other Materials- Structure & Phase Studies
664200 - Spectra of Atoms & Molecules & their Interactions with Photons- (1992-)