Vibrational studies of interfaces using high-resolution electron energy loss spectroscopy

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:7072209

Colaianni, M L.B.

High-resolution electron energy loss spectroscopy (HREELS), Auger electron spectroscopy (AES) and thermal desorption mass spectroscopy (TDS) provide complimentary information on the structure, reactivity and thermal behavior of three classes of interfaces: (1) gas/metal, (2) gas/semiconductor, and (3) metal/metal-oxide interfaces. The structure and chemistry of CO and O[sub 2] adsorbed onto well-defined reactive metal surfaces have been examined to determine the elementary chemical steps and specific bonding structures which lead to dissociation of the adsorbate. Four distinct, interconvertible CO bonding structures were vibrationally identified and assigned on the Mo(110) surface. The reactive adsorption of oxygen into three distinct sites on the Mo(110) surface was probed from the earliest stages of low-temperature dissociative adsorption to the formation of thin films of molybdenum oxide at 1000 K. The synergistic effect of combining two normally-unreactive metals, Cu and Al, to induce CO dissociation at exceptionally low temperatures was examined. The effect of substrate surface structure on controlling the course of a reaction has been examined on silicon substrates. By utilizing Si(100)-(2x1) and Si(111)-(7x7), the presence of structurally-strained sites on the (7x7) activated thermal decomposition of molecularly adsorbed NH[sub 2] and PH[sub 2], whereas on the Si(100), these species recombined with an adsorbed H species upon heating. The metal/metal-oxide interface was studied. All the vapor-deposited metals retain their gas phase chemisorption capacity to higher than 600 K, while temperatures above 900 K cause the diffusion of the metal overlayer into the oxide support. SiO[sub 2] films were totally inert to metallic Sn penetration or diffusion. While tin could not be oxidized by molecular oxygen exposures, the incorporation of sodium oxide at the interface induced tin oxidation. Tin oxide exhibited an enhanced thermal stability on the SiO[sub 2] support.

• Research Organization: Pittsburgh Univ., PA (United States)
• OSTI ID: 7072209
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
664200 -- Spectra of Atoms & Molecules & their Interactions with Photons-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
CHALCOGENIDES
ELECTRON SPECTROSCOPY
ELEMENTS
ENERGY LEVELS
ENERGY-LOSS SPECTROSCOPY
EXCITED STATES
FLUIDS
GASES
INTERFACES
MASS SPECTRA
MATERIALS
METALS
MOLYBDENUM
OXIDES
OXYGEN COMPOUNDS
SEMICONDUCTOR MATERIALS
SEMIMETALS
SILICON
SORPTIVE PROPERTIES
SPECTRA
SPECTROSCOPY
STRUCTURAL CHEMICAL ANALYSIS
SURFACE PROPERTIES
TEMPERATURE DEPENDENCE
TRANSITION ELEMENTS
VIBRATIONAL STATES