Reactions of thin-film multilayers

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1993

OSTI ID:7020003

Novet, T

High reaction temperatures used in traditional solid-state synthesis techniques limit possible products to thermodynamically most-stable phases. In order to avoid these high temperatures, a synthetic method has been developed in which thin-film multilayers are used as starting reactants. Short diffusion lengths permit the intimate mixing of elements at low temperatures (<300[degrees]C) to form an amorphous alloy. From this alloy, a crystalline product nucleates directly. Separating interdiffusion from nucleation in this manner allows the preparation of metastable solid-state compounds. An understanding of each of the steps in a reaction is necessary in order to control the products. The first step, interdiffusion of the multilayer, is monitored using x-ray diffraction. As a multilayer diffuses, the composition profile at each interface changes, altering diffraction intensities. By following the changes in a diffraction pattern as a function of time and temperature, a detailed picture of the interdiffusion of three metal-silicon multilayers systems are presented. The final step in this synthetic technique is the nucleation of a crystalline product from the amorphous intermediate. Energetics of nucleation determines the phase which forms. By controlling nucleation barriers, it is possible to direct a chemical reaction. The composition dependence of nucleation temperatures as a method to affect nucleation of a chosen phase is also discussed. Finally, the preparations of metastable compounds using this technique is demonstrated.

• Research Organization: Oregon Univ., Eugene, OR (United States)
• OSTI ID: 7020003
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360101* -- Metals &amp; Alloys-- Preparation &amp; Fabrication
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical &amp; Physicochemical Properties
ALLOYS
AMORPHOUS STATE
CHEMICAL PREPARATION
CHEMICAL REACTIONS
FILMS
LAYERS
NUCLEATION
SYNTHESIS
TEMPERATURE DEPENDENCE
THIN FILMS