High-temperature structural stability of MoSi{sub 2}-based nanolayer composites
- Center for Materials Science, Los Alamos National Laboratory, Los Alamos, New Mexico 87454 (United States)
- Technical Research Centre of Finland, Espoo (Finland)
- Center for Materials Science and Ceramic Science and Technology Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87454 (United States)
A systematic study of the high-temperature structural stability is reported for the following three nanolayered composites: (1) MoSi{sub 2}--MoSi{sub 2}N{sub {ital x}}, (2) Mo--MoSi{sub 2}N{sub {ital x}}, and (3) Mo--MoSi{sub 2}N{sub {ital x}}--MoSi{sub 2}, where {ital x}{similar_to}3--4. The alternating layers with layer thickness varying from 1 to 50 nm were synthesized by sputtering techniques. The structural evolution in these composites has been studied by cross-sectional transmission electron microscopy as a function of annealing temperature. As-deposited Mo layers exhibit nanocrystalline structure, while the other types of layers are amorphous in structure. With increasing annealing temperature, MoSi{sub 2} crystallizes to form a metastable {ital C}40 phase at {similar_to}500 {degree}C and then transforms to the stable {ital C}11{sub {ital b}} phase at {similar_to}900 {degree}C, while MoSi{sub 2}N{sub {ital x}} remains amorphous up to temperature as high as 1000 {degree}C. No difference in crystallization behavior was observed for the constituents in either single phase or multilayered form. One way to improve the toughness of MoSi{sub 2} is through the addition of a ductile phase, e.g., Mo. However, the Mo and MoSi{sub 2} layers react and the layer structure deteriorates. Previous study has shown that the compound, MoSi{sub 2}N{sub {ital x}}, stays amorphous at 1000 {degree}C. This suggests that it could function either as a stable second-phase reinforcement or as a diffusion barrier between Mo and MoSi{sub 2}. The MoSi{sub 2}--MoSi{sub 2}N{sub {ital x}}, Mo--MoSi{sub 2}N{sub {ital x}}, and Mo--MoSi{sub 2}--MoSi{sub 2}N{sub {ital x}} nanolayers are found to remain stable up to 900 {degree}C (highest temperature tested). {copyright} {ital 1995} {ital American} {ital Vacuum} {ital Society}
- OSTI ID:
- 57128
- Journal Information:
- Journal of Vacuum Science and Technology. B, Microelectronics Processing and Phenomena, Vol. 13, Issue 3; Other Information: PBD: May 1995
- Country of Publication:
- United States
- Language:
- English
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