| Title: | Characterization of alpha and beta phases of tantalum coatings |
| Author: | |
| Document Type: | Thesis |
| Department: | Committee for the Interdisciplinary Program in Materials Science and Engineering |
| Degree: | Master of Science |
| Major: | Materials Science and Engineering |
| Advisory Committee: |
Tyson, Trevor
Sosnowski, Marek
Axe, Lisa
|
| Thesis Date: | 2001, August |
| Keywords: |
Tantalum Coatings
|
| Availability: | Unrestricted |
| Abstract: |
Sputtered tantalum forms
two phases - α and β. The α and β phases have
distinctly different crystalline structures and properties. The structure
and the causes of formation of the β phase are still being studied
by researchers. This is a study to distinguish and characterize these
two phases. Samples from Bennet Labs and NJIT were characterized using
techniques such as SEM, EDX, XRF, XRD, TEM and XAFS. Samples deposited
at NJIT were used for an experimental study on the conditions favoring
the formation of the phases, by depositing tantalum on heated steel and
silicon substrates, additionally TEM analysis was carried out for a sample
having a mixture of α and β phases to study its differences.
The XRD results shows one of the sample to be highly textured β
Tantalum. The XAFS results also show the α. phase to have a bcc
structure with the characterstic coordination of bulk tantalurn.The local
structure of β tantalum is compared to a theoretical model of
P41mnm space group. The study confirm that the structure of tantalum belongs
to this space group and has a 30-atom unit cell isomorphous with Uranium.
The coordination of Ta atoms in the β phase is seen to be non
isotropic. The results of the heating experiments suggest that coatings
deposited on substrates without heating favored the formation of the β
phase. The TEM analysis shows the β phase to be made up of larger
grains of size 100-120 nm, which are about 4 times the size of the (αphase
grains.
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| Complete Thesis: | njit-etd2001-038 (107 pages ~ 4,108 KB pdf) |
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Created December 18, 2002
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