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Substrate temperature effects on laser crystallized NiTi thin films
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10.1063/1.3093678
/content/aip/journal/jap/105/7/10.1063/1.3093678
http://aip.metastore.ingenta.com/content/aip/journal/jap/105/7/10.1063/1.3093678
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

XRD spectrum of as-deposited film. Note the amorphous scattered signal indicative of room temperature sputtered NiTi. Heat treated spectrum shifted for clarity.

Image of FIG. 2.
FIG. 2.

SEM image of an array of irradiated regions. Irradiated regions are with uniform energy density. Each square region represents one energy density.

Image of FIG. 3.
FIG. 3.

Schematic representations of the (a) PM, (b) NCM, and (c) CM regimes.

Image of FIG. 4.
FIG. 4.

Reflectivity spectrum for an amorphous and a number of heat treated films. This change in reflectivity, due to oxidation, particularly at , is consistent with observed enhanced laser-film energy coupling (Ref. 29).

Image of FIG. 5.
FIG. 5.

XPS spectrum of heat treated film confirming presence of .

Image of FIG. 6.
FIG. 6.

XRD spectra for the as-deposited amorphous spectrum and the room temperature, laser treated specimen (completely melted) confirming crystallization as well as heterogeneous nucleation. Additionally, it is seen that a metastable phase results due to the exceedingly high quench rate.

Image of FIG. 7.
FIG. 7.

XRD spectra depicting the thermally induced phase transformation. Note that emergence of the austenitic phase upon heating and subsequent disappearance upon cooling. The persistence of the [110] austenitic peak suggests a phase mixture of austenite and martensite upon cooling back down to room temperature.

Image of FIG. 8.
FIG. 8.

XRD spectra for room temperature and substrate temperature. Room temperature processing results in metastable phase formation, while an elevated substrate temperature processing results in the formation of austenite. Note that both films were laser treated above their respective complete melt thresholds and result in highly textured films implying heterogeneous nucleation.

Image of FIG. 9.
FIG. 9.

Schematic load curve for typical nanoindentation experiment. Note that the total energy input to the system is equal to the sum of the dissipated and recovered energy.

Image of FIG. 10.
FIG. 10.

Load curve comparisons between specimens processed at room temperature , , and . Note that all specimens presented here were laser treated with energy densities above their respective CMTs.

Image of FIG. 11.
FIG. 11.

Energy recovery ratio as a function of maximum indenter load for films laser processed at room temperature , , and . It is seen here that the film processed at recovers significantly more energy upon unloading due to its superelastic response. Note that all specimens presented here were laser treated with energy densities above their respective CMTs.

Image of FIG. 12.
FIG. 12.

Load responses of laser treated and untreated films for elevated substrate temperatures of and . Note the increased slope as well as increased depth recovery for the laser treated, [200] textured film treated at . The load response of a precrystallized (no laser treatment) film at is also included for reference.

Image of FIG. 13.
FIG. 13.

Effective film modulus for films laser processed at room temperature , , and . Effective film moduli for precrystallized (no laser treatment) and amorphous films are also included for reference. The asterisk denotes that laser treated specimen presented here have undergone CM, and thus nucleation and growth in order to solidify.

Image of FIG. 14.
FIG. 14.

[(a) and (b)] temperature: representative AFM image from completely melted film. Note the presence of lateral growth, although not well defined or of significant length, .

Image of FIG. 15.
FIG. 15.

Scanning electron micrographs, : [(a) and (b)] interior and boundary regions, respectively. Partially melted film characterized by small grain size limited to film thickness, : [(c) and (d)] interior and boundary regions, respectively. NCM regime characterized by bimodal grain size distribution, : [(e) and (f)] interior and boundary regions, respectively. Completely melted film characterized by the presence of large aspect ratio, well defined lateral growth, .

Image of FIG. 16.
FIG. 16.

Average grain size as a function of % CMT. Note the evolution of grain size distribution as the energy density transitions through the PM, NCM, and CM regimes.

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/content/aip/journal/jap/105/7/10.1063/1.3093678
2009-04-01
2014-04-24
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Substrate temperature effects on laser crystallized NiTi thin films
http://aip.metastore.ingenta.com/content/aip/journal/jap/105/7/10.1063/1.3093678
10.1063/1.3093678
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