Thermal stability and electrical conduction behavior of coevaporated WSi2±x thin films

F. Nava*, B. Z. Weiss, K. Y. Ahn, D. A. Smith, King-Ning Tu

*Corresponding author for this work

Research output: Contribution to journalArticle

35 Scopus citations

Abstract

The thermal stability of coevaporated amorphous WSi 2±x(x≅±0.2) thin films from room temperature to 1000 °C has been studied by in situ resistivity measurements and hot-stage transmission-electron microscopy. During continuous heating two consecutive phase transformations were observed to occur via nucleation and growth processes. The first which occurs at ∼420 °C is the crystallization of the amorphous film to a metastable, semiconducting hexagonal phase WSi 2. The second which occurs at ∼620 °C is the transformation of the hexagonal phase to the thermodynamically stable, metallic, tetragonal phase of WSi2. The hexagonal phase is characterized by an acicular morphology and its formation is associated with a drastic increase in resistivity. The crystallites (grains) of the stable tetragonal phase are equiaxed and their formation is associated with a rapid decrease in resistivity. In order to achieve a low value of resistivity, ∼70 μΩ cm at room temperature, the tetragonal phase must be annealed to the neighborhood of 1000 °C. The activation energy for the hexagonal to tetragonal transformation (∼3 eV) was found to be higher than that for the crystallization (∼2 eV). The mode parameters for both transformations were found to be almost the same, n∼2. The characteristics of both transformations were not greatly influenced by the compositional changes.

Original languageEnglish
Pages (from-to)354-364
Number of pages11
JournalJournal of Applied Physics
Volume64
Issue number1
DOIs
StatePublished - 1 Dec 1988

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