Crystallization and semiconductor-metal switching behavior of thin VO₂ layers grown by atomic layer deposition

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• 作者：Geert Rampelberg ; Davy Deduytsche ; Bob De Schutter ; Peter Antony Premkumar ; Michael Toeller ; Marc Schaekers ; Koen Martens ; Iuliana Radu ; Christophe Detavernier
• 关键词：Vanadium dioxide ; Atomic layer deposition ; Crystallization ; Semiconductor&ndash ; metal transition ; X-ray diffraction ; Ellipsometry ; In-situ
• 刊名：Thin Solid Films
• 出版年：1 January, 2014
• 年：2014
• 卷：550
• 期：Complete
• 页码：59-64
• 全文大小：1891 K

文摘

Crystalline vanadium dioxide (VO₂) thin films were prepared by annealing amorphous VO₂ films which were deposited by atomic layer deposition on a SiO₂ substrate. A large influence of the oxygen partial pressure in the annealing ambient was observed by means of in-situ X-ray diffraction. In the range between 1 and 10 Pa of oxygen the interesting VO₂(R) phase crystallized near 450 掳C. Between 2 and 10 Pa of oxygen, metastable VO₂(B) was observed as an intermediate crystalline phase before it transformed to VO₂(R). Anneals in inert gas did not show any crystallization, while oxygen partial pressures above 10 Pa resulted in oxidation into the higher oxide phase V₆O₁₃. Film thickness did not have much effect on the crystallization behavior, but thinner films suffered more from agglomeration during the high-temperature crystallization on the SiO₂ substrate. Nevertheless, continuous polycrystalline VO₂(R) films were obtained with thicknesses down to 11 nm. In the case where VO₂(R) was formed, the semiconductor-metal transition was observed by three complementary techniques. This transition near 68 掳C was characterized by X-ray diffraction, showing the transformation of the crystal structure, by spectroscopic ellipsometry, mapping optical changes, and by sheet resistance measurements, showing resistance changes larger than 2 orders of magnitude between the low-temperature semiconducting state and the high-temperature metallic state.