The Resistivity Size Effect in Epitaxial Nb(001) and Nb(011) Layers
| Autor: | Mary E. McGahay, Daniel Gall, Erik Milosevic, Sit Kerdsongpanya, Baiwei Wang |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
010302 applied physics
Materials science Condensed matter physics Scattering Epitaxy Lambda 01 natural sciences Omega Electronic Optical and Magnetic Materials Orientation (vector space) Electrical resistivity and conductivity Product (mathematics) 0103 physical sciences Electrical and Electronic Engineering Sheet resistance |
| Zdroj: | IEEE Transactions on Electron Devices. 66:3473-3478 |
| ISSN: | 1557-9646 0018-9383 |
| DOI: | 10.1109/ted.2019.2924312 |
| Popis: | Epitaxial Nb(011) and Nb(001) layers are sputter deposited onto ${a}$ -plane and ${r}$ -plane sapphire substrates, respectively, and their resistivity $\rho $ measured in situ , ex situ , and at 77 K as a function of layer thickness ${d}= 4$ –400 nm. The resistivity increase with decreasing ${d}$ is independent of layer orientation and is described with the model by Fuchs and Sondheimer (FS), providing a value for the bulk electron mean free path $\lambda = {20} \pm {2}$ nm at room temperature. Exposure to air causes a 1.5-nm-thick surface oxide and an increase in $\rho $ by up to 74%, suggesting a decrease in the surface scattering specularity from ${p}_{{{1}}}= {0.9} \pm {0.1}$ at the Nb-vacuum interface to completely diffuse scattering ( ${p}_{{{1}}}= {0}$ ) at the oxidized Nb surface. Alternatively, this increase in resistance can be attributed to roughening during surface oxidation while retaining completely diffuse scattering, yielding a lower bound for the room-temperature $\lambda $ of 9.0±0.4 nm. The product of the bulk resistivity $\rho _{o}$ times $\lambda $ is temperature-independent and, depending on either choosing the roughness or the specularity interpretation, $\rho _{o}\,\,\lambda = {14}\times {10}^{{-{16}}}$ or ${30} \times {10}^{{-{16}}}\,\,\Omega \text{m}^{{{2}}}$ , respectively. These values are 3.9 and 8.5 times larger than $\rho _{o}~\lambda $ from a previous theoretical prediction, indicating a dramatic break down of the classical FS model for Nb and indicating that the resistivity size effect in Nb is considerably larger than predicted earlier. They are also larger than for W, Ru, and Co, making Nb not promising for high-conductivity narrow interconnect lines. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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