### Abstract

We measured the height of Pd microdisks during H_{2} exposure using epi-illumination diffraction phase microscopy, a quantitative phase imaging technique for capturing nanoscale dynamics in situ. From these microdisk height measurements, we extracted the axial expansion coefficient as a function of H_{2} concentration as well as image sequences that show the instantaneous rate of axial expansion in a spatially and temporally resolved manner. Quantifying these two parameters is important in modeling Pd-based H_{2} sensors. For H_{2} concentrations below 0.5%, i.e. an order of magnitude below the lower explosive limit, the axial expansion coefficient followed the Freundlich distribution: Δh(c) = 1.28 c^{0.51} where Δh is the percentage change in height of the Pd microdisk and c is the percent concentration of H_{2} in N_{2}. The fit agrees well with the anticipated square root dependence for diatomic gas.

Original language | English (US) |
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Pages (from-to) | 2559-2564 |

Number of pages | 6 |

Journal | Optical Materials Express |

Volume | 4 |

Issue number | 12 |

DOIs | |

State | Published - 2014 |

### ASJC Scopus subject areas

- Electronic, Optical and Magnetic Materials

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## Cite this

*Optical Materials Express*,

*4*(12), 2559-2564. https://doi.org/10.1364/OME.4.002559