Micro-Raman spectroscopy and X-ray diffraction studies of atomic-layer-deposited ZrO2 and HfO2 thin films

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Raman spectroscopy and X-ray diffraction (XRD) methods were applied to characterize ZrO2 and HfO2 films grown by atomic layer deposition (ALD) on silicon substrates in chloride- based processes. A dramatic enhancement in spectral quality of Raman data resulted from the use of the film's freestanding edges for experimental runs between 80 and 800 cm−1. Both techniques detected a preferential formation of a metastable phase in ZrO2 and HfO2 films at 500 and 600°C, respectively, during the initial stages of ALD. In the case of ZrO2 films this phase was identified as the tetragonal polymorph of ZrO2 (t-ZrO2). XRD and Raman spectroscopy data showed that, in contrast to the monoclinic phase (m-ZrO2), the absolute amount of t-ZrO2 remained approximately constant while its relative amount decreased with the increase of the film thickness from 56 to 660 nm. Neither XRD nor Raman spectroscopy allowed unambiguous identification of the metastable phase formed in otherwise monoclinic HfO2 films.

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