CC BY
11ВКВО-2021- СТЕНДОВЫЕ ДОКЛАДЫ
incident light
Raman signal
DOI 10.24412/2308-6920-2021-6-432
ЭФФЕКТ ВОДЫ НА ЭЛЕКТРИЧЕСКИЙ ГИСТЕРЕЗИС УГЛЕРОДНЫХ ПОКРЫТИЙ ОПТИЧЕСКИХ ВОЛОКОН
1 1 12 2 Харинцев С.С. , Сапарина С.В. , Фишман А.И. , Столов А.А. , Джи Ли
'Казанский федеральный университет 2OFS, 55 Darling Drive, Avon, CT, 0600', USA
В работе изучается электрический и спектроскопический гистерезис углеродных покрытий при мягком отжиге (до 150оС) в присутствии/отсутствии воды.
Amorphous carbon (a-C) is an appealing disordered multi-phase material widely used as a cost-effective barrier coating (10-100 nm thick) for silica optical fibers to protect them from harsh environments. Those coatings prevent strength degradation of the optical fibers by moisture and also block hydrogen diffusion into the fiber. The protective properties of a-C coatings, synthesized via thermal chemical vapor deposition (CVD), mainly depend upon their structural and morphological peculiarities controlled by hydrocarbon cracking temperature and the precursor gas type. In this paper, we experimentally study the in situ temperature-dependent dc electrical conductivity and Raman scattering of dried/wetted a-C coatings under
multiple heating/cooling cycles within the range of 40-120oC. At temperatures of above 80oC, we observe a hysteresis in both the dc electrical resistance and the Raman scattering intensity. This hysteresis is underpinned to two competing mechanisms. One of them is related to the escape of intercalated (or spatially confined) water from the a-C coating, causing the resistance decrease due to closing the bandgap. An opposite picture is observed when some water molecules experience dissociative absorption at the edge and basal defects that may be decorated with C-H, COOH/C-OH and C-O-C/C=O functional groups. Upon cooling, the functional groups interact with free water through hydrogen bonding predominately. Using a regularized least-squares method, the highly overlapped Raman bands within the range of 1000-2000 deconvoluted into 9 elementary peaks assigned to sp2/sp species and the edge functional groups. The content of water within the a-C coating is quantified through relative contributions of the water and edge defects-related Raman bands. This study expands our knowledge about a-C ultrathin films, originally designed as barrier coatings, towards promising ultracompact humidity sensors and next-generation adsorbents.
Acknowledgements
This work was supported by grant No. '9-12-00066 of the Russian Science Foundation. This work was done using equipment of Federal Center of Shared Facilities of Kazan Federal University.
carbon-coated optical fiber
Fig. 1. A principal scheme of the experimental setup for the in-situ temperature-dependent dc electrical and Raman measurements
cm-1 were
2/„„з carbon
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