Rapid growth of amorphous carbon films on the inner surface of micron-thick and hollow-core fibers

Ultrathick (> 25 μm) carbon films were obtained on the inner surface of hollow and micron-thick quartz fibers by confining CH₄/He or C₂H₂/He microplasmas in their hollow cores. The resulting carbon films were studied by using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The microplasma-enhanced chemical vapor deposition (CVD) technique resulted in the uniform growth of amorphous carbon films on the inner surface of very long (> 1 m) hollow-core fibers. Film deposition is performed by using microplasmas at atmospheric pressure and at 50 Pa. The carbon films obtained with the latter show the smooth inner surfaces and the well continuity across the film/optical fiber. Low-pressure CH₄/He and C₂H₂/He microplasmas can lead to a rapid growth (∼ 2.00 μm/min) of carbon films with their thickness of > 25 μm. The optical emission measurements show that various hydrocarbon species were formed in these depositing microplasmas due to the collisions between CH₄/C₂H₂ molecules and energetic species. The microplasma-enhanced CVD technique running without the complicated fabrication processes shows its potentials for rapidly depositing the overlong carbon tubes with their inner diameters of tens of microns. - Highlights: • The microplasma device is applied for coating deposition inside hollow-core fibers. • The microplasma device results in > 25 μm-thick carbon films. • The microplasma device is simple for deposition of ultralong carbon tubes