SiC protective coating for photovoltaic retinal prosthesis

Xin Lei, Sheryl Kane, Stuart Cogan, Henri Lorach, Ludwig Galambos, Philip Huie, Keith Mathieson, Theodore Kamins, James Harris, Daniel Palanker

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31 Citations (Scopus)
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OBJECTIVE: To evaluate plasma-enhanced, chemically vapor deposited (PECVD) amorphous silicon carbide (α-SiC:H) as a protective coating for retinal prostheses and other implantable devices, and to study their failure mechanisms in vivo.

APPROACH: Retinal prostheses were implanted in rats sub-retinally for up to 1 year. Degradation of implants was characterized by optical and scanning electron microscopy. Dissolution rates of SiC, SiN x and thermal SiO2 were measured in accelerated soaking tests in saline at 87 °C. Defects in SiC films were revealed and analyzed by selectively removing the materials underneath those defects.

MAIN RESULTS: At 87 °C SiN x dissolved at 18.3 ± 0.3 nm d(-1), while SiO2 grown at high temperature (1000 °C) dissolved at 0.104 ± 0.008 nm d(-1). SiC films demonstrated the best stability, with no quantifiable change after 112 d. Defects in thin SiC films appeared primarily over complicated topography and rough surfaces.

SIGNIFICANCE: SiC coatings demonstrating no erosion in accelerated aging test for 112 d at 87 °C, equivalent to about 10 years in vivo, can offer effective protection of the implants. Photovoltaic retinal prostheses with PECVD SiC coatings exhibited effective protection from erosion during the 4 month follow-up in vivo. The optimal thickness of SiC layers is about 560 nm, as defined by anti-reflective properties and by sufficient coverage to eliminate defects.

Original languageEnglish
Article number046016
Number of pages13
JournalJournal of Neural Engineering
Issue number4
Publication statusPublished - 21 Jun 2016


  • SiC
  • silicon carbide
  • retinal prostheses
  • protective coating
  • neural stimulation
  • chronic implant


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