The work presented here introduces a materials strategy that involves physically transferred, ultrathin layers of silicon dioxide (SiO2) thermally grown on silicon wafers and then coated with hafnium oxide (HfO2) by atomic layer deposition, as barriers that satisfy requirements for even the most challenging flexible electronic devices. Materials and physics aspects of hydrolysis and ionic transport associated with such bilayers define their performance and reliability characteristics. Systematic experimental studies and reactive diffusion modeling suggest that the HfO2 film, even with some density of pinholes, slows dissolution of the underlying SiO2 by orders of magnitude, independent of the concentration of ions in the surrounding biofluids. Accelerated tests that involve immersion in phosphate-buffered saline solution at a pH of 7.4 and under a constant electrical bias demonstrate that this bilayer barrier can also obstruct the transport of ions that would otherwise cause drifts in the operation of the electronics. Theoretical drift–diffusion modeling defines the coupling of dissolution and ion diffusion, including their effects on device lifetime. Demonstrations of such barriers with passive and active components in thin, flexible electronic test structures highlight the potential advantages for wide applications in chronic biointegrated devices.
Bibliographical noteFunding Information:
E.S., Y.K.L., R.L., and J.L. contributed equally to this work. This work was supported by Defense Advanced Research Projects Agency Contract HR0011-14-C-0102, and the Center for Bio-Integrated Electronics. The authors acknowledge the use of facilities in the Micro and Nanotechnology Laboratory for device fabrication and the Frederick Seitz Materials Research Laboratory for Advanced Science and Technology for device measurement at the University of Illinois at Urbana–Champaign. E.S. acknowledges support from China Scholarship Council. R.L. acknowledges the support from the Young Elite Scientist Sponsorship Program by China Association for Science and Technology (CAST). Z.X. acknowledges the support National Natural Science Foundation of China (Grant No. 11402134). Y.H. acknowledges the support from NSF (Grant Nos. DMR-1121262, CMMI-1400169, and CMMI-1534120) and the NIH (Grant No. R01EB019337). M.A. acknowledges the support from NSF Nano-biosensing Program Grant No. 1403582 and NSF NCNNEEDS Program under Grant No. 1227020-EEC.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics