Research Article Cite This: ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
www.acsami.org
ALD HfO2 Films for Defining Microelectrodes for Electrochemical Sensing and Other Applications Charmaine Chia,*,# Max M. Shulaker,§ J Provine,∥ Stefanie S. Jeffrey,‡ and Roger T. Howe# Department of Electrical Engineering and ‡Department of Surgery, Stanford University, Stanford, California 94305, United States § Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States ∥ Aligned Carbon, Inc., Santa Clara, California 95087, United States Downloaded via GUILFORD COLG on July 18, 2019 at 22:36:58 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.
#
S Supporting Information *
ABSTRACT: Microelectrodes are used in a wide range of applications from analytical electrochemistry and biomolecular sensing to in vivo implants. While a variety of insulating materials have been used to define the microelectrode active area, most are not suitable for nanoscale electrodes ( 5 μm2, tending toward a slope of 1, whereas at smaller areas, the gradient is closer to 0.5. An overlay of all the current versus area data is presented in Figure 11 below. Results from Section 3.2.1 from the Hnp100-Pp and Hnp350-Pp devices have also been included using (+) markers. Comparing the current magnitudes obtained from the
Figure 11. Aggregated data plotting the current magnitudes obtained from voltammograms against device electrode area exposed to electrolyte. Total theoretical steady-state current (iss) is plotted as pink and green dashed lines for the band and disk electrodes, respectively. H
DOI: 10.1021/acsami.9b06891 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
Research Article
ACS Applied Materials & Interfaces Hpxxx-Pp and Pp* devices, we observe that the former are generally lower, suggesting that the HfO2 layer reduces the current leakage from random parylene film defects. More importantly, the ultrathin HfO2 film allows us to define microelectrodes considerably smaller than the thickness of the parylene film (i.e.,
