Electrochemical Deposition of Manganese Oxides on Carbon Nanosheets
CNS was grown using RF-PECVD technique  onto both blanket 200 mm Si wafers coated with 70 nm thick PVD TiN, and wafer pieces with high-aspect-ratio Si pillars coated with 10 nm ALD TiN. CNS was grown on TiN from CH4/H2mixture  to a height of approximately 1 µm.
Anodic electrodeposition of Mn-oxide, often also termed electrolytic manganese-dioxide (EMD), was performed on both blanket CNS/TiN/Si and patterned CNS/ALD TiN/Si samples using 0.3 M MnSO4·xH2O + 0.55 M H2SO4aqueous electrolyte. Plating experiments were performed using a three-electrode clip-on Teflon cell connected to a computer controlled Autolab potentiostat PGSTAT100 (Metrohm), with Ag/AgCl as a reference electrode (RE) and Pt mesh as a counter electrode (CE). Characterization of EMD/CNS films was performed using Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy (RS), and X-ray photoelectron spectroscopy (XPS).
Figure 1 shows SEM images of as-grown CNS (a) and EMD coverage as a function of deposition current (b and c). EMD is plated galvanostatically, and potential-time responses were analyzed to help optimize deposition parameters for desired film thickness and structural properties. The analysis was based on the theories of galvanostatic nucleation and growth , and proposed reaction mechanisms during galvanostatic deposition of EMD . Further surface area enhancement was attempted through EMD/CNS deposition on HAR Si pillars coated with 10 nm ALD TiN. Figure 2 shows HAR ALD TiN/Si pillars before and after CNS and EMD deposition, respectively. CNS coating was applied to various ALD TiN/Si structures having different aspect ratios and spacing between pillars, and then followed by EMD deposition.
A typical Raman spectrum of our EMD/CNS structure, shown in Figure 3, contained broad features in the range 450 to 730 cm-1 where characteristic EMD peaks are expected [4 and references therein], and showed characteristic CNS peaks in 1000 to 3500 cm-1range .
Thanks to its sensitivity to local structure/symmetry Raman spectroscopy proved to be a useful tool for characterization of disordered and defective EMD. We were able to detect EMD structural changes upon annealing at various temperatures and lithiation in anhydrous propylene carbonate solvent with 1 M LiClO4, and also monitor the effects of plating and post-plating processing on CNS.
 D. J. Cott, M. Verheijen, O. Richard, I. Radu, S. De Gendt, S. van Elshocht, and P. M. Vereecken, Carbon, 58(2013), 59.
 A. Milchev and M.I. Montenegro, J. Electroanal. Chem., 333 (1992) 93.
 A. D. Cross, A. Morel, T. F. Hollenkamp, and S. W. Donnea, J. Electrochem. Soc., 158(2011), A1160.
 R. Baddour-Hadjean and J.-P. Pereira-Ramos, Chem. Rev., 110, (2010), 1278.
 S. Kurita, A. Yoshimura, H. Kawamoto, T. Uchida, K. Kojima, M. Tachibanaa, P. Molina-Morales and H. Nakai, Journal of Applied Physics, 97(2005), 104320.
Figure 1. SEM images of (a) as-received CNS, and Mn oxide anodically deposited on CNS at (b) 2.5 mA/cm2, and (c) 0.25 mA/cm2, from acidic sulfate solution.
Figure 2. (a) High aspect ratio ALD TiN/Si pillars after (b) CNS, and (c) EMD deposition.
Figure 3. Raman spectrum of Mn oxides plated on CNS at 2.5 mA/cm2 from acidic sulfate solution. EMD stands for electrolytic manganese dioxide. Characteristic CNS peaks are designated using capital letters.