PDF Publication Title:
Text from PDF Page: 120
110 Graphene – Synthesis, Characterization, Properties and Applications Hf(NMe2)4 and H2O as presursors, without any postdeposition annealing. The relative dielectric constant of the stack was found to be about 16. A considerable mobility reduction to about 50% of the initial value was observed after the first 2-4 nm of metal oxide deposition. The mobility did not depend significantly on temperature in the range from 77 K to room temperature. This result suggests that phonon scattering did not play an essential role in the devices. Therefore the authors of this study speculated that influence of positively charged oxygen vacancies, ubiquitous in high-k dielectrics, was the main mobility limiting factor. 3.6 Polymer buffer layer for ALD of HfO2 on graphene Farmer et al. (2009) used a low-k polymer (NFC 1400-3CP) as a buffer layer for ALD of HfO2 on exfoliated graphene. This polymer is a derivative of polyhydroxystyrene that is commonly used in lithography. The polymer can be diluted in propylene glycol monomethyl ether acetate (PGMEA) and spin-coated on top of graphene. For deposition of HfO2, Farmer et al. used Hf(NMe2)4 and H2O as precursors and carried the ALD process out at 125 oC. The process yielded HfO2 films with a dielectric constant of about 13 on graphene. Farmer et al. also found that in order to produce continuous functionalization layer on graphene, a 24:1 dilution (by volume) of PGMEA/NFC is sufficient. Spinning of such a solution at a rate of 4000 rpm for 60 s results in a layer of about 10 nm in thickness. After curing the buffer layer at 175 oC for 5 min to remove residual solvent, a 10-nm thick HfO2 layer was deposited on top of that. The dielectric constant of the buffer layer was determined to be 2.4 which is a resonable value for this polymer. The receipe of Farmer et al. was also used by Lin et al. (2010) who demonstrated cutoff- frequency as high as 100 GHz for top-gated FETs based on wafer-scale epitaxial graphene made from SiC. This cut-off frequency exceeds that of Si metal-oxide semiconductor FETs of the same gate length (~40 GHz at 240 nm). The carrier mobilities were maintained between 900 to 1520 cm2/Vs across the 2-inch wafer. These values were largely the same as before the deposition of a top gate stack. (a) (b) (c) Fig. 12. (a) AFM image over an edge of a graphene flake on SiO2 after ALD of a 5 nm thick HfO2 (a) without and (b) with PVA. (c) Resistivity of a device after annealing and the PVA deposition as a function of back-gate bias (Adapted from Meric et al., 2011).PDF Image | GRAPHENE SYNTHESIS CHARACTERIZATION PROPERTIES
PDF Search Title:
GRAPHENE SYNTHESIS CHARACTERIZATION PROPERTIESOriginal File Name Searched:
Graphene-Synthesis.pdfDIY PDF Search: Google It | Yahoo | Bing
Salgenx Redox Flow Battery Technology: Power up your energy storage game with Salgenx Salt Water Battery. With its advanced technology, the flow battery provides reliable, scalable, and sustainable energy storage for utility-scale projects. Upgrade to a Salgenx flow battery today and take control of your energy future.
CONTACT TEL: 608-238-6001 Email: greg@infinityturbine.com (Standard Web Page)