Synthesis of Crystalline ZnO Nanosheets on Graphene and Other Substrates at Ambient Conditions
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Synthesis of Crystalline ZnO Nanosheets on Graphene and Other Substrates at Ambient Conditions Phani Kiran Vabbina*a, Santanu Dasb, Nezih Palaa, Wonbong Choib a
Electrical & Computer Engineering Department, Florida International University, Miami, FL.
b
Mechanical and Materials Engineering, Florida International University, Miami, FL.
ABSTRACT We report on the fabrication of ZnO nanosheets on Graphene and other substrates at ambient conditions. The growth mechanism and the effect of the substrate are also discussed. Our synthesis method is based on sonochemical reaction of Zinc nitrate hexahydrate and hexamethylenetetramine in aqueous solutions. Extensive analysis by transmission electron microscopy, energy dispersive x-ray spectroscopy (EDS) revealed crystalline ZnO composition of the ZnO nanosheets. The proposed method is a rapid, inexpensive, low-temperature, catalystfree, CMOS compatible and environmentally benign alternative to existing growth techniques. INTRODUCTION Graphene has attracted a lot interest due to its unique electrical and optical properties. Growing oxides over graphene will provide additional functionality to graphene in electronic and optoelectronic applications. This will also enable us to integrate Graphene in semiconductors [2]. Zinc Oxide with its wide band gap of 3.37 eV, large exciton binding energy and high thermal stability has attracted wide research recently. ZnO nanostructures are expected to find applications in light emitting and detection devices in UV-visible spectral range, energy harvesting devices and in gas sensors. 2-D ZnO nanosheets with their large surface area and flat topography are among those nanostructures. ZnO nanosheets have been successfully synthesized by various methods such as vapor-solid and hydrothermal methods [9, 10]. However to be able to use in practical low cost electronic applications, these techniques are either not cost effective or the conditions are too harsh to give any flexibility for the growth on desired substrates. In this regard, we have recently reported on a sonochemical method which involves use of high intensity ultrasonic irradiation of an aqueous solution as an alternative method for the synthesis of ZnO nanowires and nanowalls [1]. Our method resulted in a ten times faster synthesis of ZnO nanostructures compared to the more conventional approaches such as hydrothermal synthesis, due to the fast hydrolysis rate caused by imploding cavitation bubbles [1] and does not require a seeding layer like previously reported sonochemical synthesis methods [5]. Here we report the synthesis of ultra-thin ZnO nanosheets on Graphene and other substrates by simple sonochemical method and present extensive crystallographic and surface and electrical studies by TEM, EDS, and AFM. With the advantages of being inexpensive, low-temperature, catalyst-free, CMOS compatible and environmentally benign, our reported method has the potential of being used for many electronic and photonic applications.
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EXPERIMENT: ZnO nanosheets were synthesized in a cu
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