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Nitrogen-Mediated Wet-Chemical Formation of Carbon Nitride/ZnO Heterojunctions for Enhanced Field Emission

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journal contribution
posted on 20.04.2010, 00:00 by Kaushik Ghosh, Mukul Kumar, Huafeng Wang, Takahiro Maruyama, Yoshinori Ando
Heterojunction structures of nanocrystalline materials are of great importance in scientific and industrial research for their potential applications in nanoscale electronics and photonics. Here, we report a simple wet-chemical method of nitrogen-mediated growth of ZnO nanocrystals on carbon nitride (CNx) nanotubes. SEM and TEM analyses show self-organized ZnO nanoflowers on CNx stems. PL spectra exhibiting a blue emission at 449 nm confirms the junction formation between CNx and ZnO. The field emission (FE) properties of CNx-ZnO film are greatly improved over those of pristine CNx. The turn-on and threshold fields for bare CNx film are 1.70 and 2.95 V/μm, whereas those for CNx-ZnO hybrid are found to be 0.75 and 1.3 V/μm, respectively. This significant downshift in the turn-on and threshold fields is believed to occur via lowering of the Schottky barrier at the metal−semiconductor interface. Three-dimensionally blossomed ZnO nanopetals with multiple sharp tips effectively enhance the FE performance. Moreover, this heterojunction reinforces the electron emission lifetime and protects the CNx tubes against thermal degradation.