Effects of gas exposure on the field-emission properties of ZnO nanorods

Kim, Do-Hyung; Jang, Hee‐Seong; Lee, Sung-Youp; Lee, Hyeong-Rag

doi:10.1088/0957-4484/15/11/008

Cited by 26 publications

(12 citation statements)

References 15 publications

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“…ZnO with various morphologies such as nanowires, nanorods, nanobelts, nanotubes and nanotetrapods [9][10][11] have been prepared by a number of methods. Recent examples of the utilization of ZnO nanorods are found in hybrid and dye-sensitized solar cells, field-emitting cathodes, chemical sensors, lowvoltage and short-wavelength electro-optical devices such as light emitting diodes and diode lasers, surface acoustic wave filters and varistors [12][13][14][15][16][17][18], etc. ZnO is a potential sensor of NH 3 and a photocatalyst to reduce the emission of NO x .…”

Section: Introductionmentioning

confidence: 99%

Surfactant free hydrothermally derived ZnO nanowires, nanorods, microrods and their characterization

Nagaraju

Ashoka

Chithaiah

et al. 2010

Materials Science in Semiconductor Processing

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a b s t r a c tZnO nanowires, nanorods and microrods have been prepared by an organic-free hydrothermal process using ZnSO 4 and NaOH/NH 4 OH solutions. The powder X-ray diffraction (PXRD) patterns reveal that the ZnO nano/microrods are of hexagonal wurtzite structure. The Fourier transform infrared (FT-IR) spectrum of ZnO powder shows only one significant spectroscopic band at around 417 cm À 1 associated with the characteristic vibrational mode of Zn-O bonding. The thickness 75-300 nm for ZnO nanorods and 0.2-1.8 mm for microrods are identified from SEM/TEM images.UV-visible absorption spectra of ZnO nano/microrods show the blue shift. The UV band and green emission observed in photoluminescence (PL) spectra are due to free exciton emission and singly ionized oxygen vacancy in ZnO. Finally, the mechanism for organicfree hydrothermal synthesis of the ZnO nano/microrods is discussed.

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Section: Introductionmentioning

confidence: 99%

Surfactant free hydrothermally derived ZnO nanowires, nanorods, microrods and their characterization

Nagaraju

Ashoka

Chithaiah

et al. 2010

Materials Science in Semiconductor Processing

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“…This factor is a material-related one; however, that does not mean it is a fixed number. For example, the reported work function for carbon emitters ranges from 1 to 12 eV, and there is also evidence that the work function of the emitters can be varied in a large range by annealing in different atmospheres. , Furthermore, improved field emission performances of ZnO nanorods can also be achieved by lowering the work function through doping or coupling with other materials. − Accordingly, we adopted two alternative approaches to improve the field emission performances of the ZnO nanorods arrays. The first one is to decrease the tip radius of ZnO nanorods by controlling the growth processes, and the second one is to lower the work function of ZnO by modifying it with metal particles with a smaller work function.…”

Section: Introductionmentioning

confidence: 99%

Enhanced Field Emission Performance of ZnO Nanorods by Two Alternative Approaches

Ye,

Bando,

Fang

et al. 2007

J. Phys. Chem. C

121

124

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Standard ZnO nanorods with a diameter of ∼150 nm show poor field emission performance. In an attempt to dramatically improve the field emission properties, we developed two alternative methods: The first one is to decrease the tip radius of nanorods down to ∼5 nm. The second one is to decorate the nanorods by small metal particles. By either of these two approaches, we can obtain excellent field emission performances, typically turn-on field (the electric field at which the current density reaches 10 µA/cm 2 ) as small as 2 V/µm and current density as large as 1 mA/cm 2 can be readily achieved. The physical essence of the excellent performances is the geometrically enhanced local field near the tip of the nanorods and the lowered work function of ZnO nanorods by the donation of electrons from the nanoparticles.

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“…These diŠerences were mainly due to the interaction between the diŠerent cathode materials and the ambient gases during the fabrication or operation processes of the device. In the CNT-FE device, where carbon was abundant-due to the disassociation of the CNTs or non-graphitic carbon in the CNT paste, or the evaporation of the CNTs during electron emission 19) -chemical reactions between C and CO 2 or O 2 would have led to increases in the amount of CO in the device using a CNT cathode. This would have resulted in an absence of CO 2 in the CNT-FE devices.…”

Section: Resultsmentioning

confidence: 99%

Residual Gas Components and Their Effect on Field Emission Devices with Nanoscale Emitters

et al. 2015

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The emission currents of zinc oxide (ZnO) and carbon nanotube (CNT) cold cathodes show continuous degradation in sealed eld emission (FE) devices when the anode voltages are maintained at a constant value; more stable currents are observed when the same cathodes are operated under ultra-high vacuum (UHV) conditions. This shows that ambient gases in the devices play an important role in degrading the emission currents of ZnO and CNT cathodes. To investigate the gas conditions in sealed FE devices, a vacuum system with a quadrupole mass spectrometer (QMS) was employed here. QMS data obtained before and after the gases in the FE devices were removed showed that the residual gases in the CNT-FE panels were H 2 , CH 4 , CO, and Ar, while in the ZnO-FE panels the residual gases were H 2 , CH 4 , CO, Ar, and CO 2 . It was clear that the residual gases in the two kinds of FE devices were slightly diŠerent; this was mainly due to the diŠerent cathode materials used in the FE devices. The residual gases aŠected the emission current of the CNT and ZnO FE devices by changing the work function at the cathode surface; this was conˆrmed by the F-N curves measured when the same cathodes were tested in the devices and in the UHV chamber.

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Effects of gas exposure on the field-emission properties of ZnO nanorods

Cited by 26 publications

References 15 publications

Surfactant free hydrothermally derived ZnO nanowires, nanorods, microrods and their characterization

Surfactant free hydrothermally derived ZnO nanowires, nanorods, microrods and their characterization

Enhanced Field Emission Performance of ZnO Nanorods by Two Alternative Approaches

Residual Gas Components and Their Effect on Field Emission Devices with Nanoscale Emitters

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