The Fowler−Nordheim Plot Behavior and Mechanism of Field Electron Emission from ZnO Tetrapod Structures

Abstract

Field emission measurements of current-voltage characteristics are reported for tetrapod structures of ZnO. The nonlinear Fowler-Nordheim (FN) plot is analyzed according to a model of calculation based on saturation of conduction band current and predominance of valence band current at high-field values. The simulated FN plot exhibits similar features to those observed experimentally. The model of calculation suggests that the slope variation of the FN plot, in the high-field and low-field regions, does not depend on the magnitude of saturation. Instead, it is a characteristic of the energy band structure and voltage-to-barrier-field conversion factor of the emitting material.

Memristive behavior of Al2O3 film with bottom electrode surface modified by Ag nanoparticles

“…We can see that the I-V relation in LRS exhibits a linearly ohmic behavior with a slope of about one in the range from 0.04 to 0.45 V, which is regarded as the formation of conducting filaments in the device. The I-V relation in HRS can be expressed as ln (I/V 2 ) µ 1/V, which is consistent with Fowler-Nordheim (F-N) emission [29]. It indicates that HRS may be dominated by the interfaces between the electrode and dielectric layer, and the current is mostly coming from the charge tunneling.…”

Field emission in ordered arrays of ZnO nanowires prepared by nanosphere lithography and extended Fowler-Nordheim analyses

“…The slope value in the high-field regime is measured at À2702 V and is significantly reduced compared with its value in the low field regime. We observe that the transition between these regimes occurs gradually around a voltage of 2 kV over a range of about 150 V. We note that these two distinct regimes are also observed by Jeong et al 14 in the case of ZnO nanowires and Al-Tabbakh et al 19 in the ZnO tetrapods.…”

“…11, 14, 15, and 33 based on the 5.3 eV value. The choice of a work function of / ¼ 7:9 eV corresponding to electrons emitted from the top of the ZnO valence band 19 leads to even larger values of the enhancement factor and the surface field strength.…”

“…Jeong et al 14 suggested that the emission proceeds from deep-level defect states in the low field regime whereas the high field regime consists of electrons emitted from near the Fermi level. Al-Tabbakh et al 19 suggested that low-field emission in the conduction band ultimately saturates as the field is increased and leads to predominant emission from the valence band in the high field regime with a related increase in the work function value. More detailed investigations are needed to understand the importance of semiconductor effects in the FE of ZnO nanowires.…”

“…We recall here that most reports on the topic of FE assume the work function value / ¼ 5:3 eV for ZnO, irrespective of its morphology. 18 Al-Tabbakh et al have recorded IÀV data leading to highly non-linear FN plots for ZnO tetrapod nanostructures, 19 which they interpreted in terms of conduction band electrons or valence band currents at high field values due to the saturation of the conduction band current. It is apparent that the authors invoke differing electronic processes and work function values to explain the different results observed.…”