Elsevier

Applied Surface Science

Volume 256, Issue 9, 15 February 2010, Pages 2764-2768
Applied Surface Science

Enhanced field emission and patterned emitter device fabrication of metal-tetracyanoquinodimethane nanowires array

https://doi.org/10.1016/j.apsusc.2009.11.025Get rights and content

Abstract

Ag(TCNQ) and Cu(TCNQ) nanowires were synthesized via vapor-transport reaction method at a low temperature of 100 °C. Field emission properties of the as-obtained nanowires on ITO glass substrates were studied. The turn-on electric fields of Ag(TCNQ) and Cu(TCNQ) nanowires were 9.7 and 7.6 V/μm (with emission current of 10 μA/cm2), respectively. The turn-on electric fields of Ag(TCNQ) and Cu(TCNQ) nanowires decreased to 6 and 2.2 V/μm, and the emission current densities increased by two orders at a field of 8 V/μm with a homogeneous-like metal (e.g. Cu for Cu(TCNQ)) buffer layer to the substrate. The improved field emission is due to the better conduct in the nanowires/substrate interface and higher internal conductance of the nanowires. The patterned field emission cathode was then fabricated by localized growing M-TCNQ nanowires onto mask-deposited metal film buffer layer. The emission luminance was measured to be 810 cd/m2 at a field of 8.5 V/μm.

Introduction

Over the past few years, one dimensional (1D) nanostructures have been considered as promising field emitters to fabricate field emission displays (FEDs) because of their high enhancement factor owing to the sharp tips and high aspect ratios [1]. Among them, carbon nanotubes (CNTs) [2], [3], [4] have obviously attracted the most attention due to their high aspect ratio and conductivity. These years, metal oxide 1D nanostructures such as ZnO [5], WO3 [6] and CuO [7] have been considered as appropriate alternatives to CNTs for field emission (FE) microelectronic devices owing to their higher thermal and chemical stability and negative electron affinity. However, the synthesis of these nanostructures all requires high-temperature treatments as described in Table 1, which is not conducive to the emission cathode fabrication and FE device packaging. Therefore, it is essential to seek low-temperature-synthesized emission material and to develop convenient counterpart cathode fabrications, which are curial for FE microelectronic device application.

The 1D nanostructures of metal-tetracyanoquinodimethane (M-TCNQ) charge transfer complexes attracted increasingly interests for potential application in functional nano-scaled electronic devices due to their high densities of charge carriers and field-induced electrical switching properties [8], [9], [10], [11]. Recently, studies have revealed that M-TCNQ (e.g., Ag-TCNQ and Cu-TCNQ) nanostructures grown on Ag/Cu foils by organic vapor–solid-phase reaction at 150 °C have low emission turn-on field and mA/cm2 order emission current density [12]. However, the research on FE device application of M-TCNQ nanowires including electrode patterning and substrate facilitating is still insufficient and necessary.

In this paper, Ag(TCNQ) and Cu(TCNQ) nanowires were produced via an undemanding vapor-transport reaction method at a temperature of 100 °C. The field emission properties of as-obtained nanowires were studied. Furthermore, a structure consisting of M-TCNQ nanowires/Metal thin film/ITO glasses was employed in order to reduce the emission threshold field and enhance the emission current. Field emitter device was then fabricated utilizing this structure. The emission fluorescence experiment afterwards indicates that M-TCNQ 1D nanostructures are promising candidates for field emission display (FED) cathode materials.

Section snippets

Experimental

Horizontal oriented M-TCNQ nanowires arrays were synthesized via a vapor-transport reaction method we developed in previous work [13]. A 10 nm thick Cu or Ag film was pre-deposited on the ITO glass substrate by thermal evaporation. Afterwards the substrate together with TCNQ powder (98% Aldrich) was placed in a glass tube connected to a vacuum chamber. After pumped down to 2 × 10−3 Pa, the tube was sealed and thermal treated in a furnace at 100 °C for 1 h. Consequently, the substrate was covered with

Results and discussion

The morphologies of as-prepared M-TCNQ nanowires are shown in Fig. 1. The typical diameters of nanowires ranged from 50 to 200 nm, which was determined by the thickness of the pre-cursor metal film. It can be seen that Ag(TCNQ) nanowires were straight and rigid rod-like (Fig. 1a and b) while Cu(TCNQ) nanowires were bendy and flexible (Fig. 1c and d). The growth of M-TCNQ nanowires conformed to a vapor–liquid–solid mechanism as was discussed in our previous work [13]. During the growth, the metal

Acknowledgements

The authors acknowledge financial support from Shanghai Science and Technology Development Fund (No. 09DZ1142102 and No. 0752nm016) and Shanghai Leading Academic discipline Project (No. B113).

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