Fabrication and Field‐Emission Properties of Large‐Area Nanostructures of the Organic Charge‐Transfer Complex Cu‐TCNAQ

Abstract

Low-dimensional semiconductors have attracted a great deal of attention owing to their promising uses in constructing functional nanometer-scale electronic and optoelectronic devices. [1][2][3][4][5] Metal-organic charge-transfer (CT) complexes are of growing interest because of their unique solid-state physical properties. [6][7][8] In particular, with well-defined architecture,CT complexes are showing prominent merits over their bulk counterparts for applications in electrical and optical memory devices, sensors, and magnetic devices. [9][10][11] Many researchers therefore launched studies on the controllable synthesis of CT complexes. Tetracyanoquinodimethane (TCNQ)-based solidstate chemistry represents an area of considerable current interest in the field of materials science. [12][13][14] Although successful attempts to impart TCNQ-based CT complexes devices with high-quality performance, a sparsely investigate avenue for development is the exploration of materials based on other acceptors, [15][16][17] which may significantly enhanced the understanding of their intriguing physical and chemical, such as electronic, magnetic and optic, behavior. Tetracyanoanthraquinodimethane (TCNAQ; see Scheme S1 in the Supporting Information) shows more efficient electron-acceptor properties than TCNQ and has been extensively studied in conjugated polymers. [18,19] . However, studies on CT complexes based on TCNAQ are seldom reported.An active area of research has been the synthesis and fabrication of low-dimensional organic semiconductors for applications in field-emission cold cathodes. [20][21][22][23][24] Recently, we reported the field-emission properties of metal-organic chargetransfer complexes of Cu-TCNQ and Ag-TCNQ nanostructure arrays. Both the outstanding current density and the low turn-on field showed great potential for applications of organic charge-transfer complexes in field-emission flat displays.[23]These results encouraged us to fabricate new structures of metal-organic charge-transfer complexes for applications in further field emitters. Herein, we would like to report the facile fabrication of Cu-TCNAQ complexes on the nanometer scale. Controllable synthesis of large-area nanostructured Cu-TCNAQ films has been easily achieved. Field-emission measurements show that the Cu-TCNAQ complex is a potential candidate for field-emission cathodes. Figure 1 displays photographs of the large-area Cu-TCNAQ synthesized in acetonitrile (Fig. 1a) and acetone (Fig. 1b) solution. Figure 2a-b show the typical morphology as the reaction was performed in TCNAQ of acetonitrile solution. The nanowire film was grown on the copper foil after reaction for about 5 min in 1 mg mL -1 TCNAQ acetonitrile solution at room temperature. From Figure 2a, it can be seen that the nanowires with flexible shape are mostly lying down on the substrate. The high-magnification image (Fig. 2b) shows that the nanowires are entangled with each other. The nanowire is about 100 nm in diameter and several microme-

Experimental and theoretical investigation of enhanced cold cathode emission by plasma-etched 3d array of nanotips derived from CuPc nanotube

“…The eld emission characteristics are shown in the Fig. [10][11][12][13][14][21][22][23][24][25][26] These values are also comparable various tube like eld emitter such as B-C-N microtube, Fe doped TiO 2 nanotube, ZnO nanotubes, boron nanotubes and carbon nanotubes. The turn-on eld and threshold eld in the case of CuPc nanotube was obtained 6.8 and 8.4 V mm À1 respectively, which get down-shied to 4.2 and 6.5 V mm À1 for the P-CuPc nanotips respectively.…”

“…Inspired by this speculated array of exciting features, several groups have focused their attentions to design excellent cold cathode emitting materials. Field emission properties of others kind of organic nanostructures such as CuTCNQ (TCNQ ¼ tetracyanoquinodimethane) nanotube, Cu-TCNAQ (TCNAQ ¼ tetracyanoanthraquinodimethane) nanowires, CuTCNQ nanorod, Alq3{Tris(8-hydroxyquinoline)-aluminium} nanowires, PTCDA (3,4,9,10- 17,[21][22][23][24][25][26] Even then until now there is no report in the literature on high quality, uniform 3D out of plane nanotips arrays over a base morphology where both materials acts as a eld emitter and there are few reports of organic eld emitters which have turn-on eld less than $5 V mm À1 (dened current density@10 mA cm À2 ). Such inorganic nanostructures, in spite of their excellent eld emission characteristics, possess several drawbacks such as high temperature processing and expensive deposition system.…”

Self-assembly low dimensional inorganic/organic heterojunction nanomaterials

“…Under the certain temperature, 7,7,8,8-tetracyanoquinodimethane (TCNQ) powder could be gasified and react with cooper film to generate CuTCNQ complexes (Figure 7(a) -(d)) [47][48][49][50]. Through controlling the concentrations of TCNQ vapor, two kinds of morphologies of CuTCNQ complexes, nanowire and nanotube, could be fabricated (Figure 7(e) and (f)) [51].…”

“…CuTCNQ and AgTCNQ nanowires are very promising field emission cathode materials which have smaller work function, even than carbon materials such as graphene. Through changing the growth condition, the CuTCNQ nanowall [49] and nanotube [51] arrays were also fabricated. Their turn on fields were 8 and 12.2 V μm 1 and the largest emission current density were 10.9 and 7.15 mA cm 2 .…”

Organic crystallizable solvent served as template for constructing well-ordered PPE films

“…The preparation of patterned films has drawing extensive attention during the past decades, and scientists have developed many patterning technologies to manipulate the morphology of well-patterned inorganic, organic and polymer films. The patterned nanostructures of organic charge-transfer complexes were synthesized by chemical vapor deposition [6,7]; the high-throughout and high-resolution patterns were prepared by nanoimprint lithography [8]; tailed domain orientation of polymer films were fabricated by using magnetic field [9], electric field [10,11], templated methods [12,13] and so on [14,15]. Among these methods, great efforts have been dedicated in investigation of patterned polymer films obtained from the microphase separation in block copolymers [16][17][18][19][20].…”