Effective large-area free-standing graphene field emitters by electrophoretic deposition

Abstract

Large area graphene field emitters were fabricated using electrophoretic deposition. By varying the deposition time, we were able to fabricate emitters with varied field enhancement factors. The turn-on field increased when the deposition time increased, and it was observed that a monolayer of graphene flakes covered on the substrate gave the best results. The low emission turn-on field obtained from the graphene field emitters was attributed to the random orientation of graphene flakes which give protruded edges that acted as field enhancing spots. Graphene emitters produced by this method present a low cost cold cathode that can be mass produced.

Electrophoretic deposition of graphene-related materials: A review of the fundamentals

“…Most of the studies [15,29,49,71,119,144,147,153,154] have reported that electrophoretically deposited GRM sheets lie parallel to the surface of their underlying electrode which produce a flat surface morphology. However, several studies [39,68,91,103,105,106,136,146,155,156] have reported the EPD of GRM sheets to occur with a perpendicular or random orientation to the electrode surface, leading to a rough surface with protruding graphene edges. Orientation may relate to dynamic effects during electrophoresis, including specific effects of charging salts (see Section 6.2 (v)), but is probably also strongly influenced by capillary effects during drying, and hence, the solvent surface tension and drying method.…”

“…For example, electrodes for electrochemical double layer supercapacitors rely on high structural porosity as well as a large interlayer separation of GRM sheets to allow effective electrolyte access and to maximise the active surface area for charge storage [15,63,96,124,143]. On the other hand, field emission of electrons at low voltages requires a high surface roughness and a predominance of well distributed, individualised GRM edges [39,85,91,92,101,[144][145][146]. In contrast, a low surface roughness and high film bulk density are favoured for solid lubricant coatings [76] or barrier layers.…”

“…However, high concentrations of these ions can destabilize the suspensions, whilst, their electrophoresis and accumulation on the electrode's surface can have negative effects on the deposition of the desired GRM [90] as described in Section 5. iv. Typical metal salts that are used for charging GRM for EPD are nitrates of aluminium [91][92][93][94], nickel [95][96][97], zinc [98], cobalt [99], manganese [63,100], magnesium [17,20,31,39,68,85,86,[101][102][103][104][105][106][107][108] and magnesium chloride [109], although, copper sulfate has been used recently [110]. The performance of these ions, however, may be pH dependent.…”

Plasma engineering of graphene

“…Some of the properties of graphene such as high aspect ratio, presence of abundant edges along with its excellent conductivity make it an ideal candidate for use in fuel cell 66,126 , Li-ion batteries 65,127,128 , supercapacitor 90,91 and field emission sources 131,132 .…”

Field emission performance enhancement of Au nanoparticles doped graphene emitters

“…4,5 Electrophoretic deposition (EPD) is an economical and versatile processing technique that has been applied in deposition of films in recent years. [6][7][8][9] Wu et al had prepared GP emitters with EPD and compared it to emitters made by directly coating GP powder onto conductive tape, thus proving the effectiveness of EPD for field emission applications. 6 Koh fabricated large area GP field emitters using EPD and obtained the low turn on field emitters with varied field enhancement factors.…”