Highly flexible and robust N-doped SiC nanoneedle field emitters

Abstract

Flexible field emission (FE) emitters, whose unique advantages are lightweight and conformable, promise to enable a wide range of technologies, such as roll-up flexible FE displays, e-papers and flexible light-emitting diodes. In this work, we demonstrate for the first time highly flexible SiC field emitters with low turn-on fields and excellent emission stabilities. n-Type SiC nanoneedles with ultra-sharp tips and tailored N-doping levels were synthesized via a catalyst-assisted pyrolysis process on carbon fabrics by controlling the gas mixture and cooling rate. The turn-on field, threshold field and current emission fluctuation of SiC nanoneedle emitters with an N-doping level of 7.58 at.% are 1.11 V μm − 1 , 1.55 V μm − 1 and 8.1%, respectively, suggesting the best overall performance for such flexible field emitters. Furthermore, characterization of the FE properties under repeated bending cycles and different bending states reveal that the SiC field emitters are mechanically and electrically robust with unprecedentedly high flexibility and stabilities. These findings underscore the importance of concurrent morphology and composition controls in nanomaterial synthesis and establish SiC nanoneedles as the most promising candidate for flexible FE applications. NPG Asia Materials (2015) 7, e157; doi:10.1038/am.2014.126; published online 23 January 2015 INTRODUCTIONFlexible electronic devices have attracted extensive attention in recent decades because of their numerous promising applications, such as flexible energy-storage devices, wearable energy-harvesting systems and stretchable electronics. 1-4 Among the emerging technologies, there is considerable interest in flexible field emission (FE) emitters due to their unique lightweight, conformable and flexible nature, which give them the significant advantage of being utilized in roll-up flexible FE displays, 3 e-papers 5 and high-performance X-ray tubes. 6 To enable such next-generation flexible devices, flexible cathodes must be used as the fundamental starting component to replace conventional emitters grown on rigid substrates. These flexible emitters should maintain their original or even better FE properties as well as excellent electrical and mechanical performances after bending, compressing, twisting and stretching. 7,8 To date, a variety of cathodes have been developed based on flexible substrates such as polymers, 9 graphene 7 and carbon fabrics. 10 However, material-and fabrication-related obstacles to the realization of high-performance flexible emitters remain.Silicon carbide (SiC) is an excellent material candidate for constructing advanced FE emitters. SiC is a third-generation wide band-gap semiconductor with excellent physical properties such as high strength and stiffness, high-temperature stability, corrosion resistance and high thermal conductivity. [11][12][13] To date, several studies have explored the FE properties of nanostructured SiC emitters

High performance field emission of silicon carbide nanowires and their applications in flexible field emission displays

“…The stable property of our SiC nanowire emitters fabricated by screen-printing is compatible with the SiC cathode by directly grown as well as other nanostructured cathodes previously reported. For example, it is found that the current fluctuations is 7.1% for the SiC convex geometries during the testing period of 1 hour, 37 14.1% for the n-type SiC nanoneedles under 200 • C during the testing period of 60 minutes, 38 and 18% for reduced graphene oxide (RGO) emitters during the testing period of 1 hour. 40 Stable devices are associated with excellent field emission performance.…”

Large‐scale growth of patterned SiC nanowire arrays and their field emission performance

“…In such unique configuration, the direction of the emitted electrons is always perpendicular to the anode surface (as presented in Figure C), which facilitates limiting the screening effect; (c) The tapered morphology of the attained SiC nanowire. The FE characteristics of the emitters could be effectively improved through controlling the growth of emitters that have both clear and sharp tips, for the improved local field enhancement effect; (d) The bamboo‐like body of the SiC nanowires, of which the sharp corners around the nanowire body are likely to play the role of effective electron emitting sites, as illustrated in Figure D.…”

“…There has been an extensive study of the field emission (FE) from nanostructured emitters in previous decades, for their potential use in the flat‐panel displays, high‐resolution electron‐beam instruments, electron microscopes, X‐ray tubes, etc . Among the field emitter communities, silicon carbide (SiC) has been proved as one of the pivotal and outstanding FE cathode candidates, for its low thermal‐shock resistance and thermal‐expansion coefficient, high electron mobility and low electron affinity, etc . In addition, SiC has excellent mechanical properties, high chemical stability, and thermal conductivity, which make it an ideal candidates for surviving harsh working conditions, for instance at high powers, high temperatures as well as high voltages .…”

“…In addition, SiC has excellent mechanical properties, high chemical stability, and thermal conductivity, which make it an ideal candidates for surviving harsh working conditions, for instance at high powers, high temperatures as well as high voltages . To date, there have been exploited numbers of nanostructured SiC FE cathodes ( eg, nanowires, nanorods, nanobelts, and nanoneedles), which shed light on their low turn‐on fields and stable current emissions …”

Extremely Stable Current Emission of P‐Doped SiC Flexible Field Emitters

“…The as‐synthesized SiCNPs field emitters possess much lower aspect ratio as compared to those of the 1D nanostructures often with a aspect ratio higher than 50. The current emission fluctuations are ≈±3.0%, ± 2.6%, ±2.5%, ±2.1%, and ±2.8%, as for the SiCNPs field emitters configured in flat state, convex bending with the radios of ≈1.2 and ≈0.4 cm, concave bending with the radios of ≈1.2 and ≈0.4 cm, which suggest the significant enhanced current emission stabilities as compared to those of ≈8.9%, 8.1%, and 7.1% responding to the concave, flat and convex states of the N‐doping SiC nanoneedles, respectively . It indicates that the stresses of the substrate caused by bending do not have significant effect on the current emission stabilities.…”