FIELD DESORPTION OF INTERCALATED CAESIUM ATOMS FROM GRAPHENE ON THE (100) IRIDIUM FACE

С помощью полевой десорбционной микроскопии исследована десорбция атомов цезия с квазисферической науглероженной поверхности монокристалла иридия. Получены полевые электронные и десорбционные изображения поверхности при образовании графена на грани (100) иридия. Полевые электронные изображения поверхности эмиттера до интеркалирования и после интеркалирования графена атомами цезия не изменяются. Электрическое поле стимулирует десорбцию атомов цезия из интеркалированного состояния, вследствие разрыва связей крайних атомов углерода с поверхностью грани (100) иридия. С помощью покадровой регистрации показана возможность наблюдения локализации дефектов графенового слоя на поверхности полевого эмиттера. Показано, что полевая десорбция атомов цезия из интеркалированного состояния начинается с дефектов графена расположенных по периметру островка графена. Обнаружено, что десорбционные центры могут располагаться не только по периметру графенового островка, но и в центральной его части в случае образования неупорядоченного графена. The desorption of caesium atoms from the quasi-spherical carbonized surface of an iridium single crystal was studied using the field desorption microscopy. Field electron and desorption images of the surface during the formation of graphene on the (100) iridium face are obtained. The field electron images of the emitter surface before intercalation and after intercalation of graphene with caesium atoms do not change. The electric field stimulates the desorption of caesium atoms from the intercalated state, due to the breaking of the bonds of the extreme carbon atoms with the surface of the face (100) of iridium. Using frame-by-frame recording, the possibility is shown of observing the localization of graphene layer defects on the surface of the field emitter. It is also shown that the field desorption of caesium atoms from the intercalated state begins with graphene defects located along the perimeter of the graphene island. It is found that desorption centers can be located not only along the perimeter of the graphene island, but also in its central part in the case of the disordered graphene formation.

Nanocone-Shaped Carbon Nanotubes Field-Emitter Array Fabricated by Laser Ablation

The nanocone-shaped carbon nanotubes field-emitter array (NCNA) is a near-ideal field-emitter array that combines the advantages of geometry and material. In contrast to previous methods of field-emitter array, laser ablation is a low-cost and clean method that does not require any photolithography or wet chemistry. However, nanocone shapes are hard to achieve through laser ablation due to the micrometer-scale focusing spot. Here, we develop an ultraviolet (UV) laser beam patterning technique that is capable of reliably realizing NCNA with a cone-tip radius of ≈300 nm, utilizing optimized beam focusing and unique carbon nanotube–light interaction properties. The patterned array provided smaller turn-on fields (reduced from 2.6 to 1.6 V/μm) in emitters and supported a higher (increased from 10 to 140 mA/cm2) and more stable emission than their unpatterned counterparts. The present technique may be widely applied in the fabrication of high-performance CNTs field-emitter arrays.

Stable Field Emission from Vertically Oriented SiC Nanoarrays

Silicon carbide (SiC) nanostructure is a type of promising field emitter due to high breakdown field strength, high thermal conductivity, low electron affinity, and high electron mobility. However, the fabrication of the SiC nanotips array is difficult due to its chemical inertness. Here we report a simple, industry-familiar reactive ion etching to fabricate well-aligned, vertically orientated SiC nanoarrays on 4H-SiC wafers. The as-synthesized nanoarrays had tapered base angles >60°, and were vertically oriented with a high packing density >107 mm−2 and high-aspect ratios of approximately 35. As a result of its high geometry uniformity—5% length variation and 10% diameter variation, the field emitter array showed typical turn-on fields of 4.3 V μm−1 and a high field-enhancement factor of ~1260. The 8 h current emission stability displayed a mean current fluctuation of 1.9 ± 1%, revealing excellent current emission stability. The as-synthesized emitters demonstrate competitive emission performance that highlights their potential in a variety of vacuum electronics applications. This study provides a new route to realizing scalable field electron emitter production.