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.

FIELD DESORPTION MICROSCOPY OF CARBON-COATED FIELD ELECTRON EMITTERS

Полевые электронные эмиттеры в форме металлического острия с пленкой углерода на поверхности обладают рядом перспективных эксплуатационных свойств. Характеристики эмиттера зависят от фазового состава, толщины и однородности пленки. Определение параметров пленок толщиной в один или несколько моноатомных слоев представляет определённые трудности. В данной работе образование и характеристики углеродных наноструктур на поверхности полевых эмиттеров из иридия и рения исследуются с помощью полевой десорбционной микроскопии непрерывного режима. На полевых десорбционных изображениях области углеродных наноструктур проявляются в виде локальных вспышек (лавинообразная десорбция). При покадровом анализе видеозаписей вспышек обнаружено несколько стадий формирования вспышек и выявлены различия в протекании десорбции с углеродных наноструктур на иридии и на рении. Обнаруженные различия объясняются образованием на иридии однослойного, а на рении многослойного графена. Десорбционные изображения выявляют неоднородности и локальные различия толщины пленки. Показано, что полевая десорбционная микроскопия непрерывного режима позволяет определять закономерности формирования полевых десорбционных изображений различных углеродных наноструктур, в частности, однослойного и многослойного графена на поверхности полевого эмиттера, и проводить диагностику поверхности после науглероживания и контролировать однородность получаемого покрытия. Получаемые данные полезны для разработки технологии эффективных полевых электронных эмиттеров. Field electron emitters in the form of a metal tip with a carbon film on the surface have a number of promising operational properties. The characteristics of the emitter depend on the phase composition, thickness and uniformity of the film. Determining the parameters of films with a thickness of one or more monoatomic layers presents certain difficulties. In this paper, the formation and characteristics of carbon nanostructures on the surface of field emitters made of iridium and rhenium are studied using continuous-mode field desorption microscopy. In the field desorption images, the regions of carbon nanostructures appear as local flashes (avalanche-like desorption). Frame-by-frame analysis of flash video recordings revealed several stages of the flash formation and revealed differences in the desorption from carbon nanostructures on iridium and rhenium. The found differences are explained by formation of the single-layer graphene on iridium and a multilayer graphene on rhenium. Desorption images reveal inhomogeneities and local differences in the film thickness. It is shown that continuous-mode field desorption microscopy makes it possible to determine the regularities of formation of the field desorption images of various carbon nanostructures, in particular, the single-layer and multilayer graphene on the surface of the field emitter, and to diagnose the surface after carburization. Besides, control the uniformity of the resulting coating is possible. The obtained data are useful for developing technology of the effective field electronic emitters.

Low-Field Electron Emission Capability of Thin Films on Flat Silicon Substrates: Experiments with Mo and General Model for Refractory Metals and Carbon

Herein, we describe a study of the phenomenon of field-induced electron emission from thin films deposited on flat Si substrates. Films of Mo with an effective thickness of 6–10 nm showed room-temperature low-field emissivity; a 100 nA current was extracted at macroscopic field magnitudes as low as 1.4–3.7 V/μm. This result was achieved after formation treatment of the samples by combined action of elevated temperatures (100–600 °C) and the electric field. Morphology of the films was assessed by AFM, SEM, and STM/STS methods before and after the emission tests. The images showed that forming treatment and emission experiments resulted in the appearance of numerous defects at the initially continuous and smooth films; in some regions, the Mo layer was found to consist of separate nanosized islets. Film structure reconstruction (dewetting) was apparently induced by emission-related factors, such as local heating and/or ion irradiation. These results were compared with our previous data obtained in experiments with carbon islet films of similar average thickness deposited onto identical substrates. On this basis, we suggest a novel model of emission mechanism that might be common for thin films of carbon and refractory metals. The model combines elements of the well-known patch field, multiple barriers, and thermoelectric models of low-macroscopic-field electron emission from electrically nanostructured heterogeneous materials.

Gravitational Field and Mass

It is extremely fascinating and astonishing that the gravitational field on the surface of a neutron star is with a relativistic mass density of 2.65*1016~5.87*1018kgm-3 which can be larger than the mass density of the neutron star (~1017kgm-3).Therefore, it is the author’s first intuitional imagining that this field could directly convert into mass. In so strong a gravitational field, electron and proton could be produced directly from graviton–photon collision. The gravitational field exists in everywhere in our universe. No vacuum that the region of a space is “empty” does exist. A particle is clearly always being acted on by the gravitational field. The quantum vacuum fluctuation and vacuum polarization need be re-understood with the interaction between photon and gravitational field. Therefore, the gravitational field is naturally one of the foundations of modern physics.

Investigation of changes in field electron emission characteristics of industrial fine-grained graphite when operated in an argon atmosphere up to 10–2 Pa

Studying of field electron emission properties of carbon cathodes operating under technical vacuum conditions is a promising scientific field. Massive cathode made of commercial fine-grained graphite of MG (Russian abbreviation) grade is being investigated. Experiments on obtaining current-voltage characteristics and long-term testing are being carried out. The emitter made of fine-grained graphite demonstrates good emission properties under technical vacuum conditions. Carbon cathode is capable of operating at pressures up to 2×10–2 Pa. Increased pressure in the vacuum chamber leads to deterioration of cathode emission properties. Electric field enhancement factors were calculated for all stages of studies. Analysis of experimental data demonstrates decrease in enhancement factor due to ion bombardment of cathode surface during exploitation. This results in higher electric field for operation of investigated graphite cold cathodes.