The results of studying the electronic states of the conduction band of ultrathin films of furan-phenylene co-oligomer 1,4-bis(5-phenylfuran-2-yl)benzene and the results of analyzing the interfacial potential barrier upon the formation of these films on the surfaces of (SiO2)n-Si and layer-by-layer deposited ZnO are presented. The formation of a (8–10)-nm-thick co-oligomer film was investigated by total current spectroscopy; the energy range from 5 to 20 eV above EF was analyzed. Furan-phenylene co-oligomer films on the (SiO2)n-Si surface have a domain structure with a characteristic domain size of 1 × 1 µm and surface roughness within a domain of no more than 1 nm. The films on the ZnO surface have a granular structure with a grain height of 40–50 nm.

The surface topography and density of unoccupied electronic states at thermal deposition of ultrathin dibromo-bianthracene films on the ZnO surface have been studied. The electronic characteristics of unoccupied electronic states during growth of dibromo-bianthracene films to a thickness of 10 nm have been investigated by total current spectroscopy using a probe electron beam. The experimental dependences have been analyzed using theoretical calculation of the orbital energies for dibromo-bianthracene molecules by the method of density functional theory (DFT).

Приведены результаты исследования топографии поверхности и плотности незаполненных электронных состояний при термическом осаждении сверхтонких пленок дибромо-биантрацена на поверхность ZnO. Измерения электронных характеристик незаполненных электронных состояний в процессе роста пленок дибромо-биантрацена до толщины 10 нм проводили методом спектроскопии полного тока с использованием тестирующего электронного пучка. Анализ экспериментальных зависимостей проводили с использованием теоретического расчета энергий орбиталей молекул дибромо-биантрацена методом теории функционала плотности.

The results of a study of the unoccupied electronic states of ultrathin films of phenolphthalein molecules on a ZnO surface formed by atomic layer deposition technique are presented. The atomic composition of the ZnO layer was determined by X-ray photoelectron spectroscopy (XPS) and its crystallinity was characterized using X-ray diffraction. The predominance of the content of O atoms by 5-10%, compared with the content of Zn atoms, was found. The electronic characteristics of the ZnO/phenolphthalein structure were studied using total current spectroscopy (TCS) in the energy range from 5 eV to 20 eV above EF during thermal vacuum deposition of phenolphthalein films up to 8 nm thick. Phenolphthalein molecules contain two hydroxyl functional groups. The TCS results on the phenolphthalein films are compared with the TCS results obtained from films of molecules that represent the backbone of phenolphthalein molecules without hydroxyl groups. The TCS fine structure maxima of phenolphthalein films located in the energy range from 5 eV to 8 eV above EF can be associated with the boundaries of the p* bands of electronic states. The work function of the ZnO surface formed by the ALD method were 4.2±0.1 eV. The deposition of a phenolphthalein film led to a decrease in the work function of the surface by 0.1 eV.

The results of a study of the unoccupied electronic states of ultrathin films of phenolphthalein molecules on a ZnO surface formed by atomic layer deposition technique are presented. The atomic composition of the ZnO layer was determined by X-ray photoelectron spectroscopy (XPS) and its crystallinity was characterized using X-ray diffraction. The predominance of the content of O atoms by 5-10%, compared with the content of Zn atoms, was found. The electronic characteristics of the ZnO/phenolphthalein structure were studied using total current spectroscopy (TCS) in the energy range from 5 eV to 20 eV above EF during thermal vacuum deposition of phenolphthalein films up to 8 nm thick. Phenolphthalein molecules contain two hydroxyl functional groups. The TCS results on the phenolphthalein films are compared with the TCS results obtained from films of molecules that represent the backbone of phenolphthalein molecules without hydroxyl groups. The TCS fine structure maxima of phenolphthalein films located in the energy range from 5 eV to 8 eV above EF can be associated with the boundaries of the π* bands of electronic states. The work function of the ZnO surface formed by the ALD method were 4.2±0.1 eV. The deposition of a phenolphthalein film led to a decrease in the work function of the surface by 0.1 eV. Keywords: Phenolphthalein, ultrathin films, ZnO, atomic layer deposition, electronic properties, low-energy electron spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy.

The results of studying the electronic states of the conduction band and interface potential barrier during the formation of ultrathin films of thiophene-phenylene co-oligomer CH3-phenylene-thiophene-thiophene-phenylene-CH3 (CH3-PTTP-CH3) on the surface of ZnO and films of biphenyl tetracarboxylic dianhydride (BPDA) on the ZnO surface are presented. A 100 nm thick ZnO layer was prepared by atomic layer deposition (ALD). Organic CH3-PTTP-CH3 films and BPDA films up to 8 nm thick were formed by thermal vacuum deposition. During film deposition, the electronic characteristics of the surface were studied using total current spectroscopy (TCS) in the energy range from 5 eV to 20 eV above EF. In this energy range, the structure of the maxima of the unoccupied electronic states of CH3-PTTP-CH3 and BPDA films was determined. As a result of the CH3-PTTP-CH3 film deposition, a decrease in the work function to 4.0 eV was found, compared with the value of the work function of 4.2 eV measured from the ALD ZnO substrate. This corresponds to the transfer of a negative charge from the СH3-PTTP-CH3 film to the substrate. The charge transfer at the interface between the BPDA film and the ALD ZnO substrate occurs in the opposite direction, since a 4.7 eV increase of the work function was registered during the formation of this interface. The СH3-PTTP-СH3 and BPDA films studied and the layer-by-layer grown ZnO film represent a continuous coating on sufficiently large surface areas of the order of 10 micrometers x 10 micrometers. The roughness of the ZnO surface does not exceed 4 nm, and the surface roughness of CH3-PTTP-CH3 and BPDA films was 10–15 nm.

This work is devoted to an experimental investigation of the electronic structure of the surface of topological insulators of various stoichiometry during the adsorption of Co atoms. Changes in the surface electronic structure of Bi2Te3 and MnBi2Te4 systems upon deposition of Co atoms at various temperatures have been studied using the methods of angle-resolved photoemission spectroscopy, as well as X-ray photoelectron spectroscopy. It is suggested that binding of the adsorbed Co atoms to the substrate surface modifies Dirac point position. The observed changes are associated with the possible formation of magnetic Co-containing ordered surface alloys.

Investigation of graphene on an ultrathin CoSi/CoSi2 cobalt silicide layer on a SiC(0001) substrate after the Au intercalation has been carried out. It was shown that deposition of Au and subsequent annealing of the system at a temperature of 500°C leads to the intercalation of Au atoms and the formation of gold silicide under graphene with a stoichiometry close to that of Au2Si. The study of the electronic structure of the system in the region of the K point of the surface Brillouin zone revealed the quasi-freestanding character of graphene with a linear spectrum of π states and a Dirac point near the Fermi level. The measurements using photoelectron microscopy showed the homogeneity of the work function along the surface of the sample on a micrometer scale.

The results of studying the electronic states of the conduction band and interface potential barrier during the formation of ultrathin films of thiophene-phenylene co-oligomer CH3-phenylene-thiophene-thiophene-phenylene -CH3(CH3-PTTP-CH3) on the surface of ZnO and films of biphenyl tetracarboxylic dianhydride (BPDA) on the ZnO surface are presented. A 100 nm thick ZnO layer was prepared by atomic layer deposition (ALD). Organic CH3-PTTP-CH3 films and BPDA films up to 8 nm thick were formed by thermal vacuum deposition. During film deposition, the electronic characteristics of the surface were studied using total current spectroscopy (TCS) in the energy range from 5 eV to 20 eV above EF. In this energy range, the structure of the maxima of the unoccupied electronic states of CH3-PTTP-CH3 and BPDA films was determined. As a result of the CH3-PTTP-CH3 film deposition, a decrease in the work function to 4.0 eV was found, compared with the value of the work function of 4.2 eV measured from the ALD ZnO-substrate. This corresponds to the transfer of a negative charge from the CH3-PTTP-CH3 film to the substrate. The charge transfer at the interface between the BPDA film and the ALD ZnO-substrate occurs in the opposite direction, since a 4.7 eV increase of the work function was registered during the formation of this interface. The CH3-PTTP-CH3 and BPDA films studied and the layer-by-layer grown ZnO film represent a continuous coating on sufficiently large surface areas of the order of 10 μmx10 μm. The roughness of the ZnO surface does not exceed 4 nm, and the surface roughness of CH3-PTTP-CH3 and BPDA films was 10-15 nm. Keywords: thiophene-phenylene co-oligomers, biphenyl tetracarboxylic dianhydride, ultrathin films, ZnO, atomic layer deposition method, electronic properties, low-energy electron spectroscopy, interface potential barrier.

Graphene grown on an ultrathin CoSi/CoSi 2 silicide layer atop a SiC(0001) substrate and intercalated by Au was studied. Intercalation of Au was found to occur at a temperature of 500 o C, and it is accompanied by the formation of gold silicide under graphene with a stoichiometry close to Au 2 Si. The study of the electronic structure of the system in the region of the (K) point of the surface Brillouin zone revealed the quasi-freestanding character of graphene with a linear spectrum of π states and a Dirac point near the Fermi level. Photoelectron microscopy revealed the homogeneity of the work function along the surface of the sample on a micrometer scale. Keywords: Graphene, magneto-spin-orbit graphene, intercalation, photoelectron spectroscopy, electronic structure.

Modification of the electronic and crystal structure of zero-layer graphene grown on 6H-SiC(0001) after Co intercalation is reported. Using a wide range of techniques including angle-resolved photoelectron spectroscopy, x-ray photoelectron spectroscopy, Raman spectroscopy, low-energy electron diffraction, we found that zero-layer graphene on SiC transforms into graphene monolayer as a result of cobalt intercalation. The Dirac cone of pi band characteristic of quasi-freestanding graphene is observed. In combination with high-resolution transmission electron microscopy and atomic force microscopy data, we conclude that ultrathin silicide CoSi/CoSi2 structure is formed between graphene and SiC substrate. Investigation of magnetic properties reveals ferromagnetic behavior with open hysteresis loop. The results of this work are the basis for further implementation of magneto-spin-orbit graphene on a semiconducting substrate and are important for the future application of such graphene in spintronics.

The work investigated the formation possibility of ordered silicon structures, including silicene, on the graphite substrates surface. The various conditions influence on the silicon atoms deposition on the final structure was also studied. Surface morphology information was obtained by atomic force microscopy, and the electronic structure was measured by Auger electron spectroscopy.

The possibility of formation of ordered silicon structures, including silicene, on the graphite substrate surface has been studied. The effect of various conditions of depositing silicon atoms on a finite structure has also been studied. The data on the surface morphology has been obtained by atomic force microscopy, and the electronic structure has been studied by Auger electron spectroscopy.

AbstractThe effect of the physical adsorption of nickel on a surface of a topological Bi_2Se_3 insulator on the electronic structure has been studied. The influence of the adsorbate on the chemical bond between Bi and Se atoms has been studied by X-ray photoelectron spectroscopy. It is shown as well that nickel atoms diffuse into the topological insulator volume at room temperature.

A detailed study of graphene growth process via segregation of carbon atoms through a 16 nm-thick metal film is presented. Two different transition metals - Co and Ni - are deposited on a highly-oriented pyrolytic graphite ( HOPG) substrate. It is demonstrated that annealing of the systems leads to segregation of carbon atoms from the substrate to the surface. X-ray photoemission studies show that in both cases a metal-rich carbide phase is formed in a near-surface area, which after a low-temperature annealing transforms into carbon-rich carbide phase. After further increase of the annealing temperature this carbide phase is transformed into graphene mono-and multilayers. Low energy electron diffraction measurements show that at the final stage a large part of the sample is covered with highly-ordered graphene domains, however a lot of small variously oriented domains can also be seen. It is shown that graphene on Co/HOPG is formed at comparable temperatures to that on Ni/HOPG, and it has better ordered surface.

The effect of the physical adsorption of nickel on a surface of a topological Bi2Se3 insulator on the electronic structure has been studied. The influence of the adsorbate on the chemical bond between Bi and Se atoms has been studied by X-ray photoelectron spectroscopy. It is shown as well that nickel atoms diffuse into the topological insulator volume at room temperature.

Методом фотоэлектронной спектроскопии с угловым разрешением и рентгеновской фотоэлектронной спектроскопией исследована возможность формирования упорядоченной структуры, схожей с силиценом, на поверхности Au/W(110). Показано, что добавление атомов кремния приводит к заметному искажению электронной структуры исходной подложки и сформированная электронная структура не соотносится с силиценом. При этом конфигурация рефлексов на картине дифракции медленных электронов свидетельствует об образовании упорядоченных двумерных кремниевых структур с большим числом разнонаправленных доменов. Исследования проводились на оборудовании Ресурсного центра "Физические методы исследования поверхности" Научного парка СПбГУ. DOI: 10.21883/FTT.2017.12.45246.092

The possibility of formation of an ordered silicene-like structure on Au/W(110) surface has been considered using angle-resolved photoelectron spectroscopy and X-ray photoelectron spectroscopy. It is shown that the addition of silicon atoms results in a considerable distortion of the electron structure of the initial substrate, and the resulting electron structure cannot be attributed to silicene. The configuration of reflections in the low energy electron diffraction pattern indicates the formation of two-dimensional ordered silicon structures with a large number of multidirectional domains.

A new method for generating spin-polarized currents in topological insulators has been proposed and investigated. The method is associated with the spin-dependent asymmetry of the generation of holes at the Fermi level for branches of topological surface states with the opposite spin orientation under the circularly polarized synchrotron radiation. The result of the generation of holes is the formation of compensating spin-polarized currents, the value of which is determined by the concentration of the generated holes and depends on the specific features of the electronic and spin structures of the system. The indicator of the formed spin-polarized current can be a shift of the Fermi edge in the photoelectron spectra upon photoexcitation by synchrotron radiation with the opposite circular polarization. The topological insulators with different stoichiometric compositions (Bi1.5Sb0.5Te1.8Se1.2 and PbBi2Se2Te2) have been investigated. It has been found that there is a correlation in the shifts and generated spin-polarized currents with the specific features of the electronic spin structure. Investigations of the graphene/Pt(111) system have demonstrated the possibility of using this method for other systems with a spin-polarized electronic structure.

A comparative investigation of graphene prepared by cracking of propylene (C 3 H 6 ) on nickel surfaces with different orientations, Ni(111) and Ni(100), has been carried out using angle-resolved photoemission spectroscopy. It has been shown that the graphene formed on the Ni(111) surface is well ordered on a large surface area, whereas the graphene on the Ni(100) surface has a well-defined domain structure. It has been found that the electronic structures of the two systems are similar to each other, and graphene is strongly bound to the nickel substrate. It has been demonstrated that the intercalation of a gold monolayer for the two systems leads to the formation of an electronic structure that is characteristic of quasi-free-standing graphene.