The photoresponse in multilayer graphene on a lithium niobate crystal (LiNbO3) was studied under the conditions of an electric potential applied to graphene and transmission of a surface acoustic wave (SAW). It is shown that the acoustoelectric current in graphene when irradiated with light either increases or decreases depending on the polarity of the potential applied to graphene. SAW causes the appearance of a periodic charge lattice in graphene, which enhances the interaction with incident light, which leads to an increase in the photoresponse.

In this Letter, we studied the photoresponse in multilayer graphene on a lithium niobate (LiNbO3) crystal under the conditions of an electric potential applied to graphene and transmission of a surface acoustic wave. The acoustoelectric current in graphene when irradiated with light is shown to either increase or decrease depending on the polarity of the potential applied to graphene. A surface acoustic wave causes the appearance of a periodic charge lattice in graphene that enhances the interaction with incident light, which leads to an increase in the photoresponse.

Graphene films were grown by the low-pressure chemical vapor deposition with a single injection of acetylene on an iron film catalyst deposited on oxidized silicon substrate. After treatment of the graphene on the iron film with aqueous solution of iron nitrate the structures consisting of quasi-suspended graphene on reaction products of the iron film with iron nitrate were obtained. The electron transport and magnetotransport properties of the films were investigated. The films have a low resistance of 80 Ohm sq−1 and a high sheet carrier density (8 × 1013 cm−2 at room temperature). At temperatures less than 200 K, the dependence of the Hall resistance on the magnetic field is like the abnormal Hall effect. Large positive linear magnetoresistance at a room temperature (60–100%) was observed in the films in a field of 0.6 T, which is attractive for creating magnetoresistive sensors. It was found that the critical magnetic field at which the MR becomes linear is very small (116–650 Oe) and linearly dependent on a temperature. The MR is proportional to the average mobility 〈µ〉. At low temperatures, the magnetoresistance increases with increasing temperature. At higher temperatures the MR decreases with increasing temperature.

Graphene films were grown on an iron film catalyst deposited on oxidized silicon substrate, using the low-pressure chemical vapor deposition. Subsequently the iron film was dissolved with an aqueous solution of iron nitrate. The structures consisting of quasi-suspended graphene on reaction products of an iron film with iron nitrate were obtained. Magnetoresistance properties of the structures were investigated at a room temperature, and the positive magnetoresistance was observed. The maximum magnetoresistance value was 100% in the magnetic field of 0.5T. The dependence of magnetoresistance on the magnetic field was quasi-linear in the range of 0.07–0.5T.

Hybrid structures composed of graphene films and (0001) graphene ribbons perpendicular to the surface of a graphene-like film have been produced through the catalytic decomposition of a carbon-containing gas on an Al-coated SiO2/Si substrate having Ni catalyst islands on its surface. A hybrid structure has been grown by a one-step chemical vapor deposition process, by admitting acetylene into a chamber for a short time. The hybrid structures thus produced have been used to fabricate Hall sensors with a sensitivity of 3000 Ω/T. The synthesized hybrid structures are potential candidates for use in nanoelectronic devices, energy storage systems, etc. The technique proposed for the growth of such films is compatible with technologies that are employed in the electronics industry.

Carbon films were fabricated on oxidized silicon substrates coated by treated bi-layer catalyst film using a chemical vapor deposition (CVD) method with a short-time acetylene inflow. The films consisted of carbon nanotubes and bundles of them, and graphene-like carbon nanostructures. Unusually high magnetic field sensitivity (3000Ω/T) obtained from Hall measurements was observed in the films. The effect of scaling the size of the Hall sensor from carbon films on its magnetic field sensitivity has been investigated. The sensitivity of the Hall sensor with an active area size of 0.13×0.13µm2 was found to be 1140Ω/T, which is much higher than reported in the literature. This carbon material is promising for the fabrication of Hall effect sensors of submicron size.

Пространственное распределение магнитного поля вокруг кончика магнитного кантилевера, покрытого пленкой кобальта толщиной 50 нм, исследовано с помощью FePt-датчика экстраординарного эффекта Холла. Измерена зависимость величины магнитного поля от расстояния между поверхностью датчика и кончиком МСМ-кантилевера: она обратно пропорциональна кубу расстояния, что находится в согласии с теорией. Значение величины магнитного поля, измеренное на кончике МСМ-кантилевера, равно 0.02 Тл.

The spatial distribution of the magnetic field around the tip of a magnetic cantilever coated with a cobalt film 50 nm thick is investigated using an FePt extraordinary Hall effect sensor. The magnetic field’s dependence on the distance between the sensor’s surface and the MFM cantilever is measured and found to be inversely proportional to the cubic distance, as predicted in theory. The magnetic field measured on the MFM cantilever tip is found to be 0.02 T.

The structures of graphene layer-carbon nanotube hybrid films produced via CVD with a single-stage flow of acetylene into a chamber containing a prepared substrate are studied. It is shown that such films have a hybrid double-layer structure consisting of a graphene layer and a dense continuous network of nanotubes. The graphene layer contains continuous extended areas 10–50 μm in size and island areas ∼0.1 μm in size. TEM images lead to the conclusion that the graphene layer and carbon nanotubes are bound by covalent bonds.

Исследована структура гибридных пленок графеновый слой-углеродные нанотрубки, полученных методом СVD с использованием однократного напуска ацетилена в камеру с подготовленной подложкой. Показано, что пленки представляют собой гибридную двухслойную структуру, состоящую из графенового слоя и густой сплошной сетки нанотрубок. Графеновый слой состоит как из сплошных протяженных участков размером 10–50 мкм, так и из островковых участков размером примерно 0.1 мкм. Полученные ПЭМ-изображения позволяют заключить, что в синтезированных гибридных пленках графеновый слой и углеродные нанотрубки связаны между собой ковалентными связями.

Graphene films were synthesized by the low-pressure no flow CVD on polycrystalline nickel catalyst films grown by the self-ion assisted deposition technique at different biases. Graphene films were transferred to a SiO2/Si substrate using PMMA. The graphene grown on Ni films with bimodal grain size distribution and weaker (111) texture had higher thickness uniformity and a lower number of graphene layers. The graphene grown on Ni films with a monomodal grain size distribution and stronger (111) texture had lower thickness uniformity and a higher number of graphene layers. The transport properties of the graphene films were investigated with the aid of Hall measurements.

The effect of the composition, deposition method, and preliminary annealing temperature of catalyst thin films on the structure of catalyst nanoparticles and carbon nanotubes synthesized by CVD with a single acetylene burst was studied. A catalyst preparation technique was found that yields the narrowest distribution of the diameters of nanoparticles and of single-wall carbon nanotubes grown on them.

Pd is widely used in producing electrodes to single-walled carbon nanotubes (SWNT). However up to now its ability to form ohmic contacts to SWNTs was not employed in scanning probe microscopy (SPM). Here we present a study of SWNTs with Pd electrodes by SPM using Pd-coated tips. SWNTs were selectively grown on oxidized silicon substrates by low pressure CVD method. Pd electrodes were prepared to SWNTs to fabricate two terminal structures for SWNTs resistance measurements. It is shown that SPM Kelvin mode is a reliable technique for SWNT detection on insulating substrate. Contact potential difference between Pd electrode and SWNT is measured using the Kelvin mode.

Single-wall carbon nanotubes were synthesized on specified parts of oxidized silicon substrates by single acetylene burst CVD and studied with high-resolution scanning electron and scanning probe micro-scopes. The resistance of individual nanotubes and nanotube series was measured using devices fabricated by the deposition of Pd and Pd/Al electrodes on the obtained single-wall nanotubes. The contact potential difference between Pd electrodes and carbon nanotubes was measured in the Kelvin mode of a scanning probe microscope.

Vertically oriented arrays of zinc oxide nanorods with high structural perfection and good optical properties have been obtained by gas-phase synthesis from the elements on the substrates. Homogeneous and heterogeneous e-n transitions have been produced on the basis of these arrays of nanorods. Thermal growth from salt mixtures has been used to synthesize zinc oxide nanorods doped with transition metals (Fe, Mn, Cr). Zinc oxide nanorods doped with iron, manganese, tin, and lithium showed room-temperature ferromagnetic properties. Two-terminal planar structures have been produced from the nanorods doped with chrome. These structures are sensitive to ultraviolet radiation and insensitive to visible light. The field-effect transistor made from the zinc oxide nanorod doped with chrome has electron conductivity and works in the enhancement mode.

Исследован экстраординарный эффект Холла (ЭЭХ) для ансамбля наночастиц Co, встроенного в матрицы W и Au. Показано, что величина сигнала ЭЭХ зависит от средневзвешенных толщин как наночастиц Co, так и обволакивающих их матриц. Максимальное значение ЭЭХ получено для средневзвешенных толщин наночастиц Co 0.3–0.6 нм. Величина сигнала ЭЭХ увеличивается также при уменьшении толщины пленки матриц вплоть до нарушения электрической сплошности получаемых структур. В системе Co–W получены структуры с чувствительностью S = U/I H = 32 /T, что открывает возможность создания ферромагнитных датчиков для локальной магнитометрии, работающих при комнатной температуре.

We present a new technique for CVD synthesis of carbon nanotubes without any gas flow and using a very low pressure of acetylene (down to 0.5 mbar). The good quality of obtained nanotubes is confirmed by TEM observation and electron diffraction patterns, Raman spectroscopy and electron transport measurements.

An experimental investigation is presented into the extraordinary Hall effect (EHE) in planar ensembles of Co nanoparticles embedded in a W or Au matrix. The EHE signal strength is shown to depend on the mean thicknesses of both the nanoparticles and the matrix. Its maximum is observed for mean Co thicknesses of 0.3–0.6 nm. The EHE signal is found to grow with decreasing matrix thickness until the structure loses its electrical continuity. A sensitivity as high as S = 32 Θ/T (S = ΔU/IΔH) is achieved with a Co-W film. This result opens up possibilities for building room-temperature ferromagnetic sensors for local magnetometry.