Recently, there is an increasing need to create energy-efficient power supplies for wearable devices. In recent studies, we found that carbon nanotubes doped with nitrogen, which exhibit anomalous piezoelectric properties, can be used as the basis for such devices. This paper presents the results of studying the effect of the activation time of catalytic centers during the growth of carbon nanotubes on the value of their piezoelectric strain coefficient and the value of the generated current. It was found that with an increase in the activation time of the catalytic centers from 1 to 90 min, the value of the piezoelectric strain coefficient decreased from 19.78pm/V to 4.49pm/V, which is associated with a change in the geometric dimensions of the catalytic centers and, consequently, the N-CNT and structures of the N-CNTs. Also, the data obtained are confirmed by the measured value of the current generated by N-CNTs during deformation. Its value decreased from 15 to 2 nA in proportion to the decrease in the piezoelectric strain coefficient. The results obtained can be used to create energy-efficient piezoelectric nanogenerators

The results of experimental studies of the influence of the ratio of process-gas flows of acetylene and ammonia on the value of the piezoelectric strain coefficient of nitrogen-doped carbon nanotubes (N‑CNTs) are presented. It is found that the value of the piezoelectric strain coefficient of N-CNTs increases from 10.9 to 20.6 pm/V when the flow ratio increases from 1 : 1 to 1 : 6, and then decreases to 18.4 pm/V when the ratio increases to 1 : 10. It is shown that this nonlinear dependence is caused by a simultaneous change in the concentration of the nitrogen dopant and the geometric parameters of the nanotube. The obtained results can be used in the development of energy-efficient piezoelectric nanogenerators based on N-CNTs.

The regularities of the influence of the growth temperature on the geometrical parameters, the concentration of the dopant nitrogen and the type of defects formed in carbon nanotubes grown on a molybdenum sublayer are established in this paper. It is shown that the best piezoelectric and resistive properties are observed in nitrogen-doped carbon nanotubes (N-CNTs) grown at a temperature of 525°C, which is due to the highest concentration of dopant nitrogen and high aspect ratio of nanotubes. Based on the results of thermodynamic analysis, the dependence of the dopant nitrogen concentration and the defect type on the tendency to form molybdenum nitrides and carbides during the growth of N-CNTs is shown. The obtained results can be used in the development of nanopiezotronic devices based on arrays of vertically aligned N-CNTs: nanogenerators, strain sensors and memory elements.

Уважаемые коллеги!Благодарим Вас за проявленный интерес к Четвертой российской конференции «Графен: молекула и 2D кристалл» и желание принять участие в её работе.Конференция проходит в научно-образовательном центре города Новосибирска -Академгородке.Мероприятие посвящено актуальным направлениям исследований и разработок в области углеродных и низкоразмерных материалов.Проведение конференции поможет координации усилий ученых в решении современных проблем материаловедения и привлечению молодых исследователей для решения актуальных научных задач.Оргкомитет выражает особую благодарность НГУ, Центру компетенций НТИ «Моделирование и разработка новых функциональных материалов с заданными свойствами», компаниям «Диаэм», «НТ-МДТ Спектрум Инструментс» и корпорации "Графеновая Долина" за финансовую поддержку и журналам Аналитика, Наноиндустрия и РЭНСИТ за информационную поддержку.Искренне надеемся, что пребывание в Новосибирском Академгородке и в стенах Новосибирского государственного университета оставит множество положительных эмоций и

The development of miniature autonomous power sources for personal electronics and the Internet of things is one of the urgent tasks of modern science. A promising direction in this area is powering such devices by harvesting and converting the mechanical energy of the environment into electrical energy. This study investigates the ability of nitrogen-doped carbon nanotubes (N-CNTs) to convert and store mechanical energy into electrical energy to create piezoelectric nanogenerators. It is shown that N-CNTs under conditions of constant vibration noise generate a surface potential and a corresponding current of about 33 nA throughout the entire exposure time without a tendency to decrease in current value. It is established that a potential barrier is formed at the boundaries of the side wall of N-CNTs with bamboo-like bridges, which allows the storage of a piezoelectric charge induced during nanotube deformation. This fact opens up wide opportunities for creating a miniature power source based on N-CNTs, combining the possibility of converting and accumulating mechanical energy of the environment.

This paper establishes patterns of influence of ambient humidity on the piezoelectric strain coefficient and the magnitude of the current generated by nitrogen-doped carbon nanotubes (N-CNTs) during their deformation. It is shown that at humidity up to 60%, stable current generation is observed during the deformation of N-CNTs; at higher humidity, the instability of measurements increases and the spread of the generated current grows significantly, which is associated with a decrease in the N-CNTs piezoelectric strain coefficient.

Уважаемые коллеги!Благодарим Вас за проявленный интерес к Четвертой российской конференции «Графен: молекула и 2D кристалл» и желание принять участие в её работе.Конференция проходит в научно-образовательном центре города Новосибирска -Академгородке.Мероприятие посвящено актуальным направлениям исследований и разработок в области углеродных и низкоразмерных материалов.Проведение конференции поможет координации усилий ученых в решении современных проблем материаловедения и привлечению молодых исследователей для решения актуальных научных задач.Оргкомитет выражает особую благодарность НГУ, Центру компетенций НТИ «Моделирование и разработка новых функциональных материалов с заданными свойствами», компаниям «Диаэм», «НТ-МДТ Спектрум Инструментс» и корпорации "Графеновая Долина" за финансовую поддержку и журналам Аналитика, Наноиндустрия и РЭНСИТ за информационную поддержку.Искренне надеемся, что пребывание в Новосибирском Академгородке и в стенах Новосибирского государственного университета оставит множество положительных эмоций и

The creation of sustainable power sources for wearable electronics and self-powered systems is a promising direction of modern electronics. At the moment, a search for functional materials with high values of piezoelectric coefficient and elasticity, as well as non-toxicity, is underway to generate such power sources. In this paper, nitrogen-doped carbon nanotubes (N-CNTs) are considered as a functional material for a piezoelectric nanogenerator capable of converting nanoscale deformations into electrical energy. The effect of defectiveness and of geometric and mechanical parameters of N-CNTs on the current generated during their deformation is studied. It was established that the piezoelectric response of N-CNTs increased nonlinearly with an increase in the Young’s modulus and the aspect ratio of the length to diameter of the nanotube and, on the contrary, decreased with an increase in defectiveness not caused by the incorporation of nitrogen atoms. The advantages of using N-CNT to create energy-efficient piezoelectric nanogenerators are shown.

The regularities of the influence of the growth temperature on the geometrical parameters, the concentration of the dopant nitrogen and the type of defects formed in carbon nanotubes grown on a molybdenum sublayer are established in this paper. It is shown that the best piezoelectric and resistive properties are observed in nitrogen-doped carbon nanotubes (N-CNTs) grown at a temperature of 525 ºС, which is due to the highest concentration of dopant nitrogen and high aspect ratio of nanotubes. Based on the results of thermodynamic analysis, the dependence of the dopant nitrogen concentration and the defect type on the tendency to form molybdenum nitrides and carbides during the growth of N-CNTs is shown. The obtained results can be used in the development of nanopiezotronic devices based on arrays of vertically aligned N-CNTs: nanogenerators, strain sensors and memory elements.

The chemical composition and stoichiometry of vertically aligned arrays of nitrogen-doped multi-walled carbon nanotubes (N-CNTs) were studied by photoelectron spectroscopy using laboratory and synchrotron X-ray sources. We performed careful deconvolution of high-resolution core-level spectra to quantify pyridine/pyrrole-like defects in N-CNTs, which are a key factor in the efficiency of the piezoelectric response for this material. It is shown that the XPS method makes it possible to estimate the concentration and type of nitrogen incorporation (qualitatively and quantitatively) in the “N-CNT/Mo electrode” system using both synchrotron and laboratory sources. The obtained results allow us to study the effect of the nickel catalytic layer thickness on the concentration of pyridine/pyrrole-like nitrogen and piezoelectric response in the nanotubes.

The solid solutions (SS) of the n-component (n = 2 ... 6) systems with the participation of two fundamentally different bases - (Na, K)NbO3 (NKN) and Pb(Ti, Zr)O3 (PZT) have been prepared by the two-stage solid-phase synthesis followed by the conventional sintering ceramic technology. Evolution trends of the structural and electrophysical parameters at such a complication of the compositions have been established. It is shown that with an increase in the number of the components in the systems, the spontaneous deformation, characterized by a uniform deformation parameter, delta, decreases, which, due to the existing correlations, leads to a decrease in the Curie temperature and an increase in the relative permittivity. The extreme "behavior" of the piezoelectric characteristics is associated with the competing influence of the permittivity and remanent polarization on them. A conclusion is made about the expediency of using the obtained results in the creation of similar materials and devices based on them.

Memristive devices are one of the promising candidates for creating neuromorphic systems due to the possibility of multilevel switching, low operating voltages and high scalability. However, as with any passive element, the memristor requires an external bias voltage to operate, which requires the inclusion of a power source in the circuit. In this regard, of great interest are works on the creation of self-powered memristive systems consisting of connecting in series a memristor and a nanogenerator that converts the energy of the external environment into electrical energy [1, 2]. Such a memristive system has a high potential for applications in aerospace and implantable electronics. At the moment, the first self-powered memristive and sensor systems based on metal oxides and piezoelectric nanogenerators (PENG) have already been developed [2]. The main problems in this area are to reduce the size of the nanogenerator and to match the output parameters of the nanogenerator and the input parameters of the memristor. In the framework of this work, these problems are being resolved by creating a self-powered memristive system based on nitrogen-doped carbon nanotubes (N-CNTs). Previously, we studied the memristive properties of N-CNTs and showed that nanotubes demonstrate reproducible multilevel switching with a resistance ratio in the high- and low-resistance states (HRS/LRS) of about 4⋅105 [3, 4]. It was found that the memristive effect in N-CNTs is due to the incorporation of nitrogen atoms into the nanotube structure and the formation of an internal piezoelectric field [4]. As part of further studies, it was found that an array of vertically aligned N-CNTs is a promising material for creating PENG: the generated output voltage is hundreds of mV and the current generated by single nanotube reaches hundreds of nA [5]. The results obtained allow us to speak about the possibility of developing a self-powered memristive system by connecting in series a memristor and PENG based on N-CNTs. To optimize the output characteristics of the PENG, in particular, the amplitude of the generated voltage, and the input switching voltage of the N-CNT-based memristor, studies were carried out to increase the piezoelectric response and reduce the switching voltage of the N-CNT resistance by changing the concentration of the dopant nitrogen in the nanotube growth process. It was found that it is necessary to grow N-CNTs with a doping nitrogen concentration of up to 12% and a high aspect ratio of length to diameter (more than 60) to create PENG with an output voltage of up to 2 V. These N-CNT parameters are provided at a low growth temperature (500–550 C°) and high ratio of acetylene and ammonia flows (1:5 - 1:6). On the contrary, the N-CNTs with a small aspect ratio (less than 30) and doping nitrogen concentrations of 4–6% are required for the manufacture of memristors with a minimum switching voltage (about 2 V), These N-CNT parameters are provided by increasing the growth temperature to 615 C° and reduction in growth time. The obtained results can be used in the development of self-powered memristive and sensor systems based on nitrogen-doped carbon nanotubes.

The relevance of the development of miniature power supplies has increased significantly over the past decade due to the large spread of wearable electronics devices. A promising direction for solving this problem is the use of the piezoelectric effect in nanoscale structures to convert external mechanical energy (human body movement, vibrations from urban noise, etc.) into electrical energy to create piezoelectric nanogenerators (PENG). Existing piezoelectric materials have a number of disadvantages (fragility, toxicity). Therefore the search for suitable functional materials for creating energy-efficient PENGs is still ongoing. Previously, it was found that nitrogen-doped carbon nanotubes (N-CNTs) exhibit anomalous piezoelectric properties, the source of which are bamboo-like bridges in the cavity of N-CNTs formed as a result of the embedding of pyrrole-like nitrogen atoms. This allows the use of the N-CNTs as a functional PENG material. This paper presents the results of a study of the effect of the lower electrode material on the value of the piezoelectric strain coefficient and the current generated during the deformation of nitrogen-doped carbon nanotubes. It is established that the largest value of the piezoelectric strain coefficient (113.5 ± 9.8 pm/V) observed for an array of N-CNTs grown on a molybdenum electrode. The obtained results can be used in the development of energy-efficient PENG based on N-CNT.

The piezoelectric properties of vertically aligned carbon nanotubes (CNTs) are characterized by piezoresponse force microscopy, and their dependence on the concentration of the doping impurity of nitrogen is established. It is shown that carbon nanotubes have predominantly longitudinal polarization, due to the direction of the dipole moment in the bamboo-like bridges of the nanotubes. It is found that lowering the temperature of growth from 690 to 645°C raises of piezoelectric strain coefficient of the carbon nanotubes from 4.5 to 21.2 pm/V. Results in this work can be used in developing energy-efficient nanopiezotronic devices.

Recent studies show that the additional introduction of heteroatoms into the structure of CNTs makes it possible to change their electronic and physical properties [1]. Of great interest is the process of doping CNTs with nitrogen atoms [2]. The introduction of nitrogen defects into a lattice of carbon atoms makes it possible to modify the CNT structure up to the demonstration of anomalous properties that are not appropriate for this material [3]. It has been shown that multi-walled N-CNTs can exhibit memristive and piezoelectric properties [4]. The parameters of CNTs during synthesis can be controlled by the plasma enhanced chemical vapor deposition (PECVD) method. The addition of ammonia (NH3) to the carbonaceous gas in the PECVD process allows CNTs to be doped directly during growth. At the same time, the dopant concentration and the type of nitrogen defects have a significant effect on the properties of CNTs. The memristive properties of CNTs have already been sufficiently studied [5], however, for their application in self-powered systems, additional studies of the parameters of the piezoelectric module of N-CNTs are required. The aim of this work is to study the effect of ammonia flow on the concentration, type of nitrogen defects, and the value of the piezoelectric modulus during growth of CNTs by the PECVD. Silicon (100) substrates were used as samples with films of a buffer (Mo, 100 nm) sublayer and a catalytic layer (Ni, 15 nm). CNTs were grown at a temperature of 550 °C in an atmosphere of acetylene (C2H2, 35 sccm) and NH3. The C2H2 flow was kept constant, while the NH3 flow was changed in the C2H2:NH3 ratio from 1:1 to 1:10. Based on the obtained SEM images, it was found that with an increase in the ratio of C2H2:NH3 flowes, an increase in the density of nanotubes in the array were observed. This occurs due to more active growth of N-CNTs on small nickel catalytic centers due to the accelerated process of hydrogen desorption and its binding with ions in ammonia plasma, which leads to an increase in the growth rate of nanotubes on smaller catalytic centers. Thus, the area of the catalytic center is one of the limiting factors of the growth rate and allows one to control the aspect ratio and density of CNTs in the array. An analysis of the XPS spectra showed that with an increase in the ratio of C2H2:NH3 flows from 1:1 to 1:10, a nonlinear change in the concentration of the nitrogen dopant in N-CNTs from 8.4 to 12 at % is also observed. This led to a nonlinear change in the piezoelectric modulus of nanotubes from 8.7 to 20.6 pm/V and a change in their memristive properties. It has been established that an increase in the concentration of doping nitrogen leads to an increase in the piezoelectric modulus of N-CNTs, which is the source of the memristive effect. The obtained results can be used in the development of energy-efficient piezoelectric nanogenerators based on an array of vertically aligned N-CNTs for autonomous memristive systems.

Thin films of lead zirconate titanate were formed by plasma radiofrequency sputtering on a low-resistance silicon substrate. The properties of the films were studied by X-ray phase analysis, scanning electron microscopy, atomic force microscopy and, piezoresponse force microscopy. The domain structure was determined by the morphology of the film surface, which had a high surface potential having an average value of +10 V. The average value of the piezoelectric modulus was 15.5 divided by 17.9 pC/V, and the magnitude of the coercive field was (3.05 +/- 0.25)center dot 10(5) V/cm. The formed PZT films can be used to manufacture the energy harvesters.

The development of nonvolatile memory is one of the urgent problems of contemporary science due to the rapid evolution of portable electronics. A promising trend in this field is the development of memristor structures able to change their resistance depending on the charge current through a memristor. The memristive effect in nitrogen-doped carbon nanotubes (CNT) is studied. It is established that the ratio between the resistances in high- and low-resistance states grows with an increase in the defectiveness of the carbon nanotubes to attain 4 × 105. It is shown that multilevel switching of the resistance determined by the recording voltage or deformation of a nanotube is possible in carbon nanotubes. The obtained results can be used for developing nonvolatile memory on the basis of CNTs corresponding to the condition of high scalability and multilevel switching.

In this paper, the films of lead zirconate-titanate formed by the method of high-frequency reactive plasma sputtering in oxygen are studied. The films have a thickness of 610-660 nm and a developed relief with a predominant number of protrusions with a height of 100-300 nm. It is shown by the methods of X-ray phase analysis and piezoelectric force microscopy that the PZT crystallites are located on the surface of the protrusions. The piezoelectric strain coefficient value is 2,73+0,44 pm/V. The formed PZT films can be used in 3D elements of nanopiezotronics (memory elements, sensors of mechanical influences, energy harvesters). Copyright (C) 2022 Elsevier Ltd. All rights reserved.

The paper reports results on the complex study on ferroelectric ceramics that represent solid solutions containing components with a perovskite-type or columbite-type structure. Solid solutions of a three-component (1[Formula: see text])[Formula: see text][Formula: see text]CdNb2O6 system are manufactured at [Formula: see text] = 0.05–0.20 and [Formula: see text] = 0.10. Domain structures in ceramic grains are studied. The consistency between experimental and calculated results is examined for coexisting phases split into non-180[Formula: see text] domains (mechanical twins) in the solid solution with [Formula: see text] = 0.15. A correlation between the internal structure (crystal, domain, granular, and defect) and fundamental electromechanical and polarization properties is stated for the studied three-component solid solutions.