Vertically Aligned Carbon Nanotubes Production by PECVD

This chapter presents the results of experimental studies of the PECVD technological mode parameters’ influence on the formation of catalytic centers and carbon nanotubes’ (CNTs’) growth processes. This chapter also presents the ability to regulate the growth parameter for the controlled production of CNTs with the required geometric parameters, properties, and growth mechanisms. The results of experimental studies of the heating temperature and activation time effects on the catalytic center formation will be presented. This chapter also shows the effects of growth temperature, heating rate, and the activation time on the geometric and structural parameters of the carbon nanotubes. Experimental studies were carried out with the use of AFM, SEM, TEM, and EXAFS techniques. The results can be used in the development of technological processes for creating ultrafast energy-efficient electronic component base with carbon nanostructures, particularly nanoelectromechanical switches, flexo- and piezoelectric generators, gas sensors, and high-performance emitters

Application of Probe Nanotechnologies for Memristor Structures Formation and Characterization

This chapter presents the results of experimental studies of the formation and investigation of the memristors by probe nanotechnologies. This chapter also perspectives and possibilities of application of local anodic oxidation and scratching probe nanolithography for the manufacture of memristors based on titanium oxide structures, nanocrystalline ZnO thin film, and vertically aligned carbon nanotubes. Memristive properties of vertically aligned carbon nanotubes, titanium oxide, and ZnO nanostructures were investigated by scanning probe microscopy methods. It is shown that nanocrystalline ZnO films manifest a stable memristor effect slightly dependent on its morphology. Titanium oxide nanoscale structures of different thicknesses obtained by local anodic oxidation demonstrate a memristive effect without the need to perform any additional electroforming operations. This experimentally confirmed the memristive switching of a two-electrode structure based on a vertically aligned carbon nanotube. These results can be used in the development of designs and technological processes of resistive random access memory (ReRAM) units based on the memristor devices

Scanning Probe Techniques for Characterization of Vertically Aligned Carbon Nanotubes

This chapter presents the results of experimental studies of the electrical, mechanical and geometric parameters of vertically aligned carbon nanotubes (VA CNTs) using scanning probe microscopy (SPM). This chapter also presents the features and difficulties of characterization of VA CNTs in different scanning modes of the SPM. Advanced techniques for VA CNT characterization (the height, Young’s modulus, resistivity, adhesion and piezoelectric response) taking into account the features of the SPM modes are described. The proposed techniques allow to overcome the difficulties associated with the vertical orientation and high aspect ratio of nanotubes in determining the electrical and mechanical parameters of the VA CNTs by standard methods. The results can be used in the development of diagnostic methods as well as in nanoelectronics and nanosystem devices based on vertically aligned carbon nanotubes (memory elements, adhesive structures, nanoelectromechanical switches, emission structures, etc.)

Piezoelectric Response of Multi-Walled Carbon Nanotubes

Recent studies in nanopiezotronics have indicated that strained graphene may exhibit abnormal flexoelectric and piezoelectric properties. Similar assumptions have been made with regard to the properties of carbon nanotubes (CNTs), however, this has not so far been confirmed. This paper presents the results of our experimental studies confirming the occurrence of a surface piezoelectric effect in multi-walled CNTs under a non-uniform strain. Using atomic force microscopy, we demonstrated the piezoelectric response of multi-walled CNTs under compression and bending. The current generated by deforming an individual CNT was shown to be −24 nA. The value of the surface potential at the top of the bundle of strained CNTs varied from 268 mV to −110 mV, depending on strain type and magnitude. We showed that the maximum values of the current and the surface potential can be achieved when longitudinal strain predominates in a CNT. However, increasing the bending strain of CNTs does not lead to a significant increase in current and surface potential, due to the mutual compensation of piezoelectric charges concentrated on the CNT side walls. The results of the study offer a number of opportunities and challenges for further fundamental research on the piezoelectric properties of carbon nanotubes as well as for the development of advanced CNT-based nanopiezotronic devices

Comparison of Synchrotron and Laboratory X-ray Sources in Photoelectron Spectroscopy Experiments for the Study of Nitrogen-Doped Carbon Nanotubes

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

Piezoelectric Response of Multi-Walled Carbon Nanotubes

Recent studies in nanopiezotronics have indicated that strained graphene may exhibit abnormal flexoelectric and piezoelectric properties. Similar assumptions have been made with regard to the properties of carbon nanotubes (CNTs), however, this has not so far been confirmed. This paper presents the results of our experimental studies confirming the occurrence of a surface piezoelectric effect in multi-walled CNTs under a non-uniform strain. Using atomic force microscopy, we demonstrated the piezoelectric response of multi-walled CNTs under compression and bending. The current generated by deforming an individual CNT was shown to be −24 nA. The value of the surface potential at the top of the bundle of strained CNTs varied from 268 mV to −110 mV, depending on strain type and magnitude. We showed that the maximum values of the current and the surface potential can be achieved when longitudinal strain predominates in a CNT. However, increasing the bending strain of CNTs does not lead to a significant increase in current and surface potential, due to the mutual compensation of piezoelectric charges concentrated on the CNT side walls. The results of the study offer a number of opportunities and challenges for further fundamental research on the piezoelectric properties of carbon nanotubes as well as for the development of advanced CNT-based nanopiezotronic devices

Analysis of the Piezoelectric Properties of Aligned Multi-Walled Carbon Nanotubes

Recent studies reveal that carbon nanostructures show anomalous piezoelectric properties when the central symmetry of their structure is violated. Particular focus is given to carbon nanotubes (CNTs) with initial significant curvature of the graphene sheet surface, which leads to an asymmetric redistribution of the electron density. This paper presents the results of studies on the piezoelectric properties of aligned multi-walled CNTs. An original technique for evaluating the effective piezoelectric coefficient of CNTs is presented. For the first time, in this study, we investigate the influence of the growth temperature and thickness of the catalytic Ni layer on the value of the piezoelectric coefficient of CNTs. We establish the relationship between the effective piezoelectric coefficient of CNTs and their defectiveness and diameter, which determines the curvature of the graphene sheet surface. The calculated values of the effective piezoelectric coefficient of CNTs are shown to be between 0.019 and 0.413 C/m2, depending on the degree of their defectiveness and diameter

Serine Proteinases Secreted by Two Isolates of the Fungus Alternaria solani

It is well-known Alternaria solani Sorauer is the causative agent of alternariosis. In this paper, serine proteinases secretion by two genetically related isolates of the fungus, collected from potato and tomato plants grown in central Russia have been studied. The data clarify functions of these enzymes in the process of pathogenesis in which they can play a pivotal role. Also, the data should allow classifying Alternaria’s strains more precisely. It was found that the two isolates produced trypsin-like and subtilisin-like proteinases during growth both in synthetic culture medium and in medium containing heat-stable vegetable proteins. There were significant differences in the influence of the environment on the serine proteinase secretion by the potato and tomato isolates of A. solani. The proportion of such serine proteinases as trypsin-like and subtilisin-like enzymes depends on the composition of the growth medium, especially on the available organic nitrogen form, as well as features both of the pathogenic fungus and of the host plant. So, the tomato isolate demonstrated weak growth and low level or absence of serine proteinase excretion on cultivation with the medium containing proteins extracted from potato tubers and pea seeds. The potato isolate secreted many more serine proteinases, among which the trypsin-like enzymes dominated. Our data suggest that the tomato isolate, when grown on medium with proteins extracted from potato tubers, lost pathogenicity and became to behave as a saprophyte, while the potato isolate retained its pathogenic properties on growth on any tested medium

Serine Proteinases Secreted by Two Isolates of the Fungus Alternaria solani

It is well-known Alternaria solani Sorauer is the causative agent of alternariosis. In this paper, serine proteinases secretion by two genetically related isolates of the fungus, collected from potato and tomato plants grown in central Russia have been studied. The data clarify functions of these enzymes in the process of pathogenesis in which they can play a pivotal role. Also, the data should allow classifying Alternaria’s strains more precisely. It was found that the two isolates produced trypsin-like and subtilisin-like proteinases during growth both in synthetic culture medium and in medium containing heat-stable vegetable proteins. There were significant differences in the influence of the environment on the serine proteinase secretion by the potato and tomato isolates of A. solani. The proportion of such serine proteinases as trypsin-like and subtilisin-like enzymes depends on the composition of the growth medium, especially on the available organic nitrogen form, as well as features both of the pathogenic fungus and of the host plant. So, the tomato isolate demonstrated weak growth and low level or absence of serine proteinase excretion on cultivation with the medium containing proteins extracted from potato tubers and pea seeds. The potato isolate secreted many more serine proteinases, among which the trypsin-like enzymes dominated. Our data suggest that the tomato isolate, when grown on medium with proteins extracted from potato tubers, lost pathogenicity and became to behave as a saprophyte, while the potato isolate retained its pathogenic properties on growth on any tested medium