A. A. Fedotov

Memristor effect on bundles of vertically aligned carbon nanotubes tested by scanning tunnel microscopy

We report on the results of experimental study of an array of vertically aligned carbon nanotubes (VA CNTs) by scanning tunnel microscopy (STM). It is shown that upon the application of an external electric field to the STM probe/VA CNT system, individual VA CNTs are combined into bundles whose diameter depends on the radius of the tip of the STM probe. The memristor effect in VA CNTs is detected. For the VA CNT array under investigation, the resistivity ratio in the low- and high-resistance states at a voltage of 180 mV is 28. The results can be used in the development of structures and technological processes for designing nanoelectronics devices based on VA CNT arrays, including elements of ultrahigh-access memory cells for vacuum microelectronics devices.

Study of the resistive switching of vertically aligned carbon nanotubes by scanning tunneling microscopy

The effect of an external electric field on the electromechanical properties and regularities of the resistive switching of a vertically aligned carbon nanotube (VA CNT) has been studied experimentally using scanning tunneling microscopy. It has been shown that the VA CNT resistivity ratio in the high- and low-resistance states is higher than 25 as the distance between the scanning tunneling microscope (STM) probe and the VA CNT is 1 nm at a voltage of 8 V and depends on the voltage applied between the probe and the VA CNT. The proposed mechanism of resistive switching of VA CNTs is based on an instantaneous deformation and induction of a VA CNT internal electric field as a result of the sharp change in the time derivative of the external electric field strength. The obtained results can be used for the design and fabrication of resistive energy-efficient memory elements with a high density of storage cells on the basis of vertically aligned carbon nanotubes.

Development of a technique for determining Young’s modulus of vertically aligned carbon nanotubes using the nanoindentation method

A technique for determining Young’s modulus of vertically aligned carbon nanotubes using the refined micromechanical model of the nanoindentation of a forest of vertically aligned carbon nanotubes is developed. The results of experimental studies of Young’s modulus determination for vertically aligned carbon nanotubes with different geometrical parameters are given. It is shown that, for a forest of carbon nanotubes with an effective diameter of around 100 nm and an effective length of approximately 2 μm, as well as for a forest with an effective diameter of carbon nanotubes of roughly 52 nm and their effective length of nearly 500 nm, the values of Young’s modulus are 1.68 ± 0.08 and 1.01 ± 0.05 TPa, respectively. Our results can be used for developing the technological processes of the formation of structures for nano- and microelectronics and nano- and microsystem technology on the basis of vertically aligned carbon nanotubes.

Development of New Metamaterials for Advanced Element Base of Micro- and Nanoelectronics, and Microsystem Devices

The results of experimental researches of the geometrical parameters of vertically aligned carbon nanotubes (VACNTs) are present by atomic force microscopy. The analysis of the applicability of the different AFM modes to determine the geometrical parameters of VACNTs array was carried out and based on this analysis the rapid-technique for determination of the length of the nanotubes in VACNTs array was developed. Unified two-layer polysilicon surface micromachining process for manufacture of biaxial micromechanical gyroscope , triaxial micromechanical accelerometer and biaxial nanomechanical accelerometer was proposed. Polysilicon inertial masses were fabricated by optical lithography, dry etching under different masks and wet etching of sacrificial layer. We developed AFM-technique for determination of electrical parameters GaAs nanowires (NWs) , which does not require additional operations of NW fixation and allows one to estimate the resistivity and conductivity type of NW material. The obtained results can use to develop of the nanodiagnostic methods and the processes of formation of micro- and nanoelectronic elements based.

Determination of the electrical resistivity of vertically aligned carbon nanotubes by scanning probe microscopy

Techniques are developed to determine the resistance per unit length and the electrical resistivity of vertically aligned carbon nanotubes (VA CNTs) using atomic force microscopy (AFM) and scanning tunneling microscopy (STM). These techniques are used to study the resistance of VA CNTs. The resistance of an individual VA CNT calculated with the AFM-based technique is shown to be higher than the resistance of VA CNTs determined by the STM-based technique by a factor of 200, which is related to the influence of the resistance of the contact of an AFM probe to VA CNTs. The resistance per unit length and the electrical resistivity of an individual VA CNT 118 ± 39 nm in diameter and 2.23 ± 0.37 μm in height that are determined by the STM-based technique are 19.28 ± 3.08 kΩ/μm and 8.32 ± 3.18 × 10−4 Ω m, respectively. The STM-based technique developed to determine the resistance per unit length and the electrical resistivity of VA CNTs can be used to diagnose the electrical parameters of VA CNTs and to create VA CNT-based nanoelectronic elements.

The growth temperature effect on vertically aligned carbon nanotubes parameters

We studied the influence of the synthesis temperature on geometric parameters and structural perfection for vertically aligned carbon nanotubes (VACNT). We established that a synthetic temperature of 750 ◦C allows one to obtain the lowest concentration of defects in VACNT, with a diameter of 44±3 nm and a height of 80±9 nm. When temperature is increased up to 800 ◦C, an increase of the VACNT geometric dimensions

The influence of activation and growth time on the geometry and structural perfection of multi-walled carbon nanotubes

We studied the influence of the activation time on the phase composition and geometric parameters of catalytic centers (CC). We found, that the treatment of substrate in an ammonia atmosphere allows to restore oxidized nickel. The activation time and the presence of ammonia plasma do not affect the phase composition of catalyst, but has a significant effect on the geometric dimensions of catalytic centers. Also we studied the influence of growth time on the geometry and structure of vertically aligned carbon nanotubes (VACNT). When the growth time ranged from 5 to 15 min we observed the formation of new walls, which resulted in an increase of the outer diameter. Within the range of 15 to 30 minutes, however, there was a decrease in the diameter of carbon nanotubes, which is associated with the disturbance of structural perfection and disorientation of carbon nanotubes caused by wall undercutting in the plasma.

Investigation of the influence of geometric parameters of carbon nanotube arrays on their adhesion properties

The results of experimental studies of adhesion of carbon nanotube (CNT) arrays with different geometric parameters and orientations using atomic-force microscopy are presented. The adhesion values of CNT arrays were determined, which were from 82 to 1315 nN depending on the parameters of the array. As a result, it was established that the adhesion of a CNT array increases with an increase in branching and disorientation of the array, as well as with the growth of the aspect ratio of CNTs in the array.

Investigation of Effect of Geometrical Parameters of Vertically Aligned Carbon Nanotubes on their Mechanical Properties

In the work the results of experimental researches of geometric and mechanical parameters of vertically aligned carbon nanotubes (VACNT) by atomic force microscopy (AFM) and nanoindentation are presented. Here is also shown the influence of diameter and length of the carbon nanotube on the value of bending stiffness and Youngs modulus of nanotubes. The analysis of the experimental researches shows that the magnitude of bending stiffness significantly increases with the increasing of the diameter of the nanotubes and decreases with increasing length of the CNT. Diameter and length of the carbon nanotubes also have the most significant influence on Youngs modulus of CNTs. The obtained results can be used to develop the processes of formation of micro-and nanoelectronic elements based on the VACNT.