O. I. Il’in

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.

Study of adhesion of vertically aligned carbon nanotubes to a substrate by atomic-force microscopy

The adhesion to a substrate of vertically aligned carbon nanotubes (VA CNT) produced by plasmaenhanced chemical vapor deposition has been experimentally studied by atomic-force microscopy in the current spectroscopy mode. The longitudinal deformation of VA CNT by applying an external electric field has been simulated. Based on the results, a technique of determining VA CNT adhesion to a substrate has been developed that is used to measure the adhesion strength of connecting VA CNT to a substrate. The adhesion to a substrate of VA CNT 70–120 nm in diameter varies from 0.55 to 1.19 mJ/m2, and the adhesion force from 92.5 to 226.1 nN. When applying a mechanical load, the adhesion strength of the connecting VA CNT to a substrate is 714.1 ± 138.4 MPa, and the corresponding detachment force increases from 1.93 to 10.33 μN with an increase in the VA CNT diameter. As an external electric field is applied, the adhesion strength is almost doubled and is 1.43 ± 0.29 GPa, and the corresponding detachment force is changed from 3.83 to 20.02 μN. The results can be used in the design of technological processes of formation of emission structures, VA CNT-based elements for vacuum microelectronics and micro- and nanosystem engineering, and also the methods of probe nanodiagnostics of VA CNT.

Analysis of modes of nanoscale profiling during ion-stimulated deposition of W and Pt using the method of focused ion beams

In this work the results obtained in experimental studies of conditions of the nanoscale profiling of a silicon substrate surface under the ion stimulation of W and Pt deposition by a Ga+ ion beam are represented. It is shown that, according to combinations of process conditions, deposition, or etching processes, conditions of the formation of transition structures can also be implemented. It is found that the rate of ionstimulated deposition of W and Pt averages 8 nm/min and 50 nm/min for ion-beam currents of 2.3 pA and 7.9 pA, respectively, and the rate of ion-beam etching of a silicon substrate is 6 nm/min and 55 nm/min for ion-beam currents of 2.3 pA and 111.4 pA respectively. With the use of these results, the modes are determined and a prototype of sensing element of tunnel accelerometer is formed using focused ion beams (FIBs). The results can be used to develop manufacturing methods of generating patterns of nano- and microelectronics and nano- and microsystem engineering on the basis of FIBs.

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 memristive behavior of non-uniform strained carbon nanotubes

The evolution of electronic devices creates a constant demand for the development of new technologies and of operation principles for non-volatile memory. One of the promising development directions in this area is the creation and investigation of memristor structures based on aligned carbon nanotubes (CNT). Previously, we have experimentally shown that vertically aligned CNTs exhibit a memristive switching associated with their strain and polarization [1–3]. Analysis of the literature [4–6] has shown that non-uniform strain in carbon nanostructures can lead to the appearance of a piezoelectric effect and the corresponding internal electric field in them. We put forward a proposal that the non-uniform strain of the CNT acts as an additional source of resistance which depends on the value of the current flowing. The application of an external electric field to the non-uniformly strained nanotube can lead to the redistribution of the strain and a reproducible switch of nanotube resistance. The aim of the research is to study a memristive behavior of carbon nanotubes at different non-uniform strain values.

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.