SnO_(2)-ZnO nanocomposite thin films:The influence of structure,composition and crystallinity on optical and electrophysical properties

SnO_(2)-ZnO thin films consisting of nanoscale crystallites were obtained on glass and silicon substrates by solid-phase low-temperature pyrolysis.The synthesized materials were studied by XRD and SEM methods,electrophysical and optical properties were evaluated,as well as the band gap was calculated.It was shown that regardless of the phase composition all films were optically transparent in the visible range(310-1000 nm).The nanocrystallites’minimum size,the highest activation energy of the conductivity and the smallest band gap calculated for indirect transitions were shown for a thin film 50SnO_(2)-50ZnO.It was assumed that the band gap decreasing might be attributed to the existence of surface electric fields with a strength higher than 4×10^(5)V/cm.

Influence of the aspect ratio of nitrogen-doped carbon nanotubes on their piezoelectric properties

Recent studies have shown that nitrogen doping of carbon nanotubes(CNTs)can lead to the formation of piezoelectric properties in them,not characteristic of pure CNTs.In this work,nitrogen-doped CNTs were grown by plasma-enhanced chemical vapor deposition and the effect of the aspect ratio of the nanotube length to its diameter on its piezoelectric coefficient d33 was shown.It was observed that as the aspect ratio of the nanotube increased from 7 to 21,the value of d33 increased linearly from 7.3 to 10.7 pm/V.This dependence is presumably due to an increase in curvature-induced polarization because of an increase in the curvature and the number of bamboo-like“bridges”in the nanotube cavity formed as a result of the incorporation of pyrrole-like nitrogen into the nanotube structure.The obtained results can be used in the development of promising elements of nanopiezotronics(nanogenerators,memory elements,and strain sensors).

Impact of laser pulse repetition frequency on nucleation and growth of LiNbO_(3)thin films

This paper reports the impact of the laser pulse repetition frequency on growth processes,morphological and electro-physical parameters of nanocrystalline LiNbO_(3)thin films obtained by the pulsed laser deposition technique.It was found that the nucleation process in LiNbO_(3)films could controllably change by increasing the laser pulse repetition frequency.The film obtained at the repetition frequency of 4 Hz consists of local islands and clusters with a diameter of 118.1±5.9 nm.Nanocrystalline films,grown at the repetition frequency of 10 Hz,possess a continuous granular structure with a grain diameter of 235±11.75 nm.Achieved results can be used for the development of promising“green”energy devices based on lead-free piezoelectric energy harvesters.

Titanium oxide artificial synaptic device:Nanostructure modeling and synthesis,memristive cross-bar fabrication,and resistive switching investigation

The paper shows the results of the mathematical model development and the numerical simulation of the oxygen vacancies,and the distribution of TiO,Ti_(2)O_(3),and TiO_(2)oxides in the titanium oxide nanostructure obtained by local anodic oxidation(anodization).The effect of the anodization voltage pulse duration and amplitude on the titanium oxide composition distribution and the conduction channel formation was shown.Synaptic device prototypes based on electrochemical titanium oxide are fabricated and investigated.It was shown that forming free resistive switching between the low resistances state(LRS)1.43±0.54 kΩand the high resistance state(HRS)28.75±9.75 kΩwere observed during 100,000 switching cycles and LRS 1.49±0.23 kΩwas maintained for 10,000 s.Multilevel resistive switching of the synaptic device prototype was investigated.It was shown that increasing Uset from 0.5 to 1.5 V leads to different LRS from 3.96±0.19 to 0.71±0.10 kΩ.The results obtained can be used in the development of technological foundations for the formation of high-performance multilevel artificial synapses for elements of neuroelectronics and hardware neural networks.

Ferroelectric solid solutions with perovskite- and columbite-type components: From structures formation to domain and hysteresis phenomena

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−x−y)NaNbO_(3)−xKNbO_(3)−yCdNb_(2)O_(6) system are manufactured at x=0.05-0.20 and y=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°domains(mechanical twins)in the solid solution with x=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.