Semicond. Physics Quantum Electronics & Optoelectronics, 2011, № 2

Dielectric and electro-optical properties of solutions of chemically modified fullerene С60 in nematic liquid crystal

Sat, 01 Jan 2011 00:00:00 GMT

Dielectric and electro-optical properties of solutions of chemically modified fullerene С60 in nematic liquid crystal Vovk, V.E.; Kovalchuk, O.V.; Gorishnyj, M.P.; Kovalchuk, T.M. Solutions of fullerene molecules С60 with chemically attached molecules of diamine (С60D) in planar oriented nematic liquid crystal (NLC) were obtained by only heating and ultrasonic processing. The С60D concentration changes from 0 up to 3.0 wt.%. Within the ranges of frequencies 10⁻¹ – 10⁶ Hz and temperatures 298-343 K, dielectric properties of solutions were investigated. It was shown that, at frequencies higher than 100 Hz, the frequency dispersion of the components of complex dielectric permittivity is absent. A value of conductivity of the solution was determined. It was also shown that the activation energy for the temperature dependence of the conductivity in nematic and isotropic phases does not depend on the concentration of molecules С60D. Obtained and explained were the reasons of the nonmonotonic conductivity dependence of solutions on the concentration of С60D molecules. For frequencies lower than 100 Hz, the dispersion of the components of complex dielectric permittivity is observed. It was shown that the dispersion can be described by the Debye equation. The temperature dependence of a value inverse to the relaxation time correlates with the temperature dependence of conductivity. Presence of С60D molecules in NLC tends to increasing the voltage for the Frederiksz transition. Made was the assumption that this effect may be explained by increase in viscosity of NLC as a consequence of aggregation of fullerene molecules.

Structural properties of nanocomposite SiO₂(Si) films obtained by ion-plasma sputtering and thermal annealing

Sat, 01 Jan 2011 00:00:00 GMT

Structural properties of nanocomposite SiO₂(Si) films obtained by ion-plasma sputtering and thermal annealing Bratus, O.L.; Evtukh, A.A.; Lytvyn, O.S.; Voitovych, M.V.; Yukhymchuk, V.О. The nanocomposite SiO₂(Si) films containing Si nanoclusters inside insulating SiO₂matrix are promising for many nanoelectronics applications. The ion-plasma sputtering of Si in O₂ containing gas mixture and following thermal annealing have been used to form nanocomposite SiO₂(Si) films. The structural properties of the obtained films have been studied using several methods. Among them, there were ellipsometry, IR spectroscopy, Raman spectroscopy, and AFM. Transition of SiOx matrix into insulating SiO₂ matrix has been revealed by IR spectroscopy. The shift of the transmittance spectra toward high frequency region and the increase in their intensity have been observed. The existence of amorphous and nanocrystalline phases into SiO₂(Si) films have been confirmed using Raman spectroscopy. Two material phases on the film surface, namely SiO₂ and Si, and surface density of silicon nanoclusters have been determined using AFM. It was shown that the size of silicon nanoclusters and their surface density depend on the level of enrichment with silicon of the initial SiOx film after ion-plasma sputtering and the temperature of subsequent annealing.

Electrical properties of MIS structures with silicon nanoclusters

Sat, 01 Jan 2011 00:00:00 GMT

Electrical properties of MIS structures with silicon nanoclusters Bunak, S.V.; Ilchenko, V.V.; Melnik, V.P.; Hatsevych, I.M.; Romanyuk, B.N.; Shkavro, A.G.; Tretyak, O.V. The theoretical and experimental investigations of electrical properties of the Al-SiO₂-( − ncsSi -SiO₂-Si structures grown using high temperature annealing SiOx, x < 2, have been carried out. It has been experimentally found that the Al-SiO₂-( − ncsSi )-SiO₂-Si structures with the tunnel dielectric layer revealed the effect of dynamic memory. Electric properties and parameters of the interface states located between − ncsSi and SiO₂ were studied in detail by measuring of current-voltage, capacitance-voltage, and thermally stimulated current characteristics.

Impact of sidewall spacer on gate leakage behavior of nano-scale MOSFETs

Sat, 01 Jan 2011 00:00:00 GMT

Impact of sidewall spacer on gate leakage behavior of nano-scale MOSFETs Rana, A.K.; Chand, N.; Kapoor, V. Semiconductor devices with a low gate leakage current are preferred for low power application. As the devices are scaled down, sidewall spacer for CMOS transistor in nano-domain becomes increasingly critical and plays an important role in device performance evaluation. In this work, gate tunneling currents have been modeled for a nano-scale MOSFET having different high-k dielectric spacer such as SiO₂, Si₃N₄, Al₂O₃, HfO₂. The proposed model is compared and contrasted with Santaurus simulation results and reported experimental result to verify the accuracy of the model. The agreement found was good, thus validating the developed analytical model. It is observed in the results that gate leakage current decreases with the increase of dielectric constant of the device spacer. Further, it is also reported that the spacer materials impact the threshold voltage, on current, off current, drain induced barrier lowering and subthreshold slope of the device.