Ion Drift and Polarization in Thin SiO₂ and HfO₂ Layers Inserted in Silicon on Sapphire

To reduce the built-in positive charge value at the silicon-on-sapphire (SOS) phase border obtained by bonding and a hydrogen transfer, thermal silicon oxide (SiO2) layers with a thickness of 50–310 nm and HfO2 layers with a thickness of 20 nm were inserted between silicon and sapphire by plasma-enhanced atomic layer deposition (PEALD). After high-temperature annealing at 1100 °C, these layers led to a hysteresis in the drain current–gate voltage curves and a field-induced switching of threshold voltage in the SOS pseudo-MOSFET. For the inserted SiO2 with a thickness of 310 nm, the transfer transistor characteristics measured in the temperature ranging from 25 to 300 °C demonstrated a triple increase in the hysteresis window with the increasing temperature. It was associated with the ion drift and the formation of electric dipoles at the silicon dioxide boundaries. A much slower increase in the window with temperature for the inserted HfO2 layer was explained by the dominant ferroelectric polarization switching in the inserted HfO2 layer. Thus, the experiments allowed for a separation of the effects of mobile ions and ferroelectric polarization on the observed transfer characteristics of hysteresis in structures of Si/HfO2/sapphire and Si/SiO2/sapphire

Formation of nanocrystalline BaTiO3 thin films by pulsed laser deposition

The paper shows the experimental results of the substrate temperature effect on the morphological and electro-physical parameters of nanocrystalline BaTiO3 films fabricated by pulsed laser deposition. It was found increasing in the substrate temperature from 300 °C to 600 °C results in decreasing in surface roughness from (6.1±0.6) nm to (0.8±0.1) nm and increasing in the films grain size from (39.1±3.1) nm to (212.1± 17.2) nm. Increasing in the substrate temperature leads to a change in electro-physical parameters: the concentration of charge carriers increases from (1.85±0.16)×1013 cm-3 to (2.77±0.25)×1013 cm-3, the mobility of charge carriers decreases from (10.1±0.9) cm2/(V·s) to (7.2±0.6) cm2/(V·s), and the resistivity of the films changes insignificantly from (3.4±0.2)×103 Ω·cm to (3.1±0.2)×103 Ω·cm under increase in the temperature from 300 °C to 600 °C. The obtained results make it possible to get BaTiO3 films with target parameters, which can be used to develop promising lead-free energy harvesters for alternative energy devices

Study of high-speed interaction processes between fluoropolymer projectiles and aluminum-based targets

The experimental results and numerical modeling of penetration process of fluoropolymer projectiles in aluminum-based targets are presented. Analysis of mathematical models for interaction of elastoplastic projectile and target without taking additional energy released during interaction of fluoropolymer and aluminum into consideration is carried out. Energy fraction which is spent effectively on the increase in cavity volume is determined. The experimental and calculated results of penetration by combined and inert projectiles are compared

Ultrasensitive Detection of 2,4-Dinitrophenol Using Nanowire Biosensor

The method for the detection of 2,4-dinitrophenol (DNP) in solution is proposed. This method employs the sensors based on silicon nanowire field-effect transistors with protective layers of high-k dielectrics, whose surface is functionalized with an amino silane. Direct highly sensitive detection of DNP has been demonstrated, and the lowest detectable concentration of DNP was determined to be 10−14 M. Silicon-on-insulator nanowire (SOI-NW) sensors can well be employed for the rapid detection of a wide range of toxic and explosive compounds by selection of sensor surface modification techniques