Critical Threshold Voltage Research Articles

Ion concentration polarization near microchannel–nanochannel interfaces: Effect of pH value

This study investigates the effect of the pH value on the ion concentration polarization phenomenon and the nonlinear current-voltage characteristics of a hybrid soda-lime glass micro/nanochannel for a constant KCl salt concentration of about 1 mM. The experimental results show that the electrical conductance of the nanochannel in the Ohmic regime and the critical threshold voltage of the limiting current are both dependent on the pH value of the salt solution when the electrical double layer thickness is considerable in the nanochannel. Specifically, the nanochannel conductance increases and the critical threshold voltage for the limiting current decreases as the pH value is increased. It also suggests that a higher pH value induces a higher surface charge density on the nanochannel walls, and therefore increases both the ionic conductance and the counter-ion flux within the nanochannel.

Multi-Resistance States Through Electrically Driven Phase Transitions in $\hbox{VO}_{2}/\hbox{HfO}_{2}/\hbox{VO}_{2}$ Heterostructures on Silicon

We report on electrically induced multi-resistance states in VO2/HfO2/VO2 heterostructures on silicon at room temperature. Through geometric confinement, the critical threshold voltage for the transition in each VO2 layer can be tuned, and this leads to sharp current jumps as each layer undergoes a conductance transition. Consistent results are obtained in both voltage and current sweep conditions. The ability to realize variable resistance states in correlated oxide heterostructures fabricated on silicon could be of relevance to emerging information processing and storage schemes utilizing functional oxides.

Differential responses of human liver cancer and normal cells to atmospheric pressure plasma

When treated by atmospheric pressure plasma, human liver cancer cells (SK-HEP-1) and normal cells (THLE-2) exhibited distinctive cellular responses, especially in relation to their adhesion behavior. We discovered the critical threshold voltage of 950 V, biased at the electrode of the micro-plasma jet source, above which SK-HEP-1 started to detach from the substrate while THLE-2 remained intact. Our mechanical and biochemical analyses confirmed the presence of intrinsic differences in the adhesion properties between the cancer and the normal liver cells, which provide a clue to the differential detachment characteristics of cancer and normal cells to the atmospheric pressure plasma.

Conductive AFM microscopy study of the carrier transport and storage in Ge nanocrystalsgrown by dewetting

A combined conductive atomic force microscope (C-AFM)/scanning electronmicroscope (SEM) has been used to study the electric transport and retentionmechanisms through Ge nanocrystals (NCs). The NCs were formed by a two-stepdewetting/nucleation process on a silicon oxide layer grown on n-doped⟨001⟩ silicon substrate. Without preliminary e-beam irradiation, electric images areobtained only with bias voltages larger than 8 V. This is due to the barrier heightintroduced by the presence of the native oxide on NCs and of the oxide layeron which the NCs are grown. After acquisition of an e-beam-induced currentimage, electric images (e-beam off) can be easily obtained at low bias voltagesbecause of the trap creation in the oxide layer. We show that the critical thresholdvoltage to detect a current through the NCs decreases with NCs size. The banddiagram of the contact in the presence of a p-doped diamond coated tip showsthat the conduction mechanism is dominated by holes. At last we show a goodmemory effect with charge/discharge in the NCs resulting in a long retention time.

A Study of Trap Profiles in Thin Silicon Dioxide Films at Dielectric Breakdown Using Percolation Model

ABSTRACTA Monte Carlo simulation of wear-out process in thin silicon dioxide films is performed to investigate the correlation between the electron trap distribution and the dielectric breakdown. Non-uniformity of the trap generation and its dependence on the stress conditions are monitored by the measurements of the charge centroid. In order to include these experimental observations into Degraeve's percolation model [IEDM Tech. Dig., pp.863-866 (1995)], we introduce exponential trap profiles decaying from the Si/SiO2interface. Our new model successfully reproduces critical threshold voltage shifts from the information about critical charge centroids for various stress conditions. Finally, as a reasonable explanation of the stress dependent breakdown properties, we suggest that the bond strain caused by lattice mismatch at the interface is accelerated by the electric field.

Multiplexing the bistable boundary layer liquid crystal display

Shorter switching times in liquid crystal devices are traditionally achieved by raising the switching voltage. However, one of the limitations in multiplexing the boundary layer display is the necessity to keep the rms switching voltage Vs on the not-yet-selected pels below a critical threshold voltage Vth that would hold them in an asymmetric state and prevent switching. By using a periodic square wave to simulate a sequence of bipolar switching pulses, we show that their orienting effect in a ‘‘dual-frequency’’ liquid crystal can be prevented by simultaneously applying a voltage at a higher frequency where the dielectric anisotropy is negative. This permits Vs>Vth, and in principle allows faster multiplexing. The goal of increased speed was not achieved in our simulation experiment due to the inherently slow response of the dual-frequency material used. Nevertheless, the demonstrated scheme will be advantageous when faster dual-frequency materials are developed.

Electro-Hydrodynamic Instabilities in Main Chain Thermotropic Liquid Crystalline Polyesters

Abstract We have investigated the response behavior of the thermotropic nematic polymer, DDA-9, in an electric field. DDA-9 is composed of regularly alternating moieties and flexible spacers. At a critical threshold voltage, dependent on molar mass, these polymers show the onset of instability. The appearance of a (non-fluctuating) striped pattern (Williams domains) is shown and the time of formation and relaxation of these patterns is investigated as a function of applied Voltage.