Time Dependence Of Capacitance Research Articles

Study of Randomly Distributed Charge Traps by Measuring Frequency- and Time-Dependence of a DNTT-Based MIS Capacitor

The frequency and time dependence of capacitance of dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT)-based metal-insulator-semiconductor (MIS) capacitors were studied. The frequency spectra show a long and gradual slope over many orders of magnitude in frequency, and the time evolution in the subthreshold region exhibits a logarithmic dependence. These two phenomena are analyzed from a unified point of view on the basis of charge trapping models that were originally developed for Si-based MIS capacitors. The charge trapping model with a Gaussian-distributed surface potential in DNTT successfully reproduces both the frequency and time dependences with the same parameter set.

Characteristics of conjugated hydrocarbon based thin film transistor with ionic liquid gate dielectric

Thin film transistors (TFTs) with ionic liquid gate dielectrics, [1-ethyl-3-methylimidazolium][bis(trifluoromethanesulfonyl)imide] (emim[TFSI]) and [1-butyl-3-methylimidazolium][hexafluorophosphate] (bmim[PF 6]), are fabricated with thin films of one dimensional (1D) hydrocarbon, [7]phenacene. P-channel characteristics are observed for [7]phenacene TFTs with both ionic liquids by use of platinum electrode. The field-effect mobility μ for [7]phenacene TFT with bmim[PF 6] was recorded to be 0.28 cm 2 V −1 s −1. The value of absolute threshold voltage, | V TH|, was less than 2.5 V, showing low-voltage operation. The accumulation of hole in the [7]phenacene TFTs with ionic liquids was confirmed from the voltage or time dependence of capacitance in metal–insulator-semiconductor structure, which shows that these TFTs operate electrochemically and the carriers are accumulated in the whole of [7]phenacene thin films.

COMPARATIVE STUDY ON THE ADSORPTION PROCESSES OF ALKANETHIOL AND ALKANEDITHIOL ON GOLD

The kinetics of formation of self-assembled monolayers on gold generated by the adsorption of 1-octanethiol and 1,8-octanedithiol were explored by electrochemistry measurement. The time dependence of capacitance and surface coverage supported that the adsorption of thiols typically processed with a two-step adsorption consisted of a fast initial adsorption and a slowly following reorganization. From the function of surface coverage versus time, one could get rate constants of adsorption of thiols, and the adsorption process was demonstrated to follow a diffusion-controlled Langmuir model. A comparison of the adsorption rates for different concentration between 1-octanethiol and 1,8-octanedithiol revealed that their adsorption processes were almost identical and independent on the concentration, inferring that only one sulfur atom contributed to the self-assembly of dithiol molecule.

Time Dependence of the Capacitance of a MOS Silicon Tunnel Diode under the Influence of Hydrogen

The results of theoretical and experimental investigations into the time dependence of the capacitance of MOS silicon diodes with a thin tunnel dielectric and a palladium field electrode under the influence of a gas hydrogen-containing mixture are presented. Analytical expressions are derived that describe the time dependence of the capacitance of the space charge region (SCR) of the MOS tunnel diode operating in depletion and enrichment regimes. It is demonstrated that the time dependence of the SCR capacitance of the MOS diode placed in the gas mixture is caused by diffusion of hydrogen atoms from the field electrode to the SiOx–n-Si interface. The relaxation time of hydrogen atom accumulation at the interface is 47 s for the diode with a SiOx layer thickness of ∼3.7 nm placed in the gas mixture with 0.3 vol.% of H2. It has been established that the flat band voltage and the SCR capacitance of the MOS diode change under the influence of the gas mixture due to the decreased density of surface acceptor states at the SiOx–n-Si interface, the increased positive charge density in the dielectric, and the decreased contact potential difference.

Theoretical and Experimental Studies on Retention Characteristics of Metal-Ferroelectric-Insulator-Semiconductor and Metal-Insulator -Ferroelectric-Insulator-Semiconductor Structures

AbstractRetention characteristics of Metal-Ferroelectric-Insulator-Semiconductor(MFIS) and Metal-Insulator-Ferroelectric-Insulator-Semiconductor(M-I-FIS) structures have been investigated both theoretically and experimentally. The simulated time dependence of capacitance for the MFIS has indicated that reducing currents through the ferroelectric and the insulator layers improves the retention characteristics more effectively than choosing the insulators with larger dielectric constants. The M-I-FIS structure has been studied in order to reduce the charge injection between the metal and the ferroelectric layer in the MFIS. The simulations have indicated that the M-I-FIS can provide much longer retention time than the original MFIS, although the experimental retention time of the M-I-FIS have almost the same as that of the MFIS.

Capacitive Transients During Freedericksz Transition in 7CB and 8CB

Abstract The dynamic behaviour around the electrically driven Freedericksz transition in the nematic liquid crystals 7CB and 8CB has been studied experimentally by measuring the time dependence of capacitance of a thin layer of planarly oriented sample. The initial parts of both growth and decay of capacitance in both samples are found to be exponential in nature. Beyond the initial exponential part, we find that in 7CB, close to the N-I transition, the decay of capacitance is oscillatory. The rotational viscosity coefficient γ1 has been determined from the decay rates of capacitance.