Ayayi C. Ahyi

Evidence of negative bias temperature instability in 4H-SiC metal oxide semiconductor capacitors

Generation lifetimes and interface state densities of n-type 4H-SiC metal oxide semiconductor (MOS) capacitors are characterized by using the pulsed MOS capacitor technique. A decrease in lifetime and increase in interface state density occurs when the devices are negatively biased at 400°C. This behavior is consistent with an effect seen in Si∕SiO2 devices known as negative bias temperature instability. A portion of the lifetime degradation caused by this effect can be recovered by removing the negative bias as well as by positively biasing the device.

Temporal measurement on and using pulses from spectrally narrowed emission in styrylpyridinium cyanine dye

Highly efficient spectrally narrowed emission (SNE) was observed in the solution of strylpyridinium cyanine dye (SPCD) pumped by fundamental and second harmonic of a picosecond Nd:YAG laser in two separate arrangements. A highly directional emission was observed in both the pumping arrangements without incorporating any mirrors. The pulse duration of the SNE was measured by background free SHG intensity autocorrelation technique. The measured duration of the pulses was 40 ps. These pulses, having a spectral linewidth of 10 nm (full width at half maximum), were used as a probe to measure the transient changes in the transmission in SPCD solution using a pump–probe setup. The transient optical transmission indicated a gain at the overlap and no gain was observed beyond a delay of 40 ps.

Studies of DASMS, a novel organic salt with very large electro-optic coefficient

Summary form only given. Specific stilbazolium salts possess high electro-optic coefficients. The strong Coulomb interactions between charged molecules result in favorable alignment of the chromophores in the crystal enhancing the nonlinear optical effect. We have synthesized and prepared single-crystal thin-films of a novel organic salt, 4-dimethyl-amino-4-methylstilbazolium methanesulfonate (DASMS). X-ray diffraction and polarized UV-visible spectroscopic measurements were performed on the single-crystal films. An electro-optic modulator has been demonstrated by using the single-crystal thin-film of DASMS. The electro-optic coefficient of DASMS has been determined by field-induced birefringence measurements. As is discussed, a very large electro-optic coefficient has been observed for these novel thin-films.