Electrical characterization of MIS diode prepared by magnetron sputtering

TiO2 thin film has been prepared on n-type Si wafer to fabricate an Au/TiO2/n-Si (MIS) diode by RF magnetron sputtering technique. The current-voltage (I-V) and capacitance-voltage (C-V) measurements of the diode have been performed over a wide range of temperatures (240-400 K) and frequencies (10 kHz-1 MHz), respectively. From I-V measurements, an abnormal increase in the barrier height (Φb) and a decrease in the ideality factor (n) with increasing temperature have been observed. This temperature dependence has been attributed to the barrier in homogeneities by assuming a Gaussian distribution (GD) of barrier heights at metal/semiconductor (M/S) interface. Both the conventional and modified Richardson plot show linearity. The activation energy (Ea), Richardson constant (A*) and Φb value have been calculated from the slope and intercept of the linear region. The obtained Richardson constant value of 113.82 A. cm-2. K-2 is in close agreement with the known value of 112 A.cm-2. K-2 for n-Si. The interface state density (Nss) and series resistance (Rs) of the diode has been obtained from the I-V measurements. In addition, the Φb value was determined from C-2-V characteristics. The obtained results indicate that the MIS diode with TiO2 interfacial insulator layer can be used in many device applications

CRTC Potentiates Light-independent timeless Transcription to Sustain Circadian Rhythms in Drosophila

Light is one of the strongest environmental time cues for entraining endogenous circadian rhythms. Emerging evidence indicates that CREB-regulated transcription co-activator 1 (CRTC1) is a key player in this pathway, stimulating light-induced Period1 (Per1) transcription in mammalian clocks. Here, we demonstrate a light-independent role of Drosophila CRTC in sustaining circadian behaviors. Genomic deletion of the crtc locus causes long but poor locomotor rhythms in constant darkness. Overexpression or RNA interference-mediated depletion of CRTC in circadian pacemaker neurons similarly impairs the free-running behavioral rhythms, implying that Drosophila clocks are sensitive to the dosage of CRTC. The crtc null mutation delays the overall phase of circadian gene expression yet it remarkably dampens light-independent oscillations of TIMELESS (TIM) proteins in the clock neurons. In fact, CRTC overexpression enhances CLOCK/CYCLE (CLK/CYC)-activated transcription from tim but not per promoter in clock-less S2 cells whereas CRTC depletion suppresses it. Consistently, TIM overexpression partially but significantly rescues the behavioral rhythms in crtc mutants. Taken together, our data suggest that CRTC is a novel co-activator for the CLK/CYC-activated tim transcription to coordinate molecular rhythms with circadian behaviors over a 24-hour time-scale. We thus propose that CRTC-dependent clock mechanisms have co-evolved with selective clock genes among different species.ope

Ruthenium(II) Complex Based Photodiode for Organic Electronic Applications

In this study, the electrical and photoresponse properties of a photovoltaic device with Ruthenium(II) complex interfacial thin film were investigated. Heteroleptic Ru(II) complex including bidentate and tridentate ligands thin film was coated on n-Si substrate by the spin coating technique. From current-voltage (I-V) measurements of an Au/Ru(II)/n-Si photodiode, it is observed that the reverse bias current under light is higher than that of the current in the dark. This indicates that the photodiode exhibits a photoconducting characteristic. The transient measurements such as photocurrent, photocapacitance and photoconductance were performed under various illumination conditions. These measurements indicate that the photodiode has a high photoresponsivity. The electrical parameters such as barrier height (I broken vertical bar(b)), ideality factor (n) and series resistance (R (s)) of the photodiode were determined from the analysis of I-V characteristics. Moreover, the capacitance/conductance-voltage characteristics of the photodiode highly depend on both voltage and frequency. Results show that the heterojunction can be used for various optoelectronic applications.King Khalid University under the (Research Center for Advanced Materials Science) at King Khalid University, Kingdom of Saudi Arabia [RCAMS/KKU/002-16]Authors would like to acknowledge the support of the King Khalid University for this research through a grant RCAMS/KKU/002-16 under the (Research Center for Advanced Materials Science) at King Khalid University, Kingdom of Saudi Arabia

On the interface states and series resistance profiles of (Ni/Au)-Al 0.22Ga0.78N/AlN/GaN heterostructures before and after 60Co (γ-ray) irradiation

The values of interface states (NSS) and series resistance (RS) of (Ni/Au)-Al0.22Ga0.78N/AlN/GaN heterostructures were obtained from admittance and current-voltage measurements before and after 250kGy 60Co irradiation. The analyses of these data indicate that the values of capacitance and conductance decrease, as the R S increases with increasing dose rate due to the generation of N SS. The increase in RS with increasing dose rate was attributed to two main models. According to the first model, it has been attributed to a direct decrease in the donor concentration in semiconductor material as a result of the elimination of shallow donor states. According to the second model, it is a result of irradiation because of the formation of deep acceptor centers in the semiconductor bulk, and electrons from the shallow donor centers are captured by these acceptors. © 2010 Taylor & Francis

Properties of AlN thin film as dielectric for Au/Ti/n-Si device

Abstract The purpose of this study is to investigate the electric and dielectric properties of Au/Ti/AlN/n-Si device with using admittance measurements. Aluminum nitride (AlN) epitaxial template on n-Si substrate was deposited by a hydride vapor phase epitaxy (HVPE) technique. Au/Ti contact was thermally evaporated on AlN thin film. Thus, admittance measurements (Y=G+iωC) of the fabricated device were performed and analyzed for frequencies ranging from 1 kHz to 1000 kHz and at room temperature. The capacitance-voltage (C-V) and conductance-voltage (G/ω-V) characteristics shown a strong frequency dependence. This behavior is associated with the reaction of the interface traps to the applied ac signal. Also, the dielectric parameters, conductivity, and electric modulus of the device were extracted from capacitance and conductance data. The obtained results suggest that the prepared device can be used as a capacitor in electronic circuits.</jats:p