Praveen Kumar Sahu

Ground bounce noise minimization using Multi-VDD Level Converter

In Multi-VDD system, Level Converter (LC) is used to convert one voltage level to another level (i.e. high to low and low to high). Power gating is an approach to reduce the dynamic and standby leakage in the present day System on Chip (SoC) design. As we go lower down the technology node problem of ground bouncing starts to dominate the system. It leads to various kinds of errors especially the functional ones. Here, we are using low to high level converter, whose output is used as an input signal to the sleep transistor (ST) in power gating technique to reduce the leakage current and Ground Bounce in circuit. This is achieved by reduction in the Virtual Ground (VGND) node voltage. Using this LC, VGND is maintained below the threshold voltage of ST, so that ST does not go in the saturation region. When ST is transitioning from sleep mode to active mode, small discharge current flows through the VGND node and thus limiting the bouncing. Using this technique, we have achieved 83% and 92% reduction in ground bounce and transition energy respectively as compared to conventional power gating technique. Simulations are carried out using 32-bit Ripple Carry Adder as low Vth logic circuit in Cadence Virtuoso simulation environment and UMC 0.18μm technology.

Sol–gel spin coating assisted room temperature operated nanostructured ZnO ethanol sensor with behavior transformation

AbstractIn this paper, zinc oxide (ZnO) thin film sensor has been fabricated using different sol–gel spin coating route to detect very low concentration (2 ppm) of ethanol vapors at room temperature (RT). The sensor shows appreciable response ~60% for 100 ppm of ethanol (C2H5OH) vapors at RT under humidity level ~55% RH. Various sensing parameters viz. % response, selectivity, stability, response/recovery time, repeatability, and reproducibility have been studied successfully. Structural and morphological properties have been studied via X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). XRD reveals the wurtzite structure of polycrystalline ZnO thin film. AFM, SEM, and TEM results confirm the wavy structure of well-shaped and slackly distributed ZnO nanograins with average particle size in range ~15–25 nm. The analyte sensing properties at room temperature can be ascribed to higher specific surface area due to nanograins formation. The significant effect of operating temperature on sensor’s performance is also analysed in order to obtain the optimum temperature (Topt) of the sensor device. Response reaches to 321.7% for 100 ppm of ethanol vapors at Topt (175 °C). The transformation in the behavior of sensing layer is observed which is described on the basis of experimental studies. HighlightsGrowth of nanostructured ZnO thin film sensor for ethanol detection using facile sol-gel spin coating technique.XRD, TEM, AFM and SEM are used for structural, topography and morphological properties analysis of the synthesized ZnO layer.Good sensitivity, selectivity, reproducibility and high stability observed towards ethanol detection at room temperature. Sensitivity is found to be improved multifold at higher temperatures.The transformation in the behavior of sensing layer is observed and explained on the basis of reducing and oxidizing byproducts formation upon ethanol exposure.

Fast grown self-assembled polythiophene/graphene oxide nanocomposite thin films at air–liquid interface with high mobility used in polymer thin film transistors

Successful practical application of a polymer or its nanocomposite depends on the ability to produce a high performance electronic device at a significantly lesser cost and time than those needed to manufacture conventional devices. Here, we present a facile and fast method for the self-assembly of a highly-orientated crystalline polymer nanocomposite thin film of poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] [PBTTT] and graphene oxide (GO) with large surface area at the air–liquid interface, which was assisted by the Floating Film Transfer Method (FTM). Prior to the fabrication of organic thin film transistors (OTFTs), the polymer nanocomposite thin film was studied using multiple techniques namely scanning electron microscopy (SEM), high resolution-transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED), atomic force microscopy (AFM), grazing incident X-ray diffraction (GIXD), electronic absorption, Fourier transformed-infrared (FT-IR) spectroscopy, and cyclic voltammetry (CV). The results are also compared to those of pristine polymer thin film. Further, the organic thin film transistors (OTFTs) fabricated using the polymer nanocomposite show better device performance featuring ∼0.112 cm2 V−1 s−1 field effect mobility and 103 on/off ratio in ambient conditions. Our study highlights a technique that allows fast growth of self-assembled high-quality nanocomposite thin films for enhanced device performance.

Synthesis of Na doped ZnO nano-particles for detection of reducing gases

This paper proposed a very facile method for 1 wt% Na doped Zinc Oxide (Na-ZnO) nanoparticles which have been synthesized through sol-gel method. These prepared nanoparticles have been characterized using scanning electron microscope (SEM), and Energy Dispersive Spectroscopy (EDS). Morphology of the film was analyzed by SEM which depicts the clustering of the nanoparticles which were calcined at 600 °C for 2 hr. and on other side Na doping in the ZnO nano-particles is validated by the EDS of the film having two major energy peaks for Zn and Na element. These synthesized nanoparticles are further used for fabrication of chemiresistor by drop casting method using methanol solvent. The pre-patterned gold electrode over alumina substrate is used to investigate the gas sensing capabilities of Na doped ZnO nanoparticles towards reducing gases such as H2, CO, LPG, ethanol, propanol etc. and also measured the transient response of the chemi-resistor toward ethanol gas. This chemi-resistor shows the remarkable sensing capability (∼72% sensitivity) with quick response (∼20 sec) and recovery time (∼50 sec) of ethanol gas at 3333 ppm concentration. Transient response of chemi-resistor with the exposure of ethanol gas shows the linear escalation in the sensitivity (from 11.76 to 72%) with the concentrations ranging from 833 to 3333 ppm.

Development of nanocrystalline ZnO-SnO 2 composite based platform for gas sensing applications

Nanocrystalline ZnO-SnO2 composite is synthesized incorporating xerogel route. The obtained xerogel undergoes calcination process at a higher temperature (600°C). X-ray diffraction characterization confirms the nanocrystalline growth of composite material. The average crystalline size obtained for ZnO and SnO2 composite metal oxides are 24 nm and 8.9 nm respectively. As obtained nanocrystalline composite powder is further used to fabricate the chemo resistor based gas sensor using simple fabrication techniques; where the active material is grown using brush coating over the pre-patterned gold electrodes. The fabricated chemo resistor based gas sensor is exquisitely sensitive and selective to Acetone rather than other test gases. Acetone having 1000 ppm concentration shows the maximum sensitivity of 84.60%, which is also cross sensitive with other reducing gases such as NH3, CH4, LPG, etc.