Rajanish K. Kamat

Development of Ag/WO3/ITO Thin Film Memristor Using Spray Pyrolysis Method

The unique nonlinear relationship between charge and magnetic flux along with the pinched hysteresis loop in I-V plane provide memory with resistance combinations of attribute to Memristor which lead to their novel applications in non volatile memory, nonlinear dynamics, analog computations and neuromorphic biological systems etc. The present paper reports development of Ag/WO3/ITO thin film memristor device using spray pyrolysis method. The structural, morphological and electrical properties of the thin film memristor device are further characterized using x-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and semiconductor device analyzer. The memristor is simulated using linear dopent drift model to ascertain the theoretical and experimental conformations. For the simulation purpose, the width of doped region (w) limited to the interval [0, D] is considered as a state variable along with the window function characterized by the equation f (x) = w (1 − w). The reported memristor device exhibits the symmetric pinched hysteresis loop in I-V plane within the low operating voltage (±1 V).

Effect of surfactants on the data directionality and learning behaviour of Al/TiO2/FTO thin film memristor-based electronic synapse

The present communication deals with the development of the titanium dioxide (TiO2) thin films memristor using simple and cost effective hydrothermal route for neuromorphic application. The developed devices show pinched hysteresis loop in current-voltage (I-V) plane, which is the fingerprint characteristic of a memristor. Furthermore, current in the device continuously increases and decreases similar to synaptic weights of the biological neurons. The rectifying property similar to biological synapse is observed in the device which can be converted into the non-rectifying property by the suitable surfactant. The proper surfactant is responsible for the control of data flow in the memristor-based electronic synapse.

Modelling of nanostructured memristor device characteristics using Artificial Neural Network (ANN)

Abstract The present paper reports modelling of nanostructured memristor device characteristics using Artificial Neural Network (ANN). The memristor is simulated using linear drift model and data generated thereof is applied for learning, testing and validation of ANN architecture. In the present investigation we demonstrate optimum ANN architecture for the said modelling by varying the number of hidden neurons and percentage of testing data. The percentage of validation data is varied in order to accomplish tuning of the experiment. Performance of ANN architecture thus derived has been measured in terms of Mean Squared Error (MSE) and Pearson correlation coefficient (r). The hidden units consist of nonlinear sigmoid activation functions and training algorithm is based on a Levenberg–Marquardt Backpropogation method. The reported ANN architecture reveals best performance at lower numbers of hidden neurons and further lower percentage of testing and validation data. Additionally, optimized ANN structure is selected for modelling of other characteristics of memristor such as, flux-charge relation, time domain memristance and width of doped region. The results support, ANN as the preeminent tool for modelling of nonlinear devices such as memristor and the suite of other emerging nanoelectronics devices.

Structural and Optical Properties of Nanocrystalline TiO2 with Multiwalled Carbon Nanotubes and Its Photovoltaic Studies Using Ru(II) Sensitizers

In this study, the in situ sol–gel method has been deployed to prepare the titanium dioxide/multiwalled carbon nanotubes (TiO2/MWCNTs) nanocomposite (NCs) powders with varying content of MWCNTs (0.01–1.0 wt %), to construct the dye-sensitized solar cells (DSSCs). First, binder-free NCs were deposited on a transparent-conducting F:SnO2 (FTO) glass substrate by a doctor-blade technique and then anchored with Ru(II)-based dyes to either N719 or ruthenium phthalocyanine (RuPc). The structural and optical properties and interconnectivity of the materials within the composite are investigated thoroughly by various spectral techniques (XRD, XPS, Raman, FT-IR, and UV–vis), electron microscopy (HRTEM), and BET analysis. The experimental results suggest that the ratio of MWCNTs and TiO2 in NCs, morphology, and their interconnectivity influenced their structural, optical, and photovoltaic properties significantly. Finally, the photovoltaic performances of the assembled DSSCs with different content of MWCNTs to TiO2 films anchored with two different dyes were tested under one sun irradiation (100 mW/cm2). The measured current–voltage (IV) curve and incident photon-to-current conversion efficiency (IPCE) spectra of TiO2/0.1 wt % MWCNTs (T@0.1 C) for N719 dye show three times more power conversion efficiency (η = 6.21%) which is opposed to an efficiency (η = 2.07%) of T@0.1 C for RuPc dye under the same operating conditions.

Development of Virtual Reality Tool for Creative Learning in Architectural Education

One of the challenging tasks in engineering education is to bridge the gaps between imagination and real time problems of different engineering areas. The virtual reality (VR) can reduce this gap and also provides clear ideas on the basis of real time problems. The architectural education influenced and goes hand in hands for meeting these crucial challenges using advancements in computer technologies. In this research, we developed a VR tool for improving architectural design education. We explain VR tool as a value addition to the architectural education. The system is based on a general purpose computer, ceiling-mounted projector and passive glasses for Three Dimensional (3D) viewing. The presented work shows that virtual reality technology can considerably progress the efficiency learning by allowing young architects to apply theoretical knowledge to real world problems. In addition, it develops creativity, innovation, communication, problem solving approach, team-working and business skills. Development of Virtual Reality Tool for Creative Learning in Architectural Education

Area efficient time to digital converter (TDC) architecture with double ring-oscillator technique on FPGA for fluorescence measurement application

We present an area efficient Time to Digital Converter (TDC) yielding a high resolution of nearly 10ps. The TDC architecture reported in this paper comprises of coarse measurement using system clock and two controllable oscillators for fine resolution measurement. The reported improved resolution is attributed to the difference in their frequencies. One of the main features of the implementation is its prototyping on a low-cost FPGA.

Mimicking the Synaptic Weights and Human Forgetting Curve Using Hydrothermally Grown Nanostructured CuO Memristor Device

In the present investigation, we have fabricated copper oxide (CuO) thin film memristor by employing a hydrothermal method for neuromorphic application. The X-ray diffraction pattern confirms the films are polycrystalline in nature with the monoclinic crystal structure. The developed devices show analog memory and synaptic property similar to biological neuron. The size dependent synaptic behavior is investigated for as-prepared and annealed CuO memristor. The results suggested that the magnitude of synaptic weights and resistive switching voltages are dependent on the thickness of the active layer. Synaptic weights are improved in the case of the as-prepared device whereas they are inferior for annealed CuO memristor. The rectifying property similar to a biological neuron is observed only for the as-prepared device, which suggested that as-prepared devices have better computational and learning capabilities than annealed CuO memristor. Moreover, the retention loss of the CuO memristor is in good agreement with the forgetting curve of human memory. The results suggested that hydrothermally grown CuO thin film memristor is a potential candidate for the neuromorphic device development.

Bipolar resistive switching with coexistence of mem-elements in the spray deposited CoFe2O4 thin film

In the present investigation, we have experimentally demonstrated the bipolar resistive switching with the coexistence of three fundamental memelements in the Ag/CoFe2O4/FTO thin film metal-insulator-metal (MIM) device. The device shows the analog resistive switching behavior and charge transport follows the Ohmic and space charge limited conduction (SCLC) mechanisms. The device transforms from asymmetric to symmetric resistive switching when the SCLC conduction mechanism change to the Ohmic conduction mechanism at higher voltage sweep rates. It was observed that the I–V crossing location of MIM device shifted towards the higher voltage range with increasing voltage sweep rates for both bias regions due to the nanobattery effect. The significant tunneling gap between immature conductive filament(s) and percolation channels was responsible for the coexistence of memelements and nanobattery effect in the Ag/CoFe2O4/FTO thin film MIM device.

Learning by Simulations: A New and Effective Pedagogical Approach for Science, Engineering and Technology Students in a Traditional Setting

Using a pedagogic case study in a traditional learning environment, in this paper, the authors demonstrate how an innovative yet practical computer-based simulation of a complex nano device was an effective tool that improved the learning outcomes of academically less-prepared Bachelor of Nanoscience students in an undergraduate engineering course in a rural university. The authors’ case study presented in this paper strongly suggests that innovations in content delivery, and adaptive learning such as via simulations, can transform what it means to educate students in the 21st century. Learning by Simulations: A New and Effective Pedagogical Approach for Science, Engineering and Technology Students in a Traditional Setting

Coexistence of filamentary and homogeneous resistive switching with memristive and meminductive memory effects in Al/MnO2/SS thin film metal–insulator–metal device

In the present investigation, we have experimentally demonstrated the coexistence of filamentary and homogeneous resistive switching mechanisms in single Al/MnO2/SS thin film metal–insulator–metal device. The voltage-induced resistive switching leads to clockwise and counter-clockwise resistive switching effects. The present investigations confirm that the coexistence of both RS mechanisms is dependent on input voltage, charge-flux and time. Furthermore, the non-zero I–V crossing locations and crossovers hysteresis loops suggested that the developed device has memristive and meminductive properties. The memristive and meminductive memory effects are further confirmed by electrochemical impedance spectroscopy. The results suggested that the mem-device dynamics and electrochemical kinetics during different voltage sweeps and sweep rates are responsible for the coexistence of filamentary and homogeneous resistive switching mechanisms as well as memristive and meminductive memory effect in single Al/MnO2/SS metal–insulator–metal device. The coexistence of both RS effects is useful for the development of high-performance resistive memory and electronic synapse devices. Furthermore, the coexistence of memristive and meminductive memory effects is important for the development of adaptive and self-resonating devices and circuits.