Nonphotolithographic nanoscale memory density prospects

Technologies are now emerging to construct molecular-scale electronic wires and switches using bottom-up self-assembly. This opens the possibility of constructing nanoscale circuits and memories where active devices are just a few nanometers square and wire pitches may be on the order of ten nanometers. The features can be defined at this scale without using photolithography. The available assembly techniques have relatively high defect rates compared to conventional lithographic integrated circuits and can only produce very regular structures. Nonetheless, with proper memory organization, it is reasonable to expect these technologies to provide memory densities in excess of 10/sup 11/ b/cm/sup 2/ with modest active power requirements under 0.6 W/Tb/s for random read operations

Electrical Properties of Single-Walled Carbon Nanotube Networks Produced by Langmuir-Blodgett Deposition

This thesis investigates the use of the Langmuir-Blodgett (LB) deposition technique as a means for building up ultra-thin networks of single-walled carbon nanotubes (SWCNTs) on various substrates. Transfer from a water subphase is successfully demonstrated for a range of SWCNTs and the electrical properties of the networks are discussed in detail. In contrast to the majority of literature on LB networks of SWCNTs, transfer is completed without the addition of surfactants to the nanotube material. However, and as expected, improved deposition is achieved when SWCNTs are functionalised (through thermal oxidation) with carboxylic acid groups, decreasing their hydrophobicity. In-plane electrical data reveal preferential alignment of the nanotubes along the direction of dipping. Comprehensive studies of the current dependence on temperature and the field dependence of conductivity are presented for sorted metallic and semiconducting nanotubes in an attempt to reveal the dominant conduction mechanisms. For metallic nanotubes, typical metallic conductivity is observed with an increasing resistance with increasing temperature. The metallic nanotube temperature coefficient of resistance is 0.001/K. At high electricfield strengths (>10^6 V/m), conduction in semiconducting SWCNT networks is dominated by the Poole-Frenkel effect. Transistor structures are presented with SWCNTs as the active semiconducting layer. The best device shows p-type depletion mode behaviour with an on/offratio of around 8 and a carrier mobility of 0.3 cm^2/Vs

Carbon Nanoelectronic Heterodyne Sensors : A New Paradigm for Chemical and Biological Detection.

In 1959, in his famous talk ‘There is plenty of room at the bottom’, physicist Richard Feynman had envisaged a new era of science where one could build electronic systems which would sense and interact with a world only a few atoms in size. To build such systems we not only need new materials but also new transduction strategies. The hunt for new materials has led us back to carbon, a material known since antiquity. Carbon nanotube and graphene-two allotropes of carbon, possess structural, electronic, optical and mechanical properties perfect for building fast, robust and sensitive nano-systems. However, the available sensing technologies are still incapable of high fidelity detection critical for studying nanoscale events in complex environments like ligand-receptor binding, molecular adsorption/desorption, π-π stacking, catalysis, etc. In this thesis, I first introduce a fundamentally new nanoelectronic sensing technology based on heterodyne mixing to investigate the interaction between charge density fluctuations in a nanoelectronic sensor caused by oscillating dipole moment of molecule and an alternating current drive voltage which excites it. By detecting molecular dipole instead of associated charge, we address the limitations of conventional charge-detection based nanoelectronic sensing techniques. In particular, using a carbon nanotube heterodyne platform, I demonstrate for the first time, biological detection in high ionic background solutions where conventional charge-detection based techniques fail due to fundamental Debye screening effect. Next, we report the first graphene nanoelectronic heterodyne vapor sensors which can detect a plethora of vapor molecules with high speed (~ 0.1 second) and high sensitivity (< 1 part per billion) simultaneously; recording orders-of-magnitude improvement over existing nanoelectronic sensors which suffer from fundamental speed-sensitivity tradeoff issue. Finally, we use heterodyne detection as a probe to quantify the fundamental non-covalent binding interaction between small molecules and graphene by analyzing the real-time molecular desorption kinetics. More importantly, we demonstrate for the first time, electrical tuning of molecule-graphene binding kinetics by electrostatic control of graphene work function signifying the ability to tailor chemical interactions on-demand. Our work not only lays a foundation for next-generation of rapid and sensitive nanoelectronic detectors, but also provides an insight into the fundamental molecule-nanomaterial interaction.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111436/1/girishsk_1.pd

Multiple-valued logic: technology and circuit implementation

Title from PDF of title page, viewed March 1, 2023Dissertation advisors: Masud H. Chowdhury and Yugyung LeeVitaIncludes bibliographical references (pages 91-107)Dissertation (Ph.D.)--Department of Computer Science and Electrical Engineering. University of Missouri--Kansas City, 2021Computing technologies are currently based on the binary logic/number system, which is dependent on the simple on and off switching mechanism of the prevailing transistors. With the exponential increase of data processing and storage needs, there is a strong push to move to a higher radix logic/number system that can eradicate or lessen many limitations of the binary system. Anticipated saturation of Moore's law and the necessity to increase information density and processing speed in the future micro and nanoelectronic circuits and systems provide a strong background and motivation for the beyond-binary logic system. During this project, different technologies for Multiple-Valued-Logic (MVL) devices and the associated prospects and constraints are discussed. The feasibility of the MVL system in real-world applications rests on resolving two major challenges: (i) development of an efficient mathematical approach to implement the MVL logic using available technologies and (ii) availability of effective synthesis techniques. The main part of this project can be divided into two categories: (i) proposing different novel and efficient design for various logic and arithmetic circuits such as inverter, NAND, NOR, adder, multiplexer etc. (ii) proposing different fast and efficient design for various sequential and memory circuits. For the operation of the device, two of the very promising emerging technologies are used: Graphene Nanoribbon Field Effect Transistor (GNRFET) and Carbon Nano Tube Field Effect Transistor (CNTFET). A comparative analysis of the proposed designs and several state-of-the-art designs are also given in all the cases in terms of delay, total power, and power-delay-product (PDP). The simulation and analysis are performed using the H-SPICE tool with a GNRFET model available on the Nanohub website and CNTFET model available from Standford University website.Introduction -- Fundamentals and scope of multiple valued logic -- Technological aspect of multiple valued logic circuit -- Ternary logic gates using Graphene Nano Ribbon Field Effect Transistor (GNRFET) -- Ternary arithmetic circuits using Graphene Nano Ribbon Field Effect Transistor (GNRFET) -- Ternary sequential circuits using Graphene Nano Ribbon Field Effect Transistor (GNRFET) -- Ternary memory circuits using Carbon Nano Tube Field Effect Transistor (CNTFET) -- Conclusions & future wor

Current-Voltage characteristics of carbon Nanotube field effect transistor considering Non-Ballistic conduction

This thesis report is submitted in partial fulfillment of the requirements for the degree of Bachelor of Science in Electrical and Electronic Engineering, 2013.Cataloged from PDF version of thesis report.Includes bibliographical references (page 103-112).The need for technological advancement in the field of electronics has been ever increasing. Till now silicon has been the prime material of choice for meeting the current demands. However, silicon has its own limitations; Silicon based integrated circuits and the scaling of silicon MOSFET design faces complications like tunneling effect, gate oxide thickness effect etc. which has given the scope for new materials to emerge. The growing academic interest in carbon nanotubes (CNT) as a promising novel class of electronic material has led to significant progress in the understanding of CNT physics including ballistic and non-ballistic electron transport characteristics. In a nanotube, low bias transport can be nearly ballistic across distances of several hundred nanometers. Non-ballistic CNT transistors have been considered, and extended circuit-level models which can capture both ballistic and non-ballistic electron transport phenomenon, including elastic, phonon scattering, strain and tunneling effects, have been developed. The purpose of this paper is to establish a comparative analysis of the transport characteristics of ballistic and non-ballistic carbon nanotubes. The simulation is carried out using MATLAB and the main focus is on the changes in the I-V characteristic curves of elastic scattering effect, bandgap strain effect, tunneling effect and the overall combined effect, varying the parameters such as gate oxide thickness, temperature, dielectric constant, and chirality. The obtained results were then compared to their respective ballistic results. We verified our work by further comparison of our findings with other established academic papers published under the same category.Nirjhor Tahmidur RoufAshfaqul Haq DeepRusafa Binte HassanB. Electrical and Electronic Engineerin

Nanofluidic Pathways for Single Molecule Translocation and Sequencing -- Nanotubes and Nanopores

abstract: Driven by the curiosity for the secret of life, the effort on sequencing of DNAs and other large biopolymers has never been respited. Advanced from recent sequencing techniques, nanotube and nanopore based sequencing has been attracting much attention. This thesis focuses on the study of first and crucial compartment of the third generation sequencing technique, the capture and translocation of biopolymers, and discuss the advantages and obstacles of two different nanofluidic pathways, nanotubes and nanopores for single molecule capturing and translocation. Carbon nanotubes with its constrained structure, the frictionless inner wall and strong electroosmotic flow, are promising materials for linearly threading DNA and other biopolymers for sequencing. Solid state nanopore on the other hand, is a robust chemical, thermal and mechanical stable nanofluidic device, which has a high capturing rate and, to some extent, good controllable threading ability for DNA and other biomolecules. These two different but similar nanofluidic pathways both provide a good preparation of analyte molecules for the sequencing purpose. In addition, more and more research interests have move onto peptide chains and protein sensing. For proteome is better and more direct indicators for human health, peptide chains and protein sensing have a much wider range of applications on bio-medicine, disease early diagnoses, and etc. A universal peptide chain nanopore sensing technique with universal chemical modification of peptides is discussed in this thesis as well, which unifies the nanopore capturing process for vast varieties of peptides. Obstacles of these nanofluidic pathways are also discussed. In the end of this thesis, a proposal of integration of solid state nanopore and fixed-gap recognition tunneling sequencing technique for a more accurate DNA and peptide readout is discussed, together with some early study work, which gives a new direction for nanopore based sequencing.Dissertation/ThesisDoctoral Dissertation Physics 201

Investigation of Multiple-valued Logic Technologies for Beyond-binary Era

Computing technologies are currently based on the binary logic/number system, which is dependent on the simple on and off switching mechanism of the prevailing transistors. With the exponential increase of data processing and storage needs, there is a strong push to move to a higher radix logic/number system that can eradicate or lessen many limitations of the binary system. Anticipated saturation of Moore’s law and the necessity to increase information density and processing speed in the future micro and nanoelectronic circuits and systems provide a strong background and motivation for the beyond-binary logic system. In this review article, different technologies for Multiple-valued-Logic (MVL) devices and the associated prospects and constraints are discussed. The feasibility of the MVL system in real-world applications rests on resolving two major challenges: (i) development of an efficient mathematical approach to implement the MVL logic using available technologies, and (ii) availability of effective synthesis techniques. This review of different technologies for the MVL system is intended to perform a comprehensive investigation of various MVL technologies and a comparative analysis of the feasible approaches to implement MVL devices, especially ternary logic