Showing papers presented at "International Conference on Nanotechnology in 2009"

Silicon nanowire transistor with a channel width of 4 nm fabricated by atomic force microscope nanolithography

Abstract: The emergence of an ultrasensitive sensor technology based on silicon nanowires requires both the fabrication of nanoscale diameter wires and the integration with microelectronic processes. Here we demonstrate an atomic force microscopy lithography that enables the reproducible fabrication of complex single-crystalline silicon nanowire field-effect transistors with a high electrical performance. The nanowires have been carved from a silicon-on-insulator wafer by a combination of local oxidation processes with a force microscope and etching steps. We have fabricated and measured the electrical properties of a silicon nanowire transistor with a channel width of 4 nm. The flexibility of the nanofabrication process is illustrated by showing the electrical performance of two nanowire circuits with different geometries. The fabrication method is compatible with standard Si CMOS processing technologies and, therefore, can be used to develop a wide range of architectures and new microelectronic devices.

Experimental, modeling and simulation studies of nanoscale resistance switching devices

Abstract: Excellent resistance switching properties such as fast switching time ( 106), good retention (> 6 years) and endurance (> 105) are observed in nanoscale amorphous silicon based RRAM (resistive random access memory). To successfully integrate the RRAM array, circuit models of the device characteristics and effects of device configuration such as crosstalk between cells within the array need to be elucidated. To this end, we performed experiments on the junction configuration and device modeling to predict the device behavior and 3D electric field simulation to predict the effect of the switching medium thickness in terms of crosstalk during the writing process.

Exploiting memristance in adaptive asynchronous spiking neuromorphic nanotechnology systems

Abstract: In this paper we show that Spike-Time-Dependent-Plasticity (STDP), a powerful learning paradigm for spiking neural systems, can be implemented using a crossbar memristive array combined with neurons that asynchronously generate spikes of a given shape. Such spikes need to be sent back through the neurons input terminal. The shape of the spikes turns out to be very similar to the neural spikes observed in biology for real neurons. The STDP learning function obtained by combining such neurons with memristors is exactly that of the STDP learning function obtained from neurophysiological experiments on real synapses. Using this result, we propose memristive crossbar architectures capable of performing asynchronous STDP learning.

Nanoparticles of activated natural zeolite on textiles for protection and therapy

Abstract: Activated natural zeolite clinoptilolite is microporous hydrated aluminosilicates crystals with well-defined structures containing AlO4 and SiO4 tetrahedral linked through the common oxygen atoms. It is to point out that zeolites act as strong adsorbents and ion-exchangers but having many other useful properties. Zeolites are nontoxic substance, excellent for UVR and microbes protection, for proteins and small molecules such as glucose adsorption. Due to its cationexchange ability, zeolites have catalytic properties and for that multiple uses in medicine and industry, agriculture, water purification and detergents. The present paper is an attempt to modify cotton and polyester fabrics for summer clothing with addition of natural zeolite nanoparticles for achieving UV and antibacterial protective textiles. For this purpose cotton fabrics were mercerized and polyester fabrics modified by alkaline hydrolysis and by EDA (ethylenediamine) aminolysis. Zeolite in this paper refers to activated particles of clinoptilolite, with some fraction of nanoparticles produced by tribomechanical processing in the patented machine.

Manufacturing pathway and associated challenges for nanoscale computational systems

Abstract: We propose one possible manufacturing pathway for realizing nanodevice based computational fabrics that combines self-assembly based techniques with conventional photolithography. This pathway focuses on realizing the fabric as a whole including assembly of nanostructures, functionalization of devices, contacts and interconnects. Furthermore, this pathway is scalable to large systems, as multiple devices are created simultaneously in a self-aligning process step. We discuss the key sequence of steps for achieving nanoscale computational systems using the example of a simple digital logic circuit, and review the associated challenges involved for each of these.

Layer-by-layer coating of photoactive polymers for biomedical applications

Abstract: The design of advanced, nanostructured materials at the molecular level is of tremendous interest for the scientific community because of their potential in several fields, including medicine, biology and tissue engineering. Layer-by-layer (LbL) assembly is a versatile technique for the realization of multilayered films with tailored characteristics at the nanometer scale. Photoactive nanostructured films were prepared by LbL assembly of photozymes: an amphiphilic zwitterionic copolymer, poly(sodium styrene sulphonate-stat-vinyl naphtalene-stat-3-dimethyl(methacryloylethyl) ammonium propane sodium sulfonate) (PSSS-stat-VN-stat-DMPAS; code: ZI), and a cationic polyelectrolyte, chitosan-g-fluorescein (code: CHFL), on a crosslinked gelatin substrate. Although successful LbL assembly of photozymes was proven by the performed characterization, gelatin was not an optimal substrate for the coating, due to its low charge density and amphoteric nature. A regular growth of the layers was found after at least 6 layers were deposited. The macromolecules of the zwitterionic photozyme adopted a coiled micellar conformation in solution which was kept during the assembly. The obtained nanostructured films are promising candidates for carrying out efficient electron transfer process within them, responsible for the anti-microbial activity and the osteointegration ability of the coating.

A technology aware magnetic QCA NCL-HDL architecture

Abstract: Magnetic Quantum Dot Cellular Automata (MQCA) have been recently proposed as an attractive implementation of QCA as a possible CMOS technology substitute. Marking a difference with respect to previous contributions, in this work we show that it is possible to develop and describe complex MQCA computational blocks strongly linking technology and having in mind a feasible realization. Thus, we propose a practicable clock structure for MQCA baptised “snake-clock”, we stick to this while developing a system level Hardware Description Language (HDL) based description of an architectural block, and we suggest a delay insensitive Null Convention LogicTM (NCL, [1]) implementation for the magnetic case so that the “layout=timing” problem can be solved. Furthermore we include in our model aspects critically related to technology and real production, that is timing, power and layout, and we present the preliminary steps of our experiments, the results of which will be included in the architecture description.

Carbon based nanomaterial composites in RAM and microwave shielding applications

Abstract: This work deals with the design of electromagnetic absorber of interest in radar absorbing material (RAM) and microwave shielding systems. This absorber is based on a multilayer structure and the parameters taken into account are: number of layers, absorption maximization, microwave angle of incidence and frequency band. Design and optimization of the absorber are carried out using a Genetic Algorithm (GA) and are based on actual electrical parameters values. Such stochastic method leads to the best trade off between absorption properties and structure thickness, minimizing both the reflection coefficient (RC) and the global multilayer thickness (Thick). All the (carbon based) dielectric materials adopted in GA have been characterized as a function of frequency beforehand and their characteristic impedances inserted in a data base (DB) to be available during design stage. In particular, employed materials consist of epoxy resin reinforced with three different carbon species: micro sized granular graphite, single walled carbon nanotubes (SWCNT) and carbon nanofibers (CNF). The morphology of the multilayer structures is fixed a priori, — i.e., composite material type and its location in the multilayer structure is given — and the stochastic optimization procedure can only decide the best thickness of each layer. Main goals have been achieved and the possibility of realizing a quasi-perfect microwave absorber through graphite and nanomaterials has been demonstrated.

A technology aware magnetic QCA NCL-HDL architecture

Abstract: Magnetic Quantum Dot Cellular Automata (MQCA) have been recently proposed as an attractive implementation of QCA as a possible CMOS technology substitute. Marking a difference with respect to previous contributions, in this work we show that it is possible to develop and describe complex MQCA computational blocks strongly linking technology and having in mind a feasible realization. Thus, we propose a practicable clock structure for MQCA baptised “snake-clock”, we stick to this while developing a system level Hardware Description Language (HDL) based description of an architectural block, and we suggest a delay insensitive Null Convention LogicTM (NCL, [1]) implementation for the magnetic case so that the “layout=timing” problem can be solved. Furthermore we include in our model aspects critically related to technology and real production, that is timing, power and layout, and we present the preliminary steps of our experiments, the results of which will be included in the architecture description.

Single cells electrical characterizations using nanoprobe via ESEM-nanomanipulator system

Abstract: We perform electrical characterization on single cells using dual nanoprobe through environmental scanning electron microscope (ESEM)-nanomanipulator system. The ability to characterize the electrical property of single cells can be used as a novel method for cell viability detection in a quantitative and fast manner. The nanoprobe has been successfully fabricated using focused ion beam (FIB) tungsten deposition and etching processes. The characteristics of the nanoprobe have been examined from the energy dispersion spectrometry (EDS) and noise analyses. In this paper, for the first time, the electrical property of single cells under their native condition was presented. In order to realize this method for cell viability detection, two types of cells were used, i.e. dead cells and live cells. The results showed that there is a significant different on the electrical measurement data between dead and live cells.

Nanoscale reconfigurable computing using non-volatile 2-D STTRAM array

Abstract: In this paper, we investigate the combination of a novel computing paradigm referred to as Memory Based Computing (MBC) and an emerging non-volatile nanoscale memory technology, namely Spin-Torque Transfer Random Access Memory (STTRAM), to build a reconfigurable nanocomputing framework with high integration density, robustness and energy-delay efficiency. MBC uses a 2-D memory array as underlying computing element. Noting the read-dominant access pattern in MBC, we optimize the STTRAM cells to increase the energy-delay efficiency. Further, exploiting the asymmetric nature of the cells, we introduce the notion of preferential storage which optimizes the cell performance for ‘1’ over ‘0’ and skew the LUT content toward ‘1’ for improved energy-delay product (EDP).

Fabrication of memristors with poly-crystalline silicon nanowires

Abstract: Memristors are the two-terminal components that complete the symmetry between the fundamental circuit variables, and they are highly suitable for bioinspired and neural-network-based computational systems due to their inherent memory effect. In this paper we present a fabrication technique that uses only Complementary Metal Oxide Semiconductor (CMOS) processing steps and conventional photolithography, yielding poly-crystalline silicon nanowires that show a memristive behavior. Besides measurements, we performed numerical device simulations that address the observed memristive effect.

Single cell injection using nano pipette via nanorobotic manipulation system inside E-SEM

Abstract: In this work, a nano injection system for single cell with small size (diameter: ~5 μm) is proposed. An environmental scanning electron microscope (E-SEM) nanorobotic manipulation system has been constructed with three units and seven degrees of freedom (DOFs) in total. It can provide a real-time observation with nanoscale resolution during the experiment. Micro pulling and FIB etching are used to control the tip size of nano pipette accurately. In situ penetration of single wild-type yeast cell (W303) is performed using nano pipette inside the E-SEM based on the nanorobotic manipulation system. Spouting experiment of Rhodamine 6G fluorescent solutions at femtoliter level from nano pipette is also achieved under the E-SEM environment. The results show that it is possible to perform small single cell injection using nano pipettes inside the E-SEM.

A gas sensing system for indoor air quality control and polluted environmental monitoring

Abstract: The objective of this work is to develop a miniature electronic nose (E-nose) to detect the poisonous organic vapors in the indoor. A novel bio-chemical surface-acoustic-wave array with multiplexed oscillator and readout electronics was developed and tested. The sensor array was fabricated on a 128° YX LiNbO3 sensing substrate. On the surface of this substrate, an interdigital transducer (IDT) was made with a Cr/Au film as a metallic structure. The center frequency of the sensing chips was designed at 99.8 MHz. Seven polymers, Poly-4-vinylphenol (P4VP), Poly-vinylacetate (PVAc), poly-N-vinylpyrrolidone (PNVP), Polyethyleneglycol (PEG), Polystyrene (PS), polystyrene-co-maleic anhydride (PSMA), and Polysulfone (PSu), were coated on the sensing area of Au surface between the center of the IDTs. The 2 × 2 non-continuous SAW array could be controlled by a multiplexing technique and sensor signals were obtained by readout electronics with an 89C51 microprocessor. Five different organic vapors were adopted as samples to test the developed system. The frequency shifts (Af) were measured and the stable state was about 1 kHz. Two-way hierarchical clustering analysis was used to analyze the measured data. It showed that based on the analysis method, gases and polymers with similar chemical properties were grouped into the same family. The results suggest that the designed miniature e-nose and the applied analysis method are promising for practical applications of gas detection and recognition.

The influence of thermal process on electrical conductivity of microstructures: Made by ink-jet painting with the use of ink containing nano sized silver particles

Abstract: The features of the ink containing nano silver sized particles for inkjet printing is presented. After structures printing on substrate, to obtain good electrical conductivity, sintering process is necessary. It was proved, that during heating process, the burning type reaction take place and for this process activation energy of about 1 eV is necessary. This reaction takes important role in electrical resistance decreasing. After sintering process, the conductive structures have typical metallic type properties with TCR of 2080 ppm/K.

Vertically aligned carbon nanotubes on copper substrates for applications as thermal interface materials: From synthesis to assembly

Abstract: One promising application of CNTs in microelectronics is to use vertically aligned CNT (VACNT) arrays as novel thermal interface materials (TIMs). CNTs have high intrinsic thermal conductivity, a combination of flexibility and rigidity, small coefficient of thermal expansion and high thermal and chemical stability, etc. However, large interfacial thermal resistance between CNTs and contact substrates has been found and become the main barrier against VACNT application as TIMs. Basically, there are two VACNT TIM/substrate interfaces in a typical TIM assembly: the VACNT/growth substrate interface and the VACNT/mating substrate interface. In terms of the growth substrate, given the high temperature required (typically > 600 °C) for VACNT syntheses, direct synthesis of a VACNT TIM layer on the backside of a silicon chip is not compatible with current electronic packaging systems. Instead, VACNT synthesis on the copper lid surface is preferred. However, VACNT synthesis on bulk copper substrates has for long been a big challenge. In this study, we delivered a remarkable progress on fast synthesis of high-quality VACNTs on bulk copper substrates by introducing a well-controlled conformal alumina layer as the support layer for VACNT synthesis. The key roles of the support layer were discussed. As for reducing the contact thermal resistance at the VACNT/mating substrate interface, a chemical anchoring process using molecular phonon coupler (MPC) was developed. A proper MPC was chosen to covalently bond the VACNTs to the Si substrate surface and, therefore, to enhance interfacial thermal transport. Experimental results indicated that such an interface modification improved the effective thermal diffusivity of the carbon nanotube-mediated thermal interface by an order of magnitude and the equivalent thermal conductivity by two orders of magnitude, compared with other VACNT assembling processes. This remarkable breakthrough undoubtedly provides a viable commercial VACNT application for thermal management in microelectronic and photonic packaging, and opens up a new field in the design of CNT/substrate interfaces.

Exploring spray technology for the fabrication of organic devices based on poly(3-hexylthiophene)

Abstract: In order to fully exploit the potential of polymer electronics, large-area/low-cost processing technologies are necessary. In this paper, we investigate the feasibility of air atomizing spray technology for large-area/low-cost fabrication of organic electronic and optoelectronic thin-film devices based on solution-processable polythiophene derivatives. For this purpose an airbrush coating system was implemented and two main classes of organic devices were fabricated, organic photodetectors (OPD) and organic thin-film transistors (OTFT). Electrical and electro-optical characteristics, as well as film morphology and roughness of spray coated devices were compared to those of spin coated ones fabricated with similar structure. Although films deposited by spray coating show a considerably higher surface roughness and lower overall homogeneity, the spray-coated devices are capable of achieving performances comparable to the spin-coated ones.

NDR based threshold logic fabric with memristive synapses

Abstract: In recent years, many researchers have proposed the usage of molecular scale devices exhibiting negative differential resistance (NDR) in the realization of programmable logic circuitry. This paper deals with the utilization of one such system built from NDR based circuitry, specifically the Goto pair, in the implementation of a programmable threshold logic array (PTLA). Furthermore, the PTLA considered here uses memristors exhibiting multiple levels of resistance to provide weighted inputs to each threshold gate. Circuit level considerations for the Goto pair to be implemented as part of PTLA are discussed. An image classification application is also implemented using the proposed PTLA and simulated for functionality and performance using Cadence Spectre.

Analysis of keratinocytes stiffness after desmosome disruption using Atomic Force Microscopy based nanomanipulation

Abstract: Desmosomes are cell-cell junctions that provide mechanical strength for cells and maintain integrity of tissues in animal skins and hearts. Disruption of the desmosome like in some autoimmune diseases will therefore change the mechanical property of the anchoring cells and causing blistering. In the paper, we used Atomic Force Microscopy (AFM) to visualize the keratinocytes intercellular structure. The AFM based nanomanipulation system is employed to perform the nanoindentation experiment for measuring keratinocytes nanomechanical property under both physiological and pathophysiological conditions. Our demonstration of the use of AFM for in situ imaging and nanomanipulation for quantifying stiffness in nanoscale can facilitate the investigation of diseases related to blistering and development of therapeutic strategies accordingly.

Controlled nanostructuration of catalyst particles for carbon nanotubes growth

Abstract: We report on a novel method based on a plasma pre-treatment for controlled nanostructuration and patterning of iron catalyst particles from a continuous film in view of carbon nanotube growth. The effects of the hydrogen plasma conditions on the diameter and the density of the catalyst nanoparticles was studied and discussed. We were then able to propose a comprehensive mechanism for the metallic nanostructuration. We showed that as the plasma power density increases, first a reduction of the iron nanoparticle size is observed followed by for the highest plasma powers a phenomenon of alteration in the deposited film. A better control of the nucleation process and the nanostructuration were observed for low hydrogen pressures. The correlation between the plasma parameters and the obtained iron nanoparticles was established. The growth of carbon nanotubes (CNTs) was carried out on the patterned catalyst nanoparticles under CH4/H2 microwave plasma. High quality double-walled and multi-walled CNTs of a diameter of about 5 nm have be obtained.

Effect of silver and titanium dioxide nanoparticles on PCR efficiency

Abstract: Interaction between nanomaterials and biological systems and the role nanomaterials play in biochemical reactions is of great interest nowadays due to the unique properties of nanomaterials and their potential applications in Biomedical Engineering. Recently, nanoparticle PCR research has attracted more attention. However, research has been focused on gold nanoparticles exclusively and there is no work about the effect of other nanoparticles reported yet. In this work, the effect of silver nanoparticles (AgNPs) and titanium dioxide nanoparticles (TiO2NPs) is evaluated using a real-time PCR machine. It is found that AgNPs start to cause PCR inhibition at 30 μg/mL. TiO2NPs exhibit much stronger inhibitory effect. They start to cause PCR inhibition at 0.8 μg/mL. When different amounts of AgNPs and TiO2NPs are added to PCR solution, some interesting phenomenon is observed. The effect of the combination of AgNPs and TiO2NPs is not simply the linear combination of the effect of individual AgNPs and TiO2NPs. However, by choosing the combination of AgNPs and TiO2NPs, PCR inhibition can be minimized. The observations suggest that a complex interaction mechanism exists between AgNPs and TiO2NPs.

How much input vectors affect nano-circuit's reliability estimates

Abstract: As the sizes of (nano-)devices are aggressively scaled deep towards the nanometer range, the design and manufacturing of future (nano-)circuits will become extremely complex and inevitably introduce more defects, while their functioning will be adversely affected by (transient) faults. Therefore, accurately calculating the reliability of future designs will become a very important factor for (nano-)circuit designers as they investigate several alternatives for optimizing the tradeoffs between the conflicting metrics of area-power-energy-delay versus reliability. This paper studies the effect of the input vectors on the (nano-)circuit's reliability, and introduces a time-efficient method for quickly and accurately identifying the lower/upper reliability bounds. Simulations results support the claim that the absolute difference between the lowest and the highest achievable reliability is of one-to-two orders of magnitude. Therefore, future designs should consider the worst case input vector(s) in order to guarantee the required reliability margins.

Carbon nanotube bundles as nanoscale chip to package interconnects

Abstract: The paper presents recent advances in carbon nanotube interconnect modeling, with focus on their application to nanoscale chip packaging. An enhanced electrical model of carbon nanotube bundles is used, able to take into account the effects of different nanotube sizes covered by this application. The use of carbon nanotubes as chip to package interconnects at nanoscale dimensions is analyzed and the electrical parasitics introduced by these interconnects are compared to those predicted by other packaging technologies.

Influence of the composition of MWCNTs layers on the properties of strain gauges

Abstract: Strain gauges based on multi-walled carbon nanotubes (MWCNTs) realize a higher sensitivity and a larger operation range than usual metallic strain gauges. Different technologies for CNT-layers have been realized. With the aim to find a suitable technology that allows the application of CNT strain gauges without use of adhesives. For this purpose two detergents (SDS: Sodium Dodecyl Sulfate and DOC: Deoxycholic Acid) and one polymer composite (PEO: Polyethylene Oxide) were used to manufacture CNT strain gauges. The I–V characteristics of all strain gauges are linear between 0V and 5V. The resistance change versus strain shows a quadratic behavior, so that sensitivity increases with applied strain. Therefore all SDS-CNT, DOC-CNT and PEO-CNT composite strain gauges show a linear dependence of the sensitivity factor on strain. With a much higher MWCNT concentration the PEO-MWCNT strain gauges reaches a higher sensitivity factor between 7 and 13. The average sensitivity factor of DOC-CNT strain gauges is by 7.5.

Polyol mediated synthesis & characterization of Cu nanoparticles: effect of 1-hexadecylamine as stabilizing agent

Abstract: A facile method of preparing well-dispersed copper nanoparticles by polyol method, using 1- hexadecylamine as a protecting agent in ambient atmosphere, has been developed Polyol mediated preparation of nanoparticles is one of the widely used methods that enables controlling the size and shape of nanoparticles It is demonstrated that 1-hexadecylamine used as stabilizing agent during polyol mediated synthesis presents uniform, spherical and small sized copper nanoparticles than the commonly use PVP stabilizer Higher alkylamine/Cu molar ratio leads to production of spherical and smaller copper nanoparticles Palladium and gold prepared using alkylamine show uniform and small nanoparticles suggesting the efficiency of long chain alkylamine as capping agents The nanoparticles showed a self-assembling on the alkylamine template

Performance analysis of CNT-based interconnects

Abstract: In this paper we study the high-frequency effects due to the presence of drivers, repeaters and loads along an intermediate/global interconnects made of a densely-packed carbon nanotube (CNT) bundle, comparing the results with those obtained for an ideally-scaled Cu-based interconnect. The CNT interconnect is described by means of a multiconductor transmission line in cascade with suitable lumped circuit elements.

A link failure aware routing algorithm for Networks-on-Chip in nano technologies

Abstract: As nanotechnology scales down, the reliability issues are becoming more crucial, especially for Network-on-Chip (NoC) which must provide the communication requirements of Multi-Processor System-on-Chip (MP-SoC) even in presence of faults. In this paper we present a low cost faulty-link-tolerant routing algorithm through dynamic reconfiguration when the regular mesh topology is altered by faulty links. This algorithm is a reconfigurable extension of deterministic routing algorithms and is deadlock free by prohibiting a few turns. The performance and total energy consumption overheads which are very small under the low loads are evaluated through appropriate simulations.

Graphene nanoribbon schottky diodes using asymmetric contacts

Abstract: This paper presents Schottky diodes based on graphene nanoribbons (GNRs). We show that double gate GNR field effect transistors (FETs) with a p-type semiconducting GNR and asymmetric Schottky contacts provide a good rectification characteristic. The diode rectification can be tuned through the use of different GNRs with various widths. A rectification ratio of ~ 2×107 is achieved for an N = 10 GNR at a low gate bias voltage of 0.2 V.

Processing and modeling of multi-walled carbon nanotube/styrene-butadiene-styrene (SBS) composites for force sensing

Abstract: A novel stress-sensitive nanocomposite that can be used as flexible force sensors with tailored sensitivity was fabricated. The nanocomposite consists of MWNTs as conductive filler and SBS as polymer matrix. Some electrical and mechanical properties of MWNT/SBS films were measured. A typical percolation phenomenon was observed with the MWNT/SBS composites. The elastic modulus and Poisson's ratio of the composites with different MWNT concentration showed no statistically significant differences. In a low stress range, the resistance of the MWNT/SBS composite film decreased rapidly with stress increasing. A modified piezoresistivity model based on simplified GEME was then conducted to predict the resistance change of the nanocomposite film in low stress range.

On wires at low electron densities

Abstract: When analyzing reliability, wires have in most cases been ignored, with gates taking the lion's share, and devices being considered only once in a while. With scaling, this “only-computations-fail” approach is not going to be accurate enough as wires will also start to err. Trying to do justice to communication (wires), this paper details a statistical failure analysis of wires following on the few papers which have made wires' reliability their concern. We will use a classical particle-like probabilistic approach to enhance on the accuracy of wires' length-dependent probabilities of failure due to the discreetness of charge. Covering some of the intrinsic noises, such an approach leads to “lower bound”-like wire reliability estimates, as ignoring other intrinsic noises, as well as extrinsic noises, variations, and defects. These results should have implications for design strategies of multi-/many-cores and networks-on-chip, as well as for forward-looking investigations on emerging nano-architectures.