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Articles 31 - 44 of 44

Full-Text Articles in Nanotechnology Fabrication

Cause And Prevention Of Moisture-Induced Degradation Of Resistance Random Access Memory Nanodevices, Albert Chen Jan 2013

Cause And Prevention Of Moisture-Induced Degradation Of Resistance Random Access Memory Nanodevices, Albert Chen

Albert B Chen

Dielectric thin films in nanodevices may absorb moisture, leading to physical changes and property/performance degradation, such as altered data storage and readout in resistance random access memory. Here we demonstrate using a nanometallic memory that such degradation proceeds via nanoporosity, which facilitates water wetting in otherwise nonwetting dielectrics. Electric degradation only occurs when the device is in the charge-storage state, which provides a nanoscale dielectrophoretic force directing H2O to internal field centers (sites of trapped charge) to enable bond rupture and charged hydroxyl formation. While these processes are dramatically enhanced by an external DC or AC field and electron-donating electrodes, …


Demonstration And Modeling Of Multi-Bit Resistance Random Access Memory, Albert Chen Dec 2012

Demonstration And Modeling Of Multi-Bit Resistance Random Access Memory, Albert Chen

Albert B Chen

Although intermediates resistance states are common in resistance random access memory (RRAM), two-way switching among them has not been demonstrated. Using a nanometallic bipolar RRAM, we have illustrated a general scheme for writing/rewriting multi-bit memory using voltage pulses. Stability conditions for accessing intermediate states have also been determined in terms of a state distribution function and the weight of serial load resistance. A multi-bit memory is shown to realize considerable space saving at a modest decrease of switching speed.


Vacuum Microelectronic Integrated Differential Amplifier, S. Hsu, W. Kang, J. Davidson, J. Huang, David Kerns, Jr. Aug 2012

Vacuum Microelectronic Integrated Differential Amplifier, S. Hsu, W. Kang, J. Davidson, J. Huang, David Kerns, Jr.

David V. Kerns

Reported is a novel vacuum field emission transistor (VFET) differential amplifier (diff-amp) utilising nanocrystalline diamond emitters with self-aligned gate partitions. The integrated VFET diff-amp was fabricated by a dual-mask self-aligned mould transfer method in conjunction with chemical vapour deposited nanodiamond. Identical pairs of devices with well-matched field emission transistor characteristics were obtained, realising a negligible common-mode gain, high differential-mode gain, and large common-mode rejection ratio (CMRR) of 55 dB. The emission current was validated by a modified Fowler-Nordheim equation in transistor configuration, and the CMRR was modelled by an equivalent half-circuit with the calculated result found to agree well with …


Terahertz And Microwave Detection Using Metallic Single Wall Carbon Nanotubes, Enrique Carrion Aug 2012

Terahertz And Microwave Detection Using Metallic Single Wall Carbon Nanotubes, Enrique Carrion

Enrique A Carrion

Carbon nanotubes (CNTs) are promising nanomaterials for high frequency applications due to their unique physical characteristics. CNTs have a low heat capacity, low intrinsic capacitance, and incredibly fast thermal time constants. They can also exhibit ballistic transport at low bias, for both phonons and electrons, as evident by their fairly long mean free paths. However, despite the great potential they present, the RF behavior of these nanostructures is not completely understood. In order to explore this high frequency regime we studied the microwave (MW) and terahertz (THz) response of individual and bundled single wall nanotube based devices. This thesis is …


A Parallel Circuit Model For Multi-State Resistive-Switching Random Access Memory, Albert Chen Jan 2012

A Parallel Circuit Model For Multi-State Resistive-Switching Random Access Memory, Albert Chen

Albert B Chen

Large, rapidly growing literature is available on bipolar resistive-switching random access memories (RRAM) made of myriad of simple and advanced materials. Many of them exhibit similar resistance switching behavior but, until now, no unifying model can allow quantification of their voltage and time responses. Using a simple parallel circuit model, these responses of a newly discovered RRAM made of a thin-film random material are successfully analyzed. The analysis clearly reveals a large population of intermediate states with remarkably similar switching characteristics. Such modeling framework based on simple circuit constructs also appears applicable to several RRAM made of other materials. This …


Modeling All Spin Logic: Multi-Magnet Networks Interacting Via Spin Currents, Srikant Srinivasan Dec 2011

Modeling All Spin Logic: Multi-Magnet Networks Interacting Via Spin Currents, Srikant Srinivasan

Srikant Srinivasan

All-spin logic (ASL) represents a new approach to information processing where the roles of charges and capacitors in CMOS are played by spins and magnets. This paper (1) summarizes our earlier work on the input-output isolation and intrinsic directivity of ASL devices, (2) uses an experimentally benchmarked simulator for multimagnet networks coupled by spin transport channels to demonstrate a combinational NAND gate, and (3) describes the natural mapping of such ASL networks into neuromorphic circuits suitable for hybrid analog/digital information processing.


Purely Electronic Switching With High Uniformity, Resistance Tunability, And Good Retention In Pt-Dispersed Sio2 Thin Films For Reram, Albert Chen Jun 2011

Purely Electronic Switching With High Uniformity, Resistance Tunability, And Good Retention In Pt-Dispersed Sio2 Thin Films For Reram, Albert Chen

Albert B Chen

Resistance switching memory operating by a purely electronic switching mechanism, which was first realized in Pt-dispersed SiO2 thin films, satisfies criteria including high uniformity, fast switching speed, and long retention for non-volatile memory application. This resistive element obeys Ohm's law for the area dependence, but its resistance exponentially increases with the film thickness, which provides new freedom to tailor the device characteristics.


Unidirectional Information Transfer With Cascaded All Spin Logic Devices: A Ring Oscillator, Srikant Srinivasan Jun 2011

Unidirectional Information Transfer With Cascaded All Spin Logic Devices: A Ring Oscillator, Srikant Srinivasan

Srikant Srinivasan

The authors have presented the first simulator that simultaneously describes magnetization dynamics as well as spin transport in multi-magnet ASL networks and used it to demonstrate the possibility of large scale functional spin logic blocks through the example of an All Spin ring oscillator.


Switching Energy-Delay Of All Spin Logic Devices, Srikant Srinivasan Dec 2010

Switching Energy-Delay Of All Spin Logic Devices, Srikant Srinivasan

Srikant Srinivasan

A recent proposal called all spin logic (ASL) proposes to store information in nanomagnets that communicate with spin currents in order to construct spin based digital circuits. We present a coupled magnetodynamics/spin-transport model for ASL devices that is based on established physics and is benchmarked against available experimental data. This model is used to show the linear dependence of switching energy and quadratic dependence of energy-delay of ASL devices on the number of Bohr magnetons comprising a nanomagnet. A scaling scheme that could lower the energy-delay of spin-torque switching while maintaining thermal stability is discussed.


Nano-Structured Optical Thin Films And Their Applications, Andrew Sarangan Nov 2009

Nano-Structured Optical Thin Films And Their Applications, Andrew Sarangan

Andrew Sarangan

No abstract provided.


Nano-Structured Materials For Imaging Polarimetry, Andrew Sarangan Oct 2008

Nano-Structured Materials For Imaging Polarimetry, Andrew Sarangan

Andrew Sarangan

No abstract provided.


Valley Splitting In Si Quantum Dots Embedded In Sige, Srikant Srinivasan Sep 2008

Valley Splitting In Si Quantum Dots Embedded In Sige, Srikant Srinivasan

Srikant Srinivasan

We examine energy spectra of Si quantum dots embedded in Si0.75Ge0.25 buffers using atomistic numerical calculations for dimensions relevant to qubit implementations. The valley degeneracy of the lowest orbital state is lifted and valley splitting fluctuates with monolayer frequency as a function of the dot thickness. For dot thicknesses ≤ 6 nm, valley splitting is found to be >150 μeV. Using the unique advantage of atomistic calculations, we analyze the effect of buffer disorder on valley splitting. Disorder in the buffer leads to the suppression of valley splitting by a factor of 2.5; the splitting fluctuates with ≈ 20 μeV …


Circuit Elements At Optical Frequencies: Nanoinductors, Nanocapacitors, And Nanoresistors, Nader Engheta, Alessandro Salandrino, Andrea Alù Jan 2008

Circuit Elements At Optical Frequencies: Nanoinductors, Nanocapacitors, And Nanoresistors, Nader Engheta, Alessandro Salandrino, Andrea Alù

Andrea Alù

We present the concept of circuit nanoelements in the optical domain using plasmonic and nonplasmonic nanoparticles. Three basic circuit elements, i.e., nanoinductors, nanocapacitors, and nanoresistors, are discussed in terms of small nanostructures with different material properties. Coupled nanoscale circuits and parallel and series combinations are also envisioned, which may provide road maps for the synthesis of more complex circuits in the IR and visible bands. Ideas for the optical implementation of right-handed and left-handed nanotransmission lines are also forecasted.


Nanophotonics: Design, Fabrication And Characterization (Sc647), Andrew Sarangan Dec 2005

Nanophotonics: Design, Fabrication And Characterization (Sc647), Andrew Sarangan

Andrew Sarangan

No abstract provided.