Prashanth Makaram

Experimental and Numerical Investigation of Nanoparticle Removal Using Acoustic Streaming and the Effect of Time

The removal of nanoparticles is becoming increasingly challenging as the minimum linewidth continues to decrease in semicon-ductor manufacturing. In this paper, the removal of nanoparticles from flat substrates using acoustic streaming is investigated. Baresilicon wafers and masks with a 4 nm silicon cap layer are cleaned. The silicon-cap films are used in extreme ultraviolet masks toprotect Mo–Si reflective multilayers. The removal of 63 nm polystyrene latex PSL particles from these substrates is conductedusing single-wafer megasonic cleaning. The results show higher than 99% removal of PSL nanoparticles. The results also showthat dilute SC1 provides faster removal of particles, which is also verified by the analytical analysis. Particle removal from the4 nm Si-cap substrate is slightly more difficult as compared to bare silicon wafers. The experimental results show that the removalof nanoparticles takes a relatively long removal time. Numerical simulations showed that the long time is due to particleoscillatory motion and redeposition, and that this phenomenon is not observed in the removal of sub- m or larger size particles.© 2006 The Electrochemical Society. DOI: 10.1149/1.2217287 All rights reserved.Manuscript submitted January 9, 2006; revised manuscript received April 24, 2006. Available electronically July 19, 2006.

Trends in Nanomaterial-Based Non-Invasive Diabetes Sensing Technologies

Blood glucose monitoring is considered the gold standard for diabetes diagnostics and self-monitoring. However, the underlying process is invasive and highly uncomfortable for patients. Furthermore, the process must be completed several times a day to successfully manage the disease, which greatly contributes to the massive need for non-invasive monitoring options. Human serums, such as saliva, sweat, breath, urine and tears, contain traces of glucose and are easily accessible. Therefore, they allow minimal to non-invasive glucose monitoring, making them attractive alternatives to blood measurements. Numerous developments regarding noninvasive glucose detection techniques have taken place over the years, but recently, they have gained recognition as viable alternatives, due to the advent of nanotechnology-based sensors. Such sensors are optimal for testing the amount of glucose in serums other than blood thanks to their enhanced sensitivity and selectivity ranges, in addition to their size and compatibility with electronic circuitry. These nanotechnology approaches are rapidly evolving, and new techniques are constantly emerging. Hence, this manuscript aims to review current and future nanomaterial-based technologies utilizing saliva, sweat, breath and tears as a diagnostic medium for diabetes monitoring.

Large scale directed assembly of nanoparticles using nanotrench templates

The authors describe a general high throughput directed assembly technique to address some of the challenges to enable high rate∕high volume nanomanufacturing. The directed assembly of colloidal particles using an applied electric field shows the ability of precise control of nanoparticles by controlling assembly voltage, time, and geometric design of templates. The results show that single nanoparticle lines as small as 10nm wide and 100000nm long over a 2.25cm2 area as well as other nanoparticle structures can be fabricated using electrophoresis. This approach offers a simple, robust, and fast means of directed assembly of nanoelements for many applications.

Directed assembly of gold nanoparticle nanowires and networks for nanodevices

Alternating electric field is used to assemble gold nanoparticle nanowires from liquid suspensions. The effects of electrode geometry and the dielectrophoresis force on the chaining and branching of nanowire formation are investigated. The nanowire assembly processes are modeled using finite element calculations, and the particle trajectories under the combined influence of dielectrophoresis force and viscous drag are simulated. Nanoparticle nanowires with 10nm resolution are fabricated. The wires can be further oriented along an externally introduced flow. This work provides an approach towards rapid assembly and organization of ultrasmall nanoparticle networks.

Scalable nanotemplate assisted directed assembly of single walled carbon nanotubes for nanoscale devices

The authors demonstrate precise alignment and controlled assembly of single wall nanotube (SWNT) bundles at a fast rate over large areas by combining electrophoresis and dip coating processes. SWNTs in solution are assembled on prepatterned features that are 80nm wide and separated by 200nm. The results show that the direction of substrate withdrawal significantly affects the orientation and alignment of the assembled SWNT bundles. I-V characterization is carried out to demonstrate electrical continuity of these assembled SWNT bundles.

Three dimensional controlled assembly of gold nanoparticles using a micromachined platform

By using optical lithographic procedures, the authors present a micromachined platform for large scale three dimensional (3D) assembly of gold nanoparticles with diameters of ∼50nm. The gold nanoparticles are formed into 3D low resistance bridges (two terminal resistance of ∼40Ω) interconnecting the two microelectrodes using ac dielectrophoresis. The thickness of the parylene interlevel dielectric can be adjusted to vary the height of the 3D platform for meeting different application requirements. This research represents a step towards realizing high density, three dimensional structures and devices for applications such as nanosensors, vertical integration of nanosystems, and characterization of nanomaterials.

A Three Dimensional Thermal Sensor Based on Single-Walled Carbon Nanotubes

We present a novel three-dimensional thermal sensor based on Single-Walled Carbon Nanotubes (SWNTs) utilizing dielectrophoretic (DEP) assembly. The sensor is fabricated using a hybrid assembly technique combining top down (fabrication of the microplatform) and bottom up (DEP assembly) approaches. Encapsulating the structure with a thin (1mum) parylene layer protects it from the environment and also improves the contact resistance. Both single and multi finger assembly electrode structures have been utilized to manufacture the 3D thermal sensor and its thermal sensitivity is measured with a heated chuck. The resistances of the structures decrease more than 10% across a temperature range from 25degC to 65degC. The temperature coefficient of resistance for the SWNT-based thermal sensor is measured and ranged from -0.154 to -0.24% for the single electrode device and varied from -0.3 to - 0.57% for the multielectrode device.

A three dimensional Multi-Walled Carbon Nanotube based thermal sensor on a flexible Parylene substrate

We present the first design, fabrication and testing results from a three dimensional multi-walled carbon nanotube based thermal sensor fabricated on a flexible parylene-C substrate. Parylene-C is an inert, biocompatible, optically transparent, room temperature deposited polymer with a high mechanical strength, yet is rarely used as a flexible substrate. By utilizing a 2 mask process, we have manufactured a versatile microplatform for nanoscale assembly and then by utilizing dielectrophoretic assembly, incorporate MWNTs onto the platform in a 3D manner. The MWNTs are next encapsulated using a thin Parylene-C layer that acts as an environmental barrier and in addition keeps the MWNTs intact. The temperature Coefficient of Resistance of the MWNT sensor is measured to be between -0.21% and -0.66% per degree. The thermal sensor is compact, is very high density and could potentially be used for diverse temperature sensing applications such as in wearable textiles, on non planar surfaces and for in-vivo applications.

Fabrication and Evaluation of Carbon Nanotube-Parylene Functional Composite-Films

We present the design, fabrication and mechanical testing results from Parylene-Carbon Nanotube (CNT)-Parylene composite-films. Utilizing SWNT materials as the active layer, we have fabricated flexible devices consisting of 10 mum thick parylene membranes wrapped around active SWNTs. The tensile test results show that parylene-CNT-parylene sandwich has a linear-elastic response up to a strain value of epsiv = 2% and the composite fails at epsivFail= 7.5% strain. The load-unload testing of the sample shows that a very small change in resistance (~1%) was observed when applying a strain ranging from 0% to 2% and the results were repeatable up to 100 times. The resistance of the CNT-parylene film increased 9 fold at failure. Potential applications of this work include interconnect materials for flexible electronics devices.

A Novel Three Dimensional Field Effect Transistor Based on Single-Walled Carbon Nanotubes

We present the design, fabrication and testing of a novel three dimensional (3D) Field Effect Transistor based on Single-Walled Carbon Nanotubes (SWNTs). Three Dimensional SWNT transistors are realized utilizing low temperature Dielectrophoretic (DEP) assembly. A 1mum thick conformal Parylene-C (poly-para-xylylene) layer is utilized as the gate dielectric with a non-local top gate electrode around the conducting channel. The preliminary results from 3D Carbon NanoTube Field Effect Transistors (CNTFET) display ambipolar behavior with more prominent p-type than n-type behavior. The transistor exhibits an on-to-off current ratio of ~3 x 104, a maximum transconductance of 0.061 mus, and a mobility of 85- 277 cm2/Vs. This 3D-CNTFET technology can be utilized to realize multi layer, compact and high density nanotube transistors for large scale nanoelectronic circuits.