Passivation of Carbon Nanotube Chips for Biosensing Applications

By: Vince NguyenFaculty Mentor: Dr. Phillip CollinsLab Mentor: Dr. Jaan Mannik

IMSURE PROGRAM

What is Passivation?

According to www.dictionary.com-To treat or coat (a metal) in order to reduce the chemical reactivity of its surface. -To coat (a semiconductor) with an oxide layer to protect against contamination and increase electrical stability.

Why Research Passivating CNTS Chips?

-Contribute knowledge to understand more about nanoelectronics.-Gain experience in a more technical laboratory work by working with others.-Future contribution to biochemistry, chemistry, and physics.

Introduction to Carbon Nanotubes (CNTS)

• Extremely small tubes.• A few nanometers wide.• Length >>>>>> Width.• Cylindrical carbon

molecules with properties that is potentially useful.

• sp2 bonds; stronger than sp3 bonds in diamond.

• All atoms are on the surface of single-walled nanotubes.

www.abb.com/global/ abbzh/abbzh254.nsf/0/1474d... http://www.nano-lab.com/image5.htmlwww.fujixerox.co.jp/.../ inbt/m_electronics/

Big Picture of Current Research

• Minimize the amount of electrochemical reactions to accurately do electrical measurements on CNTS chips.

• Detect if biomolecules actually bind to CNTS in electrolyte solutions.

• Current scientific/medical companies successfully create H2(g) sensor using CNTS for patients with breathing problem; they are considering of creating CO2(g) sensor as well.

How do Biomolecules Bind to CNTS

www.jcnabity.com/ nanotube.htm pubs.acs.org/cen/topstory/ 7919/7919notw9.html

Why Passivation?

Experimental MethodsSilicon oxide device (clean and uncovered) Silicon oxide device (covered with polymer)

Scanning electron microscope (SEM)Remove of exposed area using mixed solvents

SEM’s Contribution to Research

• Allow successful creations of big windows.

• Allow verification of big windows to see if they are successfully removed (observation).

• Work with NORAN System SIX to allow successful creations of line windows.

• Allow verification of line windows to see if they are successfully removed (observation).

• Spot size mode in SEM is the command that contribute a lot to line window’s creations.

Limitations of Our SEM

• Higher magnification causes polymer’s exposed area to burn.

• Scan 1 mode’s scanning box can’t be minimize for smaller window’s creations.

• Measurement of beam current is quite complex.

• SEM system does not have a built-in command to automatically scan the area of interest on silicon oxide chips at an exact amount of time that we want.

• Using SEM to do passivation requires quick and fast hand movement to minimize the amount of exposure of beam current on unwanted area.

Results

Length = 13.92 micronsWidth = .64 micronN = 15, t = 4 secondsM = X 2500ss = 3n = 1.1 points/micron

M = X 2500ss = 25t = 2.5 minutesM = Magnification

ss = SpotsizeAcV = Accelerating Voltage = 10 kV (Constant)N = # of points per scant = total time per scanWD = working distance = 10 mm (Constant)n = points scan per unit length

Device III

Continue…

Device 2 Device 4

n ranges from 1.1 to 1.4 points per micron in length

N = 40, t = 11 secondsLength = 28.67 micronsWidth = 1.33 micronsss = 1M = X 3000

ss = 4, M = X 3000

Verification of ResultsBefore Passivation After Passivation

Device I

Continue…Before Passivation After Passivation

Device III

Future Research

• May explain why strange dots exist when creating line windows.

• May create even smaller windows if measured interference is found to be unacceptable.

AcknowledgementsI would like to thank…

My Mentor: Dr. Phillip CollinsMy Lab Mentor: Dr. Jaan MannikResearchers in Lab: Brett Goldsmith,Dr. Yuwei Fan, Alex Kane, and DerekKingreyIM-MURE ProgramUC IrvineCoordinator: Said Shokair