CREATION OF NANOTUBES

RUN #: ______OPERATOR: ______

DATE: ______ASSISTANT: ______

Notes on Preparation:

Use latex or equivalent gloves for all activities involving the handling, removal or storage of wafers. Also use gloves to handle furnace tube and sample holder.

Entire procedure should be done under the cleanest conditions possible. Use laminar flow hood for cutting, cleaning and catalyst procedures.

Cutting:

1)Cleave silicon wafers by using pressure with razor blade on the edge of the wafer. Make one wafer 10mm × 10mm and 4 wafers 12.5mm × 10mm.

2)Label wafers with Roman numeral scratch mark using diamond scribe. The small wafer should be named # I.

Cleaning:

1)Rinse wafers with methanol.

2)Rinse wafers in toluene, sonicate wafers for 15 min. at room temperature in toluene.

3)Rinse with acetone, sonicate 15 min. in acetone.

4)Rinse with isopropyl alcohol (IPA), sonicate 15 min. in IPA.

Catalyst:

1)Make general solution in small glass container and shake well. Soln #1: 0.25g ferric nitrate (Fe (NO3)3 + 9H20) in 25ml electronic grade IPA .

2)Dilute solution to specification:Soln #2: 25μl soln #1: 25ml electronic grade IPA.

Spinning:

1)Put a 50μl drop of the catalyst on the small wafer (10mm × 10mm). Let dry in air.

2)Take the wafer out from the IPA solution and place on platform, turn on vacuum.

3)Press start to spin.

4)Adjust with dial to 3.00 krpm.

5)Drop catalyst onto the wafer and let dry (typically 10 sec). Repeat for 16 drops (200 μl).

6)Repeat steps 2-6 for the rest of the wafers.

BakingPreparation:

  1. Blow the dust off of the wafer holder with nitrogen.
  1. Load wafers onto holder in the following order: 1- flat (use the small wafer), 2-4 downstream, 5 - upstream
  1. Flush Argon, H2 and CH4 for about 2 minutes. During that time use the needle valve to set the appropriate flow rates :

a)Argon – 100 (440ml/min)

b)H2 – 50 (125ml/min)

c)CH4 - 42 (1080ml/min)

  1. Close the ball valve for the H2 and CH4, leaving the Ar flowing.
  1. Gently slide holder about 21cm into the furnace (this should put the holder exactly in the middle of the furnace).
  1. Slide thermocouple into tube until close to wafers.
  1. Stuff furnace ends with Fiberfrax insulation.
  1. Turn fans on directed at the end of the quartz tube.

Baking:

1)Flush Argon through furnace for 15 minutes.

2)Add H2 at 125ml/min.

3)Heat furnace to 950 C using Set Point dial (set dial to 940).

4)Hold at desired temp for 15 minutes with same flow rates.

5)Turn off H2 and flush with Argon only for 5 min.

6)Turn on CH4 at 1080ml/minand H2 for 5 min., immediately turn off Argon.

7)Turn on Argon and immediately turn off H2 and CH4. Flush with Argon for 5 min.

8)Turn off furnace and let cool under Argon flow until temperature is ~ 100 C.

9)Take the holder out of the quartz tube and unload wafers into a clean box.

List of used materials:

  • Wafers -
  • Catalyst from SIGMA-ALDRICH, Iron (III) nitrate nanohydrate, 99.999+%
  • Isopropyl alcohol (v555-10), Toluene (v561-10), Acetone (2435-10), and Methyl alcohol (H488-10) are from Mallinckrodt chemicals. They are all suitable for liquid chromatography, extract/conc, UV-spectropholometry.
  • Isopropanol, 99.8% residue free, for electronic use from Acros organics.
  • Ultra pure H2, Ultra pure CH4 , and Ar are from Airgas.

Questions associated with Nanotube exercise.
1. Calculate the concentration of ferric nitrate in the final
isopropanol suspension.
2. a. If all of the ferric nitrate suspension that you dropped onto
the silicon substrate stayed there, estimate the total mass of
ferric nitrate on the substrate.
b. If each drop of the isopropanol suspension spins down to a thickness of 100 nm, estimate the total mass of ferric nitrate on the substrate.

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