IISME Fellowship Description

I worked at Stanford University in a chemical engineering lab.

Stanford likes its creepy statues.

2013 Last summer the new chemical engineering building was under construction

2014 This summer we moved into the new building

What does a chemical engineering lab look like?

Complex equipment had to be completely disassembled, packed, moved, and reassembled. This is an ALD reactor. More about ALD later.

This is another ALD reactor.

This is an MLD reactor.

This is a glove box. This is how you work with chemicals you don’t want to expose to air.

Much of the research done in the Bent lab can be applied to electronics.

Goal: deposit ZnO ONLY on Si Pt ZnO

Hypothesis: SAMs will block ALD Dielectric Metal SAM deposition ALD Dielectric film SAM = self-assembled monolayer ALD = atomic layer deposition Self-assembled monolayers (SAMs) bond to metals but not silicon. They prevent the atomic layer deposition (ALD) precursors from reaching the metal surface.

Atomic Layer Deposition (ALD) Zn(C2H5O)2 + H2O → ZnO + 2C2H5OH ALD creates thin films of uniform thickness. The surface is exposed to one reactant at a time for as many cycles as needed (more cycles = thicker film).

Procedure 1) Immerse substrates in SAM solution Si Pt

Procedure 2) SAMs form on metallic surface Si Pt

Procedure 3) ZnO deposited by ALD Si Pt ZnO

What does this look like IRL? Start with a wafer...

Pt wafers are cut into small substrates

Si Cu

Sonicator substrates are sonicated in ethanol for 10 minutes, then in acetone for 10 minutes

Sonicator Sound energy is used to loosen particles from substrate surface

UV Ozone generator UV light source Substrates are dried with nitrogen, then placed in the UV ozone generator to further clean the surface. One set of substrates were cleaned with sonication only, and the other set with sonication AND UV ozone. UV Ozone generator

O3 decontaminates the substrate surface UV Ozone generator

substrates are now placed in vials with SAM solution 0.1mM 1mM 10mM

the vials are sealed with parafilm and placed in a water bath at 30oC for various times (2hr, 4hr, 8hr, 18hr, 24hr)

When the predetermined time is up, substrates are rinsed with ethanol and dried with nitrogen, then placed in sample cases. It’s important to label everything very clearly.

...because sometimes you have a lot of samples to test!

Ellipsometer measures thickness First, the samples are taken to the ellipsometer. The ellipsometer uses polarized light to determine how thick a sample is. measures thickness

Goniometer measures water contact angle

Si Pt low water contact angle hydrophilic surface SAMs not likely present high water contact angle hydrophobic surface SAMs likely to be present

syringe needle water Pt glass slide

syringe needle water Si glass slide

XPS samples go inside here Samples are taken to the XPS (x-ray photoelectron spectroscopy) chamber in a different building.

XPS samples

A beam of x-rays bombards the sample, causing electrons to move to an excited state. When they return to their ground state, photons are emitted and detected. The energy given off is used to identify elemental composition.