Au Nanoparticles deposited on tented structures

ByGreg Madejski

To test the filtration capabilities of our tents, Tucker and I immersed a tented (wafer 1150, ~30 nm pores) oxide structure (~3 um hole diameter, 200 nm high) and a nontented structure in a solution containing 60 nm (.043 nM) and 10 nm (~10 uM) Au nanoparticles for 1 hour (2 uL incubation volume), rinsed them (100 uL), dried them out (70C oven 1 hr), and imaged the remaining particles and structures under SEM. Unfortunately, there were no particles remaining. Experience from Josh Winans has told us that gold generally does not like to attach to silicon nitride.

Nanoporous Tent and Au? Nanoparticles
Nanoporous Tent and Au Nanoparticles nowhere to be found. 
Close up view, no nanoparticles to be seen
Close up view, no nanoparticles to be seen

 

So we switched from gold particles to polystyrene beads (20 nm and 100 nm diameter). These substrates were coated with 5 nm platinum before imaging. Unfortunately, the tent flew off the active region, but the images are still useful.

nanoporous+pt_04
Untented Oxide Pit region with a few large nanoparticles visible
nanoporous+pt_02
100 nm and 20 nm particles in previously tented region. The large particles are grouped and could not have gotten in if the filters were in place. They may have dried there and slid down the sides of the oxide pits.

 

 

nanoporous+pt_10
Magnified view of remaining particles after tent delaminated
nanoporous+pt_74
Image of the tent off of the active region. The tent acts as a prefilter
nanoporous+pt_80
Magnified view of pore filtration

nanoporous+pt_81 nanoporous+pt_90

 

We still need to show a good crossection of this process. Two images would be sufficient.

1. An image like ‘Tent acts as a prefilter’, displaying the nanomembrane filtering out garbage from the cavity.

2. Fractured membrane with small particles below, and no large particles below.

Using a tent chip substrate with posts instead of holes would increase the chances of finding picture number 2, as it increases the area below the tent. We’ve also observed that the polystyrene tended to associate with the oxide spacer instead of the nitride floor in the attocavity space. Moving to a substrate with posts will help us by reducing the amount of oxide overall compared to the pit substrates.

 

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