Using fresh tips, I re-ran the scans of amorphous Si films deposited at different biases. Recall that our theory states that interface roughness between the Si/SiO2 is an important determinant for ultimate pore morphology. A rough interface will suppress nucleation, which is why we observe low porosity with zero bias. The 05 W condition decreases…
In my last post, I introduced the concept of pore size dependent carbon growth on alumina coated membranes. Here, I have plotted a Gaussian fit of the tail of the pore size distribution of carbonized membranes (with and without an alumina coating). I am only showing the tail of the distribution to highlight the sharpness…
This week, I did a systematic study on the growth rate of carbon on bare and aluminum oxide coated pnc-Si membranes. The bare samples were not treated prior to carbonization, while the alumina coated samples underwent a 5 nm treatment in the ALD tool. A bare and alumina coated sample were placed together inside the…
With some of the recent high porosity membranes being produced, I wanted to demonstrate that we can use ALD to create a movable cut-off without sacrificing too much in permeability. I took sc713 and coated it with 5 nm and 10 nm of Al2O3 i.e. I shrank the pore diameter by 5 and 10 nm….
I’ve been working with the AFM recently and have had some success getting images on supported pnc-Si films. Yesterday, I imaged three samples from sc 698: one untreated pnc-Si film and two films coated with aluminum oxide (1.5 nm and 5 nm thickness). Here are the scans (500 nm x 500 nm). The topmost scan…
Today, I ran a quick experiment to confirm that water transport was not negatively affected by an aluminum oxide coating. I deposited 1.5 nm of Al2O3 onto a pnc-Si membrane which I then treated with an oxygen plasma in the YES system. I was curious to see whether the alumina coating along with O2 treatment…
Today while I was imaging a Al2O3 coated pnc-Si membrane on the high-res TEM, I noticed something curious as I placed the beam on a single pore for a few minutes. I was initially interested in the structure of the aluminum oxide coating, but found that something started to deposit on the pore walls as…
This is a quick post on comparing the contact angle after ALD on pnc-Si with aluminum oxide vs the untreated material (+/- ozone). The hypothesis is that the angle should drop since Al2O3 is hygroscopic. The angles are 85°, 45°, 61°, and 50° for the untreated, ozone, Al2O3, and Al2O3 and ozone case, respectively. These…
This is a follow-up to my initial report on using the ALD to coat pnc-Si pores with Al2O3. Below are the TEM micrographs and histogram of a series of depositions I performed with 3 different process times. I was targeting a 5 nm, 10 nm, and 20 nm reduction in pore diameter. The average diameter…
Today I made my first attempt at depositing aluminum oxide on pnc-Si using URInc’s Cambridge Nanotech’s Savannah 200 atomic layer deposition tool. Ritala and Leskela give a nice primer on ALD theory. ALD relies on layer-by-layer growth of film by reacting a precursor with the surface of interest. In this particular system, we react trimethylaluminum…