1) FIB. I tried to get a cross section of the pnc-Si with FIB with Brian’s help. The results are negative. It looks like the ion beam almost “melts” the membrane and destroys the pores instead of cutting.  The tool also has in-built Pt deposition capability (from organo-Pt compound). So we tried to make the…

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…

Charles developed a new microEO chamber, and I did some quick particle tracking experiments.  The fluid in front of the membrane was filled with 200nm fluorescent polymer beads, and the power supply was used to cause the fluid to flow within the chamber.  Bead speed was measured with Henry’s particle tracking programs. Picture of microEO:…

Recently I did some further research on the agglomeration in SiO2+Si layers. On my first post about agglomeration,I found that after annealing at 1000ºC for 1 min without susceptor, 15nm thick Si layer agglomerated and the average diameter of agglomeration islands is around 200nm. This time, I deposited three different thickness of top Si layers…

We have always speculated that applying a substrate bias during the silicon deposition “smooths” the film by creating a nicer film. With Graham’s help, I took a few AFM scans of films deposited at three different biases: 00, 05, and 50W. (a) 00 W: 0.337 nm RMS (b) 05 W: 0.145 nm RMS (c) 50…

We have already established that bias is an important parameter in controlling the morphology of 15 nm thick pnc-Si, but have yet to look at its effect on thicker films. This week, made a few 30 nm thick Si films with 02, 05, 25, and 50 W of substrate bias. I annealed these films at…

In this post, I will present my thoughts on the possible mechanisms of pore formation based on our most recent observations with the substrate bias experiments. As a precursor, I will discuss silicon crystallization since it is intimately related to the pore formation process. I will try to show that pore nucleation is driven by…

This is a continuation of the silicon substrate bias series. I have added several more data points to highlight the trend. Below are the TEM micrographs, pore distributions, average diameter/porosity/density plots. It would appear that the “optimal” bias is at 05W if we are using porosity as a metric. I also performed a short temperature…