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…
Diffusion based separation theory uses a hindrance model to explain how the pores affect the diffusion of molecules of different sizes. The simplest and most well known hindrance model is given by the Renkin Equation: where Dm is the diffusion coefficient within the membrane, D0 the free diffusion coefficient, and α the ratio of molecule…
I first wrote about quantifying the pore formation process using kinetic theory last year. In this post, I will develop my thoughts a bit more. In the literature, researchers oftentimes present charts, like the two shown below, describing the Arrhenius behavior of silicon crystallization (Sontheimer APL 95 2009). Figures 3 and 4 show the crystal…
I reported last week that a 15 nm silicon film deposited with 05 W substrate bias yielded a highly porous film. This week, I wanted to confirm this effect as well as compare it to films deposited at 10 W and 25 W (our baseline). We find that the 05 W is reproducible and the…
These experiments were conducted during the week of 5/10/2010 – 5/14/2010. To recap on this project, Barrett and I have been working with Dr. Harold Smith in the hopes of developing a drug screening test that consists of small-scale diffusions. In these experiments, we are working with APOBEC3G (A3G), a protein-RNA complex that is active…
In my last post, I presented the results of my BBB TEER experiments. For the BBB co-culture, there was a spike in TEER. I hypothesized that this was caused by media acidification by rapidly proliferating glial cells, which in turn negatively affected barrier function of endothelial cells. When I presented this data to Angela Glading,…