As the title states, I partially etched some different material (Wafer 2238, 100 nm NPN) to create nanofeatures with blown out holes. With a thicker membrane, we can blow out the pores more (etch longer) without compromising the strength of the material (with regard to templating purposes). These membranes were fractured and coated with 6 nm of platinum. These images are only the NPN; not coated with gold or templated with MgF2.
Equivalent pore diameter histograms for partially etched substrates.
Minor Axis histograms of partial etch (0, 20, 40, 60, 80s) of Wafer 2238 (from top to bottom). Average length: 42, 48, 53, 56, 72 nm. Based on estimates of etch rate, the thicknesses of these membranes are (100, 80, 60 40, 20 nm, from top to bottom). Pores merge considerably below 40nm.
Zoom-in of wafer 2238. The scaly structures are residual pieces (siloxynitride?) used as a mask to create the thicker NPN materials. there also appears to be some conical shape to the pores, instead of anisotropic sidewalls.
Viewed off-normal, the thickness of the siloxynitride is appreciable.
40s etch crossection, 64 nm thick. (vibration hinders some resolution). The pores have a conical crossection.
80s etch aerial image. Residue pattern from the silicoxynitride is transferred through the nanomembrane’s volume.80s etch crossection. 23nm thick. The silicoxynitride acts as an etch mask (with poor selectivity) and is causing the texture at the surface.80s crossection. Shows the scalloped merged pores with sharp peaks.
I think the 2238-80s material is too weak to hold up to MgF2 processing, but there is hope for the 60s material.
We wanted to test the effects of changing the substrate bias during the Si deposition step similar to what Dave Fang had done so many years ago. Attached is a couple of plots showing the effect of varying substrate bias on pore size and porosity. He used 15 nm thick a-Si and an anneal at…
To this point, I have shown that our membranes are stable with the use of INT’s developer over time. I have also shown that their developer has statistically similar flow properties to that of water, and is a viable option to pass through our membranes. This post will discuss the possibility of using their unique…
In the field of gas permeance there is a plot called the “Robeson Plot” (the paper that debuted it) that is used to compare the separation behavior of various membranes made of different materials and measured in different systems. An example is pictured: Various literature data for the log permeability of H2 gas versus the…
In my last post we determined that there is an inverse relationship between porosity and burst pressure. I continued to dig further into other factors that affect the burst pressure of the membrane. Pure silicon was used in all the measurements. I measured the burst pressure of many samples that differed in properties that includes…
In support of the bone infection studies done in the Schwarz lab at URMC, I have recently been tasked with coordinating a new collaboration with Dr. Yates lab in the Chemical Engineering department. The goal of this collaboration is to establish a method to coat our membranes with hydroxyapatite crystals. Two different methods were attempted,…
Over winter break I put together some posters to hang up in the lab. I tried to represent in an clever way a few key areas of research that NRG is interested in: If anyone has any ideas for more, or any suggestions for captions or improvements (I’m really not a fan of “At…
