The ‘standard’ window size is 0.5 mm square and this dimension is more than enough for most TEM workers. Remember, larger membrane window is never going to be as robust as a smaller window. We’ve had some requests for larger windows for TEM and now offer at least two standard products that have a 1 mm square window.
Membrane square window
Membrane square window
Ultra Thin Membrane Windows
Our 20 nm windows represent the very latest in production technology for membrane window grids. Remember, the membrane itself is ‘stoichiometric’ and not ‘low stress’ but it does not really matter anyhow since the stress is so low. Any way you look at it, 20 nm is very thin, so thin that we hesitate to guarantee to anyone that the 20 nm windows can be spin coated or exposed to various other forms of processing without rupturing the membrane. The membranes are sufficiently robust to perform as a TEM grid, with the smaller size windows being more robust than the larger ones. We make no guarantee that the 20 nm windows will be completely free of pin-hole defects (for TEM applications, this should not matter).
SiN membrane thickness
Visually one can ‘see through’ the windows if you view them by transmission light microscopy. There has to be some thickness beyond which the optical transparency starts to decline, but even at 200 nm thickness, they are transparent in the visible range of the spectrum. When considering optical properties, keep in mind that the absorption edge is just below 13 nm. Hence at 13 nm the transmission for a 100 nm membrane is about 44%. At 12.4 nm it drops down to about 13%. Always keep in mind where they are relative to the absorption edge when trying to estimate membrane optical properties. Our target for refraction index is approximately 2.15, but we make no gaurantees nor represent this as a specification of the product.
Optical Transparency At More Than 13nm
Optical Transparency At 13nm
Optical Transparency At 12.4nm
- For SEM applications, the background is relatively structureless and featureless (remember, nothing is completely structureless or featureless).
- For x-ray microscopy there is really no other way for mounting many of the samples one would want to analyze.
- For SEM BSE imaging, cells can be grown directly onto the nitride windows and the volume sealed with a "blank" without membrane for a perfect UHV compatible environmental chamber.
- For high temperature applications, we believe that the nitride membranes are stable up to at least 1000°C. A report on information validating the robust nature of the membrane windows can be found here. Morphological information can easily be obtained as a function of annealing time without concern about breakage of the membrane (within limits, of course!).
- We assume our membranes are as flat as the underlying silicon wafers. In terms of roughness our specification for the starting wafer is to be better than 0.5 nm RMS, but it is not a stated specification for roughness of the final membrane. We have reports of customers doing their own roughness measurements and reporting as good as 0.2 nm RMS. We have not made exhaustive measurements of our own.In our opinion the flatness is acceptable for most users and similar on both sides. We've never measured the "well" side for flatness because one can not get a SPM probe down into the well. We assume the flatness closely mirrors the that of the underlying silicon wafer. Therefore the well side can't be any more rough than the opposite side, it could only be smoother.
- First and most important: The amount of frame left is so little that the grids would 'snap' when being broken out of the wafer into individual grids. Secondly: It would be difficult to pick up a grid with such a small frame with a pair of tweezers without damaging the window. We can make larger windows but not in a TEM grid product.
- Those considering larger than the standard (I.E. 0.5 mm) windows generally want a larger field of view. For these we offer the 1 mm window products. For those contemplating processing, smaller windows are desired. All of the SPI Supplies silicon nitride membrane window grid products can be easily spin coated provided arrays of membranes are being coated.
- IST's TEM/SEM window?can be used to create a unique environmental chamber or "wet cells" which permit the BSE imaging of cells and other wet samples at resolutions heretofore just not possible.
- The silicon nitride membrane window grids do not need further cleaning before use. There are occasionally small pieces of nitride scattered around from the snap out corners (that make the frames rounded) but the presence of such debris particles can't be prevented. They should not pose any problems or interference to the user.If one does want to clean the membranes for some reason, then we suggest using H2SO4 : H2O2 (1:1) for organic and H2O:HCl: H2O2 (5:3:3) for metals. The membranes are not compatible with ultrasonic treatments. The windows have a tendency to shatter.
- All the commonly used coating methods can be used on the membrane but there can be adhesion problems, not necessarily because they are membranes, but just because they are normal surfaces with the properties of normal surfaces. One can use vacuum evaporation, sputter coating, or spin coating without undo problems. In the case of gold coating, we normally apply a thin layer of chromium to enhance adhesion.
- We have also successfully made our first holey membranes using micro fabrication techniques. Such grids make possible the depositing of nanofibers or other samples across the holes so that data can be taken without any contribution from the support being present in the final data. Putting holes into the membrane increases the price typically by 2-3 times, depending on the number of holes needed.
- Silicon Nitride Window for Transmission Electron Microscopy
FRAME THICKNESS 200 μm FRAME SIZE 3 mm x 3mm TYPE MEMBRANE THICKNESS (nm) WINDOW SIZE (mm2) IN STOCK B0204S3W0250N 15 0.25×0.25 yes B0204S3W0500N 15 0.50×0.50 yes B0204S3W1000N 15 1.00×1.00 yes B0201S3W0250N 30 0.25×0.25 yes B0201S3W0500N 30 0.50×0.50 yes B0201S3W1000N 30 1.00×1.00 yes INCLUDED IN EACH PACK 10 pieces TEM window
per piece just
- CUSTOMIZED PRODUCT
- We are now able to offer the customized silicon
- nitride window product. Customers allow to order
- specific windows that for their unique size and/or
- thickness requirements.