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Amorphous Silicon TEM Windows:
Half the Chromatic Blur and No Organic Contamination

A comparison analysis of the thinnest amorphous carbon and 5 nm amorphous UltraSM« Silicon TEM Windows revealed that UltraSM« Silicon TEM Windows:

  • Yield half the inelastic scattering of ultra-thin amorphous carbon
  • Are 35%+ thinner
  • Tolerate aggressive plasma cleaning and high-beam currents

These results were obtained through a grant program at Cornell University in collaboration with
Dr. David Muller, Associate Professor of Applied and Engineering Physics

Comparison of UltraSM« Non-Porous Silicon TEM Windows to the thinnest commercially available amorphous carbon grids reveals key differences for TEM imaging and analysis. UltraSM« Silicon TEM Windows yield half the inelastic scattering of ultra-thin amorphous carbon and are more uniformly thin. Combined with their tolerance for high-beam current and plasma cleaning, UltraSM« Silicon TEM Windows enable the preparation of higher quality samples, leading to improved imaging and reduced instrument time.

Comparison of Amorphous Silicon and Amorphous Carbon

A comparative analysis of electron energy loss spectroscopy (EELS) was performed at Cornell University by Dr. David Muller, a leading researcher in transmission electron microscopy. The analysis compared 5 nm amorphous UltraSM« Non-Porous Silicon TEM Windows with the thinnest commercially available amorphous carbon TEM grids (advertised as 3 nm thick). The spectral data shown below reveal two important distinctions:

  • Thickness: The ultra-thin amorphous carbon grids are 5-10 nm thick (2X to 3X thicker than advertised), while the amorphous UltraSM« Silicon are 3.5-5 nm thick.
  • Inelastic Scattering: The spectra reveal two-times less inelastic scattering of the electron beam within amorphous UltraSM« Silicon compared to amorphous carbon. Note the two-fold greater broadening of the spectrum from amorphous carbon, leading to twice the chromatic blur for the inelastically scattered electrons.

Figure 1: Electron Energy Loss Spectroscopy Analysis of 5 nm Amorphous UltraSM« Silicon (a-Si) and 3 nm Amorphous Carbon (a-C) EELS spectra were recorded on a 200 keV FEI Tecnal F20 and normalized to equal zero peak intensities. The sample thickness, t, can be extracted from the ratio of the inelastic/ elastic scattering if the inelastic mean free path, λ , is known. For a-C, t/λ = 0.1 and t = 10 nm. For a-Si, t/λ = 0.05 and t = 6.5 nm. Inelastic mean free paths, λ, were calculated using equation 5.2 from Egerton (1996)
1. R.F. Egerton, "Electron Energy-Loss Spectroscopy in the Electron Microscope", 2nd ed., Plenum, NY (1996).

Effectively three times thinner with reduced inelastic scattering, 5 nm amorphous UltraSM« Silicon TEM Windows help minimize chromatic blur, improve image resolution, and offer improved contrast relative to the best amorphous carbon TEM grids.

Figure 2: Representative images of gold nanoparticles imaged on 5 nm UltraSM« Silicon; plasma cleaned for 120 seconds prior to imaging. (Click on individual images to view full-resolution)

The pure silicon composition of UltraSM« Silicon TEM Windows improves substrate tolerance for high-beam currents and offers stability against vigorous plasma cleaning. In addition, the absence of a carbon background simplifies the materials analysis of carbon-containing materials using EDX and EELS. Any organic signatures are a direct reflection of the composition of the sample.

Ideal Substrate for High-Resolution Imaging and Analysis

These properties improve sample quality to a great extent, potentially reducing hours of costly TEM time. As a result, UltraSM« Non-Porous Silicon TEM Windows are an ideal sample substrate for high-resolution imaging and for high-beam current analyses such as EDX and EELS.