(Color online) (a) Schematic illustrating that an upright nanopost has a higher secondary-electron yield when scanned by an electron beam compared to a collapsed nanopost. (b) SEM image of an array of nanoposts showing that as a result of the higher yield of secondary electrons in an upright nanopost, they appear “brighter” in the SEM image than nanoposts that have fallen over. (c) Schematic of the concept used to achieve pixels of varying brightness when imaged in a SEM.
(Color online) (a) JPEG image of the 1948 mezzotint by M. C. Escher entitled “Dewdrop,” which illustrates a dewdrop on a leaf from a succulent plant. (b) Pixel maps consisting of increasing number of dots arranged in different configurations to achieve varying brightness levels of 0–16. (c) An enlarged view of the dashed region in the image in (a) which was an 8 bit grayscale with 256 possible brightness levels (shades of gray) for each pixel. (d) The same region of the image reduced to only 17 brightness levels, which closely resembles (c) without a noticeable loss of information. (e) The pattern layout for the corresponding region where brightness levels have been converted to dots of varying density using the pixel map in (b).
(a) SEM image of the miniaturized version of the original image showing an accurate reproduction with ∼200 nm details (e.g., the individual veins of the leaf) clearly visible. (b) An enlarged SEM view of the corresponding portion of the leaf as in Fig. 2(e) showing the individual nanoposts, which make up the image appearing as bright dots. Inset shows a larger-view SEM of the individual nanopost arrays with identifiable pixel maps within them.
(Color online) (a) Original grayscale version of the Lena test image commonly used in image processing studies. (b) The same image after down-sampling to 17 grayscale levels. (c) SEM image of the miniaturized Lena image reproducing the subtle gray levels of the original. (d) SEM image of an enlarged view of the patterned image showing that fine details were preserved by the process. (e) SEM image of the varying densities of individual nanoposts that made up the patterned image with center-to-center distances as low as 20 nm. (i–iii) Plots of brightness levels (in arbitrary units and vertically stacked for clarity) vs position taken along the lines as indicated in (a–c) showing the quantization steps in (ii) and image speckle noise in (iii).
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