One nanometer structure fabrication using electron beam induced deposition

We have recently demonstrated that electron beam induced deposition can be used to fabricate structures that are much smaller than was generally believed, even as small as 1 nm in size. When fabricating arrays of such small structures a spread in deposited mass is observed, as well as a spread in position of the deposit with respect to the intended array position. In this work we study the distribution of masses by analysing arrays of tungsten containing dots, deposited on 10 nm thick carbon foils, at decreasing deposition times. The observed distributions of mass resemble closely a Poisson distribution, and the average amount of mass deposited in a dot is found to decrease linearly with decreasing deposition time. As the number of atoms in such small deposits is getting very small (of the order of 100) the statistical variations are becoming significant. This may set a limit on the accuracy with which structure sizes can be defined.