A Study of Electron Beam Induced Deposition and Nano Device Fabrication Using Liquid Cell TEM Technology

Abstract

SiC x nano dots and nano wires with sizes from 60 nm to approximately 2 μm were fabricated using liquid cell transmission electron microscope (TEM) technology. A SiCl 4 in CH 2 Cl 2 solution was sealed between two pieces of Si 3 N 4 window grids in an in situ TEM liquid cell. Focused 200 keV electron beams were used to bombard the sealed precursors, which caused decomposition of the precursor materials, and deposition of the nano materials on the Si 3 N 4 window substrates. The size of nano dots increased with beam exposure time, following an approximately exponential relationship with the beam doses. Secondary electrons are attributed as the primary sources for the Si and C reduction. A nano device was formed from a deposited nano wire, with its electrical property characterized.

Effects Associated with Nanostructure Fabrication Using In Situ Liquid Cell TEM Technology

“…First, we tested the LP-EBID method by depositing nanodots and nanoline structures [ 15 , 23 ]. By focusing the electron beam on the Si 3 N 4 window for various lengths of time, we obtained nanodots of different sizes.…”

“…The scattering of the electron beam in a thick layer of liquid can cause some deterioration in image resolution [ 27 ], depending on the studied liquid materials and instrument factors. Bubbles may form in the liquid cell and significantly reduce the local liquid layer thickness in the cell [ 22 , 23 ]. The image resolution from Fig.…”

“…The secondary electron generation rate might be expected to decrease quickly with lateral distance from the beam center, resulting in a much smaller lateral growth rate at larger d , and thus a small n -value, and dot growth might be biased toward the vertical direction. The yield of Si and C reduction from the EB irradiation may be similar during the deposition; thus, the SiCl 4 concentration change mostly resulted in a composition shift, but did not affect the lateral size of the resulting nanodots under the same accumulated EB dose [ 23 ]. There are some relatively scattered data such as the 4 M, 0.28 nA and the 0 M, 29.5 nA, in which the data above the trend line could be due to some non-ideal beam conditions and the data below the trend line could be related to some growth rate reducing effect under the higher primary beam current, and/or there could be some minor growth rate difference between Si and C.

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“…Liquid precursors were enclosed between two Si 3 N 4 window grids in the in situ cell. The details of the in situ cell structure have been previously reported [ 15 , 23 ]. Metallic thin film spacers of ~100 nm were formed on one of the grids to limit the minimum space between the substrates; however, the typical separation between the Si 3 N 4 windows was generally larger and also varied from place to place because of the Si 3 N 4 window deformation resulting from the clamping pressure.…”

“…Using this technique, researchers have deposited many different nanomaterials, such as silver nanoaggregates, Pt, Pd, and PbS nanomaterials [ 16 – 21 ]. In addition to the relatively irregular-shaped nanomaterials, Grogan et al have demonstrated direct writing of nanoscale Au letters using LP-EBID [ 22 ], and we have demonstrated controlled deposition of Si nanodots, SiC x nanodots, and SiC x nanolines using this technology [ 15 , 23 ].…”