Electrostatic Funneling for Precise Nanoparticle Placement:  A Route to Wafer-Scale Integration

Abstract

We demonstrate a large-scale placement of nanoparticles through a scheme named "electrostatic funneling", in which charged nanoparticles are guided by an electrostatic potential energy gradient and placed on targeted locations with nanoscale precision. The guiding electrostatic structures are defined using current CMOS fabrication technology. The effectiveness of this scheme is demonstrated for a variety of geometries including one-dimensional and zero-dimensional patterns as well as three-dimensional step structures. Placement precision of 6 nm has been demonstrated using a one-dimensional guiding structure comprising alternatively charged lines with line width of approximately 100 nm. Detailed calculations using DLVO theory agree well with the observed long-range interactions and also estimate lateral forces as strong as (1-3) x 10(-7) dyn, which well explains the observed guided placement of Au nanoparticles.

Nanoparticle assembly enabled by EHD-printed monolayers

“…For Au-MHA devices, based on the previously established routes to single-particle assembly 7,8 , 50 nm of Au (with Cr adhesion) was thermally evaporated onto the surface under high vacuum. These surfaces were spin-coated at 4000 rpm with poly(methyl methacrylate) (PMMA) to a 100 nm thickness, which was then patterned by EBL.…”

“…Initially, we looked at templated assembly on SiO 2 surfaces patterned with Au, with a 16-mercaptohexadecanoic acid (MHA) monolayer bound to it (light) and the surrounding surface coated with a monolayer of 3-aminopropyl triethoxysilane (APTES) (dark); the MHA and APTES monolayers are electrostatically repulsive and attractive with respect to the negatively charged, citrate stabilized 20 nm Au particles. This design and assembly process is based on devices that have previously been shown to successfully assemble particles with nanoscale precision 7,8 . This process showed good results, with particles funnelled from the MHA to the APTES surfaces, with features ranging from 100 to 130 nm wide achieving capture of individual particles, showing great exclusivity ( Figure 2).…”

“…Burgeoning methods of additive nanomanufacturing offer a potential solution to this problem, by enabling the top-down integration of existing devices with nanomaterials [1][2][3][4][5][6] , whose properties have demonstrable applications in novel areas of biosensing 4 , single-electron transport 5 , quantum phenomena 6 , and more. These materials can be made to self-assemble into desired configurations via many driving forces, from electrophoresis [7][8][9][10] , DNA-linkages 11,12 and geometrical interactions [13][14][15] . Controlling when and where such self-assembly occurs requires lithography, however, which to integrate with modern device designs must meet sub-100 nm resolution as standard.…”

Assembly of Nanoparticles: Towards Multiscale Three-Dimensional Architecturing

“…Electrostatic funneling was proposed by Ma et al 48) as a way to place nanoparticles onto predefined locations on a substrate in large area. As described in the Fig.…”

Gas Phase Nanoparticle Integration

“…A number of concepts have been developed to print nanoparticles directly from powder and solution. Sub -one micrometer resolution assembly has been accomplished using charge directed nanoxerographic printing [1,2] and topographically directed assembly incorporating both capillary and electrostatic forces [3,4]. While the solution methods have emerged, directed self-assembly processes from the gas phase are not widely available but immensely important.…”