Downsizing Has Its Rewards

New Theory has Guided Experiments for Making the Smallest Possible Metal Rods Useful as Air-tight Sealants.

Image courtesy of Hanchen Huang, Northeastern University
Copper (Cu) nanorods grown using physical vapor deposition.

The Science

A newly developed theory of nanorod growth has guided the experimental realization of smallest (~10 nm diameter) metallic nanorods ever reported for physical vapor deposition. Now, using this process, well-separated silver nanorods were grown that were shown to be excellent air-tight sealants that form at room temperature in air, under a small pressure (~10 MPa).

The Impact

This low-cost, simple metallic sealant displays 1,000 times better leak resistance compared to polymeric seals and meets the industry standard for organic solar cell packaging.

Summary

A newly developed theory has guided the identification of processing conditions needed to experimentally realize the smallest metallic nanorods (~10 nm) ever reported for physical vapor deposition. The theory explains and predicts how nanorods grow when they are physically deposited on a surface through a gas, incorporating dynamic processes and the never before considered multiple-layers of steps on the surface. The smallest diameter of nanorods can therefore be defined as a function of processing conditions, such as substrate temperature and deposition rate, as well as materials properties. This growth technique has allowed the design of nanorods with a separation to be larger than the smallest diameter, so that well-separated nanorods are realized. Moreover, silver nanorods made with this technique have been shown to function as an air-tight sealant that forms at room temperature in air, under a small pressure (~10MPa). This low cost simple metallic sealant displays 1,000 times better leak resistance compared to polymeric sealants and meets the industry standard for organic solar cell (OSC) packaging and organic light emitting diodes. The metal sealants not only prevent moisture and water vapor from degrading the OSCs, but also do not degrade from exposure to the sun compared to polymeric sealants currently in use. In addition, these nanorod-based sealants can be processed without the need for high temperature, high pressure, and/or vacuum.

Contact

Hanchen Huang
Northeastern University
h.huang@neu.edu

Funding

DOE Office of Science, Basic Energy Science program, including use of the Center for Integrated NanoTechnologies User Facility.

Publications

Xiaobin Niu, Stephen Stagon, Hanchen Huang, J. Kevin Baldwin, and Amit Misra,”Smallest Metallic Nanorods Using Physical Vapor Deposition”, Physical Review Letters 110, 136102 (2013). [DOI: 10.1103/PhysRevLett.110.136102].

Stephen Stagon and Hanchen Huang, “Airtight Metallic Sealing at Room Temperature under Small Mechanical Pressure” Nature Scientific Reports 3,3066 (2013). [DOI: 10.1038/srep03066].

Related Links

Highlight by APS (and picked as Editor’s Suggestion): http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.110.136102

News report by UCONN Today: http://today.uconn.edu/blog/2013/05/uconn-researchers-develop-some-of-the-worlds-smallest-metallic-nanorods/

News report by Northeastern University: http://www.northeastern.edu/news/2014/01/huang/

Highlight Categories

Program: BES , MSE

Performer: SC User Facilities , BES User Facilities , CINT