Nanocrystal Film Patterning by Inhibiting Cation Exchange via Electron-Beam or X‑ray Lithography
Citation: Liberato Manna and Roman Krahne (2014/03/04) Nanocrystal Film Patterning by Inhibiting Cation Exchange via Electron-Beam or X‑ray Lithography. Nano Lett., 2014, 14, 2116-2122 (RSS)
DOI (original publisher): 10.1021/nl500349j
Semantic Scholar (metadata): 10.1021/nl500349j
Sci-Hub (fulltext): 10.1021/nl500349j
Internet Archive Scholar (search for fulltext): Nanocrystal Film Patterning by Inhibiting Cation Exchange via Electron-Beam or X‑ray Lithography
Tagged: Chemistry
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Summary
The paper discusses at length, a method to pattern nanocrystals (NCs) by selectively masking the surface using chemical controls. Other methods of patterning include controlled dewetting of NC solution, selective deposition into etched trenches, dip pen lithography, doctor-blading & inkjet printing. The paper’s core contribution towards lithography lies in the fact that the exposure of NC film to electron beam or X-ray beam acts to inhibit local cationic exchange. NCs of CdSe/CdS are used to deposit a homogenous NC film on a substrate such that the thickness of the film is of the range of a few monolayers. The methods used for the deposition could be spin coating or layer-by-layer deposition. According to the paper, the film is then exposed to an electron beam having an acceleration voltage of 10 kV. The exposure dose of the beam lies within the range 0.1-20 mC/cm2 immersed in a Cu(I) complex so as to carry out cation exchange. The CdSe/CdS are thus converted to Cu2-xSe/Cu2-xS. This patterns the film. The paper argues that when NC film is exposed to high energy electron beam, ligand molecules cross-link and thereby, deactivate the corresponding NC surface. On the other hand, cation exchange occurs only on the non-radiated parts of the NC surface. This reasoning is supported by confocal imaging data wherein CdSe/CdS NCs (irradiated parts) exhibit bright photoluminescence in visible region while Cu2-xSe/Cu2-xS NCs (non-radiated parts) do not emit in spectral range. Also, Cu2-xSe/Cu2-xS shows appreciable conductivity while the former doesn’t carry current. These findings have potential applications in opto-electronics (eg., designing microchips) and can form the basis of integrated circuits in time to come.
