Thin films made from transparent conducting oxide (TCO) nanocrystals are promising alternatives to traditional vacuum-sputtered films. However, the material properties of nanocrystal-derived thin films are dependent upon the doping levels and sizes of the nanocrystal building blocks. To date, a lack of deliberate and precise control over size in TCO nanocrystals has hindered the investigation of how nanocrystal size affects the optoelectronic properties of the resulting thin films. Here, this gap is addressed through the use of a synthetic approach that produces a series of uniform nanocrystals with tunable, well-defined sizes with nanometer resolution. A size ladder of Sn-doped In 2 O 3 (ITO) nanocrystals, containing seven samples ranging from 5 to 21 nm in diameter, was synthesized sequentially under the same reaction conditions in a single slow-injection reaction. The nanocrystals displayed constant dopant levels, homogeneous dopant distributions, and high carrier concentrations (∼10 21 cm −3 ) across all sizes produced. The ITO nanocrystals were solution-deposited into thin films and processed under mild conditions. For all nanocrystal sizes, the films were smooth and crack-free and exhibited >95% optical transparency. The resistivities of the thin films decrease over an order of magnitude, from 5.0 × 10 −2 to 4.5 × 10 −3 Ω cm for the 5.3 and 21.5 nm samples, respectively. Larger nanocrystals exhibit lowered thin film resistivities due to decreased coulombic charging energy, decreased electron surface scattering, and reduced interface density.

Three organotin carboxylate species stabilized by the same ligands, but varying in size and structure, were studied to elucidate the effects of the structure on reactivity in the context of direct-write electron beam patterning. The chemical reactions that occur between the organotin reagents and the electron beam, the patterned film products, and the ligand decomposition and desorption byproducts were compared across all species. We found that both the metal−oxo content and the ligand coordination mode of each organotin reagent affected the reaction efficiency during electron beam patterning. In each case, an insoluble metal−oxo product formed after irradiation, but the composition, structure, and surface morphology of the products were nearly indistinguishable from the initial films. Examining the byproducts of the irradiation chemistry using electron-stimulated desorption confirmed that many of the organic ligands remained in the film during the reaction, likely crosslinking the clusters together to form a metal−oxo polymer product. Finally, we discuss the implications of the chemical transformations that occur during patterning for the use of these organotin reagents as both photoresists for lithography and direct-write functional nanomaterials.

A series of five organotin carboxylates of the type [RSn(O)O 2 CR'] 6 containing n-butyl ligands and carboxylates ranging in size from formate to diphenylacetate were synthesized and examined by single crystal X-ray diffraction. The crystal and packing structures of each compound were compared with regards to the steric and intermolecular forces of the varying carboxylate groups in order to aid the understanding of how these same factors relate to irradiation trends in EUV lithography of thin films. The trends found are compared to other factors that may also dictate resist formation in order to elucidate a fuller picture of the chemical transformations that occur when patterning inorganic materials.

No abstract