nanomaterials. Our approaches involved local adjustment of electrostatics at the
surfaces to control material flux. Templating of surface electrostatics was implemented
differently for three broad concepts resulting in control over nanomaterial synthesis,
deposition, and printing. These three general concepts are:
(A) Tailored ZnO nanowire synthesis and integration out of the liquid phase
(B) Arc discharge synthesis and continuous nanocluster deposition from the gas phase
(C) Contact electrification and xerographic printing of nanoparticles from the gas phase
Concept (A): We report a method to fabricate and transfer crystalline ZnO with
control over location, orientation, size, and shape. The process uses an oxygen plasma
treatment in combination with a photoresist pattern on Magnesium-doped GaN substrates
to define narrow nucleation regions and attachment points with 100 nanometer scale
dimensions. Lateral epitaxial overgrowth follows nucleation to produce single crystalline
ZnO which were fabricated into LEDs and photovoltaic cells.
Concept (B): We report a gas phase nanoparticle deposition system which shares
characteristics with liquid phase electrodeposition. Clusters of charged nanoparticles
selectively deposit onto electrically grounded surfaces. Similar to electroplating, the
continued deposition of Au nanoparticles onto underlying resistive traces increased
overall line conductivity. Alternatively, semiconducting ZnO and Ge nanomaterial
sequentially deposited between interdigitated electrodes and served as addressable sensor
Concept (C): We report patterned transfer of charge between conformal material
interfaces through a concept referred to as nanocontact electrification. Nanocontacts of
different size and shape are formed between surface functionalized polydimethylsiloxane (PDMS) stamps and other dielectric materials (PMMA, SiO2). Forced delamination and
cleavage of the interface yields a well defined charge pattern with a minimal feature size
of 100 nm. The process produces charged surfaces and associated fields that exceed the
breakdown strength of air leading to strong long range adhesive forces and force distance
curves which are recorded over macroscopic distances. The process is applied to fabricate
charge patterned surfaces for nanoxerography demonstrating 200 nm resolution
nanoparticle prints and applied to thin film electronics where the patterned charges are
used to shift the threshold voltages of underlying transistors by over 500 mV.
University Ph.D. dissertation. July 2011. Major: Electrical Engineering. Advisor: Heiko O. Jacobs. 1 computer file (PDF); v, 123 pages.
Cole, Jesse J..
Transparent flexible electronics by directed integration of inorganic micro and nanomaterials..
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