Micro- and nano-scale molds were fabricated using nanocrystalline diamond (nano-diamond)
and diamond-like carbon (DLC) films for imprinting lithography. Patterning was first transferred
to the resist on nano-diamond and DLC thin films by photolithography and imprint lithography
methods, and then deep etching with inductively-coupled plasma reactive ion etching (ICP-RIE) was
applied to transfer patterns to nano-diamond and DLC films for the fabrication of diamond molds.
Nano-diamond films of about 1.5μm in thickness were deposited on silicon substrates by hot
filament chemical vapor deposition (HFCVD) by controlling CH<sub>4</sub>/H<sub>2</sub> ratios and substrate
temperatures. Thick diamond-like carbon films containing silicon oxide nanoparticles were
deposited on silicon substrates by PECVD using gaseous HMDSO (Hexamethyldisiloxane) reactants
to release the film stress. E-beam writer was used to pattern the resist on the Cr film-covered thick
DLC film. By using ICP-RIE, Cr film was first patterned with the patterned e-beam resist as the
etching mask, and then DLC thick film was etched to form nanoimprint mold using the patterned Cr
as the etching mask. High fidelity nano-patterns were transferred with nano-imprinting lithography
using the nano-diamond and DLC molds. Good mold releasing behavior and high mold strength
were observed for the nanocrystalline diamond and DLC molds due to their highly hydrophobic
surface and high toughness, respectively.
A two-dimensional photonic crystal (PC) structure introduced into the anode layer of an organic light-emitting diode (OLED) was designed to enhance the light extraction efficiency. Using the plane wave expansion method and the finite-difference time-domain method to simulate the optical properties, we found that the extraction efficiency of the OLED device can be greatly enhanced by modifying the lattice constant of the PC array. In our simulation results, the enhancement of the extraction efficiency can approach 60% for the optimized square PC pattern with a period of ~500nm in the OLED device emitting at the center wavelength of 510nm. In this work, the PC pattern was also fabricated to implement the simulation results via the UV-curing nano-imprint technique. To maximize the enhancement effect, the residual layer on the imprinted surface should be really thin over a large area and could thus be easily removed by the RIE process.