Selective patterning of ZnO nanorods on silicon substrates using nanoimprint lithography

In this research, nanoimprint lithography (NIL) was used for patterning crystalline zinc oxide (ZnO) nanorods on the silicon substrate. To fabricate nano-patterned ZnO nanorods, patterning of an n-octadecyltrichlorosilane (OTS) self-assembled monolayers (SAMs) on SiO2 substrate was prepared by the polymer mask using NI. The ZnO seed layer was selectively coated only on the hydrophilic SiO2 surface, not on the hydrophobic OTS SAMs surface. The substrate patterned with the ZnO seed layer was treated with the oxygen plasma to oxidize the silicon surface. It was found that the nucleation and initial growth of the crystalline ZnO were proceeded only on the ZnO seed layer, not on the silicon oxide surface. ZnO photoluminescence spectra showed that ZnO nanorods grown from the seed layer treated with plasma showed lower intensity than those untreated with plasma at 378 nm, but higher intensity at 605 nm. It is indicated that the seed layer treated with plasma produced ZnO nanorods that had a more oxygen vacancy than those grown from seed layer untreated with plasma. Since the oxygen vacancies on ZnO nanorods serve as strong binding sites for absorption of various organic and inorganic molecules. Consequently, a nano-patterning of the crystalline ZnO nanorods grown from the seed layer treated with plasma may give the versatile applications for the electronics devices

Structure and Photoluminescent Properties of ZnO Encapsulated in Mesoporous Silica SBA-15 Fabricated by Two-Solvent Strategy

The two-solvent method was employed to prepare ZnO encapsulated in mesoporous silica (ZnO/SBA-15). The prepared ZnO/SBA-15 samples have been studied by X-ray diffraction, transmission electron microscope, X-ray photoelectron spectroscopy, nitrogen adsorption–desorption isotherm, and photoluminescence spectroscopy. The ZnO/SBA-15 nanocomposite has the ordered hexagonal mesostructure of SBA-15. ZnO clusters of a high loading are distributed in the channels of SBA-15. Photoluminescence spectra show the UV emission band around 368 nm, the violet emission around 420 nm, and the blue emission around 457 nm. The UV emission is attributed to band-edge emission of ZnO. The violet emission results from the oxygen vacancies on the ZnO–SiO2interface traps. The blue emission is from the oxygen vacancies or interstitial zinc ions of ZnO. The UV emission and blue emission show a blue-shift phenomenon due to quantum-confinement-induced energy gap enhancement of ZnO clusters. The ZnO clusters encapsulated in SBA-15 can be used as light-emitting diodes and ultraviolet nanolasers

Molecular monolayer modification of the cathode in organic light-emitting diodes

The effects of alkanethiol self-assembled monolayers (SAMs) attached to the gold cathode of organic light-emitting diodes made by soft contact lamination are investigated. In spite of reported work function lowering by alkanethiol SAMs, the results from this work showed that their primary effect in carrier transport is to act as a thin insulating layer, causing current reduction. At the same time, the luminescence efficiency was enhanced because the SAMs reduce exciton quenching by the metal cathode. A two-order-of-magnitude enhancement at light emission onset was observed for a hexadecanethiol modified device. (c) 2006 American Institute of Physics.open111113sciescopu

High-efficiency soft-contact-laminated polymer light-emitting devices with patterned electrodes

Organic light-emitting devices (OLEDs) formed by soft-contact lamination (ScL) show high luminous efficiency (similar to 2.25 cd A(-1) with a Au electrode) and better operational stability than similar devices fabricated by thermal evaporation. The laminated electrodes consist of thin films of Au supported by flat or structured elastomeric elements of polydimethylsiloxane. By combining ScL and soft lithography, it is possible to fabricate high-efficiency OLEDs with micrometer-scale light-emitting areas.X1137sciescopu

Organic light-emitting diodes formed by soft contact lamination (vol 101, pg 429, 2004)

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SOFT-CONTACT OPTICAL LITHOGRAPHY USING TRANSPARENT ELASTOMERIC STAMPS: APPLICATION TO NANOPATTERNED ORGANIC LIGHT-EMITTING DEVICES

Conventional photolithography uses rigid photomasks of fused quartz and high-purity silica glass plates covered with patterned microstructures of an opaque material. We introduce new, traneparent, elastomeric molds (or stamps) of poly(dimethylsiloxane) (PDMS) that can be employed as photomasks to produce the same resist patten of the recessed (or non-contact) regions of stamps, in contrast to other reports in the literature([1]) of using PDMS is lower than that of the contact regions. Therfore, we employ a difference in the effective exposure dose between the contact and non-contact regions through the PDMS stamp to generate the same pattern as the PDMS photomask. The photomasking capability of the PDMS stamps, which is similar to rigid photomasks in conventional photolithography, widens the application boundaries of soft-contact optical lithography and makes the photolithography process and equipment very simple. This soft-contact optical lithogarphy process can be widely used to perform photolithography on flexible substrates, avoiding metal or resist cracks, as it uses soft, conformable, intimate contact with photoresist without any external pressure. To this end, we demonstrate soft-contact optical lithography on the gold-coated PDMS substrate and utilized the patterned Au/PDMS substrate with feature sizes into the nanometer regime as a top electrode in organic light emitting diodes that are formed by soft-contact lamination.X1142sciescopu