Undercut structures fabricated by microtransfer printing combined with UV exposure and their applications

In this paper. the undercut structures were fabricated by microtransfer printing of metal films on the surface of photoresist combined with UV exposure and photoresist film developing. The patterned metal films were used as mask to realize the selective UV exposure of photoresist Firstly. The undercut structures. which consist of the top metal films and the patterned bottom photoresist, formed in the subsequent developing process because of the lateral dissolving of photoresist at the edge of the unexposed regions. The method proposed in this paper has wider tolerance to the changing of the patterning parameters. but, without effect on patterning resolution since the metal film was used as the top layer. The undercut Structures were Used as separators to pattern passive-matrix display of organic light-emitting diodes (OLEDs). No visible difference of the device performance was observed Compared with the OLEDs patterned by the shadow mask.

Different microstructures of ss-NaYF4 fabricated by hydrothermal process: Effects of pH values and fluoride sources

beta-NaYF4 microcrystals with a variety of morphologies, such as microrod, hexagonal microprism, and octadecahedron, have been synthesized via a facile hydrothermal route. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectra were used to characterize the samples. The intrinsic structural feature of beta-NaYF4 seeds and two important external factors, namely, the pH values in the initial reaction solution and fluoride sources, are responsible for shape determination of beta-NaYF4 microcrystals. It is found that the organic additive trisodium citrate (Cit(3-)) as a shape modifier has the dynamic effect by adjusting the growth rate of different facets under different experimental conditions, resulting in the formation of the anisotropic geometries of various beta-NaYF4 microcrystals. The possible formation mechanisms for products with various architectures have been presented. A systematic study on the photoluminescence of Tb3+-doped beta-NaYF4 samples with rod, prism, and octadecahedral shapes has shown that the optical properties of these phosphors are strongly dependent on their morphologies and sizes.

n-channel, ambipolar, and p-channel organic heterojunction transistors fabricated with various film morphologies

The relationship between the performance characteristics of organic field-effect transistors (OFETs) with 2,5-bis(4-biphenylyl)-bithiophene/copper hexadecafluorophthalocyanine (BP2T/F16CuPc) heterojunctions and the thickness of the BP2T bottom layer is investigated. Three operating modes (n-channel, ambipolar, and p-channel) are obtained by varying the thickness of the organic semiconductor layer. The changes in operating mode are attributable to the morphology of the film and the hetero-junction effect, which also leads to an evolution of the field-effect mobility with increasing film thickness. In BP2T/F16CuPc heterojunctions the mobile charge carriers accumulate at both sides of the heterojunction interface, with an accumulation layer thickness of ca. 10 nm. High field-effect mobility values can be achieved in continuous and flat films that exhibit the heterojunction effect.

Heterojunction ambipolar organic transistors fabricated by a two-step vacuum-deposition process

Ambipolar organic field-effect transistors (OFETs) are produced, based on organic heterojunctions fabricated by a two-step vacuum-deposition process. Copper phthalocyanine (CuPc) deposited at a high temperature (250 degrees C) acts as the first (p-type component) layer, and hexadecafluorophthalocyaninatocopper (F16CuPc) deposited at room temperature (25 degrees C) acts as the second (n-type component) layer. A heterojunction with an interpenetrating network is obtained as the active layer for the OFETs. These heterojunction devices display significant ambipolar charge transport with symmetric electron and hole mobilities of the order of 10(-4) cm(2) V-1 s(-1) in air. Conductive channels are at the interface between the F16CuPc and CuPc domains in the interpenetrating networks. Electrons are transported in the F16CuPc regions, and holes in the CuPc regions. The molecular arrangement in the heterojunction is well ordered, resulting in a balance of the two carrier densities responsible for the ambipolar electrical characteristics. The thin-film morphology of the organic heterojunction with its interpenetrating network structure can be controlled well by the vacuum-deposition process.

Surface enhanced Raman scattering of p-aminothiophenol self-assembled monolayers in sandwich structure fabricated on glass

A sandwich structure consisting of Ag nanoparticles (NPs), p-aminothiophenol (p-ATP) self-assembled monolayers (SAMs), and Ag NPs was fabricated on glass and characterized by surface enhanced Raman scattering (SERS). The SERS spectrum of a p-ATP SAM in such sandwich structure shows that the electromagnetic enhancement is greater than that on Ag NPs assembled on glass. The obtained enhancement factors (EF) on solely one sandwich structure were as large as 6.0 +/- 0.62x10(4) and 1.2 +/- 0.62x10(7) for the 7a and 3b(b(2)) vibration modes, respectively. The large enhancement effect of p-ATP SAMs is likely a result of plasmon coupling between the two layers of Ag NP (localized surface plasmon) resonance, creating a large localized electromagnetic field at their interface, where p-ATP resides. Moreover, the fact that large EF values (similar to 1.9 +/- 0.7x10(4) and 9.4 +/- 0.7x10(6) for the 7a- and b(2)-type vibration modes, respectively) were also obtained on a single sandwich structure of Au NPs/p-ATP SAMs/Ag NPs in the visible demonstrates that the electromagnetic coupling does not exist only between Ag NPs but also between Au and Ag NPs.

Organic integrated pixels fabricated by a full evaporation method

An organic integrated pixel consisting of an organic light-emitting diode driven by an organic thin-film field-effect transistor (OTFT) was fabricated by a full evaporation method oil a transparent glass substrate. The OTFT was designed as a top-gate Structure, and the insulator is composed of a double-layer polymer of Nylon 6 and Teflon to lower the operation voltage and the gate-leakage current, and improve the device stability. The field-effect mobility of the OTFT is more than 0.5 cm(2) V-1 s(-1), and the on/off ratio is larger than 10(3). The brightness of the pixel reached as large as 300 cd m(-2) at a driving current of 50 mu A.

Patterning and optical properties rhodamine B-doped organic-inorganic silica films fabricated by sol-gel soft lithography

Rhodamine B (RB)-doped organic-inorganic silica films and their patterning were fabricated by a sol-gel process combined with a soft lithography. The resulted film samples were characterized by atomic force microscope (AFM), optical microscope and UV/Vis absorption and photoluminescence excitation and emission spectra. The effects of the concentration of the RB dye and heat treatment temperature on the optical properties of the hybrid silica films have been studied. Four kinds of patterning structures with film line widths of 5, 10, 20 and 50 mum have been obtained by micromolding in capillaries by a soft lithography technique. The RB-doped hybrid silica films present a red color, with an excitation and emission bands around 564 and 585 mum, respectively. With increasing the RB concentration, the emission intensity of the RB-doped hybrid silica films increases and the emission maximum presents a red shift. The emission intensity of the films decreases with increasing the heat treatment temperatures.