Metal patterning is essential to the fabrication of advanced electronic, optical, and mechanical devices. Typical applications include microelectronics, [1] microelectromechanical systems (MEMS), [2][3][4] biological and chemical sensors, [5][6][7][8] microfluidics, [9][10][11][12] display units, and optoelectronic devices. [13] Among existing patterning methods, soft lithography is the most efficient method for fabricating new types of structures and devices on planar, curved, or flexible substrates at low cost. [14] Soft lithography includes a number of nonphotolithographic techniques that use a patterned elastomer, primarily poly(dimethylsiloxane) (PDMS), as a stamp, mold, or mask to transfer a pattern to substrates. [15] Several softlithographic techniques, based on the process of transferring a metal thin film from a stamp to a substrate, have been developed. [16][17][18][19][20][21][22][23][24] Rogers et al. have developed a powerful new method called nanotransfer printing (nTP) for generating a patterned metal film on a substrate. [21][22][23][24] The nTP technique is based on the adhesive transfer of a patterned metal thin film from a stamp to a substrate with tailored surface chemistries.Recently, we developed a new metal transfer printing (mTP) method that is based on the transfer of an Al metal thin film from a stamp to a substrate via a water-mediated surface reaction that forms chemical bonds between the Al film and the substrate. [25,26] In this water-mediated mTP method, the water layer serves as an adhesion layer that provides good conformal contact and enables the formation of strong covalent bonds between the metal thin film and the substrate. The water-mediated mTP method enables the fabrication of 2D and 3D large area Al metal patterns.Here, we report another mTP method based on the watermediated mTP method that uses an Al thin film deposited on a flat glass inkpad. In this water-mediated mTP method involving contact inking, an Al thin film on a glass pad is used as a solid ''ink'' that is transferred from the glass inkpad to the PDMS stamp directly through the interfaces between the pad and the stamp in contact. [27][28][29] The Al thin film on the patterned PDMS stamp is transferred onto a substrate via a water-mediated surface reaction. Compared to previous mTP methods, the PDMS stamp in this method can be used repeatedly without any treatment. The elastomeric properties of the PDMS stamp allow it to recover its original shape, even after undergoing many cycles of pattern transfer. Since treatment of the stamp is not required, continuous printing is possible over large areas. We believe that this contact inking mTP method can be adopted in automated printing machines that are used to generate Al patterns with a wide range of feature sizes. And finally, we also demonstrate the performance of low voltage ZnO thin-film transistors (TFTs) delicately prepared using this mTP method with contact inking on glass substrates. Figure 1 illustrates the procedure for patterning Al films using water-medi...
The direct spontaneous grafting of 4-nitrophenyl molecules onto n-doped hydrogenated amorphous silicon (a-Si:H) surfaces without external ultraviolet, thermal, or electrochemical energy was invegtigated. Clean n-doped a-Si:H thin films were dipped in a solution of 4-nitrobenzenediazonium salts (PNBD) in acetonitrile. After the modified surfaces were rinsed, they were analyzed qualitatively and quantitatively by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). XPS and AFM results show that the reaction of an n-doped a-Si:H thin film with PNBD self-terminates without polymerization, after 5 h, and the surface number density of 4-nitrophenyl molecules is 4.2 x 10(15)/cm2. These results demonstrate that the spontaneous grafting of nitrophenyl layers onto n-doped a-Si:H thin films is an attractive pathway toward forming interfaces between a-Si:H and organic layers under ambient conditions.
A nanocomposite capable of showing a resistance-switching behavior is prepared using novel resistance-switchable fillers embedded in a polymer matrix. The filler in this study employs a conformal passivation layer of highly crystalline TiO₂ on surfaces of conductive Ag nanowires to effectively gate electron flows delivered through the conductive core, resulting in an excellent resistance-switching performance. A nanocomposite prepared by controlled mixing of the resistance-switchable nanowires with a polymer matrix successfully exhibited a resistance-switching behavior of highly enhanced reliability and a resistance on/off ratio, along with flexibility due to the presence of nanowires of a tiny amount. The advantages of our approach include a simple and low-cost fabrication procedure along with sustainable performances suitable for a resistance-switching random-access-memory application.
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