Nanotransfer Printing Research Articles

Fabrication of a wafer-scale uniform array of single-crystal organic nanowire complementary inverters by nanotransfer printing

Abstract We report the fabrication and electrical characterization of a wafer-scale array of organic complementary inverters using single-crystal 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-PEN) and fullerene (C60) nanowires as p- and n-channels, respectively. Two arrays of single-crystal organic nanowires were generated consecutively on desired locations of a common substrate with a desired mutual alignment by a direct printing method (liquid-bridge-mediated nanotransfer molding). Another direct printing of silver micron scale structures, as source and drain electrodes, on the substrate with the two printed nanowire arrays produced an array of complementary inverters with a bottom gate, top contact configuration. Field-effect mobilities of single-crystal TIPS-PEN and C60 nanowire field-effect transistors (FETs) in the arrays were uniform with 1.01 ± 0.14 and 0.10 ± 0.01 cm2V−1 s−1, respectively. A wafer-scale array of complementary inverters produced all by the direct printing method showed good performance with an average gain of 25 and with low variations among the inverters.

Uniformly embedded silver nanomesh as highly bendable transparent conducting electrode

Ag-nanomesh-based highly bendable conducting electrodes are developed using a combination of metal nanotransfer printing and embossing for the 6-inch wafer scale. Two Ag nanomeshes, including pitch sizes of 7.5 and 10 μm, are used to obtain highly transparent (approximately 85% transmittance at a wavelength of 550 nm) and electrically conducting properties (below 10 Ω sq−1). The Ag nanomeshes are also distinguished according to the fabrication process, which is called transferred or embedded Ag nanomesh on polyethylene terephthalate (PET) substrate, in order to compare their stability against bending stress. Then the enhancement of bending stability when the Ag nanomesh is embedded in the PET substrate is confirmed.

Fabrication of nanostep for total internal reflection fluorescence microscopy to calibrate in water

Total internal reflection fluorescence microscopy (TIRFM) is a powerful tool for analyzing x–y–z (3D) fluid flow in nano- or micro-channel. To visualize the 3D fluid flow via TIRFM, intensity calibration of a fluorescent particle is required by using calibration plates, carrying a set of nano-steps of different heights. In an attempt to fabricate a calibration plate to be used in water ambient we employed a polymer with a refractive index close to that of water. In this study, we have developed a lift-off technique for making polymer resin pattern on a glass substrate by employing the use of polyvinyl alcohol film and metal mask previously fabricated by nano transfer printing (nTP). In summary, we have succeeded in the fabrication of nanosteps made of a polymer resin and used it for the calibration of the fluorescence intensity in water.

Cross-stacked single-crystal organic nanowire p-n nanojunction arrays by nanotransfer printing.

We fabricated cross-stacked organic p-n nanojunction arrays made of single-crystal 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-PEN) and fullerene (C60) nanowires as p-type and n-type semiconductors, respectively, by using a nanotransfer printing technique. Single-crystal C60 nanowires were synthesized inside nanoscale channels of a mold and directly transferred onto a desired position of a flexible substrate by a lubricant liquid layer. In the consecutive printing process, single-crystal TIPS-PEN nanowires were grown in the same way and then perpendicularly aligned and placed onto the C60 nanowire arrays, resulting in a cross-stacked single-crystal organic p-n nanojunction array. The cross-stacked single-crystal TIPS-PEN/C60 nanowire p-n nanojunction devices show rectifying behavior with on/off ratio of ∼ 13 as well as photodiode characteristic with photogain of ∼ 2 under a light intensity of 12.2 mW/cm(2). Our study provides a facile, solution-processed approach to fabricate a large-area array of organic crystal nanojunction devices in a desired arrangement for future nanoscale electronics.

High-resolution nanotransfer printing applicable to diverse surfaces via interface-targeted adhesion switching.

Nanotransfer printing technology offers outstanding simplicity and throughput in the fabrication of transistors, metamaterials, epidermal sensors and other emerging devices. Nevertheless, the development of a large-area sub-50 nm nanotransfer printing process has been hindered by fundamental reliability issues in the replication of high-resolution templates and in the release of generated nanostructures. Here we present a solvent-assisted nanotransfer printing technique based on high-fidelity replication of sub-20 nm patterns using a dual-functional bilayer polymer thin film. For uniform and fast release of nanostructures on diverse receiver surfaces, interface-specific adhesion control is realized by employing a polydimethylsiloxane gel pad as a solvent-emitting transfer medium, providing unusual printing capability even on biological surfaces such as human skin and fruit peels. Based on this principle, we also demonstrate reliable printing of high-density metallic nanostructures for non-destructive and rapid surface-enhanced Raman spectroscopy analyses and for hydrogen detection sensors with excellent responsiveness.

Single-crystal poly(3,4-ethylenedioxythiophene) nanowires with ultrahigh conductivity.

We developed single-crystal poly(3,4-ethylenedioxythiopene) (PEDOT) nanowires with ultrahigh conductivity using liquid-bridge-mediated nanotransfer printing with vapor phase polymerization. The single-crystal PEDOT nanowires are formed from 3,4-ethylenedioxythiophene (EDOT) monomers that are self-assembled and crystallized during vapor phase polymerization process within nanoscale channels of a mold having FeCl3 catalysts. These PEDOT nanowires, aligned according to the pattern in the mold, are then directly transferred to specific positions on a substrate to generate a nanowire array by a direct printing process. The PEDOT nanowires have closely packed single-crystalline structures with orthorhombic lattice units. The conductivity of the single-crystal PEDOT nanowires is an average of 7619 S/cm with the highest up to 8797 S/cm which remarkably exceeds literature values of PEDOT nanostructures/thin films. Such distinct conductivity enhancement of single-crystal PEDOT nanowires can be attributed to improved carrier mobility in PEDOT nanowires. To demonstrate usefulness of single-crystal PEDOT nanowires, we fabricated an organic nanowire field-effect transistor array contacting the ultrahigh conductive PEDOT nanowires as metal electrodes.

Molybdenum Disulfide Nanoflake–Zinc Oxide Nanowire Hybrid Photoinverter

We demonstrate a hybrid inverter-type nanodevice composed of a MoS2 nanoflake field-effect transistor (FET) and ZnO nanowire Schottky diode on one substrate, aiming at a one-dimensional (1D)-two-dimensional (2D) hybrid integrated electronic circuit with multifunctional capacities of low power consumption, high gain, and photodetection. In the present work, we used a nanotransfer printing method using polydimethylsiloxane for the fabrication of patterned bottom-gate MoS2 nanoflake FETs, so that they could be placed near the ZnO nanowire Schottky diodes that were initially fabricated. The ZnO nanowire Schottky diode and MoS2 FET worked respectively as load and driver for a logic inverter, which exhibits a high voltage gain of ∼50 at a supply voltage of 5 V and also shows a low power consumption of less than 50 nW. Moreover, our inverter effectively operates as a photoinverter, detecting visible photons, since MoS2 FETs appear very photosensitive, while the serially connected ZnO nanowire Schottky diode was blind to visible light. Our 1D-2D hybrid nanoinverter would be quite promising for both logic and photosensing applications due to its performance and simple device configuration as well.

Controllable and Facile Fabrication of Gold Nanostructures for Selective Metal‐Assisted Etching of Silicon

A method with the combination of organic-vapor-assisted polymer swelling and nanotransfer printing (nTP) is used to manufacture desirable patterns consisting of gold nano-clusters on silicon wafers for Au-assisted etching of silicon. This method remarkably benefits to the size control and regional selection of the deposited Au. By tuning the thickness of the Au films deposited on the polydimethylsiloxane (PDMS) stamps, along with the swelling of PDMS stamps in acetone atmosphere, the Au films are cracked into diverse nanostructures. These nanostructures are covalently transferred onto silicon substrates in a large scale and enable to accelerate the chemical etching of silicon. The etched areas are composed of porous structures which can be readily distinguished from the surroundings on optical microscope. PDMS stamps and the Au clusters provide the control over the feature of the etched areas and the porous silicon, respectively. The silicon surfaces with patterned porous features offer a platform for exploiting new functional templates, for example, they present a diversity of antireflective and fluorescent performance.

Negative Index Materials: Materials Selections and Growth Conditions for Large‐Area, Multilayered, Visible Negative Index Metamaterials Formed by Nanotransfer Printing (Advanced Optical Materials 3/2014)

Negative Index Materials: Materials Selections and Growth Conditions for Large‐Area, Multilayered, Visible Negative Index Metamaterials Formed by Nanotransfer Printing (Advanced Optical Materials 3/2014)

Nanotransfer printing of gold disk, ring and crescent arrays and their IR range optical properties

We demonstrate a facile method to fabricate gold plasmonic microstructures based on the combination of colloidal lithography and a nanotransfer printing method. Poly(dimethylsiloxane) PDMS hemisphere arrays were fabricated through colloidal lithography and used as a “stamp” for the nanotransfer printing. Three kinds of plasmonic microstructures, gold disk, ring and crescent arrays, were fabricated by transferring gold “ink” onto the PDMS stamp, then to the substrate based on covalent “glue”. By adjusting the pressure applied during the printing process, the diameter of the as-prepared gold disks and gold rings can be precisely controlled, and these plasmonic arrays all exhibited significant diameter dependent LSPR properties in the NIR or Mid-IR range. In addition, by obliquely depositing gold ink onto the PDMS stamp, a gold crescent array with asymmetrical geometry was also prepared on the substrate. Owing to the asymmetric structure of the gold crescents, the gold crescent array showed significant polarization dependent LSPR properties in the Mid-IR range. We believe that these as-prepared gold plasmonic microstructures could show promising potential for application as real-time, label-free plasmonic sensing platforms in the IR range.

22am2-A6 ポリビニルアルコール薄膜への金属パターン転写技術を用いた全反射照明蛍光顕微鏡用校正プレートの作製

Total internal reflection fluorescence microscopy (TIRFM) has gotten a lot of attention because it is very useful for analyzing fluid flow in nano- or micro-channel. To calibrate the intensity of a fluorescent particle in water ambient, a nano-step pattern, whose refractive index is same to the working fluid, is needed. Therefore, we employed a polymer with a refractive index close to that of water. In this study, we have developed a lift-off technique for making polymer nano-step pattern on a glass substrate by using polyvinyl alcohol film and metal mask obtained by nano transfer printing (nTP). In summary, we have succeeded in the calibration of the fluorescence intensity of a particle in water.

Materials Selections and Growth Conditions for Large‐Area, Multilayered, Visible Negative Index Metamaterials Formed by Nanotransfer Printing

Materials Selections and Growth Conditions for Large‐Area, Multilayered, Visible Negative Index Metamaterials Formed by Nanotransfer Printing

나노 공진기의 1차 고유진동수에 미치는 링클 영향 연구

Natural frequency of a nano-resonator via nano transfer printing is studied. Through a nano transfer printing, the hybrid metal/polymer membrane may evolve a wrinkle. Natural frequency of a wrinkled hybrid membrane decreases significantly, as the amplitude to wavelength ratio becomes larger. To address the design limit of a hybrid nano resonator, we perform parametric study using finite element analysis. Specifically, we study the effects of the Young's modulus ratio of the metal/polymer membrane, thickness ratio and wrinkle amplitude to wavelength ratio, respectively. The results from the parametric studies can serve as guideline to design hybrid nano resonators.

Structure Dependence of the Intermediate-Frequency Raman Modes in Isolated Single-Walled Carbon Nanotubes

Resonance Raman spectra in the intermediate- frequency mode (IFM) region have been studied for isolated single- walled carbon nanotubes (SWNTs) at the single-nanotube level. The SWNT samples with diameter in the range of 0.8−2.0 nm are first grown on quartz substrate and then transferred to silicon substrate by nanotransfer printing technique. A specific linear relation of ωRBM = 222.0/dt + 8.0 is found to best suit for our transferred isolated SWNTs. By measuring more than 80 isolated SWNTs with 36 different assigned chiralities using five different excitation lasers, the dependence of the nondispersive out-of-plane transverse optical (oTO) and the dispersive IFM − and IFM + features on the nanotube structure has been determined. It is found that the oTO, IFM − , and IFM + frequencies decrease slightly, decrease significantly, and increase slightly with decreasing nanotube diameter, respectively. The appearance of the oTO band is indifferent to SWNT chirality or type, while the IFM − feature can only be observed in metallic or MOD1 semiconducting nanotubes with small chiral angles. The IFM − feature in resonance Raman spectra thus offers a method to distinguish small θ nanotubes from large θ nanotubes and distinguish MOD1 semiconducting nanotubes from MOD2 semiconducting nanotubes.

Probing the adhesion of submicron thin films fabricated on a polymer substrate via nano-transfer printing

Determining the interfacial adhesion of ultrathin functional films in micro-electro-mechanical systems (MEMS) and nano-electro-mechanical systems (NEMS) becomes increasingly crucial for optimal design of MEMS/NEMS devices. However, direct measurement of adhesion properties of ultrathin films can be challenging, as the traditional metrology of adhesion at macroscopic scales becomes unsuitable in dealing with samples of extremely small dimension. In this paper, we present a feasible and robust approach combining nano-transfer printing (nTP) experiments and mechanics modeling to quantitatively determine the interfacial adhesion of submicron thin films. We show that the measurements of the interfacial adhesion of a submicron polycarbonate (PC) thin film on a PC substrate at multiple locations in multiple samples agree within 7.3%, demonstrating the accuracy and robustness of our approach. Given the versatility of the nTP process, the approach demonstrated in this paper is expected to be generally applicable to measure the adhesion of interfaces of other material combinations. In this sense, this study sheds light on better understanding of the adhesive properties of functional interfaces in MEMS and NEMS.

Tunneling Characteristics of Au–Alkanedithiol–Au Junctions formed via Nanotransfer Printing (nTP)

Construction of permanent metal-molecule-metal (MMM) junctions, though technically challenging, is desirable for both fundamental investigations and applications of molecule-based electronics. In this study, we employed the nanotransfer printing (nTP) technique using perfluoropolyether (PFPE) stamps to print Au thin films onto self-assembled monolayers (SAMs) of alkanedithiol formed on Au thin films. We show that the resulting MMM junctions form permanent and symmetrical tunnel junctions, without the need for an additional protection layer between the top metal electrode and the molecular layer. This type of junction makes it possible for direct investigations into the electrical properties of the molecules and the metal-molecule interfaces. Dependence of transport properties on the length of the alkane molecules and the area of the printed Au electrodes has been examined systematically. From the analysis of the current-voltage (I-V) curves using the Simmons model, the height of tunneling barrier associated with the molecule (alkane) has been determined to be 3.5 ± 0.2 eV, while the analysis yielded an upper bound of 2.4 eV for the counterpart at the interface (thiol). The former is consistent with the theoretical value of ~3.5-5.0 eV. The measured I-V curves show scaling with respect to the printed Au electrode area with lateral dimensions ranging from 80 nm to 7 μm. These results demonstrate that PFPE-assisted nTP is a promising technique for producing potentially scalable and permanent MMM junctions. They also demonstrate that MMM structures (produced by the unique PFPE-assisted nTP) constitute a reliable test bed for exploring molecule-based electronics.

Nanotransfer Printing with sub‐10 nm Resolution Realized using Directed Self‐Assembly

An extraordinarily facile sub-10 nm fabrication method using the synergic combination of nanotransfer printing and the directed self-assembly of block copolymers is introduced. The approach is realized by achieving the uniform self-assembly of polydimethylsiloxane (PDMS)-containing block copolymers on a PDMS mold through the stabilization of the block copolymer thin films. This simple printing method can be applied on oxides, metals, polymers, and non-planar substrates without pretreatments. The fabrication of well-aligned metallic and polymeric functional nanostructures and crossed wire structures is also presented.

A technique for transferring metal nano patterns from a plastic replica mold by using a metal oxide release layer

Techniques for nano-scale metal patterning on plastic substrates are strongly desired for fabricating various novel devices such as printed electronics (PE), as well as plasmon photonics and optical devices. There are great hopes that PE devices on plastic substrates could replace conventional integrated circuits on silicon, because plastic substrates offer good transparency, flexibility, lightness and low cost. In order to simultaneously achieve high-resolution and high-throughput metal patterning on a plastic substrate, nano transfer printing (nTP) is a promising technique. However, conventional nTP processes require a poly(dimethylsiloxane) (PDMS) stamp. PDMS is a high-viscosity material before curing and thermosetting elastomer, so it is difficult to obtain PDMS stamps quickly by using injection molding or roll-to-roll nanoimprinting. To resolve these issues, we have developed a three-dimensional metal-pattern nanoimprinting technique that uses a metal oxide release layer. In this study, we examined a technique for transferring a metal onto poly(ethylene terephthalate) (PET) substrate using a cycloolefin polymer (COP) replica mold with a metal oxide release layer. We showed that the metal oxide release layer allows the nTP process to be implemented with a COP replica mold.

Transfer Printing of Nanoplasmonic Devices onto Flexible Polymer Substrates from a Rigid Stamp

Plasmonic color filters and polarizers were produced using nanotransfer printing to create aluminium nanostructures, as small as 75nm, on a polycarbonate sheet measuring 10mm × 12mm. Plasmonic filters showed good agreement with simulations.

High-Yield Transfer Printing of Metal–Insulator–Metal Nanodiodes

Nanoscale metal-insulator-metal (MIM) diodes represent important devices in the fields of electronic circuits, detectors, communication, and energy, as their cutoff frequencies may extend into the "gap" between the electronic microwave range and the optical long-wave infrared regime. In this paper, we present a nanotransfer printing method, which allows the efficient and simultaneous fabrication of large-scale arrays of MIM nanodiode stacks, thus offering the possibility of low-cost mass production. In previous work, we have demonstrated the successful transfer and electrical characterization of macroscopic structures. Here, we demonstrate for the first time the fabrication of several millions of nanoscale diodes with a single transfer-printing step using a temperature-enhanced process. The electrical characterization of individual MIM nanodiodes was performed using a conductive atomic force microscope (AFM) setup. Our analysis shows that the tunneling current is the dominant conduction mechanism, and the electrical measurement data agree well with experimental data on previously fabricated microscale diodes and numerical simulations.