共查询到20条相似文献，搜索用时 15 毫秒
1.
Tarek Abu‐Husein Swen Schuster Martin Kind Tobias Santowski Adrian Wiesner Ryan Chiechi Egbert Zojer Andreas Terfort Michael Zharnikov 《Advanced functional materials》2015,25(25):3943-3957
Using a representative model system, here electronic and structural properties of aromatic self‐assembled monolayers (SAMs) are described that contain an embedded, dipolar group. As polar unit, pyrimidine is used, with its orientation in the molecular backbone and, consequently, the direction of the embedded dipole moment being varied. The electronic and structural properties of these embedded‐dipole SAMs are thoroughly analyzed using a number of complementary characterization techniques combined with quantum‐mechanical modeling. It is shown that such mid‐chain‐substituted monolayers are highly interesting from both fundamental and application viewpoints, as the dipolar groups are found to induce a potential discontinuity inside the monolayer, electrostatically shifting the core‐level energies in the regions above and below the dipoles relative to one another. These SAMs also allow for tuning the substrate work function in a controlled manner independent of the docking chemistry and, most importantly, without modifying the SAM‐ambient interface. 相似文献
2.
Daniela Meroni Silvia Ardizzone Ulrich S. Schubert Stephanie Hoeppener 《Advanced functional materials》2012,22(20):4376-4382
Transparent conductive oxides like indium tin oxide (ITO) play a pivotal role in a wide range of innovative applications, such as new generations of solar cells. In many of these applications the tailoring of surface properties on the nanometer scale represents a highly desirable target. The local oxidation of self‐assembled monolayers (SAMs) using a scanning probe is a promising technique to achieve surface modifications on the nanometer scale. So far, electro‐oxidative lithography of SAMs has been reported mainly on Si wafers while there are no previous reports on transparent oxides. Here, we report the oxidative lithography of n‐octadecyltrichlorosilane (OTS) SAM deposited onto an ITO layer. A local overoxidation of the substrate is observed while the simultaneously occurring monolayer oxidation is indirectly confirmed by the site‐selective deposition of silver nanoparticles onto electro‐oxidized areas. The process of lithography is compared to that on OTS‐Si substrates and its mechanism is systematically investigated by means of scanning Kelvin probe microscopy (SKPM). 相似文献
3.
Aleksandar Matkovi&#x; Andreas Petritz Gerburg Schider Markus Krammer Markus Kratzer Esther Karner‐Petritz Alexander Fian Herbert Gold Michael Grtner Andreas Terfort Christian Teichert Egbert Zojer Karin Zojer Barbara Stadlober 《Advanced Electronic Materials》2020,6(5)
Bottom‐contact architectures with common electrode materials such as gold are crucial for the integration of 2D semiconductors into existing device concepts. The high contact resistance to gold—especially for bottom contacts—is, however, a general problem in 2D semiconductor thin‐film transistors. Pyrimidine‐containing self‐assembled monolayers on gold electrodes are investigated for tuning the electrode work functions in order to minimize that contact resistance. Their frequently ignored asymmetric and bias‐dependent nature is recorded by Kelvin probe force microscopy through a direct mapping of the potential drop across the channel during device operation. A reduction of the contact resistances exceeding two orders of magnitude is achieved via a suitable self‐assembled monolayer, which vastly improves the overall device performance. 相似文献
4.
Alberto Ghirri Valdis Corradini Christian Cervetti Andrea Candini Umberto del Pennino Grigore Timco Robin J. Pritchard Christopher A. Muryn Richard E. P. Winpenny Marco Affronte 《Advanced functional materials》2010,20(10):1552-1560
Graphite is a clean substrate and its nanostructures hold great potential for applications. Anchoring large molecules on graphite represents a challenge for several reasons that essentially rise from the planar bonds of the packed honeycomb structure of carbon. Here, a systematic investigation by AFM and XPS on different derivatives of molecular Cr7Ni rings deposited on highly oriented pyrolytic graphite (HOPG) is reported. Cr7Ni is emerging as a prototipical example of molecular antiferromagnet on which quantum phenomena and coherence have been demonstrated. For the deposition of Cr7Ni on HOPG, two strategies are adopted: 1) Cr7Ni rings are functionalized with extended alkyl/benzene terminations and 2) a self‐assembled monolayer of alkyl chains with sulfonate terminations is deposited and then a cationic Cr7Ni derivative is used. In both cases the electronic bond with the carbon surface is soft, but the two‐step procedure is efficient, albeit indirect, in sticking molecular Cr7Ni on HOPG. These strategies can be easily extended to deposit other complex molecular aggregates on graphite from the liquid phase. 相似文献
5.
6.
Milan Alt Malte Jesper Sabina Hillebrandt Patrick Reiser Tobias Rödlmeier Iva Angelova Kaja Deing Eric Mankel Wolfram Jaegermann Annemarie Pucci Uli Lemmer U. H. F. Bunz W. Kowalsky G. Hernandez‐Sosa R. Lovrincic M. Hamburger 《Advanced functional materials》2016,26(18):3172-3178
A novel Self‐assembled Monolayer (SAM) forming molecule bisjulolidyldisulfide (9,9'‐disulfanediylbis(2,3,6,7‐tetrahydro‐1H,5H‐pyrido[3,2,1‐ij]quinoline)) is demonstrated which lowers the work function of metal surfaces by ≈1.2 eV and can be deposited in a 1 min process. Bisjulolidyldisulfide exists in a stable disulfide configuration prior to surface exposure and can therefore be stored, handled, and processed in ambient conditions. SAM from bisjulolidyldisulfide are deposited on metal surfaces (Au and Ag), including inkjet printed Ag on polyethylene terephthalate substrates, investigated by photoelectron and infrared spectroscopy, and used as electrodes in n‐type organic field effect transistor (OFET). Treatment of electrodes in OFET devices with with bisjulolidyldisulfide‐SAMs reduces the contact resistance by two orders of magnitude and improves shelf life with respect to pristine metal electrodes. The presented treatment also increases the surfaces wettability and thereby facilitates solution processing of a subsequent layer. These beneficial properties for device performance, processing, and stability, combined with ease of preparation and handling, render this SAM‐forming molecule an excellent candidate for the high‐throughput production of flexible electronic devices. 相似文献
7.
Yang Li Cheng‐Yan Xu Jing‐Kai Qin Wei Feng Jia‐Ying Wang Siqi Zhang Lai‐Peng Ma Jian Cao Ping An Hu Wencai Ren Liang Zhen 《Advanced functional materials》2016,26(2):293-302
The behavior of excitons in van der Waals (vdWs) heterostructures depends on electron–electron interactions and charge transfer at the hetero‐interface. However, what still remains to be unraveled is to which extent the carrier densities of both counterparts and the band alignment in the vdWs heterostructures determine the photoluminescence properties. Here, we systematically study the photoluminescence properties of monolayer MoS2/graphene heterostructures by modulating the carrier densities and contact barrier at the interface via electrochemical gating. It is shown that the PL intensities of excitons can be tuned by more than two orders of magnitude, and a blue‐shift of the exciton peak of up to 40 meV is observed. By extracting the carrier density of MoS2 using an electric potential distribution model, and the Schottky barrier using first‐principle calculations, we find that the controllable carrier density in MoS2 plays a dominant role in the PL tuning at negative gate bias, whereas the interlayer relaxation of excitons induced by the Schottky barrier has a major contribution at positive gate bias. This is further verified by controlling the tunneling barrier and screening field across MoS2 by inserting self‐assembled monolayers (SAMs) at the interface. These findings will benefit to better understand the effect of many‐body interactions and hetero‐interfaces on the optical and optoelectronic properties in vdWs heterostructures. 相似文献
8.
Xiaoyang Cheng Yong‐Young Noh Jianpu Wang Marta Tello Johannes Frisch Ralf‐Peter Blum Antje Vollmer Jürgen P. Rabe Norbert Koch Henning Sirringhaus 《Advanced functional materials》2009,19(15):2407-2415
Controlling contact resistance in organic field‐effect transistors (OFETs) is one of the major hurdles to achieve transistor scaling and dimensional reduction. In particular in the context of ambipolar and/or light‐emitting OFETs it is a difficult challenge to obtain efficient injection of both electrons and holes from one injecting electrode such as gold since organic semiconductors have intrinsically large band gaps resulting in significant injection barrier heights for at least one type of carrier. Here, systematic control of electron and hole contact resistance in poly(9,9‐di‐n‐octylfluorene‐alt‐benzothiadiazole) ambipolar OFETs using thiol‐based self‐assembled monolayers (SAMs) is demonstrated. In contrast to common believe, it is found that for a certain SAM the injection of both electrons and holes can be improved. This simultaneous enhancement of electron and hole injection cannot be explained by SAM‐induced work‐function modifications because the surface dipole induced by the SAM on the metal surface lowers the injection barrier only for one type of carrier, but increases it for the other. These investigations reveal that other key factors also affect contact resistance, including i) interfacial tunneling through the SAM, ii) SAM‐induced modifications of interface morphology, and iii) the interface electronic structure. Of particular importance for top‐gate OFET geometry is iv) the active polymer layer thickness that dominates the electrode/polymer contact resistance. Therefore, a consistent explanation of how SAM electrode modification is able to improve both electron and hole injection in ambipolar OFETs requires considering all mentioned factors. 相似文献
9.
Electropolymerized Self‐Assembled Monolayers of a 3,4‐Ethylenedioxythiophene‐Thiophene Hybrid System
Maiténa Oçafrain Truong Khoa Tran Philippe Blanchard Stéphane Lenfant Sylvie Godey Dominique Vuillaume Jean Roncali 《Advanced functional materials》2008,18(15):2163-2171
Self‐assembled monolayers (SAMs) of a conjugated bithiophenic system connected to an alkanethiol chain have been deposited on gold surface. The electroactive bithiophenic system involves a 3,4‐ethylenedioxythiophene (EDOT) unit and a thiophene ring on which an alkanethiol is attached at the internal β‐position via a sulfide linkage. The analysis of the structure of the SAMs by IR spectroscopy, ellipsometry, contact angle measurement and X‐ray photoelectron spectroscopy (XPS) provides consistent results indicating compact monolayers in which the alkyl linkers are arranged in an almost vertical fashion while the bithiophenic‐conjugated systems are essentially parallel to the surface. Cyclic voltammetry shows that application of a few potential scans to SAMs immersed in a medium containing only a supporting electrolyte leads to the typical electropolymerization curves while the CV of the electrooxized monolayer exhibits a reversible cyclic voltammogram characteristic of a stable electroactive extended conjugated system. The characterization of the electropolymerized monolayers by IR spectroscopy, ellipsometry, contact angle measurement, and XPS indicates compact monolayers. The analysis of the current voltage characteristics of the monolayers by conducting AFM before and after electrooxidation shows that the enhancement of the effective conjugation resulting from electropolymerization leads to a significant increase of the transport properties. 相似文献
10.
Mark Elbing Alfred Błaszczyk Carsten von Hänisch Marcel Mayor Violetta Ferri Christian Grave Maria Anita Rampi Giuseppina Pace Paolo Samorì Andrei Shaporenko Michael Zharnikov 《Advanced functional materials》2008,18(19):2972-2983
Aiming at modulating the packing density within functional self‐assembled monolayers (SAMs), two azo‐biphenyl derivatives AZO1 and AZO2 comprising a terminal sulfur anchor group have been designed and synthesized. While AZO1 allows for a coplanar arrangement of both biphenyl subunits, additional steric repulsion due to two methyl side groups attached to the footing biphenyl of AZO2 results in an increased intermolecular distance within the SAM, providing additional free volume. SAMs of both derivatives on gold and platinum substrates have been formed and thoroughly investigated by photoelectron (XPS) and near‐edge absorption fine structure (NEXAFS) spectroscopy as well as cyclic voltammetry and scanning tunneling microscopy. These measurements confirmed the formation of tightly packed SAMs for AZO1 , while AZO2 formed SAMs consisting of less organized and more loosely packed molecules. Optical investigations of both azo derivatives in solution as well as their SAMs displayed efficient photoisomerization in solution and in SAMs. Comparable maximal cis/trans ratios of ca. 0.9 have been observed in all cases upon irradiation at λ = 370 and 360 nm for AZO1 and AZO2 , respectively. The thermally induced cis → trans back reaction on AZO1 was found to be slower by a factor of 3 in SAMs as compared to solution, while AZO2 displayed comparable rates of the back reaction in both environments. This behavior can be explained by the different nature of molecular isomerization in the two SAM systems: whereas the isomerization in AZO1 SAMs takes place in a highly coordinated, collective way and involves many adjacent molecules, AZO2 species behave rather individually even packed in SAMs, such that their isomerization process is similar in SAMs and in solutions. 相似文献
11.
Arantxa Maestre Caro Silvia Armini Olivier Richard Guido Maes Gustaaf Borghs Caroline M. Whelan Youssef Travaly 《Advanced functional materials》2010,20(7):1125-1131
A 3‐aminopropyltrimethoxysilane‐derived self‐assembled monolayer (NH2SAM) is investigated as a barrier against copper diffusion for application in back‐end‐of‐line (BEOL) technology. The essential characteristics studied include thermal stability to BEOL processing, inhibition of copper diffusion, and adhesion to both the underlying SiO2 dielectric substrate and the Cu over‐layer. Time‐of‐flight secondary ion mass spectrometry and X‐ray spectroscopy (XPS) analysis reveal that the copper over‐layer closes at 1–2‐nm thickness, comparable with the 1.3‐nm closure of state‐of‐the‐art Ta/TaN Cu diffusion barriers. That the NH2SAM remains intact upon Cu deposition and subsequent annealing is unambiguously revealed by energy‐filtered transmission electron microscopy supported by XPS. The SAM forms a well‐defined carbon‐rich interface with the Cu over‐layer and electron energy loss spectroscopy shows no evidence of Cu penetration into the SAM. Interestingly, the adhesion of the Cu/NH2SAM/SiO2 system increases with annealing temperature up to 7.2 J m?2 at 400 °C, comparable to Ta/TaN (7.5 J m?2 at room temperature). The corresponding fracture analysis shows that when failure does occur it is located at the Cu/SAM interface. Overall, these results demonstrate that NH2SAM is a suitable candidate for subnanometer‐scale diffusion barrier application in a selective coating for copper advanced interconnects. 相似文献
12.
13.
The development of new surface coatings is critical for combating wear and increasing the device lifetime in microelectromechanical systems (MEMS). Here, a class of arsonic acid self‐assembled monolayers (SAMs) is reported that form readily on oxide substrates including silicon oxide, borosilicate glass, and titanium oxide. Monolayers are easily prepared using a straightforward soaking technique, which is amenable to large‐scale commercial applications. Monolayer formation on borosilicate glass and titanium oxide is characterized using infrared spectroscopy. Monolayers on borosilicate glass, native silicon oxide and titanium oxide are evaluated with contact angle measurements, as well as wear measurements using nanoscratching experiments. On titanium oxide and borosilicate glass, monolayers prepared from hexadecylarsonic acid provide significantly greater surface protection than surfaces reacted under similar conditions with hexadecylphosphonic acid, a common modifying agent for oxide substrates. 相似文献
14.
Sven O. Krabbenborg Janine G. E. Wilbers Jurriaan Huskens Wilfred G. van der Wiel 《Advanced functional materials》2013,23(6):770-776
A method is described for fabricating and electrically characterizing large‐area (100–400 μm2) metal‐molecular monolayer‐metal junctions with a relatively high overall yield of ≈45%. The measurement geometry consists of ultra‐smooth (template‐stripped) patterned Au bottom electrodes, combined with ultra‐smooth top Au electrodes deposited using wedging transfer. The fabrication method is applied to the electrical characterization of Au‐alkanethiol self‐assembled monolayer‐Au junctions. An exponential decay of the current density is found for increasing the chain length of the alkanethiols, in agreement with earlier studies. The symmetric device geometry, and flexibility for contacting monolayers with various end groups are important advantages compared to existing techniques for electrically characterizing molecular monolayers. 相似文献
15.
Dongku Kim Hyunhak Jeong Wang‐Taek Hwang Yeonsik Jang Dmytro Sysoiev Elke Scheer Thomas Huhn Misook Min Hyoyoung Lee Takhee Lee 《Advanced functional materials》2015,25(37):5918-5923
Photoswitching molecular electronic devices with reduced graphene oxide (rGO) top electrodes on flexible substrates are fabricated and characterized. It has been reported previously that diarylethene molecular devices with poly‐(3,4‐ethylenedioxythiophene) stabilized with poly‐(4‐styrenesulfonic acid)/Au top electrodes can hold two stable electrical conductance states when the devices are exposed to UV or visible light during device fabrication. However, those devices fail to show the reversible switching phenomenon in response to illumination after device fabrication. By employing conducting and transparent rGO top electrodes, it is demonstrated that the diarylethene molecular devices show a reversible switching phenomenon, i.e., the fabricated devices change their conductance state in response to the alternating illumination with UV and visible light. Furthermore, the molecular devices with rGO top electrodes also exhibit good longtime stability and reliable electrical characteristics when subjected to various mechanical stresses (bending radius down to 5 mm and bending cycle over 104). 相似文献
16.
A novel, simple, versatile, rapid, and inexpensive method, “space limited oxygen plasma oxidation” is developed to fabricate chemical gradient on both alkylsilane and alkanethiol self‐assembled monolayers (SAMs) surface. XPS data confirm that the methyl groups of alkane SAMs are converted into oxidized carbon functional groups. The influences of RF power, O2 flow rate, and the “wedge” shape on gradient formation are investigated in details. Gradient surfaces with various scales and depths are formed by simply changing the ‘wedge’ shape or plasma generation parameters. The application of formed chemical gradient on droplet motion has been demonstrated as well. 相似文献
17.
Nicole Herzer Jurriaan H. K. van Schaik Stephanie Hoeppener Ulrich S. Schubert 《Advanced functional materials》2010,20(19):3252-3259
The electrochemical oxidation process of self‐assembled monolayers formed by n‐octadecyltrichlorosilane (OTS) molecules on silicon wafers has been studied in a droplet of water by means of in situ water contact angle measurements. The application of different bias voltages between the substrate and a counter electrode placed into the droplet resulted in changes of the chemical nature of the monolayer, which yielded a significant alteration of the surfaces properties. Due to the changes of the wetting properties of the monolayer during the electro‐oxidation process a change in the contact angles of the water droplet is concomitantly observed. This allows the in situ monitoring of the electro‐oxidation process for large modified areas of several millimeters in diameter. The chosen approach represents an easy way to screen the major parameters that influence the oxidation process. Afterwards, the oxidized regions are characterized by Fourier‐transform infrared (FT‐IR) spectroscopy, X‐ray photoelectron spectroscopy (XPS) measurements, and atomic force microscopy (AFM) investigations to obtain more information about the electro‐oxidation process. The observations are correlated to experimental results obtained for oxidations performed on a smaller dimension range in the water meniscus of a conductive, biased AFM tip. A good correlation of the results in the different dimension ranges could be found. 相似文献
18.
Naoto Shirahata Jun Nakanishi Yoshitaka Echikawa Atsushi Hozumi Yoshitake Masuda Shigeru Ito Yoshio Sakka 《Advanced functional materials》2008,18(19):3049-3055
A novel method to produce a multifunctional microarray in which different types of self‐assembled monolayers (SAMs) are positioned on predefined surface sites on an oxide‐covered silicon substrate is described. To achieve this, a liquid‐transportation system called “liquid manipulation lithography” (LML) is developed. This system allows the delivery of different varieties of molecular inks, trialkoxysilanes, onto each predefined surface position of the given substrate even under ambient conditions. Under optimum conditions, the transferred trialkoxysilane inks first form one‐molecule‐thick microstructures at each surface position through the hydrolysis of the reactive silanes with surface water adsorbed on the substrate, followed by a condensation reaction. Three types of trialkoxysilanes with long alkyl‐chains, specifically triethoxysilylundecanal (TESUD), N‐(6‐aminohexyl)‐3‐aminopropyltrimethoxysilane (AHAPS), and octadecyltrimethoxysilane (OTS), are used as model molecular inks due to their high‐end group‐functionalities in biological and electronic applications. The precise positioning of the ink with sub‐micrometer edge resolution is performed by carefully controlling a femtoliter‐scale liquid‐injection micromanipulator under a microscope. To ensure that the prepared SAM microarray is available for parallel analysis of biomolecular interactions, the area‐selective immobilization of a protein molecule is explored. Successful observation of the area‐selective biomolecular attachment confirmed a high industrial potential for the method as a lithography‐free process for the miniaturization of a multifunctional SAM array on an oxide substrate. 相似文献
19.
Chi Yueh Kao Bumsu Lee Leszek S. Wielunski Martin Heeney Iain McCulloch Eric Garfunkel Leonard C. Feldman Vitaly Podzorov 《Advanced functional materials》2009,19(12):1906-1911
A strong modification of the electronic properties of solution‐processable conjugated polythiophenes by self‐assembled silane molecules is reported. Upon bulk doping with hydrolized fluoroalkyl trichlorosilane, the electrical conductivity of ultrathin polythiophene films increases by up to six orders of magnitude, reaching record values for polythiophenes: (1.1 ± 0.1) × 103 S cm?1 for poly(2,5‐bis(3‐tetradecylthiophen ‐2‐yl)thieno[3,2‐b]thiophene) (PBTTT) and 50 ± 20 S cm?1 for poly(3‐hexyl)thiophene (P3HT). Interband optical absorption of the polymers in the doped state is drastically reduced, making these highly conductive films transparent in the visible range. The dopants within the porous polymer matrix are partially crosslinked via a silane self‐polymerization mechanism that makes the samples very stable in vacuum and nonpolar environments. The mechanism of SAM‐induced conductivity is believed to be based on protonic doping by the free silanol groups available within the partially crosslinked SAM network incorporated in the polythiophene structure. The SAM‐doped polythiophenes exhibit an intrinsic sensing effect: a drastic and reversible change in conductivity in response to ambient polar molecules, which is believed to be due to the interaction of the silanol groups with polar analytes. The reported electronic effects point to a new attractive route for doping conjugated polymers with potential applications in transparent conductors and molecular sensors. 相似文献
20.
Ilja Lange Sina Reiter Michael Pätzel Anton Zykov Alexei Nefedov Jana Hildebrandt Stefan Hecht Stefan Kowarik Christof Wöll Georg Heimel Dieter Neher 《Advanced functional materials》2014,24(44):7014-7024
Zinc oxide (ZnO) is regarded as a promising alternative material for transparent conductive electrodes in optoelectronic devices. However, ZnO suffers from poor chemical stability. ZnO also has a moderate work function (WF), which results in substantial charge injection barriers into common (organic) semiconductors that constitute the active layer in a device. Controlling and tuning the ZnO WF is therefore necessary but challenging. Here, a variety of phosphonic acid based self‐assembled monolayers (SAMs) deposited on ZnO surfaces are investigated. It is demonstrated that they allow the tuning the WF over a wide range of more than 1.5 eV, thus enabling the use of ZnO as both the hole‐injecting and electron‐injecting contact. The modified ZnO surfaces are characterized using a number of complementary techniques, demonstrating that the preparation protocol yields dense, well‐defined molecular monolayers. 相似文献