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Heat-Assisted Photoacidic Oxidation Method for Tailoring the Surface Chemistry of Polymer Dielectrics for Low-Power Organic Soft Electronics
摘要： The use in low-power soft electronics of the appropriate insulating polymer materials with a high dielectric constant (k) is considered a practical alternative to that of inorganic dielectric materials, which are brittle and have high processing temperatures. However, the polar surfaces of typical high-k polymer insulators are problematic. Further, it is a huge challenge to control their surface properties without damage because of their soft and chemically fragile nature. Here, a heat-assisted photoacidic oxidation method that can be used to effectively oxidize the outermost surfaces of high-k rubbery polymer films without degradation is presented. The oxidized surfaces prepared with the developed method contain large numbers of hydroxyl groups that enable the subsequent growth of dense and ordered self-assembled monolayers (SAMs) consisting of organosilanes. The whole process modifies the surface characteristics of polymer dielectrics effectively. The mechanisms of the oxidation of polymer surfaces and the subsequent SAM growth process are investigated. The resulting surface-tailored rubbery dielectrics exhibit superior electrical characteristics when used in organic transistors. These results demonstrate that this method can be used to realize practical soft organic electronics based on high-k polymer dielectrics.
关键词： self-assembled monolayers,organic semiconductors,polymer gate dielectric,polymer oxidation,surface chemistry
更新于2025-09-23 15:23:52
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Threshold Voltage Control in Organic Field-Effect Transistors by Surface Doping with a Fluorinated Alkylsilane
摘要： Doping is a powerful tool to control the majority charge carrier density in organic field-effect transistors and the threshold voltage of these devices. Here, a surface doping approach is shown, where the dopant is deposited on the prefabricated polycrystalline semiconducting layer. In this study, (tridecafluoro-1,1,2,2-tetrahydrooctyl)-trichlorosilane (FTCS), a fluorinated alkylsilane is used as a dopant, which is solution processable and much cheaper than conventional p-type dopants, such as 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ). In this work, the depositions from the gas phase and from solution are compared. Both deposition approaches led to an increased conductivity and to a shift in the threshold voltage to more positive values, both of which indicate a p-type doping effect. The magnitude of the threshold voltage shift could be controlled by the FTCS deposition time (from vapor) or FTCS concentration (from solution); for short deposition times and low concentrations, the off current stayed constant and the mobility decreased only slightly. In the low doping concentration regime, both approaches resulted in similar transistor characteristics, i.e., similar values of shift in the threshold and turn-on voltage as well as mobility, ION/IOFF ratio and amount of introduced free charge carriers. In comparison with vapor deposition, the solution-based approach can be conducted with less material and in a shorter time, which is critical for industrial applications.
关键词： self-assembled monolayers,fluorinated alkylsilanes,organic field-effect transistors,surface doping,p-type doping
更新于2025-09-23 15:23:52
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Systematic Modulation of Charge Transport in Molecular Device through Facile Control of Molecule-Electrode Coupling using Double Self-assembled Monolayers Nanowire Junction
摘要： We report a novel solid-state molecular device structure based on double self-assembled monolayers (D-SAMs) incorporated into the suspended nanowire architecture to form “Au | SAM-1 || SAM-2 | Au” junction. Using commercially available thiol molecules that are devoid of synthetical difficulty, we constructed Au | S-(CH2)6-Ferrocene || SAM-2 | Au junction, with various length and chemical structure of SAM-2 to tune the coupling between ferrocene conductive molecular orbital and electrode of the junction. Combining low noise and wide temperature range measurement, we demonstrated systematically modulated conduction depending on the length and chemical nature of SAM-2. Meanwhile, transport mechanism transition from tunneling to hopping, and the intermediate state accompanied by the current fluctuation due to the coexistence of the hopping and tunneling transport channels, were observed. Considering the versatility of this solid-state D-SAMs in modulating the electrode-molecule interface and electroactive groups, this strategy thus provides a novel facile strategy for tailorable nanoscale charge transport study and functional molecular devices.
关键词： charge transport,molecular device,nanowire junction,self-assembled monolayers,ferrocene
更新于2025-09-23 15:21:01
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Low temperature platinum chemical vapor deposition on functionalized self-assembled monolayers
摘要： The reaction pathways of Pt CVD using (COD)PtMe2 – xClx (x = 0, 1, 2) have been investigated on functionalized self-assembled monolayers (SAMs) as models for organic substrates. Residual gas analysis for (COD)PtMe2 and (COD)PtMeCl is consistent with the loss of methyl radicals as the initial step in deposition, while for (COD)PtCl2, the first step is the loss of a chlorine radical. It is further shown using x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry that the deposition process leads to chemical damage of the SAM layer and little Pt deposition. Using this understanding, it is demonstrated that the Pt CVD rate can be controlled using a radical trap. In the presence of 1,4-cyclohexadiene, a well-known alkyl radical trap, Pt deposition was increased by 5× to 10×, creating a room-temperature effective Pt CVD process.
关键词： time-of-flight secondary ion mass spectrometry,x-ray photoelectron spectroscopy,Pt CVD,chemical vapor deposition,self-assembled monolayers,radical trap
更新于2025-09-23 15:21:01
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Gallium arsenide waveguides as a platform for direct mid-infrared vibrational spectroscopy
摘要： During recent years, mid-infrared (MIR) spectroscopy has matured into a versatile and powerful sensing tool for a wide variety of analytical sensing tasks. Attenuated total reflection (ATR) techniques have gained increased interest due to their potential to perform non-destructive sensing tasks close to real time. In ATR, the essential component is the sampling interface, i.e., the ATR waveguide and its material properties interfacing the sample with the evanescent field ensuring efficient photon-molecule interaction. Gallium arsenide (GaAs) is a versatile alternative material vs. commonly used ATR waveguide materials including but not limited to silicon, zinc selenide, and diamond. GaAs-based internal reflection elements (IREs) are a new generation of semiconductor-based waveguides and are herein used for the first time in direct spectroscopic applications combined with conventional Fourier transform infrared (FT-IR) spectroscopy. Next to the characterization of the ATR waveguide, exemplary surface reactions were monitored, and trace-level analyte detection via signal amplification taking advantage of surface-enhanced infrared absorption (SEIRA) effects was demonstrated. As an example of real-world relevance, the mycotoxin aflatoxin B1 (AFB1) was used as a model analyte in food and feed safety analysis.
关键词： Mid-infrared chem/biosensor,Surface modification,Gallium arsenide,Self-assembled monolayers,Evanescent field absorption,Surface-enhanced infrared absorption
更新于2025-09-23 15:21:01
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Direct Patterning of Piezoelectric Thin Films by Inkjet Printing
摘要： Inkjet printing is currently gaining momentum as a low-cost and eco-friendly additive manufacturing technique for electronics. Patterning of functional metal oxide thin films on high surface energy substrates via inkjet printing remains a challenge and requires assistance from lithographic processes. This work unveils a novel process for lithography and etching-free patterning of lead zirconate titanate (PZT) films on pristine platinized silicon through the use of inkjet-printed alkanethiolate-based templates. The technique requires neither lithography nor etching, respectively, before and after PZT printing. The described process allows for feature sizes in the sub-100 μm range with control over the thickness of the final film. Inkjet-printed PZT displays typical ferroelectric and piezoelectric properties of solution-derived thin films, with remnant polarization 13 μC cm?2, coercive field 58 kV cm?1, permittivity 900, dielectric losses 0.07, and effective longitudinal piezoelectric coefficient 50 pm V?1.
关键词： piezoelectrics,lead zirconate titanate,inkjet printing,patterning,self-assembled monolayers
更新于2025-09-23 15:21:01
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Controlled Electroless Deposition of Noble Metals on Silicon Substrates Using Self-Assembled Monolayers as Molecular Resists to Generate Nanopatterned Surfaces for Electronics and Plasmonics
摘要： Electroless deposition of noble metals on silicon has applications in a wide range of fields including electronic circuitry, metal plating industry, lithography, and other fabrication techniques. In addition, studies using self-assembled monolayers (SAM) as resists for electroless deposition for controlled deposition have significant potential for aiding advancement in the fields of nano electronics, sensing applications, and fundamental studies. Herein, we discuss the development of appropriate plating solutions for controlled deposition of metallic gold and silver on Si(111) surfaces in the presence of an organic silane monolayer acting as a resist film for directed metal deposition to produce metal-monolayer hybrid surfaces while investigating microscopic plating trends. For this, plating solutions were optimized to deposit metal on bare silicon surfaces while avoiding deposition on the SAM protected areas. Trends in the electroless deposition of gold and silver on a Si(111) surface as a function of concentration of metal ions, NH4F, citric acid, sodium citrate, polyvinylpyrrolidone (PVP) and deposition time have been monitored under ambient conditions. The resulting surfaces were characterized using atomic force microscopy (AFM) and the stability of plating solutions was investigated by UV-Vis spectroscopy. For both gold and silver, we observed an increase in metal deposition when the concentration of NH4F, citric acid, and deposition time increased. The addition of PVP and the pH of the solution were also shown to have a significant effect on the metal deposition. The octadecyltrichlorosilane (OTS) SAM films act as effective nanoscale resists when the NH4F concentration is reduced from typical plating conditions. In particular, NH4F concentrations from 0.02-0.50 M and metal ions concentrations from 0.001-0.020 M were found to allow deposition of metal nanostructures on a bare Si surface while preserving OTS protected areas.
关键词： self-assembled monolayers,AFM,silver,controlled metal deposition,gold,Electroless deposition
更新于2025-09-23 15:19:57
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Significant Performance Improvement of Oxide Thin-Film Transistors by a Self-Assembled Monolayer Treatment
摘要： Despite being a standard process in fabrication of organic thin-film transistors (TFTs) to reduce interface trap density and decrease surface energy, self-assembled monolayer (SAM) treatment of gate dielectrics is rarely used in oxide-semiconductor-based TFTs due to possible damage to the SAM during semiconductor deposition. Here, by studying the dependence of plasma damage to SAM on the deposition conditions of InGaZnO (IGZO) semiconductor thin films, the feasibility of enhancing the performance of oxide TFTs using octadecyl-trichlorosilane (OTS)-treated, ultra-thin AlxOy gate dielectrics is explored. It is discovered that under optimized conditions, the TFTs can be significantly improved, showing a reduction of interface trap density by 50% and an increase of carrier mobility and current on/off ratio by a factor of 2.3 and 76, respectively. The effects on bias stress stability also show substantial improvement after the SAM interface treatment. Finally, such an optimized condition is found to also work for IGZO TFTs gated with OTS-treated HfOx, showing an increase of mobility from 7.8 to 16 cm2 V?1 s?1 compared with the untreated devices. As a result, this simple and yet effective interface treatment method and the resulting devices may have potential applications in future low-cost, low-power electronics.
关键词： interface treatment,octadecyltrichlorosilane,self-assembled monolayers,thin-film transistors,oxide semiconductors
更新于2025-09-23 15:19:57
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Interfacial Band Engineering of MoS <sub/>2</sub> /Gold Interfaces Using Pyrimidine-Containing Self-Assembled Monolayers: Toward Contact-Resistance-Free Bottom-Contacts
摘要： 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.
关键词： work-function engineering,MoS2,thin-film transistors,self-assembled monolayers,Schottky barrier
更新于2025-09-23 15:19:57
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Structure and Conformation of a Crystalline P3HT Film Adsorbed on an Alkanethiol Self-Assembled Monolayer Deposited on Gold
摘要： All-atom molecular dynamics simulations are performed to investigate the structural and conformational properties of a regioregular poly(3-hexylthiophene) (P3HT) crystal in the presence of a gold (Au) substrate terminated with an n-alkanethiol self-assembled monolayer (SAM). The employed orientation of the P3HT crystals deposited on the SAM is the edge-on, since this orientation is believed to be the most energetically favorable and stable, also yielding the highest charge carrier mobility in organic thin-film transistors. The unit cell of the overall Au/SAM interfacial layer is obtained through detailed ab initio calculations. Systems with a varying number of P3HT stacks on the Au/SAM substrate are studied with an all-atom force field in order to elucidate the effect of polymer thickness on the structural properties of the system. All final structures are found to be stable and well-equilibrated. Insights into the P3HT crystal structure are provided for the P3HT layers in direct contact with the SAM, but also for those deeper in the polymer film. According to the simulations, the majority of conformational and packing properties of the P3HT film are practically similar to those of the bulk crystalline P3HT material, implying that its structure remains unaffected by the presence of the underlying Au/SAM substrate.
关键词： DFT calculations,semiconducting polymers,molecular dynamics simulations,self-assembled monolayers,P3HT
更新于2025-09-23 15:19:57