Polyimide Layer Research Articles

Negative-tone Photo-definable Polyimide with High Thermal Stability and Thick Film Processability

High voltage power semiconductor requires higher polyimide insulation properties. We have designed a polyimide with high thermal stability, high light transparency and alkali dissolvable polyimide that is capable of passivating thick layer of polyimide with large topographys. A novel negavitve-tone photo-definable polyimide was formulated with cross linking reagent that can easily decompose during cure and a photo-initiator that initiates well during lithography. Our novel Negative photo sensitive polyimide, PSPI-1, has a patternable capability up to 16 mm thickness on silicon with 350 mj/cm2. PSPI-1 showed higher patternability than of the conventional polyimide. The cured film showed excellent properties as follows: 310C glass transition temperature (Tg), 500C 5% weight loss temperature, 40% elongation, no short observation during bias-HAST (130C. 96%, 100hr, 100V 15/30 mm line & space) and good adhesion to Si and Cu substrates. These results indicated a possibility for this novel PSPI-1 to be applicable for passivating power semiconductor.

Dual-band terahertz metamaterial sensor and its sensing capacity enhanced with a central-relief design.

In this paper, a dual-band terahertz metamaterial sensor based on aluminum and silicon is proposed and simulated. The aluminum surface, which is deposited on a silicon substrate, is made of a C-shaped frame resonator, a rectangular beam, and a cross. The device is insensitive to the change of incident angle in the range of 0°-30°, which shows the great transmission stability of the sensor. By examining the resonance frequency shift, it is shown that 98.3 and 237.5GHz/RIU refractive index sensitivity can be obtained near 1.76 and 2.404THz transmission dips of the proposed structure, respectively. The two dips can be used to sense analytes in different refractive index ranges, respectively. For Dip 1 at 1.76THz, the range is 1.0-1.6. For Dip 2 at 2.404THz, the range is 1.6-2.0. Different from traditional multi-band metamaterial sensors, two dips generated by the proposed device can measure continuous and non-multiplexed refractive index ranges, respectively. Because the resonance frequencies of matters are different, such a characteristic enables the device to measure different types of analyte using the appropriate resonant peak. A central-relief design is then proposed based on perturbation theory to further improve its sensing performance. The aluminum cross is covered by polyimide, which can interfere with the scattering field on the metal surface and affect the transmission results. For both transmission dips, the optimized structure realizes higher sensitivities of 111.7GHz/RIU and 262.5GHz/RIU, respectively. More significantly, the optimized structure also has the characteristic of a wide and non-multiplexed refractive index range. In addition, the effects of analyte thickness and polyimide layer thickness on sensor performance are also discussed. The proposed structure opens up new prospects in the design of multiple-band terahertz metamaterial sensors. It can also meet the sensing needs of biomedical, environmental monitoring, and industrial manufacturing.

The modified boundary layer mechanism for the release between polyimide film and poly(ether ketone ketone) thermoplastics

AbstractSticking between the thermoplastic polymer and metal tool is a crucial issue, as it determines whether the manufactured part can be ejected from the metal mold. Polyimide (PI) release films have been widely used in the processing of fiber‐reinforced thermoplastic polymer composites. Compared with other release mediums such as release agents, PI release film has a higher release efficiency. However, the underlying release mechanism is still not well understood which is essential to improve their performance further and reduce the cost. In this paper, poly(ether ketone ketone) (PEKK) polymer was melted and cooled down between two PI films. The surface morphologies and chemical compositions of the PI film and PEKK were characterized both before and after release using atomic force microscope, x‐ray photoelectron spectroscopy, contact angle measurements, and confocal microscopy. It showed that a thin PI layer was transferred from the PI release film to the PEKK surface during the release process. Based on these experimental results, a modified boundary layer mechanism is proposed as a hypothesis to describe the release mechanism of PI films. Our results give a fundamental understanding of how PI film works for the release of thermoplastics with high processing temperatures and may help to improve the performance and reduce the costs of existing PI films and may give guidance to the design of new release media.

Wearable microfluidic sweat collection platform with a calorimetric flow rate sensor for realtime and long-term sweat rate measurements

This work presents the design and fabrication of a wearable microfluidic patch-based system for sweat collection with a calorimetric flow rate sensor based on heat convection for measuring sweat rate (SR). The effects were predicted using a 3D multi-physics simulator and were verified on a fabricated patch made of polyimide layers. The sensor can detect surface temperature gradients of 302–312 K caused by fluid flowing thru the microfluidic channels at a rate of 0.5–23 µg s−1 that fall within the physiological range of SR. Meanwhile, the relation between flow rate and temperature gradient is highly linear (Pearson r2 = 0.999) and repeatable. This work also demonstrates a low-cost method for patterning microfluidic channels on flexible substrates which can be used for mass production of wearable patches.

Advanced Terahertz Refractive Sensing And Fingerprint Recognition Through Metasurface-Excited Surface Waves.

High-sensitive metasurface-based sensors are essential for effective substance detection and insightful bio-interaction studies, which compress light in subwavelength volumes to enhance light-matter interactions. However, current methods to improve sensing performance always focus on optimizing near-field response of individual meta-atom, and fingerprint recognition for bio-substances necessitates several pixelated metasurfaces to establish a quasi-continuous spectrum. Here, a novel sensing strategy is proposed to achieve Terahertz (THz) refractive sensing, and fingerprint recognition based on surface waves (SWs). Leveraging the long-range transmission, strong confinement, and interface sensitivity of SWs, a metasurface-supporting SWs excitation and propagation is experimentally verified to achieve sensing integrations. Through wide-band information collection of SWs, the proposed sensor not only facilitates refractive sensing up to 215.5°/RIU, but also enables the simultaneous resolution of multiple fingerprint information within a continuous spectrum. By covering 5µm thickness of polyimide, quartz and silicon nitride layers, the maximum phase change of 91.1°, 101.8°, and 126.4° is experimentally obtained within THz band, respectively. Thus, this strategy broadens the research scope of metasurface-excited SWs and introduces a novel paradigm for ultrasensitive sensing functions.

Construction of sandwich‐layered polyimide hybrid films containing double core–shell structured fillers for high energy storage density

AbstractThe inherent low dielectric constant of polyimide (PI) dielectrics restricts their applications to become a component of high energy density film capacitors. In this work, double core–shell structured barium titanate@magnesium oxide@polydopamine (BaTiO3@MgO@PDA) nanoparticles were synthesized successfully and utilized as high dielectric constant functional fillers for PIs, in which the insulating MgO layer meliorated dielectric constant difference between BaTiO3 and PI matrix, and the organic PDA layer improved the compatibility between the inorganic fillers and PI matrices. Then, a series of sandwich‐structured PI‐based hybrid films was prepared through a layer‐by‐layer solution casting method. The middle layer of pure PI with excellent insulating properties effectively suppressed charge injection. With the combination of sandwich structure and the BaTiO3@MgO@PDA nanoparticles, the PI hybrid film containing 15 wt% fillers in the outer layers achieved the maximum breakdown strength of 425.68 kV/mm and the maximum energy density of 5.132 J/cm3, which was 68.3% and 413% higher than those of pure PI film, respectively, meanwhile maintained a low dielectric loss value of 0.0083 at 1 kHz. The introduction of BaTiO3@MgO@PDA enhanced the interfacial polarization due to the high barrier energy between adjacent layers preventing the transfer of electrons and weakening the leakage current in the sandwich‐structured composite film. This work demonstrates that an appropriate combination of high dielectric hybrid fillers and multilayer structure can effectively increase the energy storage density of PI substrate for high‐temperature energy storage applications.Highlights The double core–shell structured BaTiO3@MgO@PDA was synthesized successfully. The sandwich‐structured hybrid films were prepared by layer‐by‐layer method. The energy density of hybrid films reached a high value of 5.132 J/cm3.

New approaches for creating effective combined printed circuit boards on thermally conductive substrates with polyimide dielectrics

New approaches to manufacturing improved combined boards on aluminum bases with various thin polyimide dielectrics, including thermally conductive ones, foiled by copper or aluminum foil have been proposed.
 Design and technological solutions and methods for manufacturing combined printed circuit boards on aluminum bases using industrial thin thermally conductive polyimide dielectric films with fluoropolymer coatings with thermal conductivity from 0,12 to 0,46 W/(m·K) have been developed. Design and technological solutions and methods for manufacturing combined printed circuit boards on thermally conductive aluminum bases using adhesive-free copper-polyimide and aluminum-polyimide lacquer foil dielectrics with thermal conductivity of varnish polyimide layers from 0,12 up to 1,0 W/(m·K) and more have been developed.
 Main chemical, mechanical, electrical end thermal properties of various types of experimental combined printed circuit boards on aluminum bases with thin polyimide dielectrics for use in electronic modules and printed circuit assemblies (including with using Chip-on-board and Chip-on-flex technologies for assembling) have been studied.

Evaluation of in-situ optical loss of polyimide-coated optical fiber under hydrothermal environments

When distributed fiber optic sensing (DFOS) devices are deployed in a geothermal borehole, the optical fiber as the key element, must be able to withstand the harsh environment because the temperature of the geothermal boreholes is higher than 250 °C in most cases. Understanding the deterioration behavior of optical fibers in hydrothermal conditions higher than 250 °C is important for predicting the lifetimes of DFOSs in operation.Geophysical equipment using optical fiber sensing was developed for in-situ measurement of the optical loss of optical fibers under hydrothermal conditions, and a survey method was established. Using this optical fiber sensing, we characterized the deterioration behavior of single-mode polyimide-coated optical fibers. Our experiments with carbon / polyimide-coated fibers under subcritical water from 250 to 350 °C revealed that the polyimide layer and silica cladding easily dissolved in water in that environment.

Laser Processing of Polyimide and Molybdenum Substrates for Extreme Environment Electronics

A desire in today’s electronic packaging technologies is to create more dense electronic packaging schemes. One method to achieve more dense electronic package integration is to use three-dimensional interconnects to minimize interconnect physical dimensions. Three-dimensional interconnect technologies, such as interposers, require a method of connecting electronics to electronic packages vertically. Thru silicon vias are a widely studied and explored vertical interconnect technology used in a variety of electronic packaging applications. Though silicon has high material hardness, the brittle nature of silicon substrates is a concern for robustness and reliability. These concerns only increase when the desired interconnect application is in extreme environments, such as cryogenic temperatures. A potential alternative to silicon in thru-via applications in extreme environments is molybdenum. Molybdenum is a commonly used material in many applications, such as automotive and aerospace, and has high material strength. Molybdenum is also a low coefficient of thermal expansion material, comparable to silicon, which in combination with high material strength lends to high reliability at extreme temperatures. A challenge of working with refractory metals such as molybdenum is that conventional CNC machining techniques require the use of machining coolants that may not be compatible with fabricated electronics and/or processes can become costly due to tool wear and the need for specialized equipment. Additionally, using molybdenum as a thru-via substrate requires the need for an electrically insulated layer, such as polyimide, within drilled molybdenum thru-holes to prevent the molybdenum substrate from shorting via connections. One potential solution to the above challenges is developing laser processing techniques to cut and drill molybdenum and polyimide. Laser processing is becoming a preferred method for inexpensive prototyping with high resolution and design versatility. This work seeks to meet the challenges described by developing laser cutting and drilling techniques for both molybdenum and polyimide for the use in cryogenic applications. This work will describe two laser processing configurations utilizing two different lasers to laser machine molybdenum and polyimide. This work will first describe the process strategies of laser cutting and drilling molybdenum as a stand-alone substrate. Aspects of laser processing on molybdenum, such as pattern repetitions and scanning speeds, will be described. Process parameter variations will be compared directly and evaluated. Additionally, post-laser processing steps, such as abrasive blasting, will be described and discussed. Next, the fabrication steps to achieve an insulating layer of polyimide in laser drilled holes as well as on each surface of the molybdenum will be detailed. Once polyimide has been cured, laser processing parameters to realize thru-holes in the polyimide-filled molybdenum drills will be presented. Adhesion of polyimide on the molybdenum substrate will be verified and demonstrated through the use of confocal scanning acoustic microscopy before and after polyimide laser processing. Cryogenic performance will be verified by completing confocal scanning acoustic microscopy after submersion in liquid nitrogen (~77 K) and compared with the pre-submersion microscopy images. Processes detailed in this work will open opportunities for future development of molybdenum-based interconnect structures for use in cryogenic applications. Acknowledgement We thank the Alabama Micro/Nano Science and Technology Center (AMNSTC) for providing access to fabrication and characterization facilities used in this work.

Preparation and Characterization of Fluorine-Containing Polyimide Films with Enhanced Output Performance for Potential Applications as Negative Friction Layers for Triboelectric Nanogenerators

Nanotechnologies are being increasingly widely used in advanced energy fields. Triboelectric nanogenerators (TENGs) represent a class of new-type flexible energy-harvesting devices with promising application prospects in future human societies. As one of the most important parts of TENG devices, triboelectric materials play key roles in the achievement of high-efficiency power generation. Conventional polymer tribo-negative materials, such as polytetrafluoroethylene (PTFE), polyvinylidene difluoride (PVDF), and the standard polyimide (PI) film with the Kapton® trademark based on pyromellitic anhydride (PMDA) and 4,4′-oxydianiline (ODA), usually suffer from low output performance. In addition, the relationship between molecular structure and triboelectric properties remains a challenge in the search for novel triboelectric materials. In the current work, by incorporating functional groups of trifluoromethyl (–CF3) with strong electron withdrawal into the backbone, a series of fluorine-containing polyimide (FPI) negative friction layers have been designed and prepared. The derived FPI-1 (6FDA-6FODA), FPI-2 (6FDA-TFMB), and FPI-3 (6FDA-TFMDA) resins possessed good solubility in polar aprotic solvents, such as the N,N-dimethylacetamide (DMAc) and N-methyl-2-pyrrolidone (NMP). The PI films obtained via the solution-casting procedure showed glass transition temperatures (Tg) higher than 280 °C with differential scanning calorimetry (DSC) analyses. The TENG prototypes were successfully fabricated using the developed PI films as the tribo-negative layers. The electron-withdrawing trifluoromethyl (–CF3) units in the molecular backbones of the PI layers provided the devices with an apparently enhanced output performance. The FPI-3 (6FDA-TFMDA) layer-based TENG devices showcased an especially impressive open-circuit voltage and short-circuit current, measuring 277.8 V and 9.54 μA, respectively. These values were 4~5 times greater when compared to the TENGs manufactured using the readily accessible Kapton® film.

Construction of transfer-free regular through-pore polyimide composite microfiltration membranes via amphiphilic dendron-assisted breath-figure method for water treatment

Regular through-pore membranes exhibit extremely high productivity and size-selective capabilities. Previous studies have demonstrated that the use of a polymer alone on a solid substrate surface hinders the formation of regular through-pore membranes. In this study, amphiphilic dendrons were used as surfactants to concentrate the functional groups and strengthen the weak bonding forces between the molecules, which is conducive to the formation of regular through-pores in the membrane. The amphiphilic dendrons were mixed with commercial-grade polyimide (PI) using chloroform as the solvent, and the solution was evenly coated on the surface of the filter paper. Using the breath-figure method, an ultrathin regular through-pore PI layer was formed directly on the surface of the filter paper. The SEM image shows that regular through-pores were formed only on the surface of the substrate. The preparation process used in this study eliminates the need to transfer ultrathin and weak membranes to the substrate surface, which simplifies the membrane-making process. Pure water and yeast solution filtration tests were conducted on the composite membrane prepared with a 5 mg/ml dendron solution. A pure water permeance of 118,826 L m-2h−1 bar−1 (LMH/bar) was obtained, the yeast solution permeance and rejection are 17,410 LMH/bar and 92.85 %, respectively. The yellow, turbid, muddy water was successfully purified to clean water. The original performance of the fouled membrane was restored after only 30 s of water flushing. This study proposes a new approach to fabricate high-efficiency regular through-pore PI composite microfiltration membranes.

Utilizing 2D materials in liquid crystal–based electro-optic devices: A perspective

The alignment agent plays a crucial role in the electro-optical characteristics of an electro-optic liquid crystal (LC) device. Conventionally, rubbed polyimide (PI) layers have been utilized as alignment agents in LC devices. However, these organic PI layers are sensitive to UV rays and high temperatures. The rubbing procedure involved in preparing PI layers also introduces drawbacks, including non-uniform brightness due to uneven rubbing mechanisms and the presence of residual fiber dust. In our recent research, we demonstrated that various hexagonal 2D (inorganic) materials, such as monolayer graphene, monolayer tungsten diselenide (WSe2), and monolayer hexagonal boron nitride (h-BN) nanosheets, can effectively serve as planar-alignment agents in electro-optic LC devices. In this Perspective, we review the rubbing-free LC alignment process, which relies on the coherent overlay of the benzene rings of LC molecules on the hexagonal lattice structure of 2D materials. We review our recent results on LC devices utilizing 2D materials as alignment agents, highlighting their potential advantages. Furthermore, we discuss the challenges associated with this research field. Finally, we provide our perspectives on the future directions and opportunities for advancing this area of study, aiming to overcome challenges and extend the benefits of employing 2D materials as planar-alignment agents in electro-optic LC devices.

Optical Filters with Asymmetric Transmittance Depending on the Incident Angle, Produced Using Liquid Crystalline Ink (Louver LC Filters).

In many situations in everyday life, sunlight levels need to be reduced. Optical filters with asymmetric transmittance dependent on the incident angle would be useful for sunglasses and vehicle or architectural windows, among others. Herein, we realized the production of optical filters, called "louver filters", comprising HAN-type LC film produced using liquid crystalline ink with dichroic dyes. For the formation of the HAN-type LC film, the liquid crystalline ink was aligned on a rubbed polyimide layer and polymerized by UV irradiation. Two kinds of filters are proposed: one is a filter composed of HAN-type LC film and a polarizer, and the other is composed of two HAN-LC films with a half-wave plate between them. The dependence of the asymmetric transmittance on the incident angle was confirmed for these filters. The dependence changed depending on the pretilt angle of the alignment layers. Photographs taken with the optical filters displayed their effectiveness.

Electrically Tunable Liquid Crystal Phase Grating with Double Period Based on the VIS Mode

A tunable liquid crystal (LC) phase grating based on vertical-field in-plane electrical switching (VIS) is proposed. The tunable LC phase grating is composed of four parts: an LC layer, the top-plane and bottom-plane electrodes, the polyimide (PI) layer, and the top and bottom periodical strip electrodes. On the one hand, a large period LC phase grating can be obtained by applying voltage to the upper plane electrode and the lower periodic strip electrodes. On the other hand, a small period LC phase grating can be obtained by applying voltage to the lower plane electrode and the upper period electrodes. As a result, two kinds of LC phase grating with different periods can be realized by changing the driving scheme. Naturally, the diffraction angle can be adjusted by controlling different LC phase grating periods. The simulation results show that this tunable LC phase grating based on the VIS mode has a relatively short response time and low operating voltage (5.4 V). These characteristics make the tunable LC phase grating have good application prospects in holographic 3D or augmented reality (AR) display.

Crosstalk-free large aperture electromagnetic 2D micromirror for LiDAR application

This paper presents a novel design of a 2D electromagnetic micromirror without crosstalk. The proposed micromirror uses a flexible printed circuit board (FPCB) and four layers of coils embedded in the polyimide layers. The insulated layers of the coil allow for independent actuation of the mirror plate to rotate about two orthogonal axes. The diamond shaped micromirror uses a hyperbola-shaped magnetic field on the coils under the mirror plate and a 45-degrees magnetic field on the coils embedded in the FPCB frame to eliminate the mechanical crosstalk. Finite element analysis was used to predict the novel 2D micromirror’s behavior. The novel 2D micromirror prototype is used in scanning LiDAR, The results indicate that the crosstalk-free pattern yielded significantly clearer results, particularly for detecting object boundaries and reducing barrel distortion. The experimental test has verified the novel crosstalk-free 2D micromirror working principle and showed good scanning quality: no crosstalk and an improvement in the horizontal field of view up to 19% But with the cost of reducing the vertical field of view by up to 12%. The novel 2D micromirror prototype has a large aperture of 19 × 19 mm2, which is very suitable for coaxial scanning LiDAR.

Fluorinated polyimide for controlling pretilt angle of liquid crystals by plasma treatment

ABSTRACT The pretilt angles of LC molecules can be controlled by tetrafluoromethane (CF4) plasma treatment. For conventional polyimide layers, the homogeneous alignment turns homeotropic owing to the invasion of fluoride atoms, which leads to the wettability transition from being hydrophilic to hydrophobic. The different treatment times generate variable pretilt angles such that the values of pretilt angles can be changed from 7.21ο to 79.53ο, and the polar anchoring energy can be tuned continuously. This technique can provide a reversible alignment layer that can be controlled by applying different plasmas of CF4 and O2. Moreover, a hybrid-aligned LC cell with patterned displays based on different pretilt angles, was proposed herein.

Dual-frequency switchable bandpass filter in the terahertz range based on enhanced trapped-mode resonances

We propose a high-quality and mechanically tunable dual-band narrow bandpass filter working in the THz range. Its high transmittance and modulation depth are verified both by simulations and experiments. The proposed design consists of two metasurfaces with concentric fabricated meta-atoms back-to-back on the two sides of a thin polyimide layer. When the polarization of the incident THz waves changes from y to × direction, the modulation depth of transmittance monotonically changes from 95.46% to a few percent at the resonance frequencies of 0.481 THz and inversely varies from a few percent to 97.62% at the resonance frequency of 0.931 THz. The analysis of in-plane and inter-planar distributions of induced surface current reveals that the narrow bandpass response is attributed to the excitation of “trapped mode”. The induced antiphase current excitation between the two metasurfaces not only lower the dipole moment but also weakly couple to external electromagnetic fields, consequently, leading to the high transmittance and narrow bandwidth. These features of such a simple device potentially can contribute to the design of much more advanced THz modulators and other THz applications in the future.

Wireless Power Transfer to Electrothermal Liquid Crystal Elastomer Actuators.

Wireless actuation of electrically driven soft actuators is of paramount importance for the development of bioinspired soft robotics without physical connection or on-board batteries. Here, we demonstrate untethered electrothermal liquid crystal elastomer (LCE) actuators based on emerging wireless power transfer (WPT) technology. We first design and fabricate electrothermal LCE-based soft actuators that consist of an active LCE layer, a conductive liquid metal-filled polyacrylic acid (LM-PA) layer, and a passive polyimide layer. LM can function not only as an electrothermal transducer to endow resulting soft actuators with electrothermal responsiveness but also as an embedded sensor to track the resistance changes. Various shape-morphing and locomotive modes such as directional bending, chiral helical deformation, and inchworm-inspired crawling can be facilely obtained through appropriately controlling the molecular alignment direction of monodomain LCEs, and the reversible shape-deformation behaviors of resulting soft actuators can be monitored in real-time through resistance changes. Interestingly, untethered electrothermal LCE-based soft actuators have been achieved by designing a closed conductive LM circuit within the actuators and combining it with inductive-coupling WPT technology. When the resulting soft actuator approaches a commercially available wireless power supply system, an induced electromotive force can be generated within the closed LM circuit, which results in Joule heating and wireless actuation. As proof-of-concept illustrations, wirelessly driven soft actuators that can exhibit programmable shape-morphing behaviors are demonstrated. The research disclosed herein can provide insights into the development of bioinspired somatosensory soft actuators, battery-free wireless soft robots, and beyond.

The sensory and photo-catalytic properties of graphene oxide and polyimide thin films implanted by 1500 keV Cu ions

Thin films of polyimide (PI) and graphene oxide (GO) were exposed to the accelerated Cu-ions with an energy of 1500 keV at different ion fluences (3.75 × 1012; 3.75 × 1014; 1 × 1016) cm−2. The reason for Cu-ion irradiation lies in the modification of thin PI and GO layers and their subsequent use in electronics, photo-catalysis and humidity sensing. It was expected that three ways would primarily carry out modification: i) interaction of the accelerated ions with atoms and electrons of the irradiated films, ii) implantation of Cu ions inside the matrices and their attachment to the structures in the form of CuO, and iii) formation of C and Cu aggregates and Cu nanoparticles in the subsurface layer to form an electrically conductive network. The effects of the interactions of energetic Cu-ions on the PI and GO matrices, including the prediction of the depth of Cu ion penetration, were simulated by SRIM software. Elemental changes, including the depth profiles of implanted Cu-ions, were investigated by Rutherford backscattering spectrometry (RBS) and Elastic recoil detection analysis (ERDA). Changes in the chemical bonding on the PI and GO surfaces were studied by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The effect of energetic Cu-ions on the surface morphology was analyzed by Atomic force microscopy (AFM). For the possible application of PI and GO composites in electronics and sensory, the sheet resistivity were measured by the two- point method and the effect of air humidity on electrical properties was studied. Furthermore, the degradation of Rhodamine B solution in the presence of prepared composites under UV-light irradiation was measured for possible use in photo-catalysis. It was found that the interaction of Cu- ions with the matrix leads to the release of oxygen and hydrogen, resulting in an increase in carbon concentration. The increase in carbon concentration leads to an increase in the electrical conductivity of both materials. The irradiation with Cu ion fluence of 1 × 1016 cm−2 probably formed in PI a subsurface conducting network that reduced the sheet resistivity by almost eleven orders of magnitude. The ion irradiation by Cu ion with fluences below 1 × 1016 cm−2 enhances the photo- catalytic properties of both used materials and the best result was achieved in the case of PI irradiated by the ion fluence of 3.75 × 1014 cm−2.

Enhancement of Stability in n-Channel OFETs by Modulating Polymeric Dielectric.

In this study, a high-K material, aluminum oxide (AlOx), as the dielectric of organic field-effect transistors (OFETs) was used to reduce the threshold and operating voltages, while focusing on achieving high-electrical-stability OFETs and retention in OFET-based memory devices. To achieve this, we modified the gate dielectric of OFETs using polyimide (PI) with different solid contents to tune the properties and reduce the trap state density of the gate dielectric, leading to controllable stability in the N, N'-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C13)-based OFETs. Thus, gate field-induced stress can be compensated for by the carriers accumulated due to the dipole field created by electric dipoles within the PI layer, thereby improving the OFET's performance and stability. Moreover, if the OFET is modified by PI with different solid contents, it can operate more stably under fixed gate bias stress over time than the device with AlOx as the dielectric layer only can. Furthermore, the OFET-based memory devices with PI film showed good memory retention and durability. In summary, we successfully fabricated a low-voltage operating and stable OFET and an organic memory device in which the memory window has potential for industrial production.