Conductivity Of Films Research Articles

Effect of Superfilling and Leveling Inhibitors in Hybrid Additives on the Microstructure Evolution of Electroplated Copper Interconnect Films during Self-Annealing

Abstract As the feature size shrinks, the main challenge for copper interconnect electroplating is to minimize interconnect resistance while ensuring the void-free feature filling, which is realized by the interaction of additives during electroplating. Among additives, hybrids are considered suitable for damascene filling because they combine type-I (superfilling) and type-II (leveling) inhibitors. However, it is generally believed that the more inhibitory an additive is, the more impurities it introduces into the films, thereby hindering grain growth during self-annealing, which paradoxically limits the conductivity of copper interconnects. To balance the inhibition of hybrid additives with their ability to introduce impurities, the effect of hybrid additives on the microstructure evolution of the films during self-annealing is explored in terms of texture, grain size, and impurity density, which are considered to determine the conductivity of copper films. We find that the {111} texture increases as the percentage of type-I inhibitors increases, whose relative texture coefficient reaches 97% after self-annealing due to the adsorption of hybrid additives on non-<111>-oriented crystal planes. Additionally, the impurity content and grain size increase as type-I inhibition increases, and so does the film conductivity after self-annealing, due to the possible promotion from impurities to the grain growth.

Thin Conducting Films: Preparation Methods, Optical and Electrical Properties, and Emerging Trends, Challenges, and Opportunities

Thin conducting films are distinct from bulk materials and have become prevalent over the past decades as they possess unique physical, electrical, optical, and mechanical characteristics. Comprehending these essential properties for developing novel materials with tailored features for various applications is very important. Research on these conductive thin films provides us insights into the fundamental principles, behavior at different dimensions, interface phenomena, etc. This study comprehensively analyzes the intricacies of numerous commonly used thin conducting films, covering from the fundamentals to their advanced preparation methods. Moreover, the article discusses the impact of different parameters on those thin conducting films’ electronic and optical properties. Finally, the recent future trends along with challenges are also highlighted to address the direction the field is heading towards. It is imperative to review the study to gain insight into the future development and advancing materials science, thus extending innovation and addressing vital challenges in diverse technological domains.

Enhancing electrical conductivity of RuO2 nanosheet-coated films by enlarging the nanosheet area

This study focused on enhancing the electrical conductivity of metal oxide nanosheet films by increasing the size of the nanosheets to promote the electron flow in the desired in-plane direction. We developed a method for increasing the size of RuO2 metal oxide nanosheets, a 2D material, by controlling the heat-treatment process. The size of the RuO2 nanosheets increased from 0.7 to 3.5 μm by modifying the heat-treatment conditions of KxRuO2, which was used as the precursor material. As a consequence, the electrical conductivity of the large-sized-RuO2 nanosheet-coated films was eight times higher than that of their small-sized counterparts. This lower resistance was attributed to the minimal number of contacts required for electron flow; the contact resistance between the nanosheets being higher than the intrinsic resistance. The proposed approach for enhancing the conductivity of metal oxide 2D materials is very promising and is expected to significantly contribute to the development of advanced flexible electronic devices.

Understanding the Anomalous Thermoelectric Behavior of Fe-V-W-Al-Based Thin Films.

We investigated the thermoelectric and thermal behavior of Fe-V-W-Al-based thin films prepared using the radio frequency magnetron sputtering technique at different oxygen pressures (0.1-1.0 × 10-2 Pa) and on different substrates (n, p, and undoped Si). Interestingly, at lower oxygen pressure, formation of a bcc-type Heusler structure was observed in deposited samples, whereas at higher oxygen pressure, we have noted the development of an amorphous structure in these samples. Our findings indicate that the moderately oxidized Fe-V-W-Al amorphous thin film deposited on the n-Si substrate possesses a large magnitude of S ∼ -1098 ± 100 μV K-1 near room temperature, which is almost double the previously reported value for thin films. Additionally, the power factor (PF) indicated an enormously large value of ∼33.9 mW m-1 K-2 near 320 K. The thermal conductivity of the amorphous thin film is also found to be 2.75 Wm-1 K-1, which is quite lower compared to bulk alloys. As a result, the maximum figure of merit is estimated to be extremely high, i.e., ∼3.9 near 320 K, which is among one of the highest reported values so far. The anomalously large value of Seebeck coefficient and PF has been ascribed to the unusual composite effect of the metallic amorphous oxide phase and insulating substrate possessing a large Seebeck coefficient.

Ultrasensitive Flexible Strain Sensor Made with Carboxymethyl-Cellulose-Anchored Carbon Nanotubes/MXene for Machine-Learning-Assisted Handwriting Recognition.

The combination of wearable sensors with machine learning enables intelligent perception in human-machine interaction and healthcare, but achieving high sensitivity and a wide working range in flexible strain sensors for signal acquisition and accurate recognition remains challenging. Herein, we introduced carboxymethyl cellulose (CMC) into a carbon nanotubes (CNTs)/MXene hybrid network, forming tight anchoring among the conductive materials and, thus, bringing enhanced interaction. The silicone-rubber-encapsulated CMC-anchored CNTs/MXene (CCM) strain sensor exhibits an excellent sensitivity (maximum gauge factor up to 71 294), wide working range (200%), ultralow detection limit (0.05%), and outstanding durability (over 10 000 cycles), which is superior to most of the recently reported counterparts also based on a conductive composite film. Moreover, the sensor achieves seamless integration with human skin with the help of a poly(acrylic acid) adhesive layer, successfully obtaining stable and clear waveforms with meaningful profiles from the human body. On this basis, we proposed and realized a novel in-air handwriting recognition method via extracting multiple features of high-quality strain signals assisted by deep neural networks, achieving a high classification accuracy of 98.00 and 94.85% for Arabic numerals and letters, respectively. Our work provides an effective approach for significantly improving strain sensing performance, thereby facilitating innovative applications of flexible sensors.

Photolithography-Free, Solution-Processable Perovskite Electrodes for High-Performance Organic Transistors.

Solution-processable electrodes are promising for next-generation electronics due to their simplicity, cost-effectiveness, and potential for large-area fabrication. However, current solution-processable electrodes based on conductive polymers, carbon-based compounds, and metal nanowires face challenges related to stability, patterning, and production scalability. Here we introduce a novel approach using 3D tin halide perovskites (THPs) combined with a photolithography-free solution patterning technique to fabricate solution-processed electrodes. We demonstrate the preparation of highly conductive CsSnI3 films (234.9 S cm-1) and the fabrication of patterned 35 × 35 perovskite electrode arrays on a 4-in. silicon wafer. These electrodes, used as source/drain electrodes in organic transistors, resulted in devices showing high uniformity and stability. This electrode fabrication strategy is also applicable to other 3D THPs like FASnI3 and MASnI3, showcasing versatility for diverse applications. The results highlight the feasibility and advantages of using 3D THPs as solution-processable electrodes, providing a new material system for the advancement of solution-processed electronics.

Heat transport in SiCOH thin films: an experimental and molecular dynamics study

Carbon-doped silicon dioxide (SiCOH) film is currently regarded as one of the most promising low-k materials in the integrated circuits (ICs) industry for advanced technology nodes. However, there have been limited studies on the thermal properties of SiCOH compared to its electrical and mechanical properties. In this study, we investigate the thermal conductivity of SiCOH thin films through molecular dynamics simulations (MD) and experimental characterizations. Our findings indicate that the size effect on thermal conductivity at 300 K is negligible when the thickness of SiCOH film is less than 20 nm. Additionally, we observe a contrasting temperature dependence law for the thermal conductivity of SiCOH thin films compared to crystal SiO2 thin films. Furthermore, we demonstrate a significant decrease in thermal conductivity with increasing porosity in SiCOH films; specifically, an increase in porosity from 5.35% to 42.77% results in a 60% reduction in thermal conductivity. Moreover, we validate our simulation results by characterizing the thermal conductivity of SiCOH using 3 ω method.

High toughness, flexible and thermally conductive fluorine rubber composite films reinforced by hexagonal boron nitride flakes for thermal management

The rapid advancement of electronic information technology has generated a substantial demand for polymer-based thermal management materials. In order to address the challenges of heat dissipation and avoid signal interference, it is essential to develop polymer-based thermal management materials with both high thermal conductivity and low dielectric properties. Herein, hexagonal boron nitride flakes (h-BNFs) with a high aspect ratio and some hydroxyl groups were prepared using the high pressure homogenization technique. Subsequently, h-BNF/fluorine rubber (h-BNF/FKM) composite films were fabricated through a simple and scalable blade coating method. During the blade coating process, most of the h-BNFs can align with their (002) crystal planes paralleling to the horizontal direction. In addition, the rest of the h-BNFs will randomly distribute and overlap with each other, combining with the horizontally aligned h-BNFs to form a distinctive three-dimensional packing network. This unique network structure enables the h-BNF/FKM composite films to have thermal conductivities of up to 0.44 W/(m·K). Moreover, the introduction of h-BNFs can effectively reduce the dielectric constants and dielectric losses of FKM films. More importantly, the h-BNF/FKM composite films also exhibit outstanding mechanical toughness, excellent flexibility, good adhesion and improved flame-retardancy, providing promising applications in the electronic device thermal management.

Characterization of Ultrathin Conductive Films Using a Simplified Approach for Terahertz Time-Domain Spectroscopic Ellipsometry

Characterization of Ultrathin Conductive Films Using a Simplified Approach for Terahertz Time-Domain Spectroscopic Ellipsometry

Preparation and characterization of ZnS/metal/ZnS transparent conductive multilayer films with different metal layers

ZnS/metal/ZnS transparent conductive multilayer films were deposited on quartz glass by pulsed laser deposition at room temperature with Au, Ag and Cu as the metal layers, and annealed in air at 100, 200 and 300℃ for 1 h. XRD patterns show that β -ZnS(111) diffraction peak of ZnS/Au/ZnS is stronger and sharper than the other two samples, indicating that its crystalline quality is the best. SEM images show the good structural homogeneity of the samples with smooth and compact film surfaces. When the annealing temperature increases from 100 to 300℃, the sheet resistance decreases first and then increases, while the carrier concentration changes in the opposite trend. The maximum transmittance (~85%) for ZnS/Au/ZnS in the visible light region is observed when the sample is annealed at 200℃. The figure of merit is calculated, and the best sample suitable for transparent conductive electrode is determined.

Large Rashba spin-orbit coupling in metallic SrTaO3 thin films

Abstract We fabricated conductive SrTaO3 epitaxial films on insulator substrates and measured Rashba parameter using weak anti-localization analysis. The Rashba parameter, reaching up to 9.9×10-13 eVm, is the highest among metallic oxides and is comparable to the LaAlO3/SrTiO3 interface, which is widely used in Rashba effect studies. This indicates the potential for oxide-based spintronic devices. To use them as devices, it is important to investigate how film thickness affects resistivity. Films ranging from 8.6 to 25 nm exhibited metallic conduction, but those thicker than 25 nm showed an unexpected increase in resistivity, suggesting instability of the meta-stable Ta4+ state

Tunable thermal conductivity of surface phonon polaritons in SiC thin film

As an additional heat carrier besides phonons and electrons, the surface phonon polariton (SPhPs) possesses a large potential to increase the thermal conductivity. In this work, the influences of SPhP frequency, film thickness and film permittivity on the SPhP-contributed thermal conductivity of SiC thin films were probed. Results show that: there are two frequency zones which could lead to a much high thermal conductivity, i. e. the frequency which approaching zero and the frequency in singularity zone. The thermal conductivity decreases with the increase of the film thickness, following a power-function relationship, and a thin film with a thickness of 10-nm could have a thermal conductivity higher than 1×104 W·m−1·K−1. However, the experimental observation of this high thermal conductivity is still difficult because of the size effect of the film length. The thermal conductivity will increase with the decrease of the imaginary part of the film permittivity and/or increase of the real part of the film permittivity, and there is approximately a reciprocal dependence of thermal conductivity on the imaginary part of the film permittivity. The thermal conductivity could be tuned by several times with tailoring its permittivity through adding fillers in it or adding dopant in it. This work provides some potential methods to tune the SPhP thermal conductivity in SiC thin film, which could help its application in microscale heat dissipation.

Design of a 10.8 to 34.6 GHz Ultra‐Wideband Transparent Metamaterial Absorber Using an Equivalent Circuit Model

AbstractIn this paper, an ultra‐wideband metamaterial absorber (UWMA) is proposed and demonstrated by using a transparent and flexible sandwich structure, which consists of a top patterned double‐square loop (DSL) of conductive film, the polymer interlayer, the bottom conductive film. The work presents the UWMA's equivalent circuit model for a macroscopic analysis of its physical mechanism. Further, optimizing UWMA's structural parameters using this equivalent circuit model can greatly enhance its efficiency. The absorption coefficient of the designed structure achieves over 90% within the wide frequency range from 10.82 to 34.59 GHz due to the overlapping of three absorption bands. The experimental results indicate that the absorption coefficient of the fabricated structure exceeds 60% in the frequency range of 10.45–35.28 GHz, and reaches 90% in the majority of frequency range of 10.71–28.51 GHz, while its averaged optical transparency in the visible spectrum exceeds 75%. The UWMA achieves high transparency due to a small ratio of the surface area occupied by the ITO pattern to the total area and realizes multiple‐resonance ultra‐wideband absorption with conformality while maintaining a thickness of only 2.2 mm, which has diverse applications in the field of electromagnetics, including aircraft stealth, transparent chambers, and flexible electronic screens.

A high sensing performance piezoresistive sensor based on TPU/c-MWCNTs/ V2CTX-MXene electrospun film for human motion detection

Since wearable pressure sensors have promising applications in the fields of human physiological signal detection and bionic robots, there is an urgent need for wearable pressure sensors with comprehensive attributes such as high sensitivity and wide detection range. Here, we introduce a facile electrospinning process to fabricate a film composed of thermoplastic polyurethane/carboxyl multiwalled carbon nanotube/V2CTX-MXene (TPU/c-MWCNTs/V2C). This film has high sensitivity and great linearity, designed for flexible piezoresistive sensors. To further enhance sensor performance, we applied a spin-coating of polydimethylsiloxane (PDMS) on the sandpaper surface to create a top substrate with intermittent spinosum structures. Additionally, a layer of TPU fibers was electrospun between the conductive film and the interdigitated electrodes. The assembled components form a flexible piezoresistive sensor with a wide detection range of 0–200 kPa, a high sensitivity of 545.2 kPa−1, a low detection limit of 5 Pa, a short response time of 48 ms, and excellent long-term durability after 7000 loading/unloading cycles, making the piezoresistive sensor highly discriminating for detecting complex human movements. Thanks to the great sensing performance and stable structure, we conducted various demonstrations to capture human physiological signals, including signals of muscle activity and pulse. These findings indicate the potential of the designed flexible pressure sensor for applications in electronic skin and smart devices.

Room temperature deposited highly conductive HfNx films for high-performance HfN/Si junction diodes

Transition metal nitrides are valuable materials for many technological applications due to their favorable physical characteristics, including conductivity, high temperature stability, and hardness. Among them, hafnium nitride (HfN) thin films of high attributes are crucial for semiconductor applications. However, achieving performance efficiency of HfN films with desired electrical performance via conventional deposition methods is a challenging task. Herein, we have achieved room temperature growth of highly oriented cubic HfN thin film grown on Si substrate by process optimization of radio frequency (RF) magnetron sputtering. HfN thin films were structurally, morphologically, and electrically characterized. The metallic behavior of HfN films was confirmed through current-voltage measurements; it showcased excellent electrical conductivity, signifying low resistivity (≈ 0.55 kΩ sq-1), revealing promising evidence for its potential practical application. Moreover, the first-principles calculations were also conducted to gain further insights into the electrical performance of the HfN films. These findings lay a solid foundation for further exploration and development of HfN-based junction diodes, as the observed characteristics offer significant potential for enhancing device performance in various electronic domains.

Transcriptomic Analysis Reveals the Heterogeneous Role of Conducting Films Upon Electrical Stimulation.

Central nervous system (CNS) injuries and neurodegenerative diseases have markedly poor prognoses and can result in permanent dysfunction due to the general inability of CNS neurons to regenerate. Differentiation of transplanted stem cells has emerged as a therapeutic avenue to regenerate tissue architecture in damaged areas. Electrical stimulation is a promising approach for directing the differentiation outcomes and pattern of outgrowth of transplanted stem cells, however traditional inorganic bio-electrodes can induce adverse effects such as inflammation. This study demonstrates the implementation of two organic thin films, a polymer/reduced graphene oxide nanocomposite (P(rGO)) and PEDOT:PSS, that have favorable properties for implementation as conductive materials for electrical stimulation, as well as an inorganic indium tin oxide (ITO) conductive film. Transcriptomic analysis reveals that electrical stimulation improves neuronal differentiation of SH-SY5Y cells on all three films, with the greatest effect for P(rGO). Unique material- and electrical stimuli-mediated effects are observed, associated with differentiation, cell-substrate adhesion, and translation. The work demonstrates that P(rGO) and PEDOT:PSS are highly promising organic materials for the development of biocompatible, conductive scaffolds that will enhance electrically-aided stem cell therapeutics for CNS injuries and neurodegenerative diseases.

Bimodal functionality of highly conductive nanostructured silver film towards improved performance of photosystem I-based graphene photocathode

We present the novel design of photosystem I (PSI)-based biosolar cell, whereby conductive transparent electrode materials, such as ITO or FTO, are replaced with glass covered with silver island film. This nanostructured metallic layer combines high electric conductance with enhancing the absorption efficiency of the PSI biocatalyst via the plasmonic effect. We demonstrate strong enhancement of the photocurrent generated in the biohybrid electrode composed of oriented layers of PSI reaction centers due to plasmonic interactions of the PSI fluorophores and redox centres with the conductive silver island film.

Flexible and anisotropically conductive film by assembly of silicone rubber and cobalt-coated glass fiber composites

In this study, we prepared electromagnetic cobalt-coated glass fiber (Co@GF) composites via an electroless plating method. Subsequently, a conductive sandwich flexible film consisting of Co@GF composites and liquid silicone rubber (RTV-2) was successfully formed using the tape casting method at room temperature. Based on the perfect coating and excellent electrical conductivity of the Co@GF composites, the resultant RTV-2/Co@GF/RTV-2 sandwich flexible film showed a low volume resistivity of 0.264 Ω·cm and could stretch to 100% (of 4.40 Ω·cm) without obvious fracture. When a magnetic field was applied during the curing process, the electromagnetic Co@GF composites were aligned automatically in the RTV-2 matrix because of their ferromagnetic nature. The as-prepared film exhibited anisotropy in its electrical performance. The volume resistivity parallel to the magnetic field direction is approximately two times lower than that in the perpendicular direction. The maximum difference in the volume resistivity (ρ∥ = 0.768 Ω·cm and ρ⊥ = 1.549 Ω·cm) was obtained at a magnetic field intensity of 800 mT. In addition, a magnetic field intensity of 100 mT helps improve the electrical conductivity of the as-obtained sandwich film. The anisotropic RTV-2/Co@GF/RTV-2 sandwich flexible film is considered a promising flexible electronic sensor, where discrepant inductive sensitivity is required in orthogonal directions.

Direct Writing of graphene/graphitic foam through picosecond pulsed laser-induced transformation of soluble polyimide suspension

We report the direct writing of graphene/graphitic foam with high electrical conductivity using laser-induced-transformation of polyimide (PI) resin films on glass surfaces. Raman spectroscopy of the treated surfaces indicated that average laser power irradiation between 900-1500 kW/cm2 transformed the PI film into a few layered graphene-dominated film, and the increase in irradiation power above 1500 kW/cm2 led to the formation of graphitic (multilayered graphene) material. The electrical conductivity of the transformed film was between 5800±750 S/m (lower power irradiation) and 1250±300 S/m (higher laser power irradiation). SEM imaging showed that the transformed material has a closed cell foam morphology enclosed between the smooth top and bottom layers. The results indicate that heat treatment of the polyimide suspension films, and subsequent ultra-short, pulsed laser irradiation resulted in a closed-cell graphene/graphitic foam with high electrical conductivity. The pore aspect ratio, density, and film conductivity are used to estimate the conductivity of the solid phases in the laser-treated films at different powers. Laser-induced transformation of the PI suspension into graphene/graphitic foam is conducive to additive manufacturing and may enable the direct printing of graphitic foam-based three-dimensional components.

Suppression of cracking induced by epitaxial strain relaxation using a relaxation absorber during the transfer of epitaxial thin films of anatase-type Nb:TiO2

This work developed a technique for fabricating flexible epitaxial thin films of anatase-type Nb:TiO2 (epitaxial TNO) via a transfer process. In our prior work, epitaxial TNO deposited on LaAlO3 (001) single crystal substrates was lifted off and affixed to flexible polymeric sheets. However, many cracks occurred on the surfaces of the transferred thin films, such that the conductivity of the epitaxial TNO was drastically decreased. This loss of conductivity was attributed to the interruption of current paths by the cracks. These numerous cracks were linear and in most cases were oriented either parallel to the [100]anatase∥[100]LAO direction or parallel to the [010]anatase∥[010]LAO direction (where the subscripts anatase and LAO represent the materials for each Miller index). Therefore, cracking likely occurred as a consequence of the relaxation of epitaxial strain and a return to the original axial lengths of the TNO during the transfer process. In the present work, the surface of epitaxial TNO was coated with the ductile polymer SU-8 3050 as a relaxation absorber prior to the transfer. This modified transfer process greatly reduced crack formation in the TNO such that the conductivity of the thin film was improved by two orders of magnitude. Thus, pre-coating with a ductile relaxation absorber was shown to effectively suppress the cracking of flexible epitaxial TNO.