High Dielectric Constant Films Research Articles

Self-Assembled MXene@Fluorographene Hybrid for High Dielectric Constant and Low Loss Ferroelectric Polymer Composite Films.

Modern electrical applications urgently need flexible polymer films with a high dielectric constant (εr) and low loss. Recently, the MXene-filled percolative composite has emerged as a potential material choice because of the promised high εr. Nevertheless, the typically accompanied high dielectric loss hinders its applications. Herein, a facile and effective surface modification strategy of cladding Ti3C2Tx MXene (T = F or O; FMX) with fluorographene (FG) via self-assembly is proposed. The obtained FMX@FG hybrid yields high εr (up to 108 @1 kHz) and low loss (loss tangent tan δ = 1.16 @ 1 kHz) in a ferroelectric polymer composite at a low loading level (the equivalent of 1.5 wt % FMX), which is superior to its counterparts in our work (e.g., FMX: εr = 104, tan δ = 10.71) and other studies. It is found that the FG layer outside FMX plays a critical role in both the high dielectric constant and low loss from experimental characterizations and finite element simulations. For one thing, FG with a high F/C ratio would induce a favorable structure of high β-phase crystallinity, extensive microcapacitor networks, and abundant interfacial dipoles in polymer composites that account for the high εr. For another, FG, as a highly insulating layer, can inhibit the formation of conductive networks and inter-FMX electron tunneling, which is responsible for conduction loss. The results demonstrate the potential of a self-assembled FMX@FG hybrid for high εr and low loss polymer composite films and offer a new strategy for designing advanced polymer composite dielectrics.

High dielectric transparent polymer composite with well-organized carboxymethyl cellulose microfibers in silicon elastomer fabricated under direct current electric field

The combination of transparency, high dielectric permittivity, biocompatibility and flexibility is highly desired in the embedded capacitors. Herein, we show that assembling biodegradable sodium carboxymethyl cellulose (CMC) microfibers in biocompatible silicon elastomer (PDMS) under direct current (DC) electric field enables the production of high dielectric constant composite film with above desired properties. This process leads to the formation of columns of CMC microfibers spanning across the thickness direction, thus generating microfiber depleted regions in between fibers and polymer matrix. The as-prepared composite film with CMC (15 wt%) aligned exhibits a remarkable and an almost sevenfold higher dielectric permittivity as compared to that of the film with CMC randomly dispersed (72 vs 11.4, at 100 Hz). This high CMC loading does not compromise the flexibility and optical transmittance. Interestingly, the compression modulus along the thickness direction increases by >20 times from 16.4 MPa (CMC unaligned) to 339.9 MPa (CMC aligned). We demonstrate a facile strategy of fabricating high dielectric materials combining transparency, biocompatibility, flexibility and compression resistant, making the dielectric materials more versatile. This work shows that biomass derived CMC is a promising filler for high dielectric constant polymer composites benefiting from electric field driven construction of ordered micromorphology.

Impact of varying wet oxidation temperature in the presence of nitrogen flow on hafnium tantalum oxide films

Wet oxidation has been undergone at dissimilar temperatures from 400 until 1000 °C for deposition of high dielectric constant ternary hafnium tantalum oxide films on silicon (Si) substrates. Amorphous to polycrystalline phase transformation happened as a function of temperature. An increase in the oxygen vacancy formation was observed and the calculated k values ranged from 16.5 to 31.1. However, interfacial layer formation happened exaggeratedly at 1000 °C, which could be associated with the reduction in nitrogen accumulation at the interface between the oxide and Si at this temperature, and thus resulting in the lowest total interface trap density (Dtotal). Conductance-voltage measurement showed the location of interface states that were closer to conduction band of the oxide. The findings were in coordination with structural, morphological, and optical characteristics of the samples. A simple mechanism illustrating formation of the ternary film was also proposed.

In Situ Fabrication of High Dielectric Constant Composite Films with Good Mechanical and Thermal Properties by Controlled Reduction

As a common two-dimensional carbon material, graphene has been widely doped into polymers to prepare high-performance dielectric materials. However, the shortcomings of graphene, such as large specific surface area and poor dispersion, limit its further application. Therefore, in this work, to solve the problem regarding the uniform dispersion of graphene in the matrix, in situ polymerization was used to prepare graphene/polyimide films, in which 1,4-diiodobutane was used as a reduction agent to prevent the aggregation of graphene oxide (GO) during imidization. High dielectric constant composite films were obtained by adjusting the ratio of 1,4-diiodobutane in GO. The results show that the resulting graphene/polyimide composite film possessed a dielectric constant of up to 197.5, which was more than 58 times higher than that of the polyimide (PI) film. Furthermore, compared to the pure PI film, the composite films showed better thermal stability and mechanical properties. Thermal performance tests showed that the 1,4-diiodobutane added during the preparation of the composite film was thermally decomposed, and there was no residue. We believe our preparation method can be extended to other high dielectric composite films, which will facilitate their further development and application in high power density energy storage materials.

Enhancement of the Dielectric Properties of Polyvinyl Alcohol by Adding TiO2Nanoparticles

High dielectric constant nanocomposite polymer films based polyvinyl alcohol (PVA) with different weight ratios of nanoparticles (NPs) TiO2(1.0, 2.5, 5.0, and 10) are prepared by the casting method. The structure of TiO2NPs is studied using TEM and XRD spectra, where the FTIR spectra show a strong interaction between PVA and TiO2NPs. The addition of TiO2NPs to the composites improves their mechanical properties. The dielectric parameters and AC conductivity are explored in the 10 Hz to 107 Hz frequency range at different temperatures. PVA composite films filled with 5.0 wt% TiO2NPs exhibit the highest dielectric constant (ε′) reaching up to 26 at 25 °C and 100 Hz. The origins of the enhanced dielectric properties are investigated using theoretical predictions of the effectiveε′of composites. The activation energy of a dielectric relaxation process is computed. As the temperature rises, the relaxation time lengthens slightly. A conduction mechanism is described based on thermally activated electron hops at the Fermi edge.

(Invited) Combinatorial Synthesis and Interface Analysis for Development of High Dielectric Constant Thin Films

The development of high-dielectric constant film materials is essential for future active and passive nanoelectronics devices. By integrating combinatorial synthesis, high throughput material development, and interface analysis, we have developed a high-dielectric constant Bi-based relaxor ferroelectric film material, x[BaTiO3]–(1−x)[Bi(Mg2/3Nb1/3)O3] (BT–BMN), for film capacitors. To increase the dielectric constant, and its thermal stability, of the above relaxor ferroelectric films, a periodic Ta doping structure was introduced by combinatorial method. The periodic insertion of BT–BMN layers with a high Ta concentration eliminated the dielectric constant decrease and also the Bi segregation encountered in BT–BMN films under high-temperature conditions. Upon optimizing the BT/BMN ratio in the stack structure, the BT–BMN films exhibited a high dielectric constant (>500) and an excellent thermal stability, less than 8% in the temperature range from room temperature to 400 °C

Flexible, transparent, strong and high dielectric constant composite film based on polyionic liquid coated silver nanowire hybrid

High dielectric constant films with excellent flexibility, transparency and high strength are key materials for flexible electronic devices. Herein, a novel kind of functional hybrid (AgNW@PIL) was synthesized by forming a layer of polyionic liquid (PIL) on surfaces of silver nanowires (AgNWs), which was then added into poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) to develop a series of unique high dielectric constant films (AgNW@PIL/PVDF-HFP). Comprehensive performances of AgNW@PIL/PVDF-HFP films were studied and compared with those of AgNW/PVDF-HFP films and related composite films in literature. With the increase of AgNW@PIL content, the dielectric constant and mechanical strength significantly improve, while the light transmittance gradually decreases. At the same filler content and frequency, AgNW@PIL/PVDF-HFP has higher dielectric constant, lower dielectric loss, higher light transmittance and better mechanical properties than AgNW/PVDF-HFP. The mechanism behind these attractive results is contributed to different microstructures between AgNW/PVDF-HFP and AgNW@PIL/PVDF-HFP. Specifically, different from AgNW, AgNW@PIL has good dispersibility in PVDF-HFP, and form more micro-capacitor structure and good interface polarization effect; besides, PIL coating plays a significant role in suppressing the dielectric loss of composite films. AgNW@PIL/PVDF-HFP with only 0.4 wt% AgNW@PIL simultaneously has high tensile modulus (1152.2 MPa), high tensile strength (30.9 MPa) and large elongation at break (181.0%).

Comparative study of oxidizing ambient infused with varying nitrogen flow rates for fabrication of ternary nitrided AlZrO based MOS capacitor

High dielectric constant nitrided aluminum zirconium oxide films were successfully fabricated on silicon substrate via an oxidation process infused with different nitrogen gas flow rates at 800°C. The presence of nitrogen piling up at the interface could control the thickness of interfacial layer formation. An increase in the nitrogen gas flow rate might be effective in controlling the overall thickness of the films, yet the nitrogen piling up at the interface impeded the diffusion of oxygen to the interface. Consequently, the interface quality was affected, leading to degradation in the interface-state density. In addition, the generation of oxygen vacancies in the films, as well as the presence of nitrogen at the interstitial sites, would create a lattice polarization, which decreased the k values. Corresponding effects were also discussed in corroboration with energy band gap, effective oxide charges, and slow trap density, as well as interface-state density calculated from capacitance and conductance methods.

A Chip-First Microwave Package Using Multimaterial Aerosol Jet Printing

We show in this article two fully additively manufactured microwave packages with integrated active and passive components. Packages were constructed using a chip-first approach where package substrates (dielectrics) and interconnects (conductors) are built up around power amplifier bare die attached to carriers. Bypass capacitor dielectrics were printed using multimaterial aerosol jet printing, where aerosols of barium titanate and polyimide inks are mixed in place to fabricate a high dielectric constant polymer matrix nanocomposite film. The material properties of the film are characterized using three printed capacitors. We present S-parameter measurements to characterize small-signal performance, as well as load-pull measurements at the saturated output power. Finally, we demonstrate package performance after power cycling and temperature cycling to show the effect of aging on the part and the robustness of this packaging strategy. We measured a maximum packaged gain of 21.7 dB and a saturated output power of 21.9 dBm for a commercial-off-the-shelf (COTS) medium power amplifier specified to have a gain of 22 dB and a saturated output power of 22 dBm. The printed package-level performance is compared with the published bare die performance and a measured COTS packaged amplifier.

(Invited) Development of New High-Dielectric Constant Thin Films By Combinatorial Synthesis

The development of high-dielectric constant film materials is essential for future active and passive nanoelectronics devices. By using combinatorial synthesis, high throwput material development, we developed high-dielectric constant film materials for film capacitor and gate dielectrics.In the case of the passive devices, we focused on the power device application. Power devices such as SiC require high-temperature operational passive devices, which are capable of operating over 250°C. For module and system level advancement, the high-temperature operational passive should be developed urgently. By employing combinatorial method and the thermal diffusion theory, we found some candedates based on ferroelectric materials. For the relaxor feroelectric, the permitivity of 400 and the stability <8% from room temperature to 400°C has been obtained, which are promising as a high-temperature dielectric medium. In the presentation, we also introduce the development of new high-k gate materials for GaN and Ge channels. For a Ge channel, which has been attracting a lot of attention as a replacement for the Si channel used in current Si-based metal-oxide-semiconductor (CMOS) devices. This is because the Ge channel has high electron and hole mobility, which lead to a higher drive current, and Ge has a narrower band gap than Si thus allowing supply voltage scaling. However, Ge has the same issue as Si, namely an unintentionally oxidized layer with a low dielectric constant (~5.6) can form at an oxide/Ge interface. Furthermore, in contrast with SiO2, which is a good insulating layer for MOS devices, GeOx is thermodynamically unstable and water soluble. These properties cause high defect densities at the interface between high-k and Ge and a large hysteresis in the capacitance-voltage characteristic. To overcome these issues, we have proposed the direct growth of (110) rutile TiO2 or non-oxide materials on (100) Ge substrates.

(Invited) Development of New High-Dielectric Constant Thin Films By Combinatorial Synthesis

The development of high-dielectric constant film materials is essential for future active and passive nanoelectronics devices. By using combinatorial synthesis, high throughput material development, we developed high-dielectric constant film materials for film capacitor and gate dielectrics. In this paper, the combinatorial synthesis method and achievements concerning the dielectric materials for high temperature operational thin film capacitor and high-k dielectrics are briefly introduced.

O2 plasma treated biosensor for enhancing detection sensitivity of sulfadiazine in a high-к HfO2 coated silicon nanowire array

In this paper, highly uniform silicon nanowire (SiNW) arrays (∼30 nm in diameter) used as FET biosensors are fabricated by using a CMOS-compatible spacer image transfer (SIT) technology with high efficiency compared with conventional electron beam (E-beam) lithography. An effective biochemical sensing approach that treated with optimization of O2 plasma on the SiNW biosensors coated with a 10 nm HfO2 high dielectric constant (high-к) film is demonstrated to enhance immobilization of antibodies. Furthermore, water contact angle (WCA) measurements verify that the increased number of hydroxyl groups (OH) on the HfO2 surfaces treated with O2 plasma reaches or surpasses that on a conventional SiO2 surface. Therefore, it is observed that the IDS/I0 is enlarged by 3.15 times compared with that of the HfO2 surface without O2 plasma treatment. In addition, real-time and label-free detection of sulfadiazine with high sensitivity and specific recognition is successfully achieved using the SiNW FET biosensor with the optimized process. And a 10 pg⋅mL−1 limit of detection (LOD) is achieved for the SiNW FET biosensor using O2 plasma treatment on an ultrathin HfO2 mentioned above. The proposed O2 plasma treatment on HfO2 provides an effective solution for future FET biosensors coated with high-к dielectrics.

Thermal Resistance in ALD Grown Dielectric Thin Films

The need for increased control of layer thickness and uniformity as device dimensions shrink has spurred increased use of atomic layer deposition (ALD) for thin film growth. The ability to deposit high dielectric constant (high-k) films via ALD has allowed for their widespread use in a swath of optical, optoelectronic, and electronic devices, including integration into CMOS compatible platforms. As the thickness of these films is reduced, the interfacial thermal resistance can dictate the overall thermal resistance of the material stack compared to the resistance due to the finite dielectric layer thickness. In this study, time domain thermoreflectance is used to interrogate the thermal conductivity and the thermal boundary resistance of routinely used high-k dielectrics, aluminum oxide, hafnium oxide, and titanium oxide films ALD grown on silicon, as well as films of hafnium zirconium oxide, which has demonstrated potential for applications in energy storage devices as well as electronic memory devices and architectures.

Thermal conductivity and thermal boundary resistance of atomic layer deposited high-k dielectric aluminum oxide, hafnium oxide, and titanium oxide thin films on silicon

The need for increased control of layer thickness and uniformity as device dimensions shrink has spurred increased use of atomic layer deposition (ALD) for thin film growth. The ability to deposit high dielectric constant (high-k) films via ALD has allowed for their widespread use in a swath of optical, optoelectronic, and electronic devices, including integration into CMOS compatible platforms. As the thickness of these dielectric layers is reduced, the interfacial thermal resistance can dictate the overall thermal resistance of the material stack compared to the resistance due to the finite dielectric layer thickness. Time domain thermoreflectance is used to interrogate both the thermal conductivity and the thermal boundary resistance of aluminum oxide, hafnium oxide, and titanium oxide films on silicon. We calculate a representative design map of effective thermal resistances, including those of the dielectric layers and boundary resistances, as a function of dielectric layer thickness, which will be of great importance in predicting the thermal resistances of current and future devices.

Determination of band offset in InP/YSZ hetero-junction by X-ray photoelectron spectroscopy

Y-stabilized ZrO2 (YSZ) was one of the familiar high dielectric constant films used in InP field effect transistors. However, the structure and optical properties of YSZ film deposited on InP substrate were rarely reported. The band offsets in InP/YSZ hetero-junction was an important parameter, which had not been measured. In the work, YSZ films were deposited on InP substrates by sputtering. The optical properties and structures of YSZ films and InP/YSZ interface were characterized. X-ray photoelectron spectroscopy was used to measure the energy discontinuity in the valence band of the InP/YSZ hetero-structure. A value of 1.4 eV was obtained with In 3d5 as the reference energy level. With the band gap of 5.8 eV for YSZ and 1.3 eV for InP, this indicated a conduction band offset of 3.1 eV in the system.

Synthesis and properties of a high dielectric constant copolymer of a copper phthalocyanine oligomer grafted to amino-capped polyimide

A novel high dielectric constant all-organic polymer film of a copper phthalocyanine oligomer grafted to polyimide (CuPc–PI) was successfully synthesized via a polycondensation between a copper phthalocyanine anhydride oligomer and amino-capped polyamic acid, followed by thermal treatment.

Low Temperature Processed Organic Tfts with Solution-Processable Al2O3 Gate Insulator Using Hydrogen Peroxide

Organic semiconductors are considered as a replacement for amorphous silicon in thin-film transistor (TFT) applications, since they have shown comparable electrical properties and potential advantages for their compatibility with plastic substrates. However, the high operating voltages of these TFTs still need to be reduced for any practical application. Among dielectric materials, aluminum oxide (Al2O3) appears to be promising due to its high dielectric constant, its robustness and its possibility to be prepared on different type of substrates under easy process. However, high quality and high dielectric constant films generally require annealing temperature above 400 oC, which is not suitable for high-throughput and flexible electronic devices. In this study, we fabricated the bottom-gate and top-contact organic TFTs on glass substrate. Al gate electrode was deposited by thermal evaporation while Al2O3 thin films, used as gate insulators, were grown by spin coating. Employing hydrogen peroxide (H2O2) in the solution process helps reduce defects at the interface between channel and G/I through strong oxidation and minimize organic chemical-induced defects, such as pores, pin holes, and organic residues, through decomposing organic chemicals at low temperature. The growth of the Al2O3 thin films with H2O2 was studied with various annealing temperatures from 100 ~ 300 oC and solution concentration of 0.1 ~ 1 M. Pentacene was evaporated through shadow mask at a rate of 0.3 Å/s to form a 70 nm thick active layer. Gold source/drain (S/D) electrodes (100 nm) were patterned using shadow mask on the pentacene layer. The performance of the solution processed Al2O3 based TFT was validated using capacitance-voltage and current-voltage analysis.

High Dielectric Constant ZrO2 Films by Atomic Layer Deposition Technique on Germanium Substrates

Germanium has been reconsidered as a potential substitute channel material for high-performance MOSFETs due to its intrinsic high mobilities for both electrons (3900 cm2 s-1V-1) and holes (1900 cm2 s-1V-1). In the present work we have fabricated Pt/Ti metal bilayered ALD-ZrO 2/n-Ge based MOS capacitors. The ZrO2 thin film was deposited on n-Ge (100) substrates by using ZrEMA and oxygen precursors at 300 °C in a PEALD system. The Pt/Ti bilayer metallization was carried out using e-beam evaporation and PMA using a RTA system at 350 °C in the forming gas. The thickness of the ZrO2 gate stack was measured to be 3.61 nm using an ellipsometer. The electrical study was done by analyzing capacitance voltage and current voltage measurements. The flat-band shift was found to be 0.22 V, Qeff was 3.55×1012 cm-2 and Dit was 8.53×1012 cm-2 eV-1. Current voltage characteristics have been analyzed to know the conduction mechanism in fabricated MOS devices.

High dielectric constant composite films with high strength, toughness and thermal stability

The dielectric properties of composite films comprising poly(ether ether ketone) (PEEK) and multiwalled carbon nanotubes (MWCNTs) wrapped in poly(ether sulphone) were investigated. These wrapped-MWCNT–PEEK composite films were fabricated through melt blending and subsequent melt extrusion. At low frequencies, the dielectric constant ( k) of the composite PEEK film with 0.68 vol%-wrapped MWCNTs increased with the frequency, with the value of k being as high as 367 at 103 Hz. The wrapped-MWCNT–PEEK composite films also exhibited superior mechanical and thermal properties. In particular, the tensile strength and elongation at break values of all the composite films were greater than 103 MPa and 170%, respectively, and their 5% weight loss temperatures were higher than 575°C. This was attributable to the high conductivity of the MWCNTs, the uniform dispersion of the wrapped MWCNTs in the PEEK matrix, the strong interfacial adhesion between the wrapped MWCNTs and the PEEK, and the processing method employed, namely, melt extrusion.

Synthesis, characterization and radiation damage studies of high-k dielectric (HfO2) films for MOS device applications

The current trend in miniaturization of metal oxide semiconductor devices needs high-k dielectric materials as gate dielectrics. Among all the high-k dielectric materials, HfO2 enticed the most attention, and it has already been introduced as a new gate dielectric by the semiconductor industry. High dielectric constant (HfO2) films (10 nm) were deposited on Si substrates using the e-beam evaporation technique. These samples were characterized by various structural and electrical characterization techniques. Rutherford backscattering spectrometry, X-ray reflectivity, and energy-dispersive X-ray analysis measurements were performed to determine the thickness and stoichiometry of these films. The results obtained from various measurements are found to be consistent with each other. These samples were further characterized by I–V (leakage current) and C–V measurements after depositing suitable metal contacts. A significant decrease in the leakage current and the corresponding increase in device capacitance are observed when these samples were annealed in oxygen atmosphere. Furthermore, we have studied the influence of gamma irradiation on the electrical properties of these films as a function of the irradiation dose. The observed increase in the leakage current accompanied by changes in various other parameters, such as accumulation capacitance, inversion capacitance, flat band voltage, mid-gap voltage, etc., indicates the presence of various types of defects in irradiated samples.