Al2O3 Dielectrics Research Articles

Improving bias stability of IGZO field-effect transistors through CF4 plasma treatment of Al2O3 dielectrics

In this study, the effects of the CF4 plasma treatment on the amorphous indium gallium zinc oxide (IGZO) material were explored. The electrical characteristics of the IGZO-based field-effect transistor (FET) were also thoroughly examined to analyze the influence of the plasma treatment. Excellent adhesion of the sol-gel-based IGZO semiconducting film was achieved owing to the strong dipole moment of the AlOxFy layer created by the surface treatment. In particular, X-ray photoelectron spectroscopy depth profiles and transmission electron microscopy electron energy loss spectroscopy analyses provided clear evidence that fluorine atoms diffused into the Al2O3 surface via the CF4 plasma treatment. The formation of an AlOxFy layer at the IGZO/Al2O3 interface is expected to be advantageous for reducing the interface trap density, thereby enhancing the critical transistor parameters. Additionally, the plasma-treated IGZO transistor demonstrated strong electrical bias stability under continuous gate bias stress conditions. Therefore, surface modification via CF4 plasma treatment is proposed to boost the stability and performance of the device, offering a straightforward approach for integrated thin-film transistor circuitry in advanced display applications.

Low-voltage organic field-effect transistors by using solution-processable high-κ inorganic-polymer hybrid dielectrics

Organic field-effect transistors (OFETs) incorporating hybrid high-κ inorganic Al2O3 and polymer dielectrics, including polyvinyl alcohol (PVA), polystyrene (PS), or polymethyl methacrylate (PMMA), through solution-processing techniques were fabricated. The analyses revealed that the high surface energy and hydrophilicity property of Al2O3 and PVA, and the relatively hydrophobic property of PS surface, hindered the performance of corresponding OFETs. The Al2O3/PMMA-based OFET achieved the optimized performance, with a threshold voltage of −2.7 V, a hole carrier mobility of 0.056 cm2/Vs, and a current on/off ratio of 1.0 × 104 at a low operating voltage of −5 V. Through analyzing the characteristics of leakage current, capacitance, contact resistance, and trap density of OFETs, we found that the PMMA-engaged films possessed the optimized electrical properties. The introduction of PMMA eliminated the interfacial trapping, thereby lowering the threshold voltage and enhancing the performance of the device. The COMSOL Multiphysics simulation was conducted to confirm the physical mechanism. The strategy of utilizing Al2O3/PMMA hybrid dielectric could simultaneously ensure the low operating voltage and good performance of OFET, while guaranteeing the low leakage current by the thick PMMA.

Effect of using MgO coating with multiple coatings on the optical properties of a five-layer stack

تم استخدام المادة العازلة MgO ذات معامل الانكسار العالي (H) 1.737 مع أربعة مواد عازلة BaF2 (فلوريد الباريوم) و Al2O3 (الألومينا) و GdF3 (فلوريد الجادولينيوم) و LaF3 اللانثانوم فلورايد ذوات معامل انكسار واطيء (L) 1.4825 و 1.5322 و 1.59 و 1.6056 على التوالي كطلاءات بصرية لخمس طبقات وللتصميمين الأول هو ((Glass/H/L/H/L/H والثاني (Glass/L/H/L/H/L) ، باستخدام برنامج MATLAB. تم حساب الخصائص البصرية (M، Rvis.، Rsol.، Tsol.) للطلاءات البصرية الأربعة المتكونة ، وذلك لمعرفة أي طلاء منها كفوء لتلوين زجاج الأنظمة الشمسية المستخدمة كواجهات للأبنية وأيها غير كفوء. تظهر النتائج أنه في التصميم الأول (Glass/H/L/H/L/H) للطبقات الخمس ، يوجد طلاءان فقط لهما كفاءة للتلوين ، وهما الطلاءان (MgO + BaF2) و (MgO + Al2O3) ، لأنهما يحققان القيم المطلوبة من عامل الجدارة (M) والانعكاسية المرئية Rvis. حيث ان القيم المطلوبة لقيم عامل الجدارة (M) و.Rvis والتي تجعل الطلاء كفوءاً للتلوين هي 6% و12% على التوالي ، ولهما قمة انعكاس منتظمة وحادة للتلوين في المنطقة المرئية. في التصميم الأول ، يتناسب معامل الانكسار عكسياً مع الخصائص البصرية للطلاء وبالتالي كفاءة تلوين الطلاء ، مما يعني أن طلاء (MgO + BaF2) أكثر كفاءة من طلاء (MgO + Al2O3) للتلوين. يعتبر التصميم الثاني (Glass/L/H/L/H/L) للطبقات الخمس غير كفوء للتلوين للطلاءات الأربعة ( (MgO + BaF2 ، (MgO+ Al2O3) ، (MgO + GdF3) ، MgO + LaF3)) لأنها لا تمتلك القيم المطلوبة من (M) و . Rvis

Electrical Stability of MOS Structures With AlON and Al₂O₃ Dielectrics Deposited on n- and p-Type GaN

Electrical Stability of MOS Structures With AlON and Al₂O₃ Dielectrics Deposited on n- and p-Type GaN

Design and Comparative Analysis of Ferroelectric Nanowire with Dielectric HfO2 and Al2O3 for Low-Power Applications

Design and Comparative Analysis of Ferroelectric Nanowire with Dielectric HfO2 and Al2O3 for Low-Power Applications

Hypoeutectic Liquid Metal Printing of 2D Indium Gallium Oxide Transistors.

2D native surface oxides formed on low melting temperature metals such as indium and gallium offer unique opportunities for fabricating high-performance flexible electronics and optoelectronics based on a new class of liquid metal printing (LMP). An inherent property of these Cabrera-Mott 2D oxides is their suboxide nature (e.g., In2O3-x), which leads high mobility LMP semiconductors to exhibit high electron concentrations (ne >1019cm-3) limiting electrostatic control. Binary alloying of the molten precursor can produce doped, ternary metal oxides such as In-X-O with enhanced electronic performance and greater bias-stress stability, though this approach demands a deeper understanding of the native oxides of alloys. This work presents an approach for hypoeutectic rapid LMP of crystalline InGaOx (IGO) at ultralow process temperatures (180°C) beyond the state of the art to fabricate transistors with 10X steeper subthreshold slope and high mobility (≈18cm2Vs-1). Detailed characterization of IGO crystallinity, composition, and morphology, as well as measurements of its electronic density of states (DOS), show the impact of Ga-doping and reveal the limits of doping induced amorphization from hypoeutectic precursors. The ultralow process temperatures and compatibility with high-k Al2O3 dielectrics shown here indicate potential for 2D IGO to drive low-power flexible transparent electronics.

Carrier gradient core-double shell structure with heterojunction transition layer for significantly enhancing dielectric properties

In this work, to prohibit the undesirable large dielectric loss and electric-field distortion of the conductive fillers/polymer with a high dielectric constant, TiO2 (TO) and Al2O3 (AO) shells were successively coated on the surface of amorphous carbon (C) to prepare the C@TO@AO core-double shell nanoparticles. This novel design of gradually varying the multilayer hierarchical interface achieved the gradient reduction of carrier concentration from the C core to the TO and AO layers. And the introduction of the multilayer hierarchical interface was advantageous to the enhancement of interface polarization. Moreover, the excellent integrated dielectric properties could be effectively achieved by adjusting the layer thickness and crystal structure of the TO layer. It was worth noting that the TO transition layer with anatase and rutile heterojunctions (HTO) had a significant enhancement in the dielectric constant of the composites induced by the strength of interfacial polarization and built-in electric field inside the HTO layer. Furthermore, the simulated electric field distribution inside the composites was further investigated to reveal the mechanism of enhanced dielectric properties. This work exerts important guiding significance for the reasonable structure design and the elaborate regulation of the shell micro-structures to improve the dielectric properties of composites.

Tailored plasmon polariton landscape in graphene/boron nitride patterned heterostructures

Surface plasmon polaritons (SPPs), which are electromagnetic modes representing collective oscillations of charge density coupled with photons, have been extensively studied in graphene. This has provided a solid foundation for understanding SPPs in 2D materials. However, the emergence of wafer-transfer techniques has led to the creation of various quasi-2D van der Waals heterostructures, highlighting certain gaps in our understanding of their optical properties in relation to SPPs. To address this, we analyzed electromagnetic modes in graphene/hexagonal-boron-nitride/graphene heterostructures on a dielectric Al2O3 substrate using the full ab initio RPA optical conductivity tensor. Our theoretical model was validated through comparison with recent experiments measuring evanescent in-phase Dirac and out-of-phase acoustic SPP branches. Furthermore, we investigate how the number of plasmon branches and their dispersion are sensitive to variables such as layer count and charge doping. Notably, we demonstrate that patterning of the topmost graphene into nanoribbons provides efficient Umklapp scattering of the bottommost Dirac plasmon polariton (DP) into the radiative region, resulting in the conversion of the DP into a robust infrared-active plasmon. Additionally, we show that the optical activity of the DP and its hybridization with inherent plasmon resonances in graphene nanoribbons are highly sensitive to the doping of both the topmost and bottommost graphene layers. By elucidating these optical characteristics, we aspire to catalyze further advancements and create new opportunities for innovative applications in photonics and optoelectronic integration.

Plasmonic metamaterial absorber for MWIR and LWIR bispectral microbolometers

Plasmonic metamaterial absorbers (PMAs) designed for multispectral imaging in the infrared (IR) with uncooled microbolometers are investigated. The study presents Fourier transform infrared spectroscopy (FTIR) measurements of PMAs consisting of metal-insulator-metal-stacks (MIM) with square-shaped micropatches as top metal layers. The measurements reveal high absorptances of 82% to 99% for distinct wavelengths within a range from 2 μm to 9.2 μm. The spectra are evaluated with respect to the lateral dimensions of the patches and to the refractive indices of the used dielectrics SiO2, Al2O3 and Ta2O5. Numerical simulations and analytical calculations of the TM010-mode using the transmission line model (TLM) for microstrip antennas show good qualitative agreement with the measurement results. Additionally, bispectral PMAs were fabricated consisting of fields of PMAs with two different patch sizes arranged in a chessboard pattern. The individual fields of this pattern correspond to microbolometers with 12 μm pitch in shape and size. Two distinct absorption maxima can be seen in the spectra measured by FTIR. The choice of materials, deposition methods and patterning processes is suitable for the integration into the existing Fraunhofer IMS's nanotube microbolometer technology to realize multispectral infrared imaging. The fabrication process is CMOS-compatible and carried out on 8-in. wafers.

The biological effect of the physical energy of plasma

Since the publication of the initial paper on atmospheric pressure plasma sterilization by Dr Laroussi in 1996, researchers have contributed to the field with an extensive number of papers on plasma medicine. However, these studies have primarily concentrated on the biological impacts of the chemical reactive components generated by plasma, specifically focusing on the effects of reactive oxygen and nitrogen species. Conversely, when plasma directly interacts with biological organisms, there are additional physical energies involved, such as electric fields, ultraviolet (UV)/vacuum ultraviolet (VUV) radiation, heat, etc., which may also play crucial roles in their interaction. This paper delves into this aspect by using the simplest bactericidal effect as a model for biological effects. Three dielectrics—Al2O3, quartz, and MgF2 glass—are employed to isolate the chemical active components, enabling the examination of the bactericidal effects of the electric field, UV, and VUV, respectively. The findings indicate that the plasma-induced electric field can induce irreversible electroporation, effectively eliminating bacteria at 27 kV cm−1. Notably, at a plasma-induced electric field of 40 kV cm−1, sterilization efficiency experiences a significant enhancement. The bactericidal effects of UV and VUV are closely linked to the choice of the plasma’s working gas. Specifically, when Ar is the working gas, the bactericidal effect of UV surpasses that of using only the plasma-induced electric field by two orders of magnitude, while using He results in only a one-order increase. Despite VUV radiation being considerably weaker than UV, its bactericidal effect remains substantial. In instances where He plasma is utilized, the addition of VUV doubles the bactericidal effect. In short, this paper pioneers the exploration of the biological effects of plasma’s physical energy, providing essential insights for the advancement of plasma medicine.

Enhancement of electrical performance in indium-zinc oxide thin-film transistors with HfO2/Al2O3 gate insulator deposited via low-temperature ALD

Several studies have been conducted on amorphous oxide semiconductor (AOS) thin-film transistors (TFTs) with the aim of applying them to the next-generation low-power displays. To improve the electrical performance of conventional AOS TFTs, which are known for their poor switching characteristics, we fabricated indium-zin oxide (IZO) TFTs with HfO2/Al2O3 gate insulator deposited via low-temperature atomic layer deposition (ALD). We optimized the electrical performance of the fabricated TFTs by varying the thickness of the IZO channel and Al2O3 insulator, respectively. Compared to the samples with a thermally grown 150 nm thick SiO2 gate insulator, the samples with a 10 nm thick IZO channel and a 10/70 nm thick HfO2/Al2O3 gate insulator exhibited the subthreshold swing of 0.24 V/dec, saturation carrier mobility of 7.49 cm2/V∙s and on–off current ratio of 1.09 × 107, which were improved by more than 47 %, 64 % and 5 times, respectively. Also, the threshold voltage shift in positive and negative bias stress conditions were improved to + 0.90 and – 1.75 V, respectively.

Matched printed carbon nanotube complementary metal-oxide-semiconductor (CMOS) devices for flexible circuits

The development of matched carbon nanotube (CNT) complementary metal-oxide-semiconductor (CMOS) devices still remains a challenge for flexible and low-power-dissipation circuits. In this study, we found a reliable technique to achieve matched CNT CMOS thin-film transistors (TFTs) for integrated circuits (IC) with low power consumption. The enhancement-mode p-type CNT TFTs were obtained using the low-work-function Al gate electrodes and ultrathin (10 nm) Al2O3 dielectrics, which exhibit the average field-effect mobility(μ) of 6.5 cm2V−1s−1, subthreshold swing (SS) down to 70–85 mV/dec and on/off ratio up to 106 at the low working voltages between −1.5 V and 0.5 V, as well the outstanding stability and mechanical flexibility after 10,000 cycles of bending. Then, by adjusting the aspect ratios of the TFT channels and selectively dropping the electron-doping inks into p-type CNT TFTs’ channels, matched n-type and p-type CNT TFTs were obtained. Finally, flexible printed CMOS inverters with high noise tolerance (84% of 1/2 VDD), high voltage gain (over 32), and low power consumption (down to 32.9 pW) were successfully constructed, owing to the work style of CMOS circuits and electrically symmetrical n-type and p-type TFTs. Furthermore, good-performance NAND and NOR gates have been demonstrated. This work can effectively resolve the leakage current issue of flexible carbon-based electronics with the ultra-thin dielectrics by optimizing the conductive ink formula and printing technology.

Co‐sputtering of A Thin Film Broadband Absorber Based on Self‐Organized Plasmonic Cu Nanoparticles

AbstractThe efficient conversion of solar energy to heat is a prime challenge for solar thermal absorbers, and various material classes and device concepts are discussed. One exciting class of solar thermal absorbers are plasmonic broadband absorbers that rely on light absorption thanks to plasmonic resonances sustained in metallic nanoparticles. This work focuses on Cu/Al2O3 plasmonic absorbers, which consist of a thin film stack of a metallic Cu‐mirror, a dielectric Al2O3 spacer, and an Al2O3/Cu‐nanoparticle nanocomposite. This work explores two preparation routes for the Al2O3/Cu‐nanoparticle nanocomposite, which rely on the self‐organization of Cu nanoparticles from sputtered atoms, either in the gas phase (i.e., via gas aggregation source) or on the thin film surface (i.e., via simultaneous co‐sputtering). While in either case, Cu‐Al2O3‐Al2O3/Cu absorbers with a low reflectivity over a broad wavelength regime are obtained, the simultaneous co‐sputtering approach enabled better control over the film roughness and showed excellent agreement with dedicated simulations of the optical properties of the plasmonic absorber using a multi‐scale modeling approach. Upon variation of the thickness and filling factor of the Al2O3/Cu nanocomposite layer, the optical properties of the plasmonic absorbers are tailored, reaching an integrated reflectance down to 0.17 (from 250 to 1600 nm).

Morphological Control of thin Dielectric Films Obtained by RF Magnetron Sputtering and Thermal Evaporation in Vacuum

Thin dielectric Al2O3 and SrO films obtained by thermal evaporation in vacuum, as well as Si3N4 and SiO2 films obtained by RF magnetron sputtering, were studied by atomic force microscopy. The metric and fractal parameters of dielectric layers are estimated using the Gwyddion graphical program for analyzing data from scanning probe microscopy. It has been established that the maximum values of the fractal dimension are characteristic of aluminum oxide films with a thickness of 0.5 μm, while the smallest root-mean-square roughness is characteristic of strontium oxide films. The prospects for using the analyzed dielectric films as insulating layer of sensitive elements of strain gauge pressure sensors with a conductive elastic element are demonstrated.

Simulation of Silicon FETs with a Fully Enclosed Gate with a High-k Gate Dielectric

The electrical and physical characteristics of a cylindrical silicon field-effect nanotransistor (FET) with a fully enclosed gate with Al2O3 and HfO2 gate oxide dielectrics are discussed. The numerical simulation results show that the use of high k dielectrics has a noticeable effect on all the main characteristics of the tran-sistor compared to silicon oxide. It follows from the data obtained that, when scaling, the degree of degradation of the electrical and physical characteristics of the transistor is correlated with the level of k: it decreases with the growth of k. This is due to the fact that the decrease in the effect of the gate on the characteristics of the transistor structure, especially in the subthreshold region, is partially compensated by the use of dielectrics with a high k.

Self‐Regulating Process for Large Area Nanowire Solar Cells Based on Thin Polycrystalline Silicon Films Prepared on Glass

Herein, a process for the large‐area passivating and contacting of nanowire‐based solar cells is demonstrated. The nanowire‐based solar cells are prepared on layered laser crystallization (LLC) polycrystalline silicon (pc‐Si) thin films with thickness less than 2 μm. It is demonstrated that the space between the nanowires can be filled with a passivating dielectrics Al2O3 layer, and the nanowire tips can be exposed by a self‐regulating selective etching of the Al2O3 deposited on the tips and that on the sidewalls. The exposed tips of the nanowires can be connected by a transparent conducting aluminum‐doped zinc oxide (Al:ZnO or AZO) layer deposited by atomic layer deposition (ALD). The laser beam‐induced current mapping (LBIC) demonstrates that the current density can increase up to 63% at 633 nm due to light trapping and the superior passivation of the nanowires with an thin pc‐Si film of only 1.73 μm.

Rational selection of the oxygen source for atomic layer deposition Al2O3 insulators

Insulating gate dielectric is an important component of thin film transistors (TFT) and non-volatile memories, whose properties directly affect the electrical performance of the devices. In this study, the Al2O3 insulators were prepared by atomic layer deposition (ALD) using different oxygen sources and their properties were systematically studied. Based on the two-step oxidation method (H2O + O3), the Al2O3 thin films exhibited a small gate leakage current and a big breakdown field of 9 MV/cm. However, the use of the O3 increased the C-related impurities causing a large sweep hysteresis voltage of the TFTs, i.e., 8.65 V and 4.66 V for that with Al2O3 (O3) and Al2O3 (H2O + O3), respectively. Attributed to a small amount of impurities in the Al2O3 (H2O) insulators as well as the appropriate amount of Al element diffusion at the Al2O3/ZnO interface, the TFTs using Al2O3 (H2O) as insulators presented a high mobility of 36.1 cm2V−2s−1, a subthreshold swing of 0.25 V/dec and a small sweep hysteresis voltage of 0.42 V. Therefore, the properties of the ALD-Al2O3 films can be easily controlled by changing the type of the oxidizer. The Al2O3 thin films with H2O as oxidant can be used as the insulators of the TFTs, while the Al2O3 thin films based on O3 have great potential as the charge trap layer of the memories.

High temperature stability of H-diamond high frequency MOSFET with 300°C grown Al2O3 dielectric

The high frequency H-diamond metal-oxide-semiconductor field effect transistors (MOSFETs) were fabricated on single diamond substrate using 300°C ALD grown Al2O3 as gate dielectric and passivation layer. The devices gate length, gate/drain spacing and dielectric thickness are 100 nm, 2 μm, and 10 nm, respectively. The direct-current and frequency characteristics were investigated. The device shows a maximum saturation drain current of −492.6 mA/mm and gm of 135.2 mS/mm. The device shows good high temperature working performance, and the maximum saturation drain current only has a little decreasing of 7.6%. at 200°C. In addition, the device exhibits a maximum cut-off frequency of 36.2 GHz and maximum oscillation frequency of 70.5 GHz. The transient drain current response measurement indicates that the drain current can follow the changing of gate voltage at the frequency of 1 MHz. These results indicate that the Al2O3 dielectric is suitable for using in high frequency or the high-speed switching devices.

Simulation of a plasmonic sensor using kinetic theory of plasma with the Vlasov equation in MATLAB

This research proposes a mathematical model for a plasmonic sensor using kinetic theory of plasma with the Vlasov equation. A nanoantenna cavity of a plasmonic material is driven by an input electromagnetic wave, which changes the charge density and current flow in the cavity, resulting in a change in the Fermi distribution function of the charged particles. The results are achieved in terms of current density and conductivity by solving the Boltzmann transport equation, Maxwell’s equations, and Taylor series expansion in terms of perturbed electric fields with linear integro differential equations. The results are simulated using MATLAB. The changes in current density and conductivity are validated by experimental analysis of graphene plasmonic material using patch antenna with the dielectric substrates SiO2 and Al2O3. By varying the applied electric fields, current changes at the output of the plasmonic antenna are analyzed using signal-processing techniques. Wavelet transforms are used to find the space-scale behavior of the output signals, such as current density variation, voltage variation, and susceptibility change with sub-band coding techniques in terms of wavelet coefficients.

Carrier Recombination Dynamics of Surface-Passivated Epitaxial (100)Ge, (110)Ge, and (111)Ge Layers by Atomic Layer Deposited Al2O3

Germanium (Ge) and its heterostructures with compound semiconductors offer a unique optoelectronic functionality due to its pseudo-bandgap nature, that can be transformed to a direct bandgap material by providing strain and/or mixing with tin. Moreover, two crystal surfaces, (100)Ge and (110)Ge, that are technologically important for ultralow power fin or nanosheet transistors, could offer unprecedented properties with reduced surface defects after passivating these surfaces by atomic layer deposited (ALD) dielectrics. In this work, the crystallographically oriented epitaxial Ge/AlAs heterostructures were grown and passivated with ALD Al2O3 dielectrics, and the microwave photoconductive decay (μ-PCD) technique was employed to evaluate carrier lifetimes at room temperature. The X-ray photoelectron spectroscopy analysis reveals no role of orientation effect in the quality of the ALD Al2O3 dielectric on oriented Ge layers. The carrier lifetimes measured using the μ-PCD technique were benchmarked against unpassivated Ge/AlAs heterostructures. Excitation wavelengths of 1500 and 1800 nm with an estimated injection level of ∼1013 cm–3 were selected to measure the orientation-specific carrier lifetimes. The carrier lifetime was increased from 390 ns to 565 ns for (100)Ge and from 260 ns to 440 ns for (110)Ge orientations with passivation, whereas the carrier lifetime is almost unchanged for (111)Ge after passivation. This behavior indicates a strong dependence of the measured lifetime on surface orientation and surface passivation. The observed increase (>1.5×) in lifetime with Al2O3-passivated (100)Ge and (110)Ge surfaces is due to the lower surface recombination velocity compared to unpassivated Ge/AlAs heterostructures. The enhancement of carrier lifetime from passivated Ge/AlAs heterostructures with (100)Ge and (110)Ge surface orientations offers a path for the development of nanoscale transistors due to the reduced interface state density.