Low-temperature Fabrication Process Research Articles

Hydrophilic Ligand Exchange Induces Improved Upconversion Nanoparticle Incorporation in Dye-Sensitized Solar Cells with Efficiency Exceeding 8% in a Low-Temperature Fabrication Process

Hydrophilic Ligand Exchange Induces Improved Upconversion Nanoparticle Incorporation in Dye-Sensitized Solar Cells with Efficiency Exceeding 8% in a Low-Temperature Fabrication Process

Head-to-Head Comparison of Acoustic Properties of Lead-Free and PZT-Based HIFU Transducers Operating at 12 MHz.

A direct comparison of performance and acoustic properties of high-intensity focused ultrasonic transducers utilizing lead-free (sodium bismuth titanate-NBT) and lead-based (lead zirconate titanate-PZT) piezoceramics is discussed. All transducers operate at 12 MHz at third harmonic frequency, having an outer diameter of 20 mm, a central hole of 5 mm in diameter, and a radius of curvature of 15 mm. The electroacoustic efficiency determined by a radiation force balance is evaluated in a range of input power levels up to 15 W. Schlieren tomography as well as hydrophone measurements are used for evaluation of the acoustic field distribution. It is found that the average electroacoustic efficiency of NBT-based transducers is approximately 40%, while it is around 80% in the PZT-based devices. NBT devices show significantly higher inhomogeneity of the acoustic field under schlieren tomography compared to PZT devices. From pressure measurements in the prefocal plane, it was found that the inhomogeneity could be attributed to depoling of significant areas of the NBT piezo-component during the fabrication process. In conclusion, PZT-based devices performed significantly better than those using lead-free material. However, the NBT devices show promise for this application and their electroacoustic efficiency as well as the uniformity of the acoustic field could be improved by employing a low-temperature fabrication process or repoling after processing.

(Invited) Fabrication Technique of Ferroelectric HfxZr1−XO2 Thin Films Using ALD-ZrO2 Nucleation Layers

Ferroelectric HfxZr1−xO2 (HZO) thin films have attracted considerable attention towards high-density and low-power ferroelectric memory devices of ferroelectric random access memory (FeRAM) and ferroelectric field-effect transistors (FeFETs) [1]. To obtain ferroelectric orthorhombic (O) phase of HZO films, several techniques have been investigated, such as the TiN stressor layer technique [2] and controlled annealing conditions [3]. On the other hand, we pay attention to the ZrO2 nucleation layer technique because ZrO2 films deposited by atomic layer deposition (ALD) method formed a nanocrystalline structure and consisted dominantly of O, tetragonal (T), and cubic (C) phases, whose lattice constants are considerably close to that of ferroelectric O phase for HfO2 [4]. In this paper, we report the crystallinity and ferroelectricity of HZO films fabricated using the ZrO2 nucleation layer technique for metal-ferroelectric-metal (MFM) and metal-ferroelectric-semiconductor (MFS) capacitors.First, four types of MFM capacitors of TiN/HZO/TiN (MFM w/o), TiN/HZO/bottom-ZrO2/TiN (MFM B-ZrO2), TiN/top-ZrO2/HZO/TiN (MFM T-ZrO2), and TiN/top-ZrO2/HZO/bottom-ZrO2/TiN (MFM D-ZrO2) were systematically investigated for the FeRAM applications [5]. The thicknesses of the ALD-grown HZO and ZrO2 films were 10 and 2 nm, respectively. The post-deposition annealing was performed at 600°C. The remanent polarization (2P r = P r + − P r −) of the MFM capacitors increased in the following order: MFM w/o (12 µC/cm2) < MFM B-ZrO2 (15 µC/cm2) < MFM T-ZrO2 (23 µC/cm2) < MFM D-ZrO2 (29 µC/cm2), while all capacitors showed almost the same coercive electric field (E c) value of around 1.2 MV/cm. Therefore, maximum 2P rvalue of the MFM capacitor was obtained using the top- and bottom-ZrO2 nucleation layers. For the MFM capacitors with ZrO2 nucleation layers, epitaxial-like grain growth of the HZO film occurred on the nanocrystalline top- and bottom-ZrO2 layers. Moreover, the relative ratio of O/T/C phases in the ferroelectric film, which was estimated using the peak area ratio of O(111)/T(101)/C(111)/{M(−111)+ O(111)/T(101)/C(111)+M(111)}, increased in the following order: MFM w/o < MFM B-ZrO2 < MFM T-ZrO2 < MFM D-ZrO2. Therefore, the top- and bottom-ZrO2 layers play an important role as nucleation layers for the crystallization of the HZO film, resulting in a larger relative ratio of O/T/C phases in the ferroelectric film compared to w/o. Moreover, these results indicate that the top-ZrO2 layer was more effective to form the ferroelectric phase compared to the bottom-ZrO2 layer.Next, two types of MFS capacitors of TiN/HZO/Si (MFS w/o) and TiN/top-ZrO2/HZO/Si (MFS T-ZrO2) were fabricated by low-temperature processes at 300°C of ALD and post-metallization annealing (PMA) for the FeFET applications [6]. The thicknesses of both HZO and ZrO2 films were 10 nm. Both MFS w/o and MFS T-ZrO2 were found to form an extremely thin SiO2 interfacial layer with a thickness of one or two monolayers between the HZO film and Si substrate due to a low temperature fabrication process of 300°C. The HZO film of the MFS T-ZrO2 formed O/T/C phases even with a low thermal budget of 300°C, while that of the MFS w/o had an amorphous structure. This result is attributed to the beneficial role of the nanocrystalline top-ZrO2 nucleation layer for the crystallization of an amorphous HZO film during the PMA process. Therefore, a higher 2P r value of 15 µC/cm2 was obtained for the MFS T-ZrO2 than that (2.2 µC/cm2) for the MFS w/o. Moreover, the endurance properties of the MFS T-ZrO2 were free from the wake-up effect and exhibited less degradation of switching polarization (P sw). This could be attributed to the insertion of a ZrO2 film at the TiN/HZO interface, which promoted the preferential formation of the ferroelectric orthorhombic phase and prevent the formation of oxygen vacancies at the ZrO2/HZO interface. Thus, we concluded that superior ferroelectricity with wake-up free properties and higher fatigue resistance of HZO-based MFS capacitors were achieved by using the ZrO2 nucleation layer technique.These results suggest that the fabrication technique of ferroelectric HZO films using nanocrystalline ALD-ZrO2 nucleation layers is one of the promising processes for the next-generation non-volatile memory device applications.This work was supported by JSPS KAKENHI (Nos. JP21J01667, JP20H02189, and JP18J22998) and MEXT Leading Initiative for Excellent Young Researchers (No. JPMXS0320220213).[1] T. Mikolajick et al., J. Appl. Phys. 129, 100901 (2021).[2] S. J. Kim, et al., Appl. Phys. Lett. 111, 242901 (2017).[3] S. Migita et al., Jpn. J. Appl. Phys. 58, SBBA07 (2019).[4] T. Onaya et. al., Appl. Phys. Express. 10, 081501 (2017).[5] T. Onaya et al., APL Mater. 7, 061107 (2019).[6] T. Onaya et al., APL Mater. 10, 051110 (2022).

Low temperature, highly stable ZnO thin-film transistors

A low-temperature and straightforward fabrication process for ZnO thin-film transistors (TFTs) with near-zero aging and negligible instability enabled by using an ultrathin oxide as a top-passivation layer is demonstrated. The process features bottom-gate top-contacts ZnO TFTs with ultrathin HfO2 or Al2O3 as passivation layers on top of the TFT followed by post-fabrication annealing (PFA). Devices with ultra-thin capping films of Al2O3 followed by a 150 °C PFA show threshold voltage shift (ΔVTH) of <1% after bias stress and negligible shift after aging. The devices show saturation threshold voltage (VTH-SAT) of 2.70 V, saturation mobilities larger than 10 cm2/V·s, and current ION/IOFF ratios >106. On the contrary, devices without nanofilm show similar performance to those with Al2O3 but show more considerable instability to aging and bias stress (ΔVTH > 5%). Also, devices with HfO2 as a capping layer shows severe instability (ΔVTH > 40%). A degradation mechanism to explain the improved aging and reliability performance is also discussed.

Additively Manufactured Flexible On-Package Phased Antenna Arrays With Integrated Microfluidic Cooling Channels for 5G/mmWave System-on-Package Designs

A fully additively manufactured flexible reconfigurable on-package antenna array with an integrated microfluidic cooling channel is introduced. The proposed design is a multilayer topology that can be easily embedded within flexible hybrid electronics (FHE) packages, utilizing 3-D printing and inkjet printing technologies. A novel 2.5-D ultra-wideband (UWB) antenna array operating from 24 to 40 GHz was designed and fabricated, and a beamformer IC was integrated with the inkjet-printed antenna array through room-temperature conductive silver paste as a proof-of-concept demonstration. The microfluidic channel attached to the on-package antenna array was stereolithography (SLA) printed using Flex80A resin from Formlabs. The measured radiation pattern of the integrated package showed a 10.09 dBi maximum realized gain with beam steering range from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 37 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> to 37 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> . The temperature change of the IC was also monitored, and the results showed a 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> F drop in 5 min. This low-cost and low-temperature fabrication process using additive manufacturing can be effectively applied to many 3-D printed materials that are sensitive to thermal treatment, as to next-generation multichip module (MCM) integration on flexible materials for 5G/mmWave system-on-package designs.

Monolithic Three-Dimensional Integration of Carbon Nanotube Circuits and Sensors for Smart Sensing Chips.

Semiconducting carbon nanotube (CNT) film is a promising material for constructing high-performance complementary metal-oxide-semiconductor (CMOS) integrated circuits (ICs) and highly sensitive field-effect transistor (FET) bio/chemical sensors. Moreover, CNT logic transistors and sensors can be integrated through a compatible low-temperature fabrication process, providing enough thermal budget to construct monolithic three-dimensional (M3D) systems for smart sensors. However, an M3D sensing chip based on CNT film has not yet been demonstrated. In this work, we develop M3D technology to fabricate CNT CMOS ICs and CNT sensor arrays in two different layers; then, we demonstrate a preliminary M3D sensing system comprising CNT CMOS interfacing ICs in the bottom layer and CNT sensors in the upper layer through interlayer vias as links. As a typical example, a highly sensitive hydrogen sensing IC has been demonstrated to perform in situ sensing and processing functions through upper-layer FET-based hydrogen sensors exposed to the environment and bottom-layer CNT CMOS voltage-controlled oscillator (VCO) interfacing circuits. The M3D CNT sensing ICs convert hydrogen concentration information (8-128 ppm) to digital frequency information (0.78-1.11 GHz) with a sensitivity of 2.75 MHz/ppm. M3D sensing technology is expected to provide a universal sensing system for future smart sensing chips, including multitarget detection and ultralow power sensors.

SYSTEMATIC FIELD APPLICATION OF ENHANCED PLASMONIC ORGANIC SOLAR CELL: AN OVERVIEW

Organic solar cells (OSCs) have attracted considerable research interest due to their satisfactory properties including light-weight, low-cost, low-temperature fabrication process, semi-transparency and mechanical flexibility. Recent advances in OSCs have demonstrated above 10% efficiency in single-junction cells, indicating a strong competitiveness when compared with the commercial silicon photovoltaic system. To obtain maximum efficiency, there is a trade-off between light absorption and charge transport efficiency. Plasmonic light-trapping scheme is a feasible approach to maximize light absorption while maintaining charge transport efficiency. To give an overall look at the plasmonic organic solar cells, we review the recent progress on plasmonic-enhanced OSCs devices by integration with metal plasmonic enhancers, including both experimental and theoretical works. Among the varying proposed plasmonic structures, nano particles are preferable because of their strong scattering properties, particle size tunability, shape, and dielectric environment. In addition, design approaches based on plasmonics can be used to improve absorption in solar cells, permitting a considerable reduction in the physical thickness of solar cell absorber layers, and yielding novel options for solar-cell designs. Also, the simplicity in plasmonics preparation and integration methods is easily compatible with the standard solar cell fabrication process.

Recent progress of inverted organic-inorganic halide perovskite solar cells

In recent years, inverted perovskite solar cells (IPSCs) have attracted significant attention due to their low-temperature and cost-effective fabrication processes, hysteresis-free properties, excellent stability, and wide application. The efficiency gap between IPSCs and regular structures has shrunk to less than 1%. Over the past few years, IPSC research has mainly focused on optimizing power conversion efficiency to accelerate the development of IPSCs. This review provides an overview of recent improvements in the efficiency of IPSCs, including interface engineering and novel film production techniques to overcome critical obstacles. Tandem and integrated applications of IPSCs are also summarized. Furthermore, prospects for further development of IPSCs are discussed, including the development of new materials, methods, and device structures for novel IPSCs to meet the requirements of commercialization.

Low energy repair of co-continuous metal-ceramic composites using electrodeposition

The concept of self-healing materials, mainly inspired from biological systems, in the last several decades has been pursued toward fully autonomous materials and structures. Self-healing of polymers (extensively) and metals (to much less extent) have been demonstrated, however, there are no such reports for metal-ceramic composites. Metal-ceramic composites are technologically significant as structural and functional materials and are among the most expensive materials to manufacture and repair. Hence, technologies for self-healing metal-ceramic composites are of paramount importance. Here, we demonstrate a concept to fabricate and heal co-continuous metal-ceramic composites at room temperature. The composites are fabricated by infiltration of metal (here copper) into a porous alumina preform (fabricated by freeze-casting) through electroplating; a low-temperature and low-cost (by ∼60-times lower cost compared to traditional molten metal infiltration) process for fabrication of such composites. Additionally, the same electroplating process is demonstrated for healing damages such as grooves and cracks in the original composite, such that the healed composite recovers its strength by more than 80%. Such technology may be expanded toward fully autonomous self-healing structures.

Modeling the path to >30% power conversion efficiency in perovskite solar cells with plasmonic nanoparticles.

Mixed organic-inorganic halide perovskite solar cells (PSCs) are a promising technology with increasing power conversion efficiency (PCE), low-cost material constituents, simple scalability, and a low-temperature solution fabrication process. Recent developments have seen energy conversion efficiencies increase from 3.8% to over 20%. However, to further improve PCE and reach the target efficiency of over 30%, light absorption through plasmonic nanostructures is a promising approach. In this work, we present a thorough quantitative analysis of the absorption spectrum of a methylammonium lead iodide (CH3NH3PbI3) perovskite solar cell using a nanoparticle (NP) array. Our multiphysics simulations using finite element methods (FEM) show that an array of Au nanospheres can increase average absorption >45%, compared to only 27.08% for the baseline structure without any NPs. Furthermore, we investigate the combined effect of engineered enhanced absorption on electrical and optical solar cell performance parameters using the one-dimensional solar cell capacitance software (SCAPS 1-D), which shows a PCE of ∼30.4%, significantly higher than the PCE of ∼21% for cells without NPs. Our findings demonstrate the potential of plasmonic perovskite research for next-generation optoelectronic technologies.

Microwave plasma-assisted reactive HiPIMS of InN films: Plasma environment and material characterisation

This work focuses on the low temperature fabrication process of InN thin films via microwave plasma-assisted reactive high power impulse magnetron sputtering (MAR-HiPIMS). The influence of microwave plasma on the HiPIMS discharge process at various nitrogen flows and microwave powers was monitored and characterised through in situ diagnostics, including following HiPIMS I(V,t) curves, optical emission spectroscopy (OES), as well as performing time-resolved Langmuir probe and time-of-flight mass spectroscopy (ToF-MS) measurements. This was followed by the deposition of InN films via standard reactive HiPIMS (reference sample) and MAR-HiPIMS and their characterisation via X-ray diffraction (XRD), reflectometry (XRR), as well as scanning and transmission electron microscopy (SEM, TEM). It was found that the microwave plasma facilitates the dissociation/activation of nitrogen species and supplies seed electrons to the magnetron discharge plasma. Furthermore, the energy of the incoming ions was determined via ToF-MS, and it was possible to identify their plasma origin and temporal behaviour. The produced R-HiPIMS sample was highly metallic, with no nitride phase detected. The MAR-HiPMS film, however, was stoichiometric and exhibited (0002) direction texturing, with an optical bandgap of approx. 1.5 eV, electron concentration of 2.72 × 1020 cm−3 and electron mobility of 7.16 cm2V−1 s−1 (in the range for polycrystalline InN).

Low temperature, area-selective atomic layer deposition of NiO and Ni

Nickel and nickel oxide are utilized within various device heterostructures for chemical sensing, solar cells, batteries, etc. Recently, the rising interest in realizing low-cost, flexible electronics to enable ubiquitous sensors and solar panels, next-generation displays, and improved human-machine interfaces has driven interest in the development of low-temperature fabrication processes for the integration of inorganic devices with polymeric substrates. Here, we report the low-temperature area-selective atomic layer deposition of Ni by reduction of preformed NiO. Area-selective deposition of NiO is performed at 100 °C using bis(N,N'-di-tert-butylacetamidinato) nickel(II) and water on SiO2 and polystyrene. NiO grows two-dimensionally and without nucleation delay on oxide substrates but not on SiNx or polystyrene, which require surface treatments to promote NiO nucleation. Additionally, prepatterned sp2 carbon-rich resists inhibit the nucleation of NiO, and in this way, carbon-free NiO may be patterned. Subsequent thermal reduction of NiO to Ni was investigated using H2 (50–80 m Torr) and thermally generated H-atoms (3 × 10−5 Torr chamber pressure). Due to the relatively high free surface energy of Ni metal, Ni films undergo dewetting at elevated temperatures when solid-state transport is enabled. Reduction of NiO to Ni is demonstrated at 100 °C and below using atomic hydrogen. In situ x-ray photoelectron spectroscopy is used to determine oxidation state and ex situ x-ray reflectivity and atomic force microscopy are used to probe the film thickness and surface morphology, respectively.

Microwave-Assisted Annealing Method for Low-Temperature Fabrication of Amorphous Indium-Gallium-Zinc Oxide Thin-Film Transistors

Compared with conventional silicon-based semiconductors, amorphous oxide semiconductors present several advantages, including the possibility of room-temperature fabrication, excellent uniformity, high transmittance, and high electron mobility. Notably, the application of oxide semiconductors to flexible electronic devices requires a low-temperature fabrication process. However, for the realization of semiconductor characteristics and stable products, the fabrication process requires annealing at temperatures of 300 °C or higher. To address this, a low-temperature microwave annealing method, which improves the electrical characteristics of a transistor and reduces the production time compared with the conventional annealing method, is presented herein. Microwave annealing is a well-known method of annealing that minimizes the heat energy transferred to a substrate via instantaneous heat transfer through the vibrations of the lattice in the material during microwave irradiation and is suitable as a low-temperature annealing method. In this study, we evaluate the electrical characteristics of devices subjected to conventional annealing at 200 °C and 300 °C for 1 h and microwave annealing at 200 °C for 10 min. For the device subjected to microwave annealing at 200 °C for 10 min, the threshold voltage, current on/off ratio, subthreshold swing, and saturation mobility are 13.9 V, 1.14 × 105, 3.05 V/dec, and 4.23 cm2/V·s, respectively. These characteristic results are far superior to the characteristic results of the device subjected to conventional annealing at 200 °C for 1 h and are equivalent to those of the device treated at 300 °C for 1 h. Thus, this study develops a more effective annealing method, which facilitates low-temperature fabrication in a reduced period.

Solvent-Induced Crystallization Method for High-Performance and Long-Term Stability Flexible Perovskite Photodetectors

Herein, we report a novel solvent-induced fabrication method to synthesize a perovskite thin film on flexible substrates. The high-quality CH3NH3PbI3 (MAPbI3) thin film is successfully fabricated, which is applied to prepare the stable flexible photodetector (PD). Compared with the reported results, this method achieved a low-temperature and low-cost perovskite thin film fabrication process on a flexible substrate. The constructed MAPbI3 layer possesses the advantages of being highly crystalline, uniform, and compact in a large area. The flexible PD based on the as-prepared perovskite thin film exhibits excellent performance and long-term stability. The EQE and R of the flexible PDs reached 8 × 102% and 3.6 A/W, respectively. At the same time, the flexible PDs still showed superior stability and high performance after 15 days of continuous working. The presented high-quality perovskite thin-film fabrication method and high-performance flexible perovskite PDs are expected for application in the development of novel optoelectronic devices.

Vertically stacked multilayer atomic-layer-deposited sub-1-nm In2O3 field-effect transistors with back-end-of-line compatibility

In this work, we demonstrate vertically stacked multilayer sub-1-nm In2O3 field-effect transistors (FETs) with surrounding gate in a back-end-of-line (BEOL) compatible low-temperature fabrication process. A typical bottom-gated single layer In2O3 FET with maximum on-state current (ION) of 890 μA/μm at VDS = 0.8 V and an on/off ratio over 106 is achieved with a channel length (Lch) of 100 nm. The effects of HfO2 capping and O2 annealing are systematically studied, which is critical to realizing the multilayer FETs. Each atomically thin In2O3 channel layer with a thickness (TIO) of 0.9 nm is realized by atomic layer deposition (ALD) at 225 °C. Multilayer FETs with a number of In2O3 layers up to 4 and 1.2 nm-thick HfO2 between each individual layer are fabricated. An enhancement of on-state current (ION) from 183 μA in a single layer In2O3 FET to 339 μA in a 4 layer device with an on/off ratio of 3.4 × 104 is achieved, demonstrating the key advantage of the multilayer FETs to improve the current. Several critical features, such as large-area growth, high uniformity, high reproducibility, ultrathin body, flexibility, and BEOL compatibility, have turned ALD In2O3 into a noteworthy candidate for next-generation oxide semiconductor channel materials.

Modulation of Perovskite Grain Boundaries by Electron Donor-Acceptor Zwitterions R,R-Diphenylamino-phenyl-pyridinium-(CH2) n -sulfonates: All-Round Improvement on the Solar Cell Performance.

Inverted perovskite solar cells (PSCs) have attracted intense attention because of their insignificant hysteresis and low-temperature fabrication process. However, the efficiencies of inverted PSCs are still inferior to those of commercialized silicon solar cells. Also, the poor stability of PSCs is one of the major impedances to commercialization. Herein, we rationally designed and synthesized a new series of electron donor (R,R-diphenylamino) and acceptor (pyridimium-(CH2)n-sulfonates) zwitterions as a boundary modulator and systematically investigated their associated interface properties. Comprehensive physical and optoelectronic studies verify that these zwitterions provide a four-in-one functionality: balancing charge carrier transport, suppressing less-coordinated Pb2+ defects, enhancing moisture resistance, and reducing ion migration. Although each functionality may have been reported by specific passivating molecules, a strategy that simultaneously regulates the charge-transfer balance and three other functionalities has not yet been developed. The results are to make an omnidirectional improvement of PSCs. Among all zwitterions, 4-(4-(4-(di-(4-methoxylphenyl)amino)phenyl)propane-1-ium-1-yl)butane-1-sulfonate (OMeZC3) optimizes the balance hole/electron mobility ratio of perovskite to 0.91, and the corresponding PSCs demonstrate a high power conversion efficiency (PCE) of up to 23.15% free from hysteresis, standing out as one of the champion PSCs with an inverted structure. Importantly, the OMeZC3-modified PSC exhibits excellent long-term stability, maintaining almost its initial PCE after being stored at 80% relative humidity for 35 days.

Flexible Ceramic Film Sensors for Free-Form Devices.

Recent technological innovations, such as material printing techniques and surface functionalization, have significantly accelerated the development of new free-form sensors for next-generation flexible, wearable, and three-dimensional electronic devices. Ceramic film sensors, in particular, are in high demand for the production of reliable flexible devices. Various ceramic films can now be formed on plastic substrates through the development of low temperature fabrication processes for ceramic films, such as photocrystallization and transferring methods. Among flexible sensors, strain sensors for precise motion detection and photodetectors for biomonitoring have seen the most research development, but other fundamental sensors for temperature and humidity have also begun to grow. Recently, flexible gas and electrochemical sensors have attracted a lot of attention from a new real-time monitoring application that uses human breath and perspiration to accurately diagnose presymptomatic states. The development of a low-temperature fabrication process of ceramic film sensors and related components will complete the chemically stable and reliable free-form sensing devices by satisfying the demands that can only be addressed by flexible metal and organic components.

Design Automation and Test Solutions for Monolithic 3D ICs

Monolithic 3D (M3D) is an emerging heterogeneous integration technology that overcomes the limitations of the conventional through-silicon-via (TSV) and provides significant performance uplift and power reduction. However, the ultra-dense 3D interconnects impose significant challenges during physical design on how to best utilize them. Besides, the unique low-temperature fabrication process of M3D requires dedicated design-for-test mechanisms to verify the reliability of the chip. In this article, we provide an in-depth analysis on these design and test challenges in M3D. We also provide a comprehensive survey of the state-of-the-art solutions presented in the literature. This article encompasses all key steps on M3D physical design, including partitioning, placement, clock routing, and thermal analysis and optimization. In addition, we provide an in-depth analysis of various fault mechanisms, including M3D manufacturing defects, delay faults, and MIV (monolithic inter-tier via) faults. Our design-for-test solutions include test pattern generation for pre/post-bond testing, built-in-self-test, and test access architectures targeting M3D.

MORPHOLOGICAL AND PHYSICAL PROPERTIES OF ZnO NANOSTRUCTURES GROWN ON Sb-DOPED ZnO SEEDING FILMS ANNEALED UNDER DIFFERENT ATMOSPHERES

In this work, morphological and physical properties of pyramid-like ZnO nanostructures fabricated on Sb-doped ZnO seeding films annealed under different atmospheres are extensively studied. The Sb-doped ZnO seeding films were first prepared by sol–gel spin coating technique onto glass substrate then annealed in nitrogen, air and argon followed by low-temperature hydrothermal process for ZnO nanostructures fabrication. The morphological results exhibit the growth of pyramid-like ZnO nanostructure with increasing density of the ZnO nanostructures. The crystal structure shows pyramid-like ZnO wurtzite hexagonal growth along the c-axis without any impurity phase. The growth of pyramid-like ZnO nanostructures is due to the high growth rate of (002) plane. Photoluminescence spectra exhibit the near-band-edge of all samples while the red emission appears in ZnO nanostructures after the hydrothermal process due to the imperfection in the crystal. The reflectance of ZnO nanostructures covers the visible region with the absorption edge of 375[Formula: see text]nm. The calculation shows the relevant energy band gaps in the range of 3.26–3.28[Formula: see text]eV. The difference in hydrothermally grown ZnO nanostructures is significantly affected by different annealing atmospheres.

Enhanced efficiency of low-temperature fabricated dye-sensitized solar cells by incorporating upconversion nanoparticles

Upconversion nanoparticles (UCNPs) can effectively assist solar cells in utilizing near infrared through the anti-Stokes’ emission mechanism. We incorporate UCNPs, for the first time, into the mesoporous TiO2 of dye-sensitized solar cells (DSSCs) in a low-temperature fabrication process. The mesoporous TiO2 is designed as a two-layer structure, where the lower layer is prepared from reactive anatase TiO2 chelated by acetic acid (h-TAc). The UCNP incorporation into the lower layer displays a significant improvement in photovoltaic performance. For an optimized UCNP incorporation, the power conversion efficiency (PCE) of the DSSCs can increase from 6.49 to 7.98%, an enhancement of 23%, further exceeding most of the improvement on low-temperature fabricated DSSCs reported in the literature. The enhanced PCE may be ascribed to the increase of photocurrent. We find that the hydrophobic UCNPs reveal better enhancement than hydrophilic UCNPs due to the prevention from the electrolyte penetration. However, the hydrophobic UCNP incorporation may cause the cracking of the mesoporous TiO2 layer. The strong bonding ability of h-TAc effectively alleviates the cracking issue.