Search

Indium gallium tin oxide (IGTO) thin films have the potential for high mobility and low-temperature processing, which makes them suitable for applications such as display backplanes and high-voltage switching devices. However, very few studies have investigated the plasma-etching characteristics of IGTO and changes in its properties after etching. In this study, the etching characteristics of IGTO were investigated using Cl2/Ar plasma, and changes in surface properties were analyzed. Results showed that the etch rate increased with an increase in the proportion of Cl2, with the highest etch rate observed at 69 nm/min in pure Cl2 plasma with a gas flow rate of 100 sccm. Furthermore, increased radio-frequency power caused a rise in the etch rate, while a process pressure of 15 mTorr was optimal. The primary etching mechanism for IGTO thin films under Cl2 plasma was a chemical reaction, and an increased work function indicated the occurrence of defects on the surface. In addition, the etching process reduced the surface roughness of Cl2-containing plasma, whereas the etching process in pure Ar plasma increased surface roughness. This study contributes to a better understanding of the plasma-etching characteristics of IGTO and changes in its properties after etching, providing valuable insights for IGTO-based applications.

A traffic sign recognition system is crucial for safely operating an autonomous driving car and efficiently managing road facilities. Recent studies on traffic sign recognition tasks show significant advances in terms of accuracy on several benchmarks. However, they lack performance evaluation in driving cars in diverse road environments. In this study, we develop a traffic sign recognition framework for a vehicle to evaluate and compare deep learning-based object detection and tracking models for practical validation. We collect a large-scale highway image set using a camera-installed vehicle for training models, and evaluate the model inference during a test drive in terms of accuracy and processing time. In addition, we propose a novel categorization method for urban road scenes with possible scenarios. The experimental results show that the YOLOv5 detector and strongSORT tracking model result in better performance than other models in terms of accuracy and processing time. Furthermore, we provide an extensive discussion on possible obstacles in traffic sign recognition tasks to facilitate future research through numerous experiments for each road condition.

Kinetic characterization of ribosomal translocation is important for understanding the mechanism of elongation in protein synthesis. Here we have optimized a popular fluorescent-mRNA based translocation assay conducted in stopped-flow, by calibrating it with the functional tripeptide formation assay in quench-flow. We found that a fluorescently labelled mRNA, ten bases long from position +1 (mRNA+10), is best suited for both assays as it forms tripeptide at a fast rate equivalent to the longer mRNAs, and yet produces a large fluorescence change upon mRNA movement. Next, we compared the commonly used peptidyl tRNA analog, N-acetyl-Phe-tRNAPhe, with the natural dipeptidyl fMet-Phe-tRNAPhe in the stopped-flow assay. This analog translocates about two times slower than the natural dipeptidyl tRNA and produces biphasic kinetics. The rates reduce further at lower temperatures and with higher Mg2+ concentration, but improve with higher elongation factor G (EF-G) concentration, which increase both rate and amplitude of the fast phase significantly. In summary, we present here an improved real time assay for monitoring mRNA-translocation with the natural- and an N-Ac-analog of dipeptidyl tRNA., GRAPHICAL ABSTRACT

Due to its high dielectric constant (κ), the BaTiO3 (BTO) thin film has significant potential as a next-generation dielectric material for metal oxide semiconductor field-effect transistors (MOSFETs). Hence, the evaluation of the BTO thin film etching process is required for such nanoscale device applications. Herein, the etching characteristics and surface properties are examined according to the crystallinity of the BTO thin film. The results demonstrate that the etching rate is low in the high-crystallinity thin film, and the surface residues are much lower than in the low-crystallinity thin film. In particular, the accelerated Cl radicals in the plasma are shown to penetrate more easily into the low-crystallinity thin film than the high-crystallinity thin film. After the etching process, the surface roughness is significantly lower in the high-crystallinity thin film than in the low-crystallinity thin film. This result is expected to provide useful information for the process design of high-performance electronic devices.

Plasma etching processes for multi-atomic oxide thin films have become increasingly important owing to the excellent material properties of such thin films, which can potentially be employed in next-generation displays. To fabricate high-performance and reproducible devices, the etching mechanism and surface properties must be understood. In this study, we investigated the etching characteristics and changes in the surface properties of InGaZnO4 (IGZO) thin films with the addition of O2 gases based on a CF4/Ar high-density-plasma system. A maximum etch rate of 32.7 nm/min for an IGZO thin film was achieved at an O2/CF4/Ar (=20:25:75 sccm) ratio. The etching mechanism was interpreted in detail through plasma analysis via optical emission spectroscopy and surface analysis via X-ray photoelectron microscopy. To determine the performance variation according to the alteration in the surface composition of the IGZO thin films, we investigated the changes in the work function, surface energy, and surface roughness through ultraviolet photoelectron spectroscopy, contact angle measurement, and atomic force microscopy, respectively. After the plasma etching process, the change in work function was up to 280 meV, the thin film surface became slightly hydrophilic, and the surface roughness slightly decreased. This work suggests that plasma etching causes various changes in thin-film surfaces, which affects device performance.

Al-doped ZnO (AZO) is considered as an alternative to transparent conductive oxide materials. Patterning and achieving a stable surface are important challenges in the development and optimization of dry etching processes, which must be overcome for the application of AZO in various devices. Therefore, in this study, the etch rate and surface properties of an AZO thin film after plasma etching using the adaptive coupled plasma system were investigated. The fastest etch rate was achieved with a CF4/Ar ratio of 50:50 sccm. Regardless of the ratio of CF4 to Ar, the transmittance of the film in the visible region exceeded 80%. X-ray photoelectron spectroscopy analysis of the AZO thin film confirmed that metal-F bonding persists on the surface after plasma etching. It was also shown that F eliminates O vacancies. Consequently, the work function and bandgap energy increased as the ratio of CF4 increased. This study not only provides information on the effect of plasma on AZO thin film, but identifies the cause of changes in the device characteristics during device fabrication.

An unimorph piezoelectric cantilever generator with an interdigitated electrode (IDE) was developed for application to vibration energy harvesters driven in longitudinal mode. Lead zirconate titanate (PZT) thick film was fabricated by lamination of 10 sheets printed with Ag IDE; the laminated film was subsequently cofired at 850 °C for 2 h. Compared with a conventional IDE PZT thick film, the approximately 270 ㎛-thick cofired IDE PZT laminate revealed a significantly increased capacitance due to reduction of transition area. The use of multilayered IDE could result in the enhancement of energy harvesting performance for unimorph piezoelectric cantilever generator using PZT laminate. Optimized bending resonance frequency was obtained at 78 Hz for the unimorph piezoelectric cantilever generator with tip mass of 2.3 g driven in longitudinal vibration mode. Its energy harvesting performance was characterized as having a high power density of 26.7 mW/cm3 across the resistive load of 80 kΩ, corresponding to a normalized power factor of 6.7 mW/G2·cm3.

We consider a triple dot system with one of the dots coupled to a lead whose density of states varies in power-law fashion. Using the poor-man's scaling and the numerical renormalization group method, we investigate a quantum phase transition between local moment and partially Kondo-screened strong coupling phases with the variation of non-thermal control parameters. These quantum phases are closely related to low-energy doublet states formed by the triangular symmetry breaking. Since the lead has power-law density of states, the transition fixed point separating odd-parity and even-parity doublets depends on pseudo-gap exponent. The quantum phase in the even-parity doublet is determined by the magnitude of the hybridization width; the triple dot system lies in partially Kondo-screened strong coupling phase only for large enough hybridization width. Scaling result for the critical hybridization width is compared with that of numerical renormalization group method.

For automated driving technology to move beyond the proof stage and into actual automated driving, it is important to verify the safety of the automated driving system. In this paper, a method to ensure lateral control safety for the lane detection function is proposed to address a failure of the image-sensor-based automated driving system, which is the system with the highest possibility for practical mass production. The proposed algorithm consists of three parts: the first part is the ego-motion estimator that estimates the movement of a vehicle; the second is an integrated lane detection sensor module, which response to failure by estimating lane information at the corresponding time; the last is a lane estimator, which tracks lane coefficients based on constant lane widths. A combination of these three modules and the prediction of the lane coefficient, C3, in the virtual sensor, which was not reflected in our previous study, enables a more robust response to lane detection failure. The performance difference between the proposed algorithm and an existing algorithm was confirmed by simulated evaluations for identical situations based on actual data. Through this result, it was confirmed that not only could near-lane estimation accuracy but also lane estimation accuracy at a far distance could be improved when compared to the existing algorithm. The results of this study are expected to help obtain lateral safety during minimal risk maneuver. The proposed algorithm may also contribute to ensuring the safety of image-sensor-based automated driving systems.

We investigate the triple quantum dots with triangular geometry, in which one of the dots (embedded dot) is coupled to pseudo-gap Fermi system and electrons in the dot interact with a local phonon mode. The model, which we treat using the analytical argument and the numerical renormalization group, exhibits the quantum phase transition between ferromagnetically-coupled local moment phase and antiferromagnetically-coupled strong coupling phase depending upon electron-phonon coupling. We restrict our discussion to the case that inter-dot exchange couplings are much smaller than the Kondo temperature for the embedded dot. Since Fermi system has the density of states dependent on energy in power-law fashion, the embedded dot retains an unscreened spin degree of freedom even in Kondo regime. For the coupling to such Fermi system, the simultaneous increase of electron-phonon coupling and pseudo-gap exponent has the contrary effects on the quantum phase transition depending upon inter-dot couplings.

Work function tuning has a significant influence on the performance of semiconductor devices, owing to the formation of potential barriers at the interface between metal-semiconductor junctions. In this work, we introduce a technique for tuning the work function of ZnSnO thin films using high-density O2 plasma treatment. The work function and chemical composition of the ZnSnO thin film surfaces were investigated with regards to plasma treatment time through UPS/XPS systems. The optical band gap was estimated using Tauc&rsquo, s relationship from transmittance data. The work function of Zn0.6Sn0.4O thin film increased from 4.16 eV to 4.64 eV, and the optical band gap increased from 3.17 to 3.23 eV. The surface of Zn0.6Sn0.4O thin films showed a smooth morphology with an average of 0.65 nm after O2 plasma treatment. The O2 plasma treatment technique exhibits significant potential for application in high-performance displays in optical devices, such as thin-film transistors (TFTs), light-emitting diodes (LEDs), and solar cells.

Al-doped ZnO (AZO) is a promising transparent conducting oxide that can replace indium tin oxide (ITO) owing to its excellent flexibility and eco-friendly characteristics. However, it is difficult to immediately replace ITO with AZO because of the difference in their physical properties. Here, we study the changes in the physical properties of AZO thin films using Ar and O2 plasma treatments. Ar plasma treatment causes the changes in the surface and physical properties of the AZO thin film. The surface roughness of the AZO thin film decreases, the work function and bandgap slightly increase, and the sheet resistance significantly decreases. In contrast, a large work function change is observed in the AZO thin film treated with O2 plasma; however, the change in other characteristics is not significant. Therefore, the results indicate that post-treatment using plasma can accelerate the development of high-performance transparent devices.

Detection of a primary forward target is one of the most important factors in a longitudinal control system of automated driving vehicles. If there is no special event such as a lane change, a lane detected by a vision sensor can be deemed as a predicted driving path of the ego vehicle. Based on this, it is possible to determine the state of the primary forward target vehicle accurately using the detected lanes. However, malfunction of vision sensors can induce unrecognized and misrecognized lane detection problems on account of internal/external environment factors. Furthermore, if a detection point is getting farther from the subject vehicle, the detection accuracy is getting lower because of inaccuracy of lane model parameters. To solve these problems, a novel method of lane tracking has been investigated. First, an integrated sensor module that combines a virtual sensor and a vision sensor has been developed. The virtual sensor is combined kinematic and dynamic vehicle model to be used in the full-speed range. Second, a lane estimator to improve lane detection accuracy at a long distance has been developed. The lane width in the public road can be assumed to be constant in the same road type. Based on this assumption, the clothoid parameters can be restored and consequently improve the lane detection accuracy. The performance of the proposed algorithm was verified by actual vehicle tests on public roads with manual driving and on proving ground with an automated driving system. The proposed algorithm has been compared with a conventional method which is based on in-vehicle yaw rate sensor. The test results have shown significant improvement of lane tracking performance over the conventional method.

The main objective of our work is to increase transmittance in the mid infrared region by removing impurities through the pre-heating treatment of zinc sulfide (ZnS) produced by hydrothermal synthesis. The pre-heating treatment proceeded at 450 to 600 °C for 2 h under vacuum atmosphere (10−2 Torr). It was confirmed that the particle size increased as the pre-heating temperature increased. Additionally, all ZnS nano powders had a sphalerite (cubic) structure unaffected by pre-heating treatment. The ZnS nano powders were sintered by hot-press sintering method. As the pre-heating temperature increased, transmittance was improved due to the decreasing of porosity, increase of particle size, and the removal of impurities (carbon and sulfate). However, when the pre-heating treatment temperature was 600 °C, the transmittance slightly decreased due to the formation of a hexagonal phase. The ZnS ceramic with pre-heating treatment at 550 °C showed the highest transmittance (71.6%) and density (99.9%).

Thin-film multijunction solar cells are considered to be the most promising structure for next-generation photovoltaic devices. We fabricated CuGaSe2 (CGS)/Cu(In,Ga)Se2 (CIGS) monolithic tandem solar cells. The intermediate AZO film was used as a recombination layer between the top cell and the bottom cell, and its thickness was varied from 50 to 200 nm. The best tandem cell parameters with a 50 nm thick Al-doped ZnO (AZO) layer showed a V OC = 1.03 V, J SC = 10.24 mA/cm2, FF = 41.5%, and efficiency = 4.32%. We showed the V OC of monolithic tandem cell to be over 1 V under illumination. We also observed the current continuity between the CGS cell and the CIGS cell which were connected in series as subcells. As the AZO thickness increased, the spectral response of the top cell decreased and the bottom cell was not completely saturated. The 50 nm thick AZO layer leads the CIGS bottom cell to be current-limiting, whereas the 200 nm thick AZO layer shifts the limitation to the CGS top cell. The results also showed that the In element diffusion into the CGS top absorber enhanced the electrical and optical properties of the top cell, whereas the Zn element diffusion into CIGS bottom absorber tended to degrade the bottom cell simultaneously.

Al-doped ZnO (AZO) has attracted significant attention as a transparent electrode with low cost, high transmittance, high electrical conductivity, and excellent mechanical flexibility. A high-resolution patterning process is required for its application to next-generation displays, which can be achieved through the plasma etching process. In this study, we investigated the etching mechanism for Al-doped ZnO thin films in a BCl3/Ar-based plasma system and observed the performance of the thin-film surface after the etching process. The etch rate of the AZO thin films was highest at BCl3/Ar = 25:75, and increased as the power of the radio frequency source and bias increased. The etching mechanism was elucidated through optical emission and X-ray photoelectron spectroscopic analyses and confirmed to be the interaction between the bombardment of Ar ions and the chemical reaction of Cl and Cl2 radicals. BCl3-based plasma etching induces various changes in the properties of the AZO thin-film surface. The surface of the AZO thin film becomes very smooth, the work function increases by approximately 200 meV, and the bandgap increases by approximately 0.03 eV after the etching process in BCl3-based plasma. In addition, the electrical properties, such as sheet resistance and carrier mobility, are significantly improved. The results of this study may be applied for the development of high-performance optical and electronic devices.

We investigate the quantum phase transition in triple quantum dot system with triangular geometry, in which one of the dots is connected to metallic leads and electrons in the dot interact with a local phonon mode. The influence of electron-phonon interaction on the quantum phase transition between local moment phase and Kondo screened strong coupling phase at the particle-hole symmetric point is studied based on the analytical arguments and the numerical renormalization group method. The results show that the critical value of tunnel-coupling between side dots decreases with the increase of electron-phonon coupling in “spin Kondo” regime. Furthermore, at a certain critical value of electron-phonon coupling, there appears only strong coupling phase, irrespective of tunnel-coupling between dots. The study of the influence of electron-phonon interaction on the quantum phase transition in triple quantum dot has the great importance for clarifying the mechanism of Kondo screening in the system.

We study numerically and analytically magnetic field dependence of partially separated Andreev bound states (ps-ABSs), which are localized on both sides of hybrid semiconductor-superconductor nanowire, considering the spatial inversion symmetry of proximity-induced pairing potential with finite coherence length and tunnel one. Finite coherence length results in the occurrence of topologically nontrivial regions near the ends of the nanowire, where near-zero energy ps-ABSs are energetically degenerate due to the spatial inversion symmetry. With increasing the applied magnetic field, the degeneracy is lifted by the overlap between the ps-ABSs near the opposite ends of the nanowire, leading to the appearance of a robust near-zero energy Majorana bound state (MBS) localized at both ends and a nanowire bulk-like state. Our findings provide a mechanism for coexisting of near-zero energy ps-ABS and bulk-like state in the nanowire.

The topological features of the dynamic electron density and the electrostatic potential (ESP) of the dynamic charge density of LiFePO4 have been analyzed by using the structure factors calculated accurately from the independent atom model (IAM). The integrated charges of ions at nuclear critical points (NCPs) have been evaluated and the topological properties at bond critical points (BCPs) of P–O and Fe–O bonds in the PO4 tetrahedron and FeO6 octahedron have been considered. The values and variations of the ESP have been analyzed through two-dimensional contour maps in the planes perpendicular to the a and b axes. We have found four spiral channels with negative ESP that Li+ ion migration is possible along the [010] direction in a unit cell. Each channel reveals extremely low values (less than −0.9e/A) of the ESP and variations undistinguished within 0.04e/A interval. The average width of each channel is more than known radius of Li+ ion. In a unit cell, two channels show right hand twist and other two channels do left hand twist. Since passing through the gaps between adjacent FeO6 octahedrons, these channels can be considered as the possible pathways of Li+ ion migration that oxidation/reduction of the Fe2+ ion can be expected during charge/discharge. Although there exist also four zigzag channels with negative ESP along the [100] direction, because of the average width less than ionic radius, Li+ ion migration is impossible. The ESP channels along the [001] and [101] directions have been not found. Possible three-dimensional curved aspects of the pathways of Li+ ion migration in charge/discharge process in lithium-ion battery have been presented.