Biodistribution Analysis of Peptide-Coated Magnetic Iron Nanoparticles: A Simple and Quantitative Method.

Biodistribution tracks compounds or molecules of interest in vivo to understand a compound's anticipated efficacy and safety. Nanoparticles deliver nucleic acid and drug payloads and enhance tumor permeability due to multiple properties such as high surface area to volume ratio, surface functionalization, and modifications. Studying the in vivo biodistribution of nanoparticles documents the effectiveness and safety of nanoparticles and facilitates a more application-driven approach for nanoparticle development that allows for more successful translation into clinical use. In this study, we present a relatively simple method to determine the biodistribution of magnetic iron nanoparticles in mice. In vitro, cells take up branched amphiphilic peptide-coated magnetic nanobeads (BAPc-MNBs) like their counterparts, i.e., branched amphiphilic peptide capsules (BAPCs) with a hollow water-filled core. Both BAPc-MNBs and BAPCs have widespread applications as a nanodelivery system. We evaluated the BAPc-MNBs tissue distribution in wild-type mice injected intravenously (i.v.), intraperitoneally (i.p.), or orally gavaged to understand the biological interactions and to further the development of branched amphiphilic peptide-based nanoparticles. The magnetic nanoparticles allowed collection of the BAPc-MNBs from multiple organs by magnetic bead sorting, followed by a high-throughput screening for iron content. When injected i.v., nanoparticles were distributed widely to various organs before elimination from the system via the intestines in feces. The spleen accumulated the highest amount of BAPc-MNBs in mice administered NPs via i.v. and i.p. but not via oral gavage. Taken together, these data demonstrate that the magnetic sorting not only allowed quantification of the BAPc-MNBs but also identified the distribution of BAPc-MNBs after distinct administration methods.

Regulated Phase Separation in Al-Ti-Cu-Co Alloys through Spark Plasma Sintering Process.

With the goal of developing lightweight Al-Ti-containing multicomponent alloys with excellent mechanical strength, an Al-Ti-Cu-Co alloy with a phase-separated microstructure was prepared. The granulometry of metal particles was reduced using planetary ball milling. The particle size of the metal powders decreased as the ball milling time increased from 5, 7, to 15 h (i.e., 6.6 ± 6.4, 5.1 ± 4.3, and 3.2 ± 2.1 µm, respectively). The reduction in particle size and the dispersion of metal powders promoted enhanced diffusion during the spark plasma sintering process. This led to the micro-phase separation of the (Cu, Co)2AlTi (L21) phase, and the formation of a Cu-rich phase with embedded nanoscale Ti-rich (B2) precipitates. The Al-Ti-Cu-Co alloys prepared using powder metallurgy through the spark plasma sintering exhibited different hardnesses of 684, 710, and 791 HV, respectively, while maintaining a relatively low density of 5.8-5.9 g/cm3 (<6 g/cm3). The mechanical properties were improved due to a decrease in particle size achieved through increased ball milling time, leading to a finer grain size. The L21 phase, consisting of (Cu, Co)2AlTi, is the site of basic hardness performance, and the Cu-rich phase is the mechanical buffer layer between the L21 and B2 phases. The finer network structure of the Cu-rich phase also suppresses brittle fracture.

Weighted-Sum Operation of Three-Terminal Synapse Transistors in Array Configuration Using Spin-Coated Li-Doped ZrO2 Electrolyte Gate Insulator.

Artificial synapses with ideal functionalities are essential in hardware neural networks to allow for energy-efficient analog computing. Electrolyte-gated transistors (EGTs) are promising candidates for artificial synaptic devices due to their low voltage operations supported by large specific capacitances of electrolyte gate insulators (EGIs). We investigated the synapse transistor employing an In-Ga-Zn-O channel and a Li-doped ZrO2 (LZO) EGI so as to improve the short-term plasticity (STP) and long-term potentiation (LTP). The LZO EGIs showed distinct differences in characteristics depending on the Li doping concentration, and we adopted the optimum doping concentration of 10%. Based on the strong electric double layer effect secured from the LZO, we successfully demonstrated excellent synaptic operations with gradual modulations of excitatory synaptic plasticity with variations in amplitude, width, and number of applied pulse spikes. The introduction of the LZO EGI was verified to improve typical short-term plasticity such as paired-pulse facilitation. Furthermore, by minutely controlling the pulse spike conditions, the conversion to LTP from STP was clearly accomplished while implementing the anti-Hebbian spike timing-dependent plasticity. Finally, the array configuration of synaptic devices, which is essential for realizing neuromorphic computing, was also demonstrated. In a 3 × 3 array architecture, the weighted-sum operation was well emulated to assign multilevels in seven states with the pulse width modulation scheme.

Targeting FLT3-TAZ signaling to suppress drug resistance in blast phase chronic myeloid leukemia.

BACKGROUND: Although the development of BCR::ABL1 tyrosine kinase inhibitors (TKIs) rendered chronic myeloid leukemia (CML) a manageable condition, acquisition of drug resistance during blast phase (BP) progression remains a critical challenge. Here, we reposition FLT3, one of the most frequently mutated drivers of acute myeloid leukemia (AML), as a prognostic marker and therapeutic target of BP-CML. METHODS: We generated FLT3 expressing BCR::ABL1 TKI-resistant CML cells and enrolled phase-specific CML patient cohort to obtain unpaired and paired serial specimens and verify the role of FLT3 signaling in BP-CML patients. We performed multi-omics approaches in animal and patient studies to demonstrate the clinical feasibility of FLT3 as a viable target of BP-CML by establishing the (1) molecular mechanisms of FLT3-driven drug resistance, (2) diagnostic methods of FLT3 protein expression and localization, (3) association between FLT3 signaling and CML prognosis, and (4) therapeutic strategies to tackle FLT3+ CML patients. RESULTS: We reposition the significance of FLT3 in the acquisition of drug resistance in BP-CML, thereby, newly classify a FLT3+ BP-CML subgroup. Mechanistically, FLT3 expression in CML cells activated the FLT3-JAK-STAT3-TAZ-TEAD-CD36 signaling pathway, which conferred resistance to a wide range of BCR::ABL1 TKIs that was independent of recurrent BCR::ABL1 mutations. Notably, FLT3+ BP-CML patients had significantly less favorable prognosis than FLT3- patients. Remarkably, we demonstrate that repurposing FLT3 inhibitors combined with BCR::ABL1 targeted therapies or the single treatment with ponatinib alone can overcome drug resistance and promote BP-CML cell death in patient-derived FLT3+ BCR::ABL1 cells and mouse xenograft models. CONCLUSION: Here, we reposition FLT3 as a critical determinant of CML progression via FLT3-JAK-STAT3-TAZ-TEAD-CD36 signaling pathway that promotes TKI resistance and predicts worse prognosis in BP-CML patients. Our findings open novel therapeutic opportunities that exploit the undescribed link between distinct types of malignancies.

Thermal stress-assisted formation of submicron pillars from a thin film of CoCrCuFeNi high entropy alloy: experiments and simulations.

In this work, for the first time, the thermal stress-assisted formation of submicron pillars (SPs) from a high entropy alloy (HEA) thin film is made possible, and novel molecular dynamics (MD) simulations are proposed to assess the underlying mechanisms. In a series of experiments, the growth of quasi-equiatomic HEA SPs from CoCrCuFeNi HEA thin films was demonstrated under different heating and cooling conditions. Atomistic simulations are performed to probe possible formation mechanisms in two ways. One is to first obtain surface elastic constants and then conduct surface stability analysis with the consideration of size-dependent surface stress. The other is to effectively apply large compressive stress while simplifying the molecular dynamics (MD) model by using the Stoney equation to perform long-term MD simulations. From the former, it is suggested that surface diffusion is likely not the dominant cause for the observed pillar formation. From the latter, it is revealed that the level of compressive stress plays a much greater role than the crystalline structure of the film sample. Light has been shed on the stress-assisted formation of submicron pillars from CoCrCuFeNi HEA films by both experimental and simulation approaches.

Improvement in current drivability and stability in nanoscale vertical channel thin-film transistors via band-gap engineering in In-Ga-Zn-O bilayer channel configuration.

Vertical channel thin film transistors (VTFTs) have been expected to be exploited as one of the promising three-dimensional devices demanding a higher integration density owing to their structural advantages such as small device footprints. However, the VTFTs have suffered from the back-channel effects induced by the pattering process of vertical sidewalls, which critically deteriorate the device reliability. Therefore, to reduce the detrimental back-channel effects has been one of the most urgent issues for enhancing the device performance of VTFTs. Here we show a novel strategy to introduce an In-Ga-Zn-O (IGZO) bilayer channel configuration, which was prepared by atomic-layer deposition (ALD), in terms of structural and electrical passivation against the back-channel effects. Two-dimensional electron gas was effectively employed for improving the operational reliability of the VTFTs by inducing strong confinement of conduction electrons at heterojunction interfaces. The IGZO bilayer channel structure was composed of 3 nm-thick In-rich prompt (In/Ga = 4.1) and 12 nm-thick prime (In/Ga = 0.7) layers. The VTFTs using bilayer IGZO channel showed high on/off ratio (4.8 × 109), low SS value (180 mV dec-1), and high current drivability (13.6µAµm-1). Interestingly, the strategic employment of bilayer channel configurations has secured excellent device operational stability representing the immunity against the bias-dependent hysteretic drain current and the threshold voltage instability of the fabricated VTFTs. Moreover, the threshold voltage shifts of the VTFTs could be suppressed from +5.3 to +2.6 V under a gate bias stress of +3 MV cm-1for 104s at 60 °C, when the single layer channel was replaced with the bilayer channel. As a result, ALD IGZO bilayer configuration could be suggested as a useful strategy to improve the device characteristics and operational reliability of VTFTs.

Polarity Nano-Mapping of Polymer Film Using Spectrally Resolved Super-Resolution Imaging.

With the rapid development of the nanofabrication of polymer materials, the local measurement of the chemical properties of polymer nanostructures has become crucial because they can be highly heterogeneous at the nanoscale. We developed a spectroscopic imaging approach to characterize the nanoscale local polarity of polymer films via spectrally resolved super-resolution microscopy. We demonstrate the capability of the recently developed single-molecule sensing and imaging method to probe the polarity of polymers either inside a polymer matrix or on the external surface of a polymer. The nanoscale polarity sensing capability of our method facilitates the differentiation of various polymer surfaces based on chemical polarities, and it can further differentiate the polarity of functional side chain groups. Moreover, we demonstrate that a two-component polymer mixture can be locally distinguished based on the contrasting polarities of the lateral phase separation, further allowing for the investigation of nanoscale phase separation depending on the composition of the polymer blend film. This approach is anticipated to open the door to further characterizations of various nanocomposite materials.

Roles of Oxygen Interstitial Defects in Atomic-Layer Deposited InGaZnO Thin Films with Controlling the Cationic Compositions and Gate-Stack Processes for the Devices with Subµm Channel Lengths.

Roles of oxygen interstitial defects located in the In-Ga-Zn-O (IGZO) thin films prepared by atomic layer deposition were investigated with controlling the cationic compositions and gate-stack process conditions. It was found from the spectroscopic ellipsometry analysis that the excess oxygens increased with increasing the In contents within the IGZO channels. While the device using the IGZO channel with an In/Ga ratio of 0.2 did not show marked differences with the variations in the oxidant types during the gate-stack formation, the device characteristics were severely deteriorated with increasing the In/Ga ratio to 1.4, when the Al2O3 gate insulator (GI) was prepared with the H2O oxidants (H2O-Al2O3) due to a higher amount of excess oxygen in the channel. Additionally, during the deposition process of the Al-doped ZnO (AZO) gate electrode (GE) replacing from the indium-tin oxide (ITO) GE, the thermal annealing effect at 180 °C facilitated the passivation of oxygen vacancy and the strengthening of metal-oxygen bonding, which could stabilize the TFT operations. From these results, the gate-stack structure employing O3-processed Al2O3 GI (O3-Al2O3) and AZO GE (OA) was suggested to be most suitable for the device using IGZO channel with a higher In content. On the other hand, the device employing H2O-Al2O3 GI and AZO GE exhibited larger negative shifts of threshold voltage (VTH) under positive-bias-temperature stress (PBTS) condition than the device employing O3- Al2O3 GI and ITO GE due to larger hydrogen contents within the gate stacks. Anomalous negative shifts of VTH were accelerated with increasing the In contents of the IGZO channel. When the channel length of the fabricated device were scaled down to submicrometer regime, the OA gate stacks successfully alleviated the short-channel effects.

Efficiency Enhancement of Electro-Adsorption Desalination Using Iron Oxide Nanoparticle-Incorporated Activated Carbon Nanocomposite.

Capacitive deionization (CDI) technology is currently considered a potential candidate for brackish water desalination. In this study, we designed iron oxide nanoparticle-incorporated activated carbon (AC/Fe2O3) via a facile and cost-effective hydrothermal process. The as-synthesized material was characterized using several techniques and tested as electrodes in CDI applications. We found that the distinctive properties of the AC/Fe2O3 electrode, i.e., high wettability, high surface area, unique structural morphology, and high conductivity, resulted in promising CDI performance. The electrosorptive capacity of the AC/Fe2O3 nanocomposite reached 6.76 mg g-1 in the CDI process, with a high specific capacitance of 1157.5 F g-1 at 10 mV s-1 in a 1 M NaCl electrolyte. This study confirms the potential use of AC/Fe2O3 nanocomposites as viable electrode materials in CDI and other electrochemical applications.

A Personalized 3D-Printed Model for Obtaining Informed Consent Process for Thyroid Surgery: A Randomized Clinical Study Using a Deep Learning Approach with Mesh-Type 3D Modeling.

The aim of this study was to evaluate the usefulness of a personalized 3D-printed thyroid model that characterizes a patient's individual thyroid lesion. The randomized controlled prospective clinical trial (KCT0005069) was designed. Fifty-three of these patients undergoing thyroid surgery were randomly assigned to two groups: with or without a 3D-printed model of their thyroid lesion when obtaining informed consent. We used a U-Net-based deep learning architecture and a mesh-type 3D modeling technique to fabricate the personalized 3D model. The mean 3D printing time was 258.9 min, and the mean price for production was USD 4.23 for each patient. The size, location, and anatomical relationship of the tumor and thyroid gland could be effectively presented using the mesh-type 3D modeling technique. The group provided with personalized 3D-printed models showed significant improvement in all four categories (general knowledge, benefits and risks of surgery, and satisfaction; all p < 0.05). All patients received a personalized 3D model after surgery and found it helpful to understand the disease, operation, and possible complications and their overall satisfaction (all p < 0.05). In conclusion, the personalized 3D-printed thyroid model may be an effective tool for improving a patient's understanding and satisfaction during the informed consent process.

Implementation of oxide vertical channel TFTs with sub-150 nm channel length using atomic-layer deposited IGZO active and HfO2gate insulator.

We fabricated vertical channel thin film transistors (VTFTs) with a channel length of 130 nm using an ALD In-Ga-Zn-O (IGZO) active channel and high-k HfO2gate insulator layers. Solution-processed SiO2thin film, which exhibited an etch selectivity as high as 4.2 to drain electrode of indium-tin oxide, was introduced as a spacer material. For the formation of near-vertical sidewalls of the spacer patterns, the drain and spacer were successively patterned by means of two-step plasma etching technique using Ar/Cl2and Ar/CF4etch gas species, respectively. The SiO2spacer showed smooth surface morphology (Rq = 0.45 nm) and low leakage current component of 10-6A cm-2at 1 MV cm-1, which were suggested to be appropriate for working as spacer and back-channel. The fabricated VTFT showed sound transfer characteristics and negligible shifts in threshold voltage against the bias stresses of +5 and -5 V for 104s, even though there was abnormal increase in off-currents under the positive-bias stress due to the interactions between hydrogen-related defects and carriers. Despite the technical limitations of patterning process, our fabricated prototype IGZO VTFTs showed good operation stability even with an ultra-short channel length of 130 nm, demonstrating the potential of ALD IGZO thin film as an alternative channel for highly-scaled electronic devices.

Impact of oxide gate electrode for ferroelectric field-effect transistors with metal-ferroelectric-metal-insulator-semiconductor gate stack using undoped HfO2 thin films prepared by atomic layer deposition.

Ferroelectric field-effect transistors (FETs) with a metal-ferroelectric-metal-insulator-semiconductor (MFMIS) gate stack were fabricated and characterized to elucidate the key process parameters and to optimize the process conditions for guaranteeing nonvolatile memory operations of the device when the undoped HfO2 was employed as ferroelectric gate insulator. The impacts of top gate (TG) for the MFM part on the memory operations of the MFMIS-FETs were intensively investigated when the TG was chosen as metal Pt or oxide ITO electrode. The ferroelectric memory window of the MFMIS-FETs with ITO/HfO2/TiN/SiO2/Si gate stack increased to 3.8 V by properly modulating the areal ratio between two MFM and MIS capacitors. The memory margin as high as 104 was obtained during on- and off-program operations with a program pulse duration as short as 1 µs. There was not any marked degradation in the obtained memory margin even after a lapse of retention time of 104 s at 85 °C and repeated program cycles of 10,000. These obtained improvements in memory operations resulted from the fact that the choice of ITO TG could provide effective capping effects and passivate the interfaces.

Ferroelectric Switching in Trilayer Al2O3/HfZrOx/Al2O3 Structure.

Since ferroelectricity has been observed in simple binary oxide material systems, it has attracted great interest in semiconductor research fields such as advanced logic transistors, non-volatile memories, and neuromorphic devices. The location in which the ferroelectric devices are implemented depends on the specific application, so the process constraints required for device fabrication may be different. In this study, we investigate the ferroelectric characteristics of Zr doped HfO2 layers treated at high temperatures. A single HfZrOx layer deposited by sputtering exhibits polarization switching after annealing at a temperature of 850 °C. However, the achieved ferroelectric properties are vulnerable to voltage stress and higher annealing temperature, resulting in switching instability. Therefore, we introduce an ultrathin 1-nm-thick Al2O3 layer at both interfaces of the HfZrOx. The trilayer Al2O3/HfZrOx/Al2O3 structure allows switching parameters such as remnant and saturation polarizations to be immune to sweeping voltage and pulse cycling. Our results reveal that the trilayer not only makes the ferroelectric phase involved in the switching free from pinning, but also preserves the phase even at high annealing temperature. Simultaneously, the ferroelectric switching can be improved by preventing leakage charge.

Comparative studies on vertical-channel charge-trap memory thin-film transistors using In-Ga-Zn-O active channels deposited by sputtering and atomic layer depositions.

Vertical-channel charge-trap memory thin film-transistors (V-CTM TFTs) using oxide semiconductors were fabricated and characterized, in which In-Ga-Zn-O (IGZO) channels were prepared by sputtering and atomic-layer deposition (ALD) methods to elucidate the effects of deposition process. The vertical-channel gate stack of the fabricated device was verified to be well implemented on the vertical sidewall of the spacer patterns due to excellent step-coverage and self-limiting mechanisms of ALD process. The V-CTM TFTs using ALD-IGZO channel exhibited a wide memory window (MW) of 15.0 V at a VGS sweep of ±20 V and a large memory margin of 1.6 × 102 at a program pulse duration as short as 5 ms. The programmed memory margin higher than 105 did not experience any degradation with time evolution for 104 s. The mechanical durability was also evaluated after the delamination process of polyimide (PI) film. There were no marked variations in charge-trap-assisted MW even at a curvature radius of 1 mm and programmed memory margin even after repeated program operations of 104 cycles. The introduction of ALD process for the formation of IGZO active channel was suggested as a main process parameter to ensure the excellent memory device characteristics of the V-CTM TFTs.

Implementation of an electrically modifiable artificial synapse based on ferroelectric field-effect transistors using Al-doped HfO2 thin films.

Human brain-like synaptic behaviors of the ferroelectric field-effect transistors (FeFETs) were emulated by introducing the metal-ferroelectric-metal-insulator-semiconductor (MFMIS) gate stacks employing Al-doped HfO2 (Al:HfO2) ferroelectric thin films even at a low operation voltage. The synaptic plasticity of the MFMIS-FETs could be gradually modulated by the partial polarization characteristics of the Al:HfO2 thin films, which were examined to be dependent on the applied pulse conditions. Based on the ferroelectric polarization switching dynamics of the Al:HfO2 thin films, the proposed devices successfully emulate biological synaptic functions, including excitatory post-synaptic current (EPSC), paired-pulse facilitation (PPF), and spike timing-dependent plasticity (STDP). The channel conductance of the FeFETs could be controlled by partially switching the ferroelectric polarization of the Al:HfO2 gate insulators by means of pulse-number and pulse-amplitude modulations. Furthermore, the 3 × 3 array integrated with the Al:HfO2 MFMIS-FETs was also fabricated, in which electrically modifiable weighted-sum operation could be well verified in the 3 × 3 synapse array configuration.

Impact of Polyimide Film Thickness for Improving the Mechanical Robustness of Stretchable InGaZnO Thin-Film Transistors Prepared on Wavy-Dimensional Elastomer Substrates.

We report on the In-Ga-Zn-O thin-film transistors (IGZO TFTs) with outstanding mechanical stretchability, which were fabricated on ultrathin polyimide (PI) film/prestrained elastomer with a wavy-dimensional structure. The device characteristics of the fabricated devices were evaluated under mechanically strained conditions with various strains. The operational reliabilities against the bias stress conditions and during the cyclic stretching tests were also carefully examined. The stretchable IGZO TFTs exhibited good device operations without any marked degradation under stretching/compressed conditions with a strain of 40%. Under positive bias stress with a prestrain of 50%, the turn-on voltage instabilities for the TFTs prepared on 0.9 and 2.0 µm-thick PI films were estimated to be 1.5 and 3.9 V, respectively. During the cyclic stretching tests with a strain of 50%, the device operations failed after 20,000 and 100,000 stretching cycles for the TFTs fabricated on 2.0 and 0.9 µm-thick PI films, respectively. As a result, the IGZO TFTs fabricated on a thinner PI film presented more reliable operations after the repeated stretching events. The robust mechanical stretchability dependent on the PI film thickness was suggested to be due to the difference in critical values of bending radii and the influence of the local strain induced by the spatial fluctuations of the wavy structures.

Nitrogen Doping Effect for Improving Operation Reliability of Phase Modulator Using Ge2Sb2Te5 Thin Film for Hologram Image Implementation.

A phase modulation device was proposed for the implementation of hologram image for display applications. A Ge2Sb2Te5 (GST) film as thin as 7 nm was prepared between the ITO films to form the cavities corresponding a unit pixel. Nitrogen was incorporated into the GST for improving the thermal stability of the GST active region. The effects of the nitrogen doping on the physical properties of GST was investigated with the variations in doping amounts. The nitrogen incorporation was found to reduce the surface micro-roughness and to improve the thermal stability of the GST even after the crystallization by effectively suppressing the excessive grain growth. As results, the number of repeatable operations for the fabricated phase modulation device was evidently improved from 10 to 69 cycles when a 2.7-at% nitrogen was doped into the GST.

Investigations on the bias temperature stabilities of oxide thin film transistors using In-Ga-Zn-O channels prepared by atomic layer deposition.

Bias temperature stress stabilities of thin-film transistors (TFTs) using In-Ga-Zn-O (IGZO) channels prepared by the atomic layer deposition process were investigated with varying channel thicknesses (10 and 6 nm). Even when the IGZO channel thickness was reduced to 6 nm, the device exhibited good characteristics with a high saturation mobility of 15.1 cm2 V-1 s-1 and low sub-threshold swing of 0.12 V dec-1. Excellent positive and negative bias stress stabilities were also obtained. When positive bias temperature stress (PBTS) stability was tested from 40 to 80 °C for 104 s, the threshold voltages (V TH) of the device using the 6 nm-thick IGZO channel shifted negatively, and the V TH shifts increased from -0.5 to -6.9 V with the increasing temperature. Time-dependent PBTS instabilities could be explained by a stretched-exponential equation, representing a charge-trapping mechanism.

Reliability enhancement in thin film transistors using Hf and Al co-incorporated ZnO active channels deposited by atomic-layer-deposition.

Oxide thin films transistors (TFTs) with Hf and Al co-incorporated ZnO active channels prepared by atomic-layer deposition are presented. The Al concentration was fixed at 2.6 at% and the Hf concentration was varied from 3.3 to 6.3 at%. The HfAlZnO (HAZO) TFTs exhibited positive shifts in turn on voltages toward 0 V with a slight decrease in carrier mobility with increases in the incorporated Hf content and the post-annealing temperature. It was suggested that the carrier concentration and defect densities within the HAZO channels were reduced by incorporating Hf and performing the thermal annealing process. The TFT with HAZO channels with Hf content of 6.3 at% exhibited a turn-on operation at around 0 V and a low SS value of 0.3 V dec-1 without a marked decrease in carrier mobility. Furthermore, the device stabilities under bias, illumination, and temperature stresses could be greatly enhanced by reducing the formation of additional carriers and defects caused by weak Zn-O bonds due to the high binding energy of Hf with oxygen.

Effects of Deposition Temperature on the Device Characteristics of Oxide Thin-Film Transistors Using In-Ga-Zn-O Active Channels Prepared by Atomic-Layer Deposition.

We demonstrated the physical and electrical properties of the In-Ga-Zn-O (IGZO) thin films prepared by atomic-layer deposition (ALD) method and investigated the effects of the ALD temperature. The film composition (atomic ratio of In:Ga:Zn) and film density were examined to be 1:1:3 and 5.9 g/cm3, respectively, for all the temperature conditions. The optical band gaps decreased from 3.81 to 3.21 eV when the ALD temperature increased from 130 to 170 °C. The amounts of oxygen-related defects such as oxygen vacancies increased with increasing the ALD temperature. It was found from the in situ temperature-dependent electrical conductivity measurements that the electronic natures including the defect structures and conduction mechanism of the IGZO thin films prepared at different temperatures showed marked variations. The carrier mobilities in the saturation regions (µsat's) for the fabricated thin film transistors (TFTs) using the IGZO channel layers were estimated to be 6.1 to 14.8 cm2 V-1 s-1 with increasing the ALD temperature from 130 to 170 °C. Among the devices, when the ALD temperature was controlled to be 150 °C, the IGZO TFTs showed the best performance, which resulted from the fact that the amounts of oxygen vacancies and interstitial defects could be appropriately modulated at this condition. Consequently, the µsat, subthreshold swing, and on/off ratio for the TFT using the IGZO channel prepared at 150 °C showed 10.4 cm2 V-1 s-1, 90 mV/dec, and 2 × 109, respectively. The threshold voltage shifts of this device could also be effectively reduced to be 0.6 and -3.2 V under the positive-bias and negative-bias-illumination stress conditions. These obtained characteristics can be comparable to those for the sputter-deposited IGZO TFTs.