Dependence of electrical properties on sulfur distribution in atomic-layer-deposited HfO2 thin film on an InP substrate

S passivation of a HfO2 film on an InP substrate is demonstrated using annealing in H2S ambient either before or after ALD of the HfO2 film. We examined the resulting distribution and chemical state of the incorporated S both in the HfO2 film and at its interface with the InP substrate using secondary ion mass spectroscopy and X-ray absorption spectroscopy. Annealing in H2S ambient before ALD of HfO2 resulted in accumulation of S at the interface in the sulfide (S2-) phase (due to lack of oxygen), which effectively suppressed interfacial reactions during ALD and passivated interfacial defect states. On the other hand, annealing in H2S ambient after ALD of the HfO2 film induced a sulfate (S6+) phase in the film due to the abundant oxygen in the film, as well as a sulfide (S2-) phase at the interface. This improved the charge trapping behavior by decreasing the bulk defect density in the HfO2 film.This work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science ICT & Future Planning (No. 2017R1A2B4002842) and by the Ministry of Education (No. 2018R1D1A1B07043427)

Modulation of Ca2+ Signaling in Neuroendocrine Cells

Docto

New materials in advanced gate stacks for next generation complementary metal oxide semiconductor field effect transistors(CMOSFETs) technology

Thesis(doctors)--서울대학교 대학원 :재료공학부,2008.2.Docto

Visible light-driven g-C3N4@ZnO heterojunction photocatalyst synthesized via atomic layer deposition with a specially designed rotary reactor

A g-C3N4@ZnO heterojunction is demonstrated using atomic layer deposition (ALD) of ZnO. A specially designed rotary reactor was used to maintain mechanical dispersion of g-C3N4 powder during the ALD process. Stable, uniform, and intimate heterojunctions between g-C3N4 and ZnO were produced, which induced effective charge separation; thus, the photocatalytic activity of the composites was enhanced. The photocatalytic performance was evaluated by the degradation of methylene blue dye. The photocatalytic reaction rate constant of the optimal g-C3N4@ZnO with five ALD cycles was five times and two times higher than those of pristine g-C3N4 and gC(3)N(4)@TiO2 composite, respectively. Furthermore, the photocorrosion of ZnO was inhibited by coupling with gC(3)N(4), which was confirmed through cyclic photo-degradation with three consecutive dye degradation tests. The synergistic effects of the g-C3N4@ZnO heterojunction, enhanced photocatalytic activity and photocorrosion resistance were proven.This work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (No. 2017R1A2B4002842), and an internal research program of the Korea Institute of Industrial Technology (No. EO19081)

Highly sensitive non-enzymatic lactate biosensor driven by porous nanostructured nickel oxide

Lactate sensors are increasingly used for applications in sports and clinical medicine, but currently have several shortcomings including low sensitivity. We demonstrate a highly sensitive and selective non-enzymatic lactate sensor based on porous nickel oxide by sol-gel based inverse micelle method. The porosity and surface area of nickel oxide depending on the calcination temperature (250, 350, and 450 degrees C) were compared using electron microscopy and a Brunauer-Emmett-Teller (BET) surface area analyzer. Furthermore, we also compared the chemical state of Ni3+ in porous nickel oxides, which is known to be strongly engaged with electrocatalytic lactate detection, with different calcination temperature. The sensing characteristics were assessed using an amperometric response with a three-electrode system. Owing to a relatively large surface area and high Ni3+/Ni2+ ratio, NiO calcined at 250 degrees C, exhibit maximum sensitivity at 62.35 mu A/mM (cm(2)), and a minimum detection of limit of 27 mu M, although, it has large amount of organic residue because of low calcination temperature. In addition to its sensitivity, a porous nickel oxide electrode also displays good selectivity against other interferents such as L-ascorbic acid, uric acid, and dopamine, further supporting its potential as a non-enzymatic lactate sensor.This research was financially supported by an internal research program of the Korea Institute of Industrial Technology, South Korea (Project No. PE019052), and by the Human Resources Development program (No. 20174030201830) of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government Ministry of Trade, Industry and Energy

Inhibition of voltage-sensitive calcium channels by adenosine and forskolin in PC 12 cells

Maste

Highly Uniform Resistive Switching Performances Using Two-Dimensional Electron Gas at a Thin-Film Heterostructure for Conductive Bridge Random Access Memory

This research demonstrates, for the first time, the development of highly uniform resistive switching devices with self-compliance current for conductive bridge random access memory using two-dimensional electron gas (2DEG) at the interface of an Al2O3/TiO2 thin-film heterostructure via atomic layer deposition (ALD). The cell is composed of Cu/Ti/Al2O3/TiO2, where Cu/Ti and Al2O3 overlayers are used as the active/buffer metals and solid electrolyte, respectively, and the 2DEG at the interface of Al2O3/TiO2 heterostructure, grown by the ALD process, is adopted as a bottom electrode. The Cu/Ti/Al2O3/TiO2 device shows reliable resistive switching characteristics with excellent uniformity under a repetitive voltage sweep (direct current sweep). Furthermore, it exhibits a cycle endurance over 10(7) cycles under short pulse switching. Remarkably, a reliable operation of multilevel data writing is realized up to 10(7) cycles. The data retention time is longer than 10(6) s at 85 degrees C. The uniform resistance switching characteristics are achieved via the formation of small (similar to a few nm width) Cu filament with a short tunnel gap (˂0.5 nm) owing to the 2DEG at the Al2O3/TiO2 interface. The performance and operation scheme of this device may be appropriate in neuromorphic applications.This work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT, & Future Planning (Nos. NRF- 2019R1C1C1008577, 2017R1A2B4002842), by the Technology Innovation Program (No. 20003555) funded by the Ministry of Trade, Industry & Energy(MOTIE, Korea), and also supported by the GRRC Program of Gyeonggi Province (GRRC AJOU 2016B03, Photonics-Medical Convergence Technology Research Center)

Thermal Atomic Layer Deposition of Device-Quality SiO2 Thin Films under 100 °C Using an Aminodisilane Precursor

SiO2 is one of the most important dielectric materials that is widely used in the microelectronics industry, but its growth or deposition requires high thermal budgets. Herein, we report a low-temperature thermal atomic layer deposition (ALD) process to fabricate SiO2 thin films using a novel aminodisilane precursor with a Si-Si bond, 1,2-bis-(diisopropylamino)disilane (BDIPADS), together with ozone. To compare the film quality, ALD SiO2 films grown at various temperatures from 250 down to 50 degrees C were systematically investigated. Our data suggest that even without the aid of plasma-enhanced or catalyzed surface reactions, high-quality SiO2 films with relatively high growth rates, high film densities, and low impurity contents compared to conventional Si precursors can be attained through our process at a low growth temperature (similar to 50 degrees C). Chemical analyses via Auger electron spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy confirm the formation of stoichiometric SiO2 films without noticeable impurity contents of nitrogen and carbon, regardless of the growth temperature. However, low-temperature growth of the SiO2 film (˂= 80 degrees C) results in a slight ingress of SiH-related moieties during the ALD processes that is not observed at temperatures over 80 degrees C. Density functional theory calculations show that the Si-Si bond present in the BDIPADS precursor is easier to be oxidized compared to the Si-H bonds. Through electrical characterization of the SiO2 films grown at different temperatures, we confirm only slight degradation in the dielectric constants, leakage currents, and breakdown fields with decreasing growth temperature, which may be due to the slightly decreased film density and the increased defect density of SiH-related bonds.This research was supported by the MOTIE (Ministry of Trade, Industry & Energy, no. 10053098) and KSRC (Korea Semiconductor Research Consortium) support program for the development of the future semiconductor device. This work was also supported under the framework of international cooperation program managed by the National Research Foundation of South Korea (NRF-2018K2A9A1A01090484). B.S. was partially supported by 2018 Hongik University Research Fund