• KIEE International Transactions on Electrophysics and Applications
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• 제2C권6호
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• pp.281-286
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• 2002

The temperature accelerated dielectric breakdown strength of on-wafer low-k dielectric polymer films with thicknesses ranging from 94 nm to 1141 nm is investigated by using the current-voltage characteristic measurements with MIS structures. The temperature dependence of dielectric strength is demonstrated to be Arrhenious for all thicknesses. However, the activation energy is found to be strongly thickness dependent. It follows an exponential relationship rather than being a single value, i.e., the activation energy increase significantly as film thickness increases for the thickness below 500 nm, but it is almost constant for the thickness above 500 nm. This relationship suggests that the change of the activation energy corresponding to different film thickness is closely related to the temperature dependence of the electron trapping/detrapping process in polymer thin films, and is determined by both the trapping rate and the detrapping rate. Thinner films need less energy to form a conduction path compared to thicker films. Hence, it leads to smaller activation energy in thinner films, and the activation energy increases with the increase in film thickness. However, a nearly constant value of the activation energy is achieved above a certain range of film thickness, indicating that the trapping rate and detrapping rate is almost equal and eventually the activation energy approaches the value of bulk material.

• Transactions on Electrical and Electronic Materials
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• 제16권3호
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• pp.130-134
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• 2015

This research proposes the use of a composition modulated (ZrO₂)_x(Al₂O₃)_1-x film as a charge trapping layer for charge trap flash memory; this is possible when the Zr (Al) atomic percent is controlled to form a variable bandgap as identified by the valence band offsets and electron energy loss spectrum measurements. Compared to memory devices with uniform compositional (ZrO₂)_0.1(Al₂O₃)_0.9 or a (ZrO₂)_0.92(Al₂O₃)_0.08 trapping layer, the memory device using the composition modulated (ZrO₂)_x(Al₂O₃)_1-x as the charge trapping layer exhibits a larger memory window (6.0 V) at the gate sweeping voltage of ±8 V, improved data retention, and significantly faster program/erase speed. Improvements of the memory characteristics are attributed to the special energy band alignments resulting from non-uniform distribution of elemental composition. These results indicate that the composition modulated (ZrO₂)_x(Al₂O₃)_1-x film is a promising candidate for future nonvolatile memory device applications.

• Transactions on Electrical and Electronic Materials
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• 제15권5호
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• pp.245-248
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• 2014

$Pt/Al_2O_3/Si_3N_4/SiO_2/Si$ charge trap flash memory structures with various thicknesses of the $Si_3N_4$ charge trapping layer were fabricated. According to the calculated and measured results, we depicted electron loss in a schematic diagram that illustrates how the trap to band tunneling and thermal excitation affects electrons loss behavior with the change of $Si_3N_4$ thickness, temperature and trap energy levels. As a result, we deduce that $Si_3N_4$ thicknesses of more than 6 or less than 4.3 nm give no contribution to improving memory performance.

• International Journal of Internet, Broadcasting and Communication
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• 제12권2호
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• pp.30-36
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• 2020

We demonstrated a successful fabrication of 4" Gallium Nitride (GaN)/Diamond High Electron Mobility Transistors (HEMTs) incorporated with Inner Slot Via Hole process. We made in manufacturing technology of 4" GaN/Diamond HEMT wafers in a compound semiconductor foundry since reported [1]. Wafer thickness uniformity and wafer flatness of starting GaN/Diamond wafers have improved greatly, which contributed to improved processing yield. By optimizing Laser drilling techniques, we successfully demonstrated a through-substrate-via process, which is last hurdle in GaN/Diamond manufacturing technology. To fully exploit Diamond's superior thermal property for GaN HEMT devices, we include Aluminum Nitride (AlN) barrier in epitaxial layer structure, in addition to conventional Aluminum Gallium Nitride (AlGaN) barrier layer. The current collapse revealed very stable up to Vds = 90 V. The trapping behaviors were measured Emission Microscope (EMMI). The traps are located in interface between Silicon Nitride (SiN) passivation layer and GaN cap layer.

• 한국재료학회지
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• 제30권8호
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• pp.413-420
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• 2020

Lu₃Al_5-xGa_xO₁₂:Ce³⁺,Cr³⁺ powders are prepared using a solid-state reaction method. To determine the crystal structure, Rietveld refinement is performed. The results indicate that Ga³⁺ ions preferentially occupied tetrahedral rather than octahedral sites. The lattice constant linearly increases, obeying Vegard's law, despite the strong preference of Ga³⁺ for the tetrahedral sites. Increasing x led to a blue-shift of the Ce³⁺ emission band in the green region and a change in the emission intensity. Persistent luminescence is observed from the powders prepared with x = 2-3, occurring through a trapping and detrapping process between Ce³⁺ and Cr³⁺ ions. The longest persistent luminescence is achieved for x = 2; its lifetime is at least 30 min. The findings are explained using crystal structure refinement, crystal field splitting, optical band gap, and electron trapping mechanism.

• Journal of Astronomy and Space Sciences
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• 제21권2호
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• pp.93-100
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• 2004

We have investigated characteristic solar wind dynamics associated with relativistic electron events at geosynchronous orbit. Most of the events for April, 1999 through December, 2002 are found to be accompanied by a prolonged solar quiet period which is characterized as low solar wind density, weak interplanetary magnetic field (IMF), and fast alfvenic fluctuations in IMF $B_z$. In a typical relativistic event, electron fluxes begin to increase by orders of magnitude when solar wind parameters drop to low values (e.g., $n_{sw}∼5 cm^{-3}$ and ｜$B_{IMF}$∼5 nT) after sharp peaks. Then the elevated electron fluxes stay at the high level during the solar quiet period. This observation may suggest the following scenario for the occurrence of a geosynchronous relativistic event: (ⅰ) Quiet solar winds can yield a stable and more dipole-like magnetospheric configurations in which the geosynchronous orbit locates well inside the trapping boundary of the energetic electrons. (ⅱ) If a large population of MeV electrons are generated (by whatever acceleration process(es)) in the inner magnetosphere, they can be trapped and effectively accumulated to a high intensity. (ⅲ) The high electron flux can persist for a number of days in the geosynchronous region as long as the solar wind dynamics stays quiet. Therefore the scenario indicates that the occurrence of a relativistic event would be a result of a delicate balance between the effects of electron acceleration and loss. In addition, the sensitive dependence of a relativistic event on the solar wind conditions makes the prediction of solar wind variability as important as understanding of electron acceleration processes in the forecast of a relativistic event.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.273.2-273.2
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• 2014

Sputtering process has been widely used in Si-based semiconductor industry and it is also an ideal method to deposit transparent oxide materials for thin-film transistors (TFTs). The oxide films grown at low temperature by conventional RF sputtering process are typically amorphous state with low density including a large number of defects such as dangling bonds and oxygen vacancies. Those play a crucial role in the electron conduction in transparent electrode, while those are the origin of instability of semiconducting channel in oxide TFTs due to electron trapping. Therefore, post treatments such as high temperature annealing process have been commonly progressed to obtain high reliability and good stability. In this work, the scheme of electron-assisted RF sputtering process for high quality transparent oxide films was suggested. Through the additional electron supply into the plasma during sputtering process, the working pressure could be kept below $5{\times}10-4Torr$. Therefore, both the mean free path and the mobility of sputtered atoms were increased and the well ordered and the highly dense microstructure could be obtained compared to those of conventional sputtering condition. In this work, the physical properties of transparent oxide films such as conducting indium tin oxide and semiconducting indium gallium zinc oxide films grown by electron-assisted sputtering process will be discussed in detail. Those films showed the high conductivity and the high mobility without additional post annealing process. In addition, oxide TFT characteristics based on IGZO channel and ITO electrode will be shown.

• JSTS:Journal of Semiconductor Technology and Science
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• 제16권2호
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• pp.185-190
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• 2016

A 70-${\AA}$ nanowire field-effect transistor (FET) for sub-10-nm CMOS technology is designed and simulated in order to investigate the impact of an oxide trap on random telegraph noise (RTN) in the device. It is observed that the drain current fluctuation (${\Delta}I_D/I_D$) increases up to a maximum of 78 % due to the single electron trapping. In addition, the effect of various trap positions on the RTN in the nanowire FET is thoroughly analyzed at various drain and gate voltages. As the drain voltage increases, the peak point for the ${\Delta}I_D/I_D$ shifts toward the source side. The distortion in the electron carrier density and the conduction band energy when the trap is filled with an electron at various positions in the device supports these results.

• 한국환경과학회지
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• 제29권1호
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• pp.95-108
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• 2020

Silver nanoparticles were loaded onto g-C₃N₄ (CN) with a nanoroll-type morphology (Ag/CN) synthesized using a co-polymerization method for highly selective conversion of toxic nitrobenzene to industrially-valuable aminobenzene. Scanning electron microscopy and high-resolution transmission electron microscopy (HRTEM) images of Ag/CN revealed the generation of the nanoroll-type morphology of CN. Additionally, HRTEM analysis provided direct evidence of the generation of a Schottky barrier between Ag and CN in the Ag/CN nanohybrid. Photoluminescence analysis and photocurrent measurements suggested that the introduction of Ag into CN could minimize charge recombination rates, enhancing the mobility of electrons and holes to the surface of the photocatalyst. Compared to pristine CN, Ag/CN displayed much higher ability in the photocatalytic reduction of nitrobenzene to aminobenzene, underscoring the importance of Ag deposition on CN. The enhanced photocatalytic performance and photocurrent generation were primarily ascribed to the Schottky junction formed at the Ag/CN interface, greater visible-light absorption efficiency, and improved charge separation associated with the nanoroll morphology of CN. Ag would act as an electron sink/trapping center, enhancing the charge separation, and also serve as a good co-catalyst. Overall, the synergistic effects of these features of Ag/CN improved the photocatalytic conversion of nitrobenzene to aminobenzene.

• Applied Microscopy
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• 제39권1호
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• pp.57-64
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• 2009

점착식 포충엽을 형성하는 식충식물은 포충엽 표피조직에 발달하는 분비모에서 점액성 물질을 분비하여 곤충을 포획한다. 본 연구에서는 점착식 포충엽을 형성하여 식충의 기능을 수행하는 끈끈이주걱속의 비나타와 피그미 2종의 분비모 분화 발달양상을 형태구조 및 세포학적으로 연구하였다. 분화초기 코일형태의 정단에서 발달하는 비나타의 엽원기는 표피에 미분화된 불규칙적인 형태의 모용이 밀생하였으며, 정단 부위는 신장 후 분지되면서 엽연과 엽신에는 capitate형과 peltate형 분비모들이 발달하였다. 피그미의 어린 포충엽은 엽연의 미분화된 모용들이 구심적으로 접힌 상태로 발달하나, 엽육조직 생장에 따라 길게 신장된 capitate형으로 분화되어 방사상으로 배열하였다. 실험된 2종의 포충엽은 분비모 특성에 의한 상 하피의 분화가 뚜렷하였으며, 상피 엽신과 엽연에는 분비물질을 방출하는 다양한 분비모가 밀생하였다. 상피의 경우, 비나타 분비모는 병세포가 신장된 capitate형과 무병의 peltate형으로 대별되고, 피그미는 병세포의 길이를 달리하는 capitate형만 발달하였다. 특히, 비나타는 엽연에 약 $2.2{\sim}3.4mm$에 이르는 긴 capitate형 분비모를 형성하였고, 피그미 엽연에는 위 유형과 함께 라켓 형태의 두정 부위를 지니고 약 $3.7{\sim}4.2mm$로 신장된 독특한 유형의 2 종류 capitate형 분비모가 분포하였다. 하피의 경우, 비나타에서는 작은 peltate형 분비모만 발달하였고, 피그미에서는 capitate형과 유사하나 capitate와 peltate형의 중간적인 특징을 지닌 매우 축소된 분비모를 형성하였다. 이들 분비모 두정부위의 분비세포 세포질에는 미토콘드리아 및 소포체, 골지체 등이 잘 발달하였고, 소액포들의 융합으로 큰 분비강이 형성되어 축적된 물질을 외부로방출하였다. 표피조직에 밀생하는 capitate 및 peltate형 분비모에서 방출된 점액성 물질은 포충엽 표면에 곤충 접촉 시 엽연 capitate형 분비모에 의한 굴곡운동과 엽신 분비모의 활성화를 유도하여 더욱 능동적으로 곤충을 포획하였다. 본 연구에서 밝혀진 비나타 및 피그미에 대한 분비모의 구조적 정보는 이후 Drosophyllum, Pinguicula 등의 다른 점착식 포충엽 형성 종들의 분비모 분화 양상과 비교 분석되면 유용하게 활용될 수 있는 자료가 될 것이다.