Eui-jung Yun - Academia.edu (original) (raw)

Papers by Eui-jung Yun

Research paper thumbnail of Optimization on the fabrication process of Si pressure sensors utilizing piezoresistive effect

Journal of the Institute of Electronics Engineers of Korea, 2005

In this paper, the fabrication process of Si pressure sensors utilizing piezoresistive effect was... more In this paper, the fabrication process of Si pressure sensors utilizing piezoresistive effect was optimized. The efficiency(yield) of the fabrication process for Si piezoresistive pressure sensors was improved by conducting Si anisotrophic etching process after processes of piezoresistors and AI circuit patterns. The position and process parameters for piezoresistors were determined by ANSYS and SUPREM simulators, respectively. The measured thickness of p-type Si piezoresistors from the boron depth-profile measurement was in good agreement with the simulated one from SUPREM simulation. The Si anisotrohic etching process for diaphragm was optimized by adding ammonium persulfate(AP) to tetramethyl ammonium hydroxide (TMAH) solution.

Research paper thumbnail of Characterization of Undoped ZnO Films Post-Annealed by Using Helium Gas

Journal of the Korean Physical Society, 2009

In this study, we used helium gas for the rst time for annealing undoped ZnO lms at di erent temp... more In this study, we used helium gas for the rst time for annealing undoped ZnO lms at di erent temperatures in the range of 500 800 C and we report their structural, optical and electrical properties. All measurements were carried out at room temperature. The undoped ZnO samples exhibited a (002) preferential orientation with the c-axis perpendicular to the substrate, suggesting that samples of high quality were prepared. The PL spectra of the ZnO samples revealed a strong near-band-edge ultraviolet (UV) emission peak at 3.26 eV, a strong red emission peak at 1.91 eV and a weak green emission peak at 2.36 eV, which were attributed to a free electron-acceptor transition, a zinc interstitial and a single ionized oxygen vacancy, respectively. All peak strengths in the PL spectra increased with increasing post-annealing temperature. We also con rmed from PL and Hall measurements that all samples revealed n-type conductivity. With increasing post-annealing temperature, the electron carrier concentration and the strength of UV emission peak increased, suggesting that they are related to each other.

Research paper thumbnail of High-energy Electron Beam Irradiation of Al-doped ZnO Thin Films Deposited at Room Temperature

Journal of the Korean Physical Society, 2011

ABSTRACT In this research, we demonstrated the effects of high-energy electron beam irradiation (... more ABSTRACT In this research, we demonstrated the effects of high-energy electron beam irradiation (HEEBI) on the optical and structural properties of Al-doped ZnO (AZO) films grown on transparent corning glass substrates at room temperature (RT) by using a. radio-frequency magnetron sputtering technique. The AZO thin films were treated with HEEBI in air at RT at an electron beam energy of 0.8 MeV and doses of 1 x 10(14) - 1 x 10(16) electrons/cm(2). The photoluminescence (PL) measurements revealed that the dominant peak at 2.77 eV was a blue emission originating from donor-like defects, oxygen vacancies (V(o)), suggesting that the n-type conductivity was preserved in HEEBI-treated films. On the basis of PL, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy results, we suggest that the density of V(o) donor defects is decreased due to in-diffusion of oxygen from the ambient into the films after HEEBI treatment at low doses up to 10(15) electrons/cm(2) while the opposite phenomenon can occur with further increase in the dose. We also found from the XRD analysis that the worse crystallinity with a smaller grain size was observed in HEEBI-treated AZO films at a higher close, corresponding to a higher oxygen fraction in the films. We believe that our results will contribute to developing high-quality AZO-based materials and devices for space applications.

Research paper thumbnail of Effects of SF6 plasma treatment on the properties of InGaZnO thin films

Japanese Journal of Applied Physics, 2018

The effects of sulfur hexafluoride (SF 6) plasma on the properties of amorphous InGaZnO (a-IGZO) ... more The effects of sulfur hexafluoride (SF 6) plasma on the properties of amorphous InGaZnO (a-IGZO) thin films were examined. The properties of the a-IGZO thin films were characterized by Hall effect measurement, dynamic secondary ion mass spectroscopy (SIMS), and X-ray photoelectron spectroscopy (XPS). The IGZO thin films treated with SF 6 plasma before annealing had a very high resistance mainly owing to the inclusion of S into the film surface, as evidenced by SIMS profiles. On the other hand, the samples treated with SF 6 plasma after annealing showed better electrical properties with a Hall mobility of 10 cm 2 /(V&s) than the untreated samples or the samples SF 6 plasma-treated before annealing. This was attributed to the increase in the number of oxygen vacancy defects in the a-IGZO thin films owing to the enhanced out-diffusion of O to the ambient and the increase in the number of F-related donor defects originating from the incorporation of a much larger amount of F than of S into the film surface, which were confirmed by XPS and SIMS.

Research paper thumbnail of Feature Extraction System for Land Cover Changes Based on Segmentation

Journal of remote sensing, 2004

This study focused on providing a methodology to utilize temporal information obtained from remot... more This study focused on providing a methodology to utilize temporal information obtained from remotely sensed data for monitoring a wide variety of targets on the earth's surface. Generally, a methodology in understanding of global changes is composed of mapping. quantifying, and monitoring changes in the physical characteristics of land cover. The selected processing and analysis technique affects the quality of the obtained information. In this research, feature extraction methodology is proposed based on segmentation. It requires a series of processing of multitempotal images: preprocessing of geometric and radiometric correction, image subtraction/thresholding technique. and segmentation/thresholding. It results in the mapping of the change-detected areas. Here. the appropriate methods are studied for each step and especially, in segmentation process, a method to delineate the exact boundaries of features is investigated in multi resolution framework to reduce computational co...

Research paper thumbnail of The Coexistence of One-dimensional Conductance Quantization and Tunneling Phenomena in Vlamorphous-V₂O_5IV Thin Film Structures

Journal of electrical engineering and information science, 1997

We report that the room temperature one-dimensional conductance quantization in Vlamorphous-V₂O_5... more We report that the room temperature one-dimensional conductance quantization in Vlamorphous-V₂O_5IV sandwich structures is interphase and electronically induced phenomena, and is associated with metallic VO₂ filament formation. From fitting parameters(barrier width=22A. dielectric constant of insulator=24) obtained from the interpretation of the measured background I-V data in terms of tunneling model and the capacitance vs oxide thickness characteristic showing that the interphase layer plays a dominant role, we conclude that the one-dimensional conductance quantization is an interphase phenomenon and the interphase consists of low temperature VO₂ Based on the observation of a highly characteristic threshold voltage for the onset of the conductance quantization and independence of threshold voltage on amorphous-oxide thickness and junction area. we suggest that a ballistic point contact is formed in the nonmetallmetal interphase by electronic injection. The threshold voltage decrea...

Research paper thumbnail of Effects of Oxygen Partial Pressure on the Properties of SnOx Thin Films Doped with Indium

Journal of Nanoelectronics and Optoelectronics

This study examined the effects of the oxygen partial pressure on the properties of heavily indiu... more This study examined the effects of the oxygen partial pressure on the properties of heavily indium-doped tin-oxide (In-SnOx) thin films grown at room temperature by reactive direct-current pulse sputtering from a mixed metallic target containing Sn (70 atomic %)-In (30 atomic %). X-ray photoelectron spectroscopy (XPS), dynamic secondary-ion mass spectrometry, X-ray diffraction (XRD), and Hall Effect measurements showed that the In-SnOx samples prepared with oxygen pressures of 10–20% had metallic properties. This was attributed to the notable Sn0 area ranges of 5.6–17.3%, low resistivity ranges of 5.5×10−3–2×10−4 Ωcm, and the high carrier concentration ranges of 3.5×1021–5.1×1022/cm3. On the other hand, the Sn4+ area and the resistivity increased significantly to 73.3% and 9.4 Ωcm. In comparison, the Sn2+ area and the electron concentration decreased dramatically to 23.6% and 6.5×1016/cm3, respectively, with increasing oxygen partial pressure up to 30%. The samples prepared with oxy...

Research paper thumbnail of A study on the performance improvement of an adaptive, real-time traffic assignment scheduler using the TP coefficient

As recent fusion industry and ubiquitous technology have grown fast, network contents, which requ... more As recent fusion industry and ubiquitous technology have grown fast, network contents, which require high load, are provided in various infrastructures and facilities such as u-city and smart phones. Therefore, it is anticipated that the playback quality of multimedia compared to network loads degrades dramatically due to the drastic increment of real-time reference of conventional high load contents (eg. multimedia data). In this paper, we improved the method of the traffic assignment based on MPP which elevated the playback quality of multimedia by assigning discriminately the possible traffic of MMS with TP coefficients. When the TP coefficient which combines content preference with media preference was applied to a real-time traffic assignment scheduler, the simulation results showed that the multimedia playback stream was assigned within the possible traffic of a server. The real-time scheduling algorithm was imp roved by using the TP coefficient that combines the time-dependen...

Research paper thumbnail of A Study on the Properties of Al doped ZnO (AZO) Thin Films Deposited by RF Magnetron Sputtering

In this paper, we investigated the effects of fraction on the properties of Al-doped ZnO (AZO) th... more In this paper, we investigated the effects of fraction on the properties of Al-doped ZnO (AZO) thin films prepared by radio frequency (RF) magnetron sputtering. Hall, photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS) measurements revealed that the p-type conductivity was exhibited for AZO films with an fraction of 0.9 while the n-type conductivity was observed for films with fractions in range of 0 - 0.6. PL and XPS also showed that the acceptor-like defects, such as zinc vacancies and oxygen interstitials, increased in films prepared by an fraction of 0.9, resulting in the p-type conductivity in the films. Hall results indicated that AZO films prepared by fractions in range of 0 - 0.6 can be used for electrode layers in the applications of transparent thin film transistor. We concluded from the X-ray diffraction analysis that worse crystallinity with a smaller grain size as well as higher tensile stress was observed in the films prepared by a higher fraction, which...

Research paper thumbnail of Tunable (LSMO) Ferromagnetic Thin Films for Radio Frequency Applications

In this letter, an original work in tunable (LSMO) ferromagnetic thin film materials for radio fr... more In this letter, an original work in tunable (LSMO) ferromagnetic thin film materials for radio frequency applications is presented. 400 nm thick LSMO thin film is formed by the chemical solution deposition on the top of indium tin oxide heterostructure. Interdigitated capacitor structures are used to study the behavior of LSMO thin film materials when a dc electrostatic field bias is applied. With increasing the dc voltage bias, the differential resistance of the film decreases. This change is pronounced in the measured scattering parameters of the device. The presented structure exhibits a tunable wide resistance. Index Terms—Ferromagnetic, (LSMO), mate- rial parameters, tunability, tunable circuit, tunable inductor.

Research paper thumbnail of Threshold Switching Into Conductance Quantized States in Amorphous-Vanadium Pentoxide/vanadium Thin Film Structures

Research paper thumbnail of Development of a Pressure Measurement System with the Parallel Structure

Journal of the Korean Institute of Electrical and Electronic Material Engineers

Research paper thumbnail of Electrical Properties of Amorphous-Indium-Gallium-Zinc-Oxide Based Thin-Film Transistors with Four Terminal Configuration

Science of Advanced Materials

Research paper thumbnail of Effect of the spin-on-glass curing atmosphere on In–Ga–Zn–O thin-film transistors

Journal of Information Display

A solution-based spin-on glass (SOG) was applied to the gate insulator of an oxide thin-film tran... more A solution-based spin-on glass (SOG) was applied to the gate insulator of an oxide thin-film transistor (TFT). The curing atmosphere of the SOG was investigated to enhance the performance of the self-aligned top-gate In-Ga-Zn-O (IGZO) TFT. After the SOG layer was formed on an IGZO active layer, curing was performed under N 2 , air, and O 2 atmospheres. The curing under an N 2 atmosphere resulted in the best device characteristics for the IGZO TFT. After curing, the SOG films were investigated via atomic force microscopy, secondary ion mass spectroscopy, Fourier transform infrared spectroscopy, and capacitance measurement. The results showed that the N 2 pileup at the back surface of the SOG is the main reason for the enhanced performance of the TFT after curing under an N 2 atmosphere.

Research paper thumbnail of Effects of the Post-Annealing Treatment on the Properties of Ga-Doped SnOx Thin Films

Journal of the Korean Physical Society

We investigated the effects of the post-annealing treatment (PAT) on the properties of Ga-doped t... more We investigated the effects of the post-annealing treatment (PAT) on the properties of Ga-doped tin-oxide (Ga-SnOx) thin films grown at room temperature by using a radio-frequency magnetron sputtering technique. On the basis of X-ray photoelectron spectroscopy (XPS), dynamic secondaryion mass spectrometry, X-ray diffraction (XRD), and Hall Effect measurements, we conclude that n-type SnO2 is the dominant phase in all samples regardless of PAT at low temperatures (25-200 • C). The Sn 2+ area decreased to 32.5% with increasing temperature up to 150 • C, with a simultaneous increase in the Sn 4+ area to 59%. This was attributed to a decrease and an increase in the Ga and the oxygen contents in the samples, respectively, which also caused a decrease in the number of oxygen vacancies in the samples treated at higher temperatures. In contrast, XPS on the samples post-annealed at temperatures higher than 150 • C showed results opposite to those of the samples treated at temperatures lower than 150 • C. This indicates that the Ga ions in Ga-doped SnOx films act as hole acceptors and that heat treatment is useful for controlling the number of oxygen vacancies, Sn 2+ ions, and Sn 4+ ions in Ga-doped SnOx films. In addition, XRD showed that post-annealing did not affect the amorphous phase in the samples.

Research paper thumbnail of Effects of Structure and Sputtering Parameters on the Device Properties of Tin-Oxide Thin-Film Transistors

Journal of the Korean Physical Society

We investigated the device properties of sputter-deposited tin-oxide (SnO) thin-film transistors ... more We investigated the device properties of sputter-deposited tin-oxide (SnO) thin-film transistors (TFTs) in which the SnOx active layers were deposited by using a SnO sputtering target. The developed SnO-TFTs had a bottom-gate staggered or coplanar structure, which used a heavilydoped Si wafer as a gate electrode and 300-nm-thick SiO2 as a gate dielectric layer. The TFTs with SnOx thin-films deposited using a high radio-frequency (RF) power of 100 W, a very high working pressure of 20 mTorr, and an oxygen ratio of 0% revealed n-type characteristics. The coplanar SnOxbased TFTs showed better n-type characteristics than the staggered ones, which was attributed to the good quality of the sputtered damage-free SnOx films. On the other hand, the staggered TFTs with SnOx deposited at a low RF power of 50 W, a low working pressure of 4 mTorr, and an oxygen ratio of 12% exhibited p-type characteristics, which included an onset voltage (Von) of-1.5 V, a saturated hole mobility of 39 cm 2 /Vs at gate-to-source voltage (VGS) = −10 V, a sub-threshold swing of 1 V/decade at VGS − Von = −0.5 V, and an on/off ratio of 1.1 × 10 2. We believe that our results can contribute to the development of p-type SnO-based TFTs with good performance.

Research paper thumbnail of The Effect of Bake Temperature on SU-8 Gate Insulator of IGZO Thin Film Transistor

Journal of the Korean Physical Society

SU-8 photoresist was applied to the gate insulator of a-IGZO TFT. The hard bake temperature of SU... more SU-8 photoresist was applied to the gate insulator of a-IGZO TFT. The hard bake temperature of SU-8 is important and was varied from 95 to 185 • C. The FTIR showed that hard-bake temperature higher than 125 • C is necessary for complete polymerization. The leakage current and breakdown voltage were improved as increasing hard bake temperatures to 155 • C. However, the crack was generated at 185 • C degrading the electrical characteristics of insulator. The SU-8 insulator was successfully applied to a-IGZO TFT where the on-off ratio was highest for hard-bake temperature of 155 • C.

Research paper thumbnail of Effects of Plasma Treatment on the Composition and Phase Changes of Sputter-Deposited SnOx Thin Films

Journal of Nanoscience and Nanotechnology

This study examined the effects of the plasma treatment of CF₄ or SF6 on the properties of tin ox... more This study examined the effects of the plasma treatment of CF₄ or SF6 on the properties of tin oxide (SnOx) thin films prepared at room temperature using a radio frequency sputtering technique. The properties of the samples were characterized by dynamic-secondary ion mass spectrometry, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Hall Effect measurements. All untreated samples showed Sn4+ and Sn2+ XPS peak area percentages of 57.6 and 34.6%, respectively, indicating a larger amount of SnO₂ phase in the samples than SnO. The samples treated with CF₄ plasma exhibited the maximum and minimum Sn4+ and Sn2+ peak areas, respectively, at a treatment time of 35 s. This was attributed to the maximum oxygen atomic percentage at 35 s and the injection of additional carbon and fluorine into the sample with increasing treatment time. On the other hand, in the case of samples treated with SF6 plasma, the Sn4+ peak area increased with increasing treatment time while the Sn2+ peak area decreased. This suggests that SnO₂ is a stronger phase for samples treated with SF6 plasma for a longer duration. Furthermore, the changes in the Sn4+ and Sn2+ peak areas of the samples treated with CF₄ plasma were much larger than those of the samples treated with SF6 plasma, which indicates that CF₄ plasma has a larger impact on the properties of the samples. This difference in impact showed a correlation with the sharper decrease in the number of oxygen vacancies for CF₄ plasma-treated samples. These results were attributed to the introduction of additional fluorine and carbon into CF₄ plasma-treated samples compared to the SF6 plasma-treated ones. In addition, XRD showed that the plasma treatment did not affect the amorphous phase in the samples.

Research paper thumbnail of Effects of Oxygen Ratio on the Properties of Tin Oxide Thin Films Doped with Bismuth

physica status solidi (a)

Research paper thumbnail of Development of oxide thin-film transistor using all spin-on-glass insulators with addition of hydrogen peroxide: Buffer, gate insulator, and interlayer dielectric

Japanese Journal of Applied Physics

A top-gate oxide thin-film transistor (TFT) with all spin-on-glass (SOG) insulators was developed... more A top-gate oxide thin-film transistor (TFT) with all spin-on-glass (SOG) insulators was developed. The SOG is based on methyl siloxane and was used for the buffer layer, gate insulator, and interlayer dielectric instead of a vacuum process. The SOG was diluted with ethanol, and a small amount of hydrogen peroxide was added. The diluted SOG was applied to top-gate amorphous indium–gallium–zinc-oxide TFTs, and the effects of the dilution and the hydrogen peroxide added were investigated. The TFTs with the optimized SOG insulators showed a mobility of 7.1 cm2/(Vs), a threshold voltage of 0.5 V, a subthreshold slope of 0.1 V/dec, and an on/off current ratio of 3.6 × 107.

Research paper thumbnail of Optimization on the fabrication process of Si pressure sensors utilizing piezoresistive effect

Journal of the Institute of Electronics Engineers of Korea, 2005

In this paper, the fabrication process of Si pressure sensors utilizing piezoresistive effect was... more In this paper, the fabrication process of Si pressure sensors utilizing piezoresistive effect was optimized. The efficiency(yield) of the fabrication process for Si piezoresistive pressure sensors was improved by conducting Si anisotrophic etching process after processes of piezoresistors and AI circuit patterns. The position and process parameters for piezoresistors were determined by ANSYS and SUPREM simulators, respectively. The measured thickness of p-type Si piezoresistors from the boron depth-profile measurement was in good agreement with the simulated one from SUPREM simulation. The Si anisotrohic etching process for diaphragm was optimized by adding ammonium persulfate(AP) to tetramethyl ammonium hydroxide (TMAH) solution.

Research paper thumbnail of Characterization of Undoped ZnO Films Post-Annealed by Using Helium Gas

Journal of the Korean Physical Society, 2009

In this study, we used helium gas for the rst time for annealing undoped ZnO lms at di erent temp... more In this study, we used helium gas for the rst time for annealing undoped ZnO lms at di erent temperatures in the range of 500 800 C and we report their structural, optical and electrical properties. All measurements were carried out at room temperature. The undoped ZnO samples exhibited a (002) preferential orientation with the c-axis perpendicular to the substrate, suggesting that samples of high quality were prepared. The PL spectra of the ZnO samples revealed a strong near-band-edge ultraviolet (UV) emission peak at 3.26 eV, a strong red emission peak at 1.91 eV and a weak green emission peak at 2.36 eV, which were attributed to a free electron-acceptor transition, a zinc interstitial and a single ionized oxygen vacancy, respectively. All peak strengths in the PL spectra increased with increasing post-annealing temperature. We also con rmed from PL and Hall measurements that all samples revealed n-type conductivity. With increasing post-annealing temperature, the electron carrier concentration and the strength of UV emission peak increased, suggesting that they are related to each other.

Research paper thumbnail of High-energy Electron Beam Irradiation of Al-doped ZnO Thin Films Deposited at Room Temperature

Journal of the Korean Physical Society, 2011

ABSTRACT In this research, we demonstrated the effects of high-energy electron beam irradiation (... more ABSTRACT In this research, we demonstrated the effects of high-energy electron beam irradiation (HEEBI) on the optical and structural properties of Al-doped ZnO (AZO) films grown on transparent corning glass substrates at room temperature (RT) by using a. radio-frequency magnetron sputtering technique. The AZO thin films were treated with HEEBI in air at RT at an electron beam energy of 0.8 MeV and doses of 1 x 10(14) - 1 x 10(16) electrons/cm(2). The photoluminescence (PL) measurements revealed that the dominant peak at 2.77 eV was a blue emission originating from donor-like defects, oxygen vacancies (V(o)), suggesting that the n-type conductivity was preserved in HEEBI-treated films. On the basis of PL, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy results, we suggest that the density of V(o) donor defects is decreased due to in-diffusion of oxygen from the ambient into the films after HEEBI treatment at low doses up to 10(15) electrons/cm(2) while the opposite phenomenon can occur with further increase in the dose. We also found from the XRD analysis that the worse crystallinity with a smaller grain size was observed in HEEBI-treated AZO films at a higher close, corresponding to a higher oxygen fraction in the films. We believe that our results will contribute to developing high-quality AZO-based materials and devices for space applications.

Research paper thumbnail of Effects of SF6 plasma treatment on the properties of InGaZnO thin films

Japanese Journal of Applied Physics, 2018

The effects of sulfur hexafluoride (SF 6) plasma on the properties of amorphous InGaZnO (a-IGZO) ... more The effects of sulfur hexafluoride (SF 6) plasma on the properties of amorphous InGaZnO (a-IGZO) thin films were examined. The properties of the a-IGZO thin films were characterized by Hall effect measurement, dynamic secondary ion mass spectroscopy (SIMS), and X-ray photoelectron spectroscopy (XPS). The IGZO thin films treated with SF 6 plasma before annealing had a very high resistance mainly owing to the inclusion of S into the film surface, as evidenced by SIMS profiles. On the other hand, the samples treated with SF 6 plasma after annealing showed better electrical properties with a Hall mobility of 10 cm 2 /(V&s) than the untreated samples or the samples SF 6 plasma-treated before annealing. This was attributed to the increase in the number of oxygen vacancy defects in the a-IGZO thin films owing to the enhanced out-diffusion of O to the ambient and the increase in the number of F-related donor defects originating from the incorporation of a much larger amount of F than of S into the film surface, which were confirmed by XPS and SIMS.

Research paper thumbnail of Feature Extraction System for Land Cover Changes Based on Segmentation

Journal of remote sensing, 2004

This study focused on providing a methodology to utilize temporal information obtained from remot... more This study focused on providing a methodology to utilize temporal information obtained from remotely sensed data for monitoring a wide variety of targets on the earth's surface. Generally, a methodology in understanding of global changes is composed of mapping. quantifying, and monitoring changes in the physical characteristics of land cover. The selected processing and analysis technique affects the quality of the obtained information. In this research, feature extraction methodology is proposed based on segmentation. It requires a series of processing of multitempotal images: preprocessing of geometric and radiometric correction, image subtraction/thresholding technique. and segmentation/thresholding. It results in the mapping of the change-detected areas. Here. the appropriate methods are studied for each step and especially, in segmentation process, a method to delineate the exact boundaries of features is investigated in multi resolution framework to reduce computational co...

Research paper thumbnail of The Coexistence of One-dimensional Conductance Quantization and Tunneling Phenomena in Vlamorphous-V₂O_5IV Thin Film Structures

Journal of electrical engineering and information science, 1997

We report that the room temperature one-dimensional conductance quantization in Vlamorphous-V₂O_5... more We report that the room temperature one-dimensional conductance quantization in Vlamorphous-V₂O_5IV sandwich structures is interphase and electronically induced phenomena, and is associated with metallic VO₂ filament formation. From fitting parameters(barrier width=22A. dielectric constant of insulator=24) obtained from the interpretation of the measured background I-V data in terms of tunneling model and the capacitance vs oxide thickness characteristic showing that the interphase layer plays a dominant role, we conclude that the one-dimensional conductance quantization is an interphase phenomenon and the interphase consists of low temperature VO₂ Based on the observation of a highly characteristic threshold voltage for the onset of the conductance quantization and independence of threshold voltage on amorphous-oxide thickness and junction area. we suggest that a ballistic point contact is formed in the nonmetallmetal interphase by electronic injection. The threshold voltage decrea...

Research paper thumbnail of Effects of Oxygen Partial Pressure on the Properties of SnOx Thin Films Doped with Indium

Journal of Nanoelectronics and Optoelectronics

This study examined the effects of the oxygen partial pressure on the properties of heavily indiu... more This study examined the effects of the oxygen partial pressure on the properties of heavily indium-doped tin-oxide (In-SnOx) thin films grown at room temperature by reactive direct-current pulse sputtering from a mixed metallic target containing Sn (70 atomic %)-In (30 atomic %). X-ray photoelectron spectroscopy (XPS), dynamic secondary-ion mass spectrometry, X-ray diffraction (XRD), and Hall Effect measurements showed that the In-SnOx samples prepared with oxygen pressures of 10–20% had metallic properties. This was attributed to the notable Sn0 area ranges of 5.6–17.3%, low resistivity ranges of 5.5×10−3–2×10−4 Ωcm, and the high carrier concentration ranges of 3.5×1021–5.1×1022/cm3. On the other hand, the Sn4+ area and the resistivity increased significantly to 73.3% and 9.4 Ωcm. In comparison, the Sn2+ area and the electron concentration decreased dramatically to 23.6% and 6.5×1016/cm3, respectively, with increasing oxygen partial pressure up to 30%. The samples prepared with oxy...

Research paper thumbnail of A study on the performance improvement of an adaptive, real-time traffic assignment scheduler using the TP coefficient

As recent fusion industry and ubiquitous technology have grown fast, network contents, which requ... more As recent fusion industry and ubiquitous technology have grown fast, network contents, which require high load, are provided in various infrastructures and facilities such as u-city and smart phones. Therefore, it is anticipated that the playback quality of multimedia compared to network loads degrades dramatically due to the drastic increment of real-time reference of conventional high load contents (eg. multimedia data). In this paper, we improved the method of the traffic assignment based on MPP which elevated the playback quality of multimedia by assigning discriminately the possible traffic of MMS with TP coefficients. When the TP coefficient which combines content preference with media preference was applied to a real-time traffic assignment scheduler, the simulation results showed that the multimedia playback stream was assigned within the possible traffic of a server. The real-time scheduling algorithm was imp roved by using the TP coefficient that combines the time-dependen...

Research paper thumbnail of A Study on the Properties of Al doped ZnO (AZO) Thin Films Deposited by RF Magnetron Sputtering

In this paper, we investigated the effects of fraction on the properties of Al-doped ZnO (AZO) th... more In this paper, we investigated the effects of fraction on the properties of Al-doped ZnO (AZO) thin films prepared by radio frequency (RF) magnetron sputtering. Hall, photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS) measurements revealed that the p-type conductivity was exhibited for AZO films with an fraction of 0.9 while the n-type conductivity was observed for films with fractions in range of 0 - 0.6. PL and XPS also showed that the acceptor-like defects, such as zinc vacancies and oxygen interstitials, increased in films prepared by an fraction of 0.9, resulting in the p-type conductivity in the films. Hall results indicated that AZO films prepared by fractions in range of 0 - 0.6 can be used for electrode layers in the applications of transparent thin film transistor. We concluded from the X-ray diffraction analysis that worse crystallinity with a smaller grain size as well as higher tensile stress was observed in the films prepared by a higher fraction, which...

Research paper thumbnail of Tunable (LSMO) Ferromagnetic Thin Films for Radio Frequency Applications

In this letter, an original work in tunable (LSMO) ferromagnetic thin film materials for radio fr... more In this letter, an original work in tunable (LSMO) ferromagnetic thin film materials for radio frequency applications is presented. 400 nm thick LSMO thin film is formed by the chemical solution deposition on the top of indium tin oxide heterostructure. Interdigitated capacitor structures are used to study the behavior of LSMO thin film materials when a dc electrostatic field bias is applied. With increasing the dc voltage bias, the differential resistance of the film decreases. This change is pronounced in the measured scattering parameters of the device. The presented structure exhibits a tunable wide resistance. Index Terms—Ferromagnetic, (LSMO), mate- rial parameters, tunability, tunable circuit, tunable inductor.

Research paper thumbnail of Threshold Switching Into Conductance Quantized States in Amorphous-Vanadium Pentoxide/vanadium Thin Film Structures

Research paper thumbnail of Development of a Pressure Measurement System with the Parallel Structure

Journal of the Korean Institute of Electrical and Electronic Material Engineers

Research paper thumbnail of Electrical Properties of Amorphous-Indium-Gallium-Zinc-Oxide Based Thin-Film Transistors with Four Terminal Configuration

Science of Advanced Materials

Research paper thumbnail of Effect of the spin-on-glass curing atmosphere on In–Ga–Zn–O thin-film transistors

Journal of Information Display

A solution-based spin-on glass (SOG) was applied to the gate insulator of an oxide thin-film tran... more A solution-based spin-on glass (SOG) was applied to the gate insulator of an oxide thin-film transistor (TFT). The curing atmosphere of the SOG was investigated to enhance the performance of the self-aligned top-gate In-Ga-Zn-O (IGZO) TFT. After the SOG layer was formed on an IGZO active layer, curing was performed under N 2 , air, and O 2 atmospheres. The curing under an N 2 atmosphere resulted in the best device characteristics for the IGZO TFT. After curing, the SOG films were investigated via atomic force microscopy, secondary ion mass spectroscopy, Fourier transform infrared spectroscopy, and capacitance measurement. The results showed that the N 2 pileup at the back surface of the SOG is the main reason for the enhanced performance of the TFT after curing under an N 2 atmosphere.

Research paper thumbnail of Effects of the Post-Annealing Treatment on the Properties of Ga-Doped SnOx Thin Films

Journal of the Korean Physical Society

We investigated the effects of the post-annealing treatment (PAT) on the properties of Ga-doped t... more We investigated the effects of the post-annealing treatment (PAT) on the properties of Ga-doped tin-oxide (Ga-SnOx) thin films grown at room temperature by using a radio-frequency magnetron sputtering technique. On the basis of X-ray photoelectron spectroscopy (XPS), dynamic secondaryion mass spectrometry, X-ray diffraction (XRD), and Hall Effect measurements, we conclude that n-type SnO2 is the dominant phase in all samples regardless of PAT at low temperatures (25-200 • C). The Sn 2+ area decreased to 32.5% with increasing temperature up to 150 • C, with a simultaneous increase in the Sn 4+ area to 59%. This was attributed to a decrease and an increase in the Ga and the oxygen contents in the samples, respectively, which also caused a decrease in the number of oxygen vacancies in the samples treated at higher temperatures. In contrast, XPS on the samples post-annealed at temperatures higher than 150 • C showed results opposite to those of the samples treated at temperatures lower than 150 • C. This indicates that the Ga ions in Ga-doped SnOx films act as hole acceptors and that heat treatment is useful for controlling the number of oxygen vacancies, Sn 2+ ions, and Sn 4+ ions in Ga-doped SnOx films. In addition, XRD showed that post-annealing did not affect the amorphous phase in the samples.

Research paper thumbnail of Effects of Structure and Sputtering Parameters on the Device Properties of Tin-Oxide Thin-Film Transistors

Journal of the Korean Physical Society

We investigated the device properties of sputter-deposited tin-oxide (SnO) thin-film transistors ... more We investigated the device properties of sputter-deposited tin-oxide (SnO) thin-film transistors (TFTs) in which the SnOx active layers were deposited by using a SnO sputtering target. The developed SnO-TFTs had a bottom-gate staggered or coplanar structure, which used a heavilydoped Si wafer as a gate electrode and 300-nm-thick SiO2 as a gate dielectric layer. The TFTs with SnOx thin-films deposited using a high radio-frequency (RF) power of 100 W, a very high working pressure of 20 mTorr, and an oxygen ratio of 0% revealed n-type characteristics. The coplanar SnOxbased TFTs showed better n-type characteristics than the staggered ones, which was attributed to the good quality of the sputtered damage-free SnOx films. On the other hand, the staggered TFTs with SnOx deposited at a low RF power of 50 W, a low working pressure of 4 mTorr, and an oxygen ratio of 12% exhibited p-type characteristics, which included an onset voltage (Von) of-1.5 V, a saturated hole mobility of 39 cm 2 /Vs at gate-to-source voltage (VGS) = −10 V, a sub-threshold swing of 1 V/decade at VGS − Von = −0.5 V, and an on/off ratio of 1.1 × 10 2. We believe that our results can contribute to the development of p-type SnO-based TFTs with good performance.

Research paper thumbnail of The Effect of Bake Temperature on SU-8 Gate Insulator of IGZO Thin Film Transistor

Journal of the Korean Physical Society

SU-8 photoresist was applied to the gate insulator of a-IGZO TFT. The hard bake temperature of SU... more SU-8 photoresist was applied to the gate insulator of a-IGZO TFT. The hard bake temperature of SU-8 is important and was varied from 95 to 185 • C. The FTIR showed that hard-bake temperature higher than 125 • C is necessary for complete polymerization. The leakage current and breakdown voltage were improved as increasing hard bake temperatures to 155 • C. However, the crack was generated at 185 • C degrading the electrical characteristics of insulator. The SU-8 insulator was successfully applied to a-IGZO TFT where the on-off ratio was highest for hard-bake temperature of 155 • C.

Research paper thumbnail of Effects of Plasma Treatment on the Composition and Phase Changes of Sputter-Deposited SnOx Thin Films

Journal of Nanoscience and Nanotechnology

This study examined the effects of the plasma treatment of CF₄ or SF6 on the properties of tin ox... more This study examined the effects of the plasma treatment of CF₄ or SF6 on the properties of tin oxide (SnOx) thin films prepared at room temperature using a radio frequency sputtering technique. The properties of the samples were characterized by dynamic-secondary ion mass spectrometry, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Hall Effect measurements. All untreated samples showed Sn4+ and Sn2+ XPS peak area percentages of 57.6 and 34.6%, respectively, indicating a larger amount of SnO₂ phase in the samples than SnO. The samples treated with CF₄ plasma exhibited the maximum and minimum Sn4+ and Sn2+ peak areas, respectively, at a treatment time of 35 s. This was attributed to the maximum oxygen atomic percentage at 35 s and the injection of additional carbon and fluorine into the sample with increasing treatment time. On the other hand, in the case of samples treated with SF6 plasma, the Sn4+ peak area increased with increasing treatment time while the Sn2+ peak area decreased. This suggests that SnO₂ is a stronger phase for samples treated with SF6 plasma for a longer duration. Furthermore, the changes in the Sn4+ and Sn2+ peak areas of the samples treated with CF₄ plasma were much larger than those of the samples treated with SF6 plasma, which indicates that CF₄ plasma has a larger impact on the properties of the samples. This difference in impact showed a correlation with the sharper decrease in the number of oxygen vacancies for CF₄ plasma-treated samples. These results were attributed to the introduction of additional fluorine and carbon into CF₄ plasma-treated samples compared to the SF6 plasma-treated ones. In addition, XRD showed that the plasma treatment did not affect the amorphous phase in the samples.

Research paper thumbnail of Effects of Oxygen Ratio on the Properties of Tin Oxide Thin Films Doped with Bismuth

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Research paper thumbnail of Development of oxide thin-film transistor using all spin-on-glass insulators with addition of hydrogen peroxide: Buffer, gate insulator, and interlayer dielectric

Japanese Journal of Applied Physics

A top-gate oxide thin-film transistor (TFT) with all spin-on-glass (SOG) insulators was developed... more A top-gate oxide thin-film transistor (TFT) with all spin-on-glass (SOG) insulators was developed. The SOG is based on methyl siloxane and was used for the buffer layer, gate insulator, and interlayer dielectric instead of a vacuum process. The SOG was diluted with ethanol, and a small amount of hydrogen peroxide was added. The diluted SOG was applied to top-gate amorphous indium–gallium–zinc-oxide TFTs, and the effects of the dilution and the hydrogen peroxide added were investigated. The TFTs with the optimized SOG insulators showed a mobility of 7.1 cm2/(Vs), a threshold voltage of 0.5 V, a subthreshold slope of 0.1 V/dec, and an on/off current ratio of 3.6 × 107.