A study on the Raman spectra of Al-doped and Ga-doped ZnO ceramics

장민수,류민기,이순현,김형국,A. Onodera,S. Kojima,윤명희 한국물리학회 2009 Current Applied Physics Vol.9 No.3

AlxZn1-xO and GayZn1-yO ceramics were synthesized through a solid-state reaction technique. The crystal phase of the samples was identified by an X-ray diffraction experiment. For each sample, the electrical resistivity was determined. The Al 2-mol%-doped and Ga 0.5-mol%-doped ZnO ceramics had the lowest resistivity. Raman measurement was performed to study the doping effects in the ZnO ceramics including ZnO single crystal as a reference. The line-shape parameters, q1 and C1, at the same certain doping rate and the solubility limit of Al (2 mol%) and Ga (0.5 mol%) in ZnO ceramics, are strongly related to the each other, and that the solubility limit plays an important role. The second-order Raman peak at 1162 cm-1 of the ZnO ceramics was fitted by Fano formalism. The Fano’s fitting parameters, such as the lifetime of phonon and the degree of asymmetry degree of the second-order Raman peak changed as the amounts of dopants were varied.

Ba(Fe1-xCux)O3-y의 세라믹스와 박막의 물성 연구

김경현,장민수,류민기,박성수,조철환 한국물리학회 2004 새물리 Vol.48 No.6

Ba(Fe$_{1-x}$Cu$_x$)O$_{3-y}$ ceramics with composition ratio of x = 0, 0.15, 0.3 were prepared by using the solid-state reaction method. These ceramics were characterized by using X-ray diffraction and their electric and magnetic properites were studied. Under optimized conditions for the structural, the electrical, and the magnetical properities for these ceramics, we synthesized single-crystalline thin films of Ba(Fe$_{0.7}$Cu$_{0.3}$)O$_{3-y}$ on (100) LaAlO$_3$ substrates by usinf an RF-magnetron sputtering deposition method. The structural characterization of the films was carried out by using X-ray diffracton, and the magnetic properties were measured by using a superconducting quantum interference device. The results showed that ferromagnetism existed in the films at room temperature.

Effect of High-energy Electron Beam Irradiation on the Gate-bias Stability of IGZO TFTs

문혜지,정소현,류민기,조경익,윤의중,배병성 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.2

We explored the effects of high-energy electron beam irradiation (HEEBI) on the gate-bias and light stabilities of indium-gallium-zinc-oxide (IGZO)-based transparent thin film transistors (TTFTs). The developed TTFTs had a top gate structure, which used IGZO and Al2O3 films for the active layer and the gate dielectric, respectively. The developed TTFTs were treated with HEEBI in air at room temperature at an electron beam energy of 0.8 MeV and a dose of 1 × 1014electrons/cm2. Without the gate bias and/or light stresses, the HEEBI-treated devices showed a positive threshold voltage (Vth) shift (+Vth), suggesting that acceptor defects might have been generated by HEEBI treatment near the valence band edge. The HEEBI-treated devices also exhibited a lower +Vth, a higher negative Vth shift (.Vth), and a much lower .Vth under positive gate bias, negative gate bias, and light stresses compared to those for the HEEBI-untreated devices,respectively. These Vth instabilities were observed without significant change in the sub-threshold slope, indicating that charge trapping in the gate dielectric and/or at the active layer/dielectric interface was the dominant mechanism of the device instability.

Instability of an Amorphous Indium Gallium Zinc Oxide TFT under Bias and Light Illumination

전재홍,김진호,류민기 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.1

Bias stabilities of amorphous indium gallium zinc oxide (a-IGZO) thin film transistors (TFTs) under light illumination were examined. An unstable behavior was observed under a specific condition meditated by the polarity of the applied gate bias and the wavelength of the incident light. Under a positive gate bias stress, a-IGZO TFTs showed stable characteristics regardless of the light illumination. However, under a negative gate bias stress, a-IGZO TFTs showed a huge negative shift in the threshold voltage when illumination with light in the blue range was added. Hole trapping at the gate dielectric layer is believed to be one of the major causes of the degradation. Furthermore, a degradation in the subthreshold characteristics was simultaneously found, and could be attributed to changes in the subgap states.

Ca3V2O8의 단결정 성장과 누설전류 특성에 관한 연구

최정곤,이병세,류민기,황정훈,전병억,장민수 부산대학교 유전체물성연구소 2004 유전체 논문집 Vol.3 No.

Ca3V2O8 단결정을 Czochralski방법으로 성장시켰다. 편광현미경을 이용하여 단결정은 광학적으로 일축성 음의 결정이며 3회 회전 대칭을 갖는다는 것을 알았다. 또 결합에너지를 측정함으로써 결정 속에 들어있는 V이온의 산화수 분포비를 확인할 수 있었고, 단결정의 누설전류를 온도에 따라 조사하였다.

A Protective Layer on the Active Layer of Al-Zn-Sn-O Thin-Film Transistors for Transparent AMOLEDs

조두희,황치선,조경익,류민기,정성묵,윤성민,변준원,고박상희,양신혁,정우석 한국정보디스플레이학회 2009 Journal of information display Vol.10 No.4

Transparent top-gate Al-Zn-Sn-O (AZTO) thin-film transistors (TFTs) with an Al2O3 protective layer (PL) on an active layer were studied, and a transparent 2.5-inch QCIF+AMOLED (active-matrix organic light-emitting diode) display panel was fabricated using an AZTO TFT backplane. The AZTO active layers were deposited via RF magnetron sputtering at room temperature, and the PL was deposited via two different atomic-layer deposition (ALD)processes. The mobility and subthreshold slope were superior in the TFTs annealed in vacuum and with oxygen plasma PLs compared to the TFTs annealed in O2 and with water vapor PLs, but the bias stability of the TFTs annealed in O2 and with water vapor PLs was excellent.

불순물을 첨가한 LaFeO3 세라믹스 및 박막의 물성연구

조철환,장민수,김경현,류민기,조동현 한국물리학회 2004 New Physics: Sae Mulli Vol.48 No.6

La$_{1-x}$Sr$_x$Fe$_{1-y}$Cu$_y$O$_3$ ceramics with compositions x = 0, 0.1, and y = 0, 0.01, 0.03, 0.05, 0.1 were prepared at 1200 $^\circ$C by using a solid-solution reaction method. La$_{0.9}$Sr$_{0.1}$Fe$_{0.99}$Cu$_{0.01}$O$_3$ thin film was deposited at 800 $^\circ$C for 120 min on a SrTiO$_3$ substrate with a (100) orientation by using the sol-gel method. For both the ceramics and thin film, the electrical and the magnetic properties were investigated by measuring the resistivity and the M-H curve.the La$_{0.9}$Sr$_{0.1}$FeO$_3$ and the La$_{0.9}$Sr$_{0.1}$Fe$_{0.99}$Cu$_{0.1}$O$_3$ ceramics showed Curie temperatures of 496 $^\circ$C and 489 $^\circ$C, respectively. In the thin film, a prominent magnetic hysteresis loop was observed at 5 K and 300 K.

Effect of High-energy Electron Beam Irradiation on the Device Characteristics of IGZO-based Transparent Thin Film Transistors

문혜지,오혜란,배병성,류민기,조경익,윤의중 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.2

In this study, we investigated the effects of high-energy electron beam irradiation (HEEBI) on the device properties of indium-gallium-zinc-oxide (IGZO)-based transparent thin film transistors (TTFTs). The developed TTFTs had a top gate structure, which used IGZO and Al2O3 films for the active layer and the gate dielectric, respectively. The developed TTFTs were treated with HEEBI in air at RT at an electron beam energy of 0.8 MeV and a dose of 1 × 1014 electrons/cm2. Without the HEEBI treatment, the devices operated in depletion mode with a threshold voltage (Vth) of .11.25 V, a field-effect mobility (μFE) of 8.71 cm2/Vs, an on-off ratio (Ion/off) of 1.3 ×108 and a sub-threshold slope (SS) of 0.3 V/decade. A huge positive-shifted Vth of .1 V, a very high μFE of 420 cm2/Vs, a high Ion/off of 6.1 × 108, and a lower SS of 0.25 V/decade were achieved for the HEEBI-treated devices, suggesting that the device characteristics of the developed TTFTs were significantly improved by the HEEBI treatment. The best device characteristics, which include Ion/off of 8.1 × 108, SS of 0.25 V/decade, Vth of +1 V, μFE of 8.8 cm2/Vs, and operation in the enhancement mode without aging, were obtained for the samples that had been annealed after HEEBI treatment. On the basis of the experimental results, we believe that HEEBI treatment can be crucial to develop IGZO-based TFTs with high performance and long-term reliability. In this study, we investigated the effects of high-energy electron beam irradiation (HEEBI) on the device properties of indium-gallium-zinc-oxide (IGZO)-based transparent thin film transistors (TTFTs). The developed TTFTs had a top gate structure, which used IGZO and Al2O3 films for the active layer and the gate dielectric, respectively. The developed TTFTs were treated with HEEBI in air at RT at an electron beam energy of 0.8 MeV and a dose of 1 × 1014 electrons/cm2. Without the HEEBI treatment, the devices operated in depletion mode with a threshold voltage (Vth) of .11.25 V, a field-effect mobility (μFE) of 8.71 cm2/Vs, an on-off ratio (Ion/off) of 1.3 ×108 and a sub-threshold slope (SS) of 0.3 V/decade. A huge positive-shifted Vth of .1 V, a very high μFE of 420 cm2/Vs, a high Ion/off of 6.1 × 108, and a lower SS of 0.25 V/decade were achieved for the HEEBI-treated devices, suggesting that the device characteristics of the developed TTFTs were significantly improved by the HEEBI treatment. The best device characteristics, which include Ion/off of 8.1 × 108, SS of 0.25 V/decade, Vth of +1 V, μFE of 8.8 cm2/Vs, and operation in the enhancement mode without aging, were obtained for the samples that had been annealed after HEEBI treatment. On the basis of the experimental results, we believe that HEEBI treatment can be crucial to develop IGZO-based TFTs with high performance and long-term reliability.

Properties of IGZO Thin Films Irradiated by Electron Beams with Various Energies

정소현,배병성,유경민,류민기,조경익,윤의중 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.6

In this study, we investigated the effects of high-energy electron-beam irradiation (HEEBI) key parameters on the optical, electrical, and structural properties of indium-gallium-zinc oxide (IGZO) films grown on glass substrates at room temperature by radio frequency magnetron sputtering techniques. Hall, photoluminescence, X-ray photoelectron spectroscopy (XPS), and secondary ion mass spectroscopy measurements revealed that the <I>p</I>-type conductivity might be appeared in HEEBI treated films with high energy and dose, which was attributed to not only the formation of oxygen interstitial and zinc vacancy acceptor defects but also the reduction of hydrogen뻭elated donor defects in IGZO films due to HEEBI treatment. X-ray diffraction analyses showed the increase in the halo peak intensity at around 34?with the increase in electron-beam energy, indicating that all films prepared in this study were more crystallized with a higher energy despite their amorphous main structure.

“See-Through” Nonvolatile Memory Thin-Film Transistors Using a Ferroelectric Copolymer Gate Insulator and an Oxide Semiconductor Channel

윤성민,양신혁,변춘원,정순원,박상희,조두희,류민기,권오상,김병훈,황치선,조경익 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.52

We proposed and fabricated a transparent nonvolatile memory thin-film transistor (T-MTFT). The T-MTFT was composed of a ferroelectric copolymer gate insulator of poly(vinylidene fluoridetrifluoroethylene) [P(VDF-TrFE)] and an oxide semiconducting active channel of amorphous Al-Zn-Sn-O (AZTO). The fabrication procedures were so designed as to have both good transparency and high performances even at a low process temperature below 200 ℃. Consequently, the memory window with a gate voltage sweep of -10 to 10 V, the field-effect mobility in the linear region, the subthreshold swing, the on/off ratio, and the gate leakage current were obtained to be 8.6 V, 32.2 cm^2 V^(−1)·s^(−1), 0.45 V/dec, 10^8, and 10^(−12) A, respectively. Although the photo-response and the retention behaviors should be more improved and optimized, all these obtained characteristics were very promising for the future transparent electronics.