http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Piezoelectric properties of aluminum nitride for thin film bulk acoustic wave resonator
Kuangwoo Nam,kuangwoo Nam,Byeongju Ha,심동하,Gwangseo Park,Insang Song,Jaemoon Pak,Yunkwon Park 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.47 No.2
A film bulk acoustic wave resonator (FBAR) was fabricated by using RF-sputtered aluminum nitride (AlN) between 400 nm-thick molybdenum (Mo) bottom and top electrodes. To reduce the acoustic loss of FBARs, an air gap cavity is fabricated below the membrane by a silicon deep-etch process. The sputtered 950 nm-thick AlN film was oriented in the (002) direction. The FBARs were measured by using a HP 8510C vector network analyzer in a wide frequency range of 0.5 10.5 GHz. A resonance frequency was observed near 2 GHz as well as another, a third mode about 7 GHz. The minimum insertion loss was 0.056 dB at 1858 MHz. An equivalent circuit modeling regarding this FBAR was performed with modified Butterworth Van-Dyke (MBVD) models, wellknown piezoelectric equivalent circuit models. The calculated effective electromechanical coupling coefficient (k2 eff ) was greater than 6.59 %.lf.s
Jaemoon Pak,Junho Chang,Kuangwoo Nam,Jungsuk Lee,Jooyoung Kim,Gwangseo Park 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV
Ferroelectric Bi3:25La0:75Ti3O12 (BLT) thin lms were prepared on indium tin oxide (ITO) coated glass substrates by the pulsed-laser deposition method. ITO electrodes have previously been used as bottom electrodes for studies in optical phenomenon, or in oating gate capacitors. From this fact, the ITO layer was used as the bottom electrode and gold dots with an area of 1:77 10
ELECTRICAL CHARACTERIZATIONS OF Bi3.25La0.75Ti3O12 THIN FILMS ON THERMALLY OXIDIZED p-Si SUBSTRATES
Pak, Jaemoon,Ko, Eunjung,Baek, Jongho,Nam, Kuangwoo,Park, Gwangseo Taylor Francis 2006 Integrated ferroelectrics Vol.79 No.1
<P> A metal-ferroelectric-insulator-semiconductor (MFIS) diode was prepared using Bi3.25La0.75Ti3O12 thin films onto thermally oxidized Si substrates. Results on the electrical properties include capacitance-voltage (C-V), memory window effect and current-voltage (I-V) characteristics. C-V properties for the SiO2/Si structures showed an ideal switch from maximum to minimum capacitance exactly at zero voltage without any presence of flatband voltage difference. Such property ensures ohmic contacts of the electrodes and that the Au/SiO2/Si/Al diodes have fairly good interfacial properties. As for the MFIS-diodes, the flatband voltage difference enlarges at increasing voltages, exhibiting a memory window effect from ferroelectric polarization. The positive voltage sweep was measured to be identical at increasing bias voltages. Such unusual property may arise from the sudden increase in current density at about 0.9 V from I-V measurements.</P>
Sungmin Park,박광서,Jaemoon Pak,Kuangwoo Nam 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.III
CeO2 thin films on p-Si(100) were deposited by using Pulsed Laser Deposition(PLD) to study the structure and the electrical properties. (111) preferential orientation was observed by the X-ray diffraction -2 scan method. FWHM was increased as the deposition temperature decreased. Also, they had a granular type of grain for very well oriented films deposited at 760 C in vacuum. To investigate electrical properties, an Au/CeO2/Si/Al structure was fabricated. C-V characteristic and I-V characteristic were produced with a HP4194 impedance-gain analyzer and a Keithlely 617 electrometer. A strong increase of capacitance appeared at relatively low frequency (100 kHz), which can be explained by a frequency-dependent non-uniformity state generated at the interface between CeO2 and Si substrate. Especially, based on each C-V characteristic, VF B(flat band voltage)was slightly shifted toward negative bias, which means that fixed oxide charge and interface trapped charge exist. In addition, slight hysteretic behaviors of the C-V curve attributed to trapping effects were observed at all measured frequencies. Current density of the film showed different tendencies for positive and negative bias. The difference of current density between negative and positive bias was over 10.6 order. We will report on these electrical properties and discuss various defect states that may dominantly affect the CeO2/Si system.
Donghyun Shim,Gwangseo Park,Jaemoon Pak,Kuangwoo Nam 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.47 No.2
Pb(Zr,Ti)O3 (PZT) films with Zr/Ti ratio of 50 : 50 were prepared by spin-casting at 3000 rpm for 30 sec on Pt/Ti/SiO2/Si substrates. After standard processing procedure, three different methods of annealing were conducted at 600C : a single-step process carried out in (a) air, and (b) O2 ambient, and (c) a 2-step process carried out in air, followed by an O2 annealing process. These films were highly oriented along the (111) direction with large remnant polarization and low coercive voltage values. The films treated in O2 had relatively larger polarization values, but the 2-step-annealed films possessed lower coercive voltage. Fatigue measurements were conducted until 1 × 1010 switching cycles, resulting in abnormal switching characteristics for these films. A comparative study on the ferroelectric and fatigue properties will be emphasized.
Jaemoon Pak,Gwangseo Park,Eunjung Ko,Kuangwoo Nam 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1
A metal-ferroelectric-insulator-emiconductor (MFIS) feld-effect transistor structure has been fabricated by using ferroelectric Bi3:25La0:75Ti3O12 thin flm and thermally oxidized SiO2 insulating layer. We found that the electronic transport properties differ greatly with the different types of Si substrates (boron-doped p-type and phosphorus-doped n-type). Capacitance-voltage (C-V) curves were measured at a frequency of 1 MHz at various bias voltages, which resulted in an inverted memory window characteristic for n-type structure while an ideal clockwise loop was observed from p-type structure. These dierences in C-V measurements have been found to be reliable since current-voltage (I-V) measurements for both structures resulted in identical plots. Such a result ensures that MFIS structures prepared on n-type substrates are consistent with effects from ferroelectric polarizations.
Eunjung Ko,Gwangseo Park,Jaemoon Pak,Kuangwoo Nam 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1
Studies on the electrical properties of pulsed-laser-deposited Bi3:25La0:75Ti3O12 thin flms were conducted on thermally oxidized 8-nm- and 15-nm-SiO2-coated Si substrates. Characterizations of the ferroelectric-gated eld eect transistors (FeFET) were evaluated from measurements extracted from capacitance-voltage and current-voltage properties. It has been found that the FeFET has an inverted hysteresis property and that the characteristics from 8-nm-SiO2/Si were much more stable than those from 15-nm-SiO2/Si substrates. The memory window values showed that FeFETs with 15-nm-SiO2/Si required a higher operating voltage, considered to be a drawback in device applications. However, relatively large memory window values of 0.3 V, 2.5 V, 5.0 V, and 7.0 V were extracted at the respective bias voltages of 5 V, 7 V, 10 V, and 12 V for FeFETs made from 8-nm-SiO2/Si. The properties of FeFETs made from both substrates and the effects of reducing the insulator thickness are discussed.
Jaemoon Pak,Gwangseo Park,Jooyoung Kim,Jungsuk Lee,Junho Chang,Kuangwoo Nam 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV
Ferroelectric Bi3:25La0:75Ti3O12 (BLT) thin lms were prepared on indium tin oxide (ITO) coated glass substrates by the pulsed-laser deposition method. ITO electrodes have previously been used as bottom electrodes for studies in optical phenomenon, or in oating gate capacitors. From this fact, the ITO layer was used as the bottom electrode and gold dots with an area of 1:77 10..4 cm2 was deposited for use as the top electrode in the thin lm capacitor. The BLT lms were deposited at 400 C for 5 minutes and annealed at 650 C for 1 hour. The remnant polarization (Pr) and coercive eld (Ec) values at an applied voltage of 5 V were measured to be in the range of 14-16 C/cm2 and 90-100 kV/cm, respectively. Measurements of the fatigue test was carried out until 1 1011 cycles at an applied frequency of 500 kHz. Polarization decrease for lms on Pt/Ti/SiO2/Si(100) was not observed but for the ITO coated glass substrates, however, a slight decrease was observed at about 1109 cycles. The P-E hysteresis loops before and after the fatigue test showed a slight degradation of remnant polarization.
Jaemoon Pak,Gwangseo Park,Jungsuk Lee,Jooyoung Kim,Kuangwoo Nam 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV
Sapphire is a dielectric material with good mechanical and thermal properties, consisting of lattice constant a = 4.76 A and c = 12.99 A. We have successfully grown (Bi, La)4Ti3O12 (BLT) thin lms on Al2O3(0001) substrates by the pulsed laser deposition method. The lattice mismatch of sapphire with BLT is only 0.7 % and 4.3 % along the a- and c-axis, respectively. In order to study the growth behavior of the lm, eects of forming an intermediate layer, CeO2 (a = 5.41 A), between the sapphire substrate and BLT lm was investigated. Structural growth of CeO2 and BLT lms were characterized by X-ray diraction. It was found that at lower substrate temperatures, c-axis oriented lms were obtained, while at higher temperatures the orientation of the lm was on the (104) direction, normal to the c-plane of the substrate. Studies on the surface morphology of BLT/Al2O3 and BLT/CeO2/Al2O3 were evaluated in terms of the growth behavior of BLT lms.