• 한국표면공학회지
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• 제34권5호
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• pp.421-428
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• 2001

New WC-CrN superlattice film was deposited on Si substrate (500$\mu\textrm{m}$) using cathodic arc ion plating system. The microstructure and mechanical properties of the film depend on the superlattice period (λ). In the X-ray diffraction analysis (XRD), preferred orientation of microstructure was changed according to various superlattice periods(λ). During the Transmission Electron Microscope analysis (TEM), microstructure and superlattice period (λ) of the WC - CrN superlattice film was confirmed. Hardness and adhesion of the deposited film was evaluated by nanoindentation test and scratch test, respectively. As a result of nanoindentation test, the hardness of WC - CrN superlattice film was gained about 40GPa at superlattice period (λ) with 7nm. Also residual stress with various superlattice period (λ) was measured on Si wafer (100$\mu\textrm{m}$) by conventional beam-bending technique. The residual stress of the film was reduced to a value of 0.2 GPa by introducing Ti - WC buffer layers periodically with a thickness ratio ($t_{buffer}$/$t_{buffer+superlattice}$ ). To the end, for the evaluation of oxidation resistance at the elevated temperature, CrN single layer and WC - CrN superlattice films with various superlattice periods on SKD61 substrate was measured and compared with the oxidation resistance.

• Journal of Magnetics
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• 제6권4호
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• pp.145-147
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• 2001

The effect of interface roughness between [Ni/Mn] superlattice and pinned NiFe layer on magnetoresistance (MR) of [Ni/Mn] superlattice-based spin valve films was investigated. Antiferromagnetic phase structure and interface roughness of [Ni/Mn] superlattice spin valve films were compared in the as-deposited and the annealed samples at 240$\^{C}$, respectively. Surface morphology of spin valves was substantially flattened due to the formation of the antiferromatic NiMn phase. In case of Co insertion between Cu and NiFe, the interlace roughness and MR ratio in the annealed [NiMn] superlattice and pinned NiFe/Co layer increased more than those in the annealed [Ni/Mn] superlattice and pinned NiFe layers respectively.

• 마이크로전자및패키징학회지
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• 제10권3호
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• pp.83-88
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• 2003

증착온도와 어닐링 조건에 따른 반도체-원자 초격자 구조의 광전자특성이 연구되었다. 나노결정의 Si-O 초격자 구조는 MBE 시스템에 의해 형성되었다. 다층의 Si-O 초격자 다이오드는 매우 안정한 포토루미네슨스 특성과 높은 브레이크다운 전압을 갖는 양호한 절연 특성을 나타내었다. 이러한 결과는 미래의 초고속 및 저전력 CMOS 소자에서 SOI 구조의 대체 방안으로 사용될 수 있을 뿐만 아니라, 실리콘계 광전자 소자 및 양자 전자 소자에도 응용될 수 있을 것이다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1376-1381
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• 2004

Understanding the thermal conductivity and heat transfer processes in superlattice structures is critical for the development of thermoelectric materials and optoelectronic devices based on quantum structures. $Chen^{(1)}$ developed ballistic diffusive equation(BDE) for alternatives of the Boltzmann equation that can be applied to the complex geometrical situation. In this study, a simulation code based on BDE is developed and applied to the 1-dimensional transient heat conduction across a thin film and transient 2-dimensional heat conduction across the film with heater. The obtained results are compared to the results of the $Chen^{(1)}$ and Yang and $Chen^{(1)}$. Finally, steady 2-dimensional heat conduction in the quantum dot superlattice are solved to obtain the equivalent thermal conductivity of the lattice and also compared with the experimental data from $Borca-Tasciuc^{(2)}$.

• 한국진공학회지
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• 제6권S1호
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• pp.34-42
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• 1997

Hg-Te-CdTe superlattices have received much interests over the last several years as a potential material for its applications for detecting devices and optoelectronics. We have grown the HgTe-CdTe superlattice using MBE. in our lab. We have carried out DCRC spectroscopy after growth of HgTe-CdTe superlattice with varying the superlattice periods and controlling the barrier thickness and we have that the presence of the main peak and the satellite peaks. We obtained 20 arcsec of FWHM over 100 periods of superlattice. We also note that high peak intensity shows the high quality of the sample and each layer of superlattice has abrupt interfaces. The angular separation between the main peak(m=0) and the first satellite peak(m=$\pm$1) is increased when the barrier layer thickness in superlatice layers are decreased. The separation between the first setellite peak(m=$\pm$1) and the second satellite peak(m$\pm$2) is increased similarly. The number of the satellite peak is a qualitative measure of the interfacial abruptness of the superlattice.

• Bulletin of the Korean Chemical Society
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• 제30권1호
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• pp.201-204
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• 2009

$BaTiO_3/SrTiO_3$ and $PbTiO_3/PbZrO_3$ superlattice thin films were fabricated on $Pt/Ti/SiO_2/Si$ substrate by the pulsed laser deposition process. The morphologies and physical properties of deposited films were characterized by using X-ray diffractometer, HR-SEM, and Impedance Analyzer. XRD data and SEM images of the films indicate that each layer was well deposited alternatively in the superlattice structure. The dielectric constant of $BaTiO_3/SrTiO_3$ superlattice thin film was higher than that of individual $BaTiO_3$ or $SrTiO_3$ film. Same result was obtained in the $PbTiO_3/PbZrO_3$system. The dielectric constant of a superlattice film was getting higher as the number of layer is increased.

• 한국진공학회지
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• 제11권3호
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• pp.166-170
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• 2002

$BaTiO_3$(BTO)/$SrTiO_3$(STO) 산화물 인공 초격자가 MgO(100) 단결정 기판위에 Pulsed laser deposition(PLD)법으로 증착되었다. 다층구조에서 BTO/STO 층의 적층 주기는 $BTO_{1\;unit\; cell}/STO_{1\;unit\; cell}$에서 $BTO_{125\;unit\; cell}/STO_{125 \;unit \;cell}$ 두께로 변화시켰고 초격자 전체 두께는 100 m으로 고정시켰다. X-ray 회절 결과는 다양한 주기의 BTO/STO 산화물 박막에서 초격자의 특성을 보였고 투과형 전자 현미경을 통해서 BTO와 STO의 두 층간의 계면에서 상호확산이 일어나지 않고 초격자가 잘 성장된 것을 확인하였다. 초격자의 유전율은 임계 두께 내에서 적층주기가 감소함에 따라 증가하였다. 이러한 초격자의 유전율은 낮은 주기 즉 $BTO_{2\;unit\; cell}/STO_{2\;unit\; cell}$ 주기에서 1230으로 높게 나왔으며 이러한 원인은 격자 변형(c/a ratio)에 기여된 것으로 분석되었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.391-392
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• 2012

In these days, the desire for the precise and tiny displays in mobile application has been increased strongly. Currently, laser displays ranging from large-size laser TV to mobile projectors, are commercially available or due to appear on the market [1]. In order to achieve a mobile projectors, the semiconductor laser diodes should be used as a laser source due to their size and weight. In this presentation, the continuous etch characteristics of Pd and AlGaN/GaN superlattice for the fabrication of blue laser diodes were investigated by using inductively coupled $CHF_3$ and $Cl_2$ -based plasma. The GaN laser diode samples were grown on the sapphire (0001) substrate using a metal organic chemical vapor deposition system. A Si-doped GaN layer was grown on the substrate, followed by growth of LD structures, including the active layers of InGaN/GaN quantum well and barriers layer, as shown in other literature [2], and the palladium was used as a p-type ohmic contact metal. The etch rate of AlGaN/GaN superlattice (2.5/2.5 nm for 100 periods) and n-GaN by using $Cl_2$ (90%)/Ar (10%) and $Cl_2$ (50%)/$CHF_3$ (50%) plasma chemistry, respectively. While when the $Cl_2$/Ar plasma were used, the etch rate of AlGaN/GaN superlattice shows a similar etch rate as that of n-GaN, the $Cl_2/CHF_3$ plasma shows decreased etch rate, compared with that of $Cl_2$/Ar plasma, especially for AlGaN/GaN superlattice. Furthermore, it was also found that the Pd which is deposited on top of the superlattice couldn't be etched with $Cl_2$/Ar plasma. It was indicating that the etching step should be separated into 2 steps for the Pd etching and the superlattice etching, respectively. The etched surface of stacked Pd/superlattice as a result of 2-step etching process including Pd etching ($Cl_2/CHF_3$) and SLs ($Cl_2$/Ar) etching, respectively. EDX results shows that the etched surface is a GaN waveguide free from the Al, indicating the SLs were fully removed by etching. Furthermore, the optical and electrical properties will be also investigated in this presentation. In summary, Pd/AlGaN/GaN SLs were successfully etched exploiting noble 2-step etching processes.

• 한국음향학회지
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• 제19권5호
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• pp.41-45
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• 2000

단결정 초격자 다층박막의 유효탄성계수를 표면탄성파 전파속도에 근거하는 두 가지 방법에 의하여 결정하였다. 첫째 방법은 구성층의 탄성계수로부터 초격자의 유효탄성계수를 계산하는 공식을 사용한다. 계산된 유효탄성계수로 계산한 기판 위 박막의 표면탄성파 전파속도와 선집속 초음파현미경으로 측정한 표면탄성파 전파속도를 비교하여 그 유효탄성계수를 검증한다. 둘째 방법은 선집속 초음파현미경으로 측정한 표면탄성파 전파속도 분산 데이터로부터 역산하여 초격자 다층박막의 유효탄성계수를 결정한다. 두 가지 방법을 TiN/NbN 초격자 다층박막에 적용하여 서로 잘 일치하는 결과를 얻었다.

• 대한전자공학회논문지
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• 제25권3호
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• pp.287-293
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• 1988

This paper calculates the band structure of the GaAs/(Al,Ga) As semiconductor superlttice with the interface3 grading, in consideration of different effective masses in each region. Including the effective masses, superlattice period, well and barrier widths, and the interface, the dispersion relation is derived, and the effects that the above parameters affect the subband (or miniband) structure of the superlattice and effective energy gap are investigated. It is particularly found that this case(ma<>mb<>mc) is significantly different from the same effective mass case(ma<>mb<>mc).