• 한국결정성장학회지
• /
• 제11권6호
• /
• pp.259-263
• /
• 2001

The continuum model of transient point defect dynamics to predict the concentrations of interstitial and vacancy is established by estimating expressions for the thermophysical properties of intrinsic point defects. And the point defect distribution in a Czochralski-grown 200 mm silicon crystal and the location of oxidation-induced stacking fault ring(OiSF-ring) created during the cooling of crystals are calculated by using the numerical analysis. The purpose of this paper is to show that his approach lead to predictions that are consistent with experimental results. Predicted point defect distributions by transient point defect dynamic analysis are in good qualitative agreement with experimental data under widely and abruptly varying crystal pull rates when correlated with the position of the OiSF-ring .

• 한국재료학회지
• /
• 제8권10호
• /
• pp.969-974
• /
• 1998

Fe 계 합금의 적층결함에너지를 감소시키는 거승로 알려진 vanadium이 Fe-20Cr-1.7C-1Si합금의 미세조직과 고온 마모저항성에 미치는 영향에 대하여 조사하였다. Fe-20Cr-1.7C-1Si-xV (x=0, 1, 3, 6, 10wt.%)조성에서 오스테나이트 기지상을 유지하면서 첨기될 수 있는 V의 최대 첨가량은 약 3wt.%이었으며 오스테나이트 기지상을 갖는 합금은 상온에서 낮은 적층결함에너지와 $\gamma->\alpha$ 변형유기 상변태에 의해 페라이트 합금보다 높은 마모저항성을 보인 것으로 생각된다.$225^{\circ}C$에서 $\alpha$ 생성량도 많은 것으로 보다 V은 Fe-20Cr-1.7C-1Si 합금의 온도에 따른 적층결함에너지 증가율를 억제하고 Md온도도 증가시킴으로써 고온 마모저항성을 증가시키는 것으로 생각된다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2009년도 하계학술대회 논문집
• /
• pp.23-23
• /
• 2009

GaN-based nitride semiconductors have attracted considerable attention in high-brightness light-emitting-diodes (LEDs) and laser diodes (LDs) covering from green to ultraviolet spectral range. LED and LD heterostructures are usually grown on (0001)-$Al_2O_3$. The large lattice mismatch between $Al_2O_3$ substrates and the GaN layers leads to a high density of defects(dislocations and stacking faults). Moreover, Ga and N atoms are arranged along the polar [0001] crystallographic direction, which leads to spontaneous polarization. In addition, in the InGaN/GaN MQWs heterostructures, stress applied along the same axis can also give rise to piezoelectric polarization. The total polarization, which is the sum of spontaneous and piezoelectric polarizations, is aligned along the [0001] direction of the wurtzite heterostructures. The change in the total polarization across the heterolayers results in high interface charge densities and spatial separation of the electron and hole wave functions, redshifting the photoluminescence peak and decreasing the peak intensity. The effect of polarization charges in the GaN-based heterostructures can be eliminated by growing along the non-polar [$11\bar{2}0$] (a-axis) or [$1\bar{1}00$] (m-axis) orientation instead of thecommonly used polar [0001] (c-axis). For non-polar GaN growth on non-polar substrates, the GaN films have high density of planar defects (basal stacking fault BSFs, prismatic stacking fault PSFs), because the SFs are formed on the basal plane (c-plane) due to their low formation energy. A significant reduction in defect density was recently achieved by applying blocking layer such as SiN, AlN, and AlGaN in non-polar GaN. In this work, we were performed systematic studies of the defects in the nonpolar GaN by conventional and high-resolution transmission electron microscopy.

• 한국결정성장학회지
• /
• 제15권2호
• /
• pp.45-50
• /
• 2005

규소 표면의 기계적 손상은 산화 공정 중에 규소 표면에 여러 가지 형태의 결함들을 발생 시킨다. 규소 표면에 손상을 주는 마모 입자가 커짐에 따라 OISF보다는 etch pit의 형상이 동굴형인 선 결함(line defects)들이 많이 발생된다. 이들 결함들은 실리콘 결정을 성장시키는 단계에서 형성되는 결함들과는 상호 관련이 없다. 방향성 응고법으로 성장된 규소 결정속에 존재하는 결함들은 주로 twin과 stacking fault들이며 응고과정에서 발생이 예상되는 응력에 의한 전위는 거의 발견되지 않았다. 따라서 Czochralski 법으로 성장된 단 결정 규소뿐 아니라 방향성 응고법으로 성장된 다 결정 규소 기판도 표면의 결함들을 이용하여 extrinsic gettering을 통한 규소 결정 내부의 불순물 제거의 가능성이 높다.

• 한국초전도학회:학술대회논문집
• /
• 한국초전도학회 2003년도 High Temperature Superconductivity Vol.XIII
• /
• pp.38-38
• /
• 2003

• 비파괴검사학회지
• /
• 제30권5호
• /
• pp.444-450
• /
• 2010

본 연구에서는 전류 4단자 전위차법을 이용한 전기비저항을 측정하여 반복피로손상을 받은 구리와 구리합금의 미시적 열화를 평가하였다. 서로 매우 다른 적층결함 에너지를 갖는 구리(Cu)와 구리합금(Cu-35Zn)에 대해 반복피로손상을 가하고 이들 재료에서 발달한 전위구조와 전기비저항 간의 관계를 연구하고자 하였다. Cu는 전위셀 하부구조를 형성하였지만, Cu-35Zn 합금은 피로사이클에 따라서 전위밀도는 증가하고 평면배열의 전위구조를 형성하였다. 전기비저항은 두 재료 모두에서 피로변형 초기 단계에서 급격하게 증가하였다. 더욱이, 피로시험 후 구리는 약 7 % 그리고 구리 합금은 약 6.5 % 변하였다. 이러한 일관적인 결과들로부터, 반복적인 피로에 의해 발달한 전위 셀구조는 평면배열의 전위구조보다도 전기비저항에 매우 민감한 것으로 판단된다.

• 한국진공학회지
• /
• 제7권1호
• /
• pp.35-42
• /
• 1998

100keV $O^+$이온 빔에 의해 형성된 separation by implanted oxygen(SIMOX) silicon on insulator (SOI)의 열처리 전후의 계면 구조를 high resolution transmission electron microscopy(HRTEM)을 이용하여 관찰하였다. 실리콘 주입 온도 $550^{\circ}C$에서 ~$5\times 10^{17}\textrm{cm}^{-2}O^+$를 주입한 직후의 계면은 매우 거칠고 산화물 석출, stacking fault, coesite $SiO_2$ 상 석출물 등 여러 가지 형태의 결함들을 가지고 있었다. 반면, 이것을 $1300^{\circ}C$에서 열처리한 후의 계면은 매우 편편하고 잘 정의된 계면으로 변하였다. 열처리후의 계면은 HRTEM을 통해서 3keV$O_2^\;+$이온 빔에 의해 형성된 산화막 계면, 그리고 게이트 산화막으로 사용되는 ~ 6nm열 산화막 계면과 비교하여 볼 때 비슷한 수준의 roughness를 보여 주었다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
• /
• pp.486-487
• /
• 2007

$Bi_2Sr_2Ca_{n-1}Cu_nO_x$(n=0, 1, 2) thin films have been fabricated by co-deposition at an ultra-low growth rate using ion beam sputtering(IBS) method. The growth rates of the films was set in the region from 0.17 to 0.27 nm/min. MgO(100) was used as a substrate. In order to appreciate stable existing region of Bi 2212 phase with temperature and ozone pressure, the substrate temperature was between 655 and $820^{\circ}C$ and the highly condensed ozone gas pressure in vacuum chamber was varied between $2{\times}10^{-6}{\sim}4{\times}10^{-5}$ Torr. Bi 2212 phase appeared in the temperature range of 750 and $795^{\circ}C$ and single phase of Bi 2201 existed in the lower region than $785^{\circ}C$. Whereas, $PO_3$ dependance on structural formation was scarcely observed regardless of the pressure variation.

• 한국재료학회지
• /
• 제12권7호
• /
• pp.550-554
• /
• 2002

The effect of Mn on cavitation erosion resistance and the sliding wear resistance of Fe-base hardfacing NewAlloy was investigated. Mn is known to decrease stacking fault energy and enhance the formation of $\varepsilon$-martensite. Cavitation erosion resistance for 50 hours and sliding wear resistance for 100 cycles were evaluated by weight loss. Fe-base hardfacing NewAlloy showed more excellent cavitation erosion resistance than Mn-added NewAlloys. $\Upsilon-\alpha$' phase transformation that can enhance erosion resistance by matrix hardening occurred in every specimens. But, only in Mn free Fe-base hardfacing NewAlloy, the hardened matrix could repress the propagation of cracks that was initialed at the matrix-carbides interfaces more effectively than Mn-added NewAlloy The Mn free Fe-base hardfacing NewAlloy showed better sliding wear resistance than Mn-added alloys. Mn-addition up to 5wt.% couldn't increase the sliding wear and cavitation erosion resistance of Fe-base hardfacing alloy because it didn't make $\Upsilon\to\varepsilon$ martensite phase transformation. Therefore, it is considered that the cavitation erosion and the sliding wear resistance can be improved due to $\Upsilon\to\varepsilon$ martensite phase transformation when Mn is added more than 5wt.% in Fe-base hardfacing alloys.

• 한국세라믹학회지
• /
• 제32권12호
• /
• pp.1377-1382
• /
• 1995

A high-resolution transmission electron microscopy study on the lattice defects formed in the high energy P ion implanted silicon was carried out on an atomic level. Results show that Lomer dislocations, 60$^{\circ}$perfect dislocations, 60$^{\circ}$ dislocation dipole and extrinsic stacking fault formed in the near Rp of as-implanted specimen. In the annelaed specimens, interstitial Frank loops, 60$^{\circ}$perfect disolations, 60$^{\circ}$dislocation dipoles, stacking faults, precipitates, perfect dislocation loops and <112> rodlike defects existed exclusively near in the Rp with various annealing temperature and time. From these results, it is concluded that extended secondary defects as well as the point defect clusters could be formed without annealing. Even at low temperature annealing such as 55$0^{\circ}C$, small interstitial Frank loops could be formed and precipitates were also formed by $700^{\circ}C$ annealing. The defect band annealed at 100$0^{\circ}C$ for 1 hr could be divided into two regions depending on the distribution of the secondary defects.