Effects of Laser-Heating on the Micro-Raman Spectra of YBa_2Cu_3O_7

Yang, In-Sang 梨花女子大學校 韓國生活科學硏究院 1992 韓國生活科學硏究院 論叢 Vol.49 No.-

Y123 고온초전도체의 전기 및 초전도 특성은 시료의 산소 함유량에 민감하게 의존하고, 이 산소 함유량은 그 시료의 열처리 과정에 크게 의존한다. 저자는 Y123 세라믹 시료에 있는 단결정의 라만분광이 측정시 사용되는 레이저의 세기에 어떻게 의존하는지를 현미경 라만분광법으로부터 알아내고자 한다. 측정에 의하면, z(xx)z￣ 편광일 경우, CuO_2 평면에 있는 산소의 B_lg 모드의 상대적 세기가 꼭지점 산소의 A_lg 모드의 세기에 비해 레이저 세기가 커짐에 따라 감소하는 경향을 보인다. 이는 레이저에 의한 열적 교란이 미세한 단결정들을 무질서하게 흐트러 놓기 때문이라고 사료된다. 혼합 편광에서의 측정은 이와 같은 사료가 맞다는 것을 보여준다. Electrical and superconducting properties of YBa_2Cu_3O_7 depend on the oxygen content sensitively, and the oxygen content, in turn, depends on the heating-history of the measured samples. The author reports the effects of laser heating to the micro-Raman spectra of single crystals embedded in polycrystalline YBa_2Cu_3O_7 pellets. From the measurements in z(xx)z￣ polarization, we found that the relative intensity of the B_lg mode of the plane oxygens to that of the A_lg mode of apical oxygens decreases rapidly as the laser power increases. The cause for this phenomenon is conjectured to be misalignment of micro-crystals due to thermal motion elevated by laser heating. The measurements in mixed polarization support this conjecture.

Monte Carlo Method for Solving Arbitrary States in Arbitrary Quantum Wells : Application to Quantum Wells under Transverse Electric Fiedls 균일 전기장하의 양자우물에의 응용

Yang, In-Sang 梨花女子大學校 韓國生活科學硏究院 1991 韓國生活科學硏究院 論叢 Vol.48 No.-

양자우물의 전자적, 광학적 특성을 연구한다는 것은 현대과학기술에서는 극히 중요하다 할 것이다. 이러한 양자계의 특성들을 이해하기 위해서는 그 계의 고유치와 고유함수를 알고 있어야 한다. 본 논문에서는 변분원리를 사용함에 있어, 몬테 카를로 기법을 써서 복잡한 퍼텐샬을 갖는 양자계의 에너지 상태를 계산하였다. 이 몬테 카를로 방법은 복잡한 양자계의 기저 에너지 상태 뿐 아니라, 들뜬 에너지 상태도 구할 수 있기 때문에 매우 유용하다 할 것이다. 이 방법을, 실용적인 응용 가능성이 많은, 횡적 전기장을 받는 양자우물의 경우에 응용하여, 이 방법의 유용성을 보이고자 한다. Electronic and optical properties of quantum wells are extremely important to understand in modern technology. In order to understand the properties of such quantum systems, the eigen values and eigen functions should be known. In this paper, Monte Carlo technique is imployed in using the variational principle to calculate not only the ground state but also the excited states of a quantum system of a complicated potential. The Monte Carlo method is very versatile in that it can solve for any excited state of any quantum system. As an illustration of its versatility, the method is applied to the case of a quantum well under transverse electric fields, which has many practical applications.

A Raman Spectroscopy Study of Disorder and Local Vibrational Modes in La0.7Sr0.3Mn1-xMxO3 (M=Fe, Co)

니구엔반민,양인상,Sung-Jin Kim 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5

We present results of Raman scattering and X-ray diffraction studies of La0.7Sr0.₃Mn₁-χMχO₃ manganites. Some Mn atoms were replaced by Fe and Co with x in the range of 0.0 { 0.75. XRD analysis of these samples indicates a change in the cell parameters with doping content. Our main focus is the Raman peak at high frequency (>630 cm-¹), which is somewhat controversial. The Raman spectra exhibit an additional high-frequency mode attributed to a local breathing vibration of the oxygen surrounding the substituent ion. The frequency and the intensity of the Raman spectra in these manganites are very sensitive to the type and the amount of the substituent. From the above results, a critical substituent content at which the structural phase changed is shown.

Boron-Purity-Dependent Raman Spectra of CaB6

Mizzou Song,양인상,조병기,J.Y. Kim 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.1

We report significant differences in the Raman spectra of two different kinds of CaB6 single crystals grown from boron with a purity of 99.9 % (3N) or 99.9999 % (6N). Our Raman spectra of CaB6 (3N) show peaks around 781 (T2g), 1141 (Eg), and 1283 cm.1 (A1g), and they are very similar to previous Raman spectra of CaB6. The Eg mode shows a characteristic double-peak feature due to an additional weak broad peak centered around 1158 cm.1. However, the Raman spectra of CaB6 (6N) show sharp peaks around 771 (T2g), 1137 (Eg), and 1266 cm.1 (A1g). The peak frequencies are down shifted as much as 17 cm.1. In addition, no additional peak feature is observed for the Eg mode so that the mode is symmetric in the case of CaB6 (6N). The X-ray powder diffraction patterns for both CaB6 (3N) and CaB6 (6N) show that the lattice parameters are essentially the same. The majority of the impurity in the 99.9 %-pure (3N) boron is C. Thus, we doped CaB6 (6N) with C, making Ca(B0.995C0.005)6, and looked for differences in the Raman spectra. The Raman spectra of Ca(B0.995C0.005)6 are nearly identical to those of CaB6 (6N), indicating that the differences between the Raman spectra of CaB6 (3N) and CaB6 (6N) are not due to a C impurity. The Raman results show that the presence of impurities, not the amount of them, is enough to trigger local symmetry breaking in CaB6. The broadening of T2g, the additional Eg2 mode and the asymmetry of A1g in CaB6 (3N) can be understood in terms of the symmetry of the arrangements of the boron octahedra lowered by local symmetry breaking.

Diamond - like Carbon 박막의 압축잔류응력에 대한 습도의존성

이영진,이광렬,양인상 한국진공학회 2004 한국진공학회 학술발표회초록집 Vol.- No.-

Q - switched Nd : YAG 레이저에 의한 YBCO박막의 비접촉식 가열방식증착

박주형,이상렬,최민경,양인상 한국진공학회 1997 한국진공학회 학술발표회초록집 Vol.- No.-

레이저 어블레이션을 이용한 금속기판상 산화물박막 증착

정영식,이상렬,김지연,양인상,박상진 한국진공학회 1997 한국진공학회 학술발표회초록집 Vol.- No.-

Effect of Cation Substitution on the Lattice Vibration and Crystal Structure of Magnetic RuSr1.9A0.1GdCu2O8 (A = Ca, Sr, and Ba) Superconductors

Tae Woo Kim,양인상,황성주 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.11

The lattice vibration and crystal structure of alkaline earth metal-substituted RuSr1.9A0.1GdCu2O8 (A = Ca, Sr, and Ba) have been investigated with micro-Raman spectroscopy. The present RuSr1.9A0.1GdCu2O8 materials show not only several weak Raman peaks corresponding to the vibrations of OCu and ORu but also strong characteristic phonon lines related to OSr vibration mode. A comparison between the frequency of OSr vibration and the bond distances of (Ru‒OSr) and (Cu‒OSr) in the present ruthenocuprates reveals that the vibration energy of OSr is mainly dependent on the bond distance of (Ru‒OSr). The peak splitting of the OSr phonon lines was observed for the unsubstituted RuSr2GdCu2O8, suggesting the existence of two different (Ru‒OSr) bond distances. Such a peak splitting caused by the appearance of low-energy shoulder reflects the presence of internal charge transfer pathway from the RuO2 plane to the superconductive CuO2 one. After the substitution of Sr with Ca or Ba, the low-energy shoulder peak of OSr vibration becomes suppressed, underscoring the depression of internal charge transfer between the RuO2 and CuO2 planes. The weakened role of RuO2 layer as charge reservoir in the RuSr1.9A0.1GdCu2O8 (A = Ca, Ba) would be responsible for the depression of Tc upon the Ca/Ba substitution.

Temperature-Dependent Raman Study of the Pyrochlore Superconductor Cd2Re2O7

J.S. Bae,양인상,D. Madrus,Hyun Kyung Ko,J. He,R. Jin,T.W. Noh,Y.S. Lee 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.5I

We present the results of Raman studies of the pyrochlore superconductor Cd2Re2O7 as a function of temperature. The overall features of the observed Raman spectra are in accord with the prediction of the factor group analysis and clearly identify two successive structural transitions, one at 200 K and the other at 120 K. New modes at 156, 325, and 411 cm.1 appear below 200 K, and peaks at 193 . 200 cm.1 and at 345 cm.1 are detected below 120 K. Moreover, the peak near 676 cm.1 shows an abrupt softening by 20 cm.1 below 200 K, but a slow hardening behavior below 120 K. On the other hand, the slope of the full width at half maximum of the peak at 230 cm.1 is found to decrease abruptly below 200 K, which appears to be parallel with the changes in the electric properties. This is indicative of the close relation between the lattice dynamics and the electronic properties. Our Raman spectra suggest that the structural changes at 200 K and 120 K in the Re- O(1) network, where O(1) is for oxygen atom at the apex of the ReO6 octahedron, is responsible for the changes in the electronic properties of the Cd2Re2O7 compound.

Nano-Sized Particles of Prussian Blue Analogue KxCoy[Fe(CN)6] and KxNiy[Fe(CN)6] : Synthesis and Their Properties

니구엔반민,Phung Kim Phu,양인상 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.6

Recently, striking effects of light irradiation on the magnetic state were reported for Prussian blue analogues AxCoy[Fe(CN)6] (A = Na, K, Rb, Cs). The physical and optical properties are dependent on the size of the particles of the measured samples. However, there have been few report on the formation of nano-sized particles of the material and the effect of size of the particles on the properties of the compounds. In this report, we investigate the effect of size of the particles on the properties of the Prussian blue analogue KxCoy[Fe(CN)6] and KxNiy[Fe(CN)6]. We present a novel synthesis method of the KxCoy[Fe(CN)6] and KxNiy[Fe(CN)6] nano-particles. The results of the Xray diffraction (XRD), scanning electron microscopy (SEM), UV-vis absorption and magnetization measurements of the compounds are presented.