• Journal of Magnetics
• /
• v.19 no.2
• /
• pp.111-115
• /
• 2014

X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometry (VSM) were used to investigate the influence of Ni ions on the structural, electronic, and magnetic properties of nickel-ferrites ($Ni_xFe_{3-x}O_4$). Spinel $Ni_xFe_{3-x}O_4$ ($x{\leq}0.96$) samples were prepared as polycrystalline thin films on $Al_2O_3$ (0001) substrates, using a sol-gel method. XRD patterns of the nickel-ferrites indicate that as the Ni composition increases (x > 0.3), a structural phase transition takes place from cubic to tetragonal lattice. The XPS results imply that the Ni ions in $Ni_xFe_{3-x}O_4$ substitute for the octahedral sites of the spinel lattice, mostly with the ionic valence of +2. The minority-spin d-electrons of the $Ni^{2+}$ ions are mainly distributed below the Fermi level ($E_F$), at around 3 eV; while those of the $Fe^{2+}$ ions are distributed closer to $E_F$ (~1 eV below $E_F$). The magnetic hysteresis curves of the $Ni_xFe_{3-x}O_4$ films measured by VSM show that as x increases, the saturation magnetization ($M_s$) linearly decreases. The decreasing trend is primarily attributable to the decrease in net spin magnetic moment, by the $Ni^{2+}$ ($2{\mu}_B$) substitution for octahedral $Fe^{2+}$ ($4{\mu}_B$) site.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.06a
• /
• pp.103-103
• /
• 2009

본 논문에서는 기존의 GST(GeSbTe=2:2:5)와 비교하여 상변화 재료로서의 Ga 도핑된 $Ge_2Sb_2Te_5$의 가능성을 확인하고자 하였다. 실험에 사용된 Ga 도핑된 $Ge_2Sb_2Te_5$ 박막은 전통적 melt-quenching 방법에 의해 비정질로 제작된 벌크를 Thermal evaporation을 통하여 Si(100) 및 유리 (coming glass, 7059) 기판 위에 200nm의 두께로 증착하여 제작하였다. 각 박막의 상변화 특성은 여러 온도에서 열처리된 박막을 X-ray diffraction (XRD) 측정을 통하여 확인하였다. 각 조성 박막의 비정질-결정질 상변화속도 비교를 위하여 나노-펄스 스캐너 (nano-pulse scanner)를 사용하여 power; 1~17mW, pulse duration; 10~460ns 범위에서 박막의 상변화에 따른 반사도 차이를 측정 분석하였다. Ga의 도핑농도에 따른 전기적 특성 차이를 확인하기 위하여 4-point probe를 이용하여 박막의 면 저항을 측정하였고 또한 hall 측정을 통하여 박막의 흘 계수, 흘 농도 및 이동도를 확인하고 Ga가 상전이에 미치는 영향에 대하여 분석하였다.

• Electrical & Electronic Materials
• /
• v.9 no.4
• /
• pp.404-409
• /
• 1996

The structural and electric properties of $Y_{1-x}$YbF$_{x}$Ba$_{2}$Cu$_{3}$O$_{7-y}$(x=0.0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6) have been investigated by using XRD(X-ray diffraction), TMA(thennomechanical analysis), NMR(nuclear magnetic resonance) analysis and four probe method. $Y_{1-x}$YbF$_{x}$Ba$_{2}$Cu$_{3}$O$_{7-y}$ samples were prepared by conventional solid-state reaction method using $Y_{2}$O$_{3}$, BaCO$_{3}$, CuO and YbF$_{3}$ power. TMA and high temperature XRD results shows that orthorhombic to tetragonal phase transition occurs in the unfluorinated 1-2-3 sample while the phase change is not observed in the fluorinated 1-2-3 samples. Superconducting transition temperature(T$_{c}$) increases with increasing YbF$_{3}$ content ; T$_{c}$, of the sample reaching maximum of 102K for x=0.3, and then decreases with further increasing YbF$_{3}$ content. The structural analysis and T$_{c}$ results shows that the fluorine doping stabilize the orthorhombic phase, together with the increase in T$_{c}$.}$ c/.TEX> c/.

• Journal of the Korean Ceramic Society
• /
• v.54 no.6
• /
• pp.484-491
• /
• 2017

Chalcogenide glasses have been investigated in their thermodynamic, structural, and optical properties for application in various opto-electronic devices. In this study, the $Sb_{20}Se_{80-x}Ge_x$ with x = 10, 15, 20, and 25 were selected to investigate the glass stability according to germanium ratios. The thermal, structural, and optical properties of these glasses were measured by differential scanning calorimetry (DSC), X-ray diffraction (XRD), and UV-Vis-IR Spectrophotometry, respectively. The DSC results revealed that $Ge_{20}Sb_{20}Se_{60}$ composition showing the best glass stability theoretically results due to a lower glass transition activation energy of 230 kJ/mol and higher crystallization activation energy of 260 kJ/mol. The structural and optical analyses of annealed thin films were carried out. The XRD analysis reveals obvious results associated with glass stabilities. The values of slope U, derived from optical analysis, offered information on the atomic and electronic configuration in Urbach tails, associated with the glass stability.

• Journal of the Korean Vacuum Society
• /
• v.18 no.4
• /
• pp.245-253
• /
• 2009

For the growth optimization of InAs/GaSb (8/8-ML) strained-layer superlattice (SLS), the structure has been grown under various conditions and modes and characterized by the high-resolution x-ray diffraction (XRD) analysis. In this study, the strain modulation is induced by changing parameters and modes, such as the growth temperature, the ratio of V/III beam-equivalent-pressure (BEP), and the growth interruption (GI), and the strain variation is analyzed by measuring the angle separation of 0th-order satellite peak in XRD patterns. The XRD results reveal that the growth temperature and the V/III(Sb/Ga) ratio are major parameters to change the crystallineity and the strain modulation in SLS structures, respectively. We have observed that the SLS samples with compressive strain prepared in this study are show a transition to tensile strain with decreasing V/III(Sb/Ga) ratio, and the GI process is a sensitive factor giving rise to strain modulation. These results obtained in this study suggest that optimized growth temperature and V/III(Sb/Ga) ratio are $350^{\circ}C$ and 20, respectively, and the appropriate GI time is approximately 3 seconds just before InAs growth that the crystallineity is maximized and the strain relaxation is minimized.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.08a
• /
• pp.291.1-291.1
• /
• 2013

We examined the temperature-dependent structural and magnetic properties of HgI2 in the temperature range of 300~400 K. HgI2 is a diamagnetic material and can be used for X-ray or γ-ray detectors. DCmagnetization measurements on HgI2 showed that there is a small but distinguishable change in its diamagnetic properties near 375 K. The magnetic property change is not expected because Hg and I are known as nonmagnetic elements. X-ray diffraction (XRD) measurements revealed a structural transition in the temperature of 350~400 K. Temperature-dependent x-ray absorption fine structure (XAFS) demonstrated that the chemical valence states of both Hg and I did not changed in the temperature range of 300~400 K. However, XAFS revealed that the bond-length disorder was slightly increased in the temperature range, particularly, near Hg atoms. The structural changes of HgI2 are likely related to its diamagnetic property change. We will discuss the relation between the diamagnetic properties and local structural properties of HgI2 in detail.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.11a
• /
• pp.25-25
• /
• 2009

Zinc Oxide (ZnO) nanorod were grown on Si wafer by a thermal evaporation method at various temperatures. And their structure and optical properties were measured using Photoluminescence(PL), Scanning electron microscopy(SEM), and X-ray diffraction(XRD) analysis.

• Proceedings of the IEEK Conference
• /
• 1998.10a
• /
• pp.581-584
• /
• 1998

TiN thin films were grown on (100) Si substrate by atomic layer epitaxy at 130 - $240^{\circ}C$ using TEMAT and NH3 as precursors. Reactants were injected into the reactor in sequence of TEMAT precursor vapor pulse, N2 purging gas pulse, NH3 gas pulse and N2 purging gas pulse so that gas-phase reactions could be removed. The films were characterized by means of x-ray diffraction(XRD), 4-point probe, atomic force microscopy(AFM) and auger electron spectroscopy(AES).

• 한국신재생에너지학회:학술대회논문집
• /
• 2009.11a
• /
• pp.371-372
• /
• 2009

We have prepared and characterized CIGS nanopowder for absorber layer of photovoltaic. CIGS nanopowder were obtained at $260^{\circ}C$ for 6 hours from the reaction of $CuCl_2$, $InCl_3$, $GaCl_3$ and Se powder in solvent. The CIGS nanopowder were identified to have a typical chalcopyrite tetragonal structure by using X-ray diffraction(XRD), Inductively Coupled Plasma Auger Electron Spectroscopy (AES), Scanning Electron Microscopy(SEM).

• Proceedings of the Optical Society of Korea Conference
• /
• 2008.02a
• /
• pp.281-282
• /
• 2008

The glancing angle deposition (GLAD) technique was used to fabricate $ZrO_2$ thin films by electron-beam evaporation. The crystal structure, cross-sectional structure, surface morphology and optical properties are characterized by X-ray diffraction meter (XRD, Rigaku, Cu $K{\alpha}$ - radiation), scanning electron microscope (SEM), and spectrophotometer, respectively.