• Title/Summary/Keyword: NEXAFS

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NEXAFS study on $Ge_2Sb_2Te_5$ films

  • Jang, Mun-Hyeong;Park, Seung-Jong;Im, Dong-Hyeok;Lee, Yeon-Jin;Jo, Man-Ho;Hwang, Jeong-Nam
    • Proceedings of the Korean Vacuum Society Conference
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    • 2008.02a
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    • pp.338-338
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    • 2008

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Pile Contact Depth Effects in Rubbed Polyimide(PI) Films

  • Kim, Gi-Jeong;Gwon, Hyeok-Min;Lee, Sang-Mun;Lee, Cheol-Gu;Gwak, Mu-Seon;Kim, Bong-Su
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.02a
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    • pp.398-398
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    • 2010

  • To determine the molecular directionality of PI chains depending on rubbing condition, we measured the angle resolved near edge X-ray absorption fine structure (NEXAFS) spectra at C K-edge of the rubbed PI films. Twisted nematic mode PI (PI-TN) and in plane switching mode PI (PI-IPS) were introduced to examine the effect of rubbing conditions on the chain directionality. The average tilt angle a of the PI molecules was estimated through the measured intensity change of $C=C\;{\pi}^*$ in NEXAFS C K-edge spectrum by controlling the stage speed and the pile contact depth. After rubbing, the irregular molecular direction changed to a regular direction with a molecular tilt angle of $51.2^{\circ}$ for PI-TN and $49.6^{\circ}$ for PI-IPS at the rubbing condition of the roll speed of 1000 rpm, stage speed of 50 mm/sec, and file contact depth of 0.3 mm. The molecular tilt angle $\alpha$ was linearly decreased in the PI-TN and PI-IPS samples with increasing depth of the pile contact.

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X-Ray Absorption Spectroscopic Study of 120 MeV $Ag^{9+}$ Ion-Irradiated N-Doped ZnO Thin Films

  • Gautam, Sanjeev;Lim, Weon Cheol;Kang, Hee Kyung;Lee, Ki Soo;Song, Jaebong;Song, Jonghan;Asokan, K.;Chae, Keun Hwa
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.02a
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    • pp.315-315
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    • 2013

  • We report the electronic structure modification in the swift heavy ion (SHI) irradiated N-doped ZnO thin films prepared by RF sputtering from ZnO target in different ratio of Ar/$N_2$ gas mixture using highly pure $N_2$ gas. The different N-ZnO thin lms were then irradiated with 120 MeV Ag ion beam with different doses ranging from $1{\times}10^{11}$ to $5{\times}10^{12}$ ions/$cm^2$ and characterized by XRD and near edge X-ray absorption ne structure (NEXAFS) at N and O K-edges. The NEXAFS measurements provide direct evidence of O 2p and Zn 3d orbital hybridization and also the bonding of N ions with Zn and O ions. The minimum value of resistivity of $790{\Omega}cm$, a Hall mobility of $22cm^2V^-1s^-1$ and the carrier concentration of $3.6{\times}10^{14}cm^{-3}$ were yielded at 75% $N_2$. X-ray diffraction (XRD) measurements revealed that N-doped ZnO films had the preferential orientation of (002) plane for all samples, while crystallinity start decreasing at 32.5% $N_2$. The average crystallite size varies from 5.7 to 8.2 nm for 75% and then decreases to 7.8 nm for 80% $Ar:N_2$ ratio.

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The control of the structure and properties of tetrahedral amorphous carbon films prepared by Filtered Vacuum Arc (FVA 증착법에 의해 합성된 ta-C 박막의 구조 및 물성 제어)

  • 이철승;신진국;김종국;이광렬;윤기현
    • Journal of the Korean Vacuum Society
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    • v.11 no.1
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    • pp.8-15
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    • 2002

  • Tetrahedral amorphous carbon(ta-C) films were deposited by the filtered vacuum arc(FVA) process. The FVA process has many advantages such as high ionization ratio and the ion energy, which is suitable for dense amorphous carbon film deposition. However, the energy of the carbon ion cannot be readily controlled by manipulating the arc source parameters. In order to control the film properties in wide range, we investigated the dependence of the film properties on the substrate bias voltage. The mechanical properties and the density of the film exhibit the maximum values at about -100 V of the bias voltage. The maximum values of hardness and density were respectively 54$\pm$3 GPa and 3.6$\pm$0.4 g/㎤, which are 3 to 5 times higher than those of the films deposited by RF PACVD or ion beam process. The details of the atomic bond structure were analysed by Raman and NEXAFS spectroscopy. The change in the film properties for various bias voltages could be understood in the view of the $sp^2$ and $sp^3$ bond fraction in the deposited films.

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