• 제목/요약/키워드: $SrTiO_3$films

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Metal-insulator Transition in $(Sr_{0.75},\;La_{0.25})TiO_3$ Ultra-thin Films

  • Choi, Jae-Du;Choi, Eui-Young;Lee, Yun-Sang;Lee, Jai-Chan
    • 한국재료학회:학술대회논문집
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    • 한국재료학회 2011년도 추계학술발표대회
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    • pp.19.2-19.2
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    • 2011

  • The $(Sr_{0.75},\;La_{0.25})TiO_3$ (SLTO) ultra-thin films with various thicknesses have been grown on Ti-O terminated $SrTiO_3$(100) substrate using Laser-Molecular Beam Epitaxy (Laser MBE). By monitoring the in-situ specular spot intensity oscillation of reflection high energy electron diffraction (RHEED), we controlled the layer-by-layer film growth. The film structure and topography were verified by atomic force microscopy (AFM) and high resolution thin film x-ray diffraction by the synchrotron x-ray radiation. We have also investigated the electronic band structure using x-ray absorption spectroscopy (XAS). The ultra thin SLTO film exhibits thickness driven metal-insulator transition around 8 unit cell thickness when the film thickness progressively reduced to 2 unit cell. The SLTO thin films with an insulating character showed band splitting in Ti $L_3-L_2$ edge XAS spectrum which is attributed to Ti 3d band splitting. This narrow d band splitting could drive the metal-insulator transition along with Anderson Localization. In optical conductivity, we have found the spectral weight transfer from coherent part to incoherent part when the film thickness was reduced. This result indicates the possibility of enhanced electron correlation in ultra thin films.

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유도결합 플라즈마를 이용한 PST 박막의 식각 특성 (Etch Characteristics of (Pb,Sr) TiO3 Thin films using Inductively Coupled Plasma)

  • 김관하;김경태;김동표;김창일
    • 한국전기전자재료학회논문지
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    • 제16권4호
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    • pp.286-291
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    • 2003

  • (Pb,Sr)TiO$_3$(PST) thin films have attracted great interest as new dielectric materials of capacitors for Gbit dynamic random access memories. In this study, inductively coupled CF$_4$/Ar plasma was used to etch PST thin films. The maximum etch rate of PST thin films was 740 $\AA$/min at a CF$_4$(20 %)/Ar(80 %) 9as mixing ratio, an RF power of 800 W, a DC bias voltage of -200 V, a total gas flow of 20 sccm, and a chamber pressure of 15 mTorr. To clarify the etching mechanism, the residue on the surface of the etched PST thin films was investigated by X-ray photoelectron spectroscopy. It was found that Pb was mainly removed by physically assisted chemical etching. Sputter etching was effective in the etching of Sr than the chemical reaction of F with Sr, while Ti can almost removed by chemical reaction.

  • https://doi.org/10.4313/JKEM.2003.16.4.286 인용 PDF KSCI