Heteroepitaxial Growth of In 2 0 3 on Ysz (100) Single Crystal Surface
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ABSTRACT In 20 3 films were deposited on YSZ (001) single crystal surface at 8009C at an oxygen pressure of 14 Pa by pulsed laser deposition (PLD) method. A heteroepitaxial relationship between the film and the substrate was seen in TEM photographs and X-ray diffraction measurements. The w locking curve full width of half maximum (FWHM) of the In 20 3 (004) x-ray diffraction was 0.060. Film conductivities were -10 S/cm or less, while carriers on the order of lO 8/cm 3 were generated.
INTRODUCTION Tin doped In 2 0 3 (ITO) is widely used for transparent electrodes of liquid crystal displays. In order to develop displays with a larger size and more precise patterns of pixels, improvement in electric conductivity of ITO electrodes is required. The maximum conductivity is determined by a tradeoff relationship between carrier density and mobility as a 3 21 function of tin concentration : Tin doping acts to increase carrier density up to 1 x 10 /cm while decrease mobility significantly. The mechanism of electron transport process, especially scattering process has been studied using polycrystalline sputtered films; few reports on single crystalline films are available. Tarsa et al. prepared ln 20 3 films on yttrium stabilized zirconia (YSZ) single crystal (001) surface by the PLD method at substrate temperatures between 400'C and 450'C and oxygen pressure of 1 x 10-1 Pa.') The X-ray rocking curve FWHM of the film the was 1.3', with orientation relations deduced from RHEED patterns representative of cube-on-cube texturing. Electric conductivities on the order of 2 x 103 S/cm and Hall mobility of - 50 cm 2 /Vs were reported. Taga et al. utilized molecular beam epitaxy (MBE) to deposit In 20 3 onto YSZ (100) surface at conditions of 300rC and 1 x 10-3 Pa. 2) The X-ray FWHM was as small as 0.080, and pole figure patterns revealed an excellent in-plane crystalline orientation without large angle grain boundaries. Electric conductivities of the films were not reported in the Paper. In this paper, we report use of the PLD method for In 20 3 on YSZ (001) substrate at 800'C and oxygen pressure of 14 Pa. Surface morphology, crystallinity, and electric properties of the films are studied.
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Mat. Res. Soc. Symp. Proc. Vol. 558 ©2000 Materials Research Society
EXPERIMENT The growth of 1n 20 3 films using PLD was carried out in an ultra-high- vacuum chamber with a base pressure of 1 x 10-7 Pa. Sintered bodies of In 20 3 (99.99 % pure, 98.5 % dense, Tosoh Specialty Material) were used as targets, and YSZ single crystals of 10 x 10 x 0.5 mm in size with (001) facet on top were used as substrates. Molecular oxygen gas (14 Pa) was introduced in the chamber, and the temperature of the substrate was elevated to 8009C by an IR lump. The target was ablated using 248 nm KrF excimer laser pulses at an energy density of - 4 J/cm 2/pulse to deposite ln 20 3 films on the substrate. Film thickness was measured by a stylus system (Taylor Hobson, Talystep). Surface morphology of the films was observed using an Atomic Force Microscope (AFM, S1I,
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