• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.6
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• pp.229-236
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• 2014

A stoichiometric mixture of evaporating materials for $MnAl_2S_4$ single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, $MnAl_2S_4$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperatures were $630^{\circ}C$ and $410^{\circ}C$, respectively. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The temperature dependence of the energy band gap of the $MnAl_2S_4$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=3.7920eV-5.2729{\times}10^{-4}eV/K)T^2/(T+786 K)$. In order to explore the applicability as a photoconductive cell, we measured the sensitivity (${\gamma}$), the ratio of photocurrent to dark current (pc/dc), maximum allowable power dissipation (MAPD) and response time. The results indicated that the photoconductive characteristic were the best for the samples annealed in S vapour compare with in Mn, Al, air and vacuum vapour. Then we obtained the sensitivity of 0.93, the value of pc/dc of $1.10{\times}10^7$, the MAPD of 316 mW, and the rise and decay time of 14.8 ms and 12.1 ms, respectively.

• Journal of the Korean Magnetics Society
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• v.12 no.2
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• pp.41-45
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• 2002

The low-field tunnel-type magnetoresistance (MR) properties of sol-gel derived $La_{0.7}Pb_{0.3}MnO_3(LPMO)$ thin film deposited on different substrate have been investigated. Polycrystalline thin films were fabricated by spin-coating on $SiO_2/Si(100)$ substrate and that with yttria-stabilized zirconia (YSZ) buffer layer, while c-axis-oriented thim film was grown on $LaAlO_3(001)$ (LAO) single crystal substrate. The full width half maximum (FWHM) of the rocking curve scan of LPMO/LAO film is $0.32^{\circ}$. Tunnel-type MR ratio is 0.52 % in $LPMO/SiO_2/Si$(100) film and that of $LPMO/YSZ/SiO_2/Si$(100) film is as high as 0.68 %, whereas that of LPMO/LAO(001) film is less than 0.4 % under the applied field of 500 Oe at 300 K. Well-pronounced MR hysteresis was registered with an MR peak in the vicinity of the coercive field. The low-field tunnel-type MR characteristics of thin films deposited on different substrates originates from the behavior of grain boundary properties.