• Journal of the Korean Magnetics Society
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• v.20 no.6
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• pp.207-211
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• 2010

We have investigated the magnetoresistance effect in $Cr_5S_6$ single crystals prepared by vapor transport method. Room temperature X-ray diffraction (XRD) study reveals the phase formation of the single crystals with trigonal crystal structure. The magnetization was measured as a function of temperature (5 K~400 K) and applied magnetic field (0.1 T and 5 T). The magnetization curve as a function of temperature reveals the two transition states of $Cr_5S_6$: one from antiferromagnetic to ferrimagnetic state at ~150 K and the other from ferrimagnetic to paramagnetic state at ~300 K. Temperature dependent resistivity at 0 T and 5 T magnetic field shows the metallic behavior, showing the transition from antiferromagnetic to ferrimagnetic state at ~150 K. Magnetic field dependence of magnetization was measured at four fixed temperatures viz. 100 K, 150 K, 200 K, and 300 K. It is observed that at 200 K and 300 K it shows well M-H hysteresis behavior, whereas at 100 K and 150 K it shows non-hysteretic nature. A negative magnetoresistance (MR) of -2% is observed at 5 T for $Cr_5S_6$ single crystal at 150 K, near the antiferromagnetic transition temperature.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.158-158
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• 2003

수평 전기로에서 CuGaTe2 다결정을 합성하여 HWE 방법으로 CuGaTe2 단결정 박막을 반절연성 GaAs(100) 위에 성장하였다. CuGaTe2 단결정 박막은 증발원과 기판의 온도를 각각 67$0^{\circ}C$, 41$0^{\circ}C$로 성장하였다. 이때 단결정 박막의 결정성이 10K에서 측정한 광발광 스펙트럼은 954.5nm (1.2989eV) 근처에서 exciton emission 스펙트럼이 가장 강하게 나타났으며, 또한 이중결정 X-선 요동곡선(DCRC)의 반폭치(FWHM)도 139arcsec로 가장 작게 측정되어 최적 성장 조건임을 알 수 있었다. Hall 효과는 van der Paw방법에 의해 측정되었으며, 온도에 의존하는 운반자 농도와 이동도는 293K에서 각각 8.72$\times$$10^{23}$개/㎥, 3.42$\times$$10^{-2}$$m^2$/V.s였다. 상온에서 CuGaTe2 단결정 박막의 광흡수 특성으로부터 에너지 띠간격이 1.22 eV였다 Band edge에 해당하는 광전도도peak의 온도 의존성은 Varshni 관계식으로 설명되었으며, Varshni 관계식의 상수값은 Eg(0) = 1.3982 eV, $\alpha$= 4.27$\times$$10^{-4}$ eV/K, $\beta$= 265.5 K로 주어졌다. CuGaTe2 단결정 박막의 광전류 단파장대 봉우리들로부터 10K에서 측정된 $\Delta$cr (crystal Field splitting)은 0.0791eV, $\Delta$s.o (spin orbit coupling)는 0.2463eV였다. 10K에서 광발광 봉우리의 919.8nm (1.3479eV)는 free exciton(Ex), 954.5nm (1.2989eV)는 donor-bound exciton 인 I2(DO,X)와 959.5nm (1.2921eV)는 acceptor-bound exciton 인 I1(AO,X) 이고, 964.6nm(1.2853eV)는 donor-acceptor pair(DAP) 발광, 1341.9nm (0.9239eV)는 self activated(SA)에 기인하는 광발광 봉우리로 고찰되었다.

• Journal of Sensor Science and Technology
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• v.10 no.6
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• pp.328-337
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• 2001

The stochiometric mix of evaporating materials for the $CdGa_2Se_4$ single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films, $CdGa_2Se_4$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $630^{\circ}C$ and $420^{\circ}C$, respectively. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of $CdGa_2Se_4$ single crystal thin films measured from Hall effect by van der Pauw method are $8.27{\times}10^{17}cm^{-3}$, $345\;cm^2/V{\cdot}s$ at 293 K, respectively. From the photocurrent spectrum by illumination of perpendicular light on the c-axis of the $CuInSe_2$ single crystal thin film, we have found that the values of spin orbit splitting ${\Delta}So$ and the crystal field splitting ${\Delta}Cr$ were 106.5 meV and 418.9 meV at 10 K, respectively. From the photoluminescence measurement on $CdGa_2Se_4$ single crystal thin film, we observed free excition ($E_x$) existing only high quality crystal and neutral bound exiciton ($D^{\circ}$, X) having very strong peak intensity. Then, the full-width-at -half-maximum(FWHM) and binding energy of neutral donor bound excition were 8 meV and 13.7 meV, respectivity. By Haynes rule, an activation energy of impurity was 137 meV.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.6
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• pp.425-433
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• 2000

The stochiometric mix of evaporating materials for the $CuGaTe_2$single crystal thin films was prepared from horizontal furnance. Using extrapolation method of X-ray diffraction patterns for the $CuGaTe_2$polycrystal, it was found tetragonal structure whose lattice constant $a_0 and c_0$ were 6.025 $\AA$ and 11.931 $\AA$, respectively. To obtain the single crystal thin films, $CuGaTe_2$mixed crystal was deposited on throughly etched semi-insulator GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $670^{\circ}C$ and $410^{\circ}C$ respectively, and the thickness of the single crystal thin films is 2.1$\mu\textrm{m}$. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). Hall effect on this sample was measured by the method of van der Pauw and studied on carrier density and mobility dependence on temperature. The carrier density and mobility of $CuGaTe_2$single crystal thin films deduced from Hall data are $8.72{\times}10{23}$개 $\textrm m^3$, $3.42{\times}10^{-2}$ $\textrm m^2$/V.s at 293K, respectively. From the photocurrent spectrum by illumination of perpendicular light on the c-axis of the $CuGaTe_2$single crystal thin film, we have found that the values of spin orbit coupling $\Delta$s.o and the crystal field splitting $\Delta$cr were 0.0791 eV and 0.2463 eV at 10 K, respectively. From the PL spectra at 10 K, the peaks corresponding to free bound excitons and D-A pair and a broad emission band due to SA is identified. The binding energy of the free excitons are determined to be 0.0470 eV and the dissipation energy of the donor-bound exciton and acceptor-bound exciton to be 0.0490 eV, 0.0558 eV, respectively.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.2
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• pp.211-220
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• 1998

The stochiometric composition of $AgGaS_2$polycrystal source materials for the single crystal thin films were prepared from horizontal furnace. From the extrapolation method of X-ray diffraction patterns, it was found that the polycrystal $AgGaS_2$has tetragonal structure of which lattice constant $a_0\;and \;c_0$ were 5.756 $\AA$ and 10.305 $\AA$, respectively. $AgGaS_2$single crystal thin film was deposited on throughly etched GaAs(100) substrate from mixed crystal $AgGaS_2$by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $590^{\circ}C$ and $440^{\circ}C$ respectively, and the growth rate of the single crystal thin films was about 0.5 $mu \textrm{m}$/h. The crystallinity of the grown single crystal thin films was investigated by the DCRC (double crystal X-ray diffraction rocking curve). The optical energy gaps were found to be 2.61 eV for $AgGaS_2$single crystal thin films at room temperature. The temperature dependence of the photocurrent peak energy is well explained by the Varshni equation, then the constants in the Varshni equation are given by${\Alpha};=;8.695{\times}10^{-4};eV/K,and;{\beta};=;332;K$. from the photocurrent spectra by illumination of polarized light of the $AgGaS_2$single crystal thin film, we have found that crystal field splitting $\Delta$Cr was 0.28 eV at 20 K. From the PL spectra at 20 K, the peaks corresponding to free and bound excitons and a broad emission band due to D-A pairs are identified. The binding energy of the free excitons are determined to be 0.2676 eV and 0.2430 eV and the dissociation energy of the bound excitons to be 0.4695 eV.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.5
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• pp.217-224
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• 2008

A stoichiometric mixture of evaporating materials for $ZnIn_2Se_4$ single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, $ZnIn_2Se_4$ 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 $400^{\circ}C$, respectively. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of $ZnIn_2Se_4$ single crystal thin films measured from Hall effect by van der Pauw method are $9.41\times10^{16}cm^{-3}$ and $292cm^2/v{\cdot}s$ at 293 K, respectively. The temperature dependence of the energy band gap of the $ZnIn_2Se_4$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=1.8622eV-(5.23\times10^{-4}eV/K)T^2/(T+775.5K)$. The crystal field and the spin-orbit splitting energies for the valence band of the $ZnIn_2Se_4$ have been estimated to be 182.7 meV and 42.6 meV, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the ${\Delta}so$ definitely exists in the ${\Gamma}_5$ states of the valence band of the $ZnIn_2Se_4/GaAs$ epilayer. The three photo current peaks observed at 10 K are ascribed to the $A_{1}-$, $B_{1}-exciton$ for n = 1 and $C_{27}-exciton$ peaks for n = 27.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.3
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• pp.189-198
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• 2000

The stochiometric mixture of evaporating materials for the $CuGaSe_2$single crystal thin films were prepared from horizontal furnace. Using extrapolation method of X-ray diffraction patterns for the polycrystal $CuGaSe_2$, it was found tetragonal structure whose lattice constant $a_0}$ and $c_0$ were 5.615 $\AA$ and 11.025 $\AA$, respectively. To obtains the single crystal thin films, $CuGaSe_2$mixed crystal was deposited on throughly etched GaAs(100) by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $610^{\circ}C$ and $450^{\circ}C$ respectively, and the growth rate of the single crystal thin films was about 0.5$\mu\textrm{m}$/h. The crystalline structure of single crystal thin films was investigated by the double crystal X-ray diffraction (DCXD). Hall effect on this sample was measured by the method of van der Pauw and studied on carrier density and mobility depending on temperature. From Hall data, the mobility was likely to be decreased by pizoelectric scattering in the temperature range 30 K to 150 K and by polar optical scattering in the temperature range 150 K to 293 K. The optical energy gaps were found to be 1.68 eV for CuGaSe$_2$sing1e crystal thin films at room temperature. The temperature dependence of the photocurrent peak energy is well explained by the Varshni equation then the constants in the Varshni equation are given by $\alpha$ = $9.615{\times}10^{-4}$eV/K, and $\beta$ = 335 K. From the photocurrent spectra by illumination of polarized light of the $CuGaSe_2$single crystal thin films. We have found that values of spin orbit coupling $\Delta$So and crystal field splitting $\Delta$Cr was 0.0900 eV and 0.2498 eV, respectively. From the PL spectra at 20 K, the peaks corresponding to free bound excitons and D-A pair and a broad emission band due to SA is identified. The binding energy of the free excitons are determined to be 0.0626 eV and the dissipation energy of the acceptor-bound exciton and donor-bound exciton to be 0.0352 eV, 0.0932 eV, respectively.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.2
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• pp.197-206
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• 1999

The stochiometric mixture of evaporating materials for the $AgInSe_2$single crystal thin films were prepared from horizontal furnace. Using extrapolation method of X-ray diffraction patterns for the $AgInSe_2$polycrystal, it was found tetragonal structure whose lattice constant $a_0$ and $C_0$ were 6.092 $\AA$ and 11.688 $\AA$, respectively. To obtain the single crystal thin films of AgInSe$_2$, the mixed crystal was deposited on thoroughly etched semi-insulator GaAs(100) substrate by HWE system. The source and substrate temperature were fixed to $610^{\circ}C$ and $450^{\circ}C$ respectively, and the thickness of the single thin films was obtained to 3.8 $\mu\textrm{m}$. The crystallization of single crystal thin films was investigated by the photoluminescence (PL) and double crystal X-ray dirrfaction (DCXD). The Hall effect was measured by the method of van der Pauw and carrier density and mobility dependence on temperature were studied. The carrier density and mobility of $AgInSe_2$single crystal thin films deduced from Hall data are $9.58{\times}10^{22} electron/m^3,\; 3.42{\times}10^{-2}m^2/V{\cdot}s$ at 293 K, respectively. From the photocurrent spectrum by illumination of perpendicular light on the c-axis of the $AgInSe_2$single crystal thin film, the spin orbit coupling $\Delta$So and the crystal field splitting $\Delta$Cr were obtained to 0.29 eV and 0.12 eV at 20 K respectively. From PL peaks measured at 20 K, 881.1 nm (1.4071 eV) and 882.4 nm (1.4051 eV) mean $E_x^U$ the upper polariton and $E_x^L$ the lower polariton of the free exciton $(E_x)$, also 884.1 nm (1.402 eV) express $I_2 peak of donor-bound exciton emission and 885.9 nm (1.3995 Ev) emerges $I_1$ peak of acceptor-bound exciton emission. In addition, the peak observed at 887.5 nm (1.3970 eV) was analyzed to be PL peak due to DAP.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.6
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• pp.283-290
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• 2013

A stoichiometric mixture of evaporating materials for $MgGa_2Se_4$ single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, $MgGa_2Se_4$ 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 $610^{\circ}C$ and $400^{\circ}C$, respectively. The crystalline structure of the single crystal thin films was investigated by double crystal X-ray diffraction (DCXD). The temperature dependence of the energy band gap of the $MgGa_2Se_4$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=2.34 eV-(8.81{\times}10^{-4}eV/K)T^2/(T+251K)$. The crystal field and the spin-orbit splitting energies for the valence band of the $MgGa_2Se_4$ have been estimated to be 190.6 meV and 118.8 meV, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the ${\Delta}so$ definitely exists in the ${\Gamma}_5$ states of the valence band of the $MgGa_2Se_4$/GaAs epilayer. The three photocurrent peaks observed at 10 K are ascribed to the $A_{1^-}$, $B_{1^-}$exciton for n = 1 and $C_{27}-exciton$ peaks for n = 27.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.230-233
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• 2004

The stochiometric mix of evaporating materials for the $CuInS_2$ single crystal thin films was prepared from horizontal furnance. Using extrapolation method of X-ray diffraction patterns for the $CuInS_2$ polycrystal, it was found tetragonal structure whose lattice constant $a_0$ and $c_0$ were $5.524\;{\AA}$ and $11.142\;{\AA}$, respectively. To obtain the single crystal thin films, $CuInS_2$ mixed crystal was deposited on throughly etched semi-insulator GaAs(100) substrate by the hot wall epitaxy (HWE) system. The source and substrate temperature were 640 t and 430 t, respectively and the thickness of the single crystal thin films was $2{\mu}m$. Hall effect on this sample was measured by the method of van dot Pauw and studied on carrier density and temperature dependence of mobility. The carrier density and mobility deduced from Hall data are $9.64{\times}10^{22}/m^3,\;2.95{\times}10^{-2}\;m^2/V{\cdot}s$ at 293 K, respectively The optical energy gaps were found to be 1.53 eV at room temperature. From the photocurrent spectrum by illumination of perpendicular light on the c - axis of the thin film, we have found that the values of spin orbit coupling splitting ${\Delta}So$ and the crystal field splitting ${\Delta}Cr$ were 0.0211 eV and 0.0045 eV at 10 K, respectively. From PL peaks measured at 10K, 807.7nm (1.5350ev) mean Ex peak of the free exciton emission, also 810.3nm (1.5301eV) expresses $I_2$ peak of donor-bound exciton emission and 815.6nm (1.5201eV) emerges $I_1$ peak of acceptor-bound exciton emission. In addition, the peak observed at 862.0nm (1.4383eV) was analyzed to be PL peak due to donor-acceptor pair(DAP).