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Temperature Dependence of Metal-Insulator Transition in Mn-Doped p-Type GaAs
Sungyoul Choi,최정용,Sunglae Cho,이용욱,Bongjun Kim,Huyntak Kim 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.3
We have successfully fabricated an epitaxial Mn-doped p-type GaAs thin film on a GaAs(001) substrate by using molecular beam epitaxy at a substrate temperature of 500 $^\circ$C. For the Mn-doped GaAs thin film with a hole concentration of $n_p \approx 2.0 \times 10^{17}$ cm$^{-3}$, an abrupt first-order metal-insulator transition (MIT) is observed at room temperature. The temperature dependence of the resistivity does not show a structural phase transition up to 420 K. The MIT temperature is controlled by applying a voltage without external hole doping. The abrupt MIT is discussed, along with breakdown.
Magnetic properties of Mn-doped Bi<sub>2</sub>Te<sub>3</sub> and Sb<sub>2</sub>Te<sub>3</sub>
Choi, Jeongyong,Choi, Sungyoul,Choi, Jiyoun,Park, Yongsup,Park, Hyun-Min,Lee, Hee-Woong,Woo, Byung-Chul,Cho, Sunglae WILEY-VCH Verlag 2004 Physica status solidi. PSS. B, Basic solid state p Vol.241 No.7
<P>We have fabricated Mn-doped Bi<SUB>2</SUB>Te<SUB>3</SUB> and Sb<SUB>2</SUB>Te<SUB>3</SUB> single crystals by the vertical gradient solidification method. The compositions and crystal structures of Bi<SUB>2−x</SUB>Mn<SUB>x</SUB>Te<SUB>3</SUB> and Sb<SUB>2−x</SUB>Mn<SUB>x</SUB>Te<SUB>3</SUB> were determined using Electron Probe Micro-Analyzer (EPMA) and powder X-ray diffraction (XRD) patterns, respectively. Both crystal structures were rhombohedral with smaller lattice constants because of the smaller atomic radius of Mn than those of Bi and Sb. Based on the magnetization measurements, Mn-doped Bi<SUB>2</SUB>Te<SUB>3</SUB> and Sb<SUB>2</SUB>Te<SUB>3</SUB> compounds have ferromagnetic ordering at T<SUB>C</SUB> = 10 and 17 K, respectively. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
Choi, Jiyoun,Choi, Jeongyong,Choi, Sungyoul,Kim, Jongphil,Cho, Sunglae Japan Institute of Metals 2015 MATERIALS TRANSACTIONS Vol.56 No.9
<P> We have grown un-doped and transition metal (V, Cr, Mn, Fe, Co, Ni, Cu)-doped Ge bulk single crystals using the vertical gradient solidification method. The electrical resistivities of V, Ni, Co, and Fe-doped Ge crystals significantly increased, 10<SUP>4</SUP>∼10<SUP>5</SUP> times, between 5 and 100 K, which were 100 times larger than that of the commercial Ge resistance temperature device (RTD). The large variation of electrical resistance at low temperature arises from decreased carrier density and mobility at low temperature. The mobility reduction at low temperature might be caused by ionized impurity scattering. </P>
Mn-doped ZnGeAs2 and ZnSnAs2 Single Crystals: Growth and Electrical and Magnetic Properties
Sungyoul Choi,최정용,John B. Ketterson,Soon Cheol Hong,Sunglae Cho,Yunki Kim 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.III
We have fabricated Mn-doped chalcopyrite ZnGeAs$_2$ and ZnSnAs$_2$ single crystals using vertical temperature gradient method. We have found out that Mn-doped ZnGeAs$_2$ and ZnSnAs$_2$ single crystals showed room-temperature ferromagnetism with Curie temperature of 333 and 329 K, respectively.