Browsing by Author "Ro, CS"

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Energy-dispersive x-ray diffraction and Raman scattering of Zn1-xMnxSe bulk crystals at high pressure
(1999-06-15)
Yang, CS
;
Ro, CS
;
Chou, WC
;
Lin, CM
;
Chuu, DS
Energy-dispersive x-ray diffraction experiments were carried out to investigate the structure of phase transitions under high pressure. It was found that the zinc blende (B-3) to rock salt (B-1) phase transition pressures of Zn0.93Mn0.07Se and Zn0.76Mn0.24Se bulk crystals are found 11.8+/-1.5 and 9.9+/-0.5 GPa, respectively. The respective bulk moduli are 61.8+/-0.8 and 60.5+/-0.8 GPa. The pressure-induced zinc blende (ZB) to rock salt (RS) structure phase transition is interpreted as a signature of the semiconductor to metal transition for Zn1-xMnxSe. The above interpretation is further corroborated by the observation of the disappearance of the longitudinal optical phonon at the pressure where the ZB to RS structure transition occurs. (C) 1999 American Institute of Physics. [S0021-8979(99)05312-8].
Optical properties of Zn1-xMnxSe epilayers grown by molecular beam epitaxy
(1998-04-01)
Chou, WC
;
Ro, CS
;
Hong, DY
;
Yang, CS
;
Lin, CY
Zn1-xMnxSe (x less than or equal to 0.78) epilayers were grown on the GaAs (001) substrate with tilt angle 0, 3, 10, and 15 degrees toward [010] by the molecular beam epitaxy. The reflectivity, transmission, and photoluminescence experiments were used to measure the energy gap of the epilayers. A red shift of 4 meV was found as the substrate tilt angle increased from 0 to 15 degrees. The red shift in band gap energy is attributed to the increasing incoporation of smaller Zn ion with the increase in the kink density which results from the increase in the substrate tilt angle. In addition, the lattice vibration of the Zn1-xMnxSe (0 less than or equal to x less than or equal to 0.78) epilayers measured by the Raman scattering was found to follow the intermediate mode behavior of type Ib instead of type Ic. The force constants F-MnSe = 2.81 x 10(6) amu.cm(-2) and F-ZnSe = 3.96 x 10(6) amu.cm(-2) were obtained.