The Crystal Growth And Characterization Of An Advanced Diluted Magnetic Semiconductor Cd_1-xMn_xIn₂Te₄

A new diluted magnetic semiconductor (DMS), Cd1-xMnxIn2Te4 (x-0.1, 0.22 and 0.4), has been successfully synthesized by the Vertical Bridgman Method (VBM) for the first time. Using scanning electron microscopy, x-ray powder diffractometer, ISIS energy-dispersive spectroscopy and Leica guantitative optical microscopy, the microstructure, composition profiles of CdMnZnTe ingots were analyzed, a and 3 phases are formed at the tip. 3 and Y or 8 phases are crystallized at the end. Between them exists a pure β phase region. The different neighbouring phase-regions are seperated by a distinct interface respectively. The β phase is Cdi1-xMnxIn2Te4 with chalcopyrite structure. The application of Accelerated Crucible Rotation Technique (ACRT) in the growth process decreases the radial composition inhomogenelty while increases the axial composition variation. The infrared transmission spectra, resistivity, moblility and concentration of the charge carriers of Cd1-xMnxIn2Te4 (x=0.1, 0.22 and 0.4) have respectively been measured at room temperature. Magnetic susceptibility measurements of the crystals slices with different compositions (x=0.1, 0.22, 0.4 and 0.8) have also been carried out in the temperature range 5K≤T≤300K using a SQUID magnetometer at B=1T. The optical absorption measurements show that the value of transmittance is almost a constant in 4000-500cm-1 for each crystal. The transmittance of Cd0.9Mn0.1In2Te4 is about 61%, a little smaller than the theoretical maximum 65% of CdIn2Te4. Cd1-xMnxIn2Te4 is p-type semiconductor. The concentration of the charge carriers Np decreases, while the resistivity P and the magnetization increases with the x. The magnetic susceptibilities of Cd1-xMnxIn2Te4 (x≥0.22) obey Curie-Weiss laws x = C(x)/[T - θ(x)] in the high temperature range while the susceptibility curves show down deviation at lower temperatures (<50K). There is an antiferromagnetic interaction between Mn2+ ions and which increases with x. The exchange integral constant J1 /kB is much smaller in Cd1-xMnxIn2Te4 than that in Cd1-xMnxTe4 for the same concentration of Mn2+.