Inverse Photoemission Spectroscopy of Semimagnetic Semiconductors

本研究的目的是利用反向光电子能谱(IPES)获得Cd_(1-x)&Gt；Mn_xy(Y=S，Se，Te)未被占据的导带的信息，并揭示新的IPES和以前的光电子能谱相结合的完整的电子结构。另一方面，由于Cd_1-x&Gt；Mn_xy(Y=S，Se，Te)的电阻率为-100MOMEGA，存在充电效应，给测量带来困难。用Cd_1-x&Gt；Mn_xy(Y=S，Se，Te)薄膜单晶可以避免这样的问题。1990年：(1)为了制备Cd_(1-x)Gt；Mn_xY(Y=S，Se，Te)薄膜单晶，设计并安装了热壁外延装置。(2)制作了放置装置的超高真空室。1991年：(1)在该制备室中生长了厚度为-100A的Cd&lt；1-x&gt；MnxTe样品。(2)成功地获得了Cd_(1-x)&Gt；Mn_xTe样品的IPES谱。1992：(1)系统地研究和分析了Cd&lt；1-x&Gt；MnxTe的IPES谱随Mn浓度的变化关系。(2)光电子能谱和光电子能谱相结合，揭示了Cd_(1-x)&Gt；Mn_xTe的完整电子结构。此外，首次准确地确定了Mn3d自旋交换分裂能为7.1×0.2 eV，基本达到了初步的目的。本工作将推广到其他Cd_1-x&Gt；Mn_xy(Y=S，Se，Te)合金。

Aim of the present study is to obtain information on unoccupied conduction bands of Cd_<1-x>Mn_xY(Y=S,Se,Te) using inverse photoemission spectroscopy (IPES) and to reveal a whole electronic structure from a combination of new IPES and previous photoemission spectra.IPES spectra are measured by monitoring intensity of the emitted ultraviolet photon-flux as a function of incident electron energy of 1-10 muA. On the other hand, since the resistivity of Cd_<1-x>Mn_xY(Y=S,Se,Te) is -100 MOMEGA, charging effect takes place and, thus, makes measurements difficult. One can avoid such a problem using thin film single crystals of Cd_<1-x>Mn_xY(Y=S,Se,Te). 1990:(1)To prepare thin film single crystals of Cd_<1-x>Mn_xY(Y=S,Se,Te), an appratus of hot wall epitaxy was designed and installed. (2)An ultrahigh vacuum chamber, in which the apparatus is placed, was made. This chamber was used as a sample preparation chamber for the IPES measurements.1991:(1)Cd_<1-x>Mn_xTe samples with -100 A thickness were grown in the preparation chamber. (2)IPES spectra of Cd_<1-x>Mn_xTe samples were successfully obtained. 1992:(1)Dependence of the IPES spectra of Cd_<1-x>Mn_xTe on the Mn concentration was systematically investigated and analyzed in detail. (2)Combination of photoemission and IPES spectra revealed a whole electronic structure of Cd_<1-x>Mn_xTe. In addition, the Mn 3d spin-exchange splitting energy was accurately determined to be 7.1*0.2 eV for the first time.Mayor part of the initial purpose has been achieved. The present work will be extended to other Cd_<1-x>Mn_xY(Y=S,Se,Te) alloys.