Inverse Photoemission Spectroscopy of Semimagnetic Semiconductors

本文<1-x>利用反向光电子能谱（IPES）测量了Cd_ Mn_xY（Y=S，Se，Te）晶体的未占据导带，并结合新的IPES和以前的光电子能谱，揭示了Cd_Mn_xY晶体的完整电子结构。另一方面，由于Cd_<1-x>Mn_xY（Y=S、Se、Te）的电阻率为~ 100 M Ω，因此发生充电效应，从而使得测量困难。用薄膜单晶Cd_<1-x>Mn_xY（Y=S，Se，Te）可以避免这一问题。1990年：（1）为制备Cd_<1-x>Mn_xY（Y=S，Se，Te）薄膜单晶，设计并安装了热壁外延装置。(2)An制作了用于放置该装置的真空室。1991年：（1）在该室<1-x>中生长了厚度为~ 100埃的Cd_ Mn_xTe样品。（2）成功地获得了Cd_<1-x>Mn_xTe样品的IPES谱。1992：（1）<1-x>系统地研究和分析了Cd_ Mn_xTe的IPES谱随Mn浓度的变化规律。（2）光电子能谱和IPES谱的结合揭示了Cd_ Mn_xTe的完整电子结构<1-x>。此外，还首次精确测定了Mn的3d自旋交换分裂能为7.1 × 0.2eV，初步达到了预期的目的。本文的工作将推广到其它Cd_<1-x>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.