カルコパイライト系室温強磁性半導体の物性評価

本研究旨在阐明基于Mn掺杂黄铜矿型化合物（CdGeP_2: Mn）的室温铁磁半导体的物理性质。该材料的最初制备是通过在黄铜矿型化合物的大块单晶上沉积和扩散Mn来进行的。在目前的研究中。我们首先用相同的沉积扩散技术研究了ZnGeP_2: Mn，并在室温以上的居里温度下证实了其铁磁性，并阐明了CdGeP_2: Mn材料并非特有的室温铁磁性。首先，我们将Mn掺杂到另一种黄铜矿型化合物上，发现ZnGeP2:Mn在室温下也表现出铁磁性秩序，表明室温铁磁性不是黄铜矿的特征。下一个。通过东京大学小组的原位光电子能谱分析表明，表面以Mn- ge - p成分为主，磁性为0。我们还进行了从头算带计算，研究了CdGeP_2: Mn是否存在铁磁性，发现当Mn占据cd位时，其反铁磁性是稳定的。如果Mn占据了ge位，或者基体化合物存在固有缺陷，则可能产生铁磁性。如空缺和阳离子反址。然而，用沉积-扩散法很难得到均匀分布的Mn。因此，我们决定制备CdGeP_2: Mn外延薄膜晶体，并尝试使用金属有机（MO）源对未掺杂的CdGeP_2进行MBE生长。由于在抑制Cd再蒸发的条件下，所有MO气体都不能分解，因此尽管反复努力，但没有发生沉积。采用Knudesen熔池为固体源提供Cd和Ge，通过热裂解叔丁基膦（TBP）为MO气体提供P_2。只有CdGeP_2的多晶薄膜，其存在已被光致发光和拉曼测量证实。在研究CdGeP_2的同时，我们进行了MnGeP_2薄膜的生长和表征。理论计算预测了它的存在。通过XRD实验证实了黄铜矿型MnGeP_2薄膜的外延生长。利用SQUID磁强计进行磁测量，发现这些薄膜在室温下具有铁磁性。其起源仍在研究中。少

This study was planned to elucidate the physical properties of the room-temperature ferromagnetic semiconductors based on Mn-doped chalcopyrite-type compounds such as CdGeP_2: Mn.Initially preparation of this material was carried out by deposition and diffusion of Mn on to the bulk single crystal of chalcopyrite-type compounds.In the present study. we first studied ZnGeP_2: Mn using the same deposition-diffusion technique and confirmed ferromagnetism with Curie temperature above room temperature and elucidated that the room temperature ferromagnetism is not peculiar to the CdGeP_2: Mn material. First we performed Mn-doping on to another chalcopyrite-type compound and found that ZnGeP2:Mn shows also a ferromagnetic order at room temperature, indicating room-temperature ferromagnetism is not characteristic of. Next. it is elucidated through an in-situ photoelectron spectroscopy of University of Tokyo group that the surface region is dominated by Mn-Ge-P composition and the magnetism is o … More riginated * a deep DMS layer in which substituted Mn is divalent.We also performed ab-initio band calculation and investigated whether ferrornagnetism appear in CdGeP_2: Mn and found although antiferromagnetism is stable if Mn occupies Cd-site. ferrornagnetism is possible if Mn occupies Ge-site or the host compound possesses intrinsic defects. such as vacancies and cation anti-sites.However it was difficult to get a homogeneous distribution of Mn by the deposition-diffusion method. So we decided to fabricate thin epitaxial film crystals of CdGeP_2: Mn To stall with we attempted MBE growth of undoped CdGeP_2 using metal organic (MO) sources for all the three constituent elements. In spite of repeated efforts no deposition occurred because all the MO gas spices cannot be decomposed at the condition at which re-evaporation of Cd is suppressed. We supplied Cd and Ge by solid sources using Knudesen effusion cells and P_2 as MO gas by thermally cracking tertiary butyl phosphine (TBP). Only polycrystalline films of CdGeP_2 an existence of which has been confirmed by photoluminescence and Raman measurements.In parallel with the research of CdGeP_2 we carried out growth and characterization of MnGeP_2 thin films. which has been predicted to exist by theoretical calculation. As a result we confirmed epitaxial growth of chalcopyrite type MnGeP_2, thin films by XRD experiments. Magnetic measurements using SQUID magnetometer revealed ferromagnetism at room temperature in these films. origin of which is still under study. Less