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的室温铁磁半导体材料如CdGeP_2：Mn的物理性质。我们首先研究了ZnGeP_2：Mn的单晶样品，并证实了CdGeP_2：Mn材料的铁磁性，其居里温度高于室温，说明室温铁磁性不是CdGeP_2：Mn材料所特有的。首先，我们对另一种黄铜矿型化合物进行Mn掺杂，发现ZnGeP 2：Mn在室温下也显示出铁磁有序，表明室温铁磁性不是特征。下一个通过东京大学研究组的原位光电子能谱分析，阐明了表面区域主要由Mn-Ge-P组成， ...更多信息 我们还对CdGeP_2：Mn进行了abinitio能带计算，并研究了它是否具有铁磁性，发现虽然反铁磁性是稳定的，但如果Mn占据Cd位。如果Mn占据Ge位或主体化合物具有本征缺陷，则铁磁性是可能的。但采用沉积扩散法难以得到均匀分布的Mn。因此，我们决定制造CdGeP_2：Mn的外延薄膜晶体。为了停止，我们尝试使用所有三种组成元素的金属有机（MO）源来MBE生长未掺杂的CdGeP_2。尽管反复的努力，没有发生沉积，因为所有的MO气体香料不能在镉的再蒸发被抑制的条件下分解。采用Knudesen扩散池固体源提供Cd和Ge，用TBP热裂解P_2作为MO气体。光致发光和拉曼光谱测试证实了CdGeP_2薄膜的存在。通过理论计算已经预测到存在。通过XRD实验证实了MnGeP_2薄膜的外延生长。使用SQUID磁强计的磁性测量显示在室温下在这些薄膜的铁磁性。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