カルコパイライト系室温強磁性半導体の物性評価

点击翻译按钮获取中文摘要

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