摘要：
Magnetic semiconductors hold a very special position in the field of spintronics because they allow the effective ma-nipulations of both charge and spin. This feature is important for devices combining logic functionalities and information storage capabilities. The existing technology to obtain diluted magnetic semiconductors (DMSs) is to dope magnetic elements into traditional semiconductors. So far, the DMSs have attracted much attention, yet it remains a challenge to increasing their Curie temperatures above room temperature, particularly for those III–V-based DMSs. In contrast to the concept of doping magnetic elements into conventional semiconductors to make DMSs, here we propose to introduce non-magnetic elements into originally ferromagnetic metals/alloys to form new species of magnetic semiconductors. To demonstrate this concept, we introduce oxygen into a ferromagnetic amorphous alloy to form semiconducting thin films. All the thin films are deposited on different substrates like Si, SiO2 and quartz glass by magnetron sputtering. The structures of the deposited thin films are characterized by a JEOL transmission electron microscope operated at 200 kV. The optical transparencies of the samples are measured using Jasco V-650 UV-vis spectrophotometer. The photolumi-nescence spectra of the samples are measured using RM1000 Raman microscope. Electrical properties of the samples are measured using Physical Property Measurement System (PPMS-9, Quantum Design). Magnetic properties, i.e., magnetic moment-temperature relations, are measured using SQUID-VSM (Quantum Design). With oxygen addition increasing, the amorphous alloy gradually becomes transparent. Accompanied by the opening of bandgap, its electric conduction changes from metal-type to semiconductor-type, indicating that the inclusion of oxygen indeed mediates a metal-semiconductor transition. For different oxygen content, the resistivities of these thin films are changed by about four orders of magnitude. Notably, all of them are ferromagnetic. All the samples show anomalous Hall effect. Fur-thermore, their magnetoresistance changes from a very small positive value of about 0.09%to a negative value of about?6.3%under an external magnetic field of 6 T. Correspondingly, the amorphous structure of the thin film evolves from a single-phase amorphous alloy to a single-phase amorphous metal oxide. Eventually a p-type CoFeTaBO magnetic semi-conductor is developed, and has a Curie temperature above 600 K. The carrier density of this material is～1020 cm?3. The CoFeTaBO magnetic semiconductor has a direct bandgap of about 2.4 eV. The room-temperature photolumines-cence spectra further verify that its optical bandgap is～2.5 eV. The demonstrations of p-n heterojunctions and electric field control of the room-temperature ferromagnetism in this material reflect its p-type semiconducting character and the intrinsic ferromagnetism modulated by its carrier concentration. Our findings may pave a new way to realizing high Curie temperature magnetic semiconductors with unusual multi-functionalities.%磁性半导体兼具磁性和半导体特性,通过操控电子自旋,有望实现接近完全的电子极化,提供一种全新的导电方式和器件概念.目前磁性半导体的研究对象主要为稀磁半导体,采用在非磁性半导体中添加过渡族磁性元素使半导体获得内禀磁性的方法进行制备.但大部分稀磁半导体仅具有低温磁性,成为限制其在室温可操控电子器件中应用的瓶颈.针对这一关键科学问题,本文提出与传统稀磁半导体制备方法相反的合成思路,在磁性非晶合金中引入非金属元素诱发金属-半导体转变,使磁性非晶获得半导体电性,研制出具有新奇磁、光、电耦合特性的非晶态浓磁半导体,揭示其载流子调制磁性的内禀机理,发展出可在室温下工作的p-n结及电控磁器件.
