Cr掺杂Si基稀磁半导体的制备及其磁学特性

Preparation and Magnetic Properties of Cr-Doped Si-Based Dilute Magnetic Semiconductors

采用Cr离子注入方法,在不同气体环境下退火制备了两种具有不同磁化率和居里温度的Cr掺杂p型(111)Si基稀磁半导体样品.利用X射线衍射(XRD)、傅立叶变换红外(FT-IR)光谱和超导量子干涉仪(SQUID)对样品的晶体结构、化学键及磁学特性的变化进行表征.实验发现,该样品在H2气中退火后,氢原子钝化了Cr离子注入时引起的样品中的Si悬挂键缺陷(形成Si—H),增加了传导电子的长程相互作用,使样品的居里温度达280 K,远高于同一条件下在Ar气中退火样品的居里温度(100 K).部分氢原子束缚了样品中的受主载流子,降低了磁化率,导致在低温区(小于50 K)H2气中退火样品的磁化强度小于在Ar气中退火样品的磁化强度.这为室温铁磁半导体的研制提供了实验依据.

The Cr-doped Si-based dilute magnetic semiconductors （DMS） with different magnetic properties were prepared by ion implantation method and annealing in argon （Ar） or hydrogen （H2）. D8 advanced X-ray diffraction （XRD）, Fourier transformed infrared （FT IR） spectroscopy and superconducting quantum interference device （SQUID） magnetometer were used to characterize the crystalline structures and the magnetic properties of the samples before and after annealing. The XRD results show that the Cr doped sample is amorphous before annealing and recovers crystalline structure after annealing. The IR analysis indicates that there are Si--H bonds in the sample annealed in H2, revealing that the atom hydro- gen can passivate the dangling bond defects in silicon, which increases the long-range interaction between conductive electrons and makes the sample have higher Curie temperature than that of the sample annealed in Ar. However, at the temperature lower than 50 K, the magnetization of the sample annealed in H2 is lower than that annealed in Ar, because some atoms of hydrogen bind up the acceptors in the sample. It is possible to increase the magnetization of the sample annealed in H2 with optimizing the technical conditions.