Influence of the type of carrier on ferromagnetism in a Si semiconductor implanted with Cu ions

• Published in: Physical chemistry chemical physics : PCCP 2020-04, Vol.22 (15), p.7759-7768
• Main Authors: Wang, Li, Hou, Denglu, Wu, Chunfang, Shi, Yuanping, Shi, Shaohui, Gao, Weikun, Feng, Shunzhen, Liu, Yingdi, Li, Li, Ji, Denghui
• Format: Article
• Language: English
• Subjects: Copper; Density of states; Ferromagnetism; First principles; Free energy; Heat of formation; P-type semiconductors; Room temperature; Silicon
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c9cp05608d

Silicon semiconductor samples implanted with Cu ions and samples co-implanted with Cu- and N-ions were prepared by MEVVA and the Kaufman technique. None of the samples showed evidence of secondary phases. The initially n-type Si matrix, when implanted with Cu ions, changed to a p-type semiconductor, and the Cu ions existed as local Cu 2+ cations in the p-type environment. As a result, none of the Cu-implanted samples were ferromagnetic at room temperature. The co-implanted samples, on the other hand, showed room-temperature ferromagnetism because the introduction of N ions made the carrier type change from p-type to n-type which is favorable for the appearance of Cu 2+ . First principles calculations were applied to understand the experimental phenomena. The formation energy was reduced by implanting N ions, and was decreased effectively with the increase in ratio of N to Cu ions. The density of states and spin density of states indicated that the hybridization of s, p and d electrons induced ferromagnetism at 0 K. Particularly, we proposed possible exchange interactions between the Cu 2+ -N − (N 4+ )-Cu 2+ ions to explain the ferromagnetism mechanism. Possible exchange action mechanisms to explain the ferromagnetism origin. Here, the double exchange action hopped by spin-down electron as path &z.oone; and path &z.otwo;. The super exchange action hopped by spin-up electron is shown as path &z.othr;.