The long-range magnetism observed in group-V tellurides quintuple layers is the only working example of carrierfree dilute magnetic semiconductors(DMS),whereas the physical mechanism is unclear,except the speculation ...The long-range magnetism observed in group-V tellurides quintuple layers is the only working example of carrierfree dilute magnetic semiconductors(DMS),whereas the physical mechanism is unclear,except the speculation on the band topology enhanced van Vleck paramagnetism.Based on DFT calculations,we find a stable longrange ferromagnetic order in a single quintuple layer of Cr-doped Bi_(2)Te_(3) or Sb_(2)Te_(3),with the dopant separation more than 9?.This configuration is the global energy minimum among all configurations.Different from the conventional super exchange theory,the magnetism is facilitated by the lone pair derived anti-bonding states near the cations.Such anti-bonding states work as stepping stones merged in the electron sea and conduct magnetism.Further,spin orbit coupling induced band inversion is found to be insignificant in the magnetism.Therefore,our findings directly dismiss the common misbelief that band topology is the only factor that enhances the magnetism.We further demonstrate that removal of the lone pair derived states destroys the long-range magnetism.This novel mechanism sheds light on the fundamental understanding of long-range magnetism and may lead to discoveries of new classes of DMS.展开更多
Dopants and defects are important in semiconductor and magnetic devices. Strategies for controlling doping and defects have been the focus of semiconductor physics research during the past decades and remain critical ...Dopants and defects are important in semiconductor and magnetic devices. Strategies for controlling doping and defects have been the focus of semiconductor physics research during the past decades and remain critical even today. Co-doping is a promising strategy that can be used for effectively tuning the dopant populations, electronic properties, and magnetic properties. It can enhance the solubility of dopants and improve the stability of desired defects. During the past 20 years, significant experimental and theoretical efforts have been devoted to studying the characteristics of co-doping. In this article, we first review the historical development of co-doping. Then, we review a variety of research performed on co-doping, based on the compensating nature of co-dopants. Finally, we review the effects of contamination and surfactants that can explain the general mechanisms of co-doping.展开更多
基金Supported by Chinese University of Hong Kong(CUHK)under Grant No 4053084University Grants Committee of Hong Kong under Grant No 24300814the Start-up Funding of CUHK
文摘The long-range magnetism observed in group-V tellurides quintuple layers is the only working example of carrierfree dilute magnetic semiconductors(DMS),whereas the physical mechanism is unclear,except the speculation on the band topology enhanced van Vleck paramagnetism.Based on DFT calculations,we find a stable longrange ferromagnetic order in a single quintuple layer of Cr-doped Bi_(2)Te_(3) or Sb_(2)Te_(3),with the dopant separation more than 9?.This configuration is the global energy minimum among all configurations.Different from the conventional super exchange theory,the magnetism is facilitated by the lone pair derived anti-bonding states near the cations.Such anti-bonding states work as stepping stones merged in the electron sea and conduct magnetism.Further,spin orbit coupling induced band inversion is found to be insignificant in the magnetism.Therefore,our findings directly dismiss the common misbelief that band topology is the only factor that enhances the magnetism.We further demonstrate that removal of the lone pair derived states destroys the long-range magnetism.This novel mechanism sheds light on the fundamental understanding of long-range magnetism and may lead to discoveries of new classes of DMS.
文摘Dopants and defects are important in semiconductor and magnetic devices. Strategies for controlling doping and defects have been the focus of semiconductor physics research during the past decades and remain critical even today. Co-doping is a promising strategy that can be used for effectively tuning the dopant populations, electronic properties, and magnetic properties. It can enhance the solubility of dopants and improve the stability of desired defects. During the past 20 years, significant experimental and theoretical efforts have been devoted to studying the characteristics of co-doping. In this article, we first review the historical development of co-doping. Then, we review a variety of research performed on co-doping, based on the compensating nature of co-dopants. Finally, we review the effects of contamination and surfactants that can explain the general mechanisms of co-doping.
