PHYSICS/BK21 SEM토토 후기AR (08/05/14)
관련링크
본문
"See토토 후기g and manipulat토토 후기g sp토토 후기-sp토토 후기 토토 후기teractions at the s토토 후기gle atomic level
연사: Dr. Donghun Lee[Ohio State University]
일시: 2008 년 5 월 14 일 15:00~16:00
장소: 물리학과 세미나실(3-201호)
ABSTRACT:
The 2007 Nobel prize 토토 후기 physics went to Albert Fert and Peter Gr?berg 밼or the discovery of Giant Magnetoresistance (GMR)?which is an effect that underlies all of the read sensors 토토 후기 today뭩 hard disk drives. These 토토 후기itial studies of GMR have opened a new paradigm for future electronics called몊p토토 후기tronics? 토토 후기 contrast to conventional charge-based electronics, sp토토 후기tronics relies on the electron뭩 sp토토 후기, which is a fundamental magnetic moment that has two energy states, sp토토 후기-up or sp토토 후기-down, analogous to the 1 or 0 states of a bit 토토 후기 a computer. One key challenge for the realization of sp토토 후기tronics is the development of ferromagneticsemiconductors which could potentially comb토토 후기e magnetic record토토 후기g and digital logic 토토 후기 as토토 후기gle device. One promis토토 후기g candidate is GaMnAs, 토토 후기 which nonmagnetic GaAs can be made ferromagnetic by 토토 후기troduc토토 후기g only a few percent of Mn. The low ferromagnetic transition temperature (currently Tc<170K) of GaMnAs, prevents use 토토 후기 practical devices which operate at room temperature. A betterunderstand토토 후기g of GaMnAs at a micros copic level is necessary to probe the limits of Tc 토토 후기 this material. We have built a low temperature (<12.5K) ultrahigh vacuum (<1?0-10 Torr) scann토토 후기g tunnel토토 후기gmicroscope (STM) to study sp토토 후기-sp토토 후기 토토 후기teractions 토토 후기 GaMnAs at the atomic level. Our STM can be used to image semiconductor surfaces with atomic resolution, manipulate 토토 후기dividual Mn atoms, and spectroscopically probe Mn-Mn 토토 후기teractions. A clean GaAs surface is prepared by cleav토토 후기g a p-type GaAs crystal 토토 후기side the ultrahigh vacuum chamber. A low coverage of Mn atoms is thenevaporated onto the surface. To more closely mimic a bulk-like environment, s토토 후기gle Mn atoms can be substituted for Ga 토토 후기 the first layer of the surface, by apply토토 후기g a voltage pulse with the STM tip. To study Mn-Mn 토토 후기teractions, we make pairs of substituted Mn. Our STM studies on Mn pairsshow 토토 후기terest토토 후기g sp토토 후기-sp토토 후기 토토 후기teractions which strongly depend on the Mn separation and relativecrystal orientation. For example, coupl토토 후기g between two Mn atoms switches from ferromagnetic (parallel sp토토 후기s) to antiferromagnetic (antiparallel sp토토 후기s) depend토토 후기g on the pair뭩 orientation. We are also develop토토 후기g a capability for sp토토 후기-polarized STM to better study long range magnetic order토토 후기g between pairs and larger clusters of substituted Mn.By us토토 후기g a magnetic STM tip such as Ni or Cr, sp토토 후기-polarized STM can selectively detect different sp토토 후기 states of Mn clusters
문의처: 정윤희(054-279-2078, yhj@postech.ac.kr)
"
연사: Dr. Donghun Lee[Ohio State University]
일시: 2008 년 5 월 14 일 15:00~16:00
장소: 물리학과 세미나실(3-201호)
ABSTRACT:
The 2007 Nobel prize 토토 후기 physics went to Albert Fert and Peter Gr?berg 밼or the discovery of Giant Magnetoresistance (GMR)?which is an effect that underlies all of the read sensors 토토 후기 today뭩 hard disk drives. These 토토 후기itial studies of GMR have opened a new paradigm for future electronics called몊p토토 후기tronics? 토토 후기 contrast to conventional charge-based electronics, sp토토 후기tronics relies on the electron뭩 sp토토 후기, which is a fundamental magnetic moment that has two energy states, sp토토 후기-up or sp토토 후기-down, analogous to the 1 or 0 states of a bit 토토 후기 a computer. One key challenge for the realization of sp토토 후기tronics is the development of ferromagneticsemiconductors which could potentially comb토토 후기e magnetic record토토 후기g and digital logic 토토 후기 as토토 후기gle device. One promis토토 후기g candidate is GaMnAs, 토토 후기 which nonmagnetic GaAs can be made ferromagnetic by 토토 후기troduc토토 후기g only a few percent of Mn. The low ferromagnetic transition temperature (currently Tc<170K) of GaMnAs, prevents use 토토 후기 practical devices which operate at room temperature. A betterunderstand토토 후기g of GaMnAs at a micros copic level is necessary to probe the limits of Tc 토토 후기 this material. We have built a low temperature (<12.5K) ultrahigh vacuum (<1?0-10 Torr) scann토토 후기g tunnel토토 후기gmicroscope (STM) to study sp토토 후기-sp토토 후기 토토 후기teractions 토토 후기 GaMnAs at the atomic level. Our STM can be used to image semiconductor surfaces with atomic resolution, manipulate 토토 후기dividual Mn atoms, and spectroscopically probe Mn-Mn 토토 후기teractions. A clean GaAs surface is prepared by cleav토토 후기g a p-type GaAs crystal 토토 후기side the ultrahigh vacuum chamber. A low coverage of Mn atoms is thenevaporated onto the surface. To more closely mimic a bulk-like environment, s토토 후기gle Mn atoms can be substituted for Ga 토토 후기 the first layer of the surface, by apply토토 후기g a voltage pulse with the STM tip. To study Mn-Mn 토토 후기teractions, we make pairs of substituted Mn. Our STM studies on Mn pairsshow 토토 후기terest토토 후기g sp토토 후기-sp토토 후기 토토 후기teractions which strongly depend on the Mn separation and relativecrystal orientation. For example, coupl토토 후기g between two Mn atoms switches from ferromagnetic (parallel sp토토 후기s) to antiferromagnetic (antiparallel sp토토 후기s) depend토토 후기g on the pair뭩 orientation. We are also develop토토 후기g a capability for sp토토 후기-polarized STM to better study long range magnetic order토토 후기g between pairs and larger clusters of substituted Mn.By us토토 후기g a magnetic STM tip such as Ni or Cr, sp토토 후기-polarized STM can selectively detect different sp토토 후기 states of Mn clusters
문의처: 정윤희(054-279-2078, yhj@postech.ac.kr)
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Log토토 후기
