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Kim, Ilsoo,Lee, Ki-Young,Kim, Ungkil,Park, Yong-Hee,Park, Tae-Eon,Choi, Heon-Jin Springer 2010 Nanoscale research letters Vol.5 No.10
<P>We report on bifurcate reactions on the surface of well-aligned Si<SUB>1−<I>x</I></SUB>Ge<SUB><I>x</I></SUB> nanowires that enable fabrication of two different coaxial heterostructure nanowires. The Si<SUB>1−<I>x</I></SUB>Ge<SUB><I>x</I></SUB> nanowires were grown in a chemical vapor transport process using SiCl<SUB>4</SUB> gas and Ge powder as a source. After the growth of nanowires, SiCl<SUB>4</SUB> flow was terminated while O<SUB>2</SUB> gas flow was introduced under vacuum. On the surface of nanowires was deposited Ge by the vapor from the Ge powder or oxidized into SiO<SUB>2</SUB> by the O<SUB>2</SUB> gas. The transition from deposition to oxidation occurred abruptly at 2 torr of O<SUB>2</SUB> pressure without any intermediate region and enables selectively fabricated Ge/Si<SUB>1−<I>x</I></SUB>Ge<SUB><I>x</I></SUB> or SiO<SUB>2</SUB>/Si<SUB>1−<I>x</I></SUB>Ge<SUB><I>x</I></SUB> coaxial heterostructure nanowires. The rate of deposition and oxidation was dominated by interfacial reaction and diffusion of oxygen through the oxide layer, respectively.</P>
Structural and chemical characterization of Mn doped GaN nanowires by X-ray absorption spectroscopy.
Seong, Han-Kyu,Kim, Ungkil,Kim, Myoung-Ha,Lee, Hyun-Hwi,Lee, Dong-Ryeol,Kim, Jae-Young,Choi, Heon-Jin American Scientific Publishers 2009 Journal of Nanoscience and Nanotechnology Vol.9 No.11
<P>We report on structural chemical state of doped Mn atoms in single crylstalline Mn doped GaN nanowires by X-ray absorption spectroscopy. Anomalous X-ray scattering and K-edge X-ray absorption fine structure measurement make it clear that Mn atoms substitute the Ga sites and they largely take part in the wurtzite network of host GaN. X-ray absorption and X-ray magnetic circular dichroism spectra at Mn L(2,3)-edges show that doped Mn has local magnetic moment and the electronic configuration of the doped Mn is mainly 3d(5) component. The structural and chemical states of the doped Mn atoms imply that they ascribe to the observed ferromagnetism in these diluted magnetic semiconductor nanowires.</P>
DILUTED MAGNETIC SEMICONDUCTOR NANOWIRES
최헌진,HAN-KYU SEONG,UNGKIL KIM 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2008 NANO Vol.3 No.1
An idea for simultaneously manipulating spin and charge in a single semiconductor medium has resulted in the development of diluted magnetic semiconductors (DMSs), which exhibits surprisingly room temperature ferromagnetic signatures despite having controversial ferromagnetic origin. However, achievement of truly room temperature ferromagnetism by carrier mediation is still the subject of intense research to develop the practical spin-based devices. Nanowires with one-dimensional nanostructure, which offers thermodynamically stable features and typically single crystalline and defect free, have a number of advantages over thin films with respect to studying ferromagnetism in DMSs. This review focuses primarily on our works on GaN-based DMS nanowires, i.e., Mn-doped GaN, Mn-doped AlGaN and Cu-doped GaN nanowires. These DMS nanowires have room temperature ferromagnetism by the local magnetic moment of doping elements that are in a divalent state and in tetrahedralcoordination, thus substituting Ga in the wurtzite-type network structure of host materials. Importantly, our evidences indicate that the magnetism is originated from the ferromagnetic interaction driven by the carrier. These outcomes suggest that nanowires are ideal building blocks to address the magnetism in DMS due to their thermodynamic stability, single crystallinity, free of defects and free standing nature from substrate. Nanowires themselves are ideal building blocks for nanodevices and, thus, it would also be helpful in developing DMS-based spin devices.