为了寻找新的高Tc的稀磁半导体(DMS),利用自旋局域密度泛函的第一性原理对 3d过渡金属(TM= V、Cr、Mn、Fe、Co或Ni)掺杂的II IV V2(CdGeP2 和ZnGeP2)以及I III VI2(CuGaS2 和CuGaSe2)黄铜矿半导体的电磁性质进行系统计算.结果发现:V或Cr...为了寻找新的高Tc的稀磁半导体(DMS),利用自旋局域密度泛函的第一性原理对 3d过渡金属(TM= V、Cr、Mn、Fe、Co或Ni)掺杂的II IV V2(CdGeP2 和ZnGeP2)以及I III VI2(CuGaS2 和CuGaSe2)黄铜矿半导体的电磁性质进行系统计算.结果发现:V或Cr 掺杂的 II IV V2 将出现铁磁(FM)状态,而 Mn、Fe或者 Co掺杂的 II IV V2 将出现反铁磁(AFM)状态,Ni掺杂时,DMS的磁性非常不稳定;在TM掺杂的 I III VI2 的DMS中,Cr、Mn掺杂的 CuGaS2 和 CuGaSe2将表现为FM状态,而当V、Fe、Co或Ni掺杂时,Cu(Ga,TM)S2 和Cu(Ga,TM)Se2 则表现了AFM性质.Cr掺杂的I IV V 以及 I III VI 黄铜矿半导体将可能出现较高的居里温度(Tc).展开更多
Zn1-xCoxO films were grown on glass by sol-gel spin coating process. A homogeneous and stable Zn1-xCoxO sol was prepared by dissolving zinc acetate dihydrate, cobalt acetate tetrahydrate and aluminium chloride hexahyd...Zn1-xCoxO films were grown on glass by sol-gel spin coating process. A homogeneous and stable Zn1-xCoxO sol was prepared by dissolving zinc acetate dihydrate, cobalt acetate tetrahydrate and aluminium chloride hexahydrate as solutes in solution of isopropanol and monoethanolamine. The films were postheated and vacuum annealed, and investigated for c-axis preferred orientation and electromagnetic properties. Zn1-xCoxO films with different Co concentrations were oriented well along the c-axis, especially the Zn1-xCoxO film with 10% Co(atom fraction) was highly c-axis oriented. The transmittance spectra show that Zn1-xCoxO films occur d-d transition and sp-d exchange interaction between Co2+ ions. The electrical resistivity of the films at 10% Co had the lowest value because the crystallite size became largest and the crystallinity of the c-axis was improved. X-ray photoelectron spectroscopy and alternating gradient magnetometer analyses indicated that no Co metal cluster was formed, and the ferromagnetism at room temperature appeared. The characteristics of the electrical resistivity and room temperature ferromagnetism of sol-gel derived Zn1-xCoxO films suggest a potential application of dilute magnetic semiconductor devices.展开更多
The crystallographic structures and magnetic properties of a Zn0.95Co0.05O thin film deposited on a C-sapphire substrate using a dual-beam pulsed laser deposition method were characterized. It was shown from crystallo...The crystallographic structures and magnetic properties of a Zn0.95Co0.05O thin film deposited on a C-sapphire substrate using a dual-beam pulsed laser deposition method were characterized. It was shown from crystallographic analysis that the film belongs to the wurtzite structure with the C-axis aligned with that of the substrate. Magnetic hysteresis loops were observed till up to room temperature. A small peak around 55 K was noticed on the magnetization vs. temperature curve. The corresponding temperature of the small peak is close to that of ‘the abnormal peak’ reported by X.M. Zhang et al. From the results obtained, no correlation was found between the abnormal peak and the quantum effects. The magnetic behaviors in the Zn0.95Co0.05O film cannot be explained by the ferromagnetism in diluted magnetic semiconductors. The magnetic mechanisms in ZnO-based diluted magnetic semiconductors are also discussed.展开更多
Spin ordering in a semiconductor has attracted much attention in the community of condensed matter physics. By combining ferromagnetism and the semiconducting nature, systems such as Mn-doped PbSnTe or InAs were found...Spin ordering in a semiconductor has attracted much attention in the community of condensed matter physics. By combining ferromagnetism and the semiconducting nature, systems such as Mn-doped PbSnTe or InAs were found to exhibit tunable magnetic properties responsive to an externally applied electric field. It thus holds great promises for developing novel spintronics with the tuning-knobs such as gate voltage. Conventionally, those systems are often studied in bulk forms and commonly referred to diluted magnetic semiconductor (DMS).展开更多
Zn0.90Ni0.10O nanoparticles have been synthesized by single-bath two-electrode electrodeposition at constant voltage. X-ray diffraction, UV vis and photoluminescence studies reveal that a single-phase polycrystalline ...Zn0.90Ni0.10O nanoparticles have been synthesized by single-bath two-electrode electrodeposition at constant voltage. X-ray diffraction, UV vis and photoluminescence studies reveal that a single-phase polycrystalline hcp wurtzite crystal structure of ZnO is evolved. The material consists of a large number of defects such as oxygen vacancy (Ov) and zinc interstitial (Zi). The magnetization study reveals that the sample exhibits room-temperature global ferromagnetism and the ferromagnetic ordering seems to be defect induced via bound magnetic polaron mechanism, and double exchange is also expected to have played role. Interesting optoelectronic properties have been found in the synthesized sample and the material seems to be a potential candidate to be used as a UV sensor. Such a transition metal doped ZnO based dilute magnetic semiconducting system exhibiting room-temperature ferromagnetism is likely to be first of its kind in the sense that such materials have not yet been reported to be synthesized by the simple method of electrodeposition to the best of our knowledge on the basis of ample literature review.展开更多
N-type, p-type and unintentionally-doped GaN were implanted with Yb ions by double energy ion im- plantation and the samples were annealed at 900 ℃. The structural and magnetic properties of the samples have been stu...N-type, p-type and unintentionally-doped GaN were implanted with Yb ions by double energy ion im- plantation and the samples were annealed at 900 ℃. The structural and magnetic properties of the samples have been studied by high-resolution X-ray diffraction （HRXRD）, Raman scattering and with a superconducting quan- tum interference device （SQUID）. No second phase has been observed and implantation induced defects can not be completely removed by rapid thermal annealing. The annealed samples show magnetic anisotropy and clear ferromagnetic behavior at room temperature. P-, u- and n-GaN：Yb samples show an effective magnetic moment of 1.60, 1.24 and 0.59 μB/Yb, respectively.展开更多
Unintentionally doped AIGaN layers, which were co.implanted with 400 keV Tb＋ ions and 200keV Cr＋ ions at doses of 1.5×1015cm-2, have been rapid thermally annealed at 800℃ and 900℃ for 5 min in flowing N2, Com...Unintentionally doped AIGaN layers, which were co.implanted with 400 keV Tb＋ ions and 200keV Cr＋ ions at doses of 1.5×1015cm-2, have been rapid thermally annealed at 800℃ and 900℃ for 5 min in flowing N2, Compared with Tb implanted AIGaN sample, the Tb and Cr co-implanted sample revesls a larger magnetic signal. In this work, the annealing effect on the structural and magnetic properties of Tb and Cr co-implanted AIGaN thin films have been studied. XRD and raman scattering results indicate that no second phase presents in thetin films and mast of the implantation induced defects can be removed by post-implantation annealing. Superconducting quantum interference device （SQUID） measurements show clear room temperature ferromagnetic behavior and an increase in the saturation magnetization as a result of annealing. The saturation magnetization of the 900℃ annealed sample is about 15 times higher than that of the 800℃ annealed sample.展开更多
文摘为了寻找新的高Tc的稀磁半导体(DMS),利用自旋局域密度泛函的第一性原理对 3d过渡金属(TM= V、Cr、Mn、Fe、Co或Ni)掺杂的II IV V2(CdGeP2 和ZnGeP2)以及I III VI2(CuGaS2 和CuGaSe2)黄铜矿半导体的电磁性质进行系统计算.结果发现:V或Cr 掺杂的 II IV V2 将出现铁磁(FM)状态,而 Mn、Fe或者 Co掺杂的 II IV V2 将出现反铁磁(AFM)状态,Ni掺杂时,DMS的磁性非常不稳定;在TM掺杂的 I III VI2 的DMS中,Cr、Mn掺杂的 CuGaS2 和 CuGaSe2将表现为FM状态,而当V、Fe、Co或Ni掺杂时,Cu(Ga,TM)S2 和Cu(Ga,TM)Se2 则表现了AFM性质.Cr掺杂的I IV V 以及 I III VI 黄铜矿半导体将可能出现较高的居里温度(Tc).
文摘Zn1-xCoxO films were grown on glass by sol-gel spin coating process. A homogeneous and stable Zn1-xCoxO sol was prepared by dissolving zinc acetate dihydrate, cobalt acetate tetrahydrate and aluminium chloride hexahydrate as solutes in solution of isopropanol and monoethanolamine. The films were postheated and vacuum annealed, and investigated for c-axis preferred orientation and electromagnetic properties. Zn1-xCoxO films with different Co concentrations were oriented well along the c-axis, especially the Zn1-xCoxO film with 10% Co(atom fraction) was highly c-axis oriented. The transmittance spectra show that Zn1-xCoxO films occur d-d transition and sp-d exchange interaction between Co2+ ions. The electrical resistivity of the films at 10% Co had the lowest value because the crystallite size became largest and the crystallinity of the c-axis was improved. X-ray photoelectron spectroscopy and alternating gradient magnetometer analyses indicated that no Co metal cluster was formed, and the ferromagnetism at room temperature appeared. The characteristics of the electrical resistivity and room temperature ferromagnetism of sol-gel derived Zn1-xCoxO films suggest a potential application of dilute magnetic semiconductor devices.
基金Supported by the Hangzhou Dianzi University Fund (Grant No. KYF091506003)funds from State Key Lab of Silicon Materials, Zhejiang University (Grant No. 2000603)
文摘The crystallographic structures and magnetic properties of a Zn0.95Co0.05O thin film deposited on a C-sapphire substrate using a dual-beam pulsed laser deposition method were characterized. It was shown from crystallographic analysis that the film belongs to the wurtzite structure with the C-axis aligned with that of the substrate. Magnetic hysteresis loops were observed till up to room temperature. A small peak around 55 K was noticed on the magnetization vs. temperature curve. The corresponding temperature of the small peak is close to that of ‘the abnormal peak’ reported by X.M. Zhang et al. From the results obtained, no correlation was found between the abnormal peak and the quantum effects. The magnetic behaviors in the Zn0.95Co0.05O film cannot be explained by the ferromagnetism in diluted magnetic semiconductors. The magnetic mechanisms in ZnO-based diluted magnetic semiconductors are also discussed.
文摘Spin ordering in a semiconductor has attracted much attention in the community of condensed matter physics. By combining ferromagnetism and the semiconducting nature, systems such as Mn-doped PbSnTe or InAs were found to exhibit tunable magnetic properties responsive to an externally applied electric field. It thus holds great promises for developing novel spintronics with the tuning-knobs such as gate voltage. Conventionally, those systems are often studied in bulk forms and commonly referred to diluted magnetic semiconductor (DMS).
基金Project supported by the UGC-DAE,Consortium for Scientific Research,Indore through its CRS project bearing No.CSR-IC/MSRSR-12/CRS-220/2017-18/1301.
文摘Zn0.90Ni0.10O nanoparticles have been synthesized by single-bath two-electrode electrodeposition at constant voltage. X-ray diffraction, UV vis and photoluminescence studies reveal that a single-phase polycrystalline hcp wurtzite crystal structure of ZnO is evolved. The material consists of a large number of defects such as oxygen vacancy (Ov) and zinc interstitial (Zi). The magnetization study reveals that the sample exhibits room-temperature global ferromagnetism and the ferromagnetic ordering seems to be defect induced via bound magnetic polaron mechanism, and double exchange is also expected to have played role. Interesting optoelectronic properties have been found in the synthesized sample and the material seems to be a potential candidate to be used as a UV sensor. Such a transition metal doped ZnO based dilute magnetic semiconducting system exhibiting room-temperature ferromagnetism is likely to be first of its kind in the sense that such materials have not yet been reported to be synthesized by the simple method of electrodeposition to the best of our knowledge on the basis of ample literature review.
基金supported by the National Natural Science Foundation of China(No.60876004)
文摘N-type, p-type and unintentionally-doped GaN were implanted with Yb ions by double energy ion im- plantation and the samples were annealed at 900 ℃. The structural and magnetic properties of the samples have been studied by high-resolution X-ray diffraction （HRXRD）, Raman scattering and with a superconducting quan- tum interference device （SQUID）. No second phase has been observed and implantation induced defects can not be completely removed by rapid thermal annealing. The annealed samples show magnetic anisotropy and clear ferromagnetic behavior at room temperature. P-, u- and n-GaN：Yb samples show an effective magnetic moment of 1.60, 1.24 and 0.59 μB/Yb, respectively.
文摘Unintentionally doped AIGaN layers, which were co.implanted with 400 keV Tb＋ ions and 200keV Cr＋ ions at doses of 1.5×1015cm-2, have been rapid thermally annealed at 800℃ and 900℃ for 5 min in flowing N2, Compared with Tb implanted AIGaN sample, the Tb and Cr co-implanted sample revesls a larger magnetic signal. In this work, the annealing effect on the structural and magnetic properties of Tb and Cr co-implanted AIGaN thin films have been studied. XRD and raman scattering results indicate that no second phase presents in thetin films and mast of the implantation induced defects can be removed by post-implantation annealing. Superconducting quantum interference device （SQUID） measurements show clear room temperature ferromagnetic behavior and an increase in the saturation magnetization as a result of annealing. The saturation magnetization of the 900℃ annealed sample is about 15 times higher than that of the 800℃ annealed sample.
