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共有20条相似文献,以下是第1-20项 搜索用时 109 毫秒

1.  MAGNETIC POLARIZATION OF SPACER Pd LAYER AND MAGNETIC PROPERTIES OF Co/Pd MULTILAYERS  
   梅良模  李民  马小丁  刘宜华  郑敏  顾有松  麦振洪  赵见高  T.P.MA  R.C.BARKER《中国物理》,1997年第6卷第6期
   Magnetic multilayers[Co(1.5 nm)/Pd(x nm)]40 grown by rf sputtering were studied by X-ray diffraction,vibrating sample magnetometer,torque magnetomet er and magnetoresistance measurements.The dependences of the interfacial roughne ss and the structure perfectness of Co/Pd multilayers on the spacer Pd layer thi ckness have been revealed from X-ray diffraction data.An oscillatory variation of saturation magnetization versus the thickness of the Pd spacer was observed.A similar oscillatory behavior in the dependence of its magnetic anisotropy on the thickness of the Pd spacer was observed.It is suggested from these two phenomen a that the magnetic polarization of Pd spacers oscillates between ferromagnetic and antiferromagnetic polarization with the increase of Pd spacer thickness under a RKKY-like interaction.Evidence is found for the antiferromagnetic polarization of the inner part of the Pd spacer.The antiferromagnetic coupling between two Co layers and giant magnetoresistance effect in Co/Pd multilayer system were not observed.The relationship among structure,interlayer coupling and magnetic polarization effect of the Pd spacer was discussed.    

2.  Structural and electrical properties of laser-crystallized nanocrystalline Ge films and nanocrystalline Ge/SiN_x multilayers  
   李悰  徐骏  李伟  江小帆  孙胜华  徐岭  陈坤基《中国物理 B》,2013年第10期
   Nanocrystalline Ge (nc-Ge) single layers and nc-Ge/SiNx multilayers are prepared by laser annealing amorphous Ge (a-Ge) films and a-Ge/SiNx multilayers. The microstructures as well as the electrical properties of laser-crystallized samples are systematically studied by using various techniques. It is found that the optical band gap of nc-Ge film is reduced compared with its amorphous counterpart. The formed nc-Ge film is of p-type, and the dark conductivity is enhanced by 6 orders for an nc-Ge single layer and 4 orders for a multilayer. It is suggested that the carrier transport mechanism is dominant by the thermally activation process via the nanocrystal, which is different from the thermally annealed nc-Ge sample at an intermediate temperature. The carrier mobility of nc-Ge film can reach as high as about 39.4 cm2.V ^-1 .s^-1, which indicates their potential applications in future nano-devices.    

3.  Preparation and characterization of room-temperature ferromagnetism GaMnN based on ion implantation  被引次数:1
   王基庆  陈平平  李志锋  郭旭光  H.Makino  T.Yao  陈弘  黄绮  周均铭  陆卫《中国科学G辑(英文版)》,2003年第46卷第5期
   This paper reports the fabrication of GaMnN ferromagnetic semiconductor on GaN substrate by high-dose Mn ion implantation. Both the structural and optical properties for Mn+-implanted GaN material were studied by X-ray diffraction, Raman scattering and photolumi-nescence. The results reveal that the implanted manganese incorporates on Ga site and GaMnN ternary phase is formed in the substrate. The magnetic behavior has been characterized by superconducting quantum interference device. The material shows room-temperature ferromagnet-ism. The temperature-dependent magnetization indicates different mechanism for ferromagnetism in Mn+-implanted GaN.    

4.  Flexible tuning microwave permeability spectrum in [ferromagnet/antiferromagnet]_n exchange-biased multilayer stack structure  
   金立川  张怀武  唐晓莉  白飞明  钟智勇《中国物理 B》,2013年第4期
   NiFe/[IrMn/NiFe/IrMn] 5 /[NiFe/IrMn] 4 /NiFe structured exchange-biased multilayer films are designed and prepared by magnetron sputtering. The static and the microwave magnetic properties are systematically investigated. The results reveal that adding a partially pinned ferromagnetic layer can effectively broaden the ferromagnetic resonance linewidth toward the low frequency domain. Moreover, a wideband multi-peak permeability spectrum with a 3.1-GHz linewidth is obtained by overlapping the spectra of different partially pinned ferromagnetic layers and [antiferromagnet/ferromagnet/antiferromagnet] n stacks. Our results show that the linewidth of the sample can be feasibly tuned through controlling the proper exchange bias fields of different stacks. The designed multilayered thin films have potential application for a tunable wideband high frequency noise filter.    

5.  The properties of GaMnN films grown by metalorganic chemical vapour deposition using Raman spectroscopy  
   邢海英  牛萍娟  谢玉芯《中国物理 B》,2012年第7期
   An investigation of room-temperature Raman scattering is carried out on ferromagnetic semiconductor GaMnN films grown by metalorganic chemical vapour deposition with different Mn content values. New bands around 300 and 669 cm-1, that are not observed in undoped GaN, are found. They are assigned to disorder-activated mode and local vibration mode (LVM), respectively. After annealing, the intensity ratio between the LVM and E2 (high) mode, i.e., ILVM /IE2 (high) , increases. The LO phonon-plasmon coupled (LOPC) mode is found in GaMnN, and the frequency of the LOPC mode of GaMnN shifting toward higher side is observed with the increase in the Mn doping in GaN. The ferromagnetic character and the carrier density of our GaMnN sample are discussed.    

6.  Nonlinear Localization due to a Double Negative Defect Layer in a One-Dimensional Photonic Crystal Containing Single Negative Material Layers  
   Munazza Zulfiqar Ali Tariq Abdullah《中国物理快报》,2008年第25卷第1期
   We investigate the effects of introducing a defect layer negative material layers on the transmission properties in a one-dimensional photonic crystal containing single The width of the defect layer is taken to be the same or smaller than the period of the structure. Different cases of the defect layer being linear or nonlinear and double positive or double negative are discussed. It is found that only a nonlinear double negative layer gives rises to a localized mode within the zero-Φeff gap in this kind of structure. It is also shown that the important characteristics of the nonlinear defect mode such as its frequency, its FWHM and the threshold of the associated bistability can be controlled by changing the widths of the defect layer and the host layers.    

7.  Structural, electrical and optical characterization of InGaN layers grown by MOVPE  
   Yildiz A  ztürk M Kemal  Bosi M  zelik S  Kasap M《中国物理 B》,2009年第18卷第9期
   We present a study on n-type ternary InGaN layers grown by atmospheric pressure metalorganic vapour phase epitaxy(MOVPE) on GaN template/(0001) sapphire substrate.An investigation of the different growth conditions on n-type InxGa1 xN(x = 0.06 0.135) alloys was done for a series of five samples.The structural,electrical and optical properties were characterized by high resolution x-ray diffraction(HRXRD),Hall effect and photoluminescence(PL).Experimental results showed that different growth conditions,namely substrate rotation(SR) and change of total H2 flow(THF),strongly affect the properties of InGaN layers.This case can be clearly observed from the analytical results.When the SR speed decreased,the HRXRD scan peak of the samples shifted along a higher angle.Therefore,increasing the SR speed changed important structural properties of InGaN alloys such as peak broadening,values of strain,lattice parameters and defects including tilt,twist and dislocation density.From PL results it is observed that the growth conditions can be changed to control the emission wavelength and it is possible to shift the emission wavelength towards the green.Hall effect measurement has shown that the resistivity of the samples changes dramatically when THF changes.    

8.  Structural evolution of a-Si:H/SiO2 multilayers upon step by step thermal annealing  
   梅嘉欣  徐骏  马忠元  朱达  隋妍萍  李伟  李鑫  芮云军  黄信凡  陈坤基《中国物理》,2004年第13卷第8期
   a-Si:H/SiO_2 multilayers were prepared by alternatively changing plasma enhanced chemical vapour deposition of a-Si:H layers and in situ plasma oxidation process. Subsequently, as-grown samples were annealed at temperatures from 350℃ to 1100℃ in N_2 ambient with an increment of 100℃. The evolution of bonding configurations and structures with annealing treatments was systematically investigated by Fourier-transform infrared spectroscopy. The peak position of Si-O stretching vibration of SiO_2 layers shift to 1087cm^{-1} after annealing at 1100℃, which demonstrates that the SiO_2 films fabricated by plasma oxidation after high temperature annealing can have similar properties to the thermal grown ones. A Si-O vibration from interfacial SiO_x was identified: the value x was found to increase as increasing the annealing temperature, which is ascribed to the cooperation of hydrogen effusion and reordering of the oxygen bond in SiO_x networks. The H-related bonds were observed in the form of H-Si-O_3 and H-Si-Si_{3-n}O_n (n=1-2) configurations, which are supposed to be present in SiO_2 and interfacial SiO_x layers, respectively. The H atoms bonded in different bonding configurations effuse at different temperatures due to their different desorption energies.    

9.  Growth and Annealing Study of Mg-Doped AlGaN and GaN/AlGaN Superlattices  
   王保柱 王晓亮 胡国新 冉军学 王新华 郭伦春 肖红领 李建平 曾一平 李晋闽 王占国《中国物理快报》,2006年第23卷第8期
   Mg-doped AlGaN and GaN/AlGaN superlattices are grown by metalorganic chemical vapour deposition (MOCVD) Rapid thermal annealing (RTA) treatments are carried out on the samples. Hall and high resolution x-ray diffraction measurements are used to characterize the electrical and structural prosperities of the as-grown and annealed samples, respectively. The results of hall measurements show that after annealing, the Mg-doped AIGaN sample can not obtain the distinct hole concentration and can acquire a resistivity of 1.4 ×10^3 Ωcm. However, with the same annealing treatment, the GaN/AlGaN superlattice sample has a hole concentration of 1.7 × 10^17 cm-3 and a resistivity of 5.6Ωcm. The piezoelectric field in the GaN/AlGaN superlattices improves the activation efficiency of Mg acceptors, which leads to higher hole concentration and lower p-type resistivity.    

10.  Defect types and room-temperature ferromagnetism in undoped rutile TiO2 single crystals  
   李东翔  秦秀波  郑黎荣  李玉晓  曹兴忠  李卓昕  杨静  王宝义《中国物理 B》,2013年第22卷第3期
   Room-temperature ferromagnetism has been experimentally observed in annealed rutile TiO2 single crystals when a magnetic field is applied parallel to the sample plane.By combining X-ray absorption near the edge structure spectrum and positron annihilation lifetime spectroscopy,Ti3+-V O defect complexes(or clusters) have been identified in annealed crystals at a high vacuum.We elucidate that the unpaired 3d electrons in Ti3+ ions provide the observed room-temperature ferromagnetism.In addition,excess oxygen ions in the TiO2 lattice could induce a number of Ti vacancies which obviously increase magnetic moments.    

11.  An effective-field theory study of hexagonal Ising nanowire: Thermal and magnetic properties  
   Yusuf Kocakaplan  Ersin Kantar《中国物理 B》,2014年第4期
   By means of the effective-field theory (EFT) with correlations, the thermodynamic and magnetic quantities (such as magnetization, susceptibility, internal energy, specific heat, free energy, hysteresis curves, and compensation behaviors) of the spin-l/2 hexagonal Ising nanowire (HIN) system with core/shell structure have been presented. The hysteresis curves are obtained for different values of the system parameters, in both ferromagnetic and antiferromagnetic cases. It has been shown that the system only undergoes a second-order phase transition. Moreover, from the thermal variations of the total magnetization, the five compensation types can be found under certain conditions, namely the Q-, R-, S-, P-, and N-types.    

12.  Magnetic entropy change involving martensitic transition in NiMn-based Heusler alloys  
   胡凤霞  沈保根  孙继荣《中国物理 B》,2013年第22卷第3期
   Our recent progress on magnetic entropy change(S) involving martensitic transition in both conventional and metamagnetic NiMn-based Heusler alloys is reviewed.For the conventional alloys,where both martensite and austenite exhibit ferromagnetic(FM) behavior but show different magnetic anisotropies,a positive S as large as 4.1 J·kg-1·K-1 under a field change of 0-0.9 T was first observed at martensitic transition temperature T M~197 K.Through adjusting the Ni:Mn:Ga ratio to affect valence electron concentration e/a,T M was successfully tuned to room temperature,and a large negative S was observed in a single crystal.The △S attained 18.0 J·kg-1·K-1 under a field change of 0-5 T.We also focused on the metamagnetic alloys that show mechanisms different from the conventional ones.It was found that post-annealing in suitable conditions or introducing interstitial H atoms can shift the T M across a wide temperature range while retaining the strong metamagnetic behavior,and hence,retaining large magnetocaloric effect(MCE) and magnetoresistance(MR).The melt-spun technique can disorder atoms and make the ribbons display a B2 structure,but the metamagnetic behavior,as well as the MCE,becomes weak due to the enhanced saturated magnetization of martensites.We also studied the effect of Fe/Co co-doping in Ni 45(Co1-xFex)5 Mn36.6In13.4 metamagnetic alloys.Introduction of Fe atoms can assist the conversion of the Mn-Mn coupling from antiferromagnetic to ferromagnetic,thus maintaining the strong metamagnetic behavior and large MCE and MR.Furthermore,a small thermal hysteresis but significant magnetic hysteresis was observed around TM in Ni51Mn49-xInx metamagnetic systems,which must be related to different nucleation mechanisms of structural transition under different external perturbations.    

13.  Structural and Magnetic Properties of Sm Implanted GaN  
   姜丽娟  王晓亮  肖红领  王占国  冯春  张明兰  唐健《中国物理快报》,2009年第26卷第7期
   The structural and magnetic properties of Sm ion-implanted GaN with different Sm concentrations are investigated. XRD results do not show any peaks associated with second phase formation. Magnetic investigations performed by superconducting quantum interference device reveal ferromagnetic behavior with an ordering tem- perature above room temperature in all the implanted samples, while the effective magnetic moment per Sin obtained from saturation magnetization gives a much higher value than the atomic moment of Sm. These results could be explained by the phenomenological model proposed by Dhar et al. [Phys. Rev. Lett. 94(2005)037205, Phys. Rev. B 72(2005)245203] in terms of a long-range spin polarization of the GaN matrix by the Sm atoms.    

14.  STRUCTURES,Pd SPACER POLARIZATION AND MAGNETIC PROPERTIES OF Co-Nb/Pd MULTILAYERS  
   梅良模  颜世申  李民  刘宜华  T.P.M  R.C.Barker《中国物理》,1997年第6卷第12期
   Magnetic multilayers [Co-Nb(1.5 or 3.6 nm)/Pd(x nm)]40 were fabricated by radio frequency sputtering synthesis.The structures and magnetic properties of the Co-Nb/Pd multilayers were studied by X-ray diffraction,vibrating sample magnetometer,torque magnetometer and ferromagnetic resonance measurements.The oscillatory dependence of the phase structure,the strain,the ferromagnetic inter layer coupling and the spacer polarization of multilayers on the increase of Pd spacer thickness was observed.The relationship among phase structure,strain,inte rlayer coupling and the polarization of Pd spacers was discussed.The magnetic polarization of Pd spacers will enhance the ferromagnetic coupling between magnetic layers and will restrain antiferromagnetic coupling to occur.The spin dependent electron transport along the normal direction of multilayers and its exchange interaction play key roles in causing these oscillatory behaviors.    

15.  Rapid Thermal Annealing Effects on Structural and Optical Properties of Self-Assembled InAs/GaAs Quantum Dots Capped by InAIAs/InGaAs Layers  
   吕威 黎大兵 张子旸 李超荣 张泽 徐波 王占国《中国物理快报》,2005年第22卷第4期
   Effects of rapid thermal annealing on the optical and structural properties of self-assembled InAs/GaAs quantum dots capped by the InAlAs/InGaAs combination layers are studied by photoluminescence and transmission electron microscopy. The photoluminescence measurement shows that the photoluminescence peak of the sample after 850℃ rapid thermal annealing is blue shifted with 370meV and the excitation peak intensity increases by a factor of about 2.7 after the rapid thermal annealing, which indicates that the InAs quantum dots have experienced an abnormal transformation during the annealing. The transmission electron microscopy shows that the quantum dots disappear and a new InAlGaAs single quantum well structure forms after the rapid thermal annealing treatment. The transformation mechanism is discussed. These abnormal optical properties are attributed to the structural transformation of these quantum dots into a single quantum well.    

16.  Electrical properties of MOCVD-grown GaN on Si (111) substrates with low-temperature AIN interlayers  
   倪毅强  贺致远  钟健  姚尧  杨帆  向鹏  张佰君  刘扬《中国物理 B》,2013年第8期
   The electrical properties of the structure of GaN grown on an Si (111) substrate with low-temperature (LT) A1N interlayers by metal-organic chemical-vapour deposition are investigated. An abnormal P-type conduction is observed in our GaN-on-Si structure by Hall effect measurement, which is mainly due to the A1 atom diffusing into the Si substrate and acting as an acceptor dopant. Meanwhile, a constant n-type conduction channel is observed in LT-A1N, which causes a conduction-type conversion at low temperature (50 K) and may further influence the electrical behavior of this structure.    

17.  Optical and magnetic properties of nitrogen ion implanted MgO single crystal  
   刘春明  顾海权  向霞  张焱  蒋勇  陈猛  祖小涛《中国物理 B》,2011年第20卷第4期
   The microstructure,optical property and magnetism of nitrogen ion implanted single MgO crystals are studied. A parallel investigation is also performed in an iron ion implanted single MgO sample as a reference. Large structural,optical and magnetic differences are obtained between the nitrogen and iron implanted samples. Room temperature ferromagnetism with a fairly large coercivity field of 300 Oe (1Oe=79.5775 A/m),a remanence of 38% and a slightly changed optical absorption is obtained in the sample implanted using nitrogen with a dose of 1×1018 ions/cm2 . Tran- sition metal contamination and defects induced magnetism can be excluded when compared with those of the iron ion implanted sample,and the nitrogen doping is considered to be the main origin of ferromagnetism.    

18.  Raman scattering studies on manganese ion-implanted GaN  
   徐大庆  张义门  张玉明  李培咸  王超《中国物理 B》,2009年第18卷第4期
   This paper reports that the Raman spectra have been recorded on the metal-organic chemical vapour deposition epitaxially grown GaN before and after the Mn ions implanted. Several Raman defect modes have emerged from the implanted samples. The structures around 182 cm-1 modes are attributed to the disorder-activated Raman scattering, whereas the 361 cm-1 and 660 cm-1 peaks are assigned to nitrogen vacancy-related defect scattering. One additional peak at 280 cm-1 is attributed to the vibrational mode of gallium vacancy-related defects and/or to disorder activated Raman scattering. A Raman-scattering study of lattice recovery is also presented by rapid thermal annealing at different temperatures between 700°C and 1050°C on Mn implanted GaN epilayers. The behaviour of peak-shape change and full width at half maximum (FWHM) of the A1(LO) (733 cm-1) and E2H (566 cm-1) Raman modes are explained on the basis of implantation-induced lattice damage in GaN epilayers.    

19.  Defect characterization and magnetic properties in un-doped ZnO thin film annealed in a strong magnetic field  
   宁帅  战鹏  王炜鹏  李正操  张政军《中国物理 B》,2014年第12期
   Highly c-axis oriented un-doped zinc oxide(Zn O) thin films, each with a thickness of ~ 100 nm, are deposited on Si(001) substrates by pulsed electron beam deposition at a temperature of ~ 320℃, followed by annealing at 650℃ in argon in a strong magnetic field. X-ray photoelectron spectroscopy(XPS), positron annihilation analysis(PAS), and electron paramagnetic resonance(EPR) characterizations suggest that the major defects generated in these Zn O films are oxygen vacancies. Photoluminescence(PL) and magnetic property measurements indicate that the room-temperature ferromagnetism in the un-doped Zn O film originates from the singly ionized oxygen vacancies whose number depends on the strength of the magnetic field applied in the thermal annealing process. The effects of the magnetic field on the defect generation in the Zn O films are also discussed.    

20.  Origin of Room-Temperature Ferromagnetism for Cobalt-Doped ZnO Diluted Magnetic Semiconductor  
   彭龙  ;张怀武  ;文岐业  ;宋远强  ;苏桦  ;John Q. Xiao《中国物理快报》,2008年第25卷第4期
   The pure single phase of Zn0.95 Co0.05 O bulks is successfully prepared by solid-state reaction method. The effects of annealing atmosphere on room-temperature ferromagnetic behaviour for the Zn0.95 Co0.05 O bulks are investigated. The results show that the air-annealed samples has similar weak ferromagnetic behaviour with the as-sintered samples, but the obvious ferromagnetic behaviour is observed for the samples annealed in vacuum or Ar/H2 gas, indicating that the strong ferromagnetism is associated with high oxygen vacancies density. High saturation magnetization Ms = 0.73μg/Co and coercivity Hc = 233.8 Oe are obtained for the Ar/H2 annealed samples with pure single phase structure. The enhanced room-temperature ferromagnetic behaviour is also found in the samples with high carrier concentration controlled by doping interstitials Zn (Zni).    

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