Structural and magnetic properties of GaN:Sm:Eu films fabricated by co-implantation method

Diluted-magnetic GaN:Sm:Eu films have been fabricated by co-implantation of Sm and Eu ions into c-plane (0001) GaN films and a subsequent annealing process. The structural, morphological and magnetic characteristics of the samples have been investigated by means of high-resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM), and superconducting quantum interference device (SQUID). The XRD and AFM analyses show that the annealing process can effectively recover the crystalline degradation caused by implantation. Compared with GaN:Sm films, more defects have been introduced into GaN:Sm:Eu films due to the Eu implantation process. According to the SQUID analysis, GaN:Sm:Eu films exhibit clear room-temperature ferromagnetism. Moreover, GaN:Sm:Eu films show a lower saturation magnetization (Ms) than GaN:Sm films.

Variation of Optical Quenching of Photoconductivity with Resistivity in Unintentional Doped GaN

The optical quenching of photoconductivity under dual illumination in GaN samples with different resistivity is investigated to reveal the variation of deep levels. The samples are grown by metal organic chemical vapour deposition without intentional doping. Quenching bands centered at 1.35 eV, 1.55 eV, 1.98 eV, and 2.60 eV are observed. It is found that the 1.98 eV quenching band is dominated in all the samples and the 2.60 eV band is observed only in the high-resistivity samples. The possible defect levels responsible for the quenching bands and the origin of different quenching behaviour at 2.60 eV are discussed. It is suggested that the defect level responsible for quenching at 2.60 eV plays an important role for the enhancement of resistivity.

Anomalous shift of the beating nodes in illumination-controlled In1-xGaxAs/In1-yAlyAs two-dimensional electron gases with strong spin-orbit interaction

The beating patterns in the Shubnikov-de Haas oscillatory magnetoresistance originating from zero-field spin splitting of two-dimensional electron gases (2DEGs) in In0.52Al0.48As/InxGa1-xAs/In0.52Al0.48As quantum wells with silicon delta doped on the upper barrier layer have been investigated by means of magnetotransport measurements before and after illumination. Contrary to the expectation, after each illumination, the beating nodes induced by the zero-field spin-splitting effect shift to lower and lower magnetic field due to the decrease in the zero-field spin-splitting energy of the 2DEGs. The anomalous phenomenon of the shift of the beating nodes and the decrease in spin-orbit coupling constants after illumination cannot be explained by utilizing the previous linear Rashba model. It is suggested that the decrease in the zero-field spin-splitting energy and the spin-orbit coupling constant arise from the nonlinear Rashba spin splitting.

非极性GaN基稀磁半导体的制备与性质研究

Submitted by 阎军 (yanj@red.semi.ac.cn) on 2010-06-02T01:49:46Z No. of bitstreams: 1 孙莉莉博士毕业论文.pdf: 4262097 bytes, checksum: 1e7491172a0ed5e5117f934a6b9652a1 (MD5)

Donor defect in P-diffused bulk ZnO single crystal

A high concentration of shallow donor defect is formed in P-diffused ZnO single crystals. X-ray photoelectron spectroscopy analysis indicates that P atom occupy different lattice site at different diffusion temperature. Nature of the donor defect has been discussed.

InGaN基发光二极管的反常特性研究

Submitted by 阎军 (yanj@red.semi.ac.cn) on 2010-06-02T02:11:24Z No. of bitstreams: 1 丁凯博士学位论文.pdf: 16795233 bytes, checksum: 311ac7bbd9c83be13609a0a0f4b36268 (MD5)

立方相碳化硅高量程微机械加速度计研究

Submitted by 阎军 (yanj@red.semi.ac.cn) on 2010-06-07T01:08:53Z No. of bitstreams: 1 立方相碳化硅高量程微机械加速度计研究.pdf: 2551518 bytes, checksum: c103d007add79adccfc0be58903561c6 (MD5)

四针状氧化锌晶须吸波涂层的制备与研究

Submitted by 阎军 (yanj@red.semi.ac.cn) on 2010-06-08T12:54:01Z No. of bitstreams: 1 马泽宇-四针状氧化锌晶须吸波涂层的制备与研究.pdf: 1372183 bytes, checksum: 30e24d73348a7814510ac6f0039734ef (MD5)

InGaN 太阳能电池理论模拟及制备研究

Submitted by 阎军 (yanj@red.semi.ac.cn) on 2010-06-08T12:57:05Z No. of bitstreams: 1 毕业论文-张小宾.pdf: 4412903 bytes, checksum: f96f6b7c0b4a1341e050825b566caddd (MD5)

MOCVD设备研制及氮化物材料生长研究

Submitted by 阎军 (yanj@red.semi.ac.cn) on 2010-06-08T13:11:28Z No. of bitstreams: 1 MOCVD设备研制及氮化物材料生长研究—殷海波-200718013626085.pdf: 3776668 bytes, checksum: efab1d75bd6d03744fd23a7a554f17e7 (MD5)

MVPE Ga 掺杂ZnO 薄膜材料的制备及其在LED 中的应用

Submitted by 阎军 (yanj@red.semi.ac.cn) on 2010-06-13T08:11:59Z No. of bitstreams: 1 硕士论文－刘祯.pdf: 1866687 bytes, checksum: 88d4171893f5d652dc81f3bda540b7bf (MD5)

RTD、HEMT 在频率合成和分频中的应用

Submitted by 阎军 (yanj@red.semi.ac.cn) on 2010-06-08T13:17:09Z No. of bitstreams: 1 杜睿博士论文.pdf: 12005163 bytes, checksum: a1d0c576ba88e74a6d3e0e409070bc7f (MD5)

基于电子束曝光技术的硅纳米线器件的研究

Submitted by 阎军 (yanj@red.semi.ac.cn) on 2010-06-08T13:19:08Z No. of bitstreams: 1 王颖博士学位论文.pdf: 6199298 bytes, checksum: 635b6d0b5b18d86e2ebfbd67f6032dd5 (MD5)

Disentangling mechanical and mass effects on nanomechanical resonators

Micro and nanomechanical resonators are powerful and label-free sensors of analytes in various environments. Their response, however, is a convolution of mass, rigidity, and nanoscale heterogeneity of adsorbates. Here we demonstrate a procedure to disentangle this complex sensor response, to simultaneously measure both mass and elastic properties of nanometer thick samples. This turns an apparent disadvantage of these resonators into a striking and unique asset, enabling them to measure more than mass alone.

Superconductivity in Iron Telluride Thin Films under Tensile Stress

By realizing in thin films a tensile stress state, superconductivity of 13 K was introduced into FeTe, a nonsuperconducting parent compound of the iron pnictides and chalcogenides, with a transition temperature higher than that of its superconducting isostructural counterpart FeSe. For these tensile stressed films, superconductivity is accompanied by a softening of the first-order magnetic and structural phase transition, and also, the in-plane extension and out-of-plane contraction are universal in all FeTe films independent of the sign of the lattice mismatch, either positive or negative. Moreover, the correlations were found to exist between the transition temperatures and the tetrahedra bond angles in these thin films.