量子点体系中的自旋流的产生和能隙展宽
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摘要
在纳米体系中,由于尺寸限制将引起尺寸效应,派生出纳米体系具有与宏观体系不同的低维物性。展现出许多不同于宏观材料的物理和化学性质。如纳米体系中能级的不连续性将影响电子在纳米结构中的电输运特性和光学性质变化。本文主要分析在量子点体系中如何产生自旋电流,以及量子限制效应导致的纳米体系发光蓝移现象。
纳米结构体系发光蓝移现象一直是近年来大家关心的热点问题。文中分别采用了周期方势垒和周期δ势垒两种简单的一维模型,通过直接严格求解该模型下薛定鄂方程,给出晶场中的限域情况下电子能级结构以及纳米体系中电子的限域能,从而研究体系的发光蓝移现象。基于限域能的计算,讨论了纳米体系的限域能和发光蓝移随尺寸以及势场的变化关系。我们的结果表明:导带底的电子能级随体系的尺寸增大而降低;而价带顶则随粒径的增大而升高大,因此,限域能随纳米尺寸的减小迅速增大。同时将计算结果与通常文献中所采用的有效质量计算的结果进行比较,可以看出二者有明显差别,且尺寸越小,其差异越大。因此,限域能随尺寸的变化并不严格满足通过有效质量方法计算出来的结果。另外文中也分析了限域能与晶场势高度的关系,结果表明限域能随之增大而减小。
另外本论文的我们利用量子点体系的输运特性,研究了一种产生自旋极化电流的器件。为了研究通过量子点的自旋电流和极化电流的产生方法,我们采用了一具有三端接口的模型来进行研究,这个模型包括了一个铁磁端口和两个非磁性端口,此三端接口通过量子点弱。
As we know, the properties of nanostructure material are very different from these in macroscopic level, because of the size effects. The discrete energy levels in the nanostructure which can influence the electronic transport and optical properties. In this thesis, we report some result on the growth of the pure spin current and the spread of the energy gap in nanostructure.
Recently, considerable attention is being paid to the blue-shift of the nanostructure. We study the electronic energy spectra and confinement energies by solving the Schrodinger equation accurately, using two simple model of one-dimensional, under this model. We analyse the band gap blue shift of nanostructure by calculating the confinement energies in nanostructure and discussing the size-confinement energies and potential-confinement energies characteristic curve. The results suggest that the QDs with small size have a higher electron energy at the bottom of the conduction band and lower electron energy at the top of the valence band. So the confinement energies increased abrupt as the size of nano-particle decreased. Meanwhile, the confinement energies which are calculated by the effective mass approximation referred in many literatures are very different from the result we calculate by Schrodinger, when the particle size is small. Moreover, we also find that band gap blue shift depends on the potential in the particle. The confinement energies decreased as the potential increased.
Meanwhile, in order to get a generator of spin current, we propose a three terminals spin device, which composed of a ferromagnetic metal lead (source), a semiconductor lead (collector) and a paramagnetic control electrode. Each of the terminals has a bias voltage. For proper tunnel rates and other parameters, the pure spin current can be obtained in one of the terminal, by modulating the controlling voltage.
纳米结构体系发光蓝移现象一直是近年来大家关心的热点问题。文中分别采用了周期方势垒和周期δ势垒两种简单的一维模型,通过直接严格求解该模型下薛定鄂方程,给出晶场中的限域情况下电子能级结构以及纳米体系中电子的限域能,从而研究体系的发光蓝移现象。基于限域能的计算,讨论了纳米体系的限域能和发光蓝移随尺寸以及势场的变化关系。我们的结果表明:导带底的电子能级随体系的尺寸增大而降低;而价带顶则随粒径的增大而升高大,因此,限域能随纳米尺寸的减小迅速增大。同时将计算结果与通常文献中所采用的有效质量计算的结果进行比较,可以看出二者有明显差别,且尺寸越小,其差异越大。因此,限域能随尺寸的变化并不严格满足通过有效质量方法计算出来的结果。另外文中也分析了限域能与晶场势高度的关系,结果表明限域能随之增大而减小。
另外本论文的我们利用量子点体系的输运特性,研究了一种产生自旋极化电流的器件。为了研究通过量子点的自旋电流和极化电流的产生方法,我们采用了一具有三端接口的模型来进行研究,这个模型包括了一个铁磁端口和两个非磁性端口,此三端接口通过量子点弱。
As we know, the properties of nanostructure material are very different from these in macroscopic level, because of the size effects. The discrete energy levels in the nanostructure which can influence the electronic transport and optical properties. In this thesis, we report some result on the growth of the pure spin current and the spread of the energy gap in nanostructure.
Recently, considerable attention is being paid to the blue-shift of the nanostructure. We study the electronic energy spectra and confinement energies by solving the Schrodinger equation accurately, using two simple model of one-dimensional, under this model. We analyse the band gap blue shift of nanostructure by calculating the confinement energies in nanostructure and discussing the size-confinement energies and potential-confinement energies characteristic curve. The results suggest that the QDs with small size have a higher electron energy at the bottom of the conduction band and lower electron energy at the top of the valence band. So the confinement energies increased abrupt as the size of nano-particle decreased. Meanwhile, the confinement energies which are calculated by the effective mass approximation referred in many literatures are very different from the result we calculate by Schrodinger, when the particle size is small. Moreover, we also find that band gap blue shift depends on the potential in the particle. The confinement energies decreased as the potential increased.
Meanwhile, in order to get a generator of spin current, we propose a three terminals spin device, which composed of a ferromagnetic metal lead (source), a semiconductor lead (collector) and a paramagnetic control electrode. Each of the terminals has a bias voltage. For proper tunnel rates and other parameters, the pure spin current can be obtained in one of the terminal, by modulating the controlling voltage.
引文
[1] 林峰.纳米材料的制备方法与应用.广东技术师范学院学报,2007,20():9-17
[2] 杨玲敏,叶志镇.ZnO 量子点的制备及其光电性能研究进展.纳米材料与结构,2004,12(4):1671-1776
[3] 王震宇,于贵,刘云圻,白风莲等.TPA—PPV 纳米粒子的制备和尺度效应.液晶与显示,2005,20(7):278-281
[4] 冯军强,徐曼,曹晓珑.纳米 Ag/PAM/EVA 复合材料的制备及介电特性.稀有金属材料与工程,2006,35(1):85-88
[5] 袁吉仁,李要球,邓新华.纳米 ZnO 的光吸收特性研究.南昌大学学报工科版,2006,28(4):329-331
[6] 邵明珠,罗诗裕.纳米物理学的若干基本问题.漳州师范学院学报(自然科学版),2002,15(3):71-76
[7] 莫晓亮,姚彦,范智勇等.PAR 薄膜中由 STM 诱导的库仑岛研究.助能材料,2003,34(4):412-417
[8] 郑永博,关玲.生活中的纳米科技.高校理科研究,2005,12(): 414
[9] 谭镜明.纳米生物技术研究进展.化工技术与开发,2007,36(7):24-26
[10] 刘晓荣,曹阳,陈蕾等.纳米 HA-PCL 复合生物材料的结晶行为研究.合肥工业大学学报,2007,11(7):1462-1463
[11] 周伟,孙世国,彭孝军等.壳核型纳米颗粒的研究及生物应用.化学与生物工程,2007,24(6):61-63
[12] 夏涛.纳米技术在生物医药中的应用.科技创业,2007 ,20(8):86-87
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[14] 张立波,程锦荣.氮化硼纳米管阵列储氢的计算机模拟.计算物理,2007,24(6):741-743
[15] 王景雪,张超,汤正新等.半导体量子点的电子结构与其吸收峰波长的移动.洛阳师范学院学报,2007,26(2):41-44
[16] 苑星海.纳米微粒的量子尺寸效应与态叠加.嘉应学院学报,2006,24(6):39-41
[17] 宋国利,杨幼桐,孙凯霞等.量子点的电子结构及量子效应.黑龙江大学自然科学学报,2002,19(1):81-83
[18]李文兵.GaAs/AlGaAs 超晶格束缚态电子能级结构的理论研究.首都师范大学学报,2006,27():23-27
[19] 刘承师,王立民.量子阱中 InAs/InGaAs 自组织量子点的电子结构.北京师范大学学报,2002,27():502
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[21] Brune P,Bruder C,Scholler H.Photon-assisted transport ultrasmall quantum dots Influence of intradot transitions.Phys Rev B,1997,56(8):4730-4736
[22] Aguado Ramon,Inarrea Jesus,Platero Gloria.Coherent resonant tunneling in as fields.Phys Rev B,1996,53(15):10030-10040
[23] 莫晓亮,姚彦,范智勇等.PAR 薄膜中由 STM 诱导的库仑岛研究.助能材料,2003,34:412-413
[24] 傅英,徐文兰,陆卫.半导体量子电子和光电子器件.物理学进展,2001,7(2):255
[25] 刘砚章,范希庆.电子多声子作用对能带电子有效质量的影响.郑州大学学报,1990,22(4):37
[26] 戴松涛,叠雷.单电子效应及其应用.光电子·激光,1997,8(24):6-9
[27] Bastard G,Mendez E E,Chang L L,et al.Exciton bingding energy in quantum wells.Phys Rev B,1982,26(4):1974-1978
[28] Kim S S,Hong S K,Yeon K H.Linear optical properties of the semiconductor quantum shell.Phys Rev B,2007,76(4):115322-115330
[29] Nalamura Y,Masada A,Ichikawa M et al.Quantum-confinement effect in individual Ge1?xSnx quantum dots on Si(111) substrates covered with ultrathin SiO2 films using scanningtunneling spectroscopy.Appl Phys Lett,2007,91 013109(1)-013109(3)
[30] Zhang B P,Binh N T,Wakatsuki K et al.Growth of ZnO/MgZnO quantum wells on sapphire substrates and observation of the two-dimensional confinement effect.Appl Phys Lett,2005,86(3):032105
[31] 辛萍,孙成伟,秦福文等.反应磁控溅射ZnO/MgO多量子阱的光致荧光光谱分析.物理学报,2007年2月,56:1082-1087
[32] 宋淑芳、赵德威、徐征等.有机量子阱的光学性质.物理学报,2004,56:2910-2913
[33] Tchernycheva M,Nevou L,Doyennette L et al. Systematic experimental and theoretical investigation of intersubband absorption in GaN/AlN quantum wells.Phys Rev B,2006,73(12):125347(1)-125347(11)
[34] Makino T,Chia C H,Tuan N T et al.Room-temperature luminescence of excitons in ZnO(Mg,Zn)O multiplequantum wells on lattice-matched substrates.Appl Phys Lett,2000, 77(7):975-977
[35] Akman N,Durgun E,Cahangirov S et al.Confined states in multiple quantum well structures of SinGen nanowire superlattices.Phys Rev B,2007,76(24): 245427(1)- 245427(7)
[36] 李娜,袁先漳,李宁等.GaAs/AlxGa1-xAs量子阱能级结构设计与光谱分析. 理学报,2000,49(9):0797-0800
[37] Gu X Q,Zhu L P,Ye Z Z,et al.Room-temperature photoluminescence from ZnO/ZnMgO multiple quantum wells grown on Si(111) substrates.Appl Phys Lett,2007,91(2):022103(1)- 022103(2)
[38] Fu Z D,Cui Y S,Zhang S Y,et al.Study on the quantum confinement effect on ultraviolet photoluminescence of crystalline ZnO nanoparticles with nearly uniform size.Appl Phys Lett,2007,90(26):263113(1)- 263113(3)
[39] Najmaie Ali,Sherman E Ya,Sipe J E.Generation of Spin Currents via Raman Scattering.Phys Rev Lett,2005,95(5):056601(1)-056601(3)
[40] Tang C S,Mal'shukov A G,Chao K A.Generation of spin current and polarization under dynamic gate control of spin-orbit interaction in low-dimensional semiconductor systems.Phys Rev B,2005 71(19):195314(1)- 195314(9)
[41] Akera Hiroshi.Coulomb staircase and total spin in quantum dots.Phys Rev B,1999,60(15):10683-10685
[42] Long W,Wang J.Gate-controllable spin battery.Appl Phys Lett,2003,83(3):1397-1398
[43] Zhang P,Xue Q K,Xie X C.Spin Current throught a Quantum Dot in the Presence of an Oscillating Magnetic Field.Phys Rev Lett,2003,91(19):196602(1)-196602(4)
[44] Shi Junren,Zhang Ping,Xiao Di,et al.Proper Definition of Spin Current in Spin-Orbit Coupled Systems.Phys Rev Lett,2006,96(7):076604(1)- 076604(1)
[45] Sinova Jairo,Culcer Dimitrie,Niu Q.Universal Intrinsic Spin Hall Effect.Phys Rev Lett,2004,92(12):126603(1)-126603(4)
[46] Wang Baigeng,Wang Jian,Xing D Y.Spin current carried by magnons.Phys Rev B,2004,69(17):174403(1)-174403(5)
[47] Rashba Emmanuel I. Spin currents, spin populations, and dielectric function of noncentrosymmetric semiconductors.Phys Rev B,2004,70(16):161201R(1)-161201R(4)
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[2] 杨玲敏,叶志镇.ZnO 量子点的制备及其光电性能研究进展.纳米材料与结构,2004,12(4):1671-1776
[3] 王震宇,于贵,刘云圻,白风莲等.TPA—PPV 纳米粒子的制备和尺度效应.液晶与显示,2005,20(7):278-281
[4] 冯军强,徐曼,曹晓珑.纳米 Ag/PAM/EVA 复合材料的制备及介电特性.稀有金属材料与工程,2006,35(1):85-88
[5] 袁吉仁,李要球,邓新华.纳米 ZnO 的光吸收特性研究.南昌大学学报工科版,2006,28(4):329-331
[6] 邵明珠,罗诗裕.纳米物理学的若干基本问题.漳州师范学院学报(自然科学版),2002,15(3):71-76
[7] 莫晓亮,姚彦,范智勇等.PAR 薄膜中由 STM 诱导的库仑岛研究.助能材料,2003,34(4):412-417
[8] 郑永博,关玲.生活中的纳米科技.高校理科研究,2005,12(): 414
[9] 谭镜明.纳米生物技术研究进展.化工技术与开发,2007,36(7):24-26
[10] 刘晓荣,曹阳,陈蕾等.纳米 HA-PCL 复合生物材料的结晶行为研究.合肥工业大学学报,2007,11(7):1462-1463
[11] 周伟,孙世国,彭孝军等.壳核型纳米颗粒的研究及生物应用.化学与生物工程,2007,24(6):61-63
[12] 夏涛.纳米技术在生物医药中的应用.科技创业,2007 ,20(8):86-87
[13] 孙可,张航,徐旭光,卢丹勇.纳米颗粒在周期振动下行为的计算机模拟.振动与冲击,2007,26(9):120-123
[14] 张立波,程锦荣.氮化硼纳米管阵列储氢的计算机模拟.计算物理,2007,24(6):741-743
[15] 王景雪,张超,汤正新等.半导体量子点的电子结构与其吸收峰波长的移动.洛阳师范学院学报,2007,26(2):41-44
[16] 苑星海.纳米微粒的量子尺寸效应与态叠加.嘉应学院学报,2006,24(6):39-41
[17] 宋国利,杨幼桐,孙凯霞等.量子点的电子结构及量子效应.黑龙江大学自然科学学报,2002,19(1):81-83
[18]李文兵.GaAs/AlGaAs 超晶格束缚态电子能级结构的理论研究.首都师范大学学报,2006,27():23-27
[19] 刘承师,王立民.量子阱中 InAs/InGaAs 自组织量子点的电子结构.北京师范大学学报,2002,27():502
[20] Bruder C,Scholler H.Charging Effects in Quantum Dots in the Presence of Time-Varying Fields.Phys Rev Lett,1994,72(7):1076-1079
[21] Brune P,Bruder C,Scholler H.Photon-assisted transport ultrasmall quantum dots Influence of intradot transitions.Phys Rev B,1997,56(8):4730-4736
[22] Aguado Ramon,Inarrea Jesus,Platero Gloria.Coherent resonant tunneling in as fields.Phys Rev B,1996,53(15):10030-10040
[23] 莫晓亮,姚彦,范智勇等.PAR 薄膜中由 STM 诱导的库仑岛研究.助能材料,2003,34:412-413
[24] 傅英,徐文兰,陆卫.半导体量子电子和光电子器件.物理学进展,2001,7(2):255
[25] 刘砚章,范希庆.电子多声子作用对能带电子有效质量的影响.郑州大学学报,1990,22(4):37
[26] 戴松涛,叠雷.单电子效应及其应用.光电子·激光,1997,8(24):6-9
[27] Bastard G,Mendez E E,Chang L L,et al.Exciton bingding energy in quantum wells.Phys Rev B,1982,26(4):1974-1978
[28] Kim S S,Hong S K,Yeon K H.Linear optical properties of the semiconductor quantum shell.Phys Rev B,2007,76(4):115322-115330
[29] Nalamura Y,Masada A,Ichikawa M et al.Quantum-confinement effect in individual Ge1?xSnx quantum dots on Si(111) substrates covered with ultrathin SiO2 films using scanningtunneling spectroscopy.Appl Phys Lett,2007,91 013109(1)-013109(3)
[30] Zhang B P,Binh N T,Wakatsuki K et al.Growth of ZnO/MgZnO quantum wells on sapphire substrates and observation of the two-dimensional confinement effect.Appl Phys Lett,2005,86(3):032105
[31] 辛萍,孙成伟,秦福文等.反应磁控溅射ZnO/MgO多量子阱的光致荧光光谱分析.物理学报,2007年2月,56:1082-1087
[32] 宋淑芳、赵德威、徐征等.有机量子阱的光学性质.物理学报,2004,56:2910-2913
[33] Tchernycheva M,Nevou L,Doyennette L et al. Systematic experimental and theoretical investigation of intersubband absorption in GaN/AlN quantum wells.Phys Rev B,2006,73(12):125347(1)-125347(11)
[34] Makino T,Chia C H,Tuan N T et al.Room-temperature luminescence of excitons in ZnO(Mg,Zn)O multiplequantum wells on lattice-matched substrates.Appl Phys Lett,2000, 77(7):975-977
[35] Akman N,Durgun E,Cahangirov S et al.Confined states in multiple quantum well structures of SinGen nanowire superlattices.Phys Rev B,2007,76(24): 245427(1)- 245427(7)
[36] 李娜,袁先漳,李宁等.GaAs/AlxGa1-xAs量子阱能级结构设计与光谱分析. 理学报,2000,49(9):0797-0800
[37] Gu X Q,Zhu L P,Ye Z Z,et al.Room-temperature photoluminescence from ZnO/ZnMgO multiple quantum wells grown on Si(111) substrates.Appl Phys Lett,2007,91(2):022103(1)- 022103(2)
[38] Fu Z D,Cui Y S,Zhang S Y,et al.Study on the quantum confinement effect on ultraviolet photoluminescence of crystalline ZnO nanoparticles with nearly uniform size.Appl Phys Lett,2007,90(26):263113(1)- 263113(3)
[39] Najmaie Ali,Sherman E Ya,Sipe J E.Generation of Spin Currents via Raman Scattering.Phys Rev Lett,2005,95(5):056601(1)-056601(3)
[40] Tang C S,Mal'shukov A G,Chao K A.Generation of spin current and polarization under dynamic gate control of spin-orbit interaction in low-dimensional semiconductor systems.Phys Rev B,2005 71(19):195314(1)- 195314(9)
[41] Akera Hiroshi.Coulomb staircase and total spin in quantum dots.Phys Rev B,1999,60(15):10683-10685
[42] Long W,Wang J.Gate-controllable spin battery.Appl Phys Lett,2003,83(3):1397-1398
[43] Zhang P,Xue Q K,Xie X C.Spin Current throught a Quantum Dot in the Presence of an Oscillating Magnetic Field.Phys Rev Lett,2003,91(19):196602(1)-196602(4)
[44] Shi Junren,Zhang Ping,Xiao Di,et al.Proper Definition of Spin Current in Spin-Orbit Coupled Systems.Phys Rev Lett,2006,96(7):076604(1)- 076604(1)
[45] Sinova Jairo,Culcer Dimitrie,Niu Q.Universal Intrinsic Spin Hall Effect.Phys Rev Lett,2004,92(12):126603(1)-126603(4)
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