Spin injection in the multiple quantum-well LED structure with the Fe/AlOx injector

A spin-injection/-detection device has been fabricated based on the multiple quantum well light emitting diode (LED) structure. It is found that only a broad electroluminescence (EL) peak of a full width at half maximum of 8.6 nm appears at the wavelength of 801 nm in EL spectra with a circular luminescence polarization degree of 18%, despite PL spectra always show three well resolved peaks. The kinetic energy gained by injected electrons and holes in their drift along opposite directions broadens the EL pe...     

MgB2中的MgO纳米管

为观察MgO在MgB2超导样品中的影响和存在形式,通过在MgB2胚体样品之外,增加周围MgO量的实验方法,经过4 h 750℃的烧结,在制备好的MgB2超导样品内得到了壁厚是约4纳米,直径在50～80纳米,长为30～40微米以上的氧化镁(MgO)纳米管.在MgB2样品表面可以看到少量直径是200～300纳米的氧化镁(MgO)亚微米线.经过扫描电镜的能量损失谱和透射电镜EELS分析测量,证明了纳米管中没有硼元素.实验观测也表明这些氧化镁(Mgo)纳米管是由许多氧化镁(MgO)纳米晶片组成.     

Dynamics of dense spin ensemble excited in a barrier layer and detected in a well

Photoluminescence (PL) polarization of a spin ensemble was examined over a wide excitation wavelength range from 520 nm to 700 nm and a temperature range from 3.5 K to 300 K after it transfers from a (AlGa)As barrier layer and eventually quenches irradiatively in a GaAs quantum well (QW).A highest PL circular polarization of 30% can be kept at temperatures up to 120 K,while its room temperature value reaches about 17%.It is found that the main features of the optical spin orientation in bulk Al 0.27 Ga 0.73...     

Covalently derivatized NTA microarrays on porous silicon for multi-mode detection of His-tagged proteins

Porous silicon(PSi)was applied as a supporting substrate for stepwise covalent derivatization of undecylenic acid, N-hydroxysuccinimidyl ester(NHS-ester)and nitrilotriacetic acid(NTA).By taking the advantages of porous silicon as a supporting matrix such as high surface area to volume ratio,infrared transparency,porous semiconductors for laser desorption/ionization mass spectroscopy,and low fluorescence background,a multi-mode detection biochip prototype can be realized. We prepared such a protein microarra...     

Radiation-pressure-driven mechanical oscillations in silica microdisk resonators on chip

We demonstrate radiation-pressure-driven mechanical oscillations from high optical quality factor silica microdisk resonators on chip. Mechanical quality factors of 3520 in air and 12540 in vacuum for the fundamental radial breathing modes are obtained from 73 μm-diameter silica microdisks with mechanical frequencies of ~51 MHz. The measured mechanical oscillation threshold powers for the input light are determined to be 62.5 μW in air and down to 26.6 μW in vacuum.     

增大夏克-哈特曼波前传感器动态范围的算法研究

为了保证夏克-哈特曼波前传感器具有高灵敏度的同时又具有较大的动态范围,提出了一种能够有效增大传感器动态范围的数据处理方法光斑归位法。该方法使不规则的光斑回归到各自原来的位置,形成一个规则的光斑阵列,找到光斑阵列中某个光斑与微透镜的匹配关系,进而找到所有的光斑与微透镜的匹配关系。该方法的优点在于光斑不需要被限制在子孔径内且在不增加硬件等其他辅助条件下能够有效地增大夏克-哈特曼波前传感器的动态范围。实验验证了光斑归位法的正确性和可行性,结果表明,光斑归位法是正确的且采用该方法的动态范围比传统算法的动态范围提高了25倍以上。     

氟化单元封端的不同聚合度PBMA甲苯溶液气/液界面结构

采用ATRP技术合成具有不同聚合度的末端连接甲基丙烯酸全氟辛基乙酯(FMA)单元的聚甲基丙烯酸丁酯(PBMAm-ec-PFMAn).利用和频振动光谱(SFG)和表面张力测定技术研究了各种氟化聚合物溶液的气/液界面结构.发现PBMAm-ec-PFMAn甲苯溶液的表面活性及其气/液界面的结构与两种结构单元数密切相关.当PFMA聚合度(n)大约为4和6时,聚合物溶液的表面张力随着PBMA聚合度的增加从21增加到25mN/m(该值与PBMA均聚物溶液相同).SFG的研究结果表明PBMA段较长时溶液表面被PBMA所占据.PBMA段较短时,PFMA组分吸附在溶液表面,排列比较有序且紧密堆积.当PBMA末端只有1个FMA单元时,其甲苯溶液的表面张力随PBMA段长稍有增加(从22增加到23mN/m),其值介于21与25mN/m之间.研究表明当PBMA段较短时,可能聚合物中的氟化组分吸附在溶液表面,但其排列的有序性较差.随着PBMA聚合度的增加,氟化组分与PBMA组分可能同时占据在溶液表面,这时其表面张力大约为23mN/m.     

塑性理论在桩端盖机设计中的应用

桩端盖机设计和生产必须解决塑性极限弯矩、配套电动机功率、工件下料尺寸等计算问题．把桩端盖机的工件加工过程视为一个塑性折弯过程，根据问题的特点，提出基于Tresca屈服准则的一种简化计算方法，解决了工件在塑性折弯过程中的受力分析、应力和变形分析等问题，得到相应的数学表达式．最后结合某厂生产实际给出了一个计算实例，为桩端盖机设计提供了理论依据．     

三势垒隧穿结构中由外加垂直磁场引入的高子带非热占据

在一个特殊设计的三垒双阱异质结构中 ,注入到入射端量子阱中的电子 ,首先经过子带间弛豫填充到较低能级 ,紧接着通过共振隧穿逃逸出后面的双势垒结构 ,流入收集电极 ,完成了整个输运过程。通过比较带间光荧光谱中E2 HH1 与E1 HH1 两峰的强度 ,我们发现外加垂直磁场可以抑制子带间的LO声子和LA声子散射 ,使能量较高的子带上出现了明显的非热平衡占据。这一发现提供了一种新的控制子带间散射速率 (量子级联激光器的主要机制 )的有效方法 ,使得在量子阱子带间实现粒子数反转变得更加容易。     

芴-呋喃苯并噻二唑共聚物的光电性能

对芴-呋喃苯并噻二唑共聚物的吸收光谱、光致发光光谱、电致发光性能和光伏性能进行了研究. 共聚物在382 nm和530 nm处有两处明显的吸收峰, 其中530 nm处的吸收强度随着共聚物中呋喃苯并噻二唑单元(FBT)含量的增加而增加. 随着FBT单元含量的增加, 电致发光峰值从611 nm红移至702 nm. 以PVK为空穴传输层, 共聚物PFO- FBT0.1为发光层的发光器件, 在33 mA/cm2电流密度下的外量子效率达2.32%, 亮度为441 cd/m2. 实验中观察到快速的链内能量陷阱过程(从芴到FBT单元). 以共聚物PFO-FBT50为电子给体、PCBM为电子受体(重量比1:2)共混制备的光电池能量转换效率为1.13%, 开路电压0.85 V, 短路电流3.39 mA/cm2, 光谱响应边延伸至近750 nm.