调制掺杂Al0.27Ga0.73As/GaAs多量子阱结构的光致发光

在调制掺杂（Si）Al0.27Ga0.73As／GaAs多量子阱结构的光致发光谱中，观测到一个强发光峰及多个低能弱发光峰．强发光峰是量子阱中基态电子与重空穴复合，即激子复合形成的，其低温发光线形可用Voigt函数拟合.低能弱峰是势垒层Al0.27Ga0.73As中DX中心能级上的电子跃迁到SiAs原子而引起，由此确定DX中心有四个能级，其激活能分别为0．35、037、0．39、0．41eV     

氧空位和B离子共掺杂TiO_2催化性能的研究

采用密度泛函理论的第一性原理方法,对氧空位V_O和B离子单掺杂、共掺杂锐钛矿相TiO_2的电荷布居、态密度、可见光吸收光谱等问题进行了对比分析。结果表明:氧空位V_O与掺杂B离子协同作用,使更多的Ti原子失电子能力下降,Ti~(4+)减少而更多低价位的Ti~(3+)出现,有利于减少光生电子-空穴的复合。掺杂形成n型简并半导体,根据对吸收光谱的分析,共掺杂能够提高波长较长(570nm,2.11eV)的可见光吸收效率。因此,共掺杂不仅能提高可见光吸收效率,而且能减弱光生电子-空穴的复合,更有利于提高晶体光催化性能。     

制备方法对锌掺杂多孔硅蓝光发射强度及稳定性的影响

分别采用浸渍法和电镀法对多孔硅薄膜进行了锌掺杂.用扫描探针显微镜研究了多孔硅掺杂前后的表面形貌,用荧光分光光度计分析了样品的光致发光特性,发现锌掺杂增强了多孔硅的蓝光发射,且在420nm附近出现了一个小峰,样品放置一个月后,发光强度和峰位变化很小.红外吸收谱表明锌掺杂后,Si-O-Si键、Si2O-SiH键、H2Si-O2键的振动增强,且引入了Zn-O键.锌掺杂多孔硅发射蓝光是由于掺杂后多孔硅无定形程度增大,应力增大,表面进一步被氧化,使纳米硅粒中激发的电子-空穴对在SiOx层中或纳米硅粒与SiOx层界面的发光中心复合发光造成的,420nm处的发光峰是由锌填隙引起浅施主能级上的电子到价带跃迁造成的,同时分析了电镀法掺杂锌的优越性.     

Eu~(3+)掺杂纳米TiO_2的制备及催化降解亚甲基蓝的研究

采用溶胶-凝胶法制备了Eu3+掺杂的纳米TiO2粉体,采用X射线衍射(XRD)和荧光光谱分析(PL)等手段对TiO2的相结构和TiO2中电子-空穴对的复合性能进行了表征,探讨了掺杂组分对光催化活性的影响机制。以紫外光下降解亚甲基蓝为探针反应,考察铕的掺杂对催化剂催化性能的影响。结果表明Eu3+的掺杂能够通过抑制催化剂晶粒长大从而减少团聚,并且通过降低光生电子-空穴的复合几率,提高催化剂的光催化活性。光催化实验表明,催化剂加入量为3g/L,亚甲基蓝溶液初始浓度为20mg/L时,掺杂1%Eu3+的催化剂催化性能最佳,反应3.5h降解率达到85.5%。     

纳米非晶氮化硅块体能态结构的紫外发射谱研究

用紫外荧光发射谱较系统地研究了纳米非晶氮化硅块体(粒径～10nm)的能态结构,观察到三个发射带,它们分别对应2.0、2.8和3.2eV.随热处理温度升高,峰高增大,低真空下1000℃退火又出现一个新峰,对应3.0eV.分析表明,2.0和3.2eV 发射峰与纳米非晶氮化硅高比例界面中 Si 悬键形成受主型和施主型局域态能级有关.能级2.0eV 和3.2eV 分别对应导带电子与受主型缺陷局域态空穴复合及施主型缺陷局域态电子及价带空穴复合,只有在高温(1000℃)退火才出现的3.0eV 发射带与O-Si-N 生成新的缺陷局域态有关.     

掺杂型Bi_2WO_6可见光光催化材料的最新研究进展

Bi_2WO_6的禁带宽度窄(2.7eV),能吸收紫外光和可见光,同时具有形貌可控,氧化性强,耐光腐蚀,无毒无污染等优点,是一类非常有前途的可见光光催化材料。近年来的相关研究,主要是通过改性来解决单质Bi_2WO_6的光量子效率一般和光生电子-空穴易复合问题。最为常用的是掺杂改性,其对Bi_2WO_6的电子结构、外观形貌、粒子尺寸、比表面积、表面特性的调控均有重要作用,能够提高该类催化剂的量子效率、缩小禁带宽度、降低电子-空穴复合率以提高其光催化性能。从金属掺杂、非金属掺杂、共掺杂等方面集中介绍了各种掺杂手段对Bi_2WO_6光催化性能的研究进展,阐明了光催化反应机理,并对其下一步的研究重点进行了展望。     

高效单发光层绿色有机发光二极管的制备与性能研究

为了提升绿色有机发光二极管的效率,设计了阶梯能级结构的器件,使得载流子在器件中更有效传输,进而有效减缓了器件效率的衰减。选择热致延迟荧光材料(4s,6s)-2,4,5,6-四(9-氢咔唑-9-基)间苯二腈(4CzIPN)作为发光材料,并将其掺杂到能级匹配的主体材料1,3-二(咔唑-9-基)苯(mCP)中构成发光层,制备了一系列单发光层的绿色有机发光二极管。在发光材料的掺杂浓度为2%(wt,质量分数),发光层的厚度为20nm条件下,制得的器件性能最佳,其启亮电压为3.4V,其最大亮度、电流效率、功率效率和外量子效率分别为20706cd/m~2、50.49cd/A、41.96lm/W和16.7%。在亮度为1000cd/m~2条件下,其电流效率和外量子效率仍然高达34.06cd/A和11.6%。器件显示主峰位于504nm的4CzIPN特征发射,随着掺杂浓度的提升,越来越多的电子和空穴被4CzIPN分子所俘获,导致主体材料mCP的特征发射峰逐渐减弱。     

掺Mn硅酸锌薄膜中微量氧化锌对发光强度的影响

利用溶胶-凝胶法结合高温热处理在硅衬底上制备了掺Mn硅酸锌薄膜，用XRD、SEM、UV-Vis吸收谱和PL谱测试了样品的结晶性能与光学性能，并分析了热处理温度对掺Mn硅酸锌薄膜的结晶性能和光学性能的影响．实验结果发现，ZnO的适量存在对掺Mn薄膜的发光有增强作用．进一步的分析认为，这一现象的机理可由G．G．Qin提出的量子约束-发光中心（QCLC）模型进行解释，ZnO中受激发的电子和空穴通过隧穿效应到达硅酸锌基体中复合发光，从而增强发光强度．     

高阻In掺杂CdZnTe晶体缺陷能级的研究

利用低压垂直布里奇曼法制备了不同In掺杂量的CdZnTe晶体样品, 采用低温光致发光谱(PL)、深能级瞬态谱(DLTS)以及霍尔测试等手段研究了In掺杂CdZnTe晶体中的主要缺陷能级及其可能存在的补偿机制. PL测试结果表明, 在In掺杂样品中, In原子占据了晶体中原有的Cd空位, 形成了能级位于E_c-18meV的替代浅施主缺陷[In_Cd^+], 同时 [In_Cd⁺]还与[V_Cd^2-]形成了能级位于E_v+163meV的复合缺陷[(In_Cd⁺-V_Cd^2-)^-]. DLTS分析表明, 掺In样品中存在导带以下约0.74eV的深能级电子陷阱能级, 这个能级很可能是Te反位[Te_Cd]施主缺陷造成的. 由此, In掺杂CdZnTe晶体的电学性质是In掺杂施主缺陷、Te反位深能级施主缺陷与本征受主缺陷Cd空位和残余受主杂质缺陷补偿的综合结果.     

DCJTB掺杂的荧光型白光有机电致发光器件

本文基于为ITO/2-TNATA(20 nm)/NPB(30 nm)/BePP2:DCJTB(45 nm:X%)/Alq3(30 nm)/LiF(1 nm)/Al(100 nm)的白光器件结构(X为DCJTB的掺杂浓度(质量分数))。采用真空热蒸镀的方法,在高精度膜厚测控仪的监控下分别制备了发光层掺杂浓度为1,1.5,2.0,2.5,3.0不同器件,并对各器件性能进行了测试。实验结果表明:当DCJTB的掺杂浓度为2.0%时,平衡了器件中电子和空穴的传输能力,使载流子复合形成激子的几率增加,既使载流子的传输能力明显改善,并且有效地抑制了器件的荧光猝灭效应。在12 V电压下,可以获得发光亮度最高达到9 868cd/m2,发光效率大于7.2 cd/A,且色坐标为(0.334,0.337)的较理想白光有机发光器件。     

ZnO纳米棒Al掺杂和A1,N共掺杂的制备技术与光致发光性能

采用水热法首先合成了Al掺杂ZnO(AZO)纳米棒,在此基础上通过550℃的氨气氛中退火制备了Al,N共掺杂ZnO(ANZ())纳米棒.运用X射线衍射(XRD),场发射扫描电镜(FESEM),透射电子显微镜(TEM),X射线能谱(EDS)和光致发光(PL)对样品进行了表征与分析.结果表明,制备的AZO和ANZ()纳米棒...     

CdTe/CdMnTe多量子阱的生长和激子复合动力学性质的研究

用分子束外延在GaAs衬底上生长了CdTe/Cd0.8Mn0.2Te多量子 结构,利用X射线衍射（XRD）、低激发密度下的PL光谱和变密度激发的ps时间分辨光谱研究了CdTe/CdMnTe多量子阱的结构和激子复合特性。在变密度激发的ps时间分辨光谱中,发现不同激发密度下发光衰减时间不同,认为它的机理可能是无辐射复合引起的。     

Mg-Al共掺杂ZnO薄膜的制备及其光学特性

采用溶胶-凝胶（sol—gel）旋涂法在载玻片上制备了不同A1掺杂量的Mg—Al共掺杂ZnO薄膜．在室温下利用X射线衍射仪（XRD）、扫描电子显微镜（SEM）和光致发光（PL）谱仪等手段分析了Mg—Al共掺杂Zn0薄膜的微结构、形貌和发光特性．XRD结果表明Mg．AI＆掺杂zn0薄膜具有六角纤锌矿结构;随着Al掺杂量的增加,共掺杂薄膜呈C轴取向生长．由SEM照片可知薄膜表面形貌随Al掺杂量的增加由颗粒状结构向纳米棒状结构转变．透射光谱表明共掺杂薄膜在可见光区内的透射率大于50％,紫外吸收边发生蓝移．在室温下的PL谱表明Mg—Al共掺杂zn0薄膜的紫外发射峰向短波长方向移动：Al掺杂摩尔分数为1％和3％的Mg—Al共掺杂ZnO薄膜的可见发射峰分别为596nm的黄光和565nm的绿光．黄光主要与氧间隙有关,而绿光主要与氧空位有关．     

Detection of bioconjugated quantum dots passivated with different ligands for bio-applications

Bioconjugation of quantum dots has resulted in a significant increase in resolution of biological fluorescent labeling. This intrinsic property of quantum dots can be utilized for sensitive detection of target analytes with high sensitivity; including pathogenic bacteria and cancer monitoring. The quantum dots and quantum dot doped silica nanoparticles exhibit prominent emission peaks when excited at 400 nm but on conjugation to model rabbit antigoat antibodies exhibit diminished intensity of emission peak at 600 nm. It shows that photoluminescence intensity of conjugated quantum dots and quantum dot doped silica nanoparticles could permit the detection of bioconjugation. Samples of conjugated and unconjugated quantum dots and quantum dot doped silica nanoparticles were subjected to enzyme linked immunosorbent assay for further confirmation of bioconjugation. In the present study ligand exchange, bioconjugation, fluorescence detection of bioconjugated quantum dots and quantum dot doped silica nanoparticles and further confirmation of bioconjugation by enzyme linked immunosorbent assay has been described.     

Photoluminescence of ZnSe crystals doped with group V elements

The luminescent properties of ZnSe crystals doped with Group V elements from the vapor phase were studied. Doping was found to result in ann- top-type conversion and buildup of edge emission. The near-edge photoluminescence spectra of the crystals studied comprise two bands due to electron-hole recombination through acceptor levels related to dopant atoms and selenium interstitials.     

Effect of ion doping with donor and acceptor impurities on intensity and lifetime of photoluminescence from SiO2 films with silicon quantum dots

Doping with donor and acceptor impurities is an effective way to control light emission originated from quantum-size effect in Si nanocrystals. Combined measurements of photoluminescence intensity and kinetics give valuable information on mechanisms of the doping influence. Phosphorus, boron, and nitrogen were introduced by ion implantation into Si+ -implanted thermal SiO2 films either before or after synthesis of Si nanocrystals performed at Si excess of about 10 at.% and annealing temperatures of 1000 and 1100 degrees C. After the implantation of the impurity ions the samples were finally annealed at 1000 degrees C. It is found that, independently of ion kind, the ion irradiation (the first stage of the doping process) completely quenches the photoluminescence related to Si nanocrystals (peak at around 750 nm) and modifies visible luminescence of oxygen-deficient centers in the oxide matrix. The doping with phosphorus increases significantly intensity of the 750 nm photoluminescence excited by a pulse 337 nm laser for the annealing temperature of 1000 degrees C, while introduction of boron and nitrogen atoms reduces this emission for all the regimes used. In general, the effective lifetimes (ranging from 4 to 40 micros) of the 750 nm photoluminescence correlate with the photoluminescence intensity. Several factors such as radiation damage, influence of impurities on the nanocrystals formation, carrier-impurity interaction are discussed. The photoluminescence decay is dominated by the non-radiative processes due to formation or passivation of dangling bonds, whereas the intensity of photoluminescence (for excitation pulses much shorter than the photoluminescence decay) is mainly determined by the radiative lifetime. The influence of phosphorus doping on radiative recombination in Si quantum dots is analyzed theoretically.     

Structural and optical properties of Al-doped SnO2 nanowires

We report a facile thermal evaporation method for the syntheses of Al-doped SnO₂ nanowires using Al-doped SnO₂ nanoparticles as precursors. High-density, single-crystalline Al-doped SnO₂ nanowires were directly grown on the 6H-SiC substrates without any catalyst. X-ray diffraction patterns show that the Al dopants are incorporated into the rutile SnO₂ nanowires. The X-ray photoelectron spectra confirm the SnO₂ nanowires doped with 5 at.% Al. The photoluminescence spectra of the Al-doped SnO₂ nanowires exhibit that the large blue shift of the emission band can be observed in the Al-doped SnO₂ nanowires compared with undoped nanowires. The distortion of the crystal lattices caused by incorporation of Al atoms at the interstitials should be responsible for the large blue shift of the emission band.     

Calculations of optical properties in p-doped nitrides quaternary alloys multiple quantum wells

We present theoretical photoluminescence (PL) and absorption spectra of p-doped InGaN/AlInGaN and AlInGaN/InGaN multiple quantum wells (MQWs). The calculations were performed within the k.p method by means of solving a full eight-band Kane Hamiltonian together with the Poisson equation in a plane wave representation, including exchange–correlation effects within the local density approximation. Strain effects due to the lattice mismatch and an internal electric field are also taken into account. We show that by changing the In and Al composition we can reach short and long emission wavelengths. The trends in the calculated Stokes shift, due to many-body effects within the quasi-two-dimensional hole gas (2DHG), are analyzed as a function of the acceptor doping concentration. Since the studies of optical properties of quantum wells based on nitrides quaternary alloys are at an early stage, the results reported here will provide guidelines for the interpretation of forthcoming experiments.     

Electrically Pumped White‐Light‐Emitting Diodes Based on Histidine‐Doped MoS2 Quantum Dots

MoS₂ quantum dots (QDs)‐based white‐light‐emitting diodes (QD‐WLEDs) are designed, fabricated, and demonstrated. The highly luminescent, histidine‐doped MoS₂ QDs synthesized by microwave induced fragmentation of 2D MoS₂ nanoflakes possess a wide distribution of available electronic states as inferred from the pronounced excitation‐wavelength‐dependent emission properties. Notably, the histidine‐doped MoS₂ QDs show a very strong emission intensity, which exceeds seven times of magnitude larger than that of pristine MoS₂ QDs. The strongly enhanced emission is mainly attributed to nitrogen acceptor bound excitons and passivation of defects by histidine‐doping, which can enhance the radiative recombination drastically. The enabled electroluminescence (EL) spectra of the QD‐WLEDs with the main peak around 500 nm are found to be consistent with the photoluminescence spectra of the histidine‐doped MoS₂ QDs. The enhanced intensity of EL spectra with the current increase shows the stability of histidine‐doped MoS₂ based QD‐WLEDs. The typical EL spectrum of the novel QD‐WLEDs has a Commission Internationale de l'Eclairage chromaticity coordinate of (0.30, 0.36) exhibiting an intrinsic broadband white‐light emission. The unprecedented and low‐toxicity QD‐WLEDs based on a single light‐emitting material can serve as an excellent alternative for using transition metal dichalcogenides QDs as next generation optoelectronic devices.     

Fabrication of luminescent silver doped PbS nanowires in polymer

We report here fabrication of silver (0 to 1.76 mol%) doped PbS nanowires (radius r approximately 1.75 nm) in polymer by a simple wet chemical process. An X-ray photoelectron spectroscopy study clearly confirms the possibility of silver (Ag) doping in PbS nanowires. Both absorption and photoluminescence spectra reveal very strong quantum confinement effect in PbS nanowires as expected for a r/Bohr radius ratio approximately 0.0972 nm. Visible excitonic emission is observed at room temperature in the photoluminescence spectra of undoped and silver doped PbS nanowires in polymer. The excitonic emission is appreciably blue-shifted when doped by silver (1.76 mol%) indicating strong modification of the electronic states by magnetic silver ions. While Ag2+ centers at the substitutional lattice site show an emission band around 525 nm, Ag0 at the interstitial site act as nonradiative recombination centers. Effect of silver doping on the luminescence intensity is also discussed.