Deformation potentials and photo-response of strained PbSe quantum wells and quantum dots

Deformation potentials (D_u and D_d) for PbSe where analyzed using transmission data of PbSe/PbEuSeTe multi-quantum wells (MQWs). We use calculations based on a k·p model to obtain the strain induced intervalley splitting in the quantum wells. For the reduction of the Fabri–Pérot interference fringes of the multilayer structures we design a PbEuSeTe/BaF₂ anti-reflex coating which is deposited on top of the MQWs. At low temperature we found PbSe deformation potentials D_u=-2.36 and 5.88. The results of the transmission measurements are compared with photo-current spectra measured with self-assembled PbSe/PbEuTe quantum dot superlattices.     

介电限域效应对PbSe量子点禁带宽度计算的影响研究

Considering the dielectric confinement effect on excitonics of PbSe quantum dots (QDs), a correction factor in the wave function was introduced to propose a new band gap calculation model for QDs. The modified model showed great consistency with the experimental data, especially in small size range. According to the variation of confined barrier, the band gap calculation model of PbSe QDs was analyzed in different solvents. The calculating results showed that the modified model was almost solvent-independent, which was consistent with our experimental results and related reports.     

热注入法合成PbX(X=S,Se)量子点的结构和性能研究

采用热注入的方法在空气氛围中合成PbX(X=S,Se)量子点,液体石蜡和磷酸三丁酯(TBP)作为不同的溶剂优化PbSe量子点的合成;使用六甲基二硅硫烷(TMS)作为硫源合成了第一激子吸收峰在900 ～ 1500 nm分布的PbS量子点.通过透射电镜(TEM)、X射线衍射(XRD)和吸收光谱等测试手段对合成的物质进行成分与光学性能分析表征,对比研究了Ⅳ-Ⅵ族化合物量子点在成核过程中的差异.结果表明在相同的实验条件下PbS量子点的反应条件相对温和,量子限域效应明显;而PbSe量子点的合成对环境的要求更加严苛,反应温度更高,量子点的尺寸分布更宽.     

PbSe量子点硅酸盐玻璃光纤的制备及光纤光致荧光光谱特性

对钠硼铝硅酸盐玻璃熔体进行拉丝,再经过退火热处理,制备得到光纤直径80~130μm的PbSe量子点玻璃裸光纤.透射电镜分析发现光纤中PbSe量子点的晶粒尺寸为4.2~5.5nm,掺杂体积比约1%.对量子点光纤的柔性进行了初步测试.以980nm泵浦激光作为激励源,用荧光光谱仪观测了量子点光纤的荧光发射谱.结果表明:合适的量子点光纤的退火条件跟块玻璃不同.当退火温度为500~600℃、热处理时间为5~10h时,观测到量子点光纤有强烈的荧光辐射,峰值波长位于1 300~1 450nm,半高全宽达200~330nm.光纤最佳退火温度为600℃、时间7.5h.本文得到的量子点玻璃光纤可进一步制备成玻璃基底的量子点光纤型增益器件光纤放大器、光纤激光器等.     

Synthesis and Characterization of Large PbSe Colloidal Quantum Dots

Large colloidal quantum dots of PbSe (first excitonic peak position >2 µm) are synthesized under different conditions of temperature, the concentration of precursors and their ratio, and concentration of oleic acid and diphenylphosphine. The dependence of the optical properties, grain size dispersity, and process yield on the processing conditions is systematically explored and discussed. The Ostwald ripening process and how it affects grain growth is demonstrated. Finally, the results for the dependence of the absorption wavelength on the grain diameter for large nanocrystals are compared to the relationships reported in the literature for smaller nanocrystals.     

Dielectrophoretic placement of quasi-zero-, one-, and two-dimensional nanomaterials into nanogap for electrical characterizations

DEP is one of promising techniques for positioning nanomaterials into the desirable location for nanoelectronic applications. In contrast, the lithography technique is commonly used to make ultra-thin conducting wires and narrow gaps but, due to the limit of patterning resolution, it is not feasible to make electrical contacts on ultra-small nanomaterials for a bottom-up device fabrication. Thus, integrating the lithography and dielectrophoresis, a real bottom-up fabrication can be achieved. In this work, the device with the nanogap in between two nanofinger-electrodes is made using electron-beam lithography from top down and the ultra-small nanomaterials, such as colloidal PbSe quantum dots, polyaniline nanofibers, and reduced-graphene-oxide flakes, are placed in the nanogap by DEP from bottom up. The threshold electric field for the DEP placement of PbSe nanocrystals was roughly estimated to be about 8.3 × 10(4) V/cm under our experimental configuration. After the DEP process, several procedures for reducing contact resistances are attempted and measurements of intrinsic electron transport in versatile nanomaterials are performed. It is experimentally confirmed that electron transport in both PbSe nanocrystal arrays and polyaniline nanofibers agrees well with Prof. Ping Sheng's model of granular metallic conduction. In addition, electron transport in reduced-graphene-oxide flakes follows Mott's 2D variable-range-hopping model. This study illustrates an integration of the electron-beam lithography and the DEP techniques for a precise manipulation of nanomaterials into electronic circuits for characterization of intrinsic properties.     

基于钠硼铝硅酸盐玻璃的PbSe量子点红外单模光纤激光

根据实验制备的钠硼铝硅酸盐PbSe量子点玻璃及其透射电子显微镜(TEM)图、吸收谱和发射谱,计算机数值模拟了以PbSe量子点作为激活增益介质的红外单模光纤激光。应用遗传算法,通过数值求解粒子数速率方程和激光谐振腔振荡方程,优化计算了量子点光纤激光器(QDFL)的最佳抽运波长、光纤长度、掺杂浓度及出射镜反射率。结果表明:饱和抽运功率为2 W,在1676nm激光波长处,QDFL最大输出功率可达1.36 W,抽运效率达68%。与通常的掺稀土离子(Yb3+、Er3+)的光纤激光器相比,QDFL具有抽运效率高、激励阈值低、掺杂密度可调、光纤饱和长度短等特点。由于量子点辐射波长的尺寸依赖特性,容易形成多波长激射或波长可调的新型激光器。     

Electron Paramagnetic Resonance Study of PbSe,PbTe, and PbTe:In Semiconductors Obtained by the Pulsed Laser Deposition Method

The magnetic properties of lead selenide (PbSe) and indium-doped lead telluride (PbTe:In) composites have been studied by using the electron paramagnetic resonance (EPR) technique. The samples were obtained by using the pulsed laser deposition method (PLD). Temperature dependences of the EPR spectra were obtained. The analysis of the temperature dependencies of the integral intensity of the EPR spectra was performed using the Curie–Weiss law. In these materials, the paramagnetic centers of Pb¹⁺ and Pb³⁺ ions were identified. The results are discussed.     

硒化铅核壳量子点的合成与应用研究进展

硒化铅(PbSe)量子点具有宽红外光谱调控范围、高荧光量子产率和可溶液加工等特点,成为一类重要的红外材料体系。与广泛研究的PbS量子点相比,PbSe量子点在空气中容易氧化,从而严重破坏其光电特性,制约了其应用的发展。壳层的包覆是有效提升PbSe量子点光学特性和化学稳定性的策略之一,是推动PbSe量子点应用发展的材料研究方向。本文综述了PbSe核壳量子点的合成及其在光电探测、太阳能电池、激光器和光催化等领域的应用研究进展,希望能够为国内研究者开展相关研究提供参考。