掺碳GaAs生长特性的研究

采用以碳纤维为碳源的固态源MBE技术，生长了不同厚度的重接碳GaAs以及具有不同表层厚度的δ碳掺杂GaAs，通过Nomarski干涉显微镜和原子力显微镜（AFM）对样品表面形貌的观察，分析了挨碳GaAs的生长过程和各种缺陷的产生，提出碳的掺入导致了GaAs材料的三维岛状生长，促进了各种缺陷的力生。提出了通过改善生长条件减少缺陷的途径。     

Yb3+掺杂铋酸盐玻璃的低温发光特性

选取55Bi2O3-25B2O3-10SiO2-7Ga2O3-3Yb2O3系统铋酸盐玻璃,研究了在不同温度(9-350 K)下Yb3+离子的发射光谱和荧光寿命变化情况,计算了不同温度下Yb3+离子在976和1020 nm的有效线宽△λeff,比较了不同温度下Yb3+离子的光谱特性和荧光寿命变化情况.发现随着测试温度的降...     

X-ray photoelectron spectroscopy and electrical properties studies of Nb-doped strontium titanate ceramics prepared from titanyl acylate precursors

Through a sol-gel or sol-precipitation process Nb₂O₅-doped SrTiO₃ was obtained from titanyl acylate precursors in acidic or alkaline solution, respectively. Nonstoichiometric powders were obtained by varying the Sr/Ti ratio in the starting materials. X-ray photoelectron spectroscopy (XPS) was used to investigate the surface properties of the powders and the sintered bulk ceramics. Excess Ti in the sol-gel process was converted to TiO₂ (rutile) after calcination. In contrast, in the sol-precipitation process, the excess Ti was converted to Magnéli phases, which benefited the powders sinterability, and also enhanced the formation of Ti³⁺ on the powder surface, resulting in an abnormally high dielectric constant. The excess Sr in the sol-gel process was converted to SrCO₃ and then to gaseous CO₂ during sintering, which resulted in some cavities in the microstructure. In the sol-precipitation process, a structure of Sr_n+1Ti_nO_3n+1 was established and some near rectangular shaped, high-density grains were obtained.     

Cr3+掺杂CaLu2Al4SiO12宽带近红外荧光材料发光性能与器件研究

近红外光谱技术在食品质量检测与分析、夜视、生物组织成像、植物生长调控等领域有重要的应用价值,宽带近红外光源在这些应用中起着重要的作用,而通过荧光材料转换实现宽带近红外LED光源有着不可比拟的优势。采用高温固相法制备了CaLu_2-xAl₄SiO₁₂:xCr~(3+_x=1%—13%荧光粉。研究结果表明,CaLu_2-xAl₄SiO₁₂:xCr³⁺荧光粉在423 nm的蓝光激发下,光谱覆盖了650—1000 nm范围,荧光粉的发射峰值位于752 nm,半高宽有167 nm。当Cr³⁺离子掺杂浓度为5%时,量子效率达到了60.9%。同时,CaLu_2-xAl₄SiO₁₂:xCr³⁺具有良好的热稳定性,在373 K时的发光强度为室温下的60.6%。此外,将CaLu₂Al₄Si...     

Enhancing electron field emission properties of UNCD films through nitrogen incorporation at high substrate temperature

The electron field emission (EFE) and electrochemical (EC) properties of N₂(10%)-incorporated ultra-nanocrystalline diamond (N₂-UNCD) films were investigated. Microstructure examination using TEM indicates that incorporating the N₂ species without the substrate heating induced the presence of stacking faults, which can be effectively suppressed by growing the films at elevated temperature. While the synthesis of N₂-UNCD without substrate heating can efficiently enhance the EC properties (large potential window with smaller background current) of the films, the EFE behavior of the films can be improved only when the films were grown at an elevated temperature. Moreover, coating the conducting N₂-UNCD on Si-tips can further enhance the EFE and CV behaviors, viz. (E₀)_tip = 5.0 V/μm with (J_e)_tip = 0.28 mA/cm² at 15 V/μm applied field and ΔE_p = 0.5 V with redox peak 170 μA were achieved.     

掺Dy3+铁氧体硅油基磁流体磁特性与温度的相关性研究

利用液相共沉淀法制备了纳米掺Dy3+铁氧体磁颗粒,用表面活性剂修饰后,在超声振荡下分散在硅油中制得磁流体.分别用TEM、XRF、XRD、SQUID分析手段对样品进行了表征,在203 ～358 K范围内,研究了温度变化对磁流体磁特性和粘度的影响.结果表明:制备的磁颗粒平均粒径约16.3 nm、物相主要是Fe2O3、Dy2O3,结构为面心立方尖晶石型.通过磁性能测试发现,磁流体的饱和磁化强度(MS)、矫顽力(HC)和粘度随温度(T)的降低,呈现出增大的变化规律;并且还发现,298 K≤T≤358 K时,温度降低对矫顽力和粘度的影响较小;T＜298 K时,温度降低,矫顽力和粘度明显增大.     

Cu掺杂对(K_(0.5)Na_(0.5))NbO_3-(Bi_(0.5)Na_(0.5))TiO_3-LiSbO_3-NaTaO_3系压电陶瓷结构及性能的影响

采用传统的陶瓷工艺制备了0.94[0.9405(K0.5Na0.5)NbO3-0.0095(Bi0.5Na0.5)TiO3-0.05LiSbO3]-0.06NaTaO3(简称KNN-BNT-LS-NT)+xmol%CuO(0≤x≤2.0)陶瓷,研究了其晶体结构、压电、介电以及铁电性质,并对Cu2+在A、B位取代做了详细的分析讨论。结果表明,Cu2+的加入能显著提高陶瓷的机械品质因数Qm和降低其介电损耗tanδ,当加入1.5mol%的Cu2+在时,取得较佳的性能,即d33=183pC/N、Qm=166、tanδ=0.0135。     

掺Er3+钨碲玻璃光纤放大器的特性研究

以WO₃、TeO₂、ZnO和Na₂O为基质制备了掺Er³⁺钨碲(EDWTZn)玻璃.差热分析表明EDWTZn玻璃的转变温度达到427℃,比常规碲酸盐玻璃具有更高的热稳定性.McCumber原理研究的结果显示,EDWTZn玻璃在1530nm处的峰值受激发射截面和荧光发射半高宽分别为9.52×10^-21cm²和86nm.数值模拟结果表明,EDWTZn光纤放大器利用较短的激活长度就可获得足够的信号光放大,在1530nm波长附近能提供极宽的平坦增益带,当输入信号光功率为0dBm时,在大约70nm带宽范围内的平均信号增益大于20dB,不平坦度小于5dB.     

准共线声光可调谐掺铒光纤激光器的研究

提出了一种新颖的单纵模、单偏振的可调谐掺铒光纤激光器结构。使用准共线型声光可调谐滤波器作为调谐元件。利用饱和吸收效应在未泵浦低掺铒光纤中形成自写入瞬态光栅,用以压窄输出激光的线宽,并且有效地防止跳模。理论计算表明:当泵浦功率为100mW时,激光器的输出功率可达5.5mW,输出线宽在10-4nm量级。这些数据对后续的实验研究有指导作用。