Deep level transient spectroscopy studies of Er and Pr implanted GaN films

Deep level transient spectroscopy measurements were used to characterize the electrical properties of metal organic chemical vapor deposition grown undoped, Er-implanted and Pr-implanted GaN films. Only one deep level located at 0.270 eV below the conduction band was found in the as-grown GaN films. But four defect levels located at 0.300 eV, 0.188 eV, 0.600 eV and 0.410 eV below the conduction band were found in the Er-implanted GaN films after annealing at 900 degrees C for 30 min, and four defect levels located at 0.280 eV, 0.190 eV, 0.610 eV and 0.390 eV below the conduction band were found in the Pr-implanted GaN films after annealing at 1050 degrees C for 30min. The origins of the deep defect levels are discussed. After annealing at 900 degrees C for 30min in a nitrogen flow, Er-related 1538nm luminescence peaks could be observed for the Er-implanted GaN sample. The energy-transfer and luminescence mechanism of the Er-implanted GaN film are described.

RBS/channeling study and photoluminscence properties of Er-implanted GaN

The Raman back scattering/channeling technique was used to analyze the damage recovery at different annealing temperatures and to determine the lattice location of the Er-implanted GaN samples. A better damage recovery was observed with increasing annealing temperature below 1000degreesC, but a complete recovery of the implantation damage cannot be achieved. For a sample annealed for at 900degreesC 30 min the Er and Ga angular scans across the <0001> axis was measured indicating that about 76% of Er ions occupies substitutional sites. Moreover, the photoluminscence (PL) properties of Er-implanted GaN thin films have been also studied. The experimental results indicate that those samples annealed at a higher temperature below 1000degreesC had a stronger 1539nm PL intensity. The thermal quenching of PL intensity for samples annealed at 900degreesC measured at temperatures from 15K to 300K is 30%.

Photoluminesfcence of Er-doped SiO2 films containing Si nanocrystals and Er

Correlations between Si nanocrystal (nc-Si) related photoluminescence (PL), Er3+ emission and nonradiative defects in the Er-doped SiO2 films containing nc-Si (SRSO) are studied. Upon 514.5 nm laser excitation the erbium-doped SRSO samples exhibit PL peaks at around 0.8 and 1.54 mum, which can be assigned to the electron-hole recombination in nc-Si and the intra-4f transition in Er3+, respectively. With increasing Er3+ content in the films, Er3+ emission becomes intense while the PL at 0.8 mum decreases, suggesting a strong coupling of nc-Si and Er 31 ions. Hydrogen plasma treatment for the samples improve the PL intensities of the 0.8 and 1.54 mum bands, indicating H passivation for the nonradiative defects existing in the samples. Further-more, from the effect of hydrogen treatment for the samples, we observe variation of the number of nonradiative defects with annealing temperatures. (C) 2003 Elsevier Science B.V. All rights reserved.

Role of amorphous silicon domains on Er3+ emission in the Er-doped hydrogenated amorphous silicon suboxide film

An investigation on the correlation between amorphous Si (a-Si) domains and Er3+ emission in the Er-doped hydrogenated amorphous silicon suboxide (a-Si:O:H) film is presented. On one hand, a-Si domains provide sufficient carriers for Er3+ carrier-mediated excitation which has been proved to be the highest excitation path for Er3+ ion; on the other hand, hydrogen diffusion from a-Si domains to amorphous silicon oxide (a-SiOx) matrix during annealing has been found and this possibly decreases the number of nonradiative centres around Er3+ ions. This study provides a better understanding of the role of a-Si domains on Er3+ emission in a-Si:O:H films.

Correlation between Er3+ emission and the microstructure of a-SiOx : H < Er > films

Photoluminescence (PL) from Er-implanted hydrogenated amorphous silicon suboxide (a-SiOX:H(x<2.0)) films was measured. Two luminescence bands with maxima at lambda congruent to 750 nm and lambda congruent to 1.54mum, ascribed to the a-SiOX:H intrinsic emission and Er3+ emission, were observed. Peak intensities of the two bands follow the same trend as a function of annealing temperature from 300 to 1000degreesC. Micro-Raman results indicate that the a-SiOX:H films are a mixture of two phases, an amorphous SiOX matrix and amorphous silicon (a-Si) domains embedded there in. FTIR spectra confirm that hydrogen effusion from a-SiOX:H films occurs during annealing. Hydrogen effusion leads to a reconstruction of the microstructure of a-Si domains, thus having a strong influence on Er3+ emission. Our study emphasizes the role of a-Si domains on Er3+ emission in a-SiOX:H films.

Real-time non-destructive testing of dynamic holograms in doubly-doped LiNbO3 crystals using phase-conjugate technique

Nankai University

稀土(Er, Nd, Yb, Pr, Ho, Sm)有机/无机杂化材料的制备及发光性能研究

目前，国内外对于铕和铽等稀土配合物的可见区发光和应用都有大量研究，但对具有近红外发光（800-1700 nm）性能的稀土配合物的研究还处于起步阶段。由于稀土的近红外发光在光纤通讯、激光系统及诊断学等方面应用具有特殊的优点，越来越引起人们的兴趣和重视。 稀土近红外发光配合物的致命弱点是其光、热和化学稳定性较差，从而限制了其在很多领域的实际应用。而溶胶－凝胶材料和介孔材料具有良好的光、热和化学稳定性，能改善客体分子的结构环境和化学微环境，从而能有效提高客体分子的发光性能。因此，本论文将具有优良近红外发光性能的稀土配合物分别与上述两种基质复合，从实验和理论研究稀土近红外发光杂化材料的性能和应用价值，制备出具有良好稳定性的高效稀土近红外发光杂化材料，以期为光纤通讯、激光等领域提供潜在的候选材料。围绕这一宗旨，开展了如下工作： 通过原位技术分别得到了掺杂和嫁接[Ln(dbm)3phen]化合物（Ln = Er, Nd, Yb）的杂化凝胶材料，Ln-D-P gel和Xerogel-Ln。通过对其近红外发光性能的研究，表明材料中配体能很好的保护稀土离子，并将能量有效的传递给稀土离子。采用Judd-Ofelt理论对所得部分材料进行了光谱分析，基于实验数据和理论分析表明其具有潜在的光放大和激光应用价值。 选择了两种含全氟化烷基链的β-二酮配体Hhfth和Htfnb，通过功能化的phen-Si配体，将三元配合物[Ln(hfth)3phen] (Ln = Er, Nd, Yb, Sm)和[Pr(tfnb)3phen]成功共价嫁接到介孔MCM-41和SBA-15杂化材料中，得到的衍生材料Ln(hfth)3phen–MCM-41、Pr(tfnb)3phen–MCM-41和Ln(hfth)3phen–SBA-15、Pr(tfnb)3phen–SBA-15都保持了高度有序的介孔p6mm结构，并展现出稀土离子特征的近红外发射。所得稀土配合物功能化的材料的发射光谱能完全覆盖对光通讯极具应用价值的1300-1600nm区域。 通过对Er(dbm)3phen–M41(X, Y) (X = 1~14, Y = 3, 6, 12, 18, 24 h)材料系统的比较研究，选择了X = 12, Y = 6作为合成目标材料的优化参数，通过功能化的phen-Si配体将[Ln(dbm)3phen]配合物共价嫁接于有序介孔MCM-41和SBA-15中(Ln = Er, Nd, Yb)，所得两类材料Ln(dbm)3phenM41和Ln(dbm)3phenS15都保持了很好的介孔有序性，并具有良好的近红外发光性能。通过对Ln(dbm)3phenM41和Ln(dbm)3phenS15两类材料发光行为的比较，以及两类材料中稀土离子的含量及孔结构的分析，推出以SBA-15为载体得到的材料在相对发光强度和荧光寿命上，均比以MCM-41为载体的材料有所提高。 通过对8－羟基喹啉配体进行改性，合成了具有双功能的配体Q-Si，继而合成了共价嫁接8－羟基喹啉衍生物的介孔杂化材料Q–SBA-15，其形貌均一，并具有高度有序的介孔p6mm结构。通过配体交换反应，得到了嫁接稀土喹啉配合物的具有近红外发光性能的介孔杂化材料LnQ3–SBA-15 (Ln = Er, Nd, Yb)，其仍然保持高度有序的介孔结构，且外形呈现与母体材料Q–SBA-15相似的弯曲圆柱状。激发配体的吸收，LnQ3–SBA-15材料都分别展现出相应稀土离子特征的近红外发射，并详细分析和讨论了所得介孔杂化材料的近红外发光性能。

M_2RSbO_6:R~(3+)复合氧化物的合成组成结构和性能的研究(M = Ba、Sr、Ca, R = La、Gd、Y、Bi, R' = Sm、Eu、Dy、Ho、Er、Tm)

对于稀土与非稀土所组成的二元复合氧化物的研究国外已有较多的报导。但是，对于稀土和锑的复合氧化物只是近年来才开始有些研究工作。含锑与稀土的多元复合氧化物的报导就更少。本文在我们实验室张静筠等人三元复合氧化物研究的基础上，开展Mo—Sb_2O_5—R_2O_3—R'_2O_3—Bi_2O_3多元体系的研究工作，这对于我国丰产元素稀土和锑的应用以及利用Bi~(3+)的激活与敏化将是有益的。本文按Thornton等人的方法合成了Ba_2BiSbO_6，Ba_2GdSbO_6，按EγΦECEHKO等人的方法合成了M_2RSbO_6 (M = Ba、Sr、Ca, R = La Y)。并以M_2RSbO_6为基质，掺Sm~(3+)、Eu~(3+)、Dy~(3+)、Ho~(3+)、Er~(3+)、Tm~(3+)和Bi~(3+)，研究它们的化学组成，晶体结构与发光性能的关系及规律，Bi~(3+)的荧光和敏作用。同时研究了它们的磁学和热学性能。化学组成的分析结果表明，计算的含量与实验测得的含量符合较好，说明化学反应是按化学计量比进行的。通过X-射线粉沫物相分析和晶胞参数的理论计算确定M_2RSbO_6(M = Ba、Sr、R = La、Y、Gd、Bi)复合氧化物是属于立方钙钛太型化合物。空间群为Fm3m，点群为Oh。用计算机计算了Ca_2YSbO_6的晶胞参数并结合荧光光谱分析确定它属于畸变的单斜钙钛矿，空间群为P_(21)。用磁天平测量了样品M_2RSbO_6 (M = Ba、Sr、Ca; R = Gd、Y、Bi)的磁化率。除Ba_2GdSbO_6是顺磁性物质外共余的都是反磁性的物质。按所用原料Sb_2O_5计算的磁化率与测量值符合较好，表明在所研究的M_2RSbO_6化合物中锑是正五价的。用热重热差分析仪测量了样品在反应中的热性能，观察到在化合物形成的过程中所用原料Sb_2O_3大约在520 ℃左右氧化变为Sb_2O_5。除所用原料碳酸盐分解外没有挥发性的物质，这就进一步证明化学组成分析和磁化率测量的结果是正确的。光学测量的结果表明，所有的磷光体随着激活离子浓度的不同其光谱都发生规律性的变化。对于不同Eu~(3+)浓度的Ba_2YSbO_6:Eu~(3+)和Br_2YSbO_6:Eu~(3+), Bi~(3+)体系用254nm激发时均能观察到Eu~(3+)于595nm的尖峰发射。用基质和Bi~(3+)的激发峰325nm激发时，明显地看到敏化剂Bi~(3+)到Eu~(3+)的能量传递，使Eu~(3+)于595nm的发射大大增强，我们认为Bi~(3+)对Eu~(3+)的敏化作用是由于基质和Bi~(3+)的~1S。→ 3P_1的跃迁吸收了激发的能量，然后无辐射弛豫到Eu~(3+)的激发态~5D_0，产生~5D_0 → 7F_1的磁偶极跃迁。对于不同Eu~(3+)浓度的Sr_2YSbO_6:Eu~(3+)和Sr_2YSbO_6:Eu~(3+), Bi~(3+)体系用245nm激发时均能观察到Eu~(3+)于595nm的尖峰发射。用基质和Bi~(3+)的激发峰335nm激发时，观察到基质和Bi~(3+)对Eu~(3+)具有某种能量传递。敏化作用机理与上述的Ba_2YSbO_6:Eu~(3+)和Ba_2YSbO_6:Eu~(3+), Bi~(3+)体系相同。对于不同Eu~(3+)浓度的Ca_2YSbO_6:Eu~(3+)和Ca_2YSbO_6:Eu~(3+), Bi~(3+)体系用396nm激发时，均能观察到Eu~(3+)于613nm很强的尖峰发射。用基质和Bi~(3+)的激发峰313nm激发时，见到Bi~(3+)和基质对Eu~(3+)具有某种能量传递，这种敏化作用主要是由于基质和Bi~(3+)的3P_1 → ~1S_0的400nm的宽带发射和Eu~(3+)的~7F_0 → ~5L_6的396nm的吸收相匹配产生~5L_6→~5D_0→~7F_2的跃迁。通过对激发光谱和荧光光谱的分析给出了Ca_2Y_(0.96)Eu_(0.04)SbO_6的能级图，从实验上可见，Eu~(3+)的发光强烈地依赖于钙钛矿的结构，当Eu~(3+)在空间群为Fm3m 的Ba_2YSbO_6和Sr_2YSbO_6中处于Oh点对称性时，主要是~5D_0 → ~7F_1的磁偶极跃迁。当Eu~(3+)在空间群为P_(21)的单斜钙钛矿中时，主要是~5D_0 → ~7F_2的电偶极跃迁。对于不同掺杂浓度M_2YSbO_6:R~(13+)(M = Ba、Ca; R' = Sm、Dy、Ho、Er、Tm)体系，通过激发和荧光光谱的研究，合理地确定了谱项。发现基质对Sm~(3+)、Dy~(3+)、Ho~(3+)具有敏化作用。对不同Bi~(3+)浓度的Ca_2YSbO_6:Bi~(3+)，由激发和荧光光谱可见Bi~(3+)具有二个激发带，第一激发带位于240nm处相当于~1S_0 → ~1P_1的跃迁，第二激发带位于315nm处相当于~1S_0 → ~3P_1的跃迁。有一个很强的兰紫色发射位于400nm处相当于~3P_1 →~1S_0的跃迁。

金属溶剂萃取的热力学研究 1.Er(NO_3)_3-TB -C_6H_(14) 体系2.CuSo_4-氨化P_(50)-16H_(14)体系

本文在溶液理论的基础上，用纯热力学方法研究了中性磷萃取剂-金属体系（TBP-Er(no_3)_3）和氨化P_(50)-金属体系（P_(50)-cus04）的平衡计算模型。对于TBP体系有下列萃取平衡Er(NO_3)_3 (a) + 3TBP_((0)) <-> Er(NO_3)_3. 3TBP_((0))对于氨化P50体系，在萃取剂大量过量下有下的平衡Er(NO_3)_3 (a) + 3TBP_((0)) <-> Er(NO_3)_3. 3TBP(0)对氧化P50体系，在萃取剂大量过量下有下的平衡Cu_((a))~(2+) + partial deriv H_2R_2_((0)) <-> Cu(HR_2)_2 + 2H~+。用Scatchard-hildebrand模型预测了C_6H_(24)-TBP二元体系的担力学性质，以近似地用于H_2O - 16H_4 - TBP三之体系，减少了实验工作量。用气相色谱法求得了三之体系H_2O - (6H_(14) - P_(50))的热力学平衡数据，由于改进了进样系统，使实验误差<2%。对二体系的水相，均采用Pitzer理论求算γ_(Er(WO_3)_3)，和γ_(Cn~(2+))。对有机相，用热力学关系求出了水，正已烷，萃取剂，的活度系数。实验结果用Scatchard-Hildebrand模型进行关联。使计算机上进行回归处理，求得萃取反应的热力学平衡常数Ka和萃合物的活度系数。计算中，将有效平衡常数进一步分解，以提出显函数项，并在图解数分中改进了计算方法，使得每条萃取等温成都解得到合理的积分值。Schatchard-Hildebrand模型能在较宽的有机相浓度区域应用。所得到的端值常数，可定性地分析各组分的相互作用。