用于白光LED的KNaCa2(PO4)2:Eu2+蓝色荧光粉的发光特性

采用高温固相法合成了蓝色荧光粉KNaCa₂(PO₄)₂:Eu²⁺,利用X射线衍射(XRD)和光谱技术等表征了材料的性能。结果显示,少量Eu 2+的掺入并没有影响KNaCa₂(PO₄)₂的晶体结构。 在399nm近紫外光激发下,KNaCa₂(PO₄)₂:Eu²⁺材料发 射蓝光,发射光谱为400～600nm, 主发射峰位于471nm,对应Eu²⁺的4f^65d1→ 4f⁷跃迁发射;471nm发射峰,对应的激发光 谱为250～450nm,主激发峰位于399nm,与近紫外芯片匹配很好。 以365nm近紫外光作为 激发源时,KNaCa₂(PO₄)₂:Eu²⁺材料的发射强度约为商用蓝色荧光粉BAM:Eu 2+的85%;而以 399nm近紫外光作为激发源时,相较于BAM:Eu²⁺,KNaCa₂(P O₄)₂:Eu²⁺材料具有更强的发射强 度。此外,KNaCa₂(PO₄)₂:Eu²⁺和BAM:Eu²⁺的CIE色坐标接近,均位于蓝 色区域,色坐标分别 为(0.154,0.154)和(0.141,0.112)。研究结果 表明,KN aCa₂(PO₄)₂:Eu²⁺是一种在三基色白光LED中有应用前景的蓝色荧光粉。     

Eu3+掺杂Na2La2Ti3O10红色荧光粉的光谱性质

采用传统高温固相法制备了不同Eu³⁺浓 度掺杂的Na₂(La1－xEux) ₂Ti₃O10荧光粉,研究了Eu³⁺浓度 对样品结构及发光性质的影响。X射线衍射(XRD)结果表明Eu³⁺掺杂浓度不大于40%的 样品为四方相Na₂La₂Ti₃O10;当 Eu³⁺浓度达到60%时,出现了正交相NaEuTiO₄。对样品进行 激发、发射光谱的 测试发现,样品可被较 宽波段的紫外光有效激发,获得明亮的红橙色光发射,且Na₂La₂Ti₃O₁₀到Eu 3+存在有效的能量传递。利用 Van模型,证实了Eu³⁺间的交换相互作用是引发浓度猝灭的主要原因。利用Auzel模型 ,解释了Eu³⁺发光的自猝 灭行为。测试了样品在不同温度下的发射光谱和时间衰减曲线,确定样品发光产生 温度猝灭的主 要机理是Crossover过程。利用Arrhenius公式对实验数据进行拟合,确定激活能值约为0.26eV,说明Na₂(La1－xEux)₂Ti₃O₁₀荧光粉具有较好的发光热稳定性。     

荧光粉Sr2SiO4:Eu2+中不同格位发光研究

采用高温固相反应法制备了Sr₂SiO₄:xEu²⁺荧光粉,研究Eu²⁺所占据的 Sr₂SiO₄中Sr1和Sr2两个不同格位及掺杂浓度和激发波长对格位发光的影响。荧 光粉发射光谱为一双峰的宽发射光谱,可拟合为峰值位置位于480nm 和530nm的两条高斯曲线,分别对应Eu²⁺所占据的Sr1和Sr2两 个不同格位的发射。随着 Eu²⁺掺杂浓度增加,Sr1和Sr2格位的发光强度均出现浓度猝灭现象,Sr2格位的 长波长发射峰出现明显红移现象,而Sr1格位的短波长发射峰发生红移-蓝移-红 移现象,这与Sr1和Sr2格位的优先占据以及格位间能量传递有关。随着激发波 长的增加,Sr2格位的长波长发射的发光强度与Sr1格位的短波长发射的发光强 度比值增加,占据不同格位的Eu²⁺对不同激发波长表现出明显的选择激发效应。     

CaSi2O2N2:Ce3+/Eu2+荧光粉的发光性能研究

采用高温固相反应法制备了CaSi₂O₂N₂:C e³⁺/Eu ²⁺荧光粉,研究了分别掺杂Ce³⁺、Eu²⁺及Ce³⁺/Eu²⁺共掺 杂时荧光粉 的发光特性。CaSi₂O₂N₂:Ce³⁺在333 nm激发下得到宽波段的发射谱,发射峰 位于395nm,随着Ce³⁺浓度的增大,发 射波长出现明显的红移,猝灭浓度为1mol%。CaSi₂O₂N₂:Eu²⁺在397nm激发下得到峰值位于540nm处的宽波段发射谱, 猝灭浓度为1mol%。对于Ca0.99－2xSi₂O₂N₂:xCe ³⁺,xLi⁺,0.01Eu²⁺荧光粉,在333nm激发下,位于395nm处的发射峰十分微 弱,在540nm处有宽带发射,随着Ce³⁺浓度增大,位于540nm处的Eu²⁺的特征 发射显著增强。对于Ca0.98－ySi₂O₂N₂: 0.01Ce³⁺,0.01Li⁺,yEu²⁺荧光粉,在激发光波长 为333nm,Eu²⁺浓度较低时,可以观察到两个发射带,峰值分 别位于395nm及540nm,随着Eu²⁺浓度增加,位于395nm的 发射强度一直减小,而540nm处的发射强度先增加后减小,猝灭浓 度为0.4mol%。证实了Ce³⁺,Eu²⁺之间发生了有效的能 量传递。计算出Ce 3+、Eu²⁺之间能量传递的效率ηT,在Eu²⁺浓 度为 1mol%时ηT趋于饱和,达到97.7%。通过计算,得到Ce3+ 与Eu²⁺之间的能量传递方式为电偶极-电偶极相互作用。     

一种白光LED用绿色荧光粉Ba3Si6O12N2:Eu2+的制备及研究

采用传统高温固相反应法,合成了Ba3－xSi 6O₁₂N₂:xEu²⁺系列荧光粉。X射线衍射(XRD)图谱 分析表明,所有的样品均生成了 Ba₃Si₆O₁₂N₂纯相。激发光谱表明,样品在紫外到蓝光(250～470nm)范围内都可以被有效激发,当激发波长为358nm 时,发射 光谱是Eu²⁺典型的宽带发射,发射峰在495nm附近,属于^4f₇→^4f₆^5d₁能级之间的跃迁,半峰宽覆盖青绿光范围(480～557nm)。 研究了Eu²⁺掺杂浓度对发光性能的影响。结果表明,随着Eu²⁺掺杂量的逐渐增 加 ,发光强度逐渐增大,当x=0.15时,发射 强度达到最大,所对应的发射光谱波峰的波长最小(492nm);当Eu ²⁺的掺杂量继续增加时,发光强度开始减弱,这是由于Eu²⁺间距逐渐减小,非 辐射跃迁几率增加而发生浓度猝灭现象;不同浓度的样品的发光强度 与波长呈相反变化趋势,这与斯托 克斯(Stokes)定律是相符合的。研究结果表明,所合成的Ba₃Si₆O₁₂N 2:Eu²⁺新型绿色荧光粉适合在白光LED中应用。     

提高KLa1－x(MoO4)2:Eu3+x荧光粉发光性能的研究

在氧化气氛下,采用固相反应法合成了一系列 KLa1－x(MoO₄)₂:Eu³⁺x红 色荧光粉。利 用X射线衍射仪、扫描电子显微镜和荧光分光光度计考察了KLa1－x(MoO₄)₂:Eu³⁺x荧光粉的 物相、形貌和发光强度。结果表明,激活剂Eu³⁺和助熔剂H₃BO₃的添加没有改变K La(MoO₄)₂的物相结构。KLa1－x(MoO₄)₂:Eu 3+x荧光粉可以被近紫外(393 nm )和蓝光(463 nm)有效 激发,主发射峰值位于616 nm附近,发射红光,归属为Eu³⁺的 ⁵D₀→⁷F₂跃迁。393nm和463nm的激发波长与目前广泛使用的近紫外和蓝光LED芯片相匹配。添加质量分数为5%的H₃BO₃时 ,所制备的KLa1－x(MoO₄)₂:Eu³⁺x红色荧光粉的发光强度比未掺杂H₃BO₃时的发光强度提高了234%,色坐标 (0.639,0.339)比商用的Y₂O₃:Eu³⁺(0.625,0.338)更接近于美国电 视标准委员会标准(0.67),这表明这 种荧光粉具备成为商业化红色荧光粉的潜力。     

Eu3+-Bi3+共掺杂Ca0.7Sr0.3MoO4荧光粉发光性能的研究

采用高温固相法制备了Ca0.7Sr0.18M oO₄:0.08 Eu³⁺、Ca0.7Sr0.27MoO₄:0.02Bi³⁺和Ca0.7Sr0.18－1.5xMoO₄:0.08Eu³⁺,xBi³⁺红色 荧光粉,考察Bi³⁺浓度对荧光粉发光性能的影响以及Bi³⁺与Eu³⁺间的能 量传递。通过X射线衍射(XRD)以及荧光的激发、发射光谱 对荧光粉样品进行表征。结果表明,制备的Ca0.7Sr0.15MoO₄:0.08Eu3+ ,0.02Bi³⁺红色荧光粉属于白钨矿结构。在 Ca0.7Sr0.15MoO₄:0.08Eu³⁺,0.02Bi³⁺红色荧光粉中,由于Bi ³⁺的掺杂将吸收的能量传递给激活离子Eu³⁺,其发光强度得到 增强。当Bi³⁺掺杂量x=0.02时,在312 nm激发下,主发 射峰 在616 nm处的相对发光强度最大,属于Eu³⁺的⁵D₀→⁷F₂跃迁, 但掺杂浓度过高时会出现浓度猝灭现象,发光强度减弱。     

Zn2＋,Ba2＋,Mg2＋对CaMoO4:Eu红色荧光粉发光性能的影响

采用高温固相法,制备了系列Eu³⁺激活的掺 杂Zn²⁺、Mg²⁺和Ba²⁺离子的钼酸盐 红色荧光粉,并通过测试荧光粉的发射光谱、激发光谱和X射线衍射(XRD)谱等,对荧光粉 的物相结构 、发光性能进行了分析。 实验结果表明:荧光粉可以被近紫外(395nm)和蓝光(465nm) 有效激发,发射峰值位于616nm(Eu³⁺的⁵D₀→⁷F₂跃迁)波长的红光,395nm和465nm的激发 波长与 目前广泛使用的近紫外和蓝光LED芯片相匹配,适用于LED的制造;掺杂Zn²⁺、Mg 2+和Ba²⁺的 Ca0.88－xRxMoO₄:0.08Eu ³⁺红色荧光粉的发光强度均得到提高,且最佳掺杂浓度分别为15%和5%。在最佳浓度下,3种荧光粉的 发光强度大小为Ca0.73Zn0.15Mo O₄:0.08Eu³⁺ > Ca0.78Mg0.10MoO₄:0.08Eu³⁺> Ca0.83Ba 0.05MoO₄:0.08Eu³⁺。色坐标分析结果表明 :所制备的 荧光粉的色坐标达到了国家标准,比商用的Y₂O₃:Eu³⁺红色荧光材料更接近于标 准红色色坐标。     

白色荧光粉ZnWO4:Dy3+,Eu3+的制备及发光性能

采用高温固相法合成系列以ZnWO₄基质、Dy ³⁺,Eu³⁺作为激发离子的白色荧光粉, 并通过X射线衍射(XRD)、荧光光谱对荧光粉的物相结构和发光性能进行了研究。在 387nm波长激 发下,Dy³⁺的2F₉→⁶H15/2跃迁的蓝光发射及²F₉→ 6H13/2的黄光发射最强。随着Dy³⁺的浓度 增大荧光粉ZnWO₄:Dy³⁺的色坐标由黄光到白光移动,Dy³⁺的最佳掺杂浓度 是12%,此 时荧光粉的色坐标为(0.321,0.341)。在ZnWO₄:Dy³⁺中加入Eu³⁺可以使 荧光粉的色 坐标更接近于标准白光并向暖白光区移动,当Dy³⁺的浓度为12%时,加入浓度1~8%的 Eu³⁺,其色坐标都在白光区且当其浓度等于2%时色坐标(0.346,0.339)最接近标准白光(0.33,0.33),并可观察到Dy³⁺向Eu³⁺的能量传递。     

蓝色荧光粉K(Na)BaBP2O8:Eu2+的制备与发光特性

采用高温固相法在还原气氛中合成K(Na)BaBP₂O ₈:Eu²⁺系列硼磷酸盐蓝色荧光粉,研究煅烧温度 以及用Na⁺掺杂替换K⁺对荧光粉晶体结构和发光性能的影响。利用热重-示差扫描量热 (TG-DSC)、X射 线衍射(XRD)、荧光(PL)光谱和色坐标(CIE)等手段确定了 荧光粉的合成温度,并对荧光粉的晶体 结构和发光性能进行表征。结果表明,800～875℃制备的KBaBP₂O ₈:0.03Eu²⁺荧光粉具有KBaBP₂O₈纯相 结构,属于四方晶系,空间群I42d,荧光粉的最佳合 成温度为875℃。K(Na)BaBP₂O₈:Eu²⁺系列荧光粉 可被波长为365nm的近紫外光有效激发,与InGaN芯片( 350~410nm)相匹配;其发射光谱为 400~650nm的不对称宽带,发射峰位于456nm 左右,对应Eu²⁺的4f^65d1-4f⁷-5d⁰跃迁。利用van Uitert经 验公式计算了Eu²⁺取代KBaBP₂O₈中Ba²⁺和K⁺时所占的晶体学格位,得出 449.4nm、439.1nm两个发射属 于Eu²⁺占据8配位的Ba²⁺和K⁺的5d-4f跃迁发射 ,511.0、506.7nm两个发射属于Eu²⁺ 占据6配位的 Ba²⁺和K⁺的5d-4f跃迁发射。用适量Na⁺替换K⁺可 以明显提高荧光粉的发光强度,其最佳掺杂摩尔比例为 Na/K=0.35/0.65,此时荧光粉的主晶相没有改变,但XRD衍射峰向大角度方向偏移。K(Na)Ba BP₂O₈:Eu²⁺ 荧光粉的CIE点可落在从蓝光到蓝白光区域,在近紫外LED应 用中可以根据实际需要灵活选择。     

Investigation of Ta2O5/SiO2/4H-SiC MIS capacitors

Tantalum pentoxide (Ta₂O₅) deposited by pulsed DC magnetron sputtering technique as the gate dielectric for 4H-SiC based metal-insulator-semiconductor (MIS) structure has been investigated. A rectifying current-voltage characteristic was observed, with the injection of current occurred when a positive DC bias was applied to the gate electrode with respect to the n type 4H-SiC substrate. This undesirable behavior is attributed to the relatively small band gap of Ta₂O₅ of around 4.3 eV, resulting in a small band offset between the 4H-SiC and Ta₂O₅. To overcome this problem, a thin thermal silicon oxide layer was introduced between Ta₂O₅ and 4H-SiC. This has substantially reduced the leakage current through the MIS structure. Further improvement was obtained by annealing the Ta₂O₅ at 900 °C in oxygen. The annealing has also reduced the effective charge in the dielectric film, as deduced from high frequency C-V measurements of the Ta₂O₅/SiO₂/4H-SiC capacitors.     

Kinetics of chemical vapor deposition of WSix films from WF6 and SiH2Cl2: Effect of added H2, SiH4, and Si2H6

This paper describes reaction kinetics of chemical vapor deposition of WSi_x films from WF₆ and SiH₂Cl₂, focusing on the effect of added H₂, SiH₄, and Si₂H₆ as an active reaction initiator. Our studies indicate that the temperature at which film formation is extinguished, T_ex, can be lowered by introducing H₂ instead of the standard Ar carrier gas. For a SiH₂Cl₂/WF₆ pressure ratio of 20, H₂ addition changed the deposition mode from selective W deposition to blanket WSi_x deposition. The added H₂ also improved the step-coverage profile for substrate temperatures below 600 °C. Measured step coverage profiles indicate that the activation energy of deposition species was 147 kJ/mol. Adding either SiH₄ or Si₂H₆ can assist the film-forming reactions to achieve acceptable Si/W atomic composition ratios. Under these conditions, the residual fluorine concentration remained at acceptably low levels that are typical of conventional WF₆/SiH₂Cl₂ CVD processes.     

Avalanche electron injection in 4-nmSi3N4/8-nm SiO2 dielectric structure:turn-around phenomenon and Si-SiO2 interface degradation

Charge trapping and interface-state generation in very thin nitride/oxide (4-nm Si₃N₄+8-nm SiO₂) composite gate insulators are studied as a function of gate electrode work function and bottom oxide thickness. The behavior of the trapped positive charge under bias-temperature stress after avalanche electron injection (AEI) is investigated. Evidence is presented that secondary hole injection from the anode (gate/Si₃N₄ interface) and subsequent trapping near the SiO₂-Si interface result in a turnaround of the flatband voltage shift during AEI from the substrate. Just like the thermal oxides on Si, slow-state generation near the SiO₂-Si interface and boron acceptor passivation in the surface-space charge layer of the Si substrate are also observed after AEI in these nitride/oxide capacitors, and they are found to be strongly related to the secondary hole injection and trapping. Finally, interface-state generation can take place with little secondary anode hole injection and is enhanced by the occurrence of hole trapping     

二磷酸钾镨晶体的生长

用助熔剂缓冷法从KCl-KF熔体中生长出K_3Pr(PO_4)_2晶体。实验给出了助熔剂挥发量对晶体产率的影响。化学组成分析和X射线分析证明,所得的晶体是K_3Pr(PO_4)_2。测定了晶体的红外光谱、紫外可见吸收光谱和荧光光谱。     

Influence of the additives argon, O2, C4F8, H2, N2 and CO on plasma conditions and process results during the etch of SiCOH in CF4 plasma

Reactive ion etch processes for modern interlevel dielectrics become more and more complex, especially for further scaling of interconnect dimensions. The materials will be damaged within such processes with the result of an increase in their dielectric constants. The capability of selected additives to minimize the low-k sidewall damage during reactive ion etching (RIE) of SiCOH materials in fluorocarbon plasmas was shown in different works in the past. Most of the investigated additive gases alter the fluorine to carbon ratio as well as the dissociation of the parent gas inside the etch plasma. The result is a changed etch rate, a modified polymerization behavior and other characteristics of the process induced SiCOH damage. Heavy inert ions like argon will be accelerated to the sample surface in the cathode dark space and enhance therewith the sputter yield on the SiCOH network [1]. In this paper the additives Ar, O₂, C₄F₈, H₂, N₂ and CO were added to a conventional CF₄ etch plasma. We try to provoke different changes in the plasma conditions and therewith in the process results. Contact angle measurements, spectroscopic ellipsometry, Hg-probe analysis, FTIR measurements and SEM cross-sections were used to overview the additive induced modifications. To understand the influences of the additives gases more exactly, changes in the physical and chemical plasma behavior must be analyzed. Therefore quadrupole mass spectrometry (QMS) and quantum cascade laser absorption spectroscopy (QCLAS) were used.     

Nd:Y2O3透明陶瓷4F3/2-4I11/2跃迁光谱及高效激光输出

报道了采用真空烧结法结合热等静压技术制备的Nd:Y₂O₃透明陶瓷的荧光光谱特性及相关激光输出。通过与Nd:YAG透明陶瓷的荧光光谱对比,表明Nd:Y₂O₃透明陶瓷的4F_3/2-4I_11/2跃迁光谱存在着多个增益相当的谱线,这更有利于实现同时双波长段激光振荡;不同斯塔克子跃迁光谱的离散特性有利于通过腔镜镀膜控制不同波长损耗,获得丰富的1.0~1.1 μm波段激光。利用简单的平平两镜腔结构完成进一步的实验,通过选择的输出镜片镀膜获得了输出功率3.62 W、转换效率40.4%的1074.6 nm和1078.8 nm的双波长输出和输出功率1.7 W、转换效率19.4%的1130.3 nm波长输出。     

Electroluminescence of SrAl2O4:Eu phosphor

The SrAl₂O₄:Eu²⁺ phosphor powders have been synthesized by sol-gel process. Electroluminescent (EL) properties of the SrAl₂O₄:Eu²⁺ phosphor were investigated using a convenient thick film device. Green light emitting at a peak of 508 nm was obtained when driven by sine alternating current (AC). The color coordinate of the emission was x=0.148 and y=0.635. Luminance-voltage and afterglow characteristics of the SrAl₂O₄:Eu²⁺ EL devices were studied. The results show that SrAl₂O₄:Eu²⁺ can be used as green phosphor for EL displays.     

Reactive-ion etching of Ge2Sb2Te5 in CF4/Ar plasma for non-volatile phase-change memories

Etching of Ge₂Sb₂Te₅ (GST) is a critical step in the fabrication of chalcogenide random access memories. In this paper, the etch characteristics of GST films were studied with a CF₄/Ar gas mixture using a reactive-ion etching system. We observed a monotonic decrease in etch rate with decreasing CF₄ concentration indicating its importance in defining the material removal rate. Argon, on the other hand, plays an important role in defining the smoothness of the etched surface and sidewall edge acuity. We have studied the importance of gas mixture and RF power on the quality of the etched film. The smoothest surfaces and most vertical sidewalls were achieved using a CF₄/Ar gas mixture ratio of 10/40, a background pressure of 80 mTorr, and power of 200 W.     

用Tl_2SO_4制造玻璃光波导

本文报道了用TI盐(TI_2SO_4)离子交换法制备玻璃光波导的实验结果。与用AgNO_3离子交换制备的光波导相比,波导损耗较低,折射率分布呈准阶跃型,拟合确定其折射率分布函数为费米函数,折射率增量Δn>0.13。