First-Principles Investigation of Charge Transfer Mechanism of B-Doped 3C-SiC Semiconductor Material

This study delves into the charge transfer mechanism of boron (B)-doped 3C-SiC through first-principles investigations. We explore the effects of B doping on the electronic properties of 3C-SiC, focusing on a 12.5% impurity concentration. Our comprehensive analysis encompasses structural properties, electronic band structures, and charge density distributions. The optimized lattice constant and band gap energy of 3C-SiC were found to be 4.373 Å and 1.36 eV respectively, which is in agreement with previous research (Bui, 2012;Muchiri et al., 2018). Our results show that B doping narrows the band gap, enhances electrical conductivity, and influences charge transfer interactions. The charge density analysis reveals substantial interactions between B dopants and surrounding carbon atoms. This work not only enhances our understanding of the material’s electronic properties, but also highlights the importance of charge density analysis for characterizing charge transfer mechanisms and their implications in the 3C-SiC semiconductors.

Pr,Yb,Ho:GdScO_(3)晶体生长及光谱性能

2.7-3.0μm波段激光在很多领域具有重要应用,为探索和发展该波段新型晶体材料,本文采用提拉法生长出Pr,Yb,Ho:GdScO_(3)晶体,通过共掺入Pr3+离子以达到衰减Ho^(3+):^(5)I_(7)能级寿命的目的.采用X射线衍射测试得到了晶体的粉末衍射数据,测量了拉曼光谱,并对晶体的拉曼振动峰进行指认,对Pr,Yb,Ho:GdScO_(3)晶体的透过光谱、发射光谱和荧光寿命进行表征.Yb^(3+)的最强吸收峰在966 nm,吸收峰半峰宽为90 nm;2.7-3.0μm波段最强发射峰在2850 nm,半峰宽为70 nm;Ho^(3+):^(5)I_(6)和^(5)I_(7)能级寿命分别为1094μs和56μs.与Yb,Ho:GdScO_(3)晶体相比,Yb^(3+)的吸收峰和2.7-3.0μm的发射峰半峰宽明显展宽,同时下能级寿命显著减小,计算表明Ho^(3+):^(5)I_(7)与Pr^(3+):^(3)F_(2)+^(3)H_(6)能级之间能实现高效的能量传递.以上结果表明Pr,Yb,Ho:GdScO_(3)晶体是性能更优异的2.7-3.0μm波段激光材料.

欧洲葡萄NF-YB3基因克隆与表达分析

为探究VvNF-YB3基因在葡萄生长发育和响应非生物胁迫过程中的功能,以无核白为试材,克隆得到了VvNF-YB3基因编码区序列,全长为624 bp,编码207个氨基酸,蛋白质等电点6.31,不稳定指数27.66,总平均疏水指数-0.738,为一酸性、稳定的亲水蛋白。通过生物信息学分析发现,VvNF-YB3基因位于10号染色体,含有1个内含子,编码蛋白质存在1个CBFD_NFYB_HMF结构域,与河岸葡萄NF-YB3相似性最高。VvNF-YB3的二级结构中α-螺旋和无规则卷曲占比较高,三级结构为单体的螺旋-卷曲-螺旋,启动子中包含响应激素和胁迫的多个顺式作用元件。VvNF-YB3基因在葡萄的叶片、卷须、花、幼果和茎中均表达,且在成熟的叶片中表达量最高。PEG模拟的干旱、低温和高温胁迫均可影响VvNF-YB3基因的表达,VvNF-YB3为一胁迫响应基因。VvNF-YB3的互作蛋白大多是核因子Y家族的亚基,ERF、bHLH、ARF等27个转录因子可能调控VvNF-YB3基因的表达。由此推测,VvNF-YB3基因可能通过受到上游转录因子的调控并与其他NF-Y蛋白互作响应各种环境胁迫。

Yb∶Ca_(3)(NbGa)_(5)O_(12)晶体的坩埚下降法生长及光学性能研究

使用坩埚下降法成功生长出了镱离子掺杂钙铌镓石榴石晶体(Yb∶Ca_(3)(NbGa)_(5)O_(12))。通过XRD测试分析了晶体的结构,该晶体为立方晶系,晶胞参数a=b=c=12.471。对该晶体进行了拉曼光谱、透过光谱、吸收和发射光谱、荧光寿命等测试,计算了该晶体的吸收截面、发射截面、增益截面等。研究了在空气中退火对该晶体吸收光谱、发射光谱、荧光寿命的影响,退火前在935 nm处吸收截面为1.82×10^(-20)cm^(2),退火后降低为1.40×10^(-20)cm^(2),退火前在1031 nm处的发射截面为0.56×10^(-20)cm^(2),退火后降低为0.40×10^(-20)cm^(2),退火前荧光衰减时间为1.42 ms,退火后为1.32 ms。结果表明,Yb∶Ca_(3)(NbGa)_(5)O_(12)单晶在空气中退火会对晶体的激光性能造成不利影响。

准连续c切Er,Yb:YAl_(3)(BO_(3))_(4)激光器的偏振操控

通过构建谐振腔模型,分析了各向同性固体激光器中两个本征模式相干叠加后的光斑奇异特征。并且实验验证了在不使用任何特定的腔内光学偏振选择元件的情况下,在二极管泵浦的准连续c切Er,Yb:YAl_(3)(BO_(3))_(4)激光器中可以有效操控1.6μm输出激光的偏振态。实现了从部分偏振态转化成稳定的线偏振态,其线偏振方向为可切换的正交特殊情况,均具有21 dB的偏振消光比。同时通过光斑对比,验证了激光器的线偏振输出来源于两个正交本征模式的相干叠加。文中为c切Er,Yb:YAl_(3)(BO_(3))_(4)激光器线偏振光的直接输出与偏振态的调控提供了可靠的方案。

高热稳定CaGdAlO_(4)∶Er^(3+)/Yb^(3+)荧光粉的上转换发光及其温度传感性能

获得具有良好热稳定性和发光性能的非接触式光学温度传感材料是目前的研究热点之一,本工作通过高温固相法制备了Er^(3+)/Yb^(3+)共掺CaGdAlO_(4)∶Er_(x),Yb_(0.10)(x=0.006、0.008、0.010、0.012、0.014)荧光粉,尺寸大小分布在0.6~4.2μm。在980 nm激光激发下,该荧光粉在500~700 nm发射谱由两个发射带组成,528和550 nm处两个较强的绿光发射带,归属于Er^(3+)的^(2)H_(11/2)→^(4)I_(15/2)、^(4)S_(3/2)→^(4)I_(15/2)能级跃迁,663 nm处较弱的红光发射带,归属于Er^(3+)的^(4)F_(9/2)→^(4)I_(15/2)能级跃迁。上转换发光强度最大组分为CaGdAlO_(4)∶Er_(0.010),Yb_(0.10)。300~573 K变温发射谱表明,基于荧光强度比FIR_(528/550)参数,温度传感绝对灵敏度S_(A)从44.4×10^(-4) K^(-1)(@300 K)先增大到52.0×10^(-4) K^(-1)(@445 K)随后减小到49.0×10^(-4) K^(-1)(@573 K)。相对灵敏度S_(R)则从0.95×10^(-2) K^(-1)(@300 K)单调减小到0.27×10^(-2) K^(-1)(@573 K)。冷热循环实验表明该材料的热重复性优于98%。结果表明,CaGdAlO_(4)∶Er_(0.010),Yb_(0.10)荧光粉在光学温度传感领域具有潜在的应用前景。

棒状结构NaGdF_(4):Yb^(3+),Er^(3+)上转换发光性能的研究

以乙二胺四乙酸二钠(EDTD-2Na)为螯合剂,采用水热法合成了棒状结构的NaGdF_(4):Yb^(3+),Er^(3+)纳米粉末。分别借助X射线衍射(XRD)、荧光光谱仪(PL)和扫描显微镜(SEM)对其晶体结构、发光强度和表面形貌进行分析和表征。探究了稀土前驱体、水热温度和水热时间的实验条件对NaGdF_(4):Yb^(3+),Er^(3+)纳米粉末上转换发光强度的影响;研究了氟源和钠源对NaGdF_(4):Yb^(3+),Er^(3+)晶体形貌和上转换发光强度的改善;同时,采用煅烧处理的方法,进一步探究样品的形貌和发光强度收到的影响。实验结果表明NH4F与NaOH作为氟源和钠源及200℃煅烧1 h得到的棒状结构NaGdF_(4):Yb^(3+),Er^(3+)的发光强度最好,色坐标(CIE)绿色发光强度从84%提升到94.88%。

不同激发波长下NaLaF_(4):Er^(3+)/Yb^(3+)的上转换光谱调控研究

为探究不同激发波长(980 nm、1 550 nm)对NaLaF_(4):Er^(3+)/Yb^(3+)上转换发光材料光谱调控的规律和机理,采用水热-固相两步反应法合成一系列不同Er^(3+)/Yb^(3+)掺杂浓度的NaLaF_(4)荧光粉。利用X射线衍射仪(XRD)、荧光分光光度计对材料进行测试,分析其发光性能与机理。结果表明,样品在980 nm激发下呈绿色发光,上转换发光强度随Er^(3+)/Yb^(3+)掺杂浓度增加而呈现先增后减的规律,该发光过程为双光子过程;而在1 550 nm激发下呈红色发光,上转换发光强度随Er^(3+)掺杂浓度增加而呈增强趋势,但随Yb^(3+)浓度增加而降低,发光过程为三光子过程。因此,通过调节激发光波长,在同组分NaLaF_(4):Er^(3+)/Yb^(3+)荧光粉中实现颜色可控的绿、红色发光,对设计新型光谱调控手段和探索新的发光材料具有一定的理论指导意义。

Fabrication of Gd_(2)O_(3)-doped CeO_(2)thin films through DC reactive sputtering and their application in solid oxide fuel cells

Physical vapor deposition(PVD)can be used to produce high-quality Gd_(2)O_(3)-doped CeO2(GDC)films.Among various PVD methods,reactive sputtering provides unique benefits,such as high deposition rates and easy upscaling for industrial applications.GDC thin films were successfully fabricated through reactive sputtering using a Gd_(0.2)Ce_(0.8)(at%)metallic target,and their application in solid oxide fuel cells,such as buffer layers between yttria-stabilized zirconia(YSZ)/La0.6Sr0.4Co0.2Fe0.8O_(3−δ)and as sublayers in the steel/coating system,was evaluated.First,the direct current(DC)reactive-sputtering behavior of the GdCe metallic target was determined.Then,the GDC films were deposited on NiO-YSZ/YSZ half-cells to investigate the influence of oxygen flow rate on the quality of annealed GDC films.The results demonstrated that reactive sputtering can be used to prepare thin and dense GDC buffer layers without high-temperature sintering.Furthermore,the cells with a sputtered GDC buffer layer showed better electrochemical performance than those with a screen-printed GDC buffer layer.In addition,the insertion of a GDC sublayer between the SUS441 interconnects and the Mn-Co spinel coatings contributed to the reduction of the oxidation rate for SUS441 at operating temperatures,according to the area-specific resistance tests.

Yb^(3+)/Nd^(3+)掺杂对Sr_(9)Ga(PO_(4))_(7)∶Cr^(3+)发光性能的影响

近红外荧光粉由于其独特的物理特性和广阔的应用前景吸引了人们极大的研究兴趣。本文通过高温固相反应法合成Sr_(9)Ga(PO_(4))_(7)∶0.8Cr^(3+)近红外荧光粉,使用460 nm蓝光激发样品的发射波长位于833 nm,半峰宽为117 nm。随后引入稀土离子合成Sr_(9)Ga(PO_(4))_(7)∶0.8Cr^(3+),Yb^(3+)和Sr_(9)Ga(PO_(4))_(7)∶0.8Cr^(3+),Nd^(3+)近红外荧光粉。相比Sr_(9)Ga(PO_(4))_(7)∶0.8Cr^(3+),460 nm蓝光激发的Sr_(9)Ga(PO_(4))_(7)∶0.8Cr^(3+),Yb^(3+)同时出现Cr^(3+)和Yb^(3+)特征发射峰,经过光谱分析和荧光寿命变化证明Cr^(3+)-Yb^(3+)存在能量传递通道,最高使Cr^(3+)-Yb^(3+)能量传递效率达80.2%,得益于Yb^(3+)卓越的热稳定性促使整体荧光光谱热稳定性提高约3.7倍。设计合成的Sr_(9)Ga(PO_(4))_7∶0.8Cr^(3+),Nd^(3+)样品调制出833,876,1 060 nm的多峰发射,显著拓宽了近红外光谱范围。最终,讨论了荧光粉在温度传感和无损检测领域的应用,证明该系列荧光粉具有广阔的应用前景。

Lu_(2)O_(3):Yb,Tm/MC540纳米材料的制备及研究

以水热反应及后续的高温煅烧过程为合成手段,成功制备了Lu_(2)O_(3):Yb,Tm纳米材料。XRD结果显示所得样品为纯Lu2O3晶相。且SEM结果表明所得样品由不规则形状组成,粒径在100nm左右。随后通过搅拌吸附过程负载部花青(MC540)光敏剂,得到Lu_(2)O_(3):Yb,Tm/MC540纳米材料。然后以肺癌细胞(A-549细胞)为模型,研究了Lu_(2)O_(3):Yb,Tm/MC540纳米材料的抗肿瘤活性。结果表明,在650nm的红光照射下,上述材料对肺癌A-549细胞具有明显的光动力杀伤疗效。

Upconversion Luminescence Properties of Ho^(3+),Tm^(3+),Yb^(3+) Co-Doped Nanocrystal NaYF_4 Synthesized by Hydrothermal Method

Nanocrystal of upconversion （UC） phosphor Ho^3＋, Tm^3＋ , and Yb^3＋ co-doped NaYF4 was prepared by the hydrothermal method in the presence of the complexing agent EDTA. Under 980 nm diode laser excitation, the impact of different concentrations of Ho^3＋ ion on the UC luminescence intensity was discussed. The law of luminescence intensity versus pump power shows that the 474 nm blue emission, 538 nm green emission, and 642 nm red emission are all due to the two-photon process, while the 450 nm blue emission is a three-photon process. The UC mechanism and processes were also analyzed. The sample was characterized by transmission electron microscopy （TEM） and X-ray diffraction （XRD）. The result shows that Ho^3＋ ,Tm^3＋ , and Yb^3＋ co-doped NaYF4 prepared by the hydrothermal method exhibits a hexagonal nanocrystal.

Up-Conversion Properties of Oxy-Fluoride Glasses Co-Doped with Ho^(3+) and Yb^(3+)

Oxy-fluoride glasses with composition of 25SiO2-65PbF2-9.4AlF3-0.1HoF3-0.5YbF3 were prepared. Their up-conversion fluorescence characteristics were investigated by 980 nm laser. Two emission peaks were observed at 540 and 650 nm. The up-conversion mechanism and processes were analyzed. The relationship between pumping power and relative intensity of emissions was discussed. From the dependence, it is known that the emissions centered at 540 and 650 nm are both attributed to two-photon process.

Laser Cooling Using Anti-Stokes Fluorescence in Yb^(3+)-Doped Fluorozirconate Glasses

The fluorozirconate glasses ZBLANP( ZrF\-4-BaF\-2-LaF\-3-AlF\-3-NaF-PbF\-2) doped with different Yb\+ 3+ concentration were prepared. The Raman spectra and absorption spectra are measured to substantiate the existence of phonon-assisted emission. After analyzing the normalized absorption spectra of samples with different Yb\+ 3+-doped concentration, we calculated the maximum cooling effect in the 3 wt% Yb\+ 3+-doped sample pumped at 1 012.5 nm. The corresponding cooling capability is about -4.09 ℃/W and the cooling efficiency reaches 1.76%.

Investigation on Preparation and Fluorescence Properties of Oxy-Fluoride Glass Co-Doped with Er^(3+) and Yb^(3+)

The glass sample based on the composition of 45PbF_2-45GeO_2-10WO_3 co-doped with Yb^(3+)/Er^(3+) was prepared by the fusion method in two steps: melted at 950 ℃ for 20～25 min then annealed at 380 ℃ for 4 h. Through the V-prism it is found that the refractive index of host glass and the sample are 1.517 and 1.65 respectively. The transmittance was observed by using the ultraviolet-visible-infrared spectrometer in the wavelength range from 0.35 to 2.5μm. The transmittance of the host glass is beyond 73%. That of the sample is beyond 50% and there are characteristic absorption peaks of rare-earth ions. The emission spectrum was measured by using the Hitachi F-4500 fluorescent spectrometer pumped by 980 nm semiconductor laser. There are a strong emission peak at 530 nm and a weak peak at 650 nm.

Optical temperature sensor based on up-conversion fluorescence emission in Yb^(3+):Er^(3+) co-doped ceramics glass

yb^3＋：Er^3＋ co-doped oxy-fluoride ceramics glass has been prepared. The mechanism of up-conversion emissions about Er^3＋ was discussed, and the temperature properties of green up-conversion fluorescence between 303 and 823 K were investigated. The results show that the sensitivity of this sample reaches its maximum value, about 0.0047 K^-1, when the temperature is 383 K, indicating that this kind of sample can be used as high temperature and high sensitivity optical temperature sensor.

Spectroscopic properties and mechanism of Tm^(3+)/Er^(3+)/Yb^(3+) co-doped oxyfluorogermanate glass ceramics containing BaF_2 nanocrystals

Transparent Tm^3＋/Er^3＋/yb^3＋ co-doped oxyfluorogermanate glass ceramics containing BaF2 nanocrystals are prepared. Under excitation of a 980-nm laser diode （LD）, compared with the glass before heat treatment, the Tm^3＋/Er^3＋/yb^3＋ co-doped oxyfluorogermanate glass ceramics can emit intense blue, green and red up-conversion luminescence and Stark- split peaks; X-ray diffraction （XRD） and transmission electron microscope （TEM） results show that BaF2 nanocrystals with an average diameter of 20 nm are precipitated from the glass matrix. Stark splitting of the up-conversion luminescence peaks in the glass ceramics indicates that Tm^3＋, Er^3＋ and （or） Yb^3＋ ions are incorporated into the BaF2 nanocrystals. The up-conversion luminescence intensities of Tm^3＋, Er^3＋ and the splitting degree of luminescence peaks in the glass ceramics increase significantly with the increase of heat treat temperature and heat treat time extension. In addition, the possible energy transfer process between rare earth ions and the up-conversion luminescence mechanism are also proposed.

Intense up-conversion emissions of yb3＋/Dy3＋ co-doped A12O3 nanopowders prepared by non-aqueous sol-gel method＊

yb3＋/Dy3＋ co-doped A1203 nanopowders have been prepared by the non-aqueous sol-gel method and their up- conversion photoluminescence spectra are measured under excitation by a 980-nm semiconductor laser. The results show that there are comparatively abundant spectra of up-conversion emissions centered at 378, 408, 527 and 543, and 663 nm, corresponding to 4C9/2→ 6H13/2, 4C9/2→ 6Hll/2, 4115/2 → 6H13/2, and 4F9/2 →6Hll/2 transitions of Dy3＋, respectively. Two-photon and three-photon processes are involved in ultraviolet, violet, green, and red up-conversion emissions. The energy transition between Yb3＋ and Dy3＋ is discussed.

Upconversion Properties of LiNbO_3 Single Crystals Co-doped with Ho and Yb

The IR-to-visible upconversion fluorescent crystals, Yb：Ho：LiN-bO3, with a constant Ho^3＋ concentration （0.1 mol%） and different doping concentrations of Yb^3＋ （0.5, 1.5, 2.0, 2.5, 3.0 tool%） are synthesized by Czochralski method in air atmosphere. X-ray diffraction shows that the obtained crystal is a single phase of LiNbO3 and the rare-earth ions occupied the Li^＋ or Nb^5＋ sites instead of the interstitial sites. Under 980 nm excitation, green and red emission bands due to the Ho^3＋ （^5S2, ^5F4）/^5I8 and Ho^3＋ ^5F5/^5I8 energy transitions are observed in these samples, respectively. Power dependence studies on these samples with different Yb^3＋ dopant concentrations indicate that the red and green emissions are based on a two-photon process. The intensities of the red and green upconversion fluorescence increase with Yb3＋ ions of 0-2.0 mol% because of an increased Yb^3＋ sensitization, but decrease at higher concentrations owing to the back-energy transfer between the Yb^3＋ and Ho^3＋ ions.

Tm^(3+)-doped tellurite glass with Yb^(3+) energy sensitized for broadband amplifier at 1400–1700 nm bands

A kind of novel experiment was disclosed as it possessed two bands of fluorescence emission at 1.4 and 1.6 μm, which were perfectly complimentary to the current C band of optic communication. The fluorescence was based on energy transfer and up-conversion processes between Tm^3＋ and Yb^3＋ under direct pumping of 975 nm LD. The spectra and lifetimes of Tm^3＋ fluorescence in the tellurite glass were described. The corresponding fluorescence characteristics and energy migration process were analyzed by the method of lifetime and intensity comparison. The mechanism of the up-conversion based IR fluorescence was presented upon analyzing the multi-photon pumping process. The potential advantages of Tm^3＋/Yb^3＋ co-doped tellurite glass as amplifier material were concluded.