差分吸收NO2激光雷达光源的设计与实现

为研制一台探测距离3km、分辨率10μg/m3的大气NO₂廓线差分吸收激光雷达,以NO₂的吸收光谱和激光雷达方程为基础,通过数值仿真分析了回波信噪比与水平和垂直方向上大气中气溶胶、NO₂含量的分布、探测距离和几何因子的关系;搭建探测大气NO₂实验系统,开展了大气NO₂浓度实验观测,获得水平及垂直高度0.4km~3.0km内的NO₂浓度实时分布,探测分辨率可达4.717μg/m3,系统稳定可靠。结果表明,采用两台波长为354.7nm、能量不小于100mJ的Nd:YAG激光器分别抽运两台染料激光器的方式,并以C450为染料,可满足差分吸收探测所需的两束波长为λ_on（448.10nm）和λ_off（446.80nm）、能量为8mJ的输出光束。该方法为实用化NO₂差分吸收激光雷达光源的设计及应用提供了理论依据及技术支持。     

傅里叶红外系统监测大气中温室气体的污染特征

研制了一套90 m的开放光路傅里叶变换红外光谱(OP-FTIR)温室气体分析测量设备，并利用该设备开展了CO₂、CH₄和CO质量浓度的高精度检测。OP-FTIR系统反演CO₂、CH₄和CO的光谱区域分别为2102～2250 cm^-1、2920～3140 cm^-1和2172～2210 cm^-1。以采集到的中红外吸收光谱为反演基准，开展了与Picarro温室气体分析仪的对比测试。选取测量期间10 d的数据，研究了温湿度、风向风速与环境大气中CO₂、CH₄和CO质量浓度的关联度，并详细分析了污染物的日变化特征。实验结果表明：研制的OP-FTIR光谱系统监测温室气体质量浓度具有较高的可靠性；温度、相对湿度、风速和风向对当地污染物质量浓度影响显著；CO₂、CH₄和CO质量浓度的时序变化具有明显的周期性变化趋势。将CO、CH₄质量浓度分别...     

基于贝叶斯的大数据模型在大气污染成因分析中的应用

提出了一种基于多维高斯贝叶斯分类算法的复杂系统影响因素的分析方法,并利用大数据方法建立了不同PM_2.5范围的分类模型,结合马氏距离开展了影响因素的关键性分析。以合肥市2013―2018年间的天气与空气质量数据为基础,筛选了PM₁₀、SO₂、NO₂、CO、O₃等8个大气污染的关键影响因素,采用散点矩阵对PM_2.5与这些影响因素的相关性进行了分析。利用高斯贝叶斯分类器建立了基于8个主要参量的PM_2.5大气污染分析模型,研究发现,PM_2.5与CO浓度具有较强的正相关性,对NO₂具有选择性,与O₃具有负相关性,而CO与SO₂对PM2.5的产生存在某种竞争机制。     

新冠肺炎疫情管控期间乌鲁木齐市空气质量变化及原因分析

为研究新型冠状病毒肺炎疫情防控期间乌鲁木齐市空气质量变化特征及其影响因素,选取了2020年乌鲁木齐市两次疫情严格防控期间(2020年1月26日至3月21日和7月20至8月29日)及疫情前后,以及2019年相同时期地面观测站的逐小时空气质量指数(AQI)、颗粒污染物(PM_2.5、PM₁₀)和气态污染物(SO₂、NO₂、CO、O₃)的数据进行对比分析,探究了气态污染物对颗粒污染物二次合成的贡献,并利用地理探测器对影响空气质量的因子进行了定量探测。结果表明：与2019年同期相比,2020年乌鲁木齐市两次疫情防控期间,除O₃外,PM_2.5、PM₁₀、SO₂、NO₂和CO浓度都呈现下降趋势,分别减少了36%、55%、10%、18%和49%;而同疫情严格防控期相比,2020年疫情前后期的AQI、颗粒污染物浓度及气态污染物浓度都要高。说明疫情防控措施在一定程度上减少了乌鲁木齐市颗粒污...     

机载热红外高光谱成像仪的光谱性能测试与初步应用

介绍了机载热红外高光谱成像仪样机的低温光谱仪设计特点,为了检测系统的光谱识别能力,在实验室开展了详细的光谱性能测试。为满足气体探测对超高光谱精度的需求,提出了采用CO₂激光器结合高精度单色仪的方法应用于色散型高光谱成像系统。在实验室对氨气气体进行了准确的红外吸收光谱测试,表明系统可用于气体探测及识别。在此基础上,开展了飞行试验,应用结果表明热红外高光谱可以有效开展城市典型建筑物分类、工业化学气体排放种类和形态监测等应用,特别是后者是目前其它光学遥感手段尚不具备的。以上研究和试验结果表明机载热红外高光谱成像仪已经具备了业务应用能力,后续将在仪器辐射定量化精度的提升方面进一步开展研究工作。     

基于NDIR的多组分危险气体在线监测系统设计

在冶金、石化、化工等工业领域生产过程中会产生大量易燃易爆、有毒有害的多组分危险气体(CO、CO₂、SO₂、NO、NH₃等),这些有害气体容易引发事故。而现有的在线测量预警系统不能满足高集成、低干扰、高灵敏的要求。本文针对影响检测结果的微弱信号、光源调制、气体信号交叉干扰、温度控制等因素,设计了相应的电路和算法,并进行了实验验证。实验结果表明,本文提出的基于锁相放大器电路的微弱信号提取技术、基于MOS管驱动电路的PWM波调制技术、基于融合算法的浓度反演模型,能够实现对五种危险气体(CO、CO₂、SO₂、NO、NH₃)的在线监测,检出限达到0.01%,避免了多种气体之间的交叉干扰,适用于工业生产危险气体在线分析及预警系统,具有广阔的应用前景。     

自供能Bi2O2Se/TiO2异质结紫外探测器的制备与光电探测性能

采用一步水热法合成了不同质量分数的Bi₂O₂Se/TiO₂异质结构,对其进行了X射线衍射、扫描电子显微镜和透射电子显微镜表征,并基于Bi₂O₂Se/TiO₂异质结制备了紫外探测器。实验结果表明：在365 nm紫外光的照射下,Bi₂O₂Se的质量分数为60%时,Bi₂O₂Se/TiO₂异质结探测器的光电探测性能最好,光电流高于Bi₂O₂Se探测器,是TiO₂探测器的7倍;响应时间约为30 ms,是TiO₂探测器的1/6。Bi₂O₂Se/TiO₂异质结探测器的响应度和探测率分别为10^-3A/W、1.08×10⁷cm·Hz^1/2/W,均比...     

核运动对分子谐波强度及产生阿秒脉冲的影响

为了了解核运动对H₂+和T₂+谐波辐射强度及产生阿秒脉冲的影响,采用数值求解薛定谔方程的方法,理论研究了10fs和20fs激光驱动下H₂+和T₂+谐波截止能量附近强度的变化。结果表明,短脉宽驱动下谐波强度满足H₂+>T₂+;而长脉宽驱动下谐波强度满足T₂+>H₂+;根据谐波强度变化规律,在最佳谐波辐射强度下引入半周期激光场可以获得高强度、高能量的谐波平台区,进而获得脉宽为37as的阿秒脉冲。该研究为探测同位素分子及产生高强度及高能量的阿秒脉冲提供了一种新的方案,对激光光学的发展有一定帮助。     

基于跨波长调制和直接吸收光谱的宽量程多气体检测方法

针对可调谐半导体激光吸收光谱技术(Tunable Diode Laser Absorption Spectroscopy,TDLAS)在煤矿、石油化工领域进行气体浓度检测时,遇到的高精度、宽动态范围需求,采用时分复用的方法,将直接吸收光谱技术(Direct Absorption Spectroscopy,DAS)和波长调制光谱(Wavelength Modulation Spectroscopy,WMS)技术的优势相结合,完成了高精度、宽量程和免标定多气体检测系统的设计。设计激光器的驱动为线性扫描输出和叠加不同高频调制扫描输出的周期信号,用于完成高低浓度反演算法的时分复用计算,通过实验优化选择检测气体的吸光度拐点,实现对气体浓度的高精度、宽量程检测。在室温和常压下,通过实验分别对CH₄、CO和C₂H₂三种气体体积浓度进行检测,确定了两种算法最佳拐点吸光度约为0.026 cm^-1。系统对CH₄、CO和C₂H₂三种气体体积浓度的检测量程分...     

气氛环境下Au/CeO2催化剂烧结行为的原位电镜研究

气氛环境下原位研究催化剂的烧结行为,能够为理解催化剂在预处理以及反应条件下的烧结机理和高稳定催化剂的设计提供重要的实验依据。本文以Au/CeO₂模型纳米催化剂为研究对象,利用环境透射电子显微镜原位观察其在O₂与CO气氛下的高温动态烧结过程。实验发现,负载在CeO₂上的Au纳米颗粒在O₂与CO气氛环境中表现出不同的烧结行为,其在O₂气氛下具有较高的烧结速度,同时存在颗粒迁移与聚集长大(particle migration and coalescence, PMC)和奥斯特瓦尔德熟化(Ostwald ripening, OR)两种烧结过程;在CO气氛下烧结速度较慢,烧结过程以OR为主。对比不同气氛环境下烧结后催化剂的表面结构可知,CO增加了CeO₂表面台阶的数量以及表面氧空位浓度,增强了载体对Au颗粒的锚定作用,从而提升Au/CeO₂催化剂的稳定性。     

In-situ monitoring of the growth of Bi2 Te2 and Sb2 Te3 films and Bi2 Te3-Sb2 Te3 superlattice using spectroscopic ellipsometry

In this work, we present in-situ monitoring of the growth of bismuth telluride (Bi₂Te₃) and antimony telluride (Sb₂Te₃) thin films as well as Bi₂ Te₃-Sb₂Te₃ superlattice using a spectroscopic ellipsometer (SE). Bi₂Te₃ and Sb₂ Te₃ films were grown by metalorganic chemical vapor deposition (MOCVD) at 350 C. A44-wavelength ellipsometer with spectral range from 404 nm to 740 nm was used in this work. The optical constants of Bi₂ Te₃ and Sb₂Te₃ at growth temperature were determined by fitting a model to the extracted in-situ SE data of optically thick Bi₂ Te₃ and Sb₂ Te₃ films. Compared to the optical constants of Bi₂ Te₃ and Sb₂ Te₃ at room temperature, significant temperature dependence was observed. Using their optical constants at growth temperature, the in-situ growth of Bi₂ Te₃ and Sb₂ Te₃ thin films were modeled and excellent fit between the experimental data and data generated from the best-fit model was obtained. In-situ growth of different Bi₂ Te₃-Sb₂ Te₃ superlattices was also monitored and modeled. The growth of Bi₂ Te₃ and Sb₂ Te₃ layers can be seen clearly in in-situ SE data. Modeling of in-situ superlattice growth shows perfect superlattice growth with an abrupt interface between the two constituent films.     

New TIT capacitor with ZrO2/Al2O3/ZrO2 dielectrics for 60 nm and below DRAMs

New ZrO₂/Al₂O₃/ZrO₂ (ZAZ) dielectric film was successfully developed for DRAM capacitor dielectrics of 60 nm and below technologies. ZAZ dielectric film grown by ALD has a mixture structure of crystalline phase ZrO₂ and amorphous phase Al₂O₃ in order to optimize dielectric properties. ZAZ TIT capacitor showed small Tox.eq of 8.5 Å and a low leakage current density of 0.35 fA/cell, which meet leakage current criteria of 0.5 fA/cell for mass production. ZAZ TIT capacitor showed a smaller cap leak fail bit than HAH capacitor and stable leakage current up to 550 °C anneal. TDDB (time dependent dielectric breakdown) behavior reliably satisfied the 10-year lifetime criteria within operation voltage range.     

Research of SiO2/InP structure prepared by photo-CVD

The SiO₂ film as an insulator in InP MOS structure was grown by mercury-sensitized photo induced chemical-vapor deposition (photo-CVD) utilizing gaseous mixture of monosilane (SiH₄) and nitrous oxide (N₄O) under 253.7 nm ultraviolet light irradiation. The PHOTOX SiO₂ film (i.e., SiO₂ film prepared by photo-CVD system) deposited at 250° C has a refractive index of 1.46 and breakdown field strength of 7.0 MV/cm. The 1 MHz capacitance-voltage characteristics of the InP MOS diode was measured to study the interface state densities. The minimum value is 1.2 × 10¹¹ cm⁻²eV⁻¹ for the sample prepared at a substrate temperature of 250° C.     

Electrothermal investigation of the switching effect in p-Type TllnSe2, TllnTe2, and TIGaTe2 chain chalcogenide semiconductors

Large p-type TlInSe₂, TlInTe₂, and TlGaTe₂ single crystals have been grown by the Bridgman-Stockbarger method, starting from stoichiometric melts. The first observations of the switching process in p-type TlGaTe₂ single crystal are reported. Current-voltage (I-V) characteristics of symmetrical In/p-TlInSe₂/In, In/p-TlInTe₂/In, and In/p-TlGaTe₂/In structures exhibit two distinct regions: an ohmic region at low current densities and nonlinear regions (S-shape) having negative differential resistance (NDR) at moderate and higher current densities. An electrothermal model was used to explain the nonlinear behavior. The nonlinear behavior of the I–V curves was studied at different ambient temperatures in the 100–340K region; the sample temperature and the threshold voltage of the NDR region were examined as a function of the current density and the ambient temperature, respectively. The electrothermal model is a satisfactory explanation.     

Transport properties of thermoelectric materials for coolers

The Seebeck coefficient, thermal conductivity, electrical conductivity and Hall coefficient of cooler grade, p-and n-type ternary alloys of Bi₂Te₃-Sb₂Te₃-Sb₂Se₃ were measured between 10 and 300 K. Between 300 K and about 150 K the temperature dependence of the transport properties can be explained by assuming nondegeneracy and a lattice scattering mechanism. The difference between the temperature dependence of the Hall effect in n-and p-type alloys can be explained by the presence of sub-bands of light and heavy holes in the valence band of p-type alloys.     

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。     

Excellent performance of gas sensor based on In2O3-Fe2O3 nanotubes

In₂O₃-Fe₂O₃ nanotubes are synthesized by an electrospinning method. The as-synthesized materials are characterized by scanning electron microscope and X-ray powder diffraction. The gas sensing results show that In₂O₃-Fe₂O₃ nanotubes exhibit excellent sensing properties to acetone and formaldehyde at different operating temperatures. The responses of gas sensors based on In₂O₃-Fe₂O₃ nanotubes to 100 ppm acetone and 100 ppm formaldehyde are 25 (240℃) and 15 (260℃), and the response/recovery times are 3/7 s and 4/7 s, respectively. The responses of In₂O₃-Fe₂O₃ nanotubes to 1 ppm acetone (240℃) and formaldehyde (260℃) are 3.5 and 1.8, respectively. Moreover, the gas sensor based on In₂O₃-Fe₂O₃ nanotubes also possesses an excellent selectivity to acetone and formaldehyde.     

不同深宽比GaAs衬底的Al22O3/HfO2复合薄膜材料原子层沉积及能谱分析

利用热原子层沉积（Atomic Layer Deposition, ALD）技术在不同深宽比GaAs衬底上进行了Al2₂O₃/HfO₂复合薄膜的沉积。通过对其表面和能谱进行分析发现,沉积温度对复合薄膜的摩尔比具有较大的影响。随着深宽比的增大,其沉积表面和沟槽内会出现残留物;随着ALD沉积温度的上升,其沉积表面和沟槽内的残留物减少,摩尔比趋向均匀。当深宽比为2.2并利用150 ℃的低沉积温度时,表面及底面基本无残留物。但当深宽比为4.25时,150 ℃沉积明显有大量残留物。只有当温度升高到300 ℃时,表面和沟槽里复合薄膜的残留物才被明显消除。ALD技术可以实现各种器件结构的全方位钝化,这是其他化学气相沉积法无法比拟的。     

Ca3Y2(Si3O9)2:Tb3+绿色荧光粉的光谱特性

采用高温固相法制备了Ca₃Y₂(Si₃O₉)₂: Tb³⁺绿色荧光粉,研究了材料的光学性能。X 射线衍射(XRD)结果显示,掺杂少量的Tb³⁺,并未影响Ca₃Y₂(Si₃O₉)₂材料 的晶相结构。Ca₃Y₂(Si₃O₉)₂:Tb³⁺ 荧光粉的激发光谱由较强的4f^75d1宽带吸收(200～300 nm )和较弱的4f-4f电子跃迁吸收 (300～500 nm)构成,主激发峰位于236nm。取波长分别为236、376和482nm的光 作为激发源时,发现样品的主发射峰均位于544 nm,对应Tb³⁺的⁵D 4→⁷F₅跃迁发射。以236nm 紫外光作为激发源,监测544nm主发射峰,随Tb³⁺浓度 的增大,Ca₃Y₂(Si ₃O₉)₂:Tb³⁺的荧光寿命逐渐减小,但在实验范围内并未出现浓度猝灭现象。     

The effect of Tl2Te3 on the properties of the solid solution (Sb2Te3)0.75.(Bi2Te3)0.25

The effect on transport properties of the addition of 0.5-5% Tl₂Te₃ to p-type solid solutions of antimony and bismuth tellurides was studied. It was found that the addition of Tl₂Te₃ caused a lessening of the increase of hole concentration as low temperatures were approached, resulting in a slower decrease of the Seebeck coefficient with a decrease in temperature. In partial fulfillment of M.Sc. degree, Hebrew University, Jerusalem. Permanent address, Dept. of Inorganic and Analytical Chemistry, Hebrew University, Jerusalem.