氧化铝-8YSZ叠层制备极限电流型氧传感器

采用氧化铝作支撑材料制备了一种新型结构的极限电流型氧传感器。该传感器经由氧化铝粉和8YSZ粉分别压片并烧结成瓷,再经厚膜丝网印刷及叠压共烧制成。在温度为973 K(700℃)、氧体积分数为1.4%~14%条件下,对该传感器的气敏特性和响应时间进行了研究。结果表明:该传感器在上述氧浓度范围内具有较好的电流平台特性,且极限电流与氧浓度有良好的线性关系;气体在该传感器中的扩散为Knudsen扩散;该传感器的响应时间在8 s以内且呈现较好的重复性,长时间工作性能较稳定。     

用La2MoWO9作固体电解质的极限电流型氧传感器

采用固相反应法,制备了氧离子导体La2MoWO9和混合导体La0.6Sr0.4Fe0.8Co0.2O3,并分别作为基体材料,制成了极限电流型氧传感器。利用两端子法,对氧传感器在500℃时不同氧分压下(pO2为(0~2.12)×104Pa)电流与电压的关系进行了测量。结果表明:用La2MoWO9作为氧传感器的固体电解质材料是可行的,即可以得到极限电流平台(pO2为1.70×104Pa,I为1.5mA),且极限电流与氧分压成线性关系。     

钇稳定ZrO2界限电流型微氧氧传感器的设计

从理论和实验角度,对钇稳定ZrO2界限电流型微氧氧传感器的量程与结构设计的关系进行了分析研究。结果显示:被测环境氧摩尔浓度应小于5%,被测环境氧浓度与氧传感器输出极限电流的数值,基本成线性关系;通过(5 000~50000)×10–6;(500~20000)×10–6;(100~10000)×10–6;(50~1000)×10–6四档测量范围的划分以及S/L比的合理设计,可以实现钇稳定ZrO2界限电流型微氧氧传感器对低氧浓度的准确测量。     

Pt/YSZ电极结构形貌的表征

根据YSZ型氧传感器中O在电极表面的吸附、扩散以及Pt/YSZ界面O(Pt电极中)/O2(YSZ中)的传递的机理,提出了一种对Pt /YSZ电极界面进行定量表征的模型。用此模型对不同烧结温度下的电极形貌Pt/空气/ YSZ三相界面长度进行了定量表征,同时,采用复阻抗测试技术和氧传感器响应测试技术对表征结果的合理性进行了验证。理论推算和试验结果都表明:采用1 000℃,1 h烧结的电极形貌具有最佳的电化学性能。     

Pt/YSZ泵氧电极响应特性研究

以钇稳定氧化锆(简称YSZ)为固体电解质,Pt/YSZ为电极材料,制备了NOx传感器。采用计时电流法(chronoamperometry)和电化学阻抗法(EIS)研究了Pt/YSZ泵氧电极对O2和NO的响应特性。结果表明,氧气浓度基本不影响电极活化能,在相同测试温度下,随着氧气浓度的增加,泵电流呈直线增加,界面电阻降低;氧气浓度一定时,泵电流与测试温度呈指数关系。特定测试温度下,随着NO浓度增加,泵电流呈指数增长趋势,而界面电阻逐步降低。     

砷化镓中的锡扩散

一、序言砷化镓中的 n 型杂质,已知的有 T_e、S、Si、Sn 等。在制作器件的时候,n 或 n~ 层几乎都是采用外延生长法形成的。这是因为外延生长比扩散法温度低,并且可以制得优质的单晶(在300°K 下,μ=7000～8000厘米~2/伏秒,n=10~(14)～10~(15)厘米~(-3))。然而,在外延生长法中,用目前的技术要把 GaAs 外延层厚度控制为1～2μ重复性相当差。对单晶的要求不太严格时,用扩散法制备很薄的 n~ 层是很有效的。有关 GaAs 中扩散的报告,谈的几乎都是 p 型杂质 Zn 的扩散。之所以致力研究 Zn扩散,是因为它可以在外延生长温度或更低的温度下进行。而用外延生长法很难制得优     

YAG单晶中的氧扩散

在1060—1550℃温度范围内,以~(18)O作示踪元素,用气体—固体同位素转换技术测定YAG单晶中氧的自扩散系数。在原生态的晶体中,氧离子的体扩散系数可由D=5.24×10~(-7)exp(-325000J/mol/RT)m~2/s表示。这个系数取决于扩散退火前的热处理气氛。晶体氧空位电平的效应归因于色心缺陷的形成和所含杂质离子的化合价变化。认为这种活化能是由于氧离子迁移所致。YAG单晶小面区的氧空位浓度比无小面区的要高。     

扩散温度和时间对晶体硅太阳电池性能的影响

研究了薄层方块电阻对单晶硅太阳电池的开路电压(Voc)、短路电流(Isc)、填充因子(FF)和转换效率(η)的影响。通过控制扩散温度和时间制备了具有不同薄层方块电阻的单晶硅太阳电池。结果表明:当扩散温度和时间分别为863℃和1 050 s时,电池性能得到了有效的改善,其平均开路电压、短路电流、填充因子和转换效率分别为0.64 V,5.58 A,0.755和17.3%。     

硅中氧的结构组态及热扩散行为

利用变温FTIR测量和变温Hall效应测量方法,探讨了在室温(RT)至475℃温度范围内,硅中9μm峰的中心位置及其红外吸收系数随温度变化的规律.实验证实了氧在硅单晶中存在二种不同的组态:在RT—325℃范围内为Si_2O组态,其束缚能为E_b～0.8—1.0eV;在325—475℃范围内,Si_2O组态和准自由间隙氧原子组态同时并存,准自由氧原子扩散所须克服硅晶格的势垒为E_L～1.5—1.6eV.由此很好地解释了硅中氧的热扩散行为.     

掺杂Y2O3氧化锌压敏陶瓷的显微组织及电性能

采用掺杂Y2O3、高能球磨和低温烧结技术,制备了电位梯度(ES)达1 934~2 197 V/mm、非线性系数(α)为20.8~21.8、漏电流(IL)为0.59~1.04μA、密度(ρ)为5.46~5.57 g/cm3的氧化锌压敏陶瓷。利用电子探针观察了压敏陶瓷的分布和形貌。X-射线衍射仪(XRD)证实了Y4样品(x(Y2O3)=0.1%)中Y2O3相的存在。随着Y2O3含量的增加,ES、α提高,IL、ρ和晶粒尺寸(D)降低;施主浓度(Nd)及界面态密度(Ns)降低,而势垒高度(φB)和势垒宽度(ω)增大。     

Current conduction mechanism and gas adsorption effects on deviceparameters of the Pt/SnOx/diamond gas sensor

This paper presents the results from analysis and modeling of the gas sensing performance, current conduction and gas detection mechanisms, and adsorption effects on device parameters of a Pt/SnO_x/diamond-based gas sensor. The sensor is sensitive and demonstrates high, repeatable, and reproducible reaction. The sensor response in seconds to small concentrations of O₂, CO, and H ₂ gases. The current conduction mechanism of the diamond-based CAIS (catalyst/adsorptive-oxide/intrinsic-diamond/semiconductor-diamond) diode was found to be dominated by space charge limited conduction in the forward bias region and tunneling in the reverse bias region, distinctively different from silicon based sensors. While gas adsorption causes a change in the barrier height and tunneling factor, no significant change was observed in the ideality factor over the temperature range investigated. The detection mechanism of the sensor is attributable to the change in occupancy ratio of the oxygen vacancies of the adsorptive oxide layer upon oxygen exposure, increasing the contact potential between adsorptive-oxide and intrinsic-diamond     

La_2O_3掺杂WO_3纳米粉体的制备及气敏性能

以胶溶法制备的WO3和sol-gel法制备的La2O3为原料,采用固相研磨法制备了掺杂剂质量分数w(La2O3)为0.5%～7.0%的La2O3-WO3纳米粉体,利用XRD、TEM等测试手段分析了粉体的微观结构,采用静态配气法测试了由所制粉体制成的气敏元件对丙酮的气敏性能。结果表明,制得的La2O3-WO3纳米粉体结晶良好,平均粒径为60nm;当工作电压为4.5V,w(La2O3)为5.0%时,粉体在600℃下烧结制得的气敏元件对体积分数为50×10–6的丙酮的灵敏度可达37.6,响应时间和恢复时间分别是1s和11s。     

Microstructure and properties of melt-processed Bi-2212 (Bi2Sr2CaCu2Ox)

Microstructural development and properties during melt processing of Bi-2212 were investigated with regard to the production of superconducting oxides in bulk shape for the application in electrical engineering. Oxygen loss during heating and melting leads to incongruent solidification on cooling and therefore multiphase microstructures. Phase compositions depend on oxygen stoichiometry, which is determined by oxygen partial pressure, maximum sintering temperature as well as cooling rate. During annealing, solid/liquid and subsequent solid/solid reactions yield high volume fractions of 2212. The oxygen absorption and the 2212 formation mechanism and its kinetics are strongly correlated. The11905→2212 transformation proceeds via intermediate states of high planar defect density and is promoted by frequent stacking faults, that allow diffusion of Ca- and Cu-atoms over short distance. Microstructures of the 2212 phase were also controlled by variations of the cation stoichiometry leading to an improvement of the superconducting properties.     

低温微波水热法制备氧化钇稳定氧化锆

微波水热合成法是新型的纳米粉体材料制备方法,它与常规水热法相比,反应时间更短、反应温度更低,并且微波的非热效应影响产物晶型的形成。立方相氧化钇稳定氧化锆(YSZ)陶瓷材料是制作氧传感器、固体氧化物燃料电池及高温湿度传感器等多种功能元器件的核心原材料。采用可程序化控制的MARS-5微波消解仪实现了微波水热合成,反应温度100~120℃,反应时间1~5h,在强碱环境下制备氧化钇稳定氧化锆纳米粉体,而常规水热法制备氧化锆的温度一般为190~250℃。采用X射线衍射、热分析等方法,研究了温度、时间、pH和Y2O3含量对产物粒度和晶型的影响,使用了Rietveld方法进行定量分析、粒度计算。结果显示,与常规水热法相比,微波水热法不仅缩短了反应时间,并且影响产物的结构组成。分析表明,微波加速反应的机理可以用晶粒旋转驱动的晶粒聚合解释,而微波的介电加热效应,微波离子传导损耗等是加速化学反应的主要原因。     

Annealing properties of high quality Nb/Al-AlOx/Nbtunnel junctions

High quality, low current density Josephson tunnel junctions are obtained from Nb/Al-AlO_x/Nb trilayers, using a SNAP process to define the junction area. A large number of junctions has been annealed in air for several hours at temperatures as high as 300°C. The most relevant effects observed were: a) a marked decrease of the junction current density and a related increase of the normal-state resistance; b) under suitable conditions, a barrier quality improvement measured in terms of the subgap current and of the quality factor V_m; the most remarkable result is a V_m as large as 2.5 V at T=1.2 K for our best sample. We believe that oxygen diffusion through the Nb grain boundaries is the main mechanism responsible for the normal-state resistance increase and that device quality variation is closely related to the modification of the barrier interfaces     

Evaluation of DC-sputtered Glassy TaCoN Thin Film for Copper Metallization

The failure mechanism of the TaCoN barrier for copper metallization was examined using films by direct current (dc) magnetron reactive sputtering at various nitrogen flow rates. The as-deposited TaCoN films had a glassy structure and were free from intermetallic compounds. Optimizing the nitrogen flow rate during sputtering maximized the thermal stability of the Si/Ta_66.8Co_11.4N_21.8/Cu metallization system up to an annealing temperature of 750°C when the film was deposited using a nitrogen flow rate of 1 sccm, as revealed by using X-ray diffraction, a scanning electron microscope, a four-point probe and a transmission electron microscope. Structural analysis indicated that the failure mechanisms of the studied Si/TaCoN/Cu stacked films involved the initial dissociation of the barrier layer that was annealed at a specific temperature, and the subsequent formation of diffusion paths along which the copper penetrates through the TaCoN barrier layer to react with underlying Si. The high formation temperature of the Cu₃Si phase demonstrated that the studied film was highly stable, indicating that the TaCoN thin film is highly promising for use as a diffusion barrier for Cu metallization.