(113)面硅衬底上自组织生长的GeSi量子点及其光荧光

用透射电子显微镜观察了Si(113)衬底上由固态源分子束外延生长的自组织量子点的形貌,测量了其原生及退火后低温下的光荧光谱.对所得结果进行了分析. 关键词：     

Initiation of a low-pressure glow discharge in a plasma electron source with a ribbon beam

Results are presented from an experimental investigation of a low-pressure glow discharge with a wedge-shaped hollow cathode in a plasma electron source, where this discharge is initiated by reflex and magnetron discharges. Zh. Tekh. Fiz. 69, 135–137 (July 1999)     

Anodic and Cathodic Platinum Dissolution Processes Involve Different Oxide Species

The degradation of Pt-containing oxygen reduction catalysts for fuel cell applications is strongly linked to the electrochemical surface oxidation and reduction of Pt. Here, we study the surface restructuring and Pt dissolution mechanisms during oxidation/reduction for the case of Pt(100) in 0.1 M HClO₄ by combining operando high-energy surface X-ray diffraction, online mass spectrometry, and density functional theory. Our atomic-scale structural studies reveal that anodic dissolution, detected during oxidation, and cathodic dissolution, observed during the subsequent reduction, are linked to two different oxide phases. Anodic dissolution occurs predominantly during nucleation and growth of the first, stripe-like oxide. Cathodic dissolution is linked to a second, amorphous Pt oxide phase that resembles bulk PtO₂ and starts to grow when the coverage of the stripe-like oxide saturates. In addition, we find the amount of surface restructuring after an oxidation/reduction cycle to be potential-independent after the stripe-like oxide has reached its saturation coverage.     

铪元素及其同位素的发现：技术进步和思想发展的共同结晶

1869年，门捷列夫在第一张元素周期表中的锆元素后留出原子量为180的元素位置，预测铪与锆同族。1913年，原子序数和莫斯莱定律的提出揭示了铪元素在周期表中位置排列的实质，为铪元素的发现提供理论基础。20世纪20年代，玻尔理论的发展证实铪与锆同族，指导科学家从锆矿石中寻找铪元素。1923年，赫维西和科斯特借助X射线光谱技术发现铪元素，彰显了X射线光谱技术的独特价值。20世纪30年代以后，同位素理论和质谱技术促成了铪同位素的发现，使人们对铪元素有了新的认识。总之，铪元素及其同位素的发现是技术进步和思想发展的共同结晶。