The Emergence of Metallic Properties in Free Metal Clusters in a Molecular Beam

分子束中自由金属簇中金属性质的出现

• 批准号: 1006352
• 负责人: Walter De Heer
• 金额: $ 42万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-15 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1006352&HistoricalAwards=false
• 关键词: Emergence; Metallic; Properties; Free; Metal

****NON-TECHNICAL ABSTRACT****There is an increasing interest in the properties of nanoscopic objects. Yet little is known about the properties of the very smallest metal particles, or clusters, which consist of only a few atoms. It is possible to produce these extremely small particles and to study their properties in a vacuum chamber. This individual investigator award supports a project that will produce a beam of small metallic clusters, which are subsequently cooled to extremely low temperatures. Beams of these particles are then deflected in electric and magnetic fields. The magnetic deflections provide critical information about the magnetic properties of the clusters, which can be compared with magnetic properties of bulk materials. Deflections in electric fields show whether these small metal particles conduct electricity or not. There is some evidence that certain metal clusters have properties akin to superconductivity even at room temperature. These fundamental studies will provide important information about what makes a metal a metal. They will also indicate whether specific metal clusters may be useful for nanotechnology applications such as magnetic recording. Graduate and undergraduate students will learn a variety of experimental techniques that will prepare them for future positions in academia or industry. The training they receive will provide them with the skills needed to become forefront researchers in the properties of nanoscopic electronic objects. This award receives funding from the Division of Materials Research and the Division of Physics.**** TECHNICAL ABSTRACT****This individual investigator award supports a project that addresses the fundamental question of how metallic properties develop in metallic clusters as a function of size. Beams of small metal clusters with from one to several hundred atoms are produced in a cryogenic cluster source using the pulsed laser vaporization method and their properties are studied in high vacuum as they fly from the source to a position sensitive mass analyzer that can simultaneously measure both the mass and the positions of the clusters. Clusters with temperatures of about 20 K are essentially in their electronic and vibrational ground states and therefore are ideally suited for studying the ground state properties of the material. In the bulk, metals do not tolerate a voltage difference and therefore bulk metal objects cannot have electric dipole moments. Hence electric dipole measurements of small clusters will provide information on the emergence of this important metallic property. Molecular beam electron spin resonance measurements of the magnetic moments of paramagnetic clusters will trace the size evolution of the g-values in small alkali clusters and in niobium clusters. In the latter case these measurements may provide insight into a possible connection between a ferroelectric state and superconductivity. Graduate and undergraduate students will learn a variety of experimental techniques that will prepare them for future positions in academia or industry. The training the receive will provide them with the skills needed to become forefront researchers in the properties of nanoscopic electronic objects. This award receives funding from the Division of Materials Research and the Division of Physics.

* 非技术摘要 * 纳米物体的性质越来越受到关注。然而，人们对最小的金属颗粒或簇的性质知之甚少，这些金属颗粒或簇仅由几个原子组成。 有可能生产这些极小的颗粒，并在真空室中研究它们的性质。 这项个人研究奖支持一个项目，该项目将产生一束小金属簇，随后将其冷却到极低的温度。 然后这些粒子束在电场和磁场中发生偏转。 磁偏转提供了关于团簇的磁性质的关键信息，这些信息可以与块体材料的磁性质进行比较。 电场中的偏转表明这些小金属颗粒是否导电。 有一些证据表明，某些金属团簇甚至在室温下也具有类似于超导性的性质。 这些基础研究将提供关于金属是如何成为金属的重要信息。 它们还将表明特定的金属簇是否可用于纳米技术应用，如磁记录。 研究生和本科生将学习各种实验技术，为他们将来在学术界或工业界的职位做好准备。 他们接受的培训将为他们提供成为纳米电子物体特性的前沿研究人员所需的技能。 该奖项由材料研究部和物理学部资助。技术摘要 * 这个个人研究奖支持一个项目，该项目解决了金属团簇中金属性质如何随尺寸变化的基本问题。 用脉冲激光蒸发方法在低温团簇源中产生具有一到几百个原子的小金属团簇束，并在高真空中研究它们的性质，因为它们从源飞到位置敏感质量分析器，该分析器可以同时测量团簇的质量和位置。 温度约为20 K的团簇基本上处于其电子和振动基态，因此非常适合研究材料的基态性质。 在块体中，金属不耐受电压差，因此块体金属物体不具有电偶极矩。 因此，电偶极测量的小集群将提供信息的出现，这一重要的金属属性。 分子束电子自旋共振测量的顺磁性团簇的磁矩将跟踪在小碱金属团簇和铌团簇的g值的大小演变。在后一种情况下，这些测量可以深入了解铁电态和超导性之间可能的联系。研究生和本科生将学习各种实验技术，为他们将来在学术界或工业界的职位做好准备。 接受的培训将为他们提供成为纳米电子物体特性的前沿研究人员所需的技能。该奖项由材料研究部和物理部资助。