Confinement and Scaling of 4He at the Superfluid Transition

9972287 Gasparini这是一个凝聚态物理项目，采用微尺度细胞来研究氦-4的临界行为。当与其体积极限相比时，在相关长度尺度上小的系统的性质被极大地修改。在相变附近尤其如此。通常不相关的问题，如样品的形状或其表面，现在很重要。了解这些小系统具有广泛的意义。这在应用领域也是相关的，例如考虑到设备的持续小型化。理论上也是如此，因为计算常常涉及从小样本到大样本的外推，而这种外推并不总是合理的。即将进行的研究结合了硅技术和直接晶片键合，以形成引入液氦的小型结构。研究的是这种液体在相变附近的性质。研究生和本科生都参与了这项工作。学生接受硅加工，低温技术以及各种实验技术和控制方面的培训。诊断工具包括激光光学和红外成像。学生接受广泛的培训与研究人员在不同的实验室，无论是在校园和国家设施互动。这些学生将从事教育和技术开发方面的各种职业。%人们认为材料具有某些性质，这些性质不取决于它们的大小或形状。无论样品多么小，金属仍然是金属。这在一定范围内是正确的。然而，这显然是有限度的。人们可能会认为，一百万个原子，或者一千个原子，可能是人们所能达到的最低限度。一般来说，人们不知道这个问题的答案，它需要对特定的属性和材料进行研究。通常非常小的样品将显示新的和不同的属性。这在设备的电子化中具有技术含义。即将进行的研究将涉及对经历超流体相变的少量氦-4的测量。它需要使用硅技术，以及在以前的工作中开发的独特工艺，以构建数百个原子的小结构。参与这项工作的学生，无论是研究生还是本科生，都将接受广泛的技术培训。这将包括使用康奈尔大学国家纳米纤维设施的设施，以及各种诊断和实验测量的当地设施。这些学生将在他们的培训很好地多样化，并能够继续在工业和学术界的职业生涯。

9972287GaspariniThis is a condensed matter physics project employing micro-scale cells to investigate the critical behavior of helium-4. Properties of a system which is small on a relevant length scale are greatly modified when compared to its bulk limit. This is especially true near a phase transition. Issues which are normally irrelevant, such as the shape of the sample or its surfaces now matter. Understanding of these small systems has wide implications. This is also relevant in the area for applications, given for example the continued miniaturization of devices. It is also true for theoretical reasons, since often calculations involve the extrapolation, not always justified, from a small to a large sample. The research to be done combines silicon technology and direct wafer bonding to form small structures in which liquid helium is introduced. It is the properties of this liquid near a phase transition which is studied. Graduate and undergraduate students are involved in this effort. The students are trained in silicon processing, low temperature technology, and a variety of experimental techniques and controls. Diagnostic tools involve laser optics and infrared imaging. Students receive an broad training interacting with researchers in different laboratories, both on campus and at national facilities. These student move on to a variety of careers in education and technology development.%%%One thinks of materials as having certain properties which do not depend on their size or shape. A metal will remain a metal no matter how small the sample. This is true within certain bounds. However, there is clearly a limit to this. One might think that a million atoms, or perhaps a thousand, might be as low as one could go. One does not know in general the answer to this, it requires investigations for specific properties and materials. Often very small samples will display new and different properties. This has technological implications in miniaturizations of devices. The research to be done will involve measurements of a small quantity of helium-4 undergoing a superfluid phase transformation. It requires the use of silicon technology, and a unique process developed in previous work, to construct structures as small a few hundred atoms. Students involved in this work, both graduate and undergraduates, will receive a broad technical training. This will include the use of facilities at the National Nanofabrication Facility at Cornell University, and local facilities for various diagnostic and experimental measurements. These students will be well diversified in their training, and able to move on to careers both in industry and academia.