Lattice Vibration and Heat Transport in Dielectric Solids

9115981通过测量衬底中的热流，研究了抛光单晶硅衬底上金属和介质薄膜中的波尔无序。在几度K以下，声子不会在衬底中散射，因此观察到的任何散射都是由薄膜中的无序引起的。第二个研究集中在维度对观察机械松弛现象的影响。将在硅桨振荡器上沉积金属薄膜和介电薄膜。这项技术已经得到改进，因此它足以灵敏地检测厚度小于1 nm的非晶膜。需要回答的问题之一是，所有非晶态固体特有的弛豫是否也可以在极薄的薄膜中观察到，或者只在延伸的三维体中观察到。金属薄膜或电绝缘体在现代技术中扮演着越来越重要的角色，例如作为半导体工业集成电路中的元件。目前的研究重点是通过测量薄膜的热性能和弹性性能来表征这种薄膜。一个具体的例子是富勒林(巴基球)的微晶膜。除了探索它们的无序性外，还将研究这种薄膜存储氦或氢等气体的潜力。初步测量表明，氦具有极高的溶解度。如果氢也能达到类似的溶解度，这将在能量存储方面有相当大的实际应用。***

9115981 Pohl Disorder in thin metallic and dielectric films on polished crystalline silicon substrates is investigated by measuring heat flow in the substrate. Below several degrees K, the phonons will not be scattered in the substrate; thus any scattering observed will be induced by the disorder in the films. A second study focuses on the effect of dimensionality on the observation of mechanical relaxation phenomena. Thin metallic and diekectric films will be deposited on silicon paddle oscillators. The technique has been refined so that it is sufficiently sensitive to detect amorphous films less than 1nm thick. One of the questions to be answered is whether the relaxation which is characteristic of all amorphous solids can also be observed in extremely thin films, or only in extended, three dimensional bodies. % % % Thin films of metals or electrical insulators play an increasingly important role in modern technology, e.g. as components in integrated circuits in the semiconductor industry. The current study focuses on characterizing such films by measuring their thermal and elastic properties. A specific example are microcrystalline films of fullerines (buckyballs). In addition to exploring their disorder, the potential of such films for storing gases like helium or hydrogen will be investigated. Preliminary measurements have sshown an extremely high solubility for helium. If a similar solubility could be achieved for hydrogen, this could have considerable practical applications for energy storage. ***