Lattice Vibration and Heat Transport in Dielectric Solids

通过测量衬底的热流，研究了抛光晶体硅衬底上金属薄膜和介质薄膜的波尔无序现象。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机械松弛现象观察的影响。薄金属薄膜和介电薄膜将沉积在硅桨状振荡器上。这项技术已经得到了改进，因此它具有足够的灵敏度，可以检测厚度小于1nm的非晶薄膜。要回答的一个问题是，所有非晶固体的特征松弛是否也可以在极薄的薄膜中观察到，或者仅在扩展的三维物体中观察到。金属薄膜或电绝缘体在现代技术中发挥着越来越重要的作用，例如在半导体工业中作为集成电路的元件。目前的研究重点是通过测量其热学和弹性特性来表征这类薄膜。一个具体的例子是富勒烯的微晶膜（巴基球）。除了探索它们的无序性外，还将研究这种薄膜储存气体（如氦或氢）的潜力。初步测量表明氦具有极高的溶解度。如果氢能达到类似的溶解度，这将在能量储存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. ***