TABLE OF CONTENTS At first sight a nanoparticle is defined as a ball or a ball-like molecule which consists of a few 10 to some 10,000 atoms interconnected by interatomic forces but with little or no relationship to a solid state. However, this intuitive concept is not fulfilled in many cases. A first example is a nanocrystalline Si particle which is embedded into an amorphous matrix. Other examples are nanoparticles which are compressed to bulk ceramic or surface layers. It should be considered that deposited nanoparticle layers differ from uniform layers, particularly due to the presence of grain boundaries, which leads to different electrical and optical behavior.
First of all, a container is filled with stainless steel balls of a few millimeters in diameter. The material to be crushed is added in the form of a powder of about 50 ?m diameter grain size. After filling the container with liquid nitrogen, a rotating shaft grinds the material. The grinding periods are within the range of minutes to some 100 hours. This process is simple; its weakness, however, lies in the fact that the grinding balls contribute to impurities.
A typical system is shown in Fig. 5.2. The operation occurs in an evacuated chamber with a pressure of 10 ?5 Pa. After mounting the raw material on one or more crucibles, it is evaporated thermally, by an electron gun, or by ion sputtering. The evaporated atoms or molecules unite and...
