Passivation nanocrystalline materials

One of the great issues in the field of silicon clusters is to understand their photoluminescence (PL) and finally to tune the PL emission by controlling the synthetic parameters. The last two chapters deal with this problem. In experiments described by F. Huisken et al. in Chapter 22, thin films of size-separated Si nanoparticles were produced by SiLL pyrolysis in a gas-flow reactor and molecular beam apparatus. The PL varies with the size of the crystalline core, in perfect agreement with the quantum confinement model. In order to observe an intense PL, the nanocrystals must be perfectly passivated. In experiments described by S. Veprek and D. Azinovic in Chapter 23, nanocrystalline silicon was prepared by CVD of SiH4 diluted by H2 and post-oxidized for surface passivation. The mechanism of the PL of such samples includes energy transfer to hole centers within the passivated surface. Impurities within the nanocrystalline material are often responsible for erroneous interpretation of PL phenomena. 

Key words nanocrystalline materials, electrochemical corrosion, passivation, semiconductive properties, pit initiation and growth. 

Chapter 1 provides an overview of the current rmderstanding of the problem of corrosion. The chapter also provides a brief introduction to nanomaterials in this context. Chapter 2 discusses corrosion basics with referetrce to nanostmctured materials. Chapter 3 addresses theoretical aspects of grain size reduction on corrosion with a model example and comparison with experimental resirlts of nanocrystalline zirconium and its alloys. Chapter 4 provides a good accoimt of the relevant electrochemical aspects of nanostructured materials. The nature of passive film and its correlation with nanocrystallization are explained. Chapter 5 gives a good description of fabrication of electrodeposited nanostructured materials. 

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