title: Advances in fractal germanium micro/nanoclusters induced by gold: microstructures and properties.
abstract: Germanium materials are a class of unique semiconductor materials with widespread technological applications because of their valuable semiconducting, electrical, optical, and thermoelectric power properties in the fields of macro/mesoscopic materials and micro/nanodevices. In this review, we describe the efforts toward understanding the microstructures and various properties of the fractal germanium micro/nanoclusters induced by gold prepared by high vacuum thermal evaporation techniques, highlighting contributions from our laboratory. First, we present the integer and non-integer dimensional germanium micro/nanoclusters such as nanoparticles, nanorings, and nanofractals induced by gold and annealing. In particular, the nonlinear electrical behavior of a gold/germanium bilayer film with the interesting nanofractal is discussed in detail. In addition, the third-order optical nonlinearities of the fractal germanium nanocrystals embedded in gold matrix will be summarized by using the sensitive and reliable Z-scan techniques aimed to determine the nonlinear absorption coefficient and nonlinear refractive index. Finally, we emphasize the thermoelectric power properties of the gold/germanium bilayer films. The thermoelectric power measurement is considered to be a more effective method than the conductivity for investigating superlocalization in a percolating system. This research may provide a novel insight to modulate their competent performance and promote rational design of micro/nanodevices. Once mastered, germanium thin films with a variety of fascinating micro/nanoclusters will offer vast and unforeseen opportunities in the semiconductor industry as well as in other fields of science and technology.
authors.forename: Zhiwen
authors.initials: Z
authors.lastname: Chen
authors.forename: Chan-Hung
authors.initials: CH
authors.lastname: Shek
authors.forename: C M Lawrence
authors.initials: CM
authors.lastname: Wu
authors.forename: Joseph K L
authors.initials: JK
authors.lastname: Lai
mesh_terms: D003460:Crystallization / Q000379:methods*; D004553:Electric Conductivity; D017709:Fractals; D005857:Germanium / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D008863:Microspheres; D008968:Molecular Conformation; D010316:Particle Size; D012031:Refractometry; D013499:Surface Properties
chemical_list: D046911:Macromolecular Substances; D005857:Germanium; D006046:Gold