Cathodic plasma electrolytic (CPE) techniques are new groups of coating processes, which can be used for fabrication of nanostructured layers on surface of a wide range of metallic substrates. The most exciting visible feature of these atmospheric-based plasma techniques is continuous sparking on processed surface inside an electrolyte. Unlike the anodic part of plasma electrolysis (usually known as plasma electrolytic oxidation (PEO) or micro arc oxidation (MAO)), which is commonly used for oxidation of light metals/alloys such as aluminum, titanium and magnesium, CPE techniques can clean and coat different metals and alloys such as steel, copper, and light metals/alloys with formation of wide range of nanostructures including complex carbides, carbonitrides, intermetallics, and even oxides. It has been observed that the properties of obtained layers depend on the characteristics of achieved nanostructures such as average size, distribution and average coordination number of nanocrystallites. Furthermore...

Nano-Fabrication by Cathodic Plasma Electrolysis

Modification of the surface state and doping of CdTe and CdZnTe crystals by pulsed laser irradiation

In this work we study the mechanisms of laser radiation interaction with elementary semiconductors such as Si and Ge and their solid solution SiGe. As a result of this investigation, the mechanisms of nanocones and microcones formation on a surface of semiconductor were proposed. We have shown the possibility to control the size and the shape of cones both by the laser. The main reason for the formation of nanocones is the mechanical compressive stresses due to the atoms’ redistribution caused by the gradient of temperature induced by strongly absorbed laser radiation. According to our investigation, the nanocone formation mechanism in semiconductors is characterized by two stages. The first stage is characterized by formation of a p-n junction for elementary semiconductors or of a Ge/Si heterojunction for SiGe solid solution. The generation and redistribution of intrinsic point defects in elementary semiconductors and Ge atoms concentration on the irradiated surface of SiGe solid solution in temperature gradient field take place at this stage due to the thermogradient effect which is caused by strongly absorbed laser radiation. The second stage is characterized by formation of nanocones due to mechanical plastic deformation of the compressed Ge layer on Si. Moreover, a new 1D-graded band gap structure in elementary semiconductors due to quantum confinement effect was formed. For the formation of microcones Ni/Si structure was used. The mechanism of the formation of microcones is characterized by two stages as well. The first stage is the melting of Ni film after irradiation by laser beam and formation of Ni islands due to surface tension force. The second step is the melting of Ni and subsequent manifestations of Marangoni effect with the growth of microcones.

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Formation mechanisms of nano and microcones by laser radiation on surfaces of Si, Ge, and SiGe crystals

Formation Mechanisms of Nano and Microcones by Laser Radiation on Surfaces of Si, Ge, and SiGe Crystals

Laser-induced increase of resistivity and improvement of optical properties of CdZnTe crystal

Self-organizing structures of nanometer size are observed on the surface of CdZnTe crystal irradiated by strongly absorbed Nd:YAG laser radiation (LR) at intensities within 4–12 MW/cm2. The effect of exciton quantum confinement manifested by a shift to higher energies of the A0,X exciton band of the photo-luminescent spectrum is present in structures of 10–15 nm in diameter at the top of nano-hills. A graded band gap structure with optical window is formed at the top of nano-hills. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Exciton quantum confinement effect in nanostructures formed by laser radiation on the surface of CdZnTe ternary compound

Excitation Quantum Confinement Effect in Nanostructures Formed by Laser Radiation on the Surface of CdZnTe Ternary Compound

Self-organizing structures of nanometer size are observed on the surface of CdZnTe crystal irradiated by strongly absorbed Nd:YAG laser radiation (LR) at intensities within 4–12 MW/cm 2 . The effect of exciton quantum confinement manifested by a shift to higher energies of the A 0 ,X exciton band of the photoluminescent spectrum is present in structures of 10–15 nm diameter at the top of nano-hills. A graded band gap structure with optical window is formed at the top of nano-hills.

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O. Strilchyk

Papers

Exciton quantum confinement effect in nanostructures formed by laser radiation on the surface of CdZnTe ternary compound

Excitation Quantum Confinement Effect in Nanostructures Formed by Laser Radiation on the Surface of CdZnTe Ternary Compound

Optical properties of nanostructure formed on a surface of CdZnTe crystal by laser radiation