Semiconductor materials became a part of nowadays life due to useful applications caused by characteristic properties as variable conductivity and sensitivity to light or heat. Electrical properties of a semiconductor can be modified by doping or by the application of electric fields or light; and from this view, devices made from semiconductors can be used for amplification or energy conversion. The compound semiconductor materials from III-V class experienced a qualitative leap from promising potential to nowadays technologic environment. The III-V semiconductor compounds are the material bases for electronic and optoelectronic devices such as high-electron-mobility transistors (HEMT), bipolar heterostructure transistors, IR light-emitting diodes, heterostructure lasers, Gunn diodes, Schottky devices, photodetectors, and heterostructure solar cells for terrestrial and spatial operating conditions. Among III-V semiconductor compounds, gallium arsenide (GaAs) and gallium antimonide (GaSb) are of special interest as a substrate material due to the lattice parameter match to solid solutions (ternary and quaternary) whose band gaps cover a wide spectral range from 0.8 to 4.3 μm in the case of GaSb. The solid/solid interfaces could play a key part in the development of microelectronic device technology. In most of the cases, the initial surface of III-V compounds exposed to laboratory conditions is covered usually with native oxide layers. Various techniques for performing the surface cleaning process are used, e.g., controlled chemical etching, in situ ion sputtering, coupled with controlled annealing in vacuum and often these classic techniques are combined in order to prepare an eligible semiconductor surface to be exposed to a technological device chain. The evolution of surface native oxides in different cleaning procedures and the characteristics of as-prepared semiconductor surface were investigated by modern surface investigation techniques, i.e., X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), Rutherford backscattering spectrometry (RBS) combined with electrical characterization. Surface preparation of semiconductors in particular for III-V compounds is a necessary requirement in device technology due to the existence of surface impurities and the presence of native oxides. The impurities can affect the adherence of ohmic and Schottky contacts and due to thermal decomposition of native oxides (e.g., GaSb) it also affect the interface metal/semiconductor. The practical experience reveals that the simple preparation of a surface is a nonrealistic expectation, i.e., surface preparation is a result of combined treatments, namely chemical etching and thermal treatment, ion beam sputtering and thermal reconstruction procedure.
Part of the book: Nanoscaled Films and Layers
Post-modern society is viewed nowadays as a technologized society, where the great solutions to human problems can be solved by the progress of technology in economics from classical industry to communications. In the last years, nanotechnology is called to play an important part in the global food production, food security and food safety in the sense that the use of nanoscale micronutrients conduced to suppressing crop disease and the relationship between nutritional status and plant diseases is investigated. Nanomaterials are capable to penetrate into cells of herbs; they can carry DNA and other chemical compounds in the cells extending the possibility in plant biotechnology to target special gene manipulation. It is important to note that the concentration, plant organ or tissue, exposure rate, elemental form, plant species, and exposure dosage (chronic/acute) affect the plant response and in particular the distinct stress response. The complex process of utilization nanoparticles in agriculture has to be monitored to a level that avoids further environmental contamination. The present and future use of nanoparticles as micronutrients is affected by different risks related to nanotoxicity of micronutrients, a problem to be solved by an appropriate and safe circuit of nanoparticles in soil, water, plants and at last in human organism.
Part of the book: Urban Horticulture