Nanostructurale nature of the porous GaAs layer formed on p+-GaAs substrate by electrochemical anodization
A porous GaAs layer has been formed by electrochemical anodization in HF based solution on extremely doped p-type GaAs substrate. Porous nature of the elaborated sample has been evidenced by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Nanostructurale nature of the porous layer has been demonstrated by X-ray diffraction analysis (XRD) and confirmed by photoluminescence spectroscopy (PL).
Investigation of porous GaAs layers formed on n+‐type GaAs by electrochemical anodization in HF solution
The electrochemical etching of n+‐type GaAs in a hydrofluoric acid (HF) solution results in the formation of a porous layer. The current–potential characteristic I(V) of the n+‐type GaAs–HF electrolyte interface shows that pore formation started at a breakdown anodic potential of about 2.5 V independent of the HF concentration. In addition, it is also shown that an electropolishing of the semiconductor started over a critical anodic potential value. The morphology and photoluminescence (PL) of the porous samples were investigated. It has been shown that the porous layer surface morphology consists of arbitrarily shaped crystallites, the pores grow deeply in the substrate and, under some electrochemical conditions, etch pits can be formed. The porous layers exhibited an intense and broad PL band, compared to that of the starting GaAs, composed of elementary bands located below and above the band gap of the starting GaAs. The elementary bands located above the band gap were attributed to GaAs nanocrystals. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental Study on Acoustic Agglomeration of Fine Particles from Coal Combustion
The removal of fine particles in coal-fired fumes was experimentally studied based on acoustic agglomeration. An experiment facility was designed and set up. In this facility, a fluidized bed coal combustor was used as fume generator, and an Electrical Low Pressure Impact or (ELPI) was used to measure the fine particle concentration and size distribution in the fumes. The results show that under the effect of high intensity sound waves, there is good performance to remove fine particles in coal-fired fumes, which with a number mean diameter of 0.07μm. Especially, under the conditions of the frequency of 1 000Hz and the sound intensity of 161.5dB, the number concentration of 0.0233~9.314μm particles decreased by 85.2%, and their mass concentration decreased by 92.5%.