[Show abstract][Hide abstract] ABSTRACT: This work is devoted to deposition of alumina–silica films using an innovative pulsed injection metal organic chemical vapour deposition technique and aluminium tri(iso-propoxide) (Al(i-OPr)3) and tetraethoxysilane (TEOS) as precursors. The deposited aluminium silicate films have been characterised by scanning electron microscopy, infrared spectroscopy, X-ray diffractometry and capacitance–voltage (C–V) measurements. The investigation of the deposition at different Si/Al ratios and substrate temperatures has shown that the growth rate increases with the increase of Al(i-OPr)3 proportion in solution and decreases as the proportion of TEOS increases. We have also shown that aluminium content in the film increases at lower deposition temperatures while silicon content increases at higher temperatures. The permittivity of the films determined from C–V measurements decreases with increasing substrate temperature. It was found that films deposited at substrate temperatures of 600 or 700 °C and with the highest Si/Al ratio have the lowest dielectric permittivity. This research should be useful for further development of MOCVD technology for the deposition of aluminosilicate-based dielectric materials with controlled dielectric permittivity.
Thin Solid Films 12/2006; 515(4):1830–1834. DOI:10.1016/j.tsf.2006.07.007 · 1.76 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The co-precipitation of magnetite nanoparticles in the presence of hydroxyl-functionalized porous silicon samples helps in forming the self-organization of magnetite nanoparticles into dendrite or fractal structures yielding new magnetic composites. The fractal patterned porous silicon sample with a hydroxyl terminated surface was used as a substrate for the deposition of magnetic Fr3O4 nanoparticles. This process was performed by the co-precipitation of magnetic particles from the solution of iron (Fe 3+/Fe2+)salts in the stoichiometric ratio (Fe 3+/Fe2+=2) using aqueous ammonia in the presence of the porous silicon substrate. The mechanism of fractal formation involves a DLA growth model influenced by porous-substrate effect. These new magnetic silicon composites may be used as potential applications in biotechnology as biomagnetic implants in medicine and substrate in cell biology.
Small 08/2006; 2(7):864-9. DOI:10.1002/smll.200500521 · 8.37 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The discovery of room temperature photoluminescence in porous silicon has opened up a range of applications for this material in new areas such as optical, photodetector, photovoltaic, micromachine and sensors. For this reason there have been significant efforts in recent years directed at modification of silicon surfaces via formation of Si-C and Si-O-E (E = H, C, N) bonds on the silicon surfaces. However, research on bonding of metallorganic fragments to the silicon surface is scant. The main objectives of our work are to develop and investigate new ways of specific chemical bonding of selected metallorganic compounds to the Si surface and to prepare new types of silicon-based materials.New metallorganic composites have been developed on macro- and micro- porous silicon surfaces. The silicon surfaces have been effectively modified using inorganic and organometallic chemistry approaches. The work includes: (i) preparation and investigation of Cl-, HO-, and Cp- modified porous Si-surfaces; (ii) preparation and characterisation of iron oxide layers on porous silicon; (iii) characterisation of metallorganic layers on porous silicon by FTIR, EDX and Scanning Electronic Microscopy (SEM). There are strong possibilities that those composite materials will have a wide range of applications in nano-technology and optoelectronics.