Papers by Keyword: Si(100)

Abstract: A complex ZnO/ZnAl₂O₄ heterostructures thin films on glass and Si (111) substrates have been successively obtained by a soft ultrasonic spray pyrolysis (USP) method deposition using the Zn/Al molar ratios concentrations of 0.07/0.13 and 0.1/0.1, respectively. According to (XRD) an ordered zinc oxide (ZnO) and zinc aluminate (ZnAl₂O₄) structures deposited onto glass from the air annealing at 500 °C during 2 hours was observed and confirmed by the (EDX), (FTIR) and Raman spectroscopy techniques. The estimated crystallites size and stress values of ZnO and ZnAl₂O₄ in the ZnO/ZnAl₂O₄/glass film were 19 nm/0.469 GPa and 11 nm/-0.292 GPa, respectively. The lower Zn/Al molar ratio around 0.035/0.06 produced only ZnO as a single phase, suggesting the Al insufficient quantity. The Si (100) substrate with 0.07 Zn molarity conducted to the Zn₂SiO₄/ZnO/ZnAl₂O₄ composite. The Raman integrated intensity bands of ZnO and ZnAl₂O₄ increases with increasing Zn to Al molar ratio (0.1/0.1 comparatively to 0.07/0.13). The ZnO&ZnAl₂O₄ crystallinity enhances as Zn molarity increases. The ZnO films in the composites grow with (002) texture. The TC(hkl) value indicated that ZnAl₂O₄ in the ZnO/ZnAl₂O₄/glass layer is polycrystalline preferentially oriented along the (311) plane. Spinel ZnAl₂O₄ oxide onto Si (111) substrate grown according to the (220) orientation. Crystallites are larger in ZnO/ZnAl₂O₄/Si than in ZnO/ZnAl₂O₄/glass. The ZnO/ZnAl₂O₄ film onto glass substrate is transparent in the visible and near infrared regions and sensitive to UV absorption, as characterized by UV-Vis spectroscopy. The ZnO and ZnAl₂O₄ E_g values in the ZnO/ZnAl₂O₄/glass composite were 3.25 and 3.88 eV, respectively.

Abstract: Covalently tethered well-defined new three-arm star hydrophilic poly(ethylene glycol) monomethacrylate (PEGMA) brushed nanoparticles on silicon surface have been successfully prepared by (i) synthesis a novel type of three-arm star-shaped preceding initiator, trifunctional hydroxy-based N-allyl-3,4,5-trihydroxybenzamide (NATHB), (ii) UV-induced hydrosilylation of NATHB with the hydrogen-termined Si(100) (Si-NATHB surface), (iii) coupling of 2-bromo isobutyrl bromide with the hydroxyl of NATHB by the esterification to provide the initiators (Si–NATHB–R3Br) for the subsequent ATRP, (iv) surface-initiated ATRP of PEGMA and 2-hydroxyethl methacrylate monomethacrylate (HEMA) to give the linear Si–NATHB–g–P(PEGMA) brushes and the Si–NATHB–g–P(HEMA) surface, (v) further coupling of 2-bromo isobutyrl bromide with the hydroxyl of P(HEMA) by the esterification to produce the macroinitiators (Si–NATHB–g–P(HEMA)-R3Br) and (vi) surface-initiated ATRP of PEGMA to give the comb-shaped Si–NATHB–g–P(HEMA)–g–P(PEGMA) brushes surface. Kinetics study indicated that the chain growth of P(PEGMA) and P(HEMA) from the functionalized silicon surfaces was consistent with a “controlled” or “living” process. The chemical composition and functionality of the silicon surface were tailored by the well-defined star linear and comb-shaped P(PEGMA) brushes, which provide with this type of surface structures formed in three brushes under conditions of spatial constraints imposed by their chemical connection to a single grafting site. XPS spectra testify that the linear and comb-shaped P(PEGMA) have been grafted on the Si-NATHB surface. AFM imaging of the hydrophilic polymer brushed nanoparticles imaged distinctive morphology when they were prepared into linear and comb-shaped brushes structure.