Papers by Keyword: Si(111)

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: Bulk β-PdBi₂ layered material is known as a low-temperature superconductor. Recently, ultrathin films of this material consisting of dozens of triple layers were grown by molecular beam epitaxy and demonstrated structural, electronic and superconducting properties similar to those of bulk crystals. In this paper, we showed that thin film of β-PdBi₂ can be grown by alternative palladium and bismuth deposition and its electrical conductance was investigated at room temperature in comparison with the conductivity of bulk β - PdBi₂.

Abstract: The influence of step and domain boundary on growth of Si(111)-√ 3×√3-Ag has been studied in situ using optical surface second-harmonic generation and low energy electron diffraction. The second harmonic intensity shows a difference of about 50% for Si(111) surfaces with different miscut angles and domain boundary densities, although no significant difference has been observed in low energy electron diffraction patterns, indicating a significant impediment to the growth of Si(111)-√ 3×√3-Ag by step and domain boundaries. Simulation results reveal a 90% coverage of Si(111)-√ 3×√3-Ag on the vicinal substrate with an miscut angle of 0.41o, consistent with the dynamics of Ag atoms on Si(111)-7×7 surface. The influence of two dimentional adatom gas on surface structure has also been discussed.

Abstract: This paper presents the structural and optical studies of porous GaN sample compared to the corresponding as grown GaN. The samples were investigated by scanning electron microscopy (SEM), high resolution x-ray diffraction (HRXRD), and photoluminescence (PL). The porous area is very uniform, with pore diameter in the range of 80-110 nm. XRD measurements showed that the (0002) diffraction plane peak width of porous samples was slightly broader than the as-grown sample. PL measurements revealed that the near band edge peak of the porous samples were redshifted. Metal-semiconductor-metal (MSM) photodiode was fabricated on the samples. For as grown GaN sample, this detector shows a sharp cut-off wavelength at 362 nm. A maximum responsivity of 0.258 A/W was achieved at 360 nm. For the porous GaN sample, this detector shows a sharp cut-off wavelength at 364 nm. A maximum responsivity of 0.771 A/W was achieved at 363 nm.