The etch characteristics of Si_1-xGex films in HNO3:H2O:HF were examined. The etch rate ratio (etch selectivity) between Si_1-xGex and Si escalated with the growth of HNO3 concentration at low concentration level, and...The etch characteristics of Si_1-xGex films in HNO3:H2O:HF were examined. The etch rate ratio (etch selectivity) between Si_1-xGex and Si escalated with the growth of HNO3 concentration at low concentration level, and when the HNO3 concentration exceeded a critical level the etch selectivity descended with higher HNO3 concentration. The dependence of etch selectivity on the HNO3 concentration was due to the higher critical HNO3 concentration for etching Si than that for etching Si1-xGex. Since the Ge-Ge bond energy was weaker than that of Si-Si and Si-Ge, the Ge atoms were oxidized preferentially once the HNO3 composition exceeded the critical concentration of etching Si1-xGex,which was manifested by the XPS spectra of Si1-xGex etched in HNO3:H2O:HF. When the HNO3 volume rose to another critical value, the significant growth of the Si etch rate low-ered the etch selectivity. Although both the etch rates of Si1-xGex and Si dropped with lower HF concentration, the etch rate ra-tio of Si1-xGex to Si boosted remarkably due to the water-soluble characteristics of GeO2.展开更多
Silver surfaces producing enhancement of the Raman scattering for adsorbed molecules have been simply prepared by etching them in HNO<sub>3</sub> solution. The dependence of the enhancement on etching time...Silver surfaces producing enhancement of the Raman scattering for adsorbed molecules have been simply prepared by etching them in HNO<sub>3</sub> solution. The dependence of the enhancement on etching time at different concentrations of the etching solution has also been investigated. When etched with 2.5 mol/L HNO<sub>3</sub> for 10-20 min, silver surfaces can all produce strong enhancement, and the surface-enhanced Raman scattering （SERS） activity can survive for more than 10 h in air. For Kr<sup>+</sup> laser excitation at 647.1 nm, the observed展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 61006088)the National Basic Research Program of China (973 Program) (Grant No. 2010CB832906)the Natural Sci-ence Foundation of Shanghai (Grant No. 10ZR1436100)
文摘The etch characteristics of Si_1-xGex films in HNO3:H2O:HF were examined. The etch rate ratio (etch selectivity) between Si_1-xGex and Si escalated with the growth of HNO3 concentration at low concentration level, and when the HNO3 concentration exceeded a critical level the etch selectivity descended with higher HNO3 concentration. The dependence of etch selectivity on the HNO3 concentration was due to the higher critical HNO3 concentration for etching Si than that for etching Si1-xGex. Since the Ge-Ge bond energy was weaker than that of Si-Si and Si-Ge, the Ge atoms were oxidized preferentially once the HNO3 composition exceeded the critical concentration of etching Si1-xGex,which was manifested by the XPS spectra of Si1-xGex etched in HNO3:H2O:HF. When the HNO3 volume rose to another critical value, the significant growth of the Si etch rate low-ered the etch selectivity. Although both the etch rates of Si1-xGex and Si dropped with lower HF concentration, the etch rate ra-tio of Si1-xGex to Si boosted remarkably due to the water-soluble characteristics of GeO2.
文摘Silver surfaces producing enhancement of the Raman scattering for adsorbed molecules have been simply prepared by etching them in HNO<sub>3</sub> solution. The dependence of the enhancement on etching time at different concentrations of the etching solution has also been investigated. When etched with 2.5 mol/L HNO<sub>3</sub> for 10-20 min, silver surfaces can all produce strong enhancement, and the surface-enhanced Raman scattering （SERS） activity can survive for more than 10 h in air. For Kr<sup>+</sup> laser excitation at 647.1 nm, the observed
