Sharp interfaces in optoelectronic devices are key for proper band alignment. Despite its benefits as buffer layer, ZnS deposited via atomic layer deposition(ALD) renders intermixed interfaces to its substrate, which ...Sharp interfaces in optoelectronic devices are key for proper band alignment. Despite its benefits as buffer layer, ZnS deposited via atomic layer deposition(ALD) renders intermixed interfaces to its substrate, which can be detrimental for device performance. Here, we are attempting to elucidate the chemical species deriving from this metal-oxide to metal-sulfide transition studying ultrathin film ZnS on SiO_2 using high resolution X-ray photoluminescence spectroscopy(XPS).Regarding the S 2p spectra after a deposition of only three cycles of ZnS, we discover the many different chemical species in which S is present. These include intermediate oxides such as SO_4^(2-).These species become more obvious as we tilt the sample in the XPS chamber to shallower angles.Comparing the Si 2p and S 2p high resolution peaks in the depth profile, one can clearly uncover the confinement of SO_4^(2-) to the interface of the underlying substrate. This may indicate that SiO_2/ZnS interfaces contain interfacial sulphates that likely alter the electronic configuration of this interface.展开更多
Magnesium alloys have been widely studied as materials for temporary implants,but their use has been limited by their corrosion rate.Recently,coatings have been proven to provide an effective barrier.Though only littl...Magnesium alloys have been widely studied as materials for temporary implants,but their use has been limited by their corrosion rate.Recently,coatings have been proven to provide an effective barrier.Though only little explored in the field,Atomic Layer Deposition(ALD)stands out as a coating technology due to the outstanding film conformality and density achievable.Here,we provide first insights into the corrosion behavior and the induced biological response of 100 nm thick ALD TiO_(2),HfO_(2)and ZrO_(2)coatings on AZ31 alloy by means of potentiodynamic polarization curves,electrochemical impedance spectroscopy(EIS),hydrogen evolution and MTS colorimetric assay with L929 cells.All three coatings improve the corrosion behavior and cytotoxicity of the alloy.Particularly,HfO_(2)coatings were characterized by the highest corrosion resistance and cell viability,slightly higher than those of ZrO_(2)coatings.TiO_(2)was characterized by the lowest corrosion improvements and,though generally considered a biocompatible coating,was found to not meet the demands for cellular applications(it was characterized by grade 3 cytotoxicity after 5 days of culture).These results reveal a strong link between biocompatibility and corrosion resistance and entail the need of taking the latter into consideration in the choice of a biocompatible coating to protect degradable Mg-based alloys.展开更多
基金support from Center on Nanostructuring for Efficient Energy Conversion(CNEEC)at Stanford University,an Energy Frontier Research Center funded by the U.S.Department of Energy,Office of Science,Office of Basic Energy Sciences under Award Number DESC0001060 the Austrian Research Fund(FWF)under the contract J3505-N20
文摘Sharp interfaces in optoelectronic devices are key for proper band alignment. Despite its benefits as buffer layer, ZnS deposited via atomic layer deposition(ALD) renders intermixed interfaces to its substrate, which can be detrimental for device performance. Here, we are attempting to elucidate the chemical species deriving from this metal-oxide to metal-sulfide transition studying ultrathin film ZnS on SiO_2 using high resolution X-ray photoluminescence spectroscopy(XPS).Regarding the S 2p spectra after a deposition of only three cycles of ZnS, we discover the many different chemical species in which S is present. These include intermediate oxides such as SO_4^(2-).These species become more obvious as we tilt the sample in the XPS chamber to shallower angles.Comparing the Si 2p and S 2p high resolution peaks in the depth profile, one can clearly uncover the confinement of SO_4^(2-) to the interface of the underlying substrate. This may indicate that SiO_2/ZnS interfaces contain interfacial sulphates that likely alter the electronic configuration of this interface.
文摘Magnesium alloys have been widely studied as materials for temporary implants,but their use has been limited by their corrosion rate.Recently,coatings have been proven to provide an effective barrier.Though only little explored in the field,Atomic Layer Deposition(ALD)stands out as a coating technology due to the outstanding film conformality and density achievable.Here,we provide first insights into the corrosion behavior and the induced biological response of 100 nm thick ALD TiO_(2),HfO_(2)and ZrO_(2)coatings on AZ31 alloy by means of potentiodynamic polarization curves,electrochemical impedance spectroscopy(EIS),hydrogen evolution and MTS colorimetric assay with L929 cells.All three coatings improve the corrosion behavior and cytotoxicity of the alloy.Particularly,HfO_(2)coatings were characterized by the highest corrosion resistance and cell viability,slightly higher than those of ZrO_(2)coatings.TiO_(2)was characterized by the lowest corrosion improvements and,though generally considered a biocompatible coating,was found to not meet the demands for cellular applications(it was characterized by grade 3 cytotoxicity after 5 days of culture).These results reveal a strong link between biocompatibility and corrosion resistance and entail the need of taking the latter into consideration in the choice of a biocompatible coating to protect degradable Mg-based alloys.
