This study clarifies the influence of single-layer(TiN,HfN,W)and bi-layer(HfN/TiN,W/TiN)bottom electrodes(BEs)on the ferroelectric performance and reliability of the 10-nm-thick Hf_(0.5)Zr_(0.5)O_(2)(HZO)thin films.A ...This study clarifies the influence of single-layer(TiN,HfN,W)and bi-layer(HfN/TiN,W/TiN)bottom electrodes(BEs)on the ferroelectric performance and reliability of the 10-nm-thick Hf_(0.5)Zr_(0.5)O_(2)(HZO)thin films.A smaller thermal expansion coefficient in HfN or W imposes higher in-plane tensile stress on the HZO thin films,facilitating the polar orthorhombic(o-)phase fraction and enhancing remanent polarization(P_(r)).However,thicker interfacial layers formed when HfN or W single-layer BE and HZO contacted directly,leading to excessive leakage current and degraded ferroelectric performance.These excessive interfacial layers were effectively suppressed by inserting a thin(5 nm-20 nm)TiN layer on the HfN or W BEs.As a result,the HZO thin films on the HfN/TiN and W/TiN bi-layer BEs decrease the HZO grain size,facilitating the o-phase formation(increasing P_(r))and lowering the film's coercive field.However,the higher surface roughness of the W/TiN bi-layer BEs induced excessive leakage current and reliability degradation.In contrast,the HfN BEs with a 10-or 20-nm-thick upper TiN layer lower the surface roughness of the BEs,thereby eliminating the adverse effects.As a result,the HfN 40 nm/TiN 10 nm/HZO/TiN stack exhibited enhanced ferroelectric performance up to 10^(9)switching cycles with a lower cycling field of 2.7 MV/cm than the TiN 50 nm/HZO/TiN stack with a cycling field of 3.7 MV/cm.展开更多
Zr0.5Ti0.5O2(ZT) and Zr0.25Ti0.25Al0.5O2(ZTA) mixed oxides were prepared by co-precipitation method and characterized by low temperature adsorption-desorption,XRD and NH3-TPD. The activity of Pt/Zr0.5Ti0.5O2 and Pt/ Z...Zr0.5Ti0.5O2(ZT) and Zr0.25Ti0.25Al0.5O2(ZTA) mixed oxides were prepared by co-precipitation method and characterized by low temperature adsorption-desorption,XRD and NH3-TPD. The activity of Pt/Zr0.5Ti0.5O2 and Pt/ Zr0.5Ti0.5Al0.5O2 catalysts was evaluated using the simulated gases. The results show that ZTA samples exhibit higher specific surface area,larger pore volume and proper surface acidic amount and acidity in comparison with ZT. The results of the catalytic test indicate that Pt/ZT and Pt/ZTA catalysts exhibit excellent low-temperature catalytic activity and lower light-off temperatures of hydrocarbon,carbon monoxide and nitrogen oxides,especially better conversion for nitrogen oxides (NOx). The addition of Al2O3 into ZT enhanced the anti-aging property of Pt/ ZTA catalysts due to the excellent textural,structural,surface acidity and thermal stability.展开更多
A series of Ceo.sFeo.30Zr0.20O2 catalysts were prepared by different methods （co-precipitations method, citric acid sol-gel method, impregnation method, physical mixed method, and hydrotherrnal method） and character...A series of Ceo.sFeo.30Zr0.20O2 catalysts were prepared by different methods （co-precipitations method, citric acid sol-gel method, impregnation method, physical mixed method, and hydrotherrnal method） and characterized by X-ray diffraction （XRD）, Raman spectroscopy, Brunauer-Emmett-Teller （BET） and H2-TPR measurements. Potential of the catalysts in the soot oxidation was evaluated in a temperature-programmed oxidation （TPO） apparatus. The results showed that all the Fe3＋ and Zr4＋ were incor- porated into ceria lattice to form a pure Ce-Fe-Zr-O solid solution for the co-precipitation sample, but two kinds of Fe phases ex- isted in the Ce-Fe-Zr-O catalysts prepared by other methods： Fe3＋ incorporated into CeO2 lattice and dispersed Fe2O3 clusters. The free Fe2O3 clusters could improve the activity of catalysts for soot oxidation comparing with the pure Ce-Fe-Zr-O solid solution owing to the synergetic effect between free Fe2O3 and surface oxygen vacancies. In addition, the activity of catalysts strongly relied on the surface reducibility of free Fe2O3 particles. Holding both abundant free Fe2O3 particles and high oxygen vacancy concentration, the hydrothermal Ce0.5Fe0.3Zr0.202 catalyst presented the lowest Ti （251℃, ignition temperature of soot oxidation） and Tm （310 ℃, maximum oxidation rate temperature） for soot combustion （with tight-contact between soot and catalysts） among the five samples. Even after aging at 800 ℃ for 10 h, the Ti and Tm were still relatively low, at 273 and 361 ℃, respectively, indicating high catalytic stability.展开更多
Ce Zr O solid solution was prepared by four different methods, i.e., decomposition of nitrate, coprecipiation, hydroxysuainic acid sol gel as well as citrate sol gel, and characterized by using X ray powder diffr...Ce Zr O solid solution was prepared by four different methods, i.e., decomposition of nitrate, coprecipiation, hydroxysuainic acid sol gel as well as citrate sol gel, and characterized by using X ray powder diffraction, Raman and temperature programmed reduction. The phase composition and the reduction properties of Ce Zr O depend on the preparation method. A cubic Ce 0.5 Zr 0.5 O 2 solid solution can be obtained by using the sol gel method. The Ce Zr O solid solution prepared by using decomposition or coprecipiation was composed of cubic Ce 0.8 Zr 0.2 O 2 and tetragonal Ce 0.2 Zr 0.8 O 2 solid solution. The Ce Zr O solid solution prepared with different methods shows the different reduction properties owing to different phase composition. Results of differential thermal analysis and XRD show that Ce 0.5 Zr 0.5 O 2 solid solution is formed during the decomposition or combustion of the gel.展开更多
基金supported by the National Research Foundation of Korea(Grant No.2020R1A3B2079882).
文摘This study clarifies the influence of single-layer(TiN,HfN,W)and bi-layer(HfN/TiN,W/TiN)bottom electrodes(BEs)on the ferroelectric performance and reliability of the 10-nm-thick Hf_(0.5)Zr_(0.5)O_(2)(HZO)thin films.A smaller thermal expansion coefficient in HfN or W imposes higher in-plane tensile stress on the HZO thin films,facilitating the polar orthorhombic(o-)phase fraction and enhancing remanent polarization(P_(r)).However,thicker interfacial layers formed when HfN or W single-layer BE and HZO contacted directly,leading to excessive leakage current and degraded ferroelectric performance.These excessive interfacial layers were effectively suppressed by inserting a thin(5 nm-20 nm)TiN layer on the HfN or W BEs.As a result,the HZO thin films on the HfN/TiN and W/TiN bi-layer BEs decrease the HZO grain size,facilitating the o-phase formation(increasing P_(r))and lowering the film's coercive field.However,the higher surface roughness of the W/TiN bi-layer BEs induced excessive leakage current and reliability degradation.In contrast,the HfN BEs with a 10-or 20-nm-thick upper TiN layer lower the surface roughness of the BEs,thereby eliminating the adverse effects.As a result,the HfN 40 nm/TiN 10 nm/HZO/TiN stack exhibited enhanced ferroelectric performance up to 10^(9)switching cycles with a lower cycling field of 2.7 MV/cm than the TiN 50 nm/HZO/TiN stack with a cycling field of 3.7 MV/cm.
文摘Zr0.5Ti0.5O2(ZT) and Zr0.25Ti0.25Al0.5O2(ZTA) mixed oxides were prepared by co-precipitation method and characterized by low temperature adsorption-desorption,XRD and NH3-TPD. The activity of Pt/Zr0.5Ti0.5O2 and Pt/ Zr0.5Ti0.5Al0.5O2 catalysts was evaluated using the simulated gases. The results show that ZTA samples exhibit higher specific surface area,larger pore volume and proper surface acidic amount and acidity in comparison with ZT. The results of the catalytic test indicate that Pt/ZT and Pt/ZTA catalysts exhibit excellent low-temperature catalytic activity and lower light-off temperatures of hydrocarbon,carbon monoxide and nitrogen oxides,especially better conversion for nitrogen oxides (NOx). The addition of Al2O3 into ZT enhanced the anti-aging property of Pt/ ZTA catalysts due to the excellent textural,structural,surface acidity and thermal stability.
基金Project supported by National Natural Science Foundation of China(51374004,51204083,51174105,51104074)Natural Science Foundation of Yunnan Province(2010ZC018)
文摘A series of Ceo.sFeo.30Zr0.20O2 catalysts were prepared by different methods （co-precipitations method, citric acid sol-gel method, impregnation method, physical mixed method, and hydrotherrnal method） and characterized by X-ray diffraction （XRD）, Raman spectroscopy, Brunauer-Emmett-Teller （BET） and H2-TPR measurements. Potential of the catalysts in the soot oxidation was evaluated in a temperature-programmed oxidation （TPO） apparatus. The results showed that all the Fe3＋ and Zr4＋ were incor- porated into ceria lattice to form a pure Ce-Fe-Zr-O solid solution for the co-precipitation sample, but two kinds of Fe phases ex- isted in the Ce-Fe-Zr-O catalysts prepared by other methods： Fe3＋ incorporated into CeO2 lattice and dispersed Fe2O3 clusters. The free Fe2O3 clusters could improve the activity of catalysts for soot oxidation comparing with the pure Ce-Fe-Zr-O solid solution owing to the synergetic effect between free Fe2O3 and surface oxygen vacancies. In addition, the activity of catalysts strongly relied on the surface reducibility of free Fe2O3 particles. Holding both abundant free Fe2O3 particles and high oxygen vacancy concentration, the hydrothermal Ce0.5Fe0.3Zr0.202 catalyst presented the lowest Ti （251℃, ignition temperature of soot oxidation） and Tm （310 ℃, maximum oxidation rate temperature） for soot combustion （with tight-contact between soot and catalysts） among the five samples. Even after aging at 800 ℃ for 10 h, the Ti and Tm were still relatively low, at 273 and 361 ℃, respectively, indicating high catalytic stability.
文摘Ce Zr O solid solution was prepared by four different methods, i.e., decomposition of nitrate, coprecipiation, hydroxysuainic acid sol gel as well as citrate sol gel, and characterized by using X ray powder diffraction, Raman and temperature programmed reduction. The phase composition and the reduction properties of Ce Zr O depend on the preparation method. A cubic Ce 0.5 Zr 0.5 O 2 solid solution can be obtained by using the sol gel method. The Ce Zr O solid solution prepared by using decomposition or coprecipiation was composed of cubic Ce 0.8 Zr 0.2 O 2 and tetragonal Ce 0.2 Zr 0.8 O 2 solid solution. The Ce Zr O solid solution prepared with different methods shows the different reduction properties owing to different phase composition. Results of differential thermal analysis and XRD show that Ce 0.5 Zr 0.5 O 2 solid solution is formed during the decomposition or combustion of the gel.
