Ferroelectric(FE)thin films have recently attracted renewed interest in research due to their great potential for designing novel tunable electromagnetic devices such as large intelligent surfaces(LISs).However,the me...Ferroelectric(FE)thin films have recently attracted renewed interest in research due to their great potential for designing novel tunable electromagnetic devices such as large intelligent surfaces(LISs).However,the mechanism of how a polar structure in the FE thin films contributes to desired tunable performance,especially within the microwave frequency range,which is the most widely used frequency range of electromagnetics,has not been illustrated clearly.In this paper,we described several straightforward and cost-effective methods to fabricate and characterize Ba_(0.6)Sr_(0.4)TiO_(3)(BST)thin films at microwave frequencies.The prepared BST thin films here exhibit homogenous structures and great tunability(h)in a wide frequency and temperature range when the applied field is in the out-of-plane direction.The high tunability can be attributed to high concentration of polar nanoclusters.Their response to the applied direct current(DC)field was directly visualized using a novel non-destructive near-field scanning microwave microscopy(NSMM)technique.Our results have provided some intriguing insights into the application of the FE thin films for future programmable high-frequency devices and systems.展开更多
The passivation behavior of Fe in the acidic AlCl_3-1-ethyl-3-methyl-imidazolium chloride(AlCl_3-EMIC) ionic liquid was studied by linear sweep voltammetry and chonopotentiometry. Various approaches were used to chara...The passivation behavior of Fe in the acidic AlCl_3-1-ethyl-3-methyl-imidazolium chloride(AlCl_3-EMIC) ionic liquid was studied by linear sweep voltammetry and chonopotentiometry. Various approaches were used to characterize the composition and morphology of passive film formed on the Fe electrode, such as scanning electron microscopy(SEM), Raman spectra and X-ray Photoelectron Spectroscopy(XPS). The results showed that the critical passivation potential of Fe shifted to more negative when the molar ratio of AlCl_3:EMIC changing from 2 to 1.3.A film with a light yellow color was observed on the surface of the Fe electrode after passivation. The composition of the passive film was demonstrated to be FeCl_2. The passive film was composed of particulate FeCl_2 with average diameter of about 500 nm. The formation of FeCl_2 film was attributed to the variation of the electrolyte Lewis acidity from acidic to neutral at the interface during the dissolution process of Fe. The reason caused the variation of the electrolyte acidity was discussed.展开更多
A Fe-Ni soft magnetic film was prepared in sulphate solution by electroplating.The influences of the molar ratio of n[Fe^(2+)]/n[Ni^(2+)],current density,bath temperature,pH and L-ascorbic acid concentration on magnet...A Fe-Ni soft magnetic film was prepared in sulphate solution by electroplating.The influences of the molar ratio of n[Fe^(2+)]/n[Ni^(2+)],current density,bath temperature,pH and L-ascorbic acid concentration on magnetic properties of Fe-Ni alloy film were investigated.The results show that the saturated flux density(BS)of the film increases initially and decreases after it reaches the specific value with the increase of n[Fe^(2+)]/n[Ni^(2+)]molar ratio,current density,bath temperature and pH.However,the relationship between L-ascorbic acid concentration and BS keeps linear.It is observed that the coercive force(H_(c))is enhanced with the increase of n[Fe^(2+)]/n[Ni^(2+)]molar ratio,current density and pH.By comparison,when the bath temperature increases,Hc always decreases.With the increase of L-ascorbic acid concentration,the coercive force increases initially and then decreases.展开更多
To explore and study the Fe-A1 system alloy presenting exceptional oxidation resistance at high temperature, the Fe-36Al-0.09C-0.09B-0.04Zr alloy was designed and developed. The microstructure and hardness of the back...To explore and study the Fe-A1 system alloy presenting exceptional oxidation resistance at high temperature, the Fe-36Al-0.09C-0.09B-0.04Zr alloy was designed and developed. The microstructure and hardness of the backing at 1250℃were analyzed and measured. Thermodynamics and kinetics of the oxidation behavior were also analyzed by X-ray diffraction, scanning electron micros- copy, and energy-dispersive X-ray spectroscopy techniques. The results show that the microstructttre of the Fe-36Al-0.09C-0.09B-0.04Zr alloy is FeAl phase at ambient temperature and is stable at 1250℃. It displays the excellent property of oxidation resistance because the oxide film has only the Al2O3 layer, and its oxidation kinetics curve obeys the parabolic law at 1250℃. The oxidation mechanism at 1250℃ is presumed that in the early oxidation period, the alloy oxidizes to form a large number of Al2O3 and a little Fe2O3, then, the enrichment of Al caused by Fe oxidization combines with O to form Al2O3.展开更多
The positron annihilation lifetimes and the Doppler broadening by slow positron beam are measured in thin Fe films with thickness 500 nm, a thin Hf film with thickness 100 nm, and the bilayer Fe (50 nm)/Hf (50 nm) on ...The positron annihilation lifetimes and the Doppler broadening by slow positron beam are measured in thin Fe films with thickness 500 nm, a thin Hf film with thickness 100 nm, and the bilayer Fe (50 nm)/Hf (50 nm) on quartz glass substrate. We have analyzed the behavior in vacancy-type defects in each layer through some deposition temperatures and annealing. It is observed that the thin Fe film, the thin Hf film, and the bilayer Fe (50 nm)/Hf (50 nm) already contain many vacancy-type defects. We have investigated the change of densities of the vacancy-carbon complex and the small vacancy-cluster with carbons, through solid-state amorphization of Fe (50 nm)/Hf (50 nm) bilayer.展开更多
Thin films of iron(Fe)-doped titanium dioxide(Fe:TiO_(2))T were prepared by sol–gel spin coating technique and further calcined at 450℃.The structural and optical properties of Fe-doped TiO_(2) thin films were inves...Thin films of iron(Fe)-doped titanium dioxide(Fe:TiO_(2))T were prepared by sol–gel spin coating technique and further calcined at 450℃.The structural and optical properties of Fe-doped TiO_(2) thin films were investigated by X-ray diffraction(XRD),scanning electron microscopy(SEM),ultraviolet–visible spectroscopy(UV–vis)and atomic force microscopic(AFM)techniques.The XRD results confirm the nanostructured TiO_(2) thin films having crystalline nature with anatase phase.The characterization results show that the calcined thin films having high crystallinity and the effect of iron substitution lead to decreased crystallinity.The SEM investigations of Fe-doped TiO_(2) films also gave evidence that the films were continuous spherical shaped particles with a nanometric range of grain size and film was porous in nature.AFM analysis establishes that the uniformity of the TiO_(2) thin film with average roughness values.The optical measurements show that the films having high transparency in the visible region and the optical band gap energy of Fe-doped TiO_(2) film with iron(Fe)decrease with increase in iron content.These important requirements for the Fe:TiO_(2) films are to be used as window layers in solar cells.展开更多
The room temperature stability and crystallization of amorphous Nd_xFe_(1-x)thin films with x=0.06—0.90,prepared by flash evaporation at 77 K,were investigated by X-ray diffraction and TEM observation.The amorphous N...The room temperature stability and crystallization of amorphous Nd_xFe_(1-x)thin films with x=0.06—0.90,prepared by flash evaporation at 77 K,were investigated by X-ray diffraction and TEM observation.The amorphous Nd_xFe_(1-x)films are stable at room temperature when 0.19<x<0.50.Crystallized phases grow along the surface of film as very thin flakes and become thick only at relatively high temperatures.After complete crystallization,the Nd_xFe_(1-x)films with x<0.50 are composed of Nd_2Fe-(17)and metal Nd,but no NdFe2,a phase expected to occur by phase diagram.展开更多
基金This work was supported by the“Software Defined Materials for Dynamic Control of Electromagnetic Waves”(ANIMATE)Project(QinetiQ IRAD Grant No.41025673 and EPSRC Grant No.EP/R035393/1),and the authors acknowledge QinetiQ and Engineering and Physical Sciences Research Council(EPSRC).Hanchi Ruan acknowledges EPSRC for funding the Ph.D.studentship.
文摘Ferroelectric(FE)thin films have recently attracted renewed interest in research due to their great potential for designing novel tunable electromagnetic devices such as large intelligent surfaces(LISs).However,the mechanism of how a polar structure in the FE thin films contributes to desired tunable performance,especially within the microwave frequency range,which is the most widely used frequency range of electromagnetics,has not been illustrated clearly.In this paper,we described several straightforward and cost-effective methods to fabricate and characterize Ba_(0.6)Sr_(0.4)TiO_(3)(BST)thin films at microwave frequencies.The prepared BST thin films here exhibit homogenous structures and great tunability(h)in a wide frequency and temperature range when the applied field is in the out-of-plane direction.The high tunability can be attributed to high concentration of polar nanoclusters.Their response to the applied direct current(DC)field was directly visualized using a novel non-destructive near-field scanning microwave microscopy(NSMM)technique.Our results have provided some intriguing insights into the application of the FE thin films for future programmable high-frequency devices and systems.
基金the National Natural Science Foundation of China(No.51271166)
文摘The passivation behavior of Fe in the acidic AlCl_3-1-ethyl-3-methyl-imidazolium chloride(AlCl_3-EMIC) ionic liquid was studied by linear sweep voltammetry and chonopotentiometry. Various approaches were used to characterize the composition and morphology of passive film formed on the Fe electrode, such as scanning electron microscopy(SEM), Raman spectra and X-ray Photoelectron Spectroscopy(XPS). The results showed that the critical passivation potential of Fe shifted to more negative when the molar ratio of AlCl_3:EMIC changing from 2 to 1.3.A film with a light yellow color was observed on the surface of the Fe electrode after passivation. The composition of the passive film was demonstrated to be FeCl_2. The passive film was composed of particulate FeCl_2 with average diameter of about 500 nm. The formation of FeCl_2 film was attributed to the variation of the electrolyte Lewis acidity from acidic to neutral at the interface during the dissolution process of Fe. The reason caused the variation of the electrolyte acidity was discussed.
基金This work was financially supported by the National High-Tech Research and Development Program(No.2003AA302510)the Beijing Municipal Science and Technology Program(No.D0405003040121).
文摘A Fe-Ni soft magnetic film was prepared in sulphate solution by electroplating.The influences of the molar ratio of n[Fe^(2+)]/n[Ni^(2+)],current density,bath temperature,pH and L-ascorbic acid concentration on magnetic properties of Fe-Ni alloy film were investigated.The results show that the saturated flux density(BS)of the film increases initially and decreases after it reaches the specific value with the increase of n[Fe^(2+)]/n[Ni^(2+)]molar ratio,current density,bath temperature and pH.However,the relationship between L-ascorbic acid concentration and BS keeps linear.It is observed that the coercive force(H_(c))is enhanced with the increase of n[Fe^(2+)]/n[Ni^(2+)]molar ratio,current density and pH.By comparison,when the bath temperature increases,Hc always decreases.With the increase of L-ascorbic acid concentration,the coercive force increases initially and then decreases.
文摘To explore and study the Fe-A1 system alloy presenting exceptional oxidation resistance at high temperature, the Fe-36Al-0.09C-0.09B-0.04Zr alloy was designed and developed. The microstructure and hardness of the backing at 1250℃were analyzed and measured. Thermodynamics and kinetics of the oxidation behavior were also analyzed by X-ray diffraction, scanning electron micros- copy, and energy-dispersive X-ray spectroscopy techniques. The results show that the microstructttre of the Fe-36Al-0.09C-0.09B-0.04Zr alloy is FeAl phase at ambient temperature and is stable at 1250℃. It displays the excellent property of oxidation resistance because the oxide film has only the Al2O3 layer, and its oxidation kinetics curve obeys the parabolic law at 1250℃. The oxidation mechanism at 1250℃ is presumed that in the early oxidation period, the alloy oxidizes to form a large number of Al2O3 and a little Fe2O3, then, the enrichment of Al caused by Fe oxidization combines with O to form Al2O3.
文摘The positron annihilation lifetimes and the Doppler broadening by slow positron beam are measured in thin Fe films with thickness 500 nm, a thin Hf film with thickness 100 nm, and the bilayer Fe (50 nm)/Hf (50 nm) on quartz glass substrate. We have analyzed the behavior in vacancy-type defects in each layer through some deposition temperatures and annealing. It is observed that the thin Fe film, the thin Hf film, and the bilayer Fe (50 nm)/Hf (50 nm) already contain many vacancy-type defects. We have investigated the change of densities of the vacancy-carbon complex and the small vacancy-cluster with carbons, through solid-state amorphization of Fe (50 nm)/Hf (50 nm) bilayer.
文摘Thin films of iron(Fe)-doped titanium dioxide(Fe:TiO_(2))T were prepared by sol–gel spin coating technique and further calcined at 450℃.The structural and optical properties of Fe-doped TiO_(2) thin films were investigated by X-ray diffraction(XRD),scanning electron microscopy(SEM),ultraviolet–visible spectroscopy(UV–vis)and atomic force microscopic(AFM)techniques.The XRD results confirm the nanostructured TiO_(2) thin films having crystalline nature with anatase phase.The characterization results show that the calcined thin films having high crystallinity and the effect of iron substitution lead to decreased crystallinity.The SEM investigations of Fe-doped TiO_(2) films also gave evidence that the films were continuous spherical shaped particles with a nanometric range of grain size and film was porous in nature.AFM analysis establishes that the uniformity of the TiO_(2) thin film with average roughness values.The optical measurements show that the films having high transparency in the visible region and the optical band gap energy of Fe-doped TiO_(2) film with iron(Fe)decrease with increase in iron content.These important requirements for the Fe:TiO_(2) films are to be used as window layers in solar cells.
文摘The room temperature stability and crystallization of amorphous Nd_xFe_(1-x)thin films with x=0.06—0.90,prepared by flash evaporation at 77 K,were investigated by X-ray diffraction and TEM observation.The amorphous Nd_xFe_(1-x)films are stable at room temperature when 0.19<x<0.50.Crystallized phases grow along the surface of film as very thin flakes and become thick only at relatively high temperatures.After complete crystallization,the Nd_xFe_(1-x)films with x<0.50 are composed of Nd_2Fe-(17)and metal Nd,but no NdFe2,a phase expected to occur by phase diagram.
