Perovskite-based materials can be widely used in the aerospace and transportation field. Perovskite man-ganese oxides La0.7Sr0.3MnO3 （LSMO） thin films were grown on LaAlO3 （100） and Si （100） single crystal sub-s...Perovskite-based materials can be widely used in the aerospace and transportation field. Perovskite man-ganese oxides La0.7Sr0.3MnO3 （LSMO） thin films were grown on LaAlO3 （100） and Si （100） single crystal sub-strates by the polymer-assisted chemical solution deposi-tion （PACSD） method. Electronic transport behavior, microstructure, and magnetoresistance （MR） of LSMO thin films on different substrates were investigated. The resis-tance of LSMO films fabricated on LaAlO3 substrates is smaller than that on the Si substrates. The magnetic field reduces resistance of LSMO films both on Si and LAO in the wide temperature region, when the insulator-metal transition temperature shifts to higher temperature. The low-field magnetoresistance of LSMO films on Si in low temperature range at 1 T is larger than that of LSMO films on LAO. However, the MR of LSMO film on LAO films at room-temperature is about 5.17%. The thin films are smooth and dense with uniform nanocrystal size grain. These results demonstrate that PACSD is an effective technique for producing high quality LSMO films, which is significant to improve the magnetic properties and the application of automotive sensor.展开更多
A genetic algorithm （GA） was studied to simultaneously determine the thermal transport properties and the contact resistance of thin films deposited on a thick substrate. A pulsed photothermal reflectance （PPR） sy...A genetic algorithm （GA） was studied to simultaneously determine the thermal transport properties and the contact resistance of thin films deposited on a thick substrate. A pulsed photothermal reflectance （PPR） system was employed for the measurements. The GA was used to extract the thermal properties. Measurements were performed on SiO2 thin films of different thicknesses on silicon substrate. The results show that the GA accompanied with the PPR system is useful for the simultaneous determination of thermal properties of thin films on a substrate.展开更多
High quality Nb films were successfully prepared on both flexible polyimide(PI)and rigid Al2O3substrates and their transport properties were systematically studied at various applied currents,external magnetic fields,...High quality Nb films were successfully prepared on both flexible polyimide(PI)and rigid Al2O3substrates and their transport properties were systematically studied at various applied currents,external magnetic fields,and sample orientations.It is found that a curved Nb/PI film exhibits quite different superconducting transition and vortex dynamics compared to the flat Nb/Al2O3film.For the curved Nb/PI film,smooth superconducting transitions were obtained at low currents,while unexpected cascade structures were revealed in theρ(T)curves at high currents.We attribute this phenomenon to the gradient distribution of vortex density together with a variation of superconductivity along the curved film.In addition,reentrant superconductivity was induced in the curved Nb/PI thin film by properly choosing the measurement conditions.We attribute this effect to the vortex pinning from both in-plane vortices and out-of-plane vortices.This work reveals the complex transport properties of curved superconducting thin films,providing important insights for further theoretical investigations and practical developments of flexible superconductors.展开更多
Electronic transport properties of magnetically disordered R(-3)c phase Fe1.5Ti0.5O3-δ thin films epitaxially grown on Al2O3(0001) substrates have been studied. The measured magnetization in configurations with the m...Electronic transport properties of magnetically disordered R(-3)c phase Fe1.5Ti0.5O3-δ thin films epitaxially grown on Al2O3(0001) substrates have been studied. The measured magnetization in configurations with the magnetic field perpendicular and parallel to the film plane shows weak values of 0.1μB/formula compared to the theoretical value of 2μB/formula and a strong anisotropy with no saturation in perpendicular configuration. These properties are associated with the ato- mic scale disorder of Ti/Fe ions along c-axis. At zero-magnetic field and within the temperature range of 80 K to 400 K, the conduction mechanism appears to be Efros-Shklovskii variable range hopping with a carrier localization length of ξ0= 0.86nm. Magneto-resistance (MR) is positive in perpendicular configuration, while it is negative in parallel configuration, with significant values of MR = 27%- 37% at room temperature at 9 Tesla. Electron localization lengths were deduced from experiment for different external magnetic fields. The origin of magneto-resistance observed in experiment, is discussed.展开更多
Epitaxial growth of the Lag0.5Sr0.5CoO3(LSCO) thin films has been realized on LaAl03, SrTiO3 and MgO substrates by pulsed laser deposition. The epitaxial growth behavior and the electrical transport properties of thes...Epitaxial growth of the Lag0.5Sr0.5CoO3(LSCO) thin films has been realized on LaAl03, SrTiO3 and MgO substrates by pulsed laser deposition. The epitaxial growth behavior and the electrical transport properties of these films were studied systematically. The temperature dependencies of the resistivity of the film have been determined. Studies indicate that close dependencies exist between the crystal structures and the electrical transport properties of the epitaxial LSCO films, and that the epitaxial thin films are of low resistivity and metallic conductive features. The epitaxial films deposited on the LaAlO3 substrates at about 700℃ possess the optimal properties compared with the others. Discussions of the dependencies and the mechanisms of the epitaxial structures on the electrical transport properties of the LSCO films have been made.展开更多
La2/3 Sr1/3 Mn1-x ZnxO3films （x =0.05, 0.1,0.3, and 0.5） were prepared using magnetron sputtering method, and the effect of Zn doping on transport properties of the films was studied. An analysis of X-ray diffractio...La2/3 Sr1/3 Mn1-x ZnxO3films （x =0.05, 0.1,0.3, and 0.5） were prepared using magnetron sputtering method, and the effect of Zn doping on transport properties of the films was studied. An analysis of X-ray diffraction showed that the main phase of the bulk target was orthorhombic and the films had better epitaxial character. It was found that the films with x =0.05 and x =0.1 exhibited typical insulator-metal transition. No transition of the films with x≥0.3 was observed and the dominant transport was variable-range hopping due to observable secondary phase ZnO. These could be attributed to the Zn doping effect on manganites.展开更多
The transport properties in the La2/3（Ca（1-x）Sr（x））1/3MnO3 （x=0.1/3, 2/3） films prepared using the RF magnetron sputtering method were investigated, The effect of the Ca, Sr double-doping at the A position in ...The transport properties in the La2/3（Ca（1-x）Sr（x））1/3MnO3 （x=0.1/3, 2/3） films prepared using the RF magnetron sputtering method were investigated, The effect of the Ca, Sr double-doping at the A position in the La（2/3）A（1/3）MnO3 on the structure of the targets and transport of the films has been studied. With the increase of x, the structures of the targets transform from the rhombohedral phase to the cubic phase; the metal-insulator phase transition temperature （Tp） of the films increases; and the corresponding peak resistivity decreases. All the phenomena can be qualitatively explained by the lattice effect.展开更多
By finely controlling the deposition parameters in the pulsed electron deposition process, granular La 2/3 Ca 1/3 MnO 3 （LCMO） film was grown on silicon substrates. The substrate temperature, ambient pressure in the...By finely controlling the deposition parameters in the pulsed electron deposition process, granular La 2/3 Ca 1/3 MnO 3 （LCMO） film was grown on silicon substrates. The substrate temperature, ambient pressure in the deposition chamber and acceleration potential for the electron beam were all found to affect the grain size of the film, resulting in different morphologies of the samples. Transport properties of the obtained granular films, especially the magnetoresistance （MR）, were studied. Prominent low-field MR was observed in all samples, indicating the forming of grain boundaries in the sample. The low-field MR show great sensitive to the morphology evolution, which reaches the highest value of about 40% for the sample with the grain size of about 250 nm. More interestingly, positive-MR （p-MR） was also detected above 300 K when low magnetic field applying, whereas it disappeared with higher magnetic field applied up to 1.5 and 2 Tesla. Instead of the spin- polarized tunneling process being commonly regarded as a responsible reason, lattice mismatch between LCMO film and silicon substrate appears to be the origin of the p-MR展开更多
Electrical properties of C/Ni films are studied using four mosaic targets made of pure graphite and stripes of nickel with the surface areas of 1.78,3.21,3.92 and 4.64%.The conductivity data in the temperature range o...Electrical properties of C/Ni films are studied using four mosaic targets made of pure graphite and stripes of nickel with the surface areas of 1.78,3.21,3.92 and 4.64%.The conductivity data in the temperature range of400-500 K shows the extended state conduction.The conductivity data in the temperature range of 150-300 K shows the multi-phonon hopping conduction.The Berthelot-type conduction dominates in the temperature range of 50-150 K.The conductivity of the films in the temperature range about 〈 50 K is described in terms of variable-range hopping conduction.In low temperatures,the localized density of state around Fermi level（F）for the film deposition with 3.92% nickel has a maximum value of about 56.2×10^（17）cm^（-3）eV^（-1） with the minimum average hopping distance of about 3.43 × 10^（-6） cm.展开更多
We investigate the electronic-transport properties of two-dimensional monolayer films from Au-P-Au molecular junction to Au-Si-Au molecular junction using elastic scattering Green＇s function theory. In the process of...We investigate the electronic-transport properties of two-dimensional monolayer films from Au-P-Au molecular junction to Au-Si-Au molecular junction using elastic scattering Green＇s function theory. In the process of replacing the P atoms with Si atoms every other line from the middle of monolayer blue phosphorus molecular structure, the substitution of Si atoms changes the properties of Au-P-Au molecular junction significantly. Interestingly, the current value has a symmetric change as a parabolic curve with the peak appearing in Au-Si_1P_1-Au molecular junction, which provides the most stable current of 15.00 nA in a wide voltage range of 0.70-2.70 V.Moreover, the current-voltage characteristics of the structures indicate that the steps tend to disappear revealing the property similar to metal when the Si atoms dominate the molecular junction.展开更多
In this paper we report a new method to fabricate nanostructured films, La0.67Ca0.33MnO3 （LCMO） nanostructured films have been fabricated by using pulsed electron beam deposition （PED） on anodized aluminium oxide ...In this paper we report a new method to fabricate nanostructured films, La0.67Ca0.33MnO3 （LCMO） nanostructured films have been fabricated by using pulsed electron beam deposition （PED） on anodized aluminium oxide （AAO） membranes, The magnetic and electronic transport properties are investigated by using the Quantum Design physics properties measurement system （PPMS） and magnetic properties measurement system （MPMS）. The resistance peak temperature （Tp） is about 85 K and the Curie temperature （To） is about 250 K for the LCMO film on an AAO membrane with a pore diameter of 20nm. Large magnetoresistance ratio （MR） is observed near Tp. The MR is as high as 85% under 1 T magnetic field. The great enhancement of MR at low magnetic fields could be attributed to the lattice distortion and the grain boundary that are induced by the nanopores on the AAO membrane.展开更多
基金supported by the Program of International S&T Cooperation 2013DFA51050National Magnetic Confinement Fusion Science Program (2011GB112001)+2 种基金Science Foundation of Sichuan Province (2011JY0031, 2011JY0130)the financial support of the National Natural Science Foundation of China (No. 51271155, No. 51002125)the Fundamental Research Funds for the Central Universities (SWJTU12CX018)
文摘Perovskite-based materials can be widely used in the aerospace and transportation field. Perovskite man-ganese oxides La0.7Sr0.3MnO3 （LSMO） thin films were grown on LaAlO3 （100） and Si （100） single crystal sub-strates by the polymer-assisted chemical solution deposi-tion （PACSD） method. Electronic transport behavior, microstructure, and magnetoresistance （MR） of LSMO thin films on different substrates were investigated. The resis-tance of LSMO films fabricated on LaAlO3 substrates is smaller than that on the Si substrates. The magnetic field reduces resistance of LSMO films both on Si and LAO in the wide temperature region, when the insulator-metal transition temperature shifts to higher temperature. The low-field magnetoresistance of LSMO films on Si in low temperature range at 1 T is larger than that of LSMO films on LAO. However, the MR of LSMO film on LAO films at room-temperature is about 5.17%. The thin films are smooth and dense with uniform nanocrystal size grain. These results demonstrate that PACSD is an effective technique for producing high quality LSMO films, which is significant to improve the magnetic properties and the application of automotive sensor.
基金the National Natural Science Foundation of China under Grant Nos. 59995550-5 , 90207003.
文摘A genetic algorithm （GA） was studied to simultaneously determine the thermal transport properties and the contact resistance of thin films deposited on a thick substrate. A pulsed photothermal reflectance （PPR） system was employed for the measurements. The GA was used to extract the thermal properties. Measurements were performed on SiO2 thin films of different thicknesses on silicon substrate. The results show that the GA accompanied with the PPR system is useful for the simultaneous determination of thermal properties of thin films on a substrate.
基金Project supported by the National Key Basic Research Program of China(Grant Nos.2021YFA0718700,2018YFB0704102,2017YFA0303003,2017YFA0302902,2016YFA0300301,and 2021YFA0718802)the National Natural Science Foundation of China(Grant Nos.11927808,11834016,118115301,119611410,11961141008,61727805+5 种基金11961141002)the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(CAS)(Grant Nos.QYZDB-SSW-SLH008 and QYZDY-SSW-SLH001)CAS Interdisciplinary Innovation Team,the Strategic Priority Research Program(B)of CAS(Grant Nos.XDB25000000and XDB33000000)the Beijing Natural Science Foundation(Grant No.Z190008)the Key-Area Research and Development Program of Guangdong Province,China(Grant No.2020B0101340002)the support from the China Postdoctoral Science Foundation(Grant No.2022M711497)。
文摘High quality Nb films were successfully prepared on both flexible polyimide(PI)and rigid Al2O3substrates and their transport properties were systematically studied at various applied currents,external magnetic fields,and sample orientations.It is found that a curved Nb/PI film exhibits quite different superconducting transition and vortex dynamics compared to the flat Nb/Al2O3film.For the curved Nb/PI film,smooth superconducting transitions were obtained at low currents,while unexpected cascade structures were revealed in theρ(T)curves at high currents.We attribute this phenomenon to the gradient distribution of vortex density together with a variation of superconductivity along the curved film.In addition,reentrant superconductivity was induced in the curved Nb/PI thin film by properly choosing the measurement conditions.We attribute this effect to the vortex pinning from both in-plane vortices and out-of-plane vortices.This work reveals the complex transport properties of curved superconducting thin films,providing important insights for further theoretical investigations and practical developments of flexible superconductors.
文摘Electronic transport properties of magnetically disordered R(-3)c phase Fe1.5Ti0.5O3-δ thin films epitaxially grown on Al2O3(0001) substrates have been studied. The measured magnetization in configurations with the magnetic field perpendicular and parallel to the film plane shows weak values of 0.1μB/formula compared to the theoretical value of 2μB/formula and a strong anisotropy with no saturation in perpendicular configuration. These properties are associated with the ato- mic scale disorder of Ti/Fe ions along c-axis. At zero-magnetic field and within the temperature range of 80 K to 400 K, the conduction mechanism appears to be Efros-Shklovskii variable range hopping with a carrier localization length of ξ0= 0.86nm. Magneto-resistance (MR) is positive in perpendicular configuration, while it is negative in parallel configuration, with significant values of MR = 27%- 37% at room temperature at 9 Tesla. Electron localization lengths were deduced from experiment for different external magnetic fields. The origin of magneto-resistance observed in experiment, is discussed.
基金Project supported by the National Natural Science Foundation of China (Grant No. 19574003 and No. 19674001).
文摘Epitaxial growth of the Lag0.5Sr0.5CoO3(LSCO) thin films has been realized on LaAl03, SrTiO3 and MgO substrates by pulsed laser deposition. The epitaxial growth behavior and the electrical transport properties of these films were studied systematically. The temperature dependencies of the resistivity of the film have been determined. Studies indicate that close dependencies exist between the crystal structures and the electrical transport properties of the epitaxial LSCO films, and that the epitaxial thin films are of low resistivity and metallic conductive features. The epitaxial films deposited on the LaAlO3 substrates at about 700℃ possess the optimal properties compared with the others. Discussions of the dependencies and the mechanisms of the epitaxial structures on the electrical transport properties of the LSCO films have been made.
基金Project supported by the National Natural Science Foundation of China (50331040, 50702046)
文摘La2/3 Sr1/3 Mn1-x ZnxO3films （x =0.05, 0.1,0.3, and 0.5） were prepared using magnetron sputtering method, and the effect of Zn doping on transport properties of the films was studied. An analysis of X-ray diffraction showed that the main phase of the bulk target was orthorhombic and the films had better epitaxial character. It was found that the films with x =0.05 and x =0.1 exhibited typical insulator-metal transition. No transition of the films with x≥0.3 was observed and the dominant transport was variable-range hopping due to observable secondary phase ZnO. These could be attributed to the Zn doping effect on manganites.
基金supported by the National Natural Science Foundation of China(No.50331040)the National Natural Science Foundation of Shaanxi Provice(No.2001C21)NWPU Doctor Foundation(cx200323)
文摘The transport properties in the La2/3（Ca（1-x）Sr（x））1/3MnO3 （x=0.1/3, 2/3） films prepared using the RF magnetron sputtering method were investigated, The effect of the Ca, Sr double-doping at the A position in the La（2/3）A（1/3）MnO3 on the structure of the targets and transport of the films has been studied. With the increase of x, the structures of the targets transform from the rhombohedral phase to the cubic phase; the metal-insulator phase transition temperature （Tp） of the films increases; and the corresponding peak resistivity decreases. All the phenomena can be qualitatively explained by the lattice effect.
基金Funded by the National Natural Science Foundation of China(No.10875107)the Aeronautical Science Foundation(No.2010ZF55013)+1 种基金the Basic and Advanced Technology Program of Henan Province (No.112300410229)the Foundation for University Young Key Teacher by Henan Province (No. 2010GGJS-146)
文摘By finely controlling the deposition parameters in the pulsed electron deposition process, granular La 2/3 Ca 1/3 MnO 3 （LCMO） film was grown on silicon substrates. The substrate temperature, ambient pressure in the deposition chamber and acceleration potential for the electron beam were all found to affect the grain size of the film, resulting in different morphologies of the samples. Transport properties of the obtained granular films, especially the magnetoresistance （MR）, were studied. Prominent low-field MR was observed in all samples, indicating the forming of grain boundaries in the sample. The low-field MR show great sensitive to the morphology evolution, which reaches the highest value of about 40% for the sample with the grain size of about 250 nm. More interestingly, positive-MR （p-MR） was also detected above 300 K when low magnetic field applying, whereas it disappeared with higher magnetic field applied up to 1.5 and 2 Tesla. Instead of the spin- polarized tunneling process being commonly regarded as a responsible reason, lattice mismatch between LCMO film and silicon substrate appears to be the origin of the p-MR
文摘Electrical properties of C/Ni films are studied using four mosaic targets made of pure graphite and stripes of nickel with the surface areas of 1.78,3.21,3.92 and 4.64%.The conductivity data in the temperature range of400-500 K shows the extended state conduction.The conductivity data in the temperature range of 150-300 K shows the multi-phonon hopping conduction.The Berthelot-type conduction dominates in the temperature range of 50-150 K.The conductivity of the films in the temperature range about 〈 50 K is described in terms of variable-range hopping conduction.In low temperatures,the localized density of state around Fermi level（F）for the film deposition with 3.92% nickel has a maximum value of about 56.2×10^（17）cm^（-3）eV^（-1） with the minimum average hopping distance of about 3.43 × 10^（-6） cm.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11374033,11774030,51735001 and 61775016the Fundamental Research Funds for the Central Universities under Grant No 2017CX10007
文摘We investigate the electronic-transport properties of two-dimensional monolayer films from Au-P-Au molecular junction to Au-Si-Au molecular junction using elastic scattering Green＇s function theory. In the process of replacing the P atoms with Si atoms every other line from the middle of monolayer blue phosphorus molecular structure, the substitution of Si atoms changes the properties of Au-P-Au molecular junction significantly. Interestingly, the current value has a symmetric change as a parabolic curve with the peak appearing in Au-Si_1P_1-Au molecular junction, which provides the most stable current of 15.00 nA in a wide voltage range of 0.70-2.70 V.Moreover, the current-voltage characteristics of the structures indicate that the steps tend to disappear revealing the property similar to metal when the Si atoms dominate the molecular junction.
基金Project supported by the key program of Natural Science Foundation of Zhejiang Provincial, China （Grant No Z605131）, National Natural Science Foundation of China （Grant No 60571029）, the ‘Hundred Talents Project＇ of Chinese Academy of Sciences, China, the Creative Research Group of the National Natural Science Foundation of China （Grant No 60321001）.
文摘In this paper we report a new method to fabricate nanostructured films, La0.67Ca0.33MnO3 （LCMO） nanostructured films have been fabricated by using pulsed electron beam deposition （PED） on anodized aluminium oxide （AAO） membranes, The magnetic and electronic transport properties are investigated by using the Quantum Design physics properties measurement system （PPMS） and magnetic properties measurement system （MPMS）. The resistance peak temperature （Tp） is about 85 K and the Curie temperature （To） is about 250 K for the LCMO film on an AAO membrane with a pore diameter of 20nm. Large magnetoresistance ratio （MR） is observed near Tp. The MR is as high as 85% under 1 T magnetic field. The great enhancement of MR at low magnetic fields could be attributed to the lattice distortion and the grain boundary that are induced by the nanopores on the AAO membrane.
