The ultrasonic, magnetic and transport properties of Nd0.5Ca0.5Mn1-xAlxO3 （x=0, 0.03） were studied from 15 to 300 K. The temperature dependencies of resistivity and magnetization show that Nd0.5Ca0.5MnO3 undergoes a...The ultrasonic, magnetic and transport properties of Nd0.5Ca0.5Mn1-xAlxO3 （x=0, 0.03） were studied from 15 to 300 K. The temperature dependencies of resistivity and magnetization show that Nd0.5Ca0.5MnO3 undergoes a charge ordering transition at TCO-257 K. An obvious softening of the longitudinal sound velocity above TCO and a dramatic stiffening below Too accompanied by an attenuation peak were observed. These features imply a strong electron phonom interaction via the Jahn-Teller effect iu the sample, Another broad attenuation peak was observed at around Tp-80 K. This anomaly is attributed to the phase separtion between the antiferromagnetic （AFM） and paramagnetic （PM） phases and gives a direct evidence for spin-phonon coupling in the compound. For the x=0.03 sample, both the minimum of sound velocity and attenuation peaks shift to a lower temperature. The results indicate that the charge ordering and CE-type AFM state in Nd0.5Ca0.5MnO3 are both partially suppressed by replacing Mn with A1.展开更多
CdS thin films were prepared by chemical-bath-deposited method and the effect of temperature and time on the properties of CdS thin films was studied. Independent of the deposited temperature, the growth was mainly co...CdS thin films were prepared by chemical-bath-deposited method and the effect of temperature and time on the properties of CdS thin films was studied. Independent of the deposited temperature, the growth was mainly controlled by the ion-by-ion growth mechanism at the beginning of the film deposition, then the cluster-by-cluster mechanism came to be dominant. The growth rate increased faster with the increasing of temperature until the thickness reached the limitation, then thickness instead become thinner. The scanning electron micro- scope results revealed that the morphology of the CdS film changed from pinholes to rough, inhomogeneous surface with increasing deposition time and deposition temperature. The X- ray diffraction results showed the film structure was a mixture of two phases： hexagonal and cubic, and it was very important to controll deposition time to the film＇s crystal phase. All films in depth of approxilnate 100 nm existed above 65% transmittance, the absorption edge became ＂red-shift＂ with temperature rising. At 60 and 70℃, with 20 min deposited-time, the energy band gap was more than 2.42 eV and decreased with time, while at 80 and 90℃ the energy band gap was less than 2.42 eV and increased little when the time changed from 10min to 15 nfin at 80℃.展开更多
CuInSe2 （CIS） films with good crystalline quality were synthesized by electrodeposition followed by annealing in Se vapor at 530 ℃. The morphology, composition, crystal structure, optical and electrical properties ...CuInSe2 （CIS） films with good crystalline quality were synthesized by electrodeposition followed by annealing in Se vapor at 530 ℃. The morphology, composition, crystal structure, optical and electrical properties of the CIS films were investigated by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, Raman spectroscopy, UV-VISNIR spectroscopy, and admittance spectroscopy. The results revealed that the annealed CIS films had chalcopyrite structure and consisted of relatively large grains in the range of 500-1000 nm and single grain of films extend usually through the whole film thickness. The band gap of CIS films was 0.98 eV and carrier concentration was in the order of 1016 cm-3 after etching the Cu-Se compounds on the film surface. Solar cells with the structure of AZO/i-ZnO/CdS/CIS/Mo/glass were fabricated. Current density vs. voltage test under standard reported condition showed the solar cells with an area of 0.2 cm2 had a conversion efficiency of 0.96%. The underlying physics was also discussed.展开更多
基金supported by the National Natural Science Foundation of China(No.10274075)the Specialized Research Fund for the Doctoral Program of Higher Education(No.20030358056).
文摘The ultrasonic, magnetic and transport properties of Nd0.5Ca0.5Mn1-xAlxO3 （x=0, 0.03） were studied from 15 to 300 K. The temperature dependencies of resistivity and magnetization show that Nd0.5Ca0.5MnO3 undergoes a charge ordering transition at TCO-257 K. An obvious softening of the longitudinal sound velocity above TCO and a dramatic stiffening below Too accompanied by an attenuation peak were observed. These features imply a strong electron phonom interaction via the Jahn-Teller effect iu the sample, Another broad attenuation peak was observed at around Tp-80 K. This anomaly is attributed to the phase separtion between the antiferromagnetic （AFM） and paramagnetic （PM） phases and gives a direct evidence for spin-phonon coupling in the compound. For the x=0.03 sample, both the minimum of sound velocity and attenuation peaks shift to a lower temperature. The results indicate that the charge ordering and CE-type AFM state in Nd0.5Ca0.5MnO3 are both partially suppressed by replacing Mn with A1.
文摘CdS thin films were prepared by chemical-bath-deposited method and the effect of temperature and time on the properties of CdS thin films was studied. Independent of the deposited temperature, the growth was mainly controlled by the ion-by-ion growth mechanism at the beginning of the film deposition, then the cluster-by-cluster mechanism came to be dominant. The growth rate increased faster with the increasing of temperature until the thickness reached the limitation, then thickness instead become thinner. The scanning electron micro- scope results revealed that the morphology of the CdS film changed from pinholes to rough, inhomogeneous surface with increasing deposition time and deposition temperature. The X- ray diffraction results showed the film structure was a mixture of two phases： hexagonal and cubic, and it was very important to controll deposition time to the film＇s crystal phase. All films in depth of approxilnate 100 nm existed above 65% transmittance, the absorption edge became ＂red-shift＂ with temperature rising. At 60 and 70℃, with 20 min deposited-time, the energy band gap was more than 2.42 eV and decreased with time, while at 80 and 90℃ the energy band gap was less than 2.42 eV and increased little when the time changed from 10min to 15 nfin at 80℃.
文摘CuInSe2 （CIS） films with good crystalline quality were synthesized by electrodeposition followed by annealing in Se vapor at 530 ℃. The morphology, composition, crystal structure, optical and electrical properties of the CIS films were investigated by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, Raman spectroscopy, UV-VISNIR spectroscopy, and admittance spectroscopy. The results revealed that the annealed CIS films had chalcopyrite structure and consisted of relatively large grains in the range of 500-1000 nm and single grain of films extend usually through the whole film thickness. The band gap of CIS films was 0.98 eV and carrier concentration was in the order of 1016 cm-3 after etching the Cu-Se compounds on the film surface. Solar cells with the structure of AZO/i-ZnO/CdS/CIS/Mo/glass were fabricated. Current density vs. voltage test under standard reported condition showed the solar cells with an area of 0.2 cm2 had a conversion efficiency of 0.96%. The underlying physics was also discussed.
