采用脉冲激光沉积(PLD)法制备了具有体心正交结构的单相PbPdO2薄膜,且PbPdO2薄膜具有(002)择优取向。根据EDS和XPS的测试结果证实PbPdO2中存在Pb空位和O空位。薄膜中Pb和Pd离子的价态分别为+2和+2价态。另外,PbPdO2的磁性主要和Pb空位...采用脉冲激光沉积(PLD)法制备了具有体心正交结构的单相PbPdO2薄膜,且PbPdO2薄膜具有(002)择优取向。根据EDS和XPS的测试结果证实PbPdO2中存在Pb空位和O空位。薄膜中Pb和Pd离子的价态分别为+2和+2价态。另外,PbPdO2的磁性主要和Pb空位诱导出的O1−有关。ρI (T)结果表明在PbPdO2中存在由电流诱导的正庞电致电阻(CER)效应。PbPdO2的金属–绝缘体转变温度(TMI)会随着电流和磁场的增大而增大,这表明了大的电流和磁场都可以推动薄膜的TMI向更高温区转移。最后,以薄膜中的Pb空位为中心,建立了内电场模型,很好地解释了PbPdO2的正CER效应。Single-phase PbPdO2 thin film with body-centered orthogonal structure have been prepared by pulsed laser deposition (PLD), and the PbPdO2 thin film has a (002) preferred orientation. The results of EDS and XPS confirmed the existence of Pb vacancy and O vacancy in PbPdO2 thin film. The valence states of Pb and Pd ions in the film are +2 and +2, respectively. In addition, the magnetism of PbPdO2 is mainly related to O1− induced by Pb vacancy. The ρI (T) results show that there is a positive current-induced CER effect in PbPdO2 thin film. The metal-insulator transition temperature (TMI) of PbPdO2 increases with the increase of the current and magnetic field, which indicates that large current and magnetic field can promote the TMI transfer of the film to a higher temperature region. Finally, an internal electric field model centered on the Pb vacancy in the film is established to explain the positive CER effect of PbPdO2.展开更多
Based on Peltier effect,Bi_(2)Te_(3)-based alloy is widely used in commercial solid-state refrigeration at room temperature.The mainstream strategies for enhancing room-temperature thermoelectric performance in Bi_(2)...Based on Peltier effect,Bi_(2)Te_(3)-based alloy is widely used in commercial solid-state refrigeration at room temperature.The mainstream strategies for enhancing room-temperature thermoelectric performance in Bi_(2)Te_(3)focus on band and microstructure engineering.However,a clear understanding of the modulation of band structure and scattering through such engineering remains still challenging,because the minority carriers compensate partially the overall transport properties for the narrow-gap Bi_(2)Te_(3)at room temperature(known as the bipolar effect).The purpose of this work is to model the transport properties near and far away from the bipolar effect region for Bi_(2)Te_(3)-based thermoelectric material by a two-band model taking contributions of both majority and minority carriers into account.This is endowed by shifting the Fermi level from the conduction band to the valence band during the modeling.A large amount of data of Bi_(2)Te_(3)-based materials is collected from various studies for the comparison between experimental and predicted properties.The fundamental parameters,such as the density of states effective masses and deformation potential coefficients,of Bi_(2)Te_(3)-based materials are quantified.The analysis can help find out the impact factors(e.g.the mobility ratio between conduction and valence bands)for the improvement of thermoelectric properties for Bi_(2)Te_(3)-based alloys.This work provides a convenient tool for analyzing and predicting the transport performance even in the presence of bipolar effect,which can facilitate the development of the narrow-gap thermoelectric semiconductors.展开更多
The fabrication and characterization of a Schottky-emitter heterojunction-collector UV-enhanced bipolar phototransistor （SHBT） are presented. The luminescence peak of the ZnO film is observed at 371nm in the PL spec...The fabrication and characterization of a Schottky-emitter heterojunction-collector UV-enhanced bipolar phototransistor （SHBT） are presented. The luminescence peak of the ZnO film is observed at 371nm in the PL spectrum. The sensitivity of the ultraviolet response from 200 to 400nm is enhanced noticeably, and the spectrum response at wavelengths longer than 400nm is also retained, The experiments show that the Au/n-ZnO/p-Si SHBT UV enhanced phototransistor enhances the sensitivity of the ultraviolet response noticeably. The UV response sensitivity at 370nm of the phototransistor is 5-10 times that of a ZnO/Si heterojunction UV enhanced photodiode.展开更多
文摘采用脉冲激光沉积(PLD)法制备了具有体心正交结构的单相PbPdO2薄膜,且PbPdO2薄膜具有(002)择优取向。根据EDS和XPS的测试结果证实PbPdO2中存在Pb空位和O空位。薄膜中Pb和Pd离子的价态分别为+2和+2价态。另外,PbPdO2的磁性主要和Pb空位诱导出的O1−有关。ρI (T)结果表明在PbPdO2中存在由电流诱导的正庞电致电阻(CER)效应。PbPdO2的金属–绝缘体转变温度(TMI)会随着电流和磁场的增大而增大,这表明了大的电流和磁场都可以推动薄膜的TMI向更高温区转移。最后,以薄膜中的Pb空位为中心,建立了内电场模型,很好地解释了PbPdO2的正CER效应。Single-phase PbPdO2 thin film with body-centered orthogonal structure have been prepared by pulsed laser deposition (PLD), and the PbPdO2 thin film has a (002) preferred orientation. The results of EDS and XPS confirmed the existence of Pb vacancy and O vacancy in PbPdO2 thin film. The valence states of Pb and Pd ions in the film are +2 and +2, respectively. In addition, the magnetism of PbPdO2 is mainly related to O1− induced by Pb vacancy. The ρI (T) results show that there is a positive current-induced CER effect in PbPdO2 thin film. The metal-insulator transition temperature (TMI) of PbPdO2 increases with the increase of the current and magnetic field, which indicates that large current and magnetic field can promote the TMI transfer of the film to a higher temperature region. Finally, an internal electric field model centered on the Pb vacancy in the film is established to explain the positive CER effect of PbPdO2.
基金National Natural Science Foundation of China(T2125008,92263108,92163203,52102292,52003198)Shanghai Rising-Star Program(23QA1409300)Innovation Program of Shanghai Municipal Education Commission(2021-01-07-00-07-E00096)。
文摘Based on Peltier effect,Bi_(2)Te_(3)-based alloy is widely used in commercial solid-state refrigeration at room temperature.The mainstream strategies for enhancing room-temperature thermoelectric performance in Bi_(2)Te_(3)focus on band and microstructure engineering.However,a clear understanding of the modulation of band structure and scattering through such engineering remains still challenging,because the minority carriers compensate partially the overall transport properties for the narrow-gap Bi_(2)Te_(3)at room temperature(known as the bipolar effect).The purpose of this work is to model the transport properties near and far away from the bipolar effect region for Bi_(2)Te_(3)-based thermoelectric material by a two-band model taking contributions of both majority and minority carriers into account.This is endowed by shifting the Fermi level from the conduction band to the valence band during the modeling.A large amount of data of Bi_(2)Te_(3)-based materials is collected from various studies for the comparison between experimental and predicted properties.The fundamental parameters,such as the density of states effective masses and deformation potential coefficients,of Bi_(2)Te_(3)-based materials are quantified.The analysis can help find out the impact factors(e.g.the mobility ratio between conduction and valence bands)for the improvement of thermoelectric properties for Bi_(2)Te_(3)-based alloys.This work provides a convenient tool for analyzing and predicting the transport performance even in the presence of bipolar effect,which can facilitate the development of the narrow-gap thermoelectric semiconductors.
文摘The fabrication and characterization of a Schottky-emitter heterojunction-collector UV-enhanced bipolar phototransistor （SHBT） are presented. The luminescence peak of the ZnO film is observed at 371nm in the PL spectrum. The sensitivity of the ultraviolet response from 200 to 400nm is enhanced noticeably, and the spectrum response at wavelengths longer than 400nm is also retained, The experiments show that the Au/n-ZnO/p-Si SHBT UV enhanced phototransistor enhances the sensitivity of the ultraviolet response noticeably. The UV response sensitivity at 370nm of the phototransistor is 5-10 times that of a ZnO/Si heterojunction UV enhanced photodiode.
