Two-dimensional(2D)semiconductors have attracted great attention to extend Moore’s law,which motivates the quest for fast growth of high-quality materials.However,taking MoS_(2) as an example,current methods yield 2D...Two-dimensional(2D)semiconductors have attracted great attention to extend Moore’s law,which motivates the quest for fast growth of high-quality materials.However,taking MoS_(2) as an example,current methods yield 2D MoS_(2) with a low growth rate and poor quality with vacancy concentrations three to five orders of magnitude higher than silicon and other commercial semiconductors.Here,we develop a strategy of using an intermediate product of iodine as a transport agent to carry metal precursors efficiently for ultrafast growth of high-quality MoS_(2).The grown MoS_(2) has the lowest density of sulfur vacancies(~1.41×10^(12) cm^(−2))reported so far and excellent electrical properties with high on/off current ratios of 108 and carrier mobility of 175 cm^(2) V^(−1) s^(−1).Theoretical calculations show that by incorporating iodine,the nucleation barrier of MoS_(2) growth with sulfur-terminated edges reduces dramatically.The sufficient supply of precursor and low nucleation energy together boost the ultrafast growth of sub-millimeter MoS_(2) domains within seconds.This work provides an effective method for the ultrafast growth of 2D semiconductors with high quality,which will promote their applications.展开更多
The B2O3-doped MgTiO3 powders and ceramics have been prepared by sol-gel method using Mg（NO3）2-6H2O, Ti（C4H9O）4 and H3BO3 as the starting materials. The sintering behavior and microwave dielectric properties of ce...The B2O3-doped MgTiO3 powders and ceramics have been prepared by sol-gel method using Mg（NO3）2-6H2O, Ti（C4H9O）4 and H3BO3 as the starting materials. The sintering behavior and microwave dielectric properties of ceramics prepared from powders with different particle sizes were investigated. The gels were calcined at 650, 700, 750, 800, 850 and 900 ℃ and the derived particle sizes of powders were 20-30 nm, 30-40 nm, 40-60 nm, 60-90 nm, 90-120 nm and 120-150 nm, respectively. The nanoparticles with the size of 30-60 nm benefited the sintering process with high surface energy whereas nanoparticles with the size of 20-30 nm damaged the microwave dielectric properties due to the pores in the ceramics. The addition of B203 used as a liquid sintering aid reduced the sintering temperature of MgTiO3 ceramic, which was supposed to enter the MgTi03 lattice and resulted in the formation of （MgTi）2（BO3）O phase. The B203-doped MgTiO3 ceramic sintered at 1100℃ and prepared from the nanoparticles of 40-60 nm had compact structure and exhibited good microwave dielectric properties： εr=17.63, Q x f=33,768 GHz and Tf=-48X 10-6 ℃-1.展开更多
The effects of Li~＋ co-doping concentration on the structure, upconversion luminescence and temperature sensing behavior of Er^（3＋）：La_2O_3 phosphors were investigated. X-ray diffraction and scanning electron mic...The effects of Li~＋ co-doping concentration on the structure, upconversion luminescence and temperature sensing behavior of Er^（3＋）：La_2O_3 phosphors were investigated. X-ray diffraction and scanning electron microscopy observations reveal that Li~＋ ion co-doping can change the lattice parameter of La_2O_3 host and increase the particle size of the samples. The optical investigation shows that co-doping of Li~＋ ions can enhance the upconversion emission of Er^（3＋） ions in La_2O_3 matrix effectively. Most importantly, the temperature sensing sensitivity of the samples is found to be dependent on Li~＋ co-doping concentration,when the emission intensity ratio of the（~2H_（11/2）→~4 I_（15/2）） and（~4 S_（3/2）→~4 I_（15/2）） transitions of Er^（3＋） is chosen as the thermometric index. Both of the optimum upconversion luminescence and temperature sensing sensitivity are obtained for 7 mol% Li~＋ co-doped sample. When the Li~＋ concentration is beyond 7 mol%,both the quenching in upconversion intensity and the degradation of temperature sensitivity are observed, which may be due to the serious distortion in local crystal field around Er^（3＋） ions caused by the excess Li~＋ ions.展开更多
Ho^3+/Yb^3+: BaMoO4 phosphors with different concentrations were fabricated by a gel combustion method.The upconversion(UC) luminescence, intrinsic optical bistability, and the corresponding mechanisms were reported f...Ho^3+/Yb^3+: BaMoO4 phosphors with different concentrations were fabricated by a gel combustion method.The upconversion(UC) luminescence, intrinsic optical bistability, and the corresponding mechanisms were reported for the present system. The optical thermometric properties based on red(^5F5→^5I8) and green(^5F4/^5S2→^5I8) emissions were studied. The sensing sensitivities could be tuned by manipulating the cooperative energy transfer process. The highest absolute sensitivity was 99 × 10^-4 K^-1 at 573 K, which is larger than that of many previous UC materials.展开更多
基金This work was supported by the National Key R&D Program(2018YFA0307300)the National Natural Science Foundation of China(51991343,51991340,52188101 and 51920105002)+3 种基金the China Postdoctoral Science Foundation(2021M701948)the National Science Fund for Distinguished Young Scholars(52125309)Guangdong Innovative and Entrepreneurial Research Team Program(2017ZT07C341)Shenzhen Basic Research Project(JCYJ20200109144616617 and JCYJ20220818101014029).
文摘Two-dimensional(2D)semiconductors have attracted great attention to extend Moore’s law,which motivates the quest for fast growth of high-quality materials.However,taking MoS_(2) as an example,current methods yield 2D MoS_(2) with a low growth rate and poor quality with vacancy concentrations three to five orders of magnitude higher than silicon and other commercial semiconductors.Here,we develop a strategy of using an intermediate product of iodine as a transport agent to carry metal precursors efficiently for ultrafast growth of high-quality MoS_(2).The grown MoS_(2) has the lowest density of sulfur vacancies(~1.41×10^(12) cm^(−2))reported so far and excellent electrical properties with high on/off current ratios of 108 and carrier mobility of 175 cm^(2) V^(−1) s^(−1).Theoretical calculations show that by incorporating iodine,the nucleation barrier of MoS_(2) growth with sulfur-terminated edges reduces dramatically.The sufficient supply of precursor and low nucleation energy together boost the ultrafast growth of sub-millimeter MoS_(2) domains within seconds.This work provides an effective method for the ultrafast growth of 2D semiconductors with high quality,which will promote their applications.
基金supported by the National Science Fund for Distinguished Young Scholars(52125309)the National Natural Science Foundation of China(51991343,51920105002,51991340,52188101,and 11974156)+3 种基金Guangdong Innovative and Entrepreneurial Research Team Program(2017ZT07C341 and 2019ZT08C044)the Bureau of Industry and Information Technology of Shenzhen for the “2017 Graphene Manufacturing Innovation Center Project”(201901171523)Shenzhen Basic Research Project(JCYJ20200109144616617 and JCYJ20190809180605522)Shenzhen Science and Technology Program(KQTD20190929173815000 and 20200925161102001)。
基金supported by Project of New Century Excellent Talents in University (No. NCET-07-0786)the Science and Technology Innovative Research Team of Zhejiang Province (No. 2009R50010)the Zhejiang Science and Technology Innovation Projects for students (No. 2009R409014)
文摘The B2O3-doped MgTiO3 powders and ceramics have been prepared by sol-gel method using Mg（NO3）2-6H2O, Ti（C4H9O）4 and H3BO3 as the starting materials. The sintering behavior and microwave dielectric properties of ceramics prepared from powders with different particle sizes were investigated. The gels were calcined at 650, 700, 750, 800, 850 and 900 ℃ and the derived particle sizes of powders were 20-30 nm, 30-40 nm, 40-60 nm, 60-90 nm, 90-120 nm and 120-150 nm, respectively. The nanoparticles with the size of 30-60 nm benefited the sintering process with high surface energy whereas nanoparticles with the size of 20-30 nm damaged the microwave dielectric properties due to the pores in the ceramics. The addition of B203 used as a liquid sintering aid reduced the sintering temperature of MgTiO3 ceramic, which was supposed to enter the MgTi03 lattice and resulted in the formation of （MgTi）2（BO3）O phase. The B203-doped MgTiO3 ceramic sintered at 1100℃ and prepared from the nanoparticles of 40-60 nm had compact structure and exhibited good microwave dielectric properties： εr=17.63, Q x f=33,768 GHz and Tf=-48X 10-6 ℃-1.
基金Project supported by the National Natural Science Foundation of China(51401197,61605192)the Natural Science Foundation of Zhejiang Province(LQ13F050003,LZ14B010001)
文摘The effects of Li~＋ co-doping concentration on the structure, upconversion luminescence and temperature sensing behavior of Er^（3＋）：La_2O_3 phosphors were investigated. X-ray diffraction and scanning electron microscopy observations reveal that Li~＋ ion co-doping can change the lattice parameter of La_2O_3 host and increase the particle size of the samples. The optical investigation shows that co-doping of Li~＋ ions can enhance the upconversion emission of Er^（3＋） ions in La_2O_3 matrix effectively. Most importantly, the temperature sensing sensitivity of the samples is found to be dependent on Li~＋ co-doping concentration,when the emission intensity ratio of the（~2H_（11/2）→~4 I_（15/2）） and（~4 S_（3/2）→~4 I_（15/2）） transitions of Er^（3＋） is chosen as the thermometric index. Both of the optimum upconversion luminescence and temperature sensing sensitivity are obtained for 7 mol% Li~＋ co-doped sample. When the Li~＋ concentration is beyond 7 mol%,both the quenching in upconversion intensity and the degradation of temperature sensitivity are observed, which may be due to the serious distortion in local crystal field around Er^（3＋） ions caused by the excess Li~＋ ions.
基金supported by the National Natural Science Foundation of China(51920105002,51991340,51991343,11974156)the National Key R&D Program of China(2018YFA0307200)+8 种基金Guangdong International Science Collaboration Project(2019A050510001)the Bureau of Industry and Information Technology of Shenzhen for the"2017 Graphene Manufacturing Innovation Center Project"(201901171523)Shenzhen Basic Research Project(WDZC20200819095319002,JC YJ20190809180605522,JCYJ20200109144620815,JCYJ20200109144616617)Shenzhen Science and Technology Program(KQTD20190929173815000)the Science,Technology and Innovation Commission of Shenzhen Municipality(ZDSYS20190902092905285)the assistance of SUSTech Core Research Facilities,especially technical support from Pico-Centre that receives support from Presidential fund and Development and Reform Commission of Shenzhen Municipalitysupported by the fund of the Guangdong Provincial Key Laboratory of Computational Science and Material Design(2019B030301001)the Introduced Innovative R&D Team of Guangdong(2017ZT07C062,2019ZT08C044)supported by the Center for Computational Science and Engineering of Southern University of Science and Technology。
基金supported by the Natural Science Foundation of Zhejiang Province(Nos.LY18E020008 and LD18F050001)the National Natural Science Foundation of China(No.61605192)
文摘Ho^3+/Yb^3+: BaMoO4 phosphors with different concentrations were fabricated by a gel combustion method.The upconversion(UC) luminescence, intrinsic optical bistability, and the corresponding mechanisms were reported for the present system. The optical thermometric properties based on red(^5F5→^5I8) and green(^5F4/^5S2→^5I8) emissions were studied. The sensing sensitivities could be tuned by manipulating the cooperative energy transfer process. The highest absolute sensitivity was 99 × 10^-4 K^-1 at 573 K, which is larger than that of many previous UC materials.
