Thin films of millimeter-scale continuous monolayer WS_(2) have been grown on SiO_(2)/Si substrate,followed by the deposition ofβ-In_(2)Se_(3) crystals on monolayer WS2 to prepare In_(2)Se_(3)/WS_(2) van deWaals hete...Thin films of millimeter-scale continuous monolayer WS_(2) have been grown on SiO_(2)/Si substrate,followed by the deposition ofβ-In_(2)Se_(3) crystals on monolayer WS2 to prepare In_(2)Se_(3)/WS_(2) van deWaals heterostructures by a two-step chemical vapor deposition(CVD)method.After the growth of In_(2)Se_(3) at elevated temperatures,high densities of In_(2)Se_(3)/WS_(2) heterostructure bubbles with monolayer to multilayerβ-In_(2)Se_(3) crystals atop are observed.Fluorescence of the resultantβ-In_(2)Se_(3)/WS_(2) heterostructure is greatly enhanced in intensity upon the formation of bubbles,which are evidenced by the Newton’s rings in optical image owing to constructive and destructive interference.In photoluminescence(PL)mapping images of monolayerβ-In_(2)Se_(3)/monolayer WS2 heterobilayer bubble,significant oscillatory behavior of emission intensity is demonstrated due to constructive and destructive interference.However,oscillatory behaviors of peak position are also observed and come from a local heating effect induced by an excitation laser beam.The oscillatory mechanism of PL is further verified by changing the exterior pressure of bubbles placed in a home-made vacuum chamber.In addition,redshifted in peak position and broadening in peak width are observed due to strain effect during decreasing the exterior pressure of bubbles.展开更多
rickets hardness calculations of eleven wurtzite-structured semiconductors are performed based on the microscopic hardness model. All the parameters are obtained from first-principles calculations. There are two types...rickets hardness calculations of eleven wurtzite-structured semiconductors are performed based on the microscopic hardness model. All the parameters are obtained from first-principles calculations. There are two types of chemical bonds in wurtzite-structured crystals. The overlap populations of the two types of chemical bonds in lonsdaleite are chosen as Pe for wurtzite structure. The calculated bond ionicity values of the wurtzite-structured semiconductors are in good agreement with the ionicities from the dielectric definition. When the hardness of wurtzite-structured crystal is higher than 20 GPa, our calculated rickets hardness is within 10% accuracy. Therefore, the hardness of novel wurtzite-structured crystal could be estimated from first-principles calculations.展开更多
Single phase of Fe^3＋-doped α-Ga2-xFexO3（α-GF x O, x = 0.1, 0.2, 0.3, 0.4） is synthesized by treating the β-Ga2-x Fe x O3（β-GF x O） precursors at high temperatures and high pressures. Rietveld refinements of ...Single phase of Fe^3＋-doped α-Ga2-xFexO3（α-GF x O, x = 0.1, 0.2, 0.3, 0.4） is synthesized by treating the β-Ga2-x Fe x O3（β-GF x O） precursors at high temperatures and high pressures. Rietveld refinements of the X-ray diffraction data show that the lattice constants increase monotonically with the increase of Fe^3＋content. Calorimetric measurements show that the temperature of the phase transition from α-GF x O to β-GF x O increases, while the associated enthalpy change decreases upon increasing Fe^3＋content. The optical energy gap deduced from the reflectance measurement is found to decrease monotonically with the increase in Fe3＋content. From the measurements of magnetic field-dependent magnetization and temperature-dependent inverse molar susceptibility, we find that the superexchange interaction between Fe^3＋ions is antiferromagnetic. Remnant magnetization is observed in the Fe^3＋-doped α-GF x O and is attributed to the spin glass in the magnetic sublattice. At high Fe^3＋doping level（x = 0.4）, two evident peaks are observed in the image part of the AC susceptibility χ ac. The frequency dependence in intensity of these two peaks as well as two spin freezing temperatures observed in the DC magnetization measurements of α-GF0.4O is suggested to be the behavior of two spin glasses.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 50225207, 10325417, 50372055, 50472051 and 50532020, and the National Basic Research Programme of China under Grant No 2005CB724400.
基金Supported by the National Natural Science Foundation of China under Grant Nos 50225207, 10325417, 50372055, 50472051 and 50532020, and the National Basic Research Programme of China under Grant No 2005CB724400.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51732010 and 51972280)the Natural Science Foundation of Hebei Province,China(Grant No.E2019203233)the Research Program of the College Science&Technology of Hebei Province,China(Grant No.ZD2020121).
文摘Thin films of millimeter-scale continuous monolayer WS_(2) have been grown on SiO_(2)/Si substrate,followed by the deposition ofβ-In_(2)Se_(3) crystals on monolayer WS2 to prepare In_(2)Se_(3)/WS_(2) van deWaals heterostructures by a two-step chemical vapor deposition(CVD)method.After the growth of In_(2)Se_(3) at elevated temperatures,high densities of In_(2)Se_(3)/WS_(2) heterostructure bubbles with monolayer to multilayerβ-In_(2)Se_(3) crystals atop are observed.Fluorescence of the resultantβ-In_(2)Se_(3)/WS_(2) heterostructure is greatly enhanced in intensity upon the formation of bubbles,which are evidenced by the Newton’s rings in optical image owing to constructive and destructive interference.In photoluminescence(PL)mapping images of monolayerβ-In_(2)Se_(3)/monolayer WS2 heterobilayer bubble,significant oscillatory behavior of emission intensity is demonstrated due to constructive and destructive interference.However,oscillatory behaviors of peak position are also observed and come from a local heating effect induced by an excitation laser beam.The oscillatory mechanism of PL is further verified by changing the exterior pressure of bubbles placed in a home-made vacuum chamber.In addition,redshifted in peak position and broadening in peak width are observed due to strain effect during decreasing the exterior pressure of bubbles.
基金Supported by the National Natural Science Foundation of China under Grant Nos 50532020 and 50672081, the National Basic Research Programme of China under Grant No 2005CB724400, and the Science Foundation of Yanshan University for the Excellent PhD Students.
文摘rickets hardness calculations of eleven wurtzite-structured semiconductors are performed based on the microscopic hardness model. All the parameters are obtained from first-principles calculations. There are two types of chemical bonds in wurtzite-structured crystals. The overlap populations of the two types of chemical bonds in lonsdaleite are chosen as Pe for wurtzite structure. The calculated bond ionicity values of the wurtzite-structured semiconductors are in good agreement with the ionicities from the dielectric definition. When the hardness of wurtzite-structured crystal is higher than 20 GPa, our calculated rickets hardness is within 10% accuracy. Therefore, the hardness of novel wurtzite-structured crystal could be estimated from first-principles calculations.
基金supported by the National Basic Research Program of China(Grant No.2010CB731605)the National Science Fund for Distinguished Young Scholars of China(Grant No.51025103)+3 种基金the National Natural Science Foundation of China(Grant Nos.51172198 and 51102206)the Natural Science Foundation of Hebei Province,China(Grant No.E2014203144)the Science Foundation for the Excellent Youth Scholars from Universities and Colleges of Hebei Province,China(Grant No.YQ2014009)the Research Program of the College Science&Technology of Hebei Province,China(Grant No.QN2014047)
文摘Single phase of Fe^3＋-doped α-Ga2-xFexO3（α-GF x O, x = 0.1, 0.2, 0.3, 0.4） is synthesized by treating the β-Ga2-x Fe x O3（β-GF x O） precursors at high temperatures and high pressures. Rietveld refinements of the X-ray diffraction data show that the lattice constants increase monotonically with the increase of Fe^3＋content. Calorimetric measurements show that the temperature of the phase transition from α-GF x O to β-GF x O increases, while the associated enthalpy change decreases upon increasing Fe^3＋content. The optical energy gap deduced from the reflectance measurement is found to decrease monotonically with the increase in Fe3＋content. From the measurements of magnetic field-dependent magnetization and temperature-dependent inverse molar susceptibility, we find that the superexchange interaction between Fe^3＋ions is antiferromagnetic. Remnant magnetization is observed in the Fe^3＋-doped α-GF x O and is attributed to the spin glass in the magnetic sublattice. At high Fe^3＋doping level（x = 0.4）, two evident peaks are observed in the image part of the AC susceptibility χ ac. The frequency dependence in intensity of these two peaks as well as two spin freezing temperatures observed in the DC magnetization measurements of α-GF0.4O is suggested to be the behavior of two spin glasses.
基金supported by the National Natural Science Foundation of China (51571172,51672240,51571171,and 11404280)the Natural Science Foundation for Distinguished Young Scholars of Hebei Province (E2017203095)+1 种基金the Natural Science Foundation of Hebei Province (E2016203484 and A2015203337)the Research Program of the College Science & Technology of Hebei Province (ZD2017083 and QN2014047)
基金supported by the National Natural Science Foundation of China(51421091,51332005,51572225,51272227, 51172197,51525205 and 51672239)the US National Science Foundation(EAR-1361276)
