ABSTRACT
The fabrication of planar heterojunctions with magnetic van der Waals ultrathin crystals is essential for constructing miniaturized spintronic devices but is yet to be realized. Here, we report the growth of CrTe3 and CrTe2 ultrathin films with molecular beam epitaxy and characterize their morphological and electronic structure through low-temperature scanning tunneling microscopy/spectroscopy. The former is identified as a Mott insulator, and the latter has shown a robust magnetic order previously. Through vacuum annealing, CrTe3 can be transformed into CrTe2, whose relative ratio is controlled via the annealing time. This renders the feasibility of constructing CrTe3-CrTe2 planar heterojunctions, which express atomically sharp interfaces and smooth band bending. We also identified a superstructure conceivably formed via hybrid units of CrTe3 and CrTe2, whose electronic structure exhibits stunning tunability with the length of the superstructure. Our study sets a foundation for the development of magnetic tunneling junctions for building spintronic circuits and engineering electronic states in artificial superlattice structures.
ABSTRACT
Objective To observe the deposition of PM2.5 in the contact lens and its influence on the oxygen permeability and refractive index of the contact lens.Methods Atmospheric PM2.5 was collected for preparation of 1 mg · mL-1 PM2.5 suspension.Then,18 rigid gas permeable contact lenses (RGPCL) and 18 soft contact lens lenses (SCL) were grouped in control,experimental and PBS-rinse group,with 6 RGPCL and 6 SCL in each group.RGPCL and SCL in the experimental and PBS-rinse groups were incubated in 1 mg · mL-1 PM2.5 solution for 24 h,followed by PBS-rinse group were further washed for 1 h in PBS,whereas the controls were incubated in PBS for 24 h.All of them were examined with field scanning electron microscopy.Meanwhile,oxygen permeability and refractive index of contact lens were measured using the polar graphic devices and refractometry respectively.All the obtained data were quantitatively and statistically analyzed.Results After treatment in PM2.5 solution,there was a large amount of PM2.5 deposition on the RGPCL surface in the experimental group,and the amount of PM2.5 was counted (3.19 ± 1.64) · 100 μm-2,while no atmospheric particulate matter was found in the control group;following the treatment of PBS,a lot of PM2.5 attached on the surface of RGPCL remained visible,and the number of particles was (5.12 ± 1.27) · 100 μm-2.And the difference was statistically significant between the control group and PBS-rinse group (P ＜0.05).In addition,and the amount of PM2.5 attached on the surface of SCL in the exPerimental group was (2.16 ± 1.19) · 100 μm-2,while there wasn t any atmospheric particulate matter in the control group;and,after a wash of SCL in PBS,the amount of PM2.5 on SCL surface was (0.56 ±0.39) · 100 μm-2 in the PBS-rinse group,indicating a statistically difference between the control group and PBS-rinse group (P ＜0.05).Moreover,the amount of PM2.5 attachment on SCL surface in the experimental group was significantly lower than that of the control group,and the difference was statistically significant (P ＜ 0.05).After PM2.5 solution treatment,oxygen permeability of RGPCL and SCL was 100.00 ± 3.17 and 42.00 ± 2.57 respectively in the experimental group,as well as 100.00 ±2.36 and 41.00 ± 3.44 in the control group,with no statistically significant difference between the two groups (all P ＞ 0.05);while refractive index of RGPCL and SCL was 1.415 6 ±0.000 4 and 1.3737 ±0.000 7 respectively in the experimental group,as well as 1.415 3 ±0.000 4 and 1.373 7 ±0.000 l in the control group,with no statistically significant difference between the two groups either (all P ＞ 0.05).Conclusion PM2.5 can be attached to the surface of RGPCL and SCL,and PM2.5 is easier to adhere to RGPCL surface and is not easy to elute when compared with SCL,but PM2.5 deposition do not affect oxygen permeability and refractive index of contact lenses over a short span of time.
