Electric-field tuning of the valley splitting in silicon corner dots

AbstractValleytronics is receiving extensive research efforts. Thus, we investigated the electric field-induced valley polarization in the WSe2/CrSnSe3 heterostructures by varying the stacking order. The heterostructure shows indirect band gaps of 270 and 330 meV in the two most stable structures. The WSe2/CrSnSe3 heterostructure displays a ferromagnetic ground state with out-of-plane anisotropy (0.02 meV) in one stable stacking (S-1) while a small in-plane anisotropy (−0.01 meV) is found in other stacking (S-2). The Curie temperature is slightly enhanced to 73 K compared to the monolayer CrSnSe3. We have found the valley splitting of 4 meV in S-1 whereas it became 9 meV in the S-2 system. The valley splitting is further enhanced if an electric field is applied from CrSnSe3 to the WSe2 layer whereas it is suppressed in the reversed electric field. Particularly, the S-2 structure shows a giant valley splitting of 67 meV at an electric field of 0.6 V Å−1. We attribute this electric field-dependency to the dipolar effect. Overall, we propose that the WSe2/CrSnSe3 heterostructure can be a potential structure for obtaining a giant valley splitting.

Download Full-text

Anisotropic refraction and valley-spin-dependent anomalous Klein tunneling in an 1T′-MoS2-based p-n junction

Chinese Physics B ◽

10.1088/1674-1056/ac46bf ◽

2021 ◽

Author(s):

Fenghua Qi ◽

Xingfei Zhou

Keyword(s):

Electron Beam ◽

Band Structure ◽

Electric Field ◽

Transport Properties ◽

Incident Angle ◽

External Fields ◽

Valley Splitting ◽

Klein Tunneling ◽

Vertical Electric Field ◽

New Type

Abstract We investigate the transport properties of electron in an 1T′-MoS2-based p-n junction. The anisotropic refraction of electron is found when the electron beam crosses the p-n junction, which brings the phenomenon of valley splitting without any external fields. Besides, the valley-spin-dependent anomalous Klein tunneling, i.e., the perfect transmission exists at a nonzero incident angle of valley-spin-dependent electron, happens when the vertical electric field is equal to the critical electric field. These two peculiar properties arise from the same reason that the tilted band structure makes the directions of wavevector and velocity different. Our work designs a special valley splitter without any external fields and finds a new type of Klein tunneling.

Download Full-text

Resolution in photoelectron microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100086593 ◽

1991 ◽

Vol 49 ◽

pp. 458-459

Author(s):

G. F. Rempfer

Keyword(s):

Electron Microscopy ◽

Electric Field ◽

Ultraviolet Light ◽

Uniform Field ◽

Virtual Image ◽

Lens System ◽

Photoemission Electron Microscopy ◽

Planar Electrode ◽

Electron Lens ◽

Photoemission Electron

In photoelectron microscopy (PEM), also called photoemission electron microscopy (PEEM), the image is formed by electrons which have been liberated from the specimen by ultraviolet light. The electrons are accelerated by an electric field before being imaged by an electron lens system. The specimen is supported on a planar electrode (or the electrode itself may be the specimen), and the accelerating field is applied between the specimen, which serves as the cathode, and an anode. The accelerating field is essentially uniform except for microfields near the surface of the specimen and a diverging field near the anode aperture. The uniform field forms a virtual image of the specimen (virtual specimen) at unit lateral magnification, approximately twice as far from the anode as is the specimen. The diverging field at the anode aperture in turn forms a virtual image of the virtual specimen at magnification 2/3, at a distance from the anode of 4/3 the specimen distance. This demagnified virtual image is the object for the objective stage of the lens system.

Download Full-text

Field-assisted ionization theory for microscopists

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100171833 ◽

1994 ◽

Vol 52 ◽

pp. 820-821

Author(s):

Patrick P. Camus

Keyword(s):

Electric Field ◽

Electron Tunneling ◽

Ionization Probability ◽

Critical Distance ◽

Tunneling Probability ◽

Field Ionization ◽

Radius Of Curvature ◽

Field Evaporation ◽

A Value ◽

Ion Emission

The theory of field ion emission is the study of electron tunneling probability enhanced by the application of a high electric field. At subnanometer distances and kilovolt potentials, the probability of tunneling of electrons increases markedly. Field ionization of gas atoms produce atomic resolution images of the surface of the specimen, while field evaporation of surface atoms sections the specimen. Details of emission theory may be found in monographs.Field ionization (FI) is the phenomena whereby an electric field assists in the ionization of gas atoms via tunneling. The tunneling probability is a maximum at a critical distance above the surface,xc, Fig. 1. Energy is required to ionize the gas atom at xc, I, but at a value reduced by the appliedelectric field, xcFe, while energy is recovered by placing the electron in the specimen, φ. The highest ionization probability occurs for those regions on the specimen that have the highest local electric field. Those atoms which protrude from the average surfacehave the smallest radius of curvature, the highest field and therefore produce the highest ionizationprobability and brightest spots on the imaging screen, Fig. 2. This technique is called field ion microscopy (FIM).

Download Full-text