Hierarchical composites of polyaniline nanorod arrays covalently-grafted on the surfaces of graphene@Fe3O4@C with high microwave absorption performance

In this work, we have investigated the effect of impurity position on optical properties of a pyramid and a cone like quantum dot For this goal, we first obtain the energy levels and wave functions using finite element method (FEM) in the presence of impurity Then, we have studied the influence of impurity location on refractive index changes and absorption coefficients of the two quantum dots We found that there is a maximum value for total refractive index changes and absorption coefficients at a special impurity position Also, we have found that the refractive index changes and absorption coefficients of a cone like quantum dot are greater than a pyramid quantum dot in same volume and height According to the results, it is deduced that the impurity location plays an important and considerable role in the electronic and optical properties of a pyramid and a cone like quantum dot

Impurity position effect on optical properties of various quantum dots

We have studied the behavior of the binding energy and photoionization cross-section of a donor-impurity in cylindrical-shape GaAs-Ga0.7Al0.3As quantum dots, under the effects of hydrostatic pressure and in-growth direction applied electric and magnetic fields. We have used the variational method under the effective mass and parabolic band approximations. Parallel and perpendicular polarizations of the incident radiation and several values of the quantum dot geometry have also been considered. Our results show that the photoionization cross-section growths as the hydrostatic pressure is increased. For parallel polarization of the incident radiation, the photoionization cross-section decreases when the impurity is shifted from the center of the dot. In the case of perpendicular polarization of the incident radiation, the photoionization cross-section increases when the impurity is shifted in the radial direction of the dot. For on-axis impurities the transitions between the ground state of the impurity and the ground state of the quantum dot are forbidden. In the low pressure regime (less than 13.5 kbar) the impurity binding energy growths linearly with pressure, and in the high pressure regime (higher than 13.5 kbar) the binding energy growths up to a maximum and then decreases. Additionally, we have found that the applied electric and magnetic fields may favor the increase or decrease in binding energy, depending on the impurity position.

Donor-impurity related binding energy and photoinization cross-section in quantum dots: electric and magnetic fields and hydrostatic pressure effects

The combined effects of hydrostatic pressure and temperature on donor impurity binding energy in cylindrical GaAs/Ga07Al03As quantum wire in the presence of the magnetic field have been studied by using a variational technique within the effective-mass approximation The results show that an increment in temperature results in a decrement in donor impurity binding energy while an increment in the pressure for the same temperature enhances the binding energy and the pressure effects on donor binding energy are lower than those due to the magnetic field

The hydrostatic pressure and temperature effects on donor impurities in cylindrical quantum wire under the magnetic field

The effects of the hydrostatic pressure and temperature on binding energy and optical properties of a donor impurity in a spherical quantum dot under external electric field

The multilayered spherical quantum dot under a magnetic field

The binding energy of a hydrogenic impurity of a multilayered spherical GaAs-(Ga,Al)As quantum dot has been investigated as a function of the barrier thickness and the inner dot thickness for various barrier potentials in the effect of the band non-parabolicity. Within the effective mass approximation, the ground state energy has been calculated using the fourth-order Runge–Kutta method. The ground state binding energy of hydrogenic impurity located at the center of a quantum dot has been studied with a variational approach. We have found that a variation in the binding energy has depended on the geometry of the dot.

The binding energy of hydrogenic impurity in multilayered spherical quantum dot

Electric field effect on the binding energy of a hydrogenic impurity in coaxial GaAs/Al xGa1 − x As quantum well-wires

The effect of both an electric and magnetic field on the hydrogenic binding energy of a shallow donor impurity in a coaxial GaAs-(Ga, Al)As quantum well wire (QWW) has been investigated as a function of the impurity position and barrier thicknesses for different values of the applied magnetic and electric field strengths. Within the effective mass approximation, the ground-state energy in the presence of a uniform magnetic field applied parallel to the wire axis has been calculated using the fourth-order Runge–Kutta method. The ground state binding energy under applied electric field has been studied with a variational approach. The two sharp increase in the binding energy have observed for the donor impurity located at outside of the center under the critical electric and magnetic field values. However, for the electric field off the binding energy monotonously decrease with increasing magnetic field strength up to a critical magnetic field and then a sharp decrease is seen before reaching a constant value. For the impurity located at the center, the abrupt deviations of the binding energy strongly depend not only on the electronic confinement, but also on the electric and magnetic field strength. We expect that these results will be useful in technological applications.

S. Aktas

Papers

The multilayered spherical quantum dot under a magnetic field

The binding energy of hydrogenic impurity in multilayered spherical quantum dot

Electric field effect on the binding energy of a hydrogenic impurity in coaxial GaAs/Al xGa1 − x As quantum well-wires

Electric and magnetic field effects on the binding energy of a hydrogenic donor impurity in a coaxial quantum well wire

Geometric effects on energy states of a hydrogenic impurity in multilayered spherical quantum dot