The electronic properties and the optical absorption of lead iodide (PbI 2 ) have been investigated experimentally by means of optical absorption and spectroscopic ellipsometry, and theoretically by a full-potential linear muffin-tin-orbital method. PbI 2 has been recognized as a very promising detector material with a large technological applicability. Its band-gap energy as a function of temperature has also been measured by optical absorption. The temperature dependence has been fitted by two different relations, and a discussion of these fittings is given.

Articles you may be interested inSize dependent optical properties of Si quantum dots in Si-rich nitride/Si3N4 superlattice synthesized by magnetron sputtering Influence of nanocrystal size on optical properties of Si nanocrystals embedded in Si O 2 synthesized by Si ion implantationThe optical band gap energy and the dielectric functions of n-type 4H-SiC have been investigated experimentally by transmission spectroscopy and spectroscopic ellipsometry and theoretically by an ab initio full-potential linear muffin-tin-orbital method. We present the real and imaginary parts of the dielectric functions, resolved into the transverse and longitudinal photon moment a, and we show that the anisotropy is small in 4H-SiC. The measurements and the calculations fall closely together in a wide range of energies.

The renormalization of the electron g factor by the confining potential in semiconductor nanostructures is considered. A new effective k • p Hamiltonian for the electronic states in III-V semiconductor nanostructures in the presence of an external magnetic field is introduced. The mesoscopic spin-orbit (Rashba type) and Zeeman interactions are taken into account on an equal footing. It is then solved analytically for the electron effective g factor in symmetric quantum wells (g * QW). Comparison with different spin quantum beat measurements in GaAs and InGaAs structures demonstrates the accuracy and utility of the theory. The quantum size effects in g * QW are easily understood and its anisotropy g * QW (i.e., the difference between the in-plane and perpendicular configurations) is shown to be given by a mesoscopic spin-orbit effect having the same origin as the Rashba one.

Control of the Rashba spin-orbit coupling in semiconductor two-dimensional electron gases ͑2DEGs͒ is of fundamental interest to the rapidly evolving semiconductor spintronics and depends on the detailed knowledge of the controversial interface and barrier penetration effects. Based on the 8 ϫ 8 k · p Kane model for the bulk, we propose a spin-dependent variational solution for the conduction subbands of III-V heterojuctions, which reveals analytically the different contributions to the Rashba splitting and its dependency on heterostructure and band parameters as the band offset and effective masses. Perturbation expansions are used to derive renormalized parameters for an effective, simple, and yet accurate one band model. Spin-dependent modified Fang-Howard trial functions, which satisfy the spin-dependent boundary conditions, are then introduced. The subband splitting is given as a function of the variational parameter which is obtained minimizing the total energy of the 2DEG. Our calculations applied to InAlAs/InGaAs heterojunctions, where a near 20% increase in the splitting is observed due to the barrier penetration, are in good agreement with both experiment and exact numerical calculations. Well-known expressions in the limit of a perfect insulating barrier are exactly reproduced. The desired control of the spin-orbit splitting for twodimensional ͑2D͒ electron gases ͑2DEGs͒ in III-V semiconductor heterojunctions, as in the Datta and Das spin transistor, has not been achieved yet. The quantitative agreement between theory and experiment is far from complete. Among different studies, there are in particular long-standing controversies concerning the barrier and boundary effects, 1,2 as well as regarding the splitting dependence on the electron density and the consistency among the different experimental methods. [3][4][5] In view of the spintronics, semiconductor heterojunctions form a special class of Rashba split 2DEGs. The electrons are confined by a triangular potential and the strength of the Rashba coupling as well as the electron density ͑n s ͒ can be varied with the gate voltage. Different experiments have been quantitatively interpreted with a simple model for the 2DEGs, 6 i.e., H c = ប 2 ͑k x 2 + k y 2 ͒ / 2m ‫ء‬ + ␣ ‫ء‬ · k ϫ e z , where the Rashba coupling parameter derived from Kane model in the infinite barrier approximation 7 is given byHere the band parameters are those of the well material and E is the confining electric field seen by the 2DEG near the interface. The spin splitting at the Fermi level is then given by ␦ =2␣ ‫ء‬ k F . However, this model has some limitations because it does not include nonparabolicity, barrier penetration, and spin-dependent boundary conditions known to lead to sizable corrections. 2,[8][9][10][11][12][13] There is, however, no simple or consensus way to include or calculate these effects which are usually included through numerical integration of multiband models. 2,[8][9][10][11][12] The problems with such numerical calculations are the spurious solutions, ...

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