Energy Band Structure Parameters Research Articles

Nanodimensional CoSiO Films Obtained by Ion Implantation on a CoSi2 Surface

The morphology, composition, and electronic properties of CoSiO films formed on a CoSi2/Si(111) substrate surface by $${\text{O}}_{2}^{ + }$$ ion implantation followed by thermal annealing have been studied. Energy band structure parameters are determined, and information on the density of electron states in the valence and conduction bands is obtained. The bandgap width of a CoSiO film is estimated at ~2.4 eV.

A low temperature growth of Ca silicides on Si(100) and Si(111) substrates: Formation, structure, optical properties and energy band structure parameters

The low-temperature formation of Ca silicides on silicon substrates with (100) and (111) orientations and on the oxidized silicon surface during deposition using solid phase epitaxy (SPE) and molecular beam epitaxy (MBE) was studied by the in situ electron spectroscopy. The temperature ranges for the formation of Ca2Si (273–346 °C) and CaSi (554–663 °C) on the Si(100) 2 × 1 surface were established during isochronous annealing of a thin Ca layer (10 nm). It was shown that an amorphous Ca2Si layer was formed by a SPE process at 330 °C from a Ca–Si mixture on the Si(100)2 × 1 surface, but under the surface the silicon and CaSi nanocrystals (NCs) were formed at the interface with the substrate. According to the optical spectroscopy data, films grown by the SPE method are semiconducting with the first direct interband transition at 1.16 eV, but the intraband absorption below 1 eV was determined by the carrier transitions in the CaSi NCs and transitions to defect levels. Raman active and far IR active peaks in amorphous Ca2Si films were firstly determined. When the MBE method (T = 330 °C) with an additional annealing at 330 °C was used, a Ca2Si layer was formed on the film surface, but the main contribution is made by faceted CaSi crystals (100 × 25 nm2) according to AFM, X-ray and electron diffraction. In the film consisting of the Ca2Si and CaSi phases, there are Raman peaks from both phases, which is associated with their separation according to the positions of the Raman shifts. A decrease in the temperature of the MBE process to 190 °C on the Si(111)7 × 7 surface with additional annealing at T = 300 °C leads to the formation of amorphous calcium silicide with a high density of embedded CaSi NCs (3–7 nm) with a stressed structure. When these CaSi NCs films were studied by the Raman spectroscopy method, 8 Raman phonons in the range of 105–422 cm−1 were detected. It was established that films containing CaSi in the crystalline phase are a semimetal with a constant absorption coefficient ((1–2)∙104 cm−1) at photon energies (0.5–1.1 eV) and a quasi-band gap with an energy from 1.26 eV to 1.36 eV depending on the size of CaSi NCs. MBE growth from a mixture of Ca–Si on an oxidized Si(100) surface led to the formation of shapeless CaSi and Ca2Si grains (weak contribution) with sizes from 50 to 200 nm, creating a structural-continuous film.

Model of intrinsic carrier concentrationof [110]/(001)-uniaxial strained Si

In this paper, the effect of uniaxial stress along [110] direction on the energy-band structure parameters of (001)-bulk Si is discussed, thereby we investigate the equilibrium carrier concentration and the expressions of effective density of state (DOS) in conduction and valence band, which contain explicit physical significance. The model of intrinsic carrier concentration is proposed by combining the expressions of DOS and bandgap. The pro- posed method in this paper is also applicable to modeling the intrinsic carrier concentration under the action of uniaxial stress along an arbitrary direction, and provides some references for design, mode- ling and simulation of similar uniaxial strained Si devices.

Evaluating the electronic energy eigenvalues for A2B6 crystals obtained with the GGGA+U functional

AbstractElectronic energy bands of ZnS, ZnSe, and ZnTe crystals evaluated within the mixed basis approach with using the core Bloch states and plane waves. The exchange‐correlation potential has been derived from the new exchange‐correlation‐energy functional including the density gradient corrections and the intra‐atomic Coulomb term U. The calculated energy band structure parameters of the crystals show an improvement compared with the LDA results. The semicore Zn 3d state energies are closer to experimental data than those obtained within the LDA approach. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Energy band structure and electrical properties of (La2O3)1−x(SiO2)x(⩽x⩽1)∕n-GaAs(001) system

This letter investigates the chemical bonding state and energy band structure of (La2O3)1−x(SiO2)x(0⩽x⩽1) films grown on sulfur-passivated n-GaAs (001). The dielectric bandgap and interfacial band alignment were modified by compounding the La2O3 films with SiO2. A shift in binding energy of the core level was observed by comparing the electronegativities of the second nearest-neighbor element. The controlled parameters of energy band structure were systematically monitored by valence band and absorption spectra. Band offset values were almost linearly related to the concentration of SiO2 when no Fermi level pinning in the midgap of n-GaAs was assumed. The correlation between band parameter and electrical properties, as probed by capacitance and leakage current measurements, is discussed.

Controlled band offset in (Gd2O3)1−x(SiO2)x(0⩽x⩽1)∕n–GaAs (001) structure

This letter investigates the chemistry and energy band structure of (Gd2O3)1−x(SiO2)x(0⩽x⩽1) films grown on n-GaAs (001). Dielectric band gap and interfacial band alignment of Gd2O3 films were modified by compounding with SiO2. Binding energy shift of core level was observed from different electronegativity of second nearest-neighbor element. Controlled parameters of energy band structure were systematically characterized by valence band, absorption, and energy loss spectra. Assuming no Fermi level pinning in the midgap of n-GaAs, band offset values represent almost linear dependency on the concentration of SiO2. The correlation of band offset with the electrical properties, as probed by capacitance and leakage current measurements, was also discussed.

Energy band structure parameters and their data, derived from the measurements of minority carrier current density in heavily doped emitters of silicon devices

In the n(p)-type heavily doped emitter region (HDER) of silicon devices, at room temperature, we have investigated the minority-carrier lifetime and the energy band structure parameters such as band-gap narrowing, apparent band-gap narrowing, unperturbed Fermi energy shift, optical gap, and reduced interacting density-of-majority conduction (valence) band states effective mass. As used in our previous paper, the present treatment is also based on the two assumptions for minority-carrier transport parameters. Gaussian impurity density profile, and accurate expression for minority-carrier mobility. Our empirical models for minority-carrier lifetime and band-gap narrowing are proposed and determined such that their curves versus the impurity concentration lie in between 3heir existing experimental data. Then, from a conjunction between electrical and optical phenomena, it is found that our theoretical values of such the energy band structure parameters are in good accordance with our own corresponding data, derived from the measurements of minority-carrier saturation current density in the n(p)-type HDER of silicon devices.

The Energy Band Structure of the Corundum (0001) Surface with Different Extent of Hydroxylation

AbstractA theoretical study of the energy band structure is made for corundum (α‐Al2O3) (0001) surface within the frameworkof the crystalline orbital method. From the results, the dispersion dependences of the electronic energy in chosen directions of the surface Brillouinzone are obtained. For the Al atoms sp‐ and spd‐orbitals are considered to evaluate the effect of an appropriate basis on the results. The dependence of the energy band structure parameters on the extent of the surface hydroxylation is established. A comparison of the theoretical data with experimental ones is made.