Optical characteristic and gap states distribution of amorphous SnO_2:(Zn,In) film

In this paper the fabrication technique of amorphous SnO2：（Zn, In） film is presented. The transmittance and gap-states distribution of the film are given. The experimental results of gap-states distribution are compared with the calculated results by using the facts of short range order and lattice vacancy defect of the gap states theory. The distribution of gap state has been proved to be discontinuous due to the short-range order of amorphous structure.

Materials Design on the Origin of Gap States in a High-κ/GaAs Interface

Given the demand for constantly scaling micro- electronic devices to ever smaller dimensions, a SiO2 gate dielectric was substituted with a higher dielectric-constant material, Hf（Zr）O2, in order to minimize current leakage through dielectric thin film. However, upon interfacing with high dielectric constant （high-κ） dielectrics, the electron mobility in the conventional Si channel degrades due to Coulomb scattering, surface-roughness scattering, remotephonon scattering, and dielectric-charge trapping.Ⅲ-Ⅴ and Ge are two promising candidates with superior mobility over Si. Nevertheless, Hf（Zr）O2/Ⅲ-Ⅴ（Ge） has much more complicated interface bonding than Si-based interfaces. Successful fabrication of a high-quality device critically depends on understanding and engineering the bonding configurations at Hf（Zr）O2/Ⅲ-Ⅴ（Ge） interfaces for the optimal design of device interfaces. Thus, an accurate atomic insight into the interface bonding and mechanism of interface gap states formation becomes essential. Here, we utilize first- principle calculations to investigate the interface between HfO2 and GaAs. Our study shows that As--As dimer bonding, Ga partial oxidation （between 3＋ and 1＋） and Ga- dangling bonds constitute the major contributions to gap states. These findings provide insightful guidance for optimum interface passivation.

Gap States of ZnO Thin Films by New Methods:Optical Spectroscopy,Optical Conductivity and Optical Dispersion Energy

The optical reflectance and transmittance spectra in the wavelength range of 300-2500 nm are used to compute the absorption coefficient of zinc oxide films annealed at different post-annealing temperatures 400, 500 and 600°C.The values of the cross point between the curves of the real and imaginary parts of the optical conductivity ɑ_1 and ɑ_1 with energy axis of films exhibit values that correspond to optical gaps and are about 3.25-3.3 eV. The maxima of peaks in plots dR/dλ and dT/dλ versus wavelength of films exhibit optical gaps at about 3.12-3.25 eV.The values of the fundamental indirect band gap obtained from the Tauc model are at about 3.14-3.2 eV. It can be seen that films annealed at 600°C have the minimum indirect optical band gap at about 3.15 eV. The films annealed at 600°C have Urbach＇s energy minimum of 1.38 eV and hence have minimum disorder. The dispersion energy d of films annealed at 500°C has the minimum value of 43 eV.

Radiation-Induced Oscillating Gap States of Nonequilibrium Two-Dimensional Superconductors

We study the effects of infrared radiation on a two-dimensional Bardeen-Cooper-Schrieffer superconductor coupled with a normal metal substrate through a tunneling barrier.The phase transition is analyzed by inspecting the stability of the system against perturbations of pairing potentials.We find an oscillating gap phase with a frequency not directly related to the radiation frequency,but instead resulting from the asymmetry of electron density of states of the system as well as the tunneling amplitude.When such a superconductor is in contact with another superconductor,gives rise to an unusual alternating Josephson current.

Localized electronic states in gaps on hole-net structures of silicon

Hole-net structure silicon is fabricated by laser irradiation and annealing, on which a photoluminescence （PL） band in a the region of 650-750 nm is pinned and its intensity increases obviously after oxidation. It is found that the PL intensity changes with both laser irradiation time and annealing time. Calculations show that some localized states appear in the band gap of the smaller nanocrystal when Silo bonds or Si-O-Si bonds are passivated on the surface. It is discovered that the density and the number of Si=O bonds or Si-O-Si bonds related to both the irradiation time and the annealing time obviously affect the generation of the localized gap states of hole-net silicon, by which the production of stimulated emission through controlling oxidation time can be explained.

Effect of graphene tunnel barrier on Schottky barrier height of Heusler alloy Co_2MnSi/graphene/n-Ge junction

We demonstrate that the insertion of a graphene tunnel barrier between Heusler alloy Co_2MnSi and the germanium（Ge） channel modulates the Schottky barrier height and the resistance–area product of the spin diode. We confirm that the Fermi level is depinned and a reduction in the electron Schottky barrier height（SBH） occurs following the insertion of the graphene layer between Co_2MnSi and Ge. The electron SBH is modulated in the 0.34 eV–0.61 eV range. Furthermore,the transport mechanism changes from rectifying to symmetric tunneling following the insertion. This behavior provides a pathway for highly efficient spin injection from a Heusler alloy into a Ge channel with high electron and hole mobility.

Density Functional Theory Studies on the High-pressure Behavior of Crystalline 5,7-Dinitrobenzo-1,2,3,4-tetrazine-1,3-dioxide

The structural and electronic properties of the solid 5,7-dinitrobenzo-1,2,3,4-tetrazine-1,3-dioxide（DNBTDO） under the hydrostatic pressure of 0~100 GPa were investigated using density functional theory method. The predicted crystal structure with the LDA/CA-PZ functional agrees well with the experimental data at the ambient pressure. The structural results show that the b axis is the most compressible, whereas the a and c axes both have slight variation with pressure. The band gap generally decreases with the increasing pressure, which shows that the DNBTDO molecular crystal undergoes an electronic phase transition from semiconductor to metallic system. Through the analysis of band gap, the title compound is most sensitive at 70 GPa. The density of states analysis indicates that the strong peaks split into some small peaks and become wider under compression, which shows the increase of charge overlap and delocalization among the bonded atoms in the system.