Thin film growth and band lineup of In2O3 on the layered semiconductor InSe

Thin films of the transparent conducting oxide In2O3 have been prepared in ultrahigh vacuum by reactive evaporation of indium. X-ray diffraction, optical, and electrical measurements were used to characterize properties of films deposited on transparent insulating mica substrates under variation of the oxygen pressure. Photoelectron spectroscopy was used to investigate in situ the interface formation between In2O3 and the layered semiconductor InSe. For thick In2O3 films a work function of φ = 4.3 eV and a surface Fermi level position of EF−EV = 3.0 eV is determined, giving an ionization potential IP = 7.3 eV and an electron affinity χ = 3.7 eV. The interface exhibits a type I band alignment with ΔEV = 2.05 eV, ΔEC = 0.29 eV, and an interface dipole of δ = −0.55 [email protected]

Strong optical nonlinearities in gallium and indium selenides related to inter-valence-band transitions induced by light pulses

A nonlinear optical effect is shown to occur in gallium and indium selenides at photon energies of the order of 1.5 eV. It corresponds to transitions from a lower-energy valence band to the uppermost one when a nonequilibrium degenerate hole gas is created in the latter by a laser pulse. This inter-valence-band transition is allowed by crystal symmetry. Its oscillator strength is estimated through the f-sum rule and turns out to be about two orders of magnitude higher than that of the fundamental transition. The intensity of this effect is stronger when the pump pulse photon energy is close to that of the inter-valence-band transition; a condition that can be fulfilled only in indium selenide. The transient behavior of the sample transmittance is shown to be controlled by the balance between absorption and stimulated emission, which depends on the hole quasi-Fermi level and the gap renormalization due to Coulomb interaction in the electron-hole gas generated by the pump

Investigation of nitrogen-related acceptor centers in indium selenide by means of photoluminescence: Determination of the hole effective mass

In this work we report on steady-state and time-resolved photoluminescence (PL) measurements in nitrogen doped p-type indium selenide in the 33-210-K temperature range. In samples with low nitrogen concentration the photoluminescence spectrum consists of exciton-related peaks and a band-to-acceptor recombination peak (2.1-μs lifetime) with LO-phonon replica. An ionization energy of 65.5 meV is proposed for the nitrogenrelated acceptor. A long-lived (18 μs) component, which consists of an asymmetric broadband centered around the acceptor peak, has been also detected by means of time-resolved PL. Samples with a higher nitrogen concentration show a PL spectrum that mainly consists of the asymmetric long-lived broadband that can be associated to a complex center. The asymmetric shape of this band is quantitatively accounted for in the framework of the configuration coordinate model for complex centers. Under the assumption that the nitrogen related acceptor is shallow, the Gerlach-Pollman theory allows an estimate of the hole's effective masses

Peptide metal-organic frameworks under pressure: flexible linkers for cooperative compression

We investigate the structural response of a dense peptide metal-organic framework using in situ powder and single-crystal X-ray diffraction under high-pressures. Crystals of Zn(GlyTyr)2 show a reversible compression by 13% in volume at 4 GPa that is facilitated by the ability of the peptidic linker to act as a flexible string for a cooperative response of the structure to strain. This structural transformation is controlled by changes to the conformation of the peptide, which enables a bond rearrangement in the coordination sphere of the metal and changes to the strength and directionality of the supramolecular interactions specific to the side chain groups in the dipeptide sequence. Compared to other structural transformations in Zn(II) peptide MOFs, this behaviour is not affected by host/guest interactions and relies exclusively on the conformational flexibility of the peptide and its side chain chemistry

Study of the Secondary Electron Yield in Dielectrics Using Equivalent Circuital Models

© 2018 IEEE. Personal use of this material is permitted. Permissíon from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertisíng or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.[EN] Secondary electron emission has an important role on the triggering of the multipactor effect; therefore, its study and characterization are essential in radio-frequency waveguide applications. In this paper, we propose a theoretical model, based on equivalent circuit models, to properly understand charging and discharging processes that occur in dielectric samples under electron irradiation for secondary electron emission characterization. Experimental results obtained for Pt, Si, GaS, and Teflon samples are presented to verify the accuracy of the proposed model. Good agreement between theory and experiments has been found.The authors would like to thank the European High Power Space Materials Laboratory for its contribution-a laboratory funded by the European Regional Development Fund-a way of making Europe. Many thanks to the University of Valencia (Spain) for supporting this research activity with the internal program "Assistance for temporary stays of invited researchers within the framework of the Subprogramme Attraction of Talent 2015".Bañón, D.; Socuellamos, JM.; Mata-Sanz, R.; Mercadé-Morales, L.; Gimeno Martínez, B.; Boria Esbert, VE.; Raboso García-Baquero, D.... (2018). Study of the Secondary Electron Yield in Dielectrics Using Equivalent Circuital Models. IEEE Transactions on Plasma Science. 46(4):859-867. https://doi.org/10.1109/TPS.2018.2809602S85986746

Experimental and Theoretical Study of Bi2O2Se Under Compression

We report a joint experimental and theoretical study of the structural, vibrational, elastic, optical, and electronic properties of the layered high-mobility semiconductor Bi2O2Se at high pressure. A good agreement between experiments and ab initio calculations is observed for the equation of state, the pressure coefficients of the Raman-active modes and the bandgap of the material. In particular, a detailed description of the vibrational properties is provided. Unlike other Sillén-type compounds which undergo a tetragonal to collapsed tetragonal pressure-induced phase transition at relatively low pressures, Bi2O2Se shows a remarkable structural stability up to 30 GPa; however, our results indicate that this compound exhibits considerable electronic changes around 4 GPa, likely related to the progressive shortening and hardening of the long and weak Bi–Se bonds linking the Bi2O2 and Se atomic layers. Variations of the structural, vibrational, and electronic properties induced by these electronic changes are discussed

Electrical and photovoltaic properties of indium‐tin‐oxide/p‐InSe/Au solar cells

Conditions for efficiency improvement and optimization in indium‐tin‐oxide/p‐indium‐selenide solar cells are discussed in this paper. This aim is achieved by using low‐resistivity p‐indium‐selenide and by incorporating a back‐surface‐field contact. This contact is insured by a p‐indium selenide/gold barrier whose rectifying behavior is explained through the complex impurity structure of p‐indium‐selenide. Electrical and photovoltaic properties of the cells are also reported. The efficiency parameters under AM1 simulated conditions have been improved up to 32 mA/cm2 for the short‐circuit current density, 0.58 V for the open‐circuit voltage, and 0.63 for the filling factor. As a result, solar efficiencies larger than 10% in annealed cells and 8% in unannealed ones have been attained. The limitations of these devices are discussed by investigating the dependence of electrical and efficiency parameters in function of photon flux and [email protected] ; [email protected]

Numerical analysis of thermally induced optical nonlinearity in GaSe layered crystal

A numerical approach to studying thermally induced optical nonlinearity in semiconductors is presented. A transient finite difference algorithm is applied to solve the thermal diffusion equation coupled with the nonlinear absorbance-transmittance of Au/GaSe/Au samples with an applied electric field. The presented analysis can deal with any arbitrary axisymmetric dependence of the input power over the sample and external electric field, and provides information about the steady state and transitory effects in the transmittance

Pr3+-doped Y2O3 nanocrystals embedded in Y2O3 thin films as a sandwich-like structure prepared by pulsed laser deposition

Pr3+-doped yttria (Y2O3) nanocrystal layers embedded in between pure yttria thin films were prepared on four different substrates. Pulsed laser deposition was used to fabricate this sandwich-like structure. An exhaustive structural and optical characterization of the initial nanocrystals was performed to study their preservation once incorporated between the deposited thin films. We demonstrate that the prepared Y2O3:Pr3+ nanocrystals can be integrated into the thin films after the pulsed laser deposition process, retaining their original crystal structure and luminescent features regardless of the number of deposition cycles and the nature of the substrate. In this sense, we present a novel method to embed and protect the luminescent material, paving the way for developing future optoelectronic applications.The authors acknowledge financial support from the European Community through a Future and Emerging Technologies (FET) project NCLas (Proposal: 829161)