Illumination dependence of I-V and C-V characterization of Au/InSb/InP(1 0 0) Schottky structure

The effects of surface preparation and illumination on electric parameters of Au/InSb/InP(100) Schottky diode were investigated, in the later diode InSb forms a fine restructuration layer allowing to block In atoms migration to surface. In order to study the electric characteristics under illumination, we make use of an He-Ne laser of 1 mW power and 632.8 nm wavelength. The current-voltage I(V_G), the capacitance-voltage C(V_G) measurements were plotted and analysed. The saturation current I_s, the serial resistance R_s and the mean ideality factor n are, respectively, equal to 2.03 × 10⁻⁵ A, 85 Ω, 1.7 under dark and to 3.97 × 10⁻⁵ A, 67 Ω, 1.59 under illumination. The analysis of I(V_G) and C(V_G) characteristics allows us to determine the mean interfacial state density N_ss and the transmission coefficient θ_n equal, respectively, to 4.33 × 10¹² eV⁻¹ cm⁻², 4.08 × 10⁻³ under dark and 3.79 × 10¹² eV⁻¹ cm⁻² and 5.65 × 10⁻³ under illumination. The deep discrete donor levels presence in the semiconductor bulk under dark and under illumination are responsible for the non-linearity of the C⁻²(V_G) characteristic.     

XPS, electric and photoluminescence-based analysis of the GaAs (1 0 0) nitridation

In this paper, nitridation process of GaAs (1 0 0) substrates was studied in-situ using X-ray photoelectron spectroscopy (XPS) and ex-situ by means of electrical method I-V and photoluminescence surface state spectroscopy (PLS³) in order to determine chemical, electrical and electronic properties of the elaborated GaN/GaAs interfaces.The elaborated structures were characterised by I-V analysis. The saturation current I_S, the ideality factor n, the barrier height Φ_Bn and the serial resistance R_S are determined.The elaborated GaN/GaAs structures are also exhibited a high PL intensity at room temperature. From the computer-aided analysis of the power-dependent PL efficiency measurements (PLS³ technique), the value of the interface state density N_SS(E) close to the mid-gap was estimated to be in the range of 2-4 × 10¹¹ eV⁻¹ cm⁻², indicating a good electronic quality of the obtained interfaces.Correlation among chemical, electronic and electrical properties of the GaN/GaAs interface was discussed.     

Probe metal binding mode of imine covalent organic frameworks: cycloiridation for (photo)catalytic hydrogen evolution from formate

Metalation of covalent organic frameworks (COFs) is a critical strategy to functionalize COFs for advanced applications yet largely relies on the pre-installed specific metal docking sites in the network, such as porphyrin, salen, 2,2′-bipyridine, etc. We show in this study that the imine linkage of simple imine-based COFs, one of the most popular COFs, readily chelate transition metal (Ir in this work) via cyclometalation, which has not been explored before. The iridacycle decorated COF exhibited more than 10-fold efficiency enhancement in (photo)catalytic hydrogen evolution from aqueous formate solution than its molecular counterpart under mild conditions. This work will inspire more functional cyclometallated COFs to be explored beyond catalysis considering the large imine COF library and the rich metallacycle chemistry.

This study describes cyclometallation as a new metal binding mode for imine-based COFs. The iridacycle decorated COF could be used for catalytic hydrogen evolution from aqueous formate solution with high stability and high efficacy.     

Resolvent Tests for Similarity to a Normal Operator

The main result of this paper is the resolvent similarity criterionwhich says that linear growth of the resolvent towards the spectrumis sufficient for a Hilbert space contraction with finite rankdefect operators and spectrum not covering the unit disc tobe similar to a normal operator. Similar results are provedfor operators having a spectral set bounded by a Dini-smoothJordan curve; in particular, a dissipative operator with finiterank imaginary part is similar to a normal operator if and onlyif its resolvent grows linearly towards the spectrum. Relevantresults on the insufficiency of linear resolvent growth notaccompanied by smallness of defect operators are presented.Also it is proved that there is no restriction on the spectrum,other than finiteness, which together with linear resolventgrowth implies similarity to a normal operator. The constructionof corresponding examples depends on a characterization of well-knownAhlfors curves as curves of linear length growth with respectto linear fractional transformations. 1991 Mathematics SubjectClassification: 11D25, 11G05, 14G05.     

First stages of surface steel nitriding: X-ray photoelectron spectroscopy and electrical measurements

Quantitative and qualitative analysis techniques were employed to study the first stages of ultra-high vacuum plasma nitriding of the 42CrMo4 steel. At constant treatment temperature, maintained for all samples at about 360 °C, we have established the influence of treatment time on the chemical composition, thickness and electrical properties of the nitrided layer.In this purpose it was used a stacking atomic layer model describing the sample surface, which takes into account the attenuation depth of photoelectrons by the atomic monolayers. So, we have found that after 2 h of nitriding in laboratory conditions, 70% of the nitrided layer was composed of iron oxide. Also, I–V measurements indicate an influence of the nitride overlayer with increasing treatment time.     

Numerical simulation of solar cells based on III–V nitride compounds

In this paper, we developed a numerical calculation program, using Turbo Pascal, to determine the current–voltage characteristics of a $\hbox {N}^{+}\hbox {P}$ solar cells in order to find the main parameters influencing the conversion efficiency. We adopted a one-dimensional numerical model for the resolution of the three semiconductor equations, which are: the Poisson’s equation and the two continuity equations of electrons and holes. Our system of equations is written in term of $\varphi ,\, \varphi _{n}$ , and $\varphi _{p}$ , and it’s resolved using the finite difference method. This code enables us to draw the current density versus the voltage for different layer thicknesses, the conversion efficiency versus the minority carrier life time and the spectral response versus the wavelength. In order to compare the conversion efficiency of two different solar cells, we simulated a solar cell based on III–V nitride compounds $(\hbox {In}_\mathrm{x}\hbox {Ga}_{1-\mathrm{x}}\hbox {N})$ and a monocrystalline silicon solar cell.     

Simulation and electrical characterization of InN/InP diodes

ABSTRACT

Fabrication and electrical characterization of thin films obtained by the nitridation of InP (100) substrates in a Glow Discharge Source (GDS) are presented and discussed. The electrical parameters of InN/InP Schottky diode such as the saturation current (I_s), barrier height (φ_b), ideality factor (n) and series resistance (R_s) were determined. These parameters were calculated using the current-voltage (I–V) characteristics and are compared with those obtained by an analytical model. This model was used in order to identify the transport phenomena. Semi-log forward I-V, Cheung functions and Norde methods were used in order to determine the series resistance R_s. The measured values of I_s, (φ_b), and n for the studied sample are of 1.33 × 10^?4 A cm^?2, 0.46 eV and 3.31, respectively.     

Study of the surface state density and potential in MIS diode Schottky using the surface photovoltage method

ABSTRACT

The effects of surface preparation and illumination on electric parameters of Au/GaN/GaAs Schottky diode were investigated. The thin GaN film is realized by nitridation of GaAs substrates with different thicknesses of GaN layers (0.7 – 2.2 nm). In order to study the electrical characteristics under illumination, we use an He-Ne laser of 632 nm wavelength. The I(V) current- voltage, the surface photovltage SPV measurement were plotted and analysed taking into consideration the influence of charge exchange between a continuum of the surface states and the semiconductor. The barrier height Ф_Bn, the serial resistance R_s and the ideality factor n are respectively equal to 0.66 eV, 1980 Ω, 2.75 under dark and to 0.65 eV, 1160 Ω, 2.74 under illumination for simple 1 (GaN theckness of 0.7 nm). The interface states density N_ss in the gap and the excess of concentration δn are determined by fitting the experimental curves of the surface photovltage SPV with the theoretical ones and are equal to 4.5×10¹² eV^?1 cm^?2, 5×10⁷ cm^?3, respectively, for sample 1 and 3.5×10¹² eV^?1 cm^?2, 7×10⁸ cm^?3 for sample 2 (GaN theckness of 2 nm). The results confirm that the surface photovoltage is an efficient method for optical and electrical characterizations.     

Characterization and comparison between Ig(Vgs) structures HEMT AlInN/GaN and AlGaN/GaN

In this paper, we have studied the Schottky contact of two structures AlInN/GaN and AlGaN/GaN in transistors HEMTs. The current–voltage Igs(Vgs) of AlInN/GaN and AlGaN/GaN structures were investigated at room temperature. The electrical parameters such as ideality factor (2.3 and 1.96), barrier height (0.72 and 0.71 eV) and series resistance (33 and 153 $\Omega $ ) were evaluated from I–V data. The comparison of the performance of the two structures AlInN/GaN and AlGaN/GaN in transistors HEMTs have been analyzed and discussed.     

Magnetic Nanoparticle Thermometry via Controlled Diffusion

The process of magnetic nanoparticle heating releases enormous amounts of thermal energy. Through typical calorimetric analyses, the total thermal energy released can be easily quantified; however, knowledge of nanoscale temperature is necessary. Herein, a novel method of nanoscale thermometry by analyzing intra-particle diffusion in core–shell nanoparticles is proposed. Heating the iron cores with an alternating magnetic field in a saline suspension encourages the diffusion of sodium ions into the silica shells of the particles, which is modeled numerically; however, experimental measurements are needed in order to provide accurate diffusivity estimations. After determining the diffusion characteristics from X-ray photoelectron spectroscopy) depth profiling of silica films, energy dispersive analysis with high-resolution transmission electron microscopy measures the sodium ion gradient within single particles before and after heating. When compared directly to the numerical simulations, the results indicate that the temperature gradient between particles and saline suspension reaches significantly higher temperatures than the macro-scale temperature of the solution. By accurately knowing the thermal gradient between nanoparticles and the surrounding medium, nanoparticles can be engineered to limit surface resistances as much as possible and promote high rates of thermal energy transfer.