B. Gruzza

Modelization and characterization of Au/InSb/InP Schottky systems as a function of temperature

This work attempts to characterize the Au/InP Schottky diode at different temperatures (in the range 300–425 K). The InP surface is restructured with an InSb thin film with several monolayers. I(V) analysis versus different temperatures gives the saturation current variation Is (2×10−5–7×10−5 A), the mean ideality factor (1.7–1.24), the barrier height (0.47–0.45 V), and finally the serial resistance Rs variations (85–19 Ω). The doping concentration Nd and the diffusion voltage Vd are calculated using the C(V) characteristics. The concentration Nd is 3×1015 cm−3 at room temperature and increases with thermal activation to 7×1015 cm−3 at 425 K. Nevertheless, the diffusion voltage Vd is reversibly proportional to the doping concentration Nd and decreases from 33.7×10−2 to 29×10−2 V. The mean interfacial state density Nss decreases with increasing temperature, from 4.33×1012 to 1012 cm−2.eV−1. This improvement is the result of molecular restructuring and reordering at the Au/InP interface. For temperatures less than 375 K, the C(V) characteristic is controlled by an important interfacial state density and/or the presence of deep donor levels in the semiconductor bulk. At temperatures greater than 375 K, the C−2(V) curve is linear and the deep donor levels disappear. The traps effect is also reduced.

Stranski-Krastanov growth mode of Au ON Mo(llO) surface: Investigation by Auger electron spectroscopy

Abstract This paper is a continuation of the gold condensation on Mo(110) study, in which we pointed out the influence of temperature deposition T s on the first stages of growth. The aim of the present work is to study correlations between temperature and growth mode for 293 T s T s T s T s T s > 1223 K: The sticking coefficient is lower than unity and one monolayer condense after a very long time.

Some aspects of AES, EELS and EPES application: Interpretation of experimental results obtained on InP(100) surfaces

Abstract This paper is devoted to the interpretation of the results obtained by AES, EPES and EELS on InP(100). Accurate characterizations of the preparation of the substrates are given, particularly their contribution to the growth of In crystallites on the surface during the Ar + bombardment.

A study by elastically reflected electrons of InP(100) substrates previously ion bombarded

The current Ie of elastically reflected electrons on (100) InP substrates was determined by measuring the spectral distribution and the current transmitted by the optical system. A method allowing one to calculate the current of electrons Ie, elastically reflected by a stacking of alternating A and B monolayers ended by a mixed monolayer, is developed. The method is applied to clean and stable InP(100) surfaces previously studied by Auger electron spectroscopy. The correlation between the results obtained by these two techniques performed on samples chemically cleaned both bombarded with Ar+ ions at low energy and room temperature, allows one to consider the stacking model (0.75 In+0.25 P)/P/In/P as the most reliable.

AES and EELS study of alumina model catalyst supports

Stoichiometry of alumina surface can influence the catalytic properties of alumina supported catalysts. Different types of the (0001) α-alumina surface were prepared by thermal treatment under atmosphere or vacuum and by ion sputtering. Heating under vacuum and ion sputtering lead to the formation of an aluminium rich surface layer. This is observed via an excitation of the Al surface plasmon and an increase of the Al/O Auger intensity ratio. Heating of the alumina crystal under air gives well stoichiometric oxide surface. But γ-alumina layer prepared by thermal heating of aluminium under air exhibits a lack of oxygen without formation of an Al rich surface film.

Analysis and simulation of Au/InSb/InP diode C–V characteristic: modeling and experiments

Abstract The effects of the energy density distribution and relaxation time of the interface state on electric parameters of Au/InSb/InP(100) Schottky diodes were investigated, in the latter diode, InSb forms a fine restructuration layer allowing to block P atoms migration to surface. To be sure of the disappearance of the In droplets, a high quantity of Sb was evaporated and the excess was eliminated by heating the substrate surface at 300 °C before evaporating Au onto it. The current–voltage I(VG) and capacitance–voltage C(VG) characteristics are measured as a function of frequency (100 Hz–1 MHz). Typical Ln[I/(1−e−qVG/kT)] versus VG characteristics of Au/heated InSb/InP(100) Schottky diode under forward bias show two linear regions separated by a transition segment. From the first region, the slope and the intercept of this plot on the current axis allow to determine the ideality factor n and the saturation current Is evaluated to 1.79 and 1.64×10−7 A, respectively. The mean density of interface states estimated from the C(VG) measurements was 1.57 1012 cm−2 eV−1. The interface states were responsible for the non-ideal behavior of the I(VG) characteristics, the capture cross-section σn for the fast slow varies between 2.16×10−11 and 7.13×10−12 cm2 for the relaxation times range 7.9×10−3–2.4×10−2s.

Energy dependence of the different electron emissions backscattered from polycrystalline molybdenum

The energy dependence of the emission yield of electrons backscattered from a clean polycrystalline molybdenum sample has been studied using a dispersive hemispherical analyser (incidence angle theta =70 degrees ; collection angle phi =0 degrees ). True secondaries, Auger electrons, elastic peak and background detected in the N(E) mode were investigated. Experimental results related to the elastic scattering of primary electrons are in good agreement with theoretical treatments (simple diffusion model and Monte Carlo simulation of multiple scattering). It is found that elastically reflected electrons mainly arise from single collision processes with a maximum of the emission yield at a primary energy Ep approximately=300 eV. The behaviour of the Mo-MNN Auger signal normalized by the primary current is compared to the energy dependence of the Auger peak/background ratio. These two normalization procedures lead to some differences mainly due to the transfer of the inelastic contribution of the background toward higher kinetic energies when Ep is increased. The dependence on the primary energy of the true secondary emission is closely related to the one recorded for the total backscattered coefficient deduced from the measurements of primary and sample currents. Threshold effects at an energy corresponding to the Mo-3d inner level are hardly detected. Furthermore, a rough estimation of the relative contributions of the different electrons involved in the N(E) backscattered spectra is proposed.

Electrical parameters evolution of Au/InP(100) and Au/InSb/InP(100) systems with restructuring conditions

Abstract The effects of surface preparation and annealing on the electrical parameters of Au/InP and Au/InSb/InP Schottky diodes were investigated; in the latter diode, InSb forms a thin restructuration layer allowing the blockage of In atom migration to the surface. The current–voltage characteristics I – V G of these diodes were measured before and after restructuring. The electrical behavior of the components obtained after creation of Au/InP(100) interfaces before and after annealing of the substrate surface at 300 °C was examined. The analysis of the I – V G curves of Au/InP diodes shows a migration of chemical species towards the interface. The electrical characteristic of this contact is ohmic type when the InP surface is heated at 300 °C, and it is of Schottky type with a poor quality and with a height of the potential barrier equal to 0.44 eV when the InP surface is not heated. On the other hand, the Au/InSb/InP contact presents better electrical quality and structural properties when the InSb/InP surface is heated at 300 °C than when it is not. Thus, in the former case, the contact shows high value, about 0.63 eV, for the height of the potential barrier.

Study of Sb condensation on InP(100) substrates previously cleaned by low energy Ar+ ion beam

Abstract Electron loss spectroscopy (EELS) and AES have been performed in order to investigate a (100) InP surface subjected to a controlled Sb deposition. The InP(100) surface was previously cleaned by Ar + ion bombardment at low energy leading to the removal of the impurities and the formation of some metallic indium. After Sb deposition, EELS reveals a new surface configuration. Heating of such surface decreases the roughness induced by In droplets; Sb appears strongly fixed with θ

Electrons elastically backscattered from Al, Ag and Au samples

The objective of this study is to exhibit the capability of Monte-Carlo simulation in the frame of surface spectroscopy using elastically reflected electrons. Our computer programme is based on sample descriptions as stackings of atomic layers. Results allow us information on important parameters as the penetration depth of the electron beam or angular reflections. The programme has the capability for performing 3 D mapping of the backscattered electrons. Measurements of the percentage of the reflected current are depending on the geometry of the analysis system. This can be shown by the relief of the three dimensional patterns.