J. Guillot

Deliberate and Accidental Gas-Phase Alkali Doping of Chalcogenide Semiconductors: Cu(In,Ga)Se2

Alkali metal doping is essential to achieve highly efficient energy conversion in Cu(In,Ga)Se2 (CIGSe) solar cells. Doping is normally achieved through solid state reactions, but recent observations of gas-phase alkali transport in the kesterite sulfide (Cu2ZnSnS4) system (re)open the way to a novel gas-phase doping strategy. However, the current understanding of gas-phase alkali transport is very limited. This work (i) shows that CIGSe device efficiency can be improved from 2% to 8% by gas-phase sodium incorporation alone, (ii) identifies the most likely routes for gas-phase alkali transport based on mass spectrometric studies, (iii) provides thermochemical computations to rationalize the observations and (iv) critically discusses the subject literature with the aim to better understand the chemical basis of the phenomenon. These results suggest that accidental alkali metal doping occurs all the time, that a controlled vapor pressure of alkali metal could be applied during growth to dope the semiconductor, and that it may have to be accounted for during the currently used solid state doping routes. It is concluded that alkali gas-phase transport occurs through a plurality of routes and cannot be attributed to one single source.

Vector and tensor analyzing powers in the

Cross sections and vector and tensor analyzing powers for the main levels in Pb-207 have been measured via the Pb-208(d over arrow pointing right, t)Pb-207 reaction at 200 and 360 MeV incident energies. A(y) and A(yy) spin observables allow a clear identification of the valence levels, especially at 200 MeV. The results are compared with finite range distorted-wave Born approximation calculations using the Paris projectile-ejectile form factor including the S and D components. The analysis shows a large effect of the D component on the tensor analyzing powers at the most forward angles. At both energies, the spin part of the deuteron optical potential is very important to describe the analyzing powers and especially A(yy). A good description of all observables at 200 MeV allows this reaction to be used as a spectroscopic tool.

^{208}

The reversibility of redox processes is an important function for sensing and molecular electronic devices such as pH reporters or molecular switches. Here we report the electrochemical behaviour and redox reversibility of para-aminothiolphenol (PATP) after different polymerisation methods. We used electrochemical and photo-polymerisation in neutral buffers and plasma polymerisation in air to induce reversible redox states. The chemical stoichiometry and surface coverage of PATP in the polymerized layers were characterized by X-ray photoelectron spectroscopy (XPS), while cyclic voltammetry (CV) was used to measure the charge transfer, double layer capacitance and electrochemical rate of the layers during successive potential cycles. Our results show that the surface coverage of the redox active species is higher on electro-polymerised samples, however, after consecutive cycles all the methods converge to the same charge transfer, while the plasma polymerised samples achieve higher efficiency per molecule and UV polymerised samples have a higher electron transfer rate.

Pb(d.t)

In order to solve the nature of 9He ground state, additional information on this unbound nucleus with extreme N/Z ratio was needed. The present study was performed via the (d,p) reaction, a standard tool for determination of neutron single-particle distribution.

^{207}

We have used the 43 MeV/nucleon primary tritium beam of the AGOR facility with an intensity of 4x10(7) pps and the BBS experimental setup to study the (t,He-3) reaction between 0 degrees and 5 degrees lab angles on C-12, Ca-48, and Ni-58 targets. The standard ray-tracing procedure has allowed us to obtain excitation-energy spectra up to 30 MeV in six angular bins for each residual nucleus, with an average energy resolution of 350 keV. The reaction mechanism has been described in distorted-waves Born approximation (DWBA) using the DWBA98 code. In this approximation, the form factor is treated as a folding of an effective projectile-nucleon interaction with a transition density. The effective projectile-nucleon interaction has been adjusted to reproduce the 0(degrees) cross section of the 1(+) ground state of B-12 populated in the C-12(t,He-3) reaction. We have employed random-phase approximation (RPA) wave functions of excited states to construct the form factor instead of the normal modes wave functions used earlier. This new DWBA+RPA analysis is used to compare calculated and experimental cross sections directly and to discuss the giant resonance excitations in K-48 and Co-58 nuclei.

Pb reaction at 200 and 360 MeV

Proton holes states have been studied up toEx=17 MeV andEx=3.5 MeV in the119In nucleus via the120Sn(d,3He)119In reaction respectively atEd=108.4 MeV andEd=51 MeV. DWBA analysis of angular distributions has allowedl attributions for a large number of new levels and the determination of valence and inner hole strength distributions. The first 1g9/2, 2p1/2 and 2p3/2 levels only exhaust 40%, 60% and 32% of their respective sum rule limits. The missing strengths are shared among several low lying levels and significant higher lying contributions. The 1f strength, not identified in the previous experiments is spread fromEx=1 MeV to about 17 MeV. The low lying levels aroundEx=2.4 MeV could exhaust some 40% of the 1f5/2 sum rule. The higher lying strength with a flat maximum aroundEx=7.5 MeV could account for the 1f7/2inner hole strength and the missing 1f5/2 valence strength. The experimental strength functions compare rather well with the predictions of the quasiparticle-phonon model.