| 1. |
|
|
| 2. |
- Busto, D., et al.
(författare)
-
Time-frequency representation of autoionization dynamics in helium
- 2018
-
Ingår i: Journal of Physics B-Atomic Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 51:4
-
Tidskriftsartikel (refereegranskat)abstract
- Autoionization, which results from the interference between direct photoionization and photoexcitation to a discrete state decaying to the continuum by configuration interaction, is a well known example of the important role of electron correlation in light-matter interaction. Information on this process can be obtained by studying the spectral, or equivalently, temporal complex amplitude of the ionized electron wave packet. Using an energy-resolved interferometric technique, we measure the spectral amplitude and phase of autoionized wave packets emitted via the sp2+ and sp3(+) resonances in helium. These measurements allow us to reconstruct the corresponding temporal profiles by Fourier transform. In addition, applying various time-frequency representations, we observe the build-up of the wave packets in the continuum, monitor the instantaneous frequencies emitted at any time and disentangle the dynamics of the direct and resonant ionization channels.
|
|
| 3. |
- Igalson, M., et al.
(författare)
-
Concentration of defects responsible for persistent photoconductivity in Cu (In,Ga)Se-2 : Dependence on material composition
- 2019
-
Ingår i: Thin Solid Films. - : ELSEVIER SCIENCE SA. - 0040-6090 .- 1879-2731. ; 669, s. 600-604
-
Tidskriftsartikel (refereegranskat)abstract
- Persistent photoconductivity (PPC) in thin Cu(In,Ga)Se-2 films is discussed within a model of relaxing defects acting as donors or acceptors depending on their configurational and charge state. The aim of this work is to identify the factors related to technological processes which affect the magnitude of PPC. We established a method of evaluation of the concentration of metastable defects in thin Cu(In,Ga)Se-2 films relating it to the position of the Fermi level in thermodynamic equilibrium and used it to compare and discuss the impact of preparation details on the PPC value. The main result is that deviation from Cu/(Ga + In) stoichiometry does not change the concentration of metastable defects. Post deposition annealing in selenium affects the PPC depending on the presence of sodium during the treatment, while the impact of sodium itself on the metastable defect concentration apparently depends on whether it is present during the Cu(In,Ga)Se-2 deposition process or whether it is supplied during post-deposition treatment.
|
|
| 4. |
- Igalson, M., et al.
(författare)
-
Excitation spectra of defect levels derived from photoinduced current transient spectroscopy - a tool for studying deep levels in Cu(In,Ga)Se2 compounds
- 2017
-
Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 633:SI, s. 227-230
-
Tidskriftsartikel (refereegranskat)abstract
- Energy required for the optical excitation of carriers onto defect levels is a parameter that compliments thermal activation energy and helps to understand the electronic properties of defects under study. Here a modification of the photoinduced current transient spectroscopy (PICTS) based on phase-sensitive detection is proposed which makes possible to measure the excitation spectra of defect levels. The representative results of the excitation spectra of the epitaxial CuGaSe2 and polycrystalline Cu(In,Ga)Se2 thin films are presented. They illustrate the usefulness of the method as a tool for studying defect properties by providing data that supplement information derived from standard PICTS spectroscopy.
|
|
| 5. |
- Urbaniak, A., et al.
(författare)
-
Signatures of extended defects in Cu(In,Ga)Se-2 observed using capacitance spectroscopy techniques
- 2019
-
Ingår i: Journal of Physics and Chemistry of Solids. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0022-3697 .- 1879-2553. ; 134, s. 58-63
-
Tidskriftsartikel (refereegranskat)abstract
- This work concerns the interpretation of defect spectroscopy signals in CuInSe2-and Cu(In,Ga)Se-2-based Schottky junctions and thin films, which are investigated using capacitance- and current-based techniques. Two common signals are distinguished. It is shown here that the activation energies and consequently the emission rates vary between the samples and are strongly correlated with the hole concentration in the material. Models that can account for these changes are discussed. Based on deep-level transient spectroscopy and conductivity measurements, we present arguments for the validity of the existing models and discuss the hypothesis that the observable signals may originate from extended defects in Cu(In,Ga)Se-2.
|
|
