Cathy Guasch

Discontinuous ion tracks on silicon oxide on silicon surfaces after grazing-angle heavy ion irradiation

Thin silicon oxide layers on silicon have been characterized by atomic force microscopy before and after swift heavy ion irradiation with 0.63MeV∕u Pb ions at grazing angle of incidence. In this letter, the authors report the observation of extended intermittent tracks at the silicon oxide (SiO2) surface. As a result, this raises the question of the discontinuous energy deposition at the nanometric scale. This experimental overlook is of major interest for nanostructuring and surface nanoprocessing as well as with regard to reliability of electronic components and systems.

Growth of silicon bump induced by swift heavy ion at the silicon oxide-silicon interface

Thin silicon oxide layers on silicon substrates are investigated by scanning probe microscopy before and after irradiation with 210 MeV Au+ ions. After irradiation and complete chemical etching of the silicon oxide layer, silicon bumps grown on the silicon surface are observed. It is shown that each impinging ion induces one silicon bump at the interface. This observation is consistent with the thermal spike theory. Ion energy loss is transferred to the oxide and induces local melting. Silicon-bump formation is favored when the oxide and oxide-silicon interface are silicon rich.

Effect of indium doping on physical properties of nanocrystallized SnS zinc blend thin films grown by chemical bath deposition

SnS:In thin films have been successfully prepared on Pyrex substrates using low cost chemical bath deposition technique with different indium concentrations (y=[In][Sn]=4%,6%,8%,and10%). The structure, the surface morphology, and the optical properties of the SnS:In films were studied by x-ray diffraction, scanning electron microscope, atomic force microscopy, and spectrophotometer measurements. In order to obtain a thickness of the order of 308 ± 10 nm for potential applications in solar cell devices, a multilayer deposition has been prepared. It is found that the physical properties of tin sulphide are affected by indium concentration. In fact, x-ray diffraction study showed that better crystallinity in zinc blend structure with preferential orientations (111)ZB and (200)ZB was obtained for y equal to 6%. According to the AFM analysis, we remark that low average surface roughness value of SnS(ZB) thin film is obtained with In concentrations equal to y = 6%. Energy dispersive spectroscopy showed the exis...

Synthesis and characterization of Fe-doped SnS thin films by chemical bath deposition technique for solar cells applications

Undoped zinc blend tin sulphide can be used as an absorber material in thin film solar cells. In the present study, SnS thin film has been doped with iron (Fe) at different concentrations (y = [Fe]/[Sn] = 4%, 6%, 8%, 10%). Structural, morphological, chemical, optical, and electrical properties were studied by X-Ray diffraction, scanning electron microscopy associated with energy dispersive spectroscopy, atomic force microscopy, and thermally stimulated current. X-ray diffraction study shows that better crystallinity is obtained for y = 8%. Scanning electron microscopy reveals that the surface morphology of the films strongly depends on the doping concentration. The energy dispersive spectroscopy shows the presence of Fe. The band gap energy is found to be about 1.6 eV. The thermally stimulated current is dominated by the trapping centers. It increases for y = 4% compared to the undoped SnS thin film. The activation energy of trapping centers in undoped and doped SnS thin layers is also calculated.

Effect of Deposition Time on Physical Properties of Nanocrystallized SnS Zinc Blend Thin Films Grown by Chemical Bath Deposition

Abstract. Zinc blend tin sulphide thin films have been successfully prepared on Pyrex substrates using low cost chemical bath depositiontechnique. In this work, we study the effect of time deposition on the physical properties of SnS thin film. A 200 nm thick layer is obtained as an optimum value for deposition time td equal to four hours. X-Ray diffraction study shows that SnS exhibits a zinc blend structure with preferential orientations (111)ZB and (200)ZB. Optical analyses by means of transmission T(λ) and reflection R(λ) measurements allow to determine the direct band gap energy value ≈1.7 eV. Thin layers of tin sulphide exhibit a high absorption coefficient up to 1.5×106 cm-1 in the visible domain, indicating that SnS compound has absorbing properties favorable for applications in solar cell devices.

Effects of gallium doping and thermal annealing on the physical properties of tin sulphide thin films

SnS thin films doped with gallium at different concentrations (0%, 4%, 6%, 8%, and 10%) were grown by the chemical bath deposition technique. The structural analysis confirmed previous results on the formation of a mixed face-centered cubic (rock-salt RS) and orthorhombic (OR) microcrystalline structure with the preferential orientations (111)RS and (200)RS in the undoped layers. This crystal structure was confirmed by Raman spectroscopy: the main vibration at 220 cm−1 corresponding to the face-centered cubic SnS was observed in all samples. Small amounts of Sn2S3 phases were also present. The optimum of thin film crystal structure was obtained with a gallium concentration of 4%. This layer was then annealed in nitrogen gas for 30 min at annealing temperatures ranging from 200 °C to 600 °C. X-ray diffraction analysis revealed a structural transition from RS to OR when the annealing temperature was over 500 °C. The optical bandgap energy declined with increasing annealing temperatures. The resistivity dedu...

Oxide thickness dependence of swift heavy ion-induced surface tracks formation in silicon dioxide on silicon structures at grazing incidence

The influence of the oxide thickness in the surface tracks formation in thin silicon dioxide layered-silicon substrate (SiO2-Si) irradiated with swift heavy ion is dealt with. In this respect, SiO2-Si samples with different oxide thicknesses have been characterized using atomic force microscopy before and after 7.51 MeV/u Xe ion irradiation at a grazing incident angle of 1° relative to the surface plane. Experimental evidence of the existence of a threshold thickness in the formation of swift heavy ion-induced surface tracks has been addressed and discussed according to the thermal spike theory. This experimental upshot can be helpful when assessing metal–oxide–semiconductor ultrathin-gate oxide reliability issues and for growth of silicon-based nanostructures.

Toward a better understanding of the nanoscale degradation mechanisms of ultra-thin Si02/Si films: Investigation of the best experimental conditions with a conductive-atomic force microscope

We report, in this paper, investigations on the experimental conditions to be adopted to improve the reproducibility and the stability of conductive-atomic force microscopy experiments performed on ultra-thin oxide films. In particular, we demonstrate the key role of the water film layer which can disturb the acquisition of ramp voltage stresses and, in fine, lead to an important tip oxidation. Starting from these results, Weibull statistical analyses of stress-induced electrical degradation were carried out under vacuum on SiO2/Si films. We studied the influence of different parameters like the oxide thickness, the substrate doping type and doping level. We also observed important morphological effects, more or less visible, according to the type of tip and the oxide thickness. Those effects can be attributed, on one hand, to different temperature rise at the tip/oxide interface and, on the other hand, to different energy dissipated through the oxide film.

High ionizing dose effects on ultra thin SiO 2 /Si structures revealed by Conductive Atomic Force Microscopy

The electrical stress behavior of high total ionizing dose irradiated ultra-thin SiO2/Si structures is investigated using Conductive-AFM. It is shown evidence, for the first time, of threshold voltage shift effects with nanometer spatial resolutions.

Effect of annealing on structural and electrical properties of ZnO and In2S3:Al thin layers

Thin films of ZnO and In2S3:Al are deposited on Pyrex substrates by spray technique. Structural and electrical properties of ZnO and β-In2S3:Al compounds were studied using X Ray Diffraction (XRD), (MEB) and the Vander Pauw method before and after annealing. The X-rays revealed that, ZnO and In2S3:Al were well crystallized respectively in the hexagonal and cubic structure. The main orientations of ZnO were (101), (100) and (110). The (101) direction is the preferentially one. The annealing favors the preferential peak crystallization with a reduction of the grains size and the thickness layer. The β-In2S3 contain Aluminum inclusion by introducing the ratio x= [Al3+]/[In3+] in sprayed solution. X-ray diffraction spectra of In2−xAlxS3 thin layer, realized for the value of z equal to 20%, show well-defined peaks of (311), (400), (511), and (440) principal orientations corresponding to cubic structure of β-In2S3. For In2S3:Al, we note that the annealing increase the intensity of all peaks with an increase of the grains size and the thickness layer. Besides, thanks to the determination of the resistance from which we calculated resistivity, we note that the annealing increase conductivity of β-In2S3:Al and decrease it for ZnO.