Operando Structural Characterization of the E-ALD Process Ultra-Thin Films Growth

Abstract

Spanning from nanoelectronics to new solar energy materials, technological development in the recent years requested highly controlled nanostructured surfaces, ultra-thin films, and 2D structured materials. In general, although very favorable from a full life cycle assessment (FLCA) standpoint, electrodeposition hardly allows to obtain the high order required by recent technologies. In particular cases, the electrodeposition enables the deposition of atomic layers by means of surface limited reactions (SLRs). By exploiting SLRs, it is possible to define layer-by-layer deposition scheme of different atomic layers; we refer to these schemes as electrochemical atomic layer deposition (E-ALD) and when the growth of the film is epitaxial with the substrate, the techniques are called electrochemical atomic layer epitaxy (ECALE). Aiming at characterizing structure and growth of materials grown by means of E-ALD, surface analysis techniques apply better. In particular, surface X-ray diffraction (SXRD) with high brilliance synchrotron sources enables the operando structural analysis in electrochemical environment. In recent years, several works on the operando surface characterization by means of SXRD have been reported. Thanks to novelties in the field of operando SXRD experiments, semiconducting systems were studied, such as single and multilayer of CdS and Cu 2 S.

Operando SXRD of E-ALD deposited sulphides ultra-thin films: Crystallite strain and size

“…This automated system allows a combination of the solutions within the electrochemical cell ensuring good fluid dynamics and a low contamination due to exposure to air. The four samples were grown in two different electrochemical flow cells, the first one designed for the E-ALD process, and the second specifically designed for coupling E-ALD with an operando SXRD investigation [3,20,21]. In both cases, the cell is delimited by the working electrode on one side and by the counter electrode on the other side, while the inlet and the outlet of the solutions were placed on the side walls [19].…”

“…The operando measurements were performed at the ID03 beamline of European Synchrotron Radiation Facility (ESRF). The measurements were performed by means of the six circle vertical axis diffractometer installed in the EH1 hutch [3,23]. The diffracted intensity has been registered by means of a MAXIPIX fast readout areal detector [24].…”

“…The electrochemical cell was mounted on the diffractometer stage. All measurements were carried out using a 24 keV X-ray radiation in order to allow a high transmission through the EC cell walls and solutions [3,23]. (111) surface cell used as reference system of the reciprocal space.…”

Successes and Issues in the Growth of Moad and MoSe2 on Ag(111) by the E-ALD Method

“…One of the most common SLR in electrochemistry is the under potential deposition (UPD) [7,8]. When the E-ALD outcome is a strictly epitaxial film, the technique is named electrochemical atomic layer epitaxy (ECALE) [9,10]. Indeed, the E-ALD method enables the growth of monolayers of different elements, one above the other through, the alternate deposition of an atomic layer under the surface limited constraints ensured by the exploitation of the SLRs.…”

Investigations on the Electrochemical Atomic Layer Growth of Bi2Se3 and the Surface Limited Deposition of Bismuth at the Silver Electrode

“…The layered structure of the rhombohedral crystal, with Van der Waals interactions between the layers, encourages synthetic opportunities for the direct growth of layered structures or two-dimensional materials. In this study we evaluate the possibility to exploit the Electrochemical Atomic Layer Deposition (E-ALD) method [ 6 , 7 ] to synthesize these kind of materials. E-ALD is a widely known method capable of finely controlling the deposition process, allowing the growth at room temperature and pressure of highly ordered crystalline structures, starting from the first atomic layers, without the need for any further treatment (e.g., thermal annealing).…”