One-reactor vacuum and plasma synthesis of transparent conducting oxide nanotubes and nanotrees: from single wire conductivity to ultra-broadband perfect absorbers in the NIR

Abstract

The eventual exploitation of one-dimensional nanomaterials yet needs the development of scalable, high yield, homogeneous and environmentally friendly methods able to meet the requirements for the fabrication of under design...

Photoelectrochemical Water Splitting with ITO/WO3/BiVO4/CoPi Multishell Nanotubes Enabled by a Vacuum and Plasma Soft-Template Synthesis

“…It is also apparent in Figure f that the NT width slightly varies from the tip to the side through which it anchors onto the ITO substrate. This particular shape of NTs is a consequence of the MS growth mechanism during the deposition onto 1D scaffolds . Depending on conditions, some of the MS-deposited particles may be ballistic and undergo shadowing effects during their trajectory from the target up to their landing position on the surface, preferentially accumulating at the outer parts of nanostructures .…”

“…In summary, as schematized in Figure b, we claim that the core–shell ITO/WO 3 /BiVO 4 nanostructure of the NT electrodes offers simultaneously a high electrochemical surface for the OER and minimum electrical resistance losses due to its particular core–shell configuration. The scattering of light within the NT structure is another factor contributing to the increase in the photocurrent …”

“…Scheme a presents a conceptual representation of the synthesis steps required to produce the NT electrodes. The method is large-area compatible and, regarding the incorporation of the ITO and WO 3 layers, can be carried out in a single vacuum deposition reactor (i.e., following a one-reactor approach) . The fundamentals of the procedure rely on the use of small-molecule single-crystalline organic nanowires (ONWs) as soft-template 1D scaffolds, which can be fabricated and removed upon mild heating in vacuum or air.…”

“…In a subsequent step (iv), an ITO layer is deposited around the ONWs. For this step, we follow the procedure described in ref where we have reported the fabrication by magnetron sputtering (MS) of ITO nanotubes (NTs) on a flat ITO substrate. MS is a well-established industrially scalable technique usually employed for the fabrication of compact thin films and, more recently, also for porous structures of WO 3 electrodes and WO 3 /BiVO 4 photoelectrodes, , the former under an oblique angle configuration.…”

“…Small ITO nuclei were additionally deposited by MS for very short times (step (ii)) to serve as nucleation sites for the formation of crystalline phthalocyanine ONWs (step (iii)). Details of the experimental procedure for the formation of the ONW templates by thermal evaporation can be found in previous publications ,, (see also Supporting Information section S1). Then, ITO was deposited by MS under conditions leading to the formation of a conformal layer completely covering the ONW templates (step (iv)).…”