PECVD of Hematite Nanoblades and Nanocolumns: Synthesis, Characterization, and Growth Model

Abstract

Fe 2 O 3 nanostructures are fabricated on Si(100) and SiO 2 by plasma enhanced (PE)CVD from a Fe III b-diketonate precursor. Depositions are carried out in Ar-O 2 plasmas, devoting particular attention to the influence of growth temperature (from 60 to 400 8C) on material chemico-physical properties. Remarkably, high purity, single-phase a-Fe 2 O 3 nanostructures are obtained at temperatures as low as 60 8C. Furthermore, the deposit nano-organization can be tuned from <110>-oriented 2D nanoblade arrays to denser nanocolumns upon increasing the deposition temperature. A possible growth model is proposed to account for the observed structural/morphological features and light absorption properties of the target materials.

Advances in photocatalytic NOx abatement through the use of Fe2O3/TiO2 nanocomposites

“…Beside a major band at 530.0 eV [(I), 67% of the overall O content], related to M-O-M bonds (M ¼ Fe, Ti), a second component (II) at higher BE (531.6 eV) was attributed to hydroxyl/carbonate species arising from exposure to the outer atmosphere. 21,25,46 Irrespective of the sputtering time, Ti 2p 3/2 BE values (458.8 eV, Fig. 1c) were in line with TiO 2 presence and enabled to exclude the formation of Fe-Ti-O ternary phases.…”

“…50 Depositions were performed on p-type Si(100) substrates (MEMC®, Merano, Italy, 30 mm  30 mm  1 mm), subjected to an established cleaning procedure prior to each deposition. 25 Electronic grade argon and oxygen were used as plasma sources. The iron precursor, Fe(dpm) 3 (dpm ¼ 2,2,6,6-tetramethyl-3,5heptanedionate), synthesized as recently reported, 44 was placed in an external glass vaporizer heated at 130 C with an oil bath, and transported into the reaction chamber by an Ar ow [rate ¼ 60 standard cubic centimeters per minute (sccm)].…”

“…1a] were similar for all specimens and conrmed Fe 2 O 3 presence. 25,28,[44][45][46]60 As a matter of fact, surface iron signals could be detected even for the higher titanium loadings (z11 at% aer 4 h of sputtering, sample FeTi4).…”

“…21-24 Fe 2 O 3 , a nontoxic and largely available semiconducting oxide (E G ¼ 2.2 eV), can in fact enable to extent light absorption into the Vis range, but is characterized by a fast electron-hole recombination, resulting in poor photocatalytic performances. [25][26][27][28] Attempts to circumvent these problems have included the control of Fe 2 O 3 nano-organization, as well as its chemical modication by doping, surface passivation or functionalization with suitable systems. 19,23,28,29 In particular, the design of Fe 2 O 3 /TiO 2 nanocomposites is expected to provide an improved efficiency in solar-driven De-NO x processes, synergistically exploiting the favorable properties of single-phase components and reducing, at the same time, their disadvantages.…”

“…Herein, we propose the preparation of supported Fe 2 O 3 /TiO 2 composite materials by an original low-temperature plasmaassisted strategy, based on the initial PE-CVD of Fe 2 O 3 followed by RF-sputtering of moderate TiO 2 amounts. Under controlled conditions, PE-CVD yields highly porous Fe 2 O 3 systems with tailored nano-organization, 25,44 whereas RFsputtering, thanks to its inltration power, enables an efficient in-depth dispersion of Ti-based species into the Fe 2 O 3 matrix, 45,46 resulting in an intimate Fe 2 O 3 /TiO 2 contact. As already demonstrated, this approach is a highly versatile tool for the fabrication of supported nanomaterials with tunable structure and composition, thanks to the unique activation mechanisms characterizing the adopted non-equilibrium plasmas.…”