Cu₂O porous nanostructured films fabricated by positive bias sputtering deposition

Abstract

In this work, the authors fabricated Cu2O porous nanostructured films (PNFs) on glass slide substrates by the newly developed positive bias deposition approach in a balanced magnetron sputtering (MS) system. It was found that the surface morphology, crystal structure and optical property of the as-deposited products were greatly dependent on the applied positive substrate bias. In particular, when the substrate was biased at +50 V and +150 V, both of the as-prepared Cu2O PNFs exhibited a unique triangular pyramids-like structure with obvious edges and corners and little gluing, a preferred orientation of (111) and a blue shift of energy band gap at 2.35 eV. Quantitative calculation results indicated that the traditional bombardment effects of electrons and sputtering argon ions were both negligible during the bias deposition in the balanced MS system. Instead, a new model of tip charging effect was further proposed to account for the controllable formation of PNFs by the balanced bias sputtering deposition.

Nanoinstabilities of Cu2O porous nanostructured films as driven by nanocurvature effect and thermal activation effect

“…[25]. In this bias deposition, the tip charging effect [25,26] was demonstrated to dominate the formation process of the PNFs. To investigate the physical and chemical instabilities of the as-prepared Cu2O PNFs, several kinds of heating treatments such as rapid thermal processing (RTP), high vacuum annealing (HVA), dry-oxygen oxidation and wet-oxygen oxidation were respectively carried out at 200-500 ℃ for a duration of 30 min.…”

Selective bias deposition of CuO thin film on unpolished Si wafer

“…Consequently, the incident Cu atoms will be uniformly attracted by the uniform electrostatic field and finally a uniform, flat and compact CuO thin film is thus formed. Also note that the morphology of CuO thin film deposited on polished Si wafer is greatly different from that of Cu 2 O thin film deposited on glass side at a substrate bias of +50 V [13] although the substrate morphologies are both smooth and flat. This may be attributed to two possible reasons.…”

“…The sputtering deposition was carried out at a RF power of 80 W at room temperature and the deposition duration was controlled to be 60 min. The other details and parameters can be found in [13]. It has been demonstrated that the residual O 2 in the pre-pumped vacuum chamber is the main oxygen source for the oxidation of sputtering Cu atoms [15].…”

“…It has been demonstrated that the residual O 2 in the pre-pumped vacuum chamber is the main oxygen source for the oxidation of sputtering Cu atoms [15]. Relative to the case in [13][14][15], the higher base pressure (2.0×10 −3 versus 5.0×10 −4 Pa) in this work can provide more sufficient O 2 (2.08×10 11 versus 5.2×10 10 atoms/cm 3 , four times) for the oxidation of Cu atoms, which may result in the formation of CuO rather than Cu and Cu 2 O. The as-achieved CuO thin films were then characterized by a field-emission scanning electron microscope (SEM, ZEISS SUPRA 55), a powder x-ray diffractometer (XRD, RIGAKU D/Max 2500 PC) and an ultraviolet-visible (UV-vis) spectrophotometer (METASH UV-9000S) to study their surface morphology, crystal structure and optical properties.…”

“…For example, during glancing angle deposition [11,12], the shadowing effect of rough substrate surface induces the columnar growth of thin films, which has been studied in detail. Recently, our group further demonstrated that when the glass slide substrate was positively or negatively biased, the tip charging effect of substrate surface would result in the formation of Cu 2 O porous nanostructured films [13,14]. Nevertheless, we have not studied the bias deposition of CuO thin films on textured Si wafers under external electric field.…”