Nanocomposites with Three-Dimensional Architecture and Impact on Photovoltaic Effect

Abstract

We demonstrate the synthesis of self-assembled threedimensional nanocomposite thin films consisting of NiO nanocolumns in an layered Aurivillius phase matrix. The structures were grown on single-crystal SrTiO 3 substrates via pulsed laser deposition (PLD) with single ceramic (PbTiO 3 ) x (BiNi 2/3 Nb 1/3 O 3 ) 1−x targets. The nanocolumns, which are about 10 nm in diameter each, extend over the entire film thickness of up to 225 nm. We reveal the difference in electrical conduction properties of the nanocolumns and the surrounding matrix on the nanoscale via conductive atomic force microscopy. The nanocomposite thin films exhibit improved photovoltaic performance compared to both pure PbTiO 3 and homogeneous Aurivillius phase thin films.

Control of Layering in Aurivillius Phase Nanocomposite Thin Films and Influence on Ferromagnetism and Optical Absorption

“…Figure 1a,d shows a transmission electron micrograph and an X-ray diffraction (XRD) pattern of a PTBNNO thin film deposited on the SrTiO 3 (STO)(001) substrate, as was also discussed in our previous publication. 8 Aurivillius phases, with the general formula (Bi 2 O 2 ) (A m−1 B m O 3m+1 ) for a phase of order m, are characterized by m perovskite blocks sandwiched within Bi 2 O 2 fluorite-like layers. The XRD pattern for an Aurivillius phase is typically interpreted as reflections arising from the lattice planes inside the rather prolonged unit cell, as depicted in Figure 1b.…”

“…However, as variations in the other process parameters can influence the growth rate, it is nevertheless an interesting question whether the film thickness can also influence the layer periodicity. Therefore, a film analogous to the 225 nm thin PTBNNO film presented in our previous work 8 was grown, with the pulse number reduced to 1/10th of the previous value. The XRD patterns of both films are shown in Figure 1e.…”

“…A perovskite-phased composite PLD target of (PbTiO 3 ) 0.65 (BiNi 2/3 Nb 1/3 O 3 ) 0.35 (PTBNNO) was used for the study, deposition from which results in a nanocomposite structure of NiO columns in an Aurivillius phase matrix, as previously reported. 8 Variations in laser fluence, temperature, and oxygen pressure were used to elaborate on the conditions that support layering and thus the Aurivillius phase. While the coarse control of the deposition parameter allows a deterministic control over the resultant phase, that is, between Aurivillius and perovskite, the fine control allows to tune the layering within the Aurivillius phase.…”

“…A perovskite-phased composite PLD target of (PbTiO 3 ) 0.65 (BiNi 2/3 Nb 1/3 O 3 ) 0.35 (PTBNNO) was used for the study, deposition from which results in a nanocomposite structure of NiO columns in an Aurivillius phase matrix, as previously reported . Variations in laser fluence, temperature, and oxygen pressure were used to elaborate on the conditions that support layering and thus the Aurivillius phase.…”

Evaluating the Band Gaps of Semiconductors by Cataluminescence

“…Universally, narrow band gap 13 semiconductors may be suitable for infrared or thermoelectric applications, while materials with wide band gaps 14 are widely used in optoelectronic devices 15 and electronic applications 16 according to their different strengths. Notably, it is known that Aurivillius-type layered perovskite oxide semiconductors have attracted much attention due to their inherent intrinsic characteristics, including internal electric field and multiple elementary compositions, which contribute to its application in photocatalysis, 17 electrocatalysis, 18 photovoltaics, 19 and so on. As a representative, the Aurivillius-type layered ferroelectric oxide, 20 especially Bi 4 Ti 3 O 12 , 21 is considered by researchers because of the unique properties of spontaneous polarization and anisotropy, giving a clear and obvious advantage in ferroelectric memory, optical device, and capacitor applications.…”