Localized Photoluminescence Imaging of Bi‐Layered Cuprous/Cupric Oxide Semiconductor Films by Synchrotron Radiation

Abstract

To develop multi‐layered semiconductor film devices, like a solar cell device, effects of localized impurities and layered interface mismatches on photovoltaic properties should be understood quantitatively and controlled effectively. However, the research of localized photoluminescence on layered semiconductor film devices is delayed. This is because, unfortunately, a measurement method for photoluminescence properties with spatial resolution on the sub‐micron scale, which could provide much of the local photoluminescence properties in bulk multi‐layered film semiconductor devices, has not been developed. In this study, a mapping method for local photoluminescence properties has been developed by utilizing a focused synchrotron radiation beam to evaluate localized photoluminescence affected by microstructures in bi‐layered semiconductor films. Luminescence maps of copper oxide semiconductor film which varies in emission energy and position are successfully obtained under the conditions of a focused beam size of 5 μm in width and 300 nm in height. The possibility of investigation for localized photoluminescence related with the microstructure is strongly suggested. This technique will support and enhance the development of high‐performance multi‐layered semiconductor film devices.

High-Resolution Mapping of Local Photoluminescence Properties in CuO/Cu2O Semiconductor Bi-Layers by Using Synchrotron Radiation

“…The obtained peaks in Figure 4 are related to the emission light energies reported for each material constituting the film sample. It was noted that the intensity of light emission was weak compared to the previous work [ 12 ], due to a smaller-sized X-ray beam. Nonetheless, despite reducing the X-ray beam’s size, the local measurement of photoluminescence spectra was successful, although a delicate set-up for the spectrometer was necessary.…”

“…It was also reported that the (0001)-oriented ZnO layer emits not only near-band emissions at 3.25 eV –3.3 eV by recombination [ 35 ], but also visible light emissions at 2.28 eV and 2.8 eV [ 36 ]. In addition, the substrates possess emission peaks at 1.9 eV and 2.7 eV [ 12 ]. The obtained peaks in Figure 4 are related to the emission light energies reported for each material constituting the film sample.…”

“…The size of the focused beam can be estimated at 0.3 μm in width and 0.3 μm in height of the sample position. The width of the beam used in this study was approximately 16 times smaller than the beam used in the previous research [ 12 ].…”

“…Currently, scanning X-ray microscopy at a synchrotron radiation facility is available, with a 65 nm-size focusing beam [ 11 ]. We proposed and applied an imaging technique for local photoluminescence mapping by means of a high-intensity focused X-ray at the undulator beam line in the Japanese synchrotron radiation facility, SPring-8, in our previous research [ 12 ]. The spatial distribution of localized photoluminescence in a CuO/Cu 2 O semiconductor was measured and demonstrated with a grid size of 0.3 μm × 5 μm.…”

“…The Cu 2 O/CuO bi-layered film utilized in the previous research [ 12 ] was prepared form the electrodeposited Cu 2 O films by annealing at 673 K for 3.6 ks (1 h) in air [ 20 ]. It has been reported that the luminescence properties of the electrodeposited Cu 2 O and CuO formed by annealing are different [ 21 ].…”