Supplemental Materials
Optical and Electrical Properties of Cu-based All Oxide Semi-Transparent Photodetector
Hong-Sik Kim,1 Malkeshkumar Patel,1 Pankaj Yadav,1 Joondong Kim1,[a]), Ahrum Sohn,2and Dong-Wook Kim,2,b)
1Photoelectric and Energy Device Application Lab (PEDAL) and Department of Electrical Engineering, Incheon National University, 119 Academy Rd. Yeonsu, Incheon, 406772, Republic of Korea
2Department of Physics, Ewha Womans University, Seoul 120750, Republic of Korea
Materials and Device Fabrication:
Glass substrates were sequentially cleaned in acetone, isopropyl alcohol, and deionized water before depositing the In2O3:SnO2 (ITO) layer. Thin films of p-type CuO and Cu2O were deposited using the reactive sputtering of a copper target (4-inch diameter with 99.99% purity) in presence of oxygen. The base vacuum pressure of the deposition chamber was 5 10-6 mbar. The argon to oxygen ratio was 15:7 and 15:3 to get CuO and Cu2O phases, respectively. Deposition of CuO and Cu2O was performed at room temperature. For all the deposition conditions, the DC power and working pressure were maintained at 100 W and 5 mTorr, respectively. For making a heterojunction, n-type ZnO layers were deposited on the CuO and Cu2O layers. For the deposition of ZnO, a target of 4-inch diameter with 99.99% purity was used. ZnO thin films were deposited at room temperature at Ar gas pressure of 5 mTorr and DC power of 50 W.
Characterization:
The structural properties of copper oxide films were analysed using X-ray diffraction (XRD) measurement (Pananalytical) with CuK (=1.54060 Å). The XRD data have been taken in the range of 2 from 20–80 with a step size of 0.015. The morphological property of the films were analysed using field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) The optical properties of CuO and Cu2O films were characterized using UV-visible-NIR photo-spectrometer (UV-2800, Shimadzu) combined with diffused reflectance integrated sphere in the wavelength range of 220 nm to 1400 nm. The dark current-voltage (I-V) characterizations were done using the source-measuring unit (Keithley 2400). The surface work function of the samples was measured using a Kelvin probe force microscopy (KPFM) system (XE-100, Park System). The electrical properties of CuO and Cu2O samples were investigated by Hall measurement system (AHT5573R, Ecopia). A light emitting diode (LED) with λ = 455-460 nm and 1 mW cm-2 was used as a light source for exciting the semi-transparent photodetectors.
ESI-1
[a]Authors to whom correspondence should be addressed.
Electronic mails: Joondong Kim () and Dong-Wook Kim ()