npsm 새물리 New Physics : Sae Mulli

pISSN 0374-4914 eISSN 2289-0041
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Research Paper

New Phys.: Sae Mulli 2020; 70: 914-919

Published online November 30, 2020 https://doi.org/10.3938/NPSM.70.914

Copyright © New Physics: Sae Mulli.

Fabrication of Epitaxial Cu$_{2}$O (111) Films from Cu(111) thin Films by Rapid Thermal Oxidation

Miyeon CHEON1, Yousil LEE1, Sujae KIM1, Se Young jeong2,3*

1Crystal Bank Research Institute, Pusan National University, Busan 46241, Korea

2Dept. of Cogno-Mechatronics Engineering, Pusan National University, Busan 46241, Korea
3Dept. of Optics and Mechatronics Engineering, Pusan National University, Busan 46241, Korea

Correspondence to:syjeong@pusan.ac.kr

Received: August 11, 2020; Revised: October 7, 2020; Accepted: October 15, 2020

Abstract

Due to the energy gaps of copper from 2.1 to 2.7 eV, its high light absorption, its nontoxicity and its abundance on the earth, Cu$_{2}$O is an attractive material for use in various areas such as photovoltaic power generation, photocatalytic reactions, water photolysis, nonlinear optics, and gas sensing. Many researches efforts are being conducted to obtain high-quality Cu$_{2}$O thin films. In this study, high-quality, epitaxial Cu$_{2}$O (111) thin films were obtained via a relatively simple method, rapid thermal processes at high temperature of RF sputtered Cu (111) thin film on a sapphire substrate. XRD, SEM and UV-Vis spectroscopy measurements confirmed the high crystallinity of the Cu$_{2}$O (111) thin film oxidized for 30 minutes at a temperature of 800 $^{\circ}$C under an atmosphere of argon with 3 ppm of oxygen. Also, because of the high crystal-quality of the Cu$_{2}$O (111) thin films, blue and indigo energy gaps at room temperature were obtained from the absorption coefficient $\alpha$. The obtained energy band gaps are consistent with the theoretical values obtained from Cu$_{2}$O bulk structures.

Keywords: Cuprous oxide thin film, Epitaxial, Cu thin film, Rapid thermal annealing, Oxide thin film, Optical properties, Energy band gap

최근 들어 2.1 eV에서 2.7 eV의 가시광선 영역에서 에너지 간격을 가지고 있어 빛의 흡수도가 높고 지구상에 풍부한 구리를 기반으로 하며 독성 또한 가지고 있지 않아 태양광 발전, 광촉매 반응, 물의 광분해, 비선형 광학, 가스 검출 등의 여러 분야에서 집중을 받고 있는 제일 산화구리 Cu$_{2}$O 박막을 얻고자 하는 연구가 많이 진행되고 있다. 본 연구에서는 비교적 간단한 방법인 Cu(111) 박막의 고온 열처리를 통하여 높은 결정성을 가지는 Cu$_{2}$O (111) 박막을 성장하는 연구를 진행하였다. 성장된Cu$_{2}$O (111) 박막의 XRD와 SEM, UV-Vis spectroscopy 측정을 통하여 아르곤 분위기 하에 800 $^{\circ}$C의 온도에서 30 분 열처리한 경우 높은 결정성을 가지는 것을 확인하였다, 또한 흡광계수 $\alpha$를 통하여 상온에서 Cu$_{2}$O (111) 박막의 청색 (blue)과 남색 (indigo) 에너지 간격을 얻을 수 있었으며 이것 또한 Cu$_{2}$O (111) 박막이 높은 결정성을 가지기 때문에 가능하였으며 얻은 값들은 bulk Cu$_{2}$O구조로부터 얻어진 이론적인 값과 잘 일치하였다.

Keywords: 제일 산화구리 박막, 에피택셜, 구리 박막, 급속 열처리, 산화 박막, 광학적 특성, 에너지 간격

Figures

Fig. 1.  XRD spectra of the pristine Cu thin film (a) and Cu$_{2}$O thin films oxidized in the atmosphere of air (b) and argon gas (c) at 800 $^{\circ}$C for 30 minutes. The inset of (b) presents the XRD results near CuO (002) and Cu$_{2}$O (111) peaks of Cu$_{2}$O thin films oxidized in air (red) and argon gas (green). Open circles (○), closed circle (●), open triangle (△) and closed triangle (▼) indicate the peaks of Al$_{2}$O$_{3}$ (0006), Cu(111), CuO(002) and Cu$_{2}$O(111), respectively.

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