N掺杂Cu_2O薄膜的光学性质及第一性原理分析

摘要

N-doped Cu_2O films are deposited at different temperatures by sputtering a CuO target in the mixture of Ar and N2.By the analysis of transmission spectra,it is found that the N-doped Cu_2O films are changed into a direct allowed band-gap semiconductor and the optical band gap energy is enlarged to 2.52±0.03 eV for the films deposited at different temperatures.The first-principles calculations indicate that the energy band gap increase by 25%,which is in good agreement with the experimental result.The change from a direct forbidden band-gap transition to a direct allowed band-gap transition can be attributed to the occupation of 2p electrons of N at the top of valence band in the N-doped Cu_2O film.%采用射频磁控溅射技术,在不同温度下制备了N掺杂Cu_2O薄膜.透射光谱分析发现,N掺杂导致Cu_2O成为允许的带隙直接跃迁半导体,并使Cu_2O的光学禁带宽度增加.不同温度下沉积的薄膜光学禁带宽度E_g=2.52±0.03 eV.第一性原理计算表明,N掺杂导致Cu_2O的禁带宽度增加了约25%,主要与价带顶下移和导带底上移有关,与实验报道基本符合.N的2p电子态分布不同于O原子,在价带顶附近具有较大的态密度是N掺杂Cu_2O变成允许的带隙直接跃迁半导体的根本原因.