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Photoinduced trapping of charge at sulfur vacancies and copper ions in photorefractive Sn2P2S6crystals
Journal of Applied Physics ( IF 2.7 ) Pub Date : 2021-02-23 , DOI: 10.1063/5.0042905
T. D. Gustafson 1 , E. M. Golden 1 , E. M. Scherrer 1 , N. C. Giles 1 , A. A. Grabar 2 , S. A. Basun 3, 4 , D. R. Evans 3 , J. E. Slagle 3 , L. E. Halliburton 4, 5
Affiliation  

Electron paramagnetic resonance (EPR) is used to monitor photoinduced changes in the charge states of sulfur vacancies and Cu ions in tin hypothiodiphosphate. A Sn2P2S6 crystal containing Cu+ (3d10) ions at Sn2+ sites was grown by the chemical vapor transport method. Doubly ionized sulfur vacancies ( V S 2 +) are also present in the as-grown crystal (where they serve as charge compensators for the Cu+ ions). For temperatures below 70 K, exposure to 532 or 633 nm laser light produces stable Cu2+ (3d9) ions, as electrons move from Cu+ ions to sulfur vacancies. A g matrix and a 63,65Cu hyperfine matrix are obtained from the angular dependence of the Cu2+ EPR spectrum. Paramagnetic singly ionized ( V S +) and nonparamagnetic neutral ( V S 0) charge states of the sulfur vacancies, with one and two trapped electrons, respectively, are formed during the illumination. Above 70 K, the neutral vacancies ( V S 0) are thermally unstable and convert to V S + vacancies by releasing an electron to the conduction band. These released electrons move back to Cu2+ ions and restore Cu+ ions. Analysis of isothermal decay curves acquired by monitoring the intensity of the Cu2+ EPR spectrum between 74 and 82 K, after removing the light, gives an activation energy of 194 meV for the release of an electron from a V S 0 vacancy. Warming above 120 K destroys the V S + vacancies and the remaining Cu2+ ions. The photoinduced EPR spectrum from a small concentration of unintentionally present Ni+ ions at Sn2+ sites is observed near 40 K in the Sn2P2S6 crystal.

中文翻译:

光致折射Sn2P2S6晶体中硫空位和铜离子处的光诱导电荷俘获

电子顺磁共振(EPR)用于监测次硫代二磷酸锡中硫空位和Cu离子的电荷状态的光诱导变化。通过化学气相传输法生长了在Sn 2+位点上包含Cu +(3d 10)离子的Sn 2 P 2 S 6晶体。双电离硫空位( V 小号 2个 +)也存在于刚生长的晶体中(它们在其中充当Cu +离子的电荷补偿剂)。对于低于70 K的温度,当电子从Cu +离子移动到硫空位时,暴露于532或633 nm激光中会产生稳定的Cu 2+(3d 9)离子。从Cu 2+ EPR光谱的角度依赖性获得了一个g矩阵和一个63,65 Cu超细矩阵。顺磁单电离( V 小号 +)和非顺磁性中性点( V 小号 0)在照明过程中分别形成一个和两个被捕获的电子的硫空位的电荷态。70 K以上,空缺( V 小号 0)具有热不稳定性,并转换为 V 小号 +通过将电子释放到导带来实现空位。这些释放的电子移回Cu 2+离子并恢复Cu +离子。通过监测74和82 K之间的Cu 2+ EPR光谱的强度而获得的等温衰减曲线的分析,在去除光后,其激活能为194 meV,用于从电子中释放电子。 V 小号 0空缺。超过120 K变暖会破坏 V 小号 +空位和剩余的Cu 2+离子。在Sn 2 P 2 S 6晶体中,在40 K附近观察到少量的Sn 2+处无意存在的Ni +离子引起的光致EPR光谱。
更新日期:2021-02-25
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