State Key Lab of Crystal Materials, Institute of Crystal Materials, Shandong University, Jinan 250100, China.
Center for Optics Research and Engineering of Shandong University, Shandong University, Qingdao 266237, China.
Molecules. 2022 Dec 17;27(24):9014. doi: 10.3390/molecules27249014.
Surface defects are usually associated with the formation of other forms of expansion defects in crystals, which have an impact on the crystals' growth quality and optical properties. Thereby, the structure, stability, and electronic structure of the hydrogen and oxygen vacancy defects (V and V) on the (100) and (101) growth surfaces of KDP crystals were studied by using density functional theory. The effects of acidic and alkaline environments on the structure and properties of surface defects were also discussed. It has been found that the considered vacancy defects have different properties on the (100) and (101) surfaces, especially those that have been reported in the bulk KDP crystals. The (100) surface has a strong tolerance for surface V and V defects, while the V defect causes a large lattice relaxation on the (101) surface and introduces a deep defect level in the band gap, which damages the optical properties of KDP crystals. In addition, the results show that the acidic environment is conducive to the repair of the V defects on the surface and can eliminate the defect states introduced by the surface V defects, which is conducive to improving the quality of the crystal surface and reducing the defect density. Our study opens up a new way to understand the structure and properties of surface defects in KDP crystals, which are different from the bulk phase, and also provides a theoretical basis for experimentally regulating the surface defects in KDP crystals through an acidic environment.
表面缺陷通常与晶体中其他形式的扩展缺陷的形成有关，这些缺陷会影响晶体的生长质量和光学性能。因此，采用密度泛函理论研究了 KDP 晶体（100）和（101）生长表面上氢和氧空位缺陷（V 和 V）的结构、稳定性和电子结构。还讨论了酸性和碱性环境对表面缺陷结构和性质的影响。研究发现，所考虑的空位缺陷在（100）和（101）表面上具有不同的性质，特别是在大块 KDP 晶体中已报道的性质。（100）表面对表面 V 和 V 缺陷具有很强的容忍性，而 V 缺陷会导致（101）表面的晶格松弛较大，并在能带隙中引入深缺陷能级，从而破坏 KDP 晶体的光学性质。此外，结果表明，酸性环境有利于表面 V 缺陷的修复，可以消除表面 V 缺陷引入的缺陷态，有利于提高晶体表面质量，降低缺陷密度。我们的研究为理解 KDP 晶体表面缺陷的结构和性质开辟了新途径，这些性质与体相不同，也为通过酸性环境实验调节 KDP 晶体表面缺陷提供了理论依据。
