发表机构
Linköping University（林雪平大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究结合多种实验与理论方法，明确了ScₓGa₁₋ₓN的局域配位、结构演化与性能关联，发现钪合金化可降低极化切换势垒、提升压电性能且保留长程纤锌矿结构。
AI 中文摘要
钪合金化的纤锌矿氮化物具有高度可调的机电与铁电性能，但它们的晶格演化与局域键合环境之间的关系仍未充分明确，尤其是在ScₓGa₁₋ₓN体系中。本研究结合X射线衍射、钪K边X射线吸收近边结构（XANES）、扩展X射线吸收精细结构（EXAFS）以及第一性原理计算，探究了ScₓGa₁₋ₓN在从稀组分到中等组分范围内的结构与局域键合演化。钪的引入会产生各向异性晶格膨胀，并使c/a比值逐渐降低。XANES与EXAFS结果显示，钪周围的局域环境发生同步改变：在x=0.06至0.26的范围内，有效Sc-N配位数从4.1(4)增至4.5(2)，平均Sc-N键长从2.045(7)Å增至2.081(8)Å；该局域响应伴随钪K边预峰强度降低，与局域四面体不对称性逐渐减弱的结果一致。第一性原理计算表明，这些结构变化与钪周围的位点选择性畸变及结构能量景观的逐渐扁平化相关。随着钪含量增加，计算得到的本征极化切换势垒从24.2meV/ų降至19.0meV/ų，压电应力系数（e₃₃）从0.82C/m²增至1.66C/m²，弹性常数（C₃₃）从380GPa降至227GPa，最终使压电应变系数（d₃₃）从2.99pC/N增至12.46pC/N。上述结果表明，在研究的组分范围内，钪的引入逐渐改变了ScGaN的局域配位环境与结构能量学，同时长程纤锌矿结构得以保留。
英文摘要
Sc-alloyed wurtzite nitrides exhibit strongly tunable electromechanical and ferroelectric properties, yet the relationship between their lattice evolution and local bonding environment remains insufficiently established, particularly in Sc$_x$Ga$_{1-x}$N. Here, we investigate the structural and local bonding evolution of Sc$_x$Ga$_{1-x}$N across the dilute-to-intermediate composition range by combining X-ray diffraction, Sc K-edge X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS) and first-principles calculations. Sc incorporation produces an anisotropic lattice expansion and a progressive reduction in the c/a ratio. XANES and EXAFS reveal a concurrent modification of the local environment around Sc, with the effective Sc-N coordination number increasing from 4.1(4) to 4.5(2) and the average Sc-N bond length increasing from 2.045(7) to 2.081(8)Å over x=0.06-0.26. The local response is accompanied by a reduction in the Sc K-edge pre-edge intensity, consistent with a gradual reduction of the local tetrahedral asymmetry. First-principles calculations show that these structural changes are associated with site-selective distortions around Sc and progressive flattening of the structural energy landscape. The calculated intrinsic polarization-switching barrier decreases from 24.2 to 19.0 meV/Å$^3$ with increasing Sc content, while the calculated piezoelectric stress coefficient (e$_{33}$) increases from 0.82 to 1.66~C/m$^2$ and elastic constant (C$_{33}$) decreases from 380 to 227~GPa, resulting in an increase of piezoelectric strain coefficient (d$_{33}$) from 2.99 to 12.46~pC/N. These results show that Sc incorporation progressively modifies the local coordination environment and structural energetics of ScGaN while the long-range wurtzite structure remains preserved over the investigated composition range.
Comments13 pages, 4 figures
