论文标题
硅在有限温度下的氢气动力学
Dynamics of hydrogen in silicon at finite temperatures from first-principles
论文作者
论文摘要
硅的氢点缺陷仍然存在未解决的问题，其披露对于SI技术的未来进步至关重要。在空旷的问题中，在从上面的$ t \ sim700 \，^{\ circ} $ c凝结为si中，将原子氢凝结成分子的机制。根据第一原理的计算，我们研究了谐波近似中有限温度下的氢单体和二聚体的热力学。地层的自由能表明，当比较高温下H $^{+} $的H $^{ - } $的种群。结果使我们能够提出分子的形成在冷却过程中发生，在温度窗口$ t \ sim700 \ textrm { - } 500 \，$ k上面，上面与Si-Si键和分离的分子相互碰撞，在此下，H $^{ - } $的hub^{ - } $的分数均为agnligible。 H $^{ - } $的形成以及最著名的快速变化中性物种的形成也可以为原子氢在高度温度下的显而易见的\ emph {Accelerated}扩散性提供解释，与在哭泣的温度下的测量值相比，原子氢的扩散率。我们最终表明，在假设它们几乎是自由转子的假设沿最小能量路径，包括在过渡状态下，它们几乎是游离的转子。
Hydrogen point defects in silicon still hold unsolved problems, whose disclosure is fundamental for future advances in Si technologies. Among the open issues is the mechanism for the condensation of atomic hydrogen into molecules in Si quenched from above $T\sim700\,^{\circ}$C to room temperature. Based on first-principles calculations, we investigated the thermodynamics of hydrogen monomers and dimers at finite temperatures within the harmonic approximation. The free energies of formation indicate that the population of H$^{-}$ cannot be neglected when compared that of H$^{+}$ at high temperatures. The results allow us to propose that the formation of molecules occurs during cooling processes, in the temperature window $T\sim700\textrm{-}500\,$K, above which the molecules collide with Si-Si bonds and dissociate, and below which the fraction of H$^{-}$ becomes negligible. The formation of H$^{-}$ and most notably of a fast-diffusing neutral species could also provide an explanation for the apparent \emph{accelerated} diffusivity of atomic hydrogen at elevated temperatures in comparison to the figures extrapolated from measurements carried out at cryogenic temperatures. We finally show that the observed diffusivity of the molecules is better described upon the assumption that they are nearly free rotors, all along the minimum energy path, including at the transition state.
