While the Ge(0 0 1) surface has been extensively studied, it is still debated whether it is of conducting or semiconducting nature at room temperature. The evidence collected by angle-resolved photoelectron spectroscopy experiments in the past has led to the preliminary attribution of a semiconducting nature at room temperature. In contrast, we show in this work that the pristine Ge(0 0 1) surface is conducting at room temperature by using temperature-dependent angle-resolved photoelectron spectroscopy, scanning tunneling microscopy and first principles calculations. Specifically, a surface band located ∼200 meV above the valence band maximum has been observed at room temperature. This surface band shows anisotropic dispersions along the [0 1 0] and [1 1 0] directions, but it disappears at lower measurement temperature, which indicates its occupation by thermally excited electrons. State-of-the-art density functional theory calculations undoubtedly attribute this surface band to the unoccupied π*-band formed by dangling bonds on the c(4 × 2) surface reconstruction, while evidencing fundamental differences with the p(2 × 1) reconstruction. Furthermore, the calculations demonstrate that the valence band structure observed in angle-resolved photoelectron spectroscopy experiments arise from projected bulk states and is thus insensitive to surface contamination. Our results contribute to the fundamental knowledge of the Ge(0 0 1) surface and to a better understanding of its role in micro- and opto-electronic devices.

虽然 Ge(0  0  1) 表面已被广泛研究，但它在室温下是否具有导电或半导体性质仍存在争议。过去通过角分辨光电子能谱实验收集的证据已经导致对室温下半导体性质的初步归因。相比之下，我们在这项工作中通过使用温度相关角分辨光电子能谱、扫描隧道显微镜和第一原理计算表明原始 Ge(0  0  1) 表面在室温下导电。具体而言，在室温下观察到位于价带最大值上方 ~200 meV 的表面带。该表面带显示沿 [0  1  0] 和 [1 1  0] 方向，但在较低的测量温度下消失，这表明它被热激发电子占据。最先进的密度泛函理论计算无疑将此表面带归因于由 c(4 × 2) 表面重建上的悬空键形成的未占据的 π* 带，同时证明与 p(2 × 1) 的根本差异重建。此外，计算表明，在角度分辨光电子能谱实验中观察到的价带结构来自投影体态，因此对表面污染不敏感。我们的结果有助于了解 Ge(0  0  1) 表面的基础知识，并有助于更好地理解其在微电子和光电器件中的作用。