The indirect bandgap (0.67 eV) of bulk germanium (Ge) remains a major bottleneck towards its applications in optoelectronics, enabling poor optical features particularly photoluminescence. Obtaining desired optical functionalities, either by synthesizing few-atoms-thick two-dimensional (2D) germanium on silicon-based substrates, or by inducing an appreciable structural engineering in its crystal lattice, has long remained a formidable challenge yet to be mitigated. Herein, a facile vacuum-tube hot-pressing strategy to synthesize strain-engineered few-atomic-layer 2D germanium nanoplates (Ge-NPts) directly on fused silica substrate (SiO₂) is developed. Leveraging from the unique mismatch between coefficient of thermal expansion of Ge and SiO₂ substrate at elevated temperatures (700 °C), and under hydrostatic pressure (~2 GPa), a biaxial compressive strain of ~1.23 ± 0.06% in Ge lattice is engineered, causing a transition from indirect to direct bandgap with an ultra-large opening of 2.91 eV. Strained Ge nanoplates, consequently, display a remarkable 42-fold blue photoluminescence (at 300 K) compared to bulk Ge, accompanied by robust quantum-confinement effects, probed by the quantum-shift ~114 meV with decreasing thicknesses of Ge nanoplates.

大块锗（Ge）的间接带隙（0.67 eV）仍然是其在光电子学中应用的主要瓶颈，从而导致较差的光学功能（特别是光致发光）。长期以来，通过在硅基衬底上合成几原子厚的二维（2D）锗或通过在其晶格中引发可观的结构工程来获得所需的光学功能一直是一项艰巨的挑战，尚待缓解。本文中，开发了一种简便的真空管热压策略，以直接在熔融石英衬底（SiO ₂）上合成应变工程化的几个原子层的二维锗纳米板（Ge-NPts）。利用Ge和SiO ₂的热膨胀系数之间的独特失配在高温（700°C）和静水压力（〜2 GPa）下对基体进行工程化处理，设计出Ge晶格中〜1.23±0.06％的双轴压缩应变，从而从具有超大开口的间接带隙过渡到为2.91 eV。因此，与块状Ge相比，应变的Ge纳米板显示出显着的42倍蓝色光致发光（在300 K下），并伴随着强大的量子约束效应，这是通过量子位移〜114 meV随Ge纳米板厚度减小而探测到的。