Strained germanium (𝜀-Ge) and strained silicon (𝜀-Si) buried quantum wells have enabled advanced spin-qubit quantum processors. However, in the absence of suitable lattice-matched substrates, 𝜀-Ge and 𝜀-Si are deposited on defective, metamorphic SiGe buffers, which may impact device performance and scaling. Here an alternative platform is introduced based on the heterojunction between bulk unstrained Ge and a lattice-matched strained silicon-germanium (𝜀-SiGe) barrier, eliminating the need for metamorphic buffers altogether. In a structure with a 52-nm-thick 𝜀-SiGe barrier, a low-disorder two-dimensional hole gas is demonstrated with a high-mobility of 1.33 ×105 cm2/Vs and a low percolation density of 1.4⁢(1) ×1010 cm−2. Quantum transport shows that holes confined in the buried unstrained Ge channel have a strong density-dependent in-plane effective mass and out-of-plane 𝑔-factor, pointing to a significant heavy-hole–light-hole mixing in agreement with theory. Measurements of Zeeman-split levels in quantum point contacts further highlight this character, showing a two-fold larger in-plane 𝑔-factor in Ge than in 𝜀-Ge. The prospects of strong spin–orbit interaction, isotopic purification, and of hosting superconducting pairing correlations make this platform appealing for fast quantum hardware and hybrid quantum systems. ... Read more

In this study, we report the synthesis of single-crystalline h-BN on Ni(111) under ultrahigh vacuum (UHV) conditions using hexamethylborazine (HMB) as a nonclassical precursor. The novel use of HMB facilitates the diffusion of methyl groups into the bulk of Ni(111), playing a critical role in the achievement of high-quality crystalline h-BN layers. The synthesis is performed on a 2 mm-thick Ni(111) single crystal and on a 2-μm-thick Ni(111) thin film on sapphire to evaluate the feasibility of synthesizing h-BN on industrially relevant substrates. Advanced microscopic and spectroscopic techniques confirm the successful synthesis of h-BN. The growth of h-BN was investigated by scanning tunneling microscopy and low-energy electron microscopy. Low-energy electron diffraction confirms the single crystallinity of the grown 2-dimensional layer. X-ray photoelectron spectroscopy confirms the presence of boron and nitrogen bonds at the same binding energies reported in the literature for h-BN. In contrast, photoemission electron microscopy allows identification of the presence of h-BN throughout the Ni(111) surface. This work advances the understanding of h-BN growth mechanisms on metal substrates and provides a foundation for improving synthesis methods to meet the demands of next-generation materials and devices. ... Read more