Palladium gates for reproducible quantum dots in silicon

We replace the established aluminium gates for the formation of quantum dots in silicon with gates made from palladium. We study the morphology of both aluminium and palladium gates with transmission electron microscopy. The native aluminium oxide is found to be formed all around the aluminium gates, which could lead to the formation of unintentional dots. Therefore, we report on a novel fabrication route that replaces aluminium and its native oxide by palladium with atomic-layer-deposition-grown aluminium oxide. Using this approach, we show the formation of low-disorder gate-defined quantum dots, which are reproducibly fabricated. Furthermore, palladium enables us to further shrink the gate design, allowing us to perform electron transport measurements in the few-electron regime in devices comprising only two gate layers, a major technological advancement. It remains to be seen, whether the introduction of palladium gates can improve the excellent results on electron and nuclear spin qubits defined with an aluminium gate stack

Observation of the single-electron regime in a highly tunable silicon quantum dot

We report on low-temperature electronic transport measurements of a silicon metal-oxide-semiconductor quantum dot, with independent gate control of electron densities in the leads and the quantum dot island. This architecture allows the dot energy levels to be probed without affecting the electron density in the leads, and vice versa. Appropriate gate biasing enables the dot occupancy to be reduced to the single-electron level, as evidenced by magnetospectroscopy measurements of the ground state of the first two charge transitions. Independent gate control of the electron reservoirs also enables discrimination between excited states of the dot and density of states modulations in the leads.Comment: 4 pages, 3 figures, accepted for Applied Physics Letter

Anisotropic Pauli spin blockade in hole quantum dots

We present measurements on gate-defined double quantum dots in Ge-Si core-shell nanowires, which we tune to a regime with visible shell filling in both dots. We observe a Pauli spin blockade and can assign the measured leakage current at low magnetic fields to spin-flip cotunneling, for which we measure a strong anisotropy related to an anisotropic g-factor. At higher magnetic fields we see signatures for leakage current caused by spin-orbit coupling between (1,1)-singlet and (2,0)-triplet states. Taking into account these anisotropic spin-flip mechanisms, we can choose the magnetic field direction with the longest spin lifetime for improved spin-orbit qubits

Grayson Ligament:A Revised Description of its Anatomy and Function

PURPOSE: Grayson ligament has been described as a common pathway for digital contracture in Dupuytren disease. Its anatomical descriptions in the literature are, however, inconsistent. METHODS: We have performed a microsurgical dissection study in 20 fresh-frozen and thawed digits to revisit the anatomy of Grayson ligaments. We also performed dissections in Thiel-preserved hands to be able to study the changes in tension of the ligaments during flexion and extension of the finger. RESULTS: We found the ligaments originally described by Grayson to be the best developed part of a trabecular network of fibers, originating in continuity with the outer adventitial layer of the flexor tendon sheath and running toward their insertions into the skin in multiple planes, all volar to the neurovascular bundle. The most dorsal fibers, which cover the neurovascular bundles, form a chevron shape with its midline apex pointing distally in an extended finger. During flexion, the fibers become more transversely oriented. CONCLUSIONS: We found Grayson ligament comprises a trabecular network of fibers, instead of a ligament, with a dynamic fiber orientation on the volar side of the finger. The main function of this network of fibers seems to be the stabilization of the skin and fat pad in digit extension while the relaxation in flexion allows the skin and volar fat pad to adapt optimally to the form of the object that is held. CLINICAL RELEVANCE: The new insights in the anatomy of Grayson trabecular network of fibers may be of importance in the understanding of the pathological anatomy of Dupuytren disease