arXiv subjects

Shota Iizuka

Publications and source records attributed to Shota Iizuka.

3 recordsLinked to original sources

arXiv2025

Pauli spin blockade at room temperature in double-quantum-dot tunneling through individual deep dopants in silicon

Pauli spin blockade (PSB) is a spin-dependent charge transport process that typically appears in double quantum dot (QD) devices and is employed in fundamental research on single spins in nanostructures to read out semiconductor qubits. The operating temperature of PSB is limited by that of the QDs and remains below 10 K, limiting wide application development. Herein, we confirm that a single deep dopant in the channel of a silicon field effect transistor functions as a room-temperature QD; consequently, transport through two different deep dopants exhibits PSB up to room temperature. The characteristic magnetoconductance provides a means to identify PSB and enables the PSB device to function as a magnetic sensor with a sensitivity below geomagnetic field. Lifting in PSB caused by magnetic resonance (50 K) and Rabi oscillations (10 K) are also observed. Further development of this unique system may lead to room-temperature quantum technologies based on silicon technology.

cond-mat.mes-hall↗

arXiv2022

Introduction of deep level impurities, S, Se, and Zn, into Si wafers for high-temperature operation of a Si qubit

To realize high-temperature operation of Si qubits, deep impurity levels with large confinement energy, which are hardly thermally excited, have been introduced into Si wafers. Group II impurity Zn and group VI impurities S and Se, which are known to form deep levels, were introduced into the Si substrates by ion implantation. These samples were analyzed for concentration-depth profiles, energy level depths, and absence of defects. To introduce deep impurities into thin channels such as 50-nm-thick Si, we found impurity introduction conditions so that the concentration depth profiles have maximum value at less than 50 nm from the Si surface. Then, the formation of the deep levels and absence of defects were experimentally examined. By using the conditions to introduce deep impurities into Si wafer obtained from the experiments, single-electron transport at room temperature, high-temperature operation of qubit, and room-temperature quantum magnetic sensors are promising.

cond-mat.mtrl-sci↗

arXiv2020

First-principles calculation study on the stabilities of the (100) and (111) surfaces of boron-doped diamond

Boron-doped diamond (BDD) has attracted much attentions in semi-/super-conductor physics and electrochemistry, where the surface structures play crucial roles. Herein, we systematically re-examined the probable surface reconstructions of the bare and H-terminated BDD(100) and (111) surfaces by using density functional theory (DFT). For the optimized structures, we performed STM image simulations based on Tersoff-Hamman scheme and calculations of the projected density of states. We found that: on the BDD(100), the p(2x1) reconstruction has lowest energy and the c(2x2) reconstruction has 0.1673 eV/surface-atom energy higher; On the BDD(111), the ideal (1x1) has lowest energy, the single chain SC-(2x1) and Pandey chain PC-(2x1) have 0.3415 eV/surface-atom and 0.6576 eV/surface-atom higher energy, respectively. The BDD(111) appears to have more reconstructions than the BDD(100) which supports to the idea that the BDD(111) is more electrochemically reactive than the BDD(100). In addition, we study the impact of the Boron dopant on the surface states of the BDD(111) and suggest the Boron-enhanced graphitization on the BDD(111). The results give an insight into the surface stability of the BDD.

cond-mat.mtrl-sci↗