RESUMO
Single electron transport through multiple quantum levels is realized in a Si quantum-dot device at room-temperature conditions. The energy spacing of more than triple the omnipresent thermal energy is obtained from an extremely small ellipsoidal Si quantum dot, and high charge stability is attained through a construction of the gate-all-around structure. These properties may move us a step closer to practical applications of quantum devices at elevated temperatures. An in-depth analysis on the transport behavior and quantum structure is presented.
RESUMO
Ferroelectric memory devices are expected for low-power and high-speed memory applications. HfO2-based ferroelectric is attracting attention for its CMOS-compatibility and high scalability. Mesoscopic-scale grains, of which size is almost comparable to device size, are formed in HfO2-based ferroelectric poly-crystalline thin films, which largely influences electrical characteristics in memory devices. It is important to study the impact of mesoscopic-scale grain formation on the electrical characteristics. In this work, first, we have studied the thickness dependence of the polarization switching kinetics in HfO2-based ferroelectric. While static low-frequency polarization is comparable for different thickness, dynamic polarization switching speed is slower in thin Hf0.5Zr0.5O2 (HZO) capacitors. Based on the analysis using the NLS model and physical characterization, thinner HZO contains smaller grains with orientation non-uniformity and more grain boundaries than thicker HZO, which can impede macroscopic polarization switching. We have also theoretically and experimentally studied the polar-axis alignment of a HfO2-based ferroelectric thin film. While in-plane polar orientation is stable in as-grown HZO, out-of-plane polarization can be dominant by applying electric field, which indicates the transition from in-plane polar to out-of-plane polar orientation in the ferroelectric phase grains. This is confirmed by calculating kinetic pathway using ab-initio calculation.
RESUMO
Reconfigurable multivalue logic functions, which can perform the versatile arithmetic computation of weighted electronic data information, are demonstrated at room temperature on an all-around-gate silicon ellipsoidal quantum-dot transistor. The large single-hole transport energy of the silicon quantum ellipsoid allows the stable M-shaped Coulomb blockade oscillation characteristics at room temperature, and the all-around-gate structure of the fabricated transistor enables us to perform the precise self-control of the energetic Coulomb blockade conditions by changing the applied bias voltage. Such a self-controllability of the M-shaped Coulomb blockade oscillation characteristics provides a great advantage to choose multiple operation points for the reconfigurable multivalue logic functions. Consequently, the weighted data states (e.g., tri-value and quattro-value) are effectively demonstrated by utilizing only the device physics in the all-around-gate silicon ellipsoidal quantum-dot transistor. These findings are of great benefit for the practical application of the silicon quantum device at an elevated temperature for future nanoelectronic information technology.