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Transport behaviors and mechanisms in cuspidal blockade region for silicon single-hole transistor
이영민,이세준,Toshiro Hiramoto 한국물리학회 2014 Current Applied Physics Vol.14 No.3
The Si single-hole transistor displays the anomalously-extended cuspidal blockade region, which is elongated toward the 45-tilted direction normal to gate vs. drain bias voltage regions in the Coulomb blockade diagram. This is attributed to the formation of an ultra small Si quantum dot (QD) into the gateall- around (GAA) stack. Namely, the large one-electron-addition energy (¼ 447 meV) from the 2-nm-size Si QD enables the clear Coulomb-blockade events at room temperature, and the large voltage gain from the GAA stack allows the cuspidal extension of the blockade region through the renormalization of Coulomb-blockade energies at the adjacent bias points near the initial Coulomb-blockade state.
Velocity Saturation Effects in a Short Channel Si-MOSFET and its Small Signal Characteristics
황상훈,Hyunsik Im,송민규,Koichi Ishida,Toshiro Hiramoto,Takayasu Sakurai 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.2
We fabricated a Si Metal Oxide Semiconductor Field Effect Transistor with a 0.18 μm gate length and analyzed its transport considering the velocity saturation effect. We found that the saturation current (Idsat) transport shows a fractional power dependence on the gate voltage (Vgs), namely, it follows the α-power law MOSFET model, Idsat = B×(Vgs −VTH)α. The main model parameters α and B were extracted from the measured Idsat−Vgs characteristics. The value of α was around 1.6. The channel length modulation factor (λ) and gate trans-conductance (gm) were investigated as functions of Vgs. We also present the small signal characteristics by using a simple analog amplifier circuit consisting of one transistor and one resistor, demonstrating that a small signal can be well modeled by using the α-power law MOSFET model.
Lee, Sejoon,Lee, Youngmin,Song, Emil B.,Hiramoto, Toshiro American Chemical Society 2014 NANO LETTERS Vol.14 No.1
<P>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.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2014/nalefd.2014.14.issue-1/nl403204k/production/images/medium/nl-2013-03204k_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl403204k'>ACS Electronic Supporting Info</A></P>
Kobayashi Masaharu,Wu Jixuan,Sawabe Yoshiki,Takuya Saraya,Hiramoto Toshiro 나노기술연구협의회 2022 Nano Convergence Vol.9 No.50
Ferroelectric memory devices are expected for low-power and high-speed memory applications. HfO 2 -based fer- roelectric 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 HfO 2 -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 HfO 2 -based ferroelectric. While static low-frequency polarization is comparable for different thickness, dynamic polarization switching speed is slower in thin Hf 0.5 Zr 0.5 O 2 (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 HfO 2 -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.