lecture1casgs-納米科學概論(參考版)
2025-05-14 18:20本頁面
【正文】 MOS EF 反相層 低維電子系統(tǒng)制備與輸運實驗 Further confinement to 2DEG ? 1DEG (Qwire) ? 0D (QD) Quantum pointcontact 量子觸點 Conductance through a short wire or constriction (quantum point contact) between two leads of 2DEG Quantized conductance as a function of gate voltage Vg Ntrans can be changed by varying splitgate bias Vg Classical effect in transport through nanoparticles: Coulomb blockade Coupling of QD to external world Weak coupling: the number of electrons located at the QD is well defined Coulomb repulsion energy between electrons in a QD of size a: ( n m ) ( e V ) 4~ 02aaeErrC ???? ?The discrete nature of electron charge bees strongly evident when EC ? kBT. For ?r ? 5, T = 300 K, this occurs at a ? 10 nm Coulomb blockade: one electron located on a QD creates an energy barrier to stop the further transfer of electrons onto the QD Classical effect in transport through nanoparticles: Coulomb blockade Furthermore, the charging energy can stop any electron jumping on a QD Electrostatic energy stored in this capacitor is: CQE 2 2?Capacitance for observing Coulomb blockade at RT: C ~ 3 1018 F Spherical QD of radius a at a distance l (a) above a ground plane, the capacitance of this system: 04 (1 )2raCa l? ? ?? ? ?For typical semiconductors, ?r ~ 10, a ~ nm at RT Energy diagram of a doublejunction QD structure with Coulomb blockade In equilibrium Under an applied bias Experimental (A) and theoretical (B and C) IV curves of a STM tip/10nm In island/AlOx film/Al substrate When e/2C Va 3e/2C, maximum occupation number of QD is n = 1 ? one electron at a time jump through QD ? current is nearly a constant Single electron transistor (SET) Third electrode gate to adjust QD potential independently Another version of SET VG = V0 + V1 cos(2?ft) I = ef, SET can be used as a current standard Application example of SET: 參考文獻 1. P. Moriarty, Nanostructured materials, Rep. Prog. Phys. 64, 297 (2021). 2. G. Timp (ed), Nanotechnology (Springer, New York, 1999). 3. Hari Singh Nalwa (ed), Nanostructured materials and nanotechnology (Academic Press, London, 2021). 4. For 2021 International Technology Roadmap for Semiconductors (ITRS), see website 5. The Royal Society, Nanoscience and nanotechnologies: opportunities and
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