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The single-charge transfer operation in two-dimensional (2D) random-multidot channel field-effect transistor (FETs) using orthodox theory of the Coulomb blockade phenomenon is numerically studied. It is found that the turnstile operation meaning that electrons are transferred one by one could be performed in the 2D multidot circuit by applying an alternating V(sub g).

Silicon/edge-oxide/polysilicon tunnel devices using a very thin silicon-on-insulator film as a cathode were fabricated to study the electron tunneling properties of nanometer-scale silicon. To this end, the tunneling current from the edge of the 5-nm-thick SIMOX-silicon layers was measured in terms of the polysilicon front gate bias. The results indicated that a positive bias at the front induces the current-gate voltages characteristics to exhibit a steplike behavior.

Abstract Silicon field-effect transistors have now reached gate lengths of only a few tens of nanometers, containing a countable number of dopants in the channel. Such technological trend brought us to a research stage on devices working with one or a few dopant atoms. In this work, we review our most recent studies on key atom devices with fundamental structures of silicon-on-insulator MOSFETs, such as single-dopant transistors, preliminary memory devices, single-electron turnstile devices and photonic devices, in which electron tunneling mediated by single dopant atoms is the essential transport mechanism. Furthermore, observation of individual dopant potential in the channel by Kelvin probe force microscopy is also presented. These results may pave the way for the development of a new device technology, i.e., single-dopant atom electronics.

We present the density functional theory calculations of the binding energy of the Phosphorus (P) donor electrons in extremely downscaled single P-doped Silicon (Si) nanorods. In past studies, the binding energy of donor electrons was evaluated for the Si nanostructures as the difference between the ionization energy for the single P-doped Si nanostructures and the electron affinity for the undoped Si nanostructures. This definition does not take into account the strong interaction of donor electron states and Si electron states explicitly at the conductive states and results in a monotonous increase in the binding energy by reducing the nanostructure's dimensions. In this paper, we introduce a new approach to evaluate the binding energy of donor electrons by combining the projected density of states (PDOS) analysis and three-dimensional analysis of associated electron wave-functions. This enables us to clarify a gradual change of the spatial distribution of the 3D electron wavefunctions (3DWFs) from the donor electron ground state, which is fully localized around the P donor site to the first conductive state, which spreads over the outer Si nanorods contributing to current conduction. We found that the energy of the first conductive state is capped near the top of the atomistic effective potential at the donor site with respect to the surrounding Si atoms in nanorods smaller than about 27 a0. This results in the binding energy of approximately 1.5 eV, which is virtually independent on the nanorod's dimensions. This fact signifies a good tolerance of the binding energy, which governs the operating temperature of the single dopant-based transistors in practice. We also conducted the computationally heavy transmission calculations of the single P-doped Si nanorods connected to the source and drain electrodes. The calculated transmission spectra are discussed in comparison with the atomistic effective potential distributions and the PDOS-3DWFs method. [ABSTRACT FROM AUTHOR]

We have studied single-electron turnstile operation in common-gated one-dimensional arrays of four tunnel junctions (three dots) having inhomogeneous junction capacitances. Analytical calculations show that the source-drain voltage range with a current plateau due to single-electron turnstile operation is increased when the outer two tunnel capacitances are adjusted to be smaller than the inner ones. In fact, we have demonstrated in phosphorous-doped silicon-on-insulator field-effect transistors (FETs) that back-gate voltage works to assist the turnstile operation, which is primarily ascribed to electrical control of junction capacitance dispersion, i.e., reduction in outer junction capacitances. As a result, postfabrication control of capacitance dispersion in multijunction FETs can be achieved, resulting in successful turnstile operation. [ABSTRACT FROM AUTHOR]

Effect of nanometer-scale corrugation on gap state and fixed charge densities at the SiO[sub 2]/Si interface in Si (001) metal-oxide-semiconductor (MOS) capacitors has been studied by capacitance-voltage (C-V) and conductance-voltage (G/ω-V) measurements. As the interface corrugation, a high density of Si protrusions, composed of a microscopic (001) plane at the top and high-index planes [typically (115) planes] at the sides, were formed by a microscopic selective oxidation technique developed by the authors. By changing the selective oxidation condition, the area ratio of the top and side planes was varied. As a result, it was found that each of C-V and G/ω-V curves showed a mixture of two curves with different flatband voltages. This reflects that the interface fixed charge density at the side high-index planes is larger than that at the top (001) plane, similar to previous reports for classical MOS capacitors with a macroscopic flat interface. Furthermore, it was found that the side high-index interface has a higher gap state density than the top (001), also similar to the previous macroscopic results. Such orientation dependence of gap state and fixed charge densities in the nanometer regime will play a significant role in electrical properties of ultrasmall Si devices, which accompany a relatively large area of curved interfaces. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]