Macromolecular nanoelectronics

We have explored new organic materials and fabrication methods to fabricate organic photodiodes and light emitting diodes. Grafting of a fullerene derivative to a polythiophene backbone yielded an integrated acceptor-donor polymer that we used as the active material in organic photodiodes. Using a method of soft lithography, soft embossing, we fabricated submicron structures to be used as organic light emitting diodes. Employing a silicone rubber replica (stamp) of an optical diffraction grating we transferred the grating pattern to an organic resist layer by placing the stamp in conformal contact with the resist. The transferred pattern was subsequently used as an etch mask for the processing of the device. The structures were successfully utilized as light emitting diodes and photodiodes, with device characteristics influenced by the imposed structure.     

Electron spectroscopy … for chemical analysis

There are several characteristics of ESCA which make it useful for chemical analysis. First, it is sensitive to nearly all elements in the periodic tab     

Electron spectroscopy of iron disilicide

We have reported on the results of a complex investigation of iron disilicide FeSi₂ using characteristic electron energy loss spectroscopy, inelastic electron scattering cross section spectroscopy, and X-ray photoelectron spectroscopy. It has been shown that the main peak in the spectra of inelastic electron scattering for FeSi₂ is a superposition of two unresolved peaks, viz., surface and bulk plasmons. An analysis of the fine structure of the spectra of inelastic electron scattering cross section by their decomposition into Lorentzlike Tougaard peaks has made it possible to quantitatively estimate the contributions of individual energy loss processes to the resulting spectrum and determine their origin and energy.     

NEMS/MEMS tools for nanoelectronics development

Present information technologies use semiconductor devices and magnetic/optical discs, however, they are all foreseen to face fundamental limitations within a decade. Therefore, superseding devices are required for the next paradigm of high performance information technologies. This paper describes prospects for single molecule devices suitable for future information processing technologies. Possible four milestones for realizing the Peta (P: 10¹⁵)/Exa (E: 10¹⁸)––floating operations per second (FLOPS) personal molecular supercomputer are proposed. Current status and necessary technologies of the first milestone are described, and necessary technologies for the next three milestones are also discussed.     

Surface passivation technology for III-V semiconductor nanoelectronics

The present status and key issues of surface passivation technology for III-V surfaces are discussed in view of applications to emerging novel III-V nanoelectronics. First, necessities of passivation and currently available surface passivation technologies for GaAs, InGaAs and AlGaAs are reviewed. Then, the principle of the Si interface control layer (ICL)-based passivation scheme by the authors’ group is introduced and its basic characterization is presented. Ths Si ICL is a molecular beam epitaxy (MBE)-grown ultrathin Si layer inserted between III-V semiconductor and passivation dielectric. Finally, applications of the Si ICL method to passivation of GaAs nanowires and GaAs nanowire transistors and to realization of pinning-free high-k dielectric/GaAs MOS gate stacks are presented.     

Electron spectroscopy of fluoridated fullerene films

The chemical and energy structures of highly fluoridated fullerene films have been investigated. Analysis of the complex structure of carbon 1s spectra showed the presence of C-F and C-F2 fragments as well as nonfluoridated carbon atoms with an overwhelming quantity of C-F bonds. The band gap in fluoridated-fullerene and its films was estimated to be 8.0 eV and energy loss on an interband transition at 11 eV was also observed. Comparison of the valence-band spectra of the experimental samples showed that the valence band of fluoridated fullerenes is divided into anionic and cationic parts (similarly to alkali-halide crystals) and suggests that fluoridated fullerenes possess the corresponding properties, making it possible to find new materials with wide practical applications. Fiz. Tverd. Tela (St. Petersburg) 40, 168–172 (January 1998)     

Electron momentum spectroscopy of NF3

The electronic structure of nitrogen trifluoride was investigated by combining the high-resolution electron momentum spectroscopy with the high-level calculations. The experimental binding energy spectra and the momentum distributions of each orbital were compared with the results of Hartree-Fock, density functional theory （DFT）, and symmetry-adapted- cluster configuration-interaction （SAC-CI） methods. SAC-CI and DFT-B3LYP with the aug-cc-pVTZ basis set can well reproduce the binding energy spectra and the observed momentum distributions of the valence orbitals except 1 a2 and 4e orbitals. It was found that the calculated momentum distributions using DFT-B3LYP are even better than those using the high-level SAC-CI method.     

Physical fault tolerance of nanoelectronics

The error rate in complementary transistor circuits is suppressed exponentially in electron number, arising from an intrinsic physical implementation of fault-tolerant error correction. Contrariwise, explicit assembly of gates into the most efficient known fault-tolerant architecture is characterized by a subexponential suppression of error rate with electron number, and incurs significant overhead in wiring and complexity. We conclude that it is more efficient to prevent logical errors with physical fault tolerance than to correct logical errors with fault-tolerant architecture.     

Electron spin-echo spectroscopy at 95 GHz

An electron spin-echo spectrometer operating at 94.9 GHz is described. The experimental details of the microwave circuit are discussed and the performance is compared with that of more conventional spectrometers at 9.5 GHz.     

Electron energy-loss spectroscopy applied to solids

Several illustrating examples of recent electron energy-loss investigations of the electronic structure of solids are reviewed. In particular, studies on rare-gas bubbles in metals, on conducting polymers, and onL _2,3 edges of 3d transition metals are reported. Moreover, the electron energy-loss spectrometer, which was used for these investigations, is described briefly.     

Electron spectroscopy of chemically synthesized ZnS clusters

Thin films of ionic compounds of ZnS clusters were measured by electron energy loss spectroscopy (EELS) and ultraviolet photoelectron spectroscopy (UPS). A size effect was observed in the valence plasmon energy measured by EELS from which the coherence length of the plasmon excitation can be estimated. The difference between the lowest excitations observed in UPS and EELS can be explained by the final state charging effect of a single cluster ion in UPS, which strongly depends upon the nominal charges of the clusters.     

Plasma-produced ultra-thin platinum-oxide films for nanoelectronics: physical characterization

We present a detailed experimental characterization of ultra-thin platinum-oxide films formed on metallic Pt surfaces using O₂ plasma treatment. A monotonic consumption of the metallic Pt by the O₂ plasma is demonstrated by electrical resistance measurements of micron-wide, ultra-thin metallic Pt wires for the range of O₂ plasma exposure times explored in this study. Conversely, angle-resolved X-ray photoelectron spectroscopy (AR-XPS) of the plasma-treated Pt reveals that the oxide layer formed on the Pt surface maintains a constant thickness over these exposure times. In combination, these data demonstrate that the O₂ plasma treatment of Pt simultaneously forms and etches an ultra-thin platinum-oxide layer on the Pt surface. In addition, the AR-XPS data also reveals the oxide layer to be composed of two different platinum–oxygen compounds. Detailed analysis demonstrates a stratified structure for the ultra-thin platinum oxide, with the oxide bulk being composed of PtO₂, likely with PtO defects, and the exposed oxide surface being Pt(OH)_y2 terminated after exposure to ambient conditions. The potential utility of using plasma oxidization to form ultra-thin platinum (or other metal) oxide films on nanoscale metal structures for nano- and molecular-electronic applications is discussed, along with other promising applications in technologies such as sensors and catalysts. PACS 61.43.Dq; 68.47.Gh; 68.55.Ac; 68.55.Jk; 73.50.Bk; 73.61.At; 73.63.Nm; 79.60.Dp     

Multidimensional spectroscopy of cascades of photons emitted by quantum objects

In the paper we describe the capabilities of the multidimensional (multidetector) spectroscopy of photon cascades. Attention is paid to a considerable increase in the resolution of multidetector spectrometers compared to one-detector spectrometers. We give a derivation of the radiation intensity detection limit, which relates all the basic characteristics of a multidetector spectrometer, and present examples of calculation of spectrometer characteristics. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 2, pp. 278–283, March–April, 1998.     

Plasma synthesis of semiconductor nanocrystals for nanoelectronics and luminescence applications

Functional nanocrystals are widely considered as novel building blocks for nanostructured materials and devices. Numerous synthesis approaches have been proposed in the solid, liquid and gas phase. Among the gas phase approaches, low pressure nonthermal plasmas offer some unique and beneficial features. Particles acquire a unipolar charge which reduces or eliminates agglomeration; particles can be electrostatically confined in a reactor based on their charge; strongly exothermic reactions at the particle surface heat particles to temperatures that significantly exceed the gas temperature and facilitate the formation of high quality crystals. This paper discusses two examples for the use of low pressure nonthermal plasmas. The first example is that of a constricted capacitive plasma for the formation of highly monodisperse, cubic-shaped silicon nanocrystals with an average size of 35 nm. The growth process of the particles is discussed. The silicon nanocubes have successfully been used as building blocks for nanoparticle-based transistors. The second example focuses on the synthesis of photoluminescent silicon crystals in the 3–6 nm size range. The synthesis approach described has enabled the synthesis of macroscopic quantities of quantum dots, with mass yields of several mg/hour. Quantum yields for photoluminescence as high as 67% have been achieved.     

Electron momentum spectroscopy of valence satellites of neon

Electron momentum spectroscopy (EMS) study of the neon valence satellites is reported. The experiments were performed at impact energies of 1250, 1450 and 1670 eV using a multichannel spectrometer that features high sensitivity. Binding energy spectra up to 100 eV and momentum profiles for the 2p⁻¹ and 2s⁻¹ primary transitions as well as the satellites are presented. The results are used to examine impact energy dependence of the relative intensities and shapes of the satellite momentum profiles. The results are also used to determine symmetries and spectroscopic factors of the satellites, and are compared with the previous experiments by EMS and photoelectron spectroscopy and sophisticated theoretical calculations. The present study has largely resolved controversies in the previous studies.     

Electron spectroscopy of autoionizing states of nitrogen atoms

During excitation of N₂, NO and N₂O molecules by fast neutral 1¹S helium atoms, highly excited molecular states are formed which yield, through predissociation, autoionizing nitrogen atoms. The energy of electrons released in autoionization was measured and the energy and plausible spectroscopic assignment of autoionizing levels was determined. The excited levels belong to Rydberg series converging to the N⁺(¹D) series limit. Besides molecular states derived by correlation of the final atoms, highly excited molecular parent states are also discussed.