On low-field electron emission mechanisms

It is established by direct experiments that the main component of the stationary field-emission current in fields E<10⁵ V/cm is due to piezogeometric intensification (by a factor of 10³) of the electricfield at the end faces of piezoelectrically active films. An emission mechanism governed by electrons supplied by tunneling from the valence band of the piezoelectric is proposed. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 11, 823–827 (10 June 1997)     

Field and photo-field electron emission from self-assembled Ge–Si nanostructures with quantum dots

Monolayer and multilayer Ge nanocluster structures were prepared on Si(1 0 0) using molecular beam epitaxy. The cluster size was 10 nm and cluster density was 10¹⁰ cm⁻². A stable field electron emission was obtained from these structures, showing current peaks in the current–voltage characteristics, which may be attributed to the resonant electron tunneling via the energy levels of the nanocluster potential well. For cluster multilayers, the current–voltage curves also showed current peaks with a complex shape. The cluster multilayer structures had a considerable temperature sensitivity, as well as photosensitivity, in the wavelength range from 0.4 to 10 μm.     

Quantized field-electron emission at 300 K in self-assembled arrays of silicon nanowires

Dense ensembles of silicon nanowires were prepared by metal-catalyzed chemical vapor deposition on silicon substrates. Some of these ensembles were doped with phosphorous during growth. The nanowires were characterized using scanning electron microscopy, X-ray diffraction, and mass spectroscopy. Field emission of electrons from these structures was studied at room temperatures in ultra-high vacuum. The measurements were carried out using a parallel-plate diode cell. At high-applied fields, the current–voltage characteristics deviate from the Fowler–Nordheim law and exhibit a step-wise increase in the current with the increasing voltage at 300 K. Possible mechanisms of the observed quantized field emission are discussed.     

Aspect-ratio dependent oscillatory thermocapillary convection in the floating half zone

The dependency of the critical Marangoni number on the geometrical aspect ratio of the floating half zone is essential to predict the onset of oscillatory thermocapillary convection.The experimental studies in the microgravity conditions on floating half zones of several centimeters in diameter have predicted that the critical Marangoni number increases with the increasing aspect ratio,and the terrestrial experimental studies have predicted the contradictory conclusion for floating half zones of several mil...     

Non-Gravitational Effects with Density-Matching in Evaluating the Influence of Sedimentation on Colloidal Coagulation

The method of density matching between the solid and liquid phases is often adopted to effectively eliminate the effect of sedimentation of suspensions in studies on dynamic behaviour of a colloidal system. However, the associated changes in the solvent composition may bring side effects to the properties investigated and therefore might lead to a faulty conclusion if the relevant correction is not made. To illustrate the importance of this side effect, we present an example of the sedimentation influence on the coagulation rate of suspensions of 2μm （diameter） polystyrene. The liquid mixtures, in the proper proportions of water （H2O）, deuterium oxide （D2O） and methanol （MeOH） as the liquid phase, density-matched and unmatched experiments are performed. Besides the influence of viscosity, the presence of methanol in solvent media, used to enhance the sedimentation effect, causes significant changes （reduction） in rapid coagulation rates compared to that in pure water. Without the relevant corrections for those non-gravitational factors it seems that gravitational sedimentation would retard the coagulation. The magnitude of the contribution from the non-gravitational factor is quantitatively determined, making the relevant correction possible. After necessary the influence of the sedimentation on coagulation rates at corrections for all factors, our experiments show that the initial stage of the coagulation is not observable.     

Single and multiple muons and the generation of neutrons in the LVD experiment

The large geometric factor and good spatial resolution of the Large Volume Detector (LVD) ensures statistically significant and highly accurate measurements of muon trajectories and determination of the multiplicity of muon groups. The developed algorithm allows us to reconstruct 2 × 10⁶ muon events (single muons and muon groups). Characteristics of muon groups are obtained and the specific yield of neutrons produced by single muons, muon groups, and showers is determined.     

Results of the liquid scintillation detector of the Mont Blanc Laboratory

Summary The Liquid Scintillation Detector (LSD experiment) is running since October 1984 in the Mont Blanc Laboratory, with 90 tons of active mass. We discuss here some of the research aims of the experiment, and report the preliminary results on searching for neutrino bursts from collapsing stars and on cosmic-ray muons.

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Riassunto Nell'ottobre 1984 è entrato in misura l'esperimento LSD (Liquid Scintillation Detector) del Laboratorio del Monte Bianco, costituito di 90 tonnellate di rivelatore. In questo lavoro si discutono alcuni degli argomenti di ricerca dell'esperimento e si riportano i risultati preliminari sui burst di neutrini da collassi stellari e sui muoni della radiazione cosmica.

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Резюме Зидкий сцинтилляционный детектор работает с октября 1984 года в лаборатории на Мон Блане. Детектор имеет 90 тонн активной массы. Мы обсуздаем некоторые цели этого эксперимента. Сообщаются предварительные результаты по поиску нейтринных вспышек от коллапсирующих звезд и мюонов в космических лучах.