The epitaxial growth of artificial two-dimensional metals at interfaces plays a key role in fabricating heterostructures for nanoelectronics. Here, we present the growth of bismuth nanostructures on highly oriented pyrolytic graphite (HOPG) under ultrahigh vacuum (UHV) conditions, which was investigated thoroughly by a combination of scanning tunneling microscopy (STM), ultraviolet photoemission spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS), and low energy electron diffraction (LEED). It was found that (111)-oriented bilayers are formed on as-cleaved high-quality HOPG at 140 K, which opens the possibility of making Bi(111) thin films on a semimetal, and this is a notable step forward from the earlier studies, which show that only Bi(110) facets could be formed at ultrathin thickness at room temperature. XPS investigation of both C 1s and Bi 4f reflects the rather weak bonding between the Bi film and the HOPG substrate and suggests a quasi layer-by-layer growth mode of Bi nanostructures on HOPG at low temperature. Moreover, the evolution of the valence band of the interface is recorded by UPS, and a transition from quantum well states to bulk-like features is observed at varying film thickness. Unlike semimetallic bulk bismuth, ultrathin Bi(111) films are expected to be topological insulators. Our study may therefore pave the way for the generation of high quality Bi nanostructures to be used in spin electronics.

MV switchgear experiences a rise in temperature during normal operation due to ohmic losses in conductors and contacts. If the temperature rise is too high, the switching device may be degraded. The focus of this paper is to find a value for the total heat transfer coefficient that may be applied to estimate the temperature of critical parts (open/close contact) of the load break switch in an enclosed MV switchgear, relative to the surrounding air (inside the enclosure) for future design. The values for the total heat transfer coefficient (including all transfer mechanisms) showed a relatively strong dependence on the surface emissivity and the actual design of the switch, but was less dependent on temperature changes within the relevant temperature range. Based on our findings, it is reasonable to assume that the total heat transfer coefficients may be applied in a first approximation of the temperature rise of a load break switch contacts relative to the surrounding air inside an enclosure. Further refinement could be obtained by taking the actual design of the switch into consideration, especially details influencing the emissivity and design elements influencing the heat conduction to adjacent conductor parts.

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SF6 is used as an insulation and interruption medium in medium-voltage (MV) gas-insulated switchgear (GIS), but has a very high global warming potential. In recent years, several environmentally-friendly (eco-efficient) alternatives have been explored, focusing on dielectric and thermal properties. The interruption of low currents in MV application is emerging as an important topic for equipment manufacturers and users. The reduced arcquenching properties of the most prominent eco-efficient alternatives may require the use of vacuum interrupters for simple load current interruptions. However, this may not be a cost-effective solution and simpler interruption principles are desirable. In this paper, we explore low-current interruption in AirPlus TM , a m i x t u r e o f d r y a i r a n d t h e C 5 F 10O fluoroketone (C5-FK) as well as mixtures of CO2 and C5-FK. We find that it is possible to achieve the E3 electrical endurance class (100 c/o) with a switch based on the puffer principle in AirPlus with a condensation temperature of-25˚C, suitable for secondary distribution MV GIS. The chemical analysis of gas samples taken from the switchgear after 100 successful interruptions indicate only trace amounts of fluoroketone decomposition products.

Training and recovery of exchange bias in FeNi/Cu/Co/FeMn spin valves have been studied by magnetoresistance curves with field sweep rates from 1000 to 4800 Oe/s. It is found that training and recovery of exchange field are proportional to the logarithm of the training cycles and recovery time, respectively. These behaviours are explained within the model based on thermal activation. For the field sweep rates of 1000, 2000 and 4000 Oe/s, the relaxation time of antiferromagnet spins are 61.4, 27.6, and 11.5 in the unit of ms respectively, much shorter than the long relaxation time (∼ 10 2 s) in conventional magnetometry measurements.