Femtosecond laser writing of buried graphitic structures in bulk diamond

Diamond samples are irradiated with 140fs pulses of 800nm wavelength. The pulse repetition rate is 1kHz. In the focal region of the irradiated pulses the diamond is transformed to graphite. The writing of graphitic wires along the incident beam is studied experimentally. Atechnique to produce buried graphitic wires with constant diameter is described. Diameters can be selected between 1.5μm and 10μm. The wire length is up to 680μm. The writing speed is typically between 1μm s−1 and 30μm s−

Public Private Partnership in Social Sphere: Models Review

Growing social pressure on economy is a global trend nowadays due to constant increase of elderly population not accompanied by respective world economy growth. One of ways to respond to global challenges became new model of social & infrastructure investments called Public Private Partnership. In this article authors analyze specifics of Public Private Partnerships in social sphere and reasons why they came up to the world's agenda. Such areas as health protection, sports, education, culture, utilities are treated as social. Main goal of majority of partnerships is social as well and due to this such projects have low income rates and high risks associated. Nevertheless, in the article models of effective Public Private Partnerships are illustrated and analyzed in depth. The most promising models out of all options are selected and conclusion for the need of special tax regulation for the PPP projects is made. Keywords: problem of elderly population, effective models of social investments, Public Private Partnership (PPP) JEL Classifications: H51, H53, H54, M14, M2

Editorial

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Electronic performance of 2D-UV detectors

With the aim of contributing to the development of two-dimensional UVand X-ray detectors, also stimulated to evaluate specific amplification, handling and addressing electronics, we present a 16-pixel matrix sensor based on high quality polycrystalline diamond. Thick polycrystalline diamond specimens, in the 0.2–0.6 mm range, have been used for the tests and the development of the prototype. Crossed 1 mm large chromium strips have then been realized by lithography on the metal deposited on both the two sample surfaces. The single pixel structure of a matrix appears like a metal-diamond-metal vertical device with a volume which is directly related to the diamond thickness (0.2–0.6 mm3). Initially, to evaluate the sensor-grade quality of the diamond films, each pixel has been characterized by means of: I–V characteristic in the dark and under ns pulsed excimer laser irradiation; linearity with the photon flux; spectral photoresponse in the 200–1000 nm range. The lateral charge collection at the non-illuminated sensing elements has also been measured to estimate the cross-talk between pixels. Successive tests have been devoted to study the whole matrix response by addressing the pixels singly through the realized electronics both in CW and chopped monochromatic UV illumination. The implemented low-noise transimpedance amplifiers (1 V/1 nA) showed a good linearity whereas the bandwidth was limited just to 20 Hz. Finally, the intensity distribution of a 1×

Surface Channel MESFETs on Hydrogenated Diamond

Metal–semiconductor field effect transistors (MESFETs) based on hydrogen terminated diamond were fabricated according to different layouts. Aluminum gates were used on single crystal and low-roughness polycrystalline diamond substrates while gold was used for ohmic contacts. Hydrogen terminated layers were deeply investigated by means of Hall bars and transfer length structures. Room temperature Hall and field effect mobility values in excess of 100 cm2 V1 s1 were measured on commercial and single crystal epitaxial growth (100) plates by using the same hydrogenation process. Hydrogen induced two-dimensional hole gas resulted in sheet resistances essentially stable and repeatable depending on the substrate quality. Self-aligned 400 nm gate length FETs on single crystal substrates showed current density and transconductance values >100 mA mm1 and >40 mS mm1, respectively. Devices with gate length LG D 200 nm showed fMax D 26:4 GHz and fT D 13:2 GHz whereas those fabricated on polycrystalline diamond, with the same gate geometry, exceeded fMax D 23 GHz and fT D 7 GHz. This work focused on the optimization of a self-aligned gate structure with respect to the fixed drain-to-source structure with which we observed higher frequency values; the new structure resulted in improvement of DC characteristics, better impedance matching and a reduction in the fMax=fT ratio