Radijacioni efekti u superizolatorima

Abstract

Superprizolatorsko stanje je po prvi put eksperimentalno uoceno pre svega nekoliko godina. Za elektrotehnicke primene, najznacajnija osobina superizolatora je beskonacna elektricna otpornost. Superizolatorsko stanje moguce je shvatiti kao dualno superprovodnom, pri cemu oba opstaju samo do odredenih kriticnih vrednosti ista tri parametra: temperature, primenjenog napona i jacine magnetnog polja. Moguce primene superizolatora su za izolaciju kablova (pogotovo superprovodnih kablova, cija konstrukcija podrazumeva hladenje do niskih temperatura na kojima se održavaju i superprovodno i superizolatorsko stanje), galvanskih elemenata (cime bi gubici usled struja curenja mogli da se svedu na zanemarljiv nivo) i komponenti u tehnologiji integrisanih kola (što bi omogucilo izradu znatno tanjih dielektricnih slojeva). Nakon razmatranja opštih karakteristika izolatorskih materijala i osobina superprovodnog stanja, u radu je dat opis mikroskopskih i makroskopskih karakteristika superizolatorske faze. Detaljno su razmotreni efekti zracenja na materijale, u zavisnosti od vrste zracenja i osobina materijalne sredine kroz koju ono prolazi. Posebna pažnja posvecena je interakciji zracenja sa izolatorskim materijalima, sa naglaskom na radijaciona oštecenja u cvrstim izolatorima. Izloženi su principi Monte Carlo metoda simulacije prolaska zracenja kroz materijal, koje se zasnivaju na numerickoj simulaciji slucajnih velicina na osnovu poznatih raspodela. Prikazani su rezultati numerickih simulacija dejstva zracenja na analizirane superizolatorske filmove, kojim su obuhvaceni gubici energije upadnog zracenja putem jonizacije, fononskog pobudivanja rešetke i izmeštanja atoma materijala. Numericka simulacija sporvedena u radu dovedena je u vezu sa teorijskim modelom superizolatorske faze, uzimajuci u obzir sve specificnosti ovog stanja. Uoceno je da svaki od tri vida deponovanja energije zracenja u superizolatorima dovodi do specificnih promena njegovih fizickih osobina, koje mogu da budu prolazne ili trajne. Efekti zracenja razmatrani su sa stanovišta strukturnih promena unutar ispitivanih filmova, kao i promena elektricnih osobina, kao što su specificna elektricna otpornost i strujno-naponska karakteristika. Radijacione promene su uporedene za razne tipove zracenja i debljine filmova superizolatorskih materijala...

Superinsulating state was experimentally observed for the first time only a couple of years ago. The most important property of superinsulators, for their use in electrical engineering, is the infinite electrical resistance. The superinsulating state can be viewed as being dual to the superconducting one, with both states subsisting only below certain critical values of the same three parameters: temperature, applied voltage, and magnetic field strength. Possible applications of superinsulators are for cable insulation (especially of superconducting cables that have to be cooled to low temperatures, at which both the superconducting and the superinsulating state can exist), insulation of galvanic elements (for reducing leakage current losses to a negligible level), and insulation of components in integrated circuit technology (which could make dielectric layers even thinner). After surveying general characteristics of insulating materials and the properties of the superconducting state, the dissertation provides a description of microscopic and macroscopic characteristics of the superinsulating phase. A detailed review of radiation effects in materials is included, depending on the type of radiation and the properties of the medium it traverses. Special attention is given to the interaction of radiation with insulating materials, emphasizing radiation damage in solid state insulators. The principles of using Monte Carlo methods for simulating the passage of radiation through matter are represented. Results of numerical simulations of radiation effects in the analyzed superinsulating films are presented. Simulated radiation transport included incident radiation energy losses through ionization, phonon excitation, and atom displacement. The conducted numerical simulation was linked to the theoretical model of the superinsulating phase, taking account of all the specific traits of this state. It was noted that all three modes of radiation energy deposition in superinsulators bring about either transient or permanent changes of their properties. Radiation effects were considered with respect to structural changes within the investigated films, as well as the changes of electrical properties, such as the specific electrical resistance and the current-voltage characteristic. Radiation-induced changes were compared for various types of radiation and different superinsulating film thicknesses...