The features of the physical mechanisms of controlled ion-plasma formation of the new functional nanomaterials are investigated. The technological regimes of formation of functional nanostructured materials under combined impact of several plasma sources are investigated; the structural and electrical properties of the obtained TiN films are studied. The structures of films are studied with scanning tunnelling microscope JSPM-4500/4610 interlocked with an atomic force microscope. As shown, the optimized helicon-arc reactor demonstrates the unique properties and provides controlled lowtemperature formation of the dense regular TiN nanostructures with the sizes from a few to tens of nanometres.Вивчено особливості фізичних механізмів керованого йонно-плазмового формування нових функціональних наноматеріялів. Відпрацьовано тех-нологічні режими формування функціональних наноструктурованих ма-теріялів за спільної роботи кількох джерел плазми; вивчено структурні та електрофізичні особливості одержаних плівок TiN. Структури плівок до-сліджено на сканівному тунельному мікроскопі JSPM-4500/4610, збло-кованому з атомним силовим мікроскопом. Встановлено, що оптимізова-ний гелікон-дуговий реактор демонструє унікальні властивості і забезпе-чує кероване низькотемпературне формування щільних упорядкованих наноструктур TiN з розмірами від одиниць до десятків нанометрів.Изучены особенности физических механизмов управляемого ионно-плазменного формирования новых функциональных наноматериалов. Отработаны технологические режимы формирования функциональных наноструктурированных материалов при совместной работе нескольких источников плазмы; изучены структурные и электрофизические особен-
Current-voltage characteristics and existence features of a superconducting state under the action of tunneling injection of the spin-polarized current Iinj with a high spin polarization degree (p ≈ 0.97) were studied in double tunneling junctions ferromagnet-insulator-superconductor-insulator-superconductor Co2CrAl–I–Pb/Sn–I–Pb. An empirical formula was proposed for describing a dependence of the energy gap Δ on Iinj. A new spin-polarized inhomogeneous superconducting state consisting of superconducting and resistive regions was found. An existence of the proximity effect through a tunnel barrier between ferromagnetic and superconducting films was established. An effective recombination time of spin-polarized quasiparticles in the nonequilibrium superconductor Pb was estimated.
Методою 3ω досліджено ефективну поперечну теплопровідність λ⊥ тонких плівок AlN. Плівки AlN товщиною 1-3 мкм синтезовано на підкладинках з монокристалічного Si або Al в гібридному геліконно-дуговому йонноплазмовому реакторі. Одержані плівки на межі з підкладинкою мали тонкий шар невпорядкованого AlN товщиною біля 200 нм. Для плівок AlN на підкладинках з монокристалічного Si одержано високе значення коефіцієнта теплопровідности λ⊥Si = 82,9 Вт/(м⋅К). Для плівок AlN на підкладинках з Al одержано значення λ⊥Al = 45,8 Вт/(м⋅К), що є найвищим серед відомих для металічних підкладинок з Al. Проведена оцінка теплового опору Rq межі між плівками AlN і підкладинками Si або Al. Для інтерфейсу AlN/Si одержано значення Rq intSi = 2,3⋅10 −8 (м 2 ⋅К)/Вт, а для інтерфейсу AlN/Al -Rq intAl = 4,3⋅10 −8 (м 2 ⋅К)/Вт.
The giant spin blocking of tunnel currents discovered by us (Low. Temp. Phys. 36, 186 (2010)) is investigated theoretically and experimentally in ferromagnet F (Co2CrAl)- insulator I- superconductor S (Pb) heterostructures with a wide range of specific resistances (10−7–10−4 Ω · cm2). The magnitude of this effect is found to depend on the specific resistance of the junction in the normal state and on recombination spin depolarization. A theoretical model which provides an adequate description of the tunnelling of spin-polarized electrons in F-I-S junctions is proposed. It is found that the normalized conductivity σFS of an F-I-S tunnel junction can be considerably lower than the fundamental normalized conductivity σNS of an N-I-S junction (where N is a normal metal). The proposed model is used to estimate the degree of spin polarization p of films of the ferromagnetic semimetal Co2CrAl (Heusler alloy) with B2- and L21-type crystal structures, which is close to 1 (p ≈ 0.97). The temperature dependence σFS(T) of a Co2CrAl-I-Pb F-I-S tunnel junction is studied experimentally. A theoretical model is proposed which provides an adequate description of the temperature behavior of the normalized conductivity σFS(T) with features of spin-polarized tunnelling taken into account.
Ferromagnetic–insulator–superconductor Co2CrAl–I–Pb tunnel junctions were created and their current-voltage characteristics (CVCs) were studied. It has been established that they differ from the usual CVCs of tunnel junctions of a normal metal–insulator–superconductor. It is proposed to assume that the observed effect of changing the type of CVC is associated with the existence of the destruction of Cooper pairs due to the inverse effect of proximity between the Co2CrAl and Pb electrodes. The CVCs were calculated based on the approach of P. Fulde.
A physical model of tunneling processes leading to a nonequilibrium superconducting state in ferromagnet-superconductor junctions is proposed and confirmed experimentally. The model is based on the analysis of experimental current-voltage characteristics and the determination of junction voltage dependences of the energy gap, the effective chemical potential and the effective temperature of quasiparticles in the modified energy distribution of quasiparticles as well as on taking into account the change in the density of electron states due to destruction of the Cooper pairs, caused by the proximity effect.
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