The goal of this work is to find ways of enhancing the speed of computer memory cells by using structures that employ operating principles other than those of traditional semiconductors’ schemes. One of the applications of the unique properties of Josephson structures is their usage in novel superfast computer memory cells. Thanks to their high working characteristic frequencies close to 1 THz, the Josephson structures are most promising candidates to be used in petaflop computers. Moreover, both Josephson cryotrons and Josephson SQUIDs can be used in qubits, which are basic units in quantum computers, and also for describing a macroscopic quantum behavior, for example, during read-out processes in quantum computations. In the present work, we have created a mathematical model of transition processes in Josephson cryotrons during direct, “1” → ”0”, as well as inverse, “0” → “1”, logical transitions. We have considered controlling the logical state of Josephson memory cells based on Josephson tunneling junctions of the S-I-S type via external current pulses. By means of mathematical modelling, we have studied transition processes in cryotrons during the change of their logical state and calculated their transition characteristics for working temperatures T1 = 11.6 K and T2 = 81.2 K, which ale close to the boiling temperatures of helium and nitrogen, respectively. It has been shown that such memory cells can effectively operate at the working temperature T2 = 81.2 K. We have determined commutation times for both the direct “0” → “1” and inverse “0” → “1” transitions. We have also identified peculiar behaviors of the Josephson cryotrons based memory cells and studied the stability of their operation.

Effect of annealing on defect structure of thin GaMnAs layers and on Si implanted with Mn + (Si:Mn) has been investigated by X-ray methods, Atomic Force Microscopy and Secondary Ion Mass Spectroscopy. Before and after the treatment the layers were fully strained in respect to the substrate. Decreased value of the GaMnAs lattice parameter is probably related to a decrease in concentration of As antisites and of Mn interstitials and created of MnAs clusters. Lattice parameter of annealed GaMnAs with 2% Mn content was smaller than that of GaAs substrate. Mn concentration remains unchanged after annealing. Defect structure of Si:Mn depends on treatment parameters.

Àíîòàö³ÿ.  ðîáîò³ âäîñêîíàëåíî ìàòåìàòè÷íó ìîäåëü ïåðåõ³äíèõ ïðîöåñ³â â äaeîçåô-ñîí³âñüêèõ åëåìåíòàõ ïàì'ÿò³ (êð³îòðîíàõ), ÿê³ ìîaeíà ñòâîðèòè íà îñíîâ³ íàäïðîâ³äíèõ êâàíòîâèõ ³íòåðôåðîìåòð³â (Ñʲijâ). Êð³îòðîíàìè ñëóaeèëè äâîêîíòàêòí³ ÑʲÄè, êåðó-âàííÿ ëîã³÷íèì ñòàíîì ÿêèõ áóëî äîñë³äaeåíî ìåòîäàìè ìàòåìàòè÷íîãî ìîäåëþâàííÿ. Íàìè çàïðîïîíîâàíî êîìá³íîâàíèé ñïîñ³á êåðóâàííÿ ëîã³÷íèì ñòàíîì òàêèõ êð³îòðîí³â, îñê³ëüêè ïðîñòèé ñïîñ³á êåðóâàííÿ çà äîïîìîãîþ ò³ëüêè ³ìïóëüñ³â ìàãí³òíîãî ïîòîêó íå çàáåçïå÷óº ñòàá³ëüíî¿ ðîáîòè êð³îòðîí³â ï³ä ÷àñ çâîðîòíèõ ëîã³÷íèõ ïåðåõîä³â "1" → "0". Ïîêàçàíî, ùî ïðÿì³ ëîã³÷í³ ïåðåõîäè "0" → "1" ìîaeíà åôåêòèâíî ðåàë³çóâàòè çà äîïîìîãîþ êåðóþ÷èõ ³ì-ïóëüñ³â ìàãí³òíîãî ïîòîêó, à ïåðåõîäè "1" → "0" -êåðóþ÷èõ ³ìïóëüñ³â ñòðóìó. Ðîçðàõîâàíî ïåðåõ³äí³ õàðàêòåðèñòèêè êð³îòðîí³â ï³ä ÷àñ ïðÿìèõ ³ çâîðîòíèõ ëîã³÷íèõ ïåðåõîä³â.Êëþ÷îâ³ ñëîâà: ÑʲÄ, êâàíòîâà êîì³ðêà ïàì'ÿò³, äaeîçåôñîí³âñüêèé êð³îòðîí, ïåðåõ³äíà õàðàêòåðèñòèêà, ëîã³÷íèé ïåðåõ³ä, íàäïðîâ³äíèé ³íòåðôåðîìåòð THE COMBINED METHOD OF LOGICAL STATE CONTROLLING OF CRIOTRONS BASED ON SQUIDS M. V. Tyhanskyi, A.I. PartykaAbstract. In the present work, we have improved the mathematical model of transition processes in Josephson memory cells (cryotrons), which can be created on the base of semiconductor quantum interferometers (SQUIDs). We employed two-contact SQUIDs to construct the cryotrons and investigated the possibilities to control the cryotrons' logical state by means of mathematical modeling. A combined method of logical state controlling of such cryotrons has been proposed since the simpler controlling method, where only impulses of magnetic flux are used, fails to provide stable operation of cryotrons during the inverse logical transitions "1" → "0". We show that the direct logical transitions "0" → "1" are effectively realized via controlling magnetic flux impulses whereas the transitions "1" → "0" are realized via controlling current impulses. Transition characteristics of the cryotrons during direct and inverse logical transitions are calculated.

Using of traditional logic elements in digital electronics has ensured the development of a wide range of electronic devices for many years. In parallel, research and development of logical elements are carried out on the basis of other non-traditional physical phenomena or effects, in particular logic elements based on the phenomenon of superconductivity, the prospect of which is the use of very small energy consumption and ultrahigh performance. For superconducting logic elements, using various Josephson cryoelectronic structures, known as Josephson cryotrons, based on the stationary and non-stationary effects of Josephson. On the basis of the Josephson cryotrons, one can create Josephson elements of computer memory, and Josephson elements of digital logic. The main requirements for the Josephson cryotrons are a stable operating mode and high speed or short switching time. Information about the mode of operation and the speed give us the transition characteristics of the cryotrons - the time dependence of the voltage on the cryotron while changing its logical state, which can be obtained either experimentally, or theoretically. This work aims at a search for new ways of increasing the switching rate of digital logical operators by employing physical structures other than the traditional semiconductor-based schemes. We propose the principles of designing digital logical operators based on Josephson cryotrons, whose operation utilizes the stationary and dynamical Josephson effects, and describe the operational principles of the logical elements “AND” and “OR” bases on tunneling Josephson junctions “superconductor-insulator-superconductor”. Our proposed mathematical models for the commutation processes in such logical elements allowed us to calculate their transition characteristics during the switching and to determine the main parameters in such models. It was shown that the logical elements “AND” and “OR” can be implemented on individual cryotrons and that their logical state can be controlled by input signals in a form of current pulses. Such logical elements meet all the requirements for digital logical elements and have switching time of about 2-3 ps, which indicates their significantly increased switching rate.

In the present work, we show that logical state controlling of Josephson memory cells (cryotrons) is possible not only by applying external current impulses, but also by means of magnetic flux impulses. By using methods of mathematical modeling, we studied transitional processes in cryotrons during the switching of their logical state and calculated transitional characteristics for the operational temperature T = 81,2 Ê. Peculiarities of the Josephson cryotrons' behavior and the effect of the variation of model parameters on direct logical transitions "0" → "1" and inverse logical transitions "1" → "0" are discussed.