The resistive switching effect in individual ferromagnetic filaments in memristive stacks based on ZrO2(Y)/Ni functional layers was studied experimentally. A conductive probe of an atomic force microscope played a role of a movable top electrode of a virtual memristive stack. The features of bipolar-type resistive switching found were related to the rapture and restoring of the filaments containing Ni atoms in the ZrO2(Y) dielectric films and are probably caused by different degree of metallization of the filaments. The filaments fromed were manifested in the images obtained by magnetic force microscopy as single-domain ferromagnetic particles. Keywords: memristor, resistive switching, atomic force microscopy, ferromagnetic filaments.

Исследованы электрические характеристики лабораторных макетов мемристоров на основе эпитаксиальных гетероструктур p-Si/p-Ge/n+-Si(001) с Ag- и Ru-электродами. Мемристоры с Ru-электродами демонстрируют меньшее напряжение электроформовки и большее отношение токов в состояниях с низким и высоким значениями сопротивления по сравнению с мемристорами с Ag-электродами. Также в мемристорах с Ru-электродами обнаружена инверсия полярности резистивного переключения. Указанные эффекты обусловлены большей подвижностью ионов Ru3+ в прорастающих дислокациях в слоях p-Si/p-Ge вследствие их меньшего ионного радиуса. Ключевые слова: мемристор, эпитаксиальные слои SiGe, резистивное переключение.

The electrical parameters of the prototype memristors based on p-Si/p-Ge/n + -Si(001) epitaxial heterostructures with Ag and Ru electrodes have been studied. The memristors with Ru electrodes demonstrated smaller electroforming voltage and greater ratio of currents in the low and high resistance values as compared to the memristors with Ag electrodes. Also, an inversion of the resistance switching polarity was observed in the memristors with Ru electrodes. Thses effects originate from a higher mobility of Ru 3+ ions in the threading dislocations in the p-Si/p-Ge layers due to smaller ion radius. Keywords: Memristor, SiGe epitaxial layers, resistance switching.

The effect of optical radiation in the visible and near-infrared bands on resistive switching of a MOS stack based on ZrO2(Y) film on an n-Si(001) substrate with self-assembled Ge nanoislands on its surface has been studied. An increase in the resistive switching logical gap was observed upon the photoexcitation, in particular, when the photon energies were smaller than the Si band gap. The effect was associated with the impact of the photovoltage at the Si/Ge/ZrO2(Y) interface. In the latter case, the effect is associated with spatially indirect interband optical transitions in Ge nanoislands.

The effect of optical radiation in the visible and near-infrared bands on resistive switching of a MOS stack based on ZrO2(Y) film on an n-Si(001) substrate with self-assembled Ge nanoislands on its surface has been studied. An increase in the resistive switching logical gap was observed upon the photoexcitation, in particular, when the photon energies were smaller than the Si band gap. The effect was associated with the impact of the photo-emf at the Si/Ge/ZrO2(Y) interface. In the latter case, the effect is associated with spatially indirect interband optical transitions in Ge nanoislands. Keywords:: memristor, photo-induced resistive switching, yttria-stabilized zirconia, MIS-structure, Ge/Si nanoislands.

Memristors attract the considerable interest of researchers and engineers due to the prospects for creating new information and computing systems on their basis. First of all, this refers to memristive devices based on the resistive switching (RS) effect, which, in most cases, are fabricated in the form of metal–insulator–metal structures. At the same time, the requirement for compatibility with the basic technological process of manufacturing complementary metal-oxide-semiconductor (CMOS) structures makes it very attractive to fabricate memristive devices directly on a silicon substrate or a silicon-on-insulator (SOI) substrate using standard insulator layers such as silicon oxide. The electrical characteristics and RS of memristors based on SiOx thin films formed on SOI substrates are studied. The memristors under study do not require electroforming. For the first time, the possibility of improving the parameters of the resistive switching of SiOx-based memristors on SOI substrates using laser and heat treatments is shown.

Conducting ferromagnetic nanosized filaments consisting of Ni atoms are formed in thin ZrO2(Y)/Ni films using an atomic force microscope probe. The contact of the probe to such films (a virtual composite memristor device) exhibits resistive switching of the bipolar type associated with the destruction and restoration of Ni filaments in the ZrO2(Y) film. The region in which the conductive filament emerges onto the surface of the ZrO2(Y) film manifests itself in the magnetic force image as a single-domain ferromagnetic particle.

In thin ZrO2 (Y) / Ni films, with used of an atomic force microscope (AFM) probe, conductive ferromagnetic filaments of nanometer sizes, consisting of Ni atoms, are formed. Memristor structures based on such films, the upper electrode of which was the AFM probe, demonstrated bipolar-type resistive switching (RP) associated with the destruction and reduction of Ni filaments. The area where the conducting filament emerges on the surface of the ZrO2 (Y) film manifested itself in the magnetic force image as a single-domain ferromagnetic particle.

We report on the application of Contact Scanning Capacitance Microscopy (CSCM) to trace the growth of an individual Ni filament in a ZrO 2 (Y) film on a Ni sublayer (together with a conductive Atomic Force Microscope probe composing a nanometer-sized virtual memristor). An increasing of the filament length in the course of electro-forming results in an increasing of the capacitance between the probe and the sample, which can be detected by CSCM technique. This way, the filament growth can be monitored in real time in situ.

The effect of resistive switching in individual dislocations in memristor Ag/Ge/Si(001) structures is demonstrated experimentally using atomic force microscopy with a conducting probe. A hysteresis is found in the current–voltage characteristics of dislocations, which is typical of bipolar resistive switching related to the formation and destruction of an Ag filament in a Ge layer as a result of drift of Ag + ions along the dislocation core.

Получены лабораторные макеты мемристоров на основе структур Ag / Ge / Si(001) и Ag / Si / Ge / Si(001), принцип действия которых основан на электромиграции ионов Ag+ по дислокациям, прорастающим через слои структур. Исследованы особенности механизма резистивного переключения и процессы деградации мемристоров.

We report on an experimental study of resistive switching (RS) of individual dislocations in Ag/Ge/Si(001) memristors by combined grazing incidence ion sputtering of the Ag electrodes and application of Conductive Atomic Force Microscopy to provide an electrical contact to individual Ag-filled dislocations in the Ge layer. Two types of RS were observed corresponding to two different RS mechanisms: (i) drift of Ag+ ions inside the dislocation cores and (ii) RedOx reactions in residual GeO x in the etch pits on the Ge layer surface.

Экспериментально изучен эффект резистивного переключения отдельных ферромагнитных филаментов мемристорных структур на основе функциональных слоев ZrO2(Y)/Ni. В качестве верхнего прижимного электрода виртуальной мемристорной структуры выступал проводящий зонд атомно-силового микроскопа. Обнаруженные особенности резистивного переключения биполярного типа связаны c разрушением и восстановлением филаментов, содержащих атомы Ni, в диэлектрической пленке ZrO2(Y) и предположительно обусловлены разной степенью металлизации филамента. Сформированные филаменты проявляются на изображениях, полученных с помощью магнитно-силовой микроскопии, как однодоменные ферромагнитные частицы. Ключевые слова: мемристор, резистивное переключение, атомно-силовая микроскопия, ферромагнитные филаменты.

Resistive switching effect of separate dislocations in Ag/Ge/Si(001) memristor structures was demonstrated experimentally by Conductive Atomic Force Microscopy. Hysteresis loops typical for bipolar resistive switching were observed in the current-voltage curves of the dislocations due to formation and rapture of Ag filament in the Ge layer as a result of Ag+ ion drift along the dislocation core.

It is shown that self-forming GeSi nanoislands built into the dielectric–semiconductor interface in the Si(001)-based metal–oxide–semiconductor (MOS) structures with the SiOx and ZrO2(Y) dielectric layers obtained by magnetron sputtering initiate bipolar resistive switching without preliminary electroforming. The I–V characteristics and electrical parameters of the MOS structures in the high- and low-resistance states have been investigated. The change in the charge incorporated in the dielectric at the dielectric–semiconductor interface during resistive switching has been established, which is related to the formation and destruction of conducting filaments. The optically stimulated switching of the MOS structures with the ZrO2(Y) dielectric layer from the high- to low-resistance state has been observed, which is caused by an increase in the conductivity of the space charge region in the Si substrate due to the interband optical absorption in Si leading to the voltage redistribution between Si and ZrO2(Y). A difference between the shapes of the low-signal photovoltage spectra of the MOS structures in the spectral region of the Si intrinsic photosensitivity in the high- and low-resistance states related to the leakage of photoexcited carriers from Si into a metal electrode through filaments has been found.

Aqueous suspension of poorly soluble iron(II) (1-hydroxyethylidene)diphosphonate (FeH2L · H2O) whiskers reacts with hydrogen peroxide to form even less soluble amorphous derivative of iron(III). The whisker shape is maintained during the reaction. Slow oxidation of the aqueous suspension of FeH2L · H2O in air oxygen yields amorphous compound of iron(III) without maintenance of the whisker structure.

It is shown that two modes of resistive switching – bipolar and volatile unipolar – are peculiar for the Ag/Ge/Si structures with germinating dislocations in the germanium layer. In this modes the structures have stable states of electric current with ION/IOFF ~1.5–2.7. The volatile unipolar type of switching can be caused by the capture of charge carriers to deep levels associated with lattice defects in the Ge film of the memristor. At the same time, bipolar switching is associated with the drift of Ag+ ions along germinating dislocations.

The Ag/Ge/Si(001) stacks with threading dislocations growing through the Ge epitaxial layers (ELs) manifested bipolar resistive switching (RS) between two metastable resistance states. Scanning transmission electron microscopy (STEM) provided a direct evidenced the RS mechanism to consist in the electrodiffusion of Ag+ ions along the dislocations in the Ge ELs. Also, STEM revealed multiple RS cycling to result in the metallization of the Ge matrix around the dislocations and in the accumulation of Ag in the misfit dislocation layer near Ge/Si interface. Both above phenomena may lead potentially to degradation of the RS performance.

Ag/Ge/Si heterostructures with threading dislocations in Ge layer can exhibit resistive switching (RS) in two regimes: (i) bipolar and (ii) volatile unipolar. In both regimes, these structures possess stable states with the ratio of currents in the low-resistance state (LRS) and high-resistance state (HRS) within 1.5–2.7. The volatile unipolar switching can be determined by capturing charge carriers on deep levels related to misfit dislocations at the Ge/Si interface, whereas the bipolar switching is related to the drift of Ag + ions via threading dislocations.