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Thin-film ferroelectric doped hafnia has emerged as a promising candidate for non-volatile computer memory devices due to its CMOS compatibility. The ferroelectricity in thin-film HfO2 is defined by the polar orthorhombic phase, whose stabilization depends on various parameters, such as doping species, stress, thickness, crystallization annealing temperature, etc. The concentration of oxygen vacancies is yet another parameter affecting the stabilization of the ferroelectric phase in HfO2 thin films. Here, we report on the effect of oxygen vacancies introduced in Y-doped HfO2 (HYO) films during reactive pulsed laser deposition on their ferroelectric properties, which we systematically study by correlating structural and electrical properties. Among different techniques, near-edge x-ray absorption fine structure analysis is successfully employed to distinguish between structurally similar ferroelectric orthorhombic and paraelectric tetragonal phases. It is shown that oxygen vacancies introduced at a certain concentration in HYO films can be used as a tool to control the phase composition as well as to decrease the formation energy (crystallization temperature) of the ferroelectric phase. Based on these results, we demonstrate a back-end-of-line compatible ferroelectric HYO capacitor device with competitive functional properties. [ABSTRACT FROM AUTHOR]

The nanosecond speed of information writing and reading is recognized as one of the main advantages of next-generation non-volatile ferroelectric memory based on hafnium oxide thin films. However, the kinetics of polarization switching in this material have a complex nature, and despite the high speed of internal switching, the real speed can deteriorate significantly due to various external reasons. In this work, we reveal that the domain structure and the dielectric layer formed at the electrode interface contribute significantly to the polarization switching speed of 10 nm thick Hf0.5Zr0.5O2 (HZO) film. The mechanism of speed degradation is related to the generation of charged defects in the film which accompany the formation of the interfacial dielectric layer during oxidization of the electrode. Such defects are pinning centers that prevent domain propagation upon polarization switching. To clarify this issue, we fabricate two types of similar W/HZO/TiN capacitor structures, differing only in the thickness of the electrode interlayer, and compare their ferroelectric (including local ferroelectric), dielectric, structural (including microstructural), chemical, and morphological properties, which are comprehensively investigated using several advanced techniques, in particular, hard X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and electron beam induced current technique. [ABSTRACT FROM AUTHOR]

Multiferroic materials with coexisting ferroelectric and ferromagnetic orders have attracted much attention due to the magnetoelectric coupling opening alternative prospects for electronic devices. Composite multiferroics containing separate ferroelectric and ferromagnetic components are a promising alternative to the single-phase counterparts. Composite multiferroic structures comprising HfO2-based ferroelectrics are potentially feasible for technological applications. Here, this study reports on the experiments aiming at the manifestation of magnetoelectric coupling at Fe/Hf0.5Zr0.5O2 (HZO) interface. Using synchrotron based 57Fe Mössbauer spectroscopy technique in operando, this study probes element-selectively the local magnetic properties of a nanometer-thick enriched 57Fe marker layer in functional Pt/57Fe/HZO/TiN capacitors and demonstrates the evidence of the ferroelectric polarization effect on the a-Fe magnetic response. Besides a-Fe exhibiting a magnetoelectric coupling, both ferromagnetic and superparamagnetic Fe3O4 components are found in the Mössbauer spectra, apparently originating from the oxygen or OH- ions penetrating ultrathin Pt overlayer during crystallization annealing of HZO. The observed effect as well as the electronic band lineup of the Fe/HZO interface elucidated from synchrotron based hard X-ray photoemission spectroscopy measurements are interpreted in terms of charge-mediated magnetoelectric coupling at the Fe/HfO2 interface driven by ferroelectric HZO polarization reversal. [ABSTRACT FROM AUTHOR]

A method is developed to measure effective work function of metal gate in contact with high-[kappa] dielectric. The effective work function of NiSi, N[i.sub.2]Si, and Sb-doped Si gate electrodes on high-[kappa] gate stack dielectric was found to be 4.4, 4.5-4.7, and 4.2 eV respectively.

Embedded, low-power, fast nonvolatile memory is considered to be a viable approach to improving the performance of computing systems designed for real-time processing of the incoming information stream. Among different nonvolatile memory concepts, resistive random access memory is one of the competitive candidates because of the combination of functional properties, such as the energy per writing cycle, speed, number of switching cycles (endurance), and retention time. In this work, we explore the effect of nanopatterning of the Pt bottom electrode (BE) to control the formation, number, and size of conductive filaments in the TaOx layer in Ta/TaOx/Pt resistance switching (RS) devices integrated with field-effect transistors (the one transistor and one resistor concept). Patterning is achieved by either etching "holes" in the Pt BE or growth of Pt "pillars" on top of a flat continuous underlayer. Such nanopatterned RS devices reveal lower (∼1.2 vs ∼2.5 V) electroforming voltages and ∼102 times lower currents in the ON state compared to those with a nonpatterned Pt electrode, while exhibiting more than 105 switching cycles without any degradation as well as better device-to-device and cycle-to-cycle repeatability of electrical characteristics. The modeling of the electric-field distribution across the functional TaOx layer reveals the edge of Pt nanopillars as the most probable area for filament formation. The elemental mapping during transmission electron microscopy analysis of the patterned Ta/TaOx/Pt RS device cross section confirms that the thickness of the TaOx layer on top of the Pt "pillar" is minimal at the inclined edge. The conducting atomic force microscopy current mapping of two patterned RS devices upon electroforming and removal of the top electrode in high- and low-resistance states confirms a single conducting channel formed at the edge of the Pt electrode. [ABSTRACT FROM AUTHOR]

Abstract A two-dimensional layers of metal (Me) nanocrystals embedded in SiO2 were produced by pulsed laser deposition of uniformly mixed Si:Me film followed by its furnace oxidation and rapid thermal annealing. The kinetics of the film oxidation and the structural properties of the prepared samples were investigated by Rutherford backscattering spectrometry, and transmission electron microscopy, respectively. The electrical properties of the selected SiO2:Me nanocomposite films were evaluated by measuring C-V and I-V characteristics on a metal-oxide-semiconductor stack. It is found that Me segregation induced by Si:Me mixture oxidation results in the formation of a high density of Me and silicide nanocrystals in thin film SiO2 matrix. Strong evidence of oxidation temperature as well as impurity type effect on the charge storage in crystalline Me-nanodot layer is demonstrated by the hysteresis behavior of the high-frequency C-V curves.

The crystallization of as‐grown amorphous Hf0.5Zr0.5O2 (HZO) thin films to the metastable ferroelectric phase by pulsed laser annealing (PLA) is investigated. PLA experiments are conducted using a Nd:YAG laser operating in two regimes: Q‐switched mode with a pulse duration of τ ≈ 16 ns and free‐running mode (τ ≈ 1 ms). The crystallization of a ferroelectric orthorhombic phase in the annealed films is confirmed by X‐ray diffraction, polarization versus electric field (P–E) measurements, and piezoresponse force microscopy (PFM) analyses. Remnant polarization up to 2Pr ≈ 50 μC cm−2 is achieved in the TiN/HZO/W capacitor structures grown on the Si substrate and subjected to millisecond PLA. In contrast, the use of laser annealing in a 10 ns pulse duration range is found ineffective for the crystallization of any HZO phase in capacitor structures. Detailed PFM analysis across a capacitor device area reveals the effect of the local temperature on the sample surface during PLA on the resulting ferroelectric domain structure. The lower thermal impact on the substrate during PLA opens the possibility of creating local areas of the ferroelectric phase in HZO films using reflecting copper masks. [ABSTRACT FROM AUTHOR]

When coupled with ferromagnetic layers (FM), topological insulators (TI) are expected to boost the charge‐to‐spin conversion efficiency across the FM/TI interface. In this context, a thorough control and optimization of the FM/TI interface quality are requested. Here, the evolution of the chemical, structural, and magnetic properties of the Fe/Sb2Te3 heterostructure is presented as a function of a rapid mild thermal annealing conducted on the Sb2Te3‐TI (up to 200 °C). While the bilayer is not subjected to any thermal treatment upon Fe deposition, the annealing of Sb2Te3 markedly improves its crystalline quality, leading to an increase in the fraction of ferromagnetic Fe atoms at the buried Fe/Sb2Te3 interface and a slight lowering of the magnetic coercivity of the Fe layer. The method is an efficient tool to clean up the Fe/Sb2Te3 interface, which may be extended to different FM/TI heterostructures. Simultaneously to the interface reconstruction, a constant ≈20% fraction of FeTe develops at the interface. Since FeTe can display superconductivity, the Fe/Sb2Te3 system could have potentialities for exploiting phenomena at the edge of magnetism, superconductivity and topology. [ABSTRACT FROM AUTHOR]

Composite bilayer multiferroics combining ferroelectric (FE) and ferromagnetic (FM) thin‐film materials in a heterostructure and exhibiting magnetoelectric (ME) coupling effect are of great scientific and technological interest. In particular, electronically driven ME coupling implies that the FE polarization orientation affects the magnetic properties of FM at the interface with FE. Unlike metals, where the electric field penetrates over distances of 1–2 unit cells only, magnetic semiconductors, particularly doped EuS, with a ≈10 nm screening length appear a viable alternative. In addition, EuS exhibits a metal–insulator transition, thus offering new functionalities in nanoelectronics. Meanwhile, ultrathin polycrystalline films of doped HfO2, such as Hf0.5Zr0.5O2 (HZO), stabilized in the noncentrosymmetric orthorhombic phase, are identified as a novel class of robust FE materials. In this work, FM EuS integrated with FE HZO in a bilayered structure is promoted as a prospective composite multiferroic. The functionality of both ultrathin FM‐EuS and FE‐HZO layers as well as their compatibility in a capacitor configuration is demonstrated. The comprehensive information on the structural, chemical, and electronic properties of EuS/HZO interface endorses it as a promising medium for magnetoelectric coupling phenomena, particularly, the effect of polarization reversal in FE‐HZO on the magnetic and transport properties in EuS. [ABSTRACT FROM AUTHOR]

The development of highly integrated electrophysiological devices working in direct contact with living neuron tissue opens new exciting prospects in the fields of neurophysiology and medicine, but imposes tight requirements on the power dissipated by electronics. On-chip preprocessing of neuronal signals can substantially decrease the power dissipated by external data interfaces, and the addition of embedded non-volatile memory would significantly improve the performance of a co-processor in real-time processing of the incoming information stream from the neuron tissue. Here, we evaluate the parameters of TaO x -based resistive switching (RS) memory devices produced by magnetron sputtering technique and integrated with the 180-nm CMOS field-effect transistors as possible candidates for on-chip memory in the hybrid neurointerface under development. The electrical parameters of the optimized one-transistor–one-resistor (1T-1R) devices, such as the switching voltage (approx. ±1 V), uniformity of the R off/ R on ratio (∼10), read/write speed (<40 ns), and the number of the writing cycles (up to 1010), are satisfactory. The energy values for writing and reading out a bit ∼30 and ∼0.1 pJ, respectively, are also suitable for the desired in vitro neurointerfaces, but are still far too high once the prospective in vivo applications are considered. Challenges arising in the course of the prospective fabrication of the proposed TaO x -based RS devices in the back-end-of-line process are identified. [ABSTRACT FROM AUTHOR]

In order to enable the use of the prototypical 2D‐layered MoS2 for spintronics, its integration with ferromagnetic layers is mandatory. By employing interface‐sensitive 57Fe conversion electron Mössbauer spectroscopy (CEMS), hard X‐ray photoelectron spectroscopy (HAXPES), and transmission electron microscopy (TEM), the chemical, structural, and magnetic properties of the Fe/2D‐MoS2 interface are investigated. CEMS shows that out of the first 1 nm of Fe in direct contact with 2D‐MoS2, about half of the Fe atoms keeps the un‐perturbed Fe local environment, partly in regions where the original 2D‐layered structure of MoS2 is preserved as shown by TEM. The remaining reacting Fe atoms exclusively bond with Mo, with the majority of them being characterized by a ferromagnetic environment and the rest coordinating in a paramagnetic Fe‐Mo configuration. The preferential Fe bonding with Mo is corroborated by HAXPES analysis. The results provide detailed insight into the link between the bonding configuration and the interfacial magnetism at the Fe/2D‐MoS2 heterojunction. [ABSTRACT FROM AUTHOR]

Since the discovery of ferroelectricity (FE) in HfO2-based thin films, they are gaining increasing attention as a viable alternative to conventional FE in the next generation of non-volatile memory devices. In order to further increase the density of elements in the integrated circuits, it is essential to adopt a three-dimensional design. Since atomic layer deposition (ALD) processes are extremely conformal, ALD is the favored approach in the production of 3D ferroelectric random access memory. Here, we report the fabrication of fully ALD-grown capacitors comprising a 10-nm-thick FE Hf0.5Zr0.5O2 layer sandwiched between TiN electrodes, which are subjected to a detailed investigation of the structural and functional properties. The robust FE properties of Hf0.5Zr0.5O2 films in capacitors are established by several alternative techniques. We demonstrate a good scalability of TiN/Hf0.5Zr0.5O2/TiN FE capacitors down to 100-nm size and the polarization retention in the test "one transistor-one capacitor" (1T-1C) cells after 1010 writing cycles. The presence of a noncentrosymmetric orthorhombic phase responsible for FE properties in the alloyed polycrystalline Hf0.5Zr0.5O2 films is established by transmission electron microscopy. Given the ability of the ALD technique to grow highly conformal films and multilayered structures, the obtained results indicate the route for the design of FE non-volatile memory devices in 3D integrated circuits. [ABSTRACT FROM AUTHOR]