The electro-optical Pockels effect is an essential nonlinear effect used in many applications. The ultrafast modulation of the refractive index is, for example, crucial to optical modulators in ...photonic circuits. Silicon has emerged as a platform for integrating such compact circuits, but a strong Pockels effect is not available on silicon platforms. Here, we demonstrate a large electro-optical response in silicon photonic devices using barium titanate. We verify the Pockels effect to be the physical origin of the response, with r
= 923 pm V
, by confirming key signatures of the Pockels effect in ferroelectrics: the electro-optic response exhibits a crystalline anisotropy, remains strong at high frequencies, and shows hysteresis on changing the electric field. We prove that the Pockels effect remains strong even in nanoscale devices, and show as a practical example data modulation up to 50 Gbit s
. We foresee that our work will enable novel device concepts with an application area largely extending beyond communication technologies.
Oxygen vacancies are an important type of defect in transition metal oxides. In SrTiO3 they are believed to be the main donors in an otherwise intrinsic crystal. At the same time, a relatively deep ...gap state associated with the vacancy is widely reported. To explain this inconsistency we investigate the effect of electron correlation in an oxygen vacancy (OV) in SrTiO3. When taking correlation into account, we find that the OV-induced localized level can at most trap one electron, while the second electron occupies the conduction band. Our results offer a natural explanation of how the OV in SrTiO3 can produce a deep in-gap level (about 1 eV below the conduction band bottom) in photoemission, and at the same time be an electron donor. Our analysis implies that an OV in SrTiO3 should be fundamentally regarded as a magnetic impurity, whose deep level is always partially occupied due to the strong Coulomb repulsion. An OV-based Anderson impurity model is derived, and its implications are discussed.
Abstract
NbO
2
has the potential for a variety of electronic applications due to its electrically induced insulator-to-metal transition (IMT) characteristic. In this study, we find that the IMT ...behavior of NbO
2
follows the field-induced nucleation by investigating the delay time dependency at various voltages and temperatures. Based on the investigation, we reveal that the origin of leakage current in NbO
x
is partly due to insufficient Schottky barrier height originating from interface defects between the electrodes and NbO
x
layer. The leakage current problem can be addressed by inserting thin NiO
y
barrier layers. The NiO
y
inserted NbO
x
device is drift-free and exhibits high I
on
/I
off
ratio (>5400), fast switching speed (<2 ns), and high operating temperature (>453 K) characteristics which are highly suitable to selector application for x-point memory arrays. We show that NbO
x
device with NiO
x
interlayers in series with resistive random access memory (ReRAM) device demonstrates improved readout margin (>2
9
word lines) suitable for x-point memory array application.
TiO2 is being widely explored as an active resistive switching (RS) material for resistive random access memory. We report a detailed analysis of the RS characteristics of single-crystal anatase-TiO2 ...thin films epitaxially grown on silicon by atomic layer deposition. We demonstrate that although the valence change mechanism is responsible for the observed RS, single-crystal anatase-TiO2 thin films show electrical characteristics that are very different from the usual switching behaviors observed for polycrystalline or amorphous TiO2 and instead very similar to those found in electrochemical metallization memory. In addition, we demonstrate highly stable and reproducible quantized conductance that is well controlled by application of a compliance current and that suggests the localized formation of conducting Magnéli-like nanophases. The quantized conductance observed results in multiple well-defined resistance states suitable for implementation of multilevel memory cells.
Over the past decade, Si-integrated single crystal thin film BaTiO 3 (BTO) has emerged as a promising material platform for a new generation of electro-optic devices in silicon photonics. Despite ...being relatively young, the BTO technology has demonstrated impressive achievements, such as a very low V π , high bandwidth and linear frequency response, low insertion loss, low power operation and high-speed data transfer. These, combined with novel integration concepts, open a plethora of exciting novel applications in high-speed communication, computing, and sensing. Here we offer a quick snapshot of current developments in this field.
The von Neumann computer architecture is experiencing difficulties with both scaling and power consumption requirements, and as a result, new computing paradigms are being actively explored. Even ...more revolutionary would be a complete or partial switch from electrons to photons. Infrared silicon photonics is one possible avenue for realizing such an alternative computing paradigm. This technology will ultimately require integration of active and passive photonic elements on a single chip. One key photonic element is an optical modulator. Here, we summarize the recent progress in integrating ferroelectric LiNbO
3
and BaTiO
3
with silicon photonics for the purpose of fabricating electro-optic modulators exploiting the linear electro-optic effect.
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