Lithium Niobate Surface Research Articles

Ab initio calculations of nonlinear susceptibility and multiphonon mixing processes in a 2DEG-piezoelectric heterostructure

Solid-state elastic-wave phonons are a promising platform for a wide range of quantum information applications including facilitating quantum transduction from microwave to optical electromagnetic fields, long-lived quantum memories, in addition to potentially acting as qubits themselves. An outstanding challenge and enabling capability in harnessing phonons for quantum information processing is achieving sufficiently strong nonlinear interactions between them. To this end, we propose a general architecture for generating strong quantum phononic nonlinearity using piezoelectric-semiconductor heterostructures consisting of a piezoelectric acoustic material hosting phononic modes that is in direct proximity to a two-dimensional electron gas (2DEG). Each phonon in the piezoelectric material carries an electric field, which extends into the 2DEG. The fields induce polarization of 2DEG electrons, which in turn interact with other piezoelectric phononic electric fields. The net result is coupling between the electric fields associated with the various phonon modes. We derive, from first principles, the nonlinear phononic susceptibility of a piezo-2DEG system and provide a prescription to calculate all orders of the susceptibility in a perturbative expansion. We show that many nonlinear processes are strongly favored at high electron mobility, motivating the use of the 2DEG to mediate the nonlinearities. We derive the first, second, and third-order susceptibilities and calculate them for the case of a lithium niobate surface acoustic wave interacting with a GaAs-AlGaAs heterostructure 2DEG. We show that, for this system, the strong third-order phononic nonlinearities generated could enable single-phonon Kerr shift in an acoustic cavity that exceeds realistic cavity linewidths, potentially leading to a new class of acoustic qubit. We further show that the strong second-order nonlinearity could be used to produce a high-gain, traveling-wave parametric amplifier to amplify—and ultimately detect—the outputs of the acoustic cavity qubits. Assuming favorable losses in such a system, the combination of these capabilities, combined with the ability to efficiently transduce phonons from microwave electromagnetic fields in transmission lines, thus hold promise for creating all-acoustic quantum information processors. Published by the American Physical Society 2024

Laser‐processed lithium niobate wafer for pyroelectric sensor

AbstractDuring the past few decades, pyroelectric sensors have attracted extensive attention due to their prominent features. However, their effectiveness is hindered by low electric output. In this study, the laser processed lithium niobate (LPLN) wafers are fabricated to improve the temperature–voltage response. These processed wafers are utilized to construct pyroelectric sensors as well as human–machine interfaces. The laser induces escape of oxygen and the formation of oxygen vacancies, which enhance the charge transport capability on the surface of lithium niobate (LN). Therefore, the electrodes gather an increased quantity of charges, increasing the pyroelectric voltage on the LPLN wafers to a 1.3 times higher voltage than that of LN wafers. For the human–machine interfaces, tactile information in various modes can be recognized by a sensor array and the temperature warning system operates well. Therefore, the laser modification approach is promising to enhance the performance of pyroelectric devices for applications in human–machine interfaces.image

The impact of various factors on the surface of X-cut lithium niobate and properties of proton-exchanged waveguides

This work describes the effects of various impacts (thermal, plasma, chemical) on X-cut lithium niobate surface and on the structure and optical characteristics of proton-exchanged waveguides. Pre-annealing at 500 °C improved the structural homogeneity of congruent lithium niobate and thus enabled fabricating waveguides of a higher quality. Ar-plasma pretreatment damaged crystal surface and increased lattice deformations. Chemical treatment influenced the surface composition of lithium niobate and the refractive index in annealed proton exchange waveguides. The results provide better understanding of the role of crystal surface in the fabrication of diffusion waveguides and photonic integrated circuits.

Monolithic Strong Coupling of Topological Surface Acoustic Wave Resonators on Lithium Niobate.

Coherent phonon transfer via high-quality factor (Q) mechanical resonator strong coupling has garnered significant interest. Yet, the practical applications of these strongly coupled resonator devices are largely constrained by their vulnerability to fabrication defects. In this study, topological strong coupling of gigahertz frequency surface acoustic wave (SAW) resonators with lithium niobate is achieved. The nanoscale grooves are etched onto the lithium niobate surface to establish robust SAW topological interface states (TISs). By constructing phononic crystal (PnC) heterostructures, a strong coupling of two SAW TISs, achieving a maximum Rabi splitting of 22MHz and frequency quality factor product fQm of ≈1.2 × 1013Hz, is realized. This coupling can be tuned by adjusting geometric parameters and a distinct spectral anticrossing is experimentally observed. Furthermore, a dense wavelength division multiplexing device based on the coupling of multiple TISs is demonstrated. These findings open new avenues for the development of practical topological acoustic devices for on-chip sensing, filtering, phonon entanglement, and beyond.

Trifurcated Splitting of Water Droplets on Engineered Lithium Niobate Surfaces.

Controlled splitting of liquid droplets is a key function in many microfluidic applications. In recent years, various methodologies have been used to accomplish this task. Here, we present an optofluidic technique based on an engineered surface formed by coating a z-cut iron-doped lithium niobate crystal with a lubricant-infused layer, which provides a very slippery surface. Illuminating the crystal with a light spot induces surface charges of opposite signs on the two crystal faces because of the photovoltaic effect. If the light spot is sufficiently intense, millimetric water droplets placed near the illuminated spot split into two charged fragments, one fragment being trapped by the bright spot and the other moving away from it. The latter fragment does not move randomly but rather follows one of three well-defined trajectories separated by 120°, which reflect the anisotropic crystalline structure of Fe:LiNbO3. Numerical simulations explain the behavior of water droplets in the framework of the forces induced by the interplay of pyroelectric, piezoelectric, and photovoltaic effects, which originate simultaneously inside the illuminated crystal. Such a synergetic effect can provide a valuable feature in applications that require splitting and coalescence of droplets, such as chemical microreactors and biological encapsulation and screening.

Resonant scattering of surface acoustic waves by arrays of magnetic stripes

Owing to magnetoelastic coupling, surface acoustic waves (SAWs) may be scattered resonantly by magnetic elements, such as nickel stripes. The scattering may be further enhanced via the Borrmann effect when the elements are organized into an array that matches the acoustic wavelength. We use finite-element modeling to consider single- and double-layer stripes patterned on top of a lithium niobate surface that carries Love surface waves. We do observe enhancement in the coupling for single-layer stripes, but only for Gilbert damping below its realistic value. For double-layered stripes, a weak yet clear and distinct signature of Bragg reflection is identified far away from the acoustic band edge, even for a realistic damping value. Double-layered stripes also offer better magnetic tunability when their magnetic period is different from the periodicity of elastic properties of the structure because of staggered magnetization patterns. The results pave the way for the design of magnetoacoustic metamaterials with an enhanced coupling between propagating SAWs and local magnetic resonances and for the development of reconfigurable SAW-based circuitry.

Antibacterial properties of lithium niobate crystal substrates

The bactericidal properties of chemically patterned lithium niobate substrates under a super-bandgap UV light source is established. UV irradiation of lithium niobate surfaces inoculated with bacteria leads to antimicrobial activity compared to a glass substrate under similar conditions, as determined by surface enhanced Raman spectroscopy and corroborated with a fluorescence-based live/dead assay. This finding may expand the possible biomedical applications of lithium niobate.

High-sensitivity non-cooled near-infrared detector based on lithium niobate surface acoustic wave resonators combined with MXene Ti3C2Tx quantum dot thin films.

In this study, we propose the design of a surface acoustic wave (SAW) near-infrared sensor combined with an MXene quantum dot thin film to improve the infrared absorption efficiency at near-infrared wavelengths. A YZ-cut lithium niobate (LiNbO3) SAW resonator is fabricated as an infrared sensing unit with a resonant frequency shift reflecting the change in infrared radiation. It was observed that the responsivity of the near-infrared sensor (with a base frequency of 460 MHz) increased by approximately 88.89%. Thus, the proposed device exhibits high-performance infrared detection. Owing to the passive wireless capability of the device, it has wide applications.

An Ionic Boundary Layer near the Lithium Niobate Surface in the Proton Exchange Process

An Ionic Boundary Layer near the Lithium Niobate Surface in the Proton Exchange Process

Fabrication and Surface Modification of Niobium Metal–Organic Framework Membrane and its Gas Sensing Application

AbstractThe niobium metal–organic framework (Nb‐MOF = [Nb2(bdc)2(NDI)]n) membrane, constructed from terephthalic acid(bdc) and 1,8,4,5‐naphthalenetetracarboxdiimide (NDI), is in this work grown on the surface of lithium niobate (LiNbO3) film composite optical waveguide (COWG) substrate using UV‐light illumination method. After growing for 20 min, the Nb‐MOF membrane forms as a graphene‐like structure with 50 nm pore size and 96 nm thickness. At room temperature (25 °C), in terms of COWG sensors, Nb‐MOF exhibits the greatest response to H2S and SO2, followed by ethylenediamine (EDA) and NO2, coexistence with 15 kinds of benzenes, amines, and acidic gases. In order to improve its response selectivity, the spirooxazine (SP) is embedded into the Nb‐MOF frame, and a SP@Nb‐MOF membrane COWG with smooth‐snowflake imprinted surface is obtained. In gas sensing performance, the obtained COWG shows the greatest response to H2S, while the response of SO2, NO2, and other gases are obviously diminished. When the SP@Nb‐MOF membrane exposes to H2S gas, proton‐transfer and morphology modulation are induced. The presented sensor also shows a wide detection range (1 × 104–0.1 ppb), fast response (4 s), and long‐term stability of 120 d to H2S at room temperature (25 °C) and 25% relative humidity.

Effective collinear interaction of radiation with a traveling refractive index grating in electro-optical waveguides in lithium niobate

Subject of study. The electrical properties of traveling wave electrodes positioned on a lithium niobate surface are investigated in this study. Method. The investigation methods included the analytical calculation, numerical modeling, and experimental investigation of the amplitude–frequency response and spectra of collinear interaction at the wavelength of 1552 nm. Main results. We demonstrated that traveling wave electrodes with a refractive index close to the refractive index of the optical waveguide should be used when grating periods are shorter than the length of the interaction area. Moreover, in the case of an exact match of the refractive indices, the minimum grating period is mostly limited by frequency-dependent signal attenuation in the electrodes. The effective phase modulation of light at the wavelength of 1552 nm by an electric signal in the band up to 40 GHz was demonstrated. Practical significance. This study determines the parameters of integrated optical circuits, which allow the fabrication of highly effective phase and amplitude light modulators.

Simulation of Heat Transfer in Single-Crystal Lithium Niobate in Interaction with Continuous-Wave Laser Radiation

The paper presents the simulation results of heat transfer in single-crystal lithium niobate (LiNbO3) in the form of cylinder of diameter mm and height mm in interaction with continuous-wave laser radiation with the output power of W and the wavelength of nm. The density of the LiNbO3 crystal is kg/m3; the thermal conductivity along the [001] direction is W/(m×K); the thermal conductivity in the (001) plane is W/(m×K); the specific heat at constant pressure is J/(kg×K); the absorption coefficient is %/cm @ 1064 nm. The laser beam propagates along the optical axis of the crystal. The laser beam intensity profile is represented as a Gaussian function, and the absorption of laser radiation of the single-crystal lithium niobate is described by Beer-Lambert’s law. The numerical solution of the non-stationary heat conduction problem is obtained by meshless scheme using anisotropic radial basis functions. The time interval of the non-stationary boundary-value problem is 2 h 30 min. The results of numerical calculations of the temperature distribution inside and on the surface of the single-crystal lithium niobate at times s are presented. The time required to achieve the steady-state heating mode of the LiNbO3 crystal, as well as its temperature range over the entire time interval, have been determined. The accuracy of the approximate solution of the boundary-value problem at the n-th iteration is estimated by the value of the norm of relative residual . The results of the numerical solution of the non-stationary heat conduction problem obtained by meshless method show its high efficiency even at a small number of interpolation nodes.

Deepening of domains at e-beam writing on the −Z surface of lithium niobate

The focus of this study was to investigate the peculiarities of the domains created by an electron beam (e-beam) in a surface layer of congruent lithium niobate (LiNbO3, LN), which are comparable to the depth of e-beam charge penetration. Direct e-beam writing (DEBW) of different domain structures with a scanning electron microscope was performed on the polar −Z cut. Accelerating voltage 15 kV and e-beam current 100 pA were applied. Different patterns of local irradiated squares were used to create domain structures and single domains. No domain contrast was observed by the piezoelectric force microscopy technique. Based on chemical etching, it was found that the vertices of the domains created do not reach the surface level. The average deepening of the domain vertices was several hundred nanometers and varied depending on the irradiation dose and the locations of the irradiated areas (squares) relative to each other. Computer simulation was applied to analyze the spatial distribution of the electric field in the various irradiated patterns. The deepening was explained by the fact that in the near-surface layer there is a sign inversion of the normal component of the electric field strength vector, which controls the domain formation during DEBW. Thus, with the help of the e-beam, domains were created completely located in the bulk, in contrast to the domains that are nucleated on the surface of the −Z cut during polarization inversion with an atomic force microscope tip. The detected deepening of e-beam domains suggests the possibility of creating ‘head-to-head’ domain walls in near-surface-layer LN by DEBW.

Low Temperature Electrical Properties of CVD Graphene on LiNbO-=SUB=-3-=/SUB=-: Acoustic Studies

Contactless acoustic methods were used to determine electrical parameters --- electrical conductivity, carrier mobility and their concentration --- in single-layer graphene deposited on the surface of lithium niobate. Keywords: graphene, acousto-electronic effects, low temperatures, high-frequency magnetotransport.

Низкотемпературные электрические свойства CVD графена на LiNbO-=SUB=-3-=/SUB=-: акустические исследования

Contactless acoustic methods were used to determine electrical parameters - electrical conductivity, carrier mobility and their concentration - in single-layer graphene deposited on the surface of lithium niobate.

Planarization of Lithium Niobate Surface Using a Thin Film Catalyst in Pure Water

A catalytically assisted etching method, named Catalyst-Referred Etching (CARE) was applied to the planarization of Lithium Niobate (LN) surface, which is widely used for optical waveguides, optical modulators, piezoelectric applications. The study demonstrates that an atomically smooth surface with less than 0.1 nm root-mean-square roughness could be achieved on a LN substrate using a thin metal film and pure water as the catalyst and etching solution, respectively. All residual stress and surface damage could be removed completely thanks to the removal mechanism of CARE.

Sputtering and ripples formation by gas cluster ions on LiNbO-=SUB=-3-=/SUB=- crystal

The work addresses the creation of surface structures on lithium niobate single crystals. Surface topography of lithium niobate surface sputtered with gas cluster ion beams was investigated. Surface ripples induced on the surface were analyzed using power spectral density functions approach, their evolution with ion fluence and their dependence on the cluster ion energy discussed. Sputter yield value was shown to decrease with surface roughness increase, the reasons of the effect are indicated. Local piezoresponse of the rippled surface was studied. Keywords: ferroelectrics, LiNbO3 crystal, gas cluster ions, self-organization, AFM, PSD function.

Surface Acoustic Wave Mitigation of Precipitate Deposition on a Solid Surface─An Active Self-Cleaning Strategy.

We demonstrate the application of a 20 MHz frequency surface acoustic wave (SAW) in a solid substrate to render its surface “self-cleaning”, redirecting the deposition of precipitating mass onto a nearby inert substrate. In our experiment, we confine a solution of poly(methyl methacrylate) polymer and a volatile toluene solvent between two substrates, lithium niobate and glass, at close proximity. We render the glass surface low energy by employing hydrophobic coating. In the absence of SAW excitation, we observe that the evaporation of the solvent yields polymer coating on the higher energy lithium niobate surface, while the glass surface is mostly devoid of polymer deposits. The application of a propagating SAW in the lithium niobate substrate mitigates the deposition of the polymer on its surface. As a response, we observe an increase in the deposition of the polymer precipitates on glass. Above a SAW power threshold, the polymer appears to deposit solely on glass, leaving the surface of the lithium niobate substrate devoid of polymer mass.

Thermostimulated Changes in the Switching Field of Planar CoNi Microparticles Formed on a Surface of Single-Crystal Lithium Niobate

Thermostimulated Changes in the Switching Field of Planar CoNi Microparticles Formed on a Surface of Single-Crystal Lithium Niobate

In-Situ Process and Simulation of High-Performance Piezoelectric-on-Silicon Substrate for SAW Sensor

This paper studied the manufacturing process of Piezoelectric-on-Silicon (POS) substrate which integrates 128° Y–X Lithium niobate thin film and silicon wafer using Smart-Cut technology. The blistering and exfoliation processes of the He as-implanted LN crystal under different annealing temperatures are observed by the in-situ method. Unlike the conventional polishing process, the stripping mechanism of the Lithium niobate thin film is changed by controlling annealing temperature, which can improve the surface morphology of the peeling lithium niobate thin film. We prepared the 128° Y–X POS substrate with high single-crystal Lithium niobate thin film and surface roughness of 3.91 nm through Benzocyclobutene bonding. After simulating the surface acoustic wave (SAW) characteristics of the POS substrate, the results demonstrate that the Benzocyclobutene layer not only performs as a bonding layer but also can couple more vibrations into the LN thin film. The electromechanical coupling coefficient of the POS substrate is up to 7.59% in the Rayleigh mode when hLN/λ is 0.3 and hBCB/λ is 0.1. Therefore, as a high-performance substrate material, the POS substrate has proved to be an efficient method to miniaturize and integrate the SAW sensor.