SBN Thin Films Research Articles

Editorial

Recent developments in both new materials and their multi-functional co-integration raise some fundamental questions that must be addressed theoretically and experimentally. This issue contains 8 articles documenting a selection of contributions to the symposia BB and V of the 2018 European Materials Research Society Spring Meeting, held June 18–22, 2018 in Strasbourg, France. Symposium V brought together researchers who co-integrate complementary functionalities by the heteroepitaxial growth of dissimilar materials. The challenges due to the heterogeneity of materials properties were at the heart of the symposium, with both experimental and theory-modelling perspectives discussed. A wide range of hetero-integration systems were considered (e.g. III-V/Si, oxides/semiconductors, organic/inorganic, 2D materials on 3D templates). Strategies were discussed for understanding and overcoming the problems associated with each hybrid material system, such as interfacial effects, extended defects and chemical mixing/segregation. Symposium BB focused on optical and X-ray techniques for characterizing advanced and hybrid material systems. The whole range of photon wavelengths was considered whereby many complementary characteristics of complex material systems can be explored. The works collected here not only reflect the recent state of the art in materials co-integration and advanced characterization techniques, but also point out future applications such as nanophotonics, quantum computing and energy conversion. Among its prominent contributions, this special section includes three Feature Articles: on 2D materials nanoelectronics from M. Dragoman et al. (DOI 10.1002/pssa.201800724), rare-earth doping of topological insulators from T. Hesjedal et al. (DOI 10.1002/pssa.201800726), and two-photon photoemission spectroscopy for studying semiconductor interfaces from D. Friedrich et al. (DOI 10.1002/pssa.201900251). Hybrid heteroepitaxial growth of MnSb(0001) on GaAs(111) is investigated by G. Bell et al. (DOI 10.1002/pssa.201800600), while shallow junctions in GaAs are studied by J. Duan et al. (DOI 10.1002/pssa.201800618). I. Shlyakhov and coworkers (DOI 10.1002/pssa.201800616) are determining band alignments of MoS2 monolayers with SiO2 and Al2O3 with internal photoemission. In situ and ex situ ellipsometry is proposed as a technique of choice by P. Petrik et al. (DOI 10.1002/pssa.201800676), to study zirconium surfaces for nuclear applications. Finally, the growth of Gd-doped SBN thin films on Pt-coated MgO (100) substrate is studied by C. L. Mak et al. (DOI 10.1002/pssa.201800660). We gratefully acknowledge the efforts of all authors and reviewers, financial assistance of the European Materials Research Society and INSA Rennes, the journal's assistance in realizing this special issue and the continuous support of the editors. Guest Editors Mircea Modreanu, Charles Cornet, Olivier Durand, Hiroyuki Fujiwara, Gerald E. Jellison, Gavin Bell, and Clement Merckling

Preparation and properties of the (Sr,Ba)Nb2O6 thin films by using the sputtering method

Strontium barium niobate (Sr0.3Ba0.7Nb2O6, SBN) thin films were deposited on silicon substrate by using the radio frequency magnetron sputtering and under different deposition power and time at room temperature. Surface morphology and thicknesses of the SBN thin films were characterized by field emission scanning electron microscopy. The crystallization films at different deposition power and time were analyzed by X-ray diffraction (XRD) using CuKα radiation from a Rigaku rotating anode with an incident angle of 2°. The remnant polarization (Pr), saturation polarization (Ps), and minimum coercive field (Ec) properties of the metal-ferroelectric-metal (MFM) structure were measured using ferroelectric material test instrument. The SBN thin films deposited at 90 min and 125 W had the maximum Pr, Ps, and minimum Ec of 1.26 μC/cm 2 , 2.41 μC/cm 2 , and 201.6 kV/cm, respectively. From above results, it knows that the SBN thin films suit for application on ferroelectric random access memory (FeRAM).

열처리 방법에 따른 세라믹 박막의 AFM 및 C-F 특성

The thin films are deposited on Pt electrode() using RF sputtering method at various deposition temperature. The deposition temperature of optimum was . SBN thin films were annealed at using furnace and RTA, respectively. The surface roughness showed about 2.42 nm in annealing temperature() of furnace. The capacitance density of SBN thin films were increased with the increase of annealing temperature. The maximum capacitance density of was obtained by annealing temperature(). The frequency dependence of dielectric loss showed about 0.03 in frequency ranges of 1~1,000 kHz.

Properties of RF Magnetron Sputtered Sr<sub>0.4</sub>Ba<sub>0.6</sub>Nb<sub>1.85</sub>Ta<sub>0.15</sub>O<sub>6</sub> Thin Films

Sr0.4Ba0.6Nb1.85Ta0.15O6 (SBNT) ceramic was used as a target and SBNT thin films were deposited at room temperature. After deposition, the SBN thin films were annealed in conventional furnace (CFA) and in an oxygen atmosphere for 1h by changing the temperature from 700oC to 900oC. The thicknesses of the SBN thin films were calculated by SEM and they were about 450nm independent on the annealing temperature. From the XRD patterns, the as-deposited SBNT thin films displayed amorphous phase, whereas as CFA-treatment was used, the SBNT thin films displayed smooth surfaces. The grain sizes also increased with increasing CFA-treated temperature. In addition, the remanent polarization and saturation polarization increased and coercive field decreased with increasing CFA-treated temperature. Finally, the lnJ-E1/2 curves of the SBNT thin films was developed to find that the linear variations of leakage current densities correspond either to the Schottky emission mechanism or to the Poole-Frenkel emission mechanism.

RF 마그네트론 스퍼터링법에 의한 SBN 박막의 분극특성

The SBN thin films were deposited on Pt/Ti/SiO₂/Si and p-type Si(100) substrate by rf magnetron sputtering method using Sr<SUB>0.7</SUB>Bi<SUB>2.3</SUB>Nb₂O? ceramic target. SBN thin films deposited were annealed at 600~800[℃] by furnace in oxygen atmosphere during 40min. The polarization characteristics have been investigated to confirm the possibility of the SBN thin films for the application t^_@span style=color:#cccccc ^_#o destructive read out ferroelectric random access memory. The maximum remanent polarization and the coercive voltage are 0.6[μC/㎠], 1.2[V] respectively at annealing temperature of 800[℃]. The leakage^_@/span^_#^_@span style=color:#999999 ^_# ... ^_@/span^_#^_@a href=javascript:; onclick=nodeUse('NODE01638901|147003') style=color:#999999;font-size:14px;text-decoration:underline; ^_#전체 초록 보기^_@/a^_#

ChemInform Abstract: Preparation of Strontium Barium Niobate by Sol-Gel Method.

This paper reports on crack-free SBN (Sr{sub x}Ba{sub 1{minus}x}Nb{sub 2}O{sub 6}) thin films that have been prepared by a sol-gel method with metal alkoxides. A homogeneous and stable precursor solution was obtained from Sr and Ba metal and Nb(OEt){sub 5} in ethanol with a key additive of ethoxyethanol. SBN (where x = 0.5) powder crystallized to orthorhombic phase at 700{degrees}C, and then transformed completely to tetragonal phase at 1200{degrees}C. The formation of tetragonal SBN was observed on sapphire (R) substrates at 700{degrees}C, whereas the tetragonal phase began to appear in the powders at 1000{degrees}C. SBN films with highly preferred orientation were successfully synthesized on MgO (100) substrates at 670{degrees}C.

Electrical Properties with Annealing Temperature of SBN Thin Film

The thin films were deposited on Si substrate using RF magnetron sputtering method. And the SBN thin films were annealed at 650~800]. The surface rougness showed about 0.42[nm] in annealed thin film at ]. The dielectric constant(150) of SBN thin film was obtained by annealing temperature above ]. The voltage dependence of dielectric loss showed a value within 0.02 in voltage ranges of -10~＋10[V]. The dielectric constant characteristics showed a stable value with the increase of frequency. Also, the SBN thin films annealed at ] showed a fatigue-free characteristics up to cycles.

RF 스퍼터링법에 의한 SBN 박막의 표면형상 및 유전특성

The <TEX>$Sr_{0.7}Bi_{2.3}Nb_2O_9$</TEX>(SBN) thin films are deposited on Pt-coated electrode(Pt/Ti/<TEX>$SiO_2$</TEX>/Si) using RF sputtering method at various deposition conditions. We investigated the effect of deposition condition on the surface morphology and dielectric properties of SBN thin films. The optimum of the rougness showed about 4.33 nm in 70/30 of Ar/<TEX>$O_2$</TEX> ratio. The crystallinity and rougness of SBN thin films were increased with the increase of rf power. Also, Deposition rate of SBN thin films was about 4.17 nm/min in 70 W of rf power. The capacitance of SBN thin films were increased with the increase of Ar/<TEX>$O_2$</TEX> ratio, rf power and deposition temperature respectively.

SBN thin films growth by RF plasma beam assisted pulsed laser deposition

SBN thin films were grown on MgO and Silicon substrates by PLD and RF-PLD (radiofrequency assisted PLD) starting from single crystal Sr0.6Ba0.4Nb2O6 and ceramic Sr0.5Ba0.5Nb2O6 stoichiometric targets. Morphological and structural analyses were performed on the SBN layers by AFM and XRD and optical properties were measured by spectroellipsometry. The films composition was determined by Rutherford Backscattering Spectrometry. The best set of experimental conditions for obtaining crystalline, c-axis preferential texture and with dominant 31° in-plane orientation relative to the MgO (100) axis is identified.

RF magnetron sputtering deposition growth of highly orientated strontium barium niobate thin films

The ferroelectric potassium ion doped Sr075Ba025Nb2O6(SBN75) buffer layers were fabricated on Si(100) substrate by the sol-gel method, and the highly c-axis preferentially orientated SBN thin films on the KSBN buffer layers were obtained by the RF magnetron sputtering deposition. For the deposition of films, the corresponding preparation parameters have been optimized. It was found that the KSBN buffer layers can reduce the mis-match of crystalline lattices between the SBN film and the substrate effectively. When the ratio of O2/Ar pressure reached 1∶2, the working pressure was 10 Pa, and the sputtering power was 300W, the temperature of substrate was 300℃ and the post-annealing temperature was adjusted to 800℃, the c-axis highly preferentially orientated growth of SBN thin film can be realized. The microstructure of the thin films was investigated by XRD and AFM, and the p-n junction effect was found in our ITO/SBN/KSBN/Si structures, which is characteristic of semiconductor materials. The intensity of the junction effect was closely related to the presence of the buffer layer as well as the crystalline properties of SBN thin films.

Second harmonic generation in the near field and far field: A sensitive tool to probe crystalline homogeneity

In order to probe crystalline orientation of SrxBa1−xNb2O6 (SBN:x) thin film, we have developed a detection scheme based on a scanning near-field optical microscope (SNOM). It is used to image simultaneously the fundamental and the second harmonic generation (SHG) of light by the sample under pulsed laser illumination. We demonstrate on SBN thin films that an apertureless SNOM can dramatically improve the resolution and the sensitivity of SNOM-SHG. Tip direction and focalization are the two crucial parameters in the SNOM-SHG experiments. Moreover, we show the ability of our setup to separate near field from far field contribution to the SHG. This is indeed very helpful in order to measure surface-SHG coefficients.

Epitaxial growth of Sr x Ba1−x Nb2 O6 (SBN) thin films on Pt coated MgO substrates: the determining control of platinum crystallographic orientation

The growth of (001) oriented Sr x Ba1−x Nb2 O6 (SBN:x) thin films on MgO single crystals substrates has focused attention due to its potential application to integrated signal waveguiding and electro-optic processing. This paper addresses the possible insertion of a platinum bottom electrode to implement the electro-optic effect, and examines the influence of Pt orientation on the subsequent growth of SBN thin films deposited by R.F. magnetron sputtering. We have first investigated the optimal sputtering conditions of a (001) Pt oriented growth. Experimental evidence is provided for an orientation switching temperature sensitive to R.F. power but insensitive to deposition rate which suggests that kinetic phenomena are not involved in the orientation development of Pt films. Seeding the MgO substrate with Fe, Cu or Cr inhibits the competitive (111) Pt growth without modifying the optimal temperature for (001) growth. Annealing at a temperature sufficient to crystallise the top SBN film causes a drastic evolution of the initial (111) and (001) Pt volume fractions, making particularly critical the deposition conditions for a final dominant (001) Pt texture on unseeded substrates. The (001) oriented growth of SBN is shown to occur exclusively on (001) Pt crystallites stable against subsequent annealing steps. As a final result, (001) SBN films have been obtained epitaxial on both Pt coated and not coated (001) MgO substrates. They display two in-plane orientations mirror symmetric (±α) to the axis of (001) MgO, with α shifted from 31° to 18° by (001) Pt coating.

Enhanced ferroelectric properties of multilayer SrBi 2Ta 2O 9/SrBi 2Nb 2O 9 thin films for NVRAM applications

Ferroelectric SrBi 2Ta 2O 9/SrBi 2Nb 2O 9 (SBT/SBN) multilayer thin films with various stacking periodicity were deposited on Pt/TiO 2/SiO 2/Si substrate by pulsed laser deposition technique. The X-ray diffraction patterns indicated that the perovskite phase was fully formed with polycrystalline structure in all the films. The Raman spectra showed the frequency of the O–Ta–O stretching mode for multilayer and single layer SrBi 2(Ta 0.5Nb 0.5) 2O 9 (SBNT) samples was ∼827–829 cm −1, which was in between the stretching mode frequency in SBT (∼813 cm −1) and SBN (∼834 cm −1) thin films. The dielectric constant was increased from 300 (SBT) to ∼373 at 100 kHz in the double layer SBT/SBN sample with thickness of each layer being ∼200 nm. The remanent polarization (2 P r) for this film was obtained ∼41.7 μC/cm 2, which is much higher, compared to pure SBT film (∼19.2 μC/cm 2). The coercive field of this double layer film (67 kV/cm) was found to be lower than SBN film (98 kV/cm).

Environmentally safe synthesis of SrBi2Ta2O9and SrBi2Nb2O9thin films

The modern industry of electronic devices has driven the development of new synthesis methods for producing materials with the desired properties. Most of these methods rely on reagents and solvents that are toxic for human health and environment. For example, it has been reported that the preparation of thin films by metallorganic deposition methods (MOD) often requires noxious chemicals. SrBi 2 Ta 2 O 9 (SBT) and SrBi 2 Nb 2 O 9 (SBN) are ferroelectric compounds with important applications as non volatile ferroelectric random access memories (NVFRAM). The advantage of being lead-free compounds is partially loss if the necessary efforts for making their precursors synthesis as safe as possible are not made. In this work a new method using an ethanol-based solution and starting from the acetates of the desired cations for obtaining SBT and SBN thin films is described. The properties of the obtained films demonstrate the good quality of the so prepared materials: the remnant polarization (Pr) values are around 6 μC/cm 2 and 10 μC/cm 2 for stoichiometric SBT and SBN respectively, and the observed leakage currents stay below 3μA for applied fields of 240 kV/cm 2 . These characteristics indicate the present method to be adequate for producing ferroelectric materials with suitable properties for memories applications.

Growth of highly c-axis oriented SBN thin films on Si(100) with/without MgO buffer layer by the sol-gel method

Growth of highly c-axis oriented SBN thin films on Si(100) with/without MgO buffer layer by the sol-gel method

Host excitation-induced red emission from Pr 3+ in strontium barium niobate thin film

Optical quality Sr x Ba 1− x Nb 2O 6 (SBN) thin films doped with Pr 3+ ions were successfully grown on fused quartz substrates using a pulsed laser deposition technique. Both as-grown and annealed samples were studied at either room temperature or at 10 K. Luminescence measurements show that most 4f 2→4f 2 emissions from Pr 3+ centers were efficiently quenched in the films. Strong red emission from 1D 2 to 3H 4 at ∼610 nm accompanied by weak emission to other 3H j multiplets could be observed only by UV excitation into the SBN conduction band. At 10 K, the main emission peak splits into four components. In addition, a broadband SBN-host luminescence was identified at ∼560 nm in the annealed sample, associated with the charge-transfer vibronic exciton. As an interstitial ion, Pr 3+ may occupy a 15-, 12-, 9- or 6-fold cage surrounded by oxygen and was found to occupy all four possible sites in SBN thin films. This behavior is different from Eu 3+- SBN where Eu 3+ only occupies a 6-fold site.

Effect of Ca on structural and ferroelectric properties of SrBi 2Ta 2O 9 and SrBi 2Nb 2O 9 thin films

In this study, we have improved the remanent polarization of SrBi 2Ta 2O 9 (SBT) and SrBi 2Nb 2O 9 (SBN) thin films using Ca substitution at Sr-site. SBT and SBN thin films with different concentrations of Ca were deposited on Pt/TiO 2/SiO 2/Si substrates using pulsed-laser-deposition technique. The lattice parameters was found to be decreased with Ca incorporation and was attributed to the smaller ionic radii of Ca than for Sr. The modification in lattice vibrational frequencies with the incorporation of Ca in SBT and SBN films was investigated using micro-Raman spectroscopy. The grain size was increased with the increase in the Ca concentrations in SBT and SBN thin films. The SBT thin films with 20% Ca contents exhibited remnant polarization of ∼23.8 μC/cm 2 with a coercive field of ∼175 kV/cm. The remanent polarization was found to be ∼35.5 μC/cm 2 for SBN thin films with 10% Ca incorporation. The dielectric constant of SBT and SBN films was found to be decrease with Ca concentrations and observed to be independent of grain size.

Growth of highly c-axis oriented K:SBN thin films on Si(100) by the sol-gel method

Ferroelectric SrxBa1-xNb2O6 (0.2＜x＜0.8, SBN100 x＝ thin films of highly preferred c axis orientation have been grown on Si (100) substrate by the sol-gel method with post annealing at 1000°C. Investigated by x-ray diffraction and second ion mass spectrum,we observed that the SBN thin films prepared using NbCl5 precursor solution contained K+ ions, compared with Nb(OC2H5)5 precursored SBN films. By choosing appropriate contents of K+ there exists the optimum preferred orientation in SBN thin film.K ions dissolving in SBN cell and entering Si substrate can make SBN cell and Si cell a small twist simultaneously,which improves the matching of the film and the substrate to promote the high c axis superior growth.Finally,the optic characteristics of thin films have been tested.

Ferroelectric Properties of SBN Thin Films Deposited by Ion Beam Sputtering

Strontium barium niobate thin films with nominal composition corresponding to Sr0.30Ba0.70Nb2O6 (SBN30) were deposited onto Pt/Ti/SiO2/Si(100) substrate by ion beam sputter deposition (IBSD) technique. D–E hysteresis loops for Pt/SBN30/Pt capacitor samples were saturated after annealing treatment in air above 750°C, with remanent polarization (2Pr) value of about 22 μC/cm2 and coercive field (Ec) of about 128 kV/cm. Relative permittivity and leakage current characteristics were also determined from C–V and I–V measurements.

Preparation and electrical properties of SBN thin films derived from aqueous organic gels

Sr 0.5Ba 0.5Nb 2O 6 (SBN50) thin films have been prepared using aqueous organic gel method. The differences in the decomposition between Sr–Ba–Nb nitrate precursor solutions with different pH values were investigate. By heat treatment at 700 °C for 2 h, SBN thin films with smooth and crack-free surface were derived from the precursor solution of a lower pH=8. XRD patterns revealed the polycrystalline nature of the SBN thin films on Pt/Ti/SiO 2/Si(100) substrates. Electric properties measurement indicated that the SBN films demonstrated a ferroelectric hysteresis loop. The remanent polarization ( P r) and coercive field ( E c) were 8.17 μC/cm 2 and 16.9 kV/cm, respectively.