Pub Date : 2024-10-16DOI: 10.1016/j.jcrysgro.2024.127919
V. Vaněček , T. Horiai , M. Yoshino , A. Yamaji , A. Yoshikawa , M. Nikl
The possibility of growing Cs1-xRbxBF3 (B = Ca, Sr) crystals by micro-pulling-down was investigated due to their potential for application in ultrafast scintillation detectors. A LiF flux was applied to lower the melting point and therefore suppress evaporation of CsF from the melt. Suitable growth conditions were obtained through careful choice of the hot zone elements. A crucible with minimal nozzle length improved mass transport and an afterheater with four windows provided a steep temperature gradient. Inclusion and crack-free crystals of Cs1-xRbxCaF3 (x = 0, 0.1, 0.25, 0.5, 0.75, 0.9, and 1) and CsCa1-xSrxF3 (x = 0, 0.1, and 0.25) were grown under optimized conditions. Despite the hygroscopic nature of the heavy alkali metal fluorides, all the grown crystals are non-hygroscopic which significantly improves their application potential. Growth of CsCa1-xSrxF3 crystals with higher Sr concentration was complicated by the low solubility of SrF2 in the LiF-CsF melt and the hygroscopic nature of the CsSrF3. The formation of solid solution in the Cs1-xRbxCaF3 and CsCa1-xSrxF3 systems was investigated through the dependence of lattice parameters on nominal composition.
{"title":"Flux growth of Cs1-xRbxBF3 (B = Ca, Sr) crystals by the micro-pulling-down method","authors":"V. Vaněček , T. Horiai , M. Yoshino , A. Yamaji , A. Yoshikawa , M. Nikl","doi":"10.1016/j.jcrysgro.2024.127919","DOIUrl":"10.1016/j.jcrysgro.2024.127919","url":null,"abstract":"<div><div>The possibility of growing Cs<sub>1-x</sub>Rb<sub>x</sub>BF<sub>3</sub> (B = Ca, Sr) crystals by micro-pulling-down was investigated due to their potential for application in ultrafast scintillation detectors. A LiF flux was applied to lower the melting point and therefore suppress evaporation of CsF from the melt. Suitable growth conditions were obtained through careful choice of the hot zone elements. A crucible with minimal nozzle length improved mass transport and an afterheater with four windows provided a steep temperature gradient. Inclusion and crack-free crystals of Cs<sub>1-x</sub>Rb<sub>x</sub>CaF<sub>3</sub> (x = 0, 0.1, 0.25, 0.5, 0.75, 0.9, and 1) and CsCa<sub>1-x</sub>Sr<sub>x</sub>F<sub>3</sub> (x = 0, 0.1, and 0.25) were grown under optimized conditions. Despite the hygroscopic nature of the heavy alkali metal fluorides, all the grown crystals are non-hygroscopic which significantly improves their application potential. Growth of CsCa<sub>1-x</sub>Sr<sub>x</sub>F<sub>3</sub> crystals with higher Sr concentration was complicated by the low solubility of SrF<sub>2</sub> in the LiF-CsF melt and the hygroscopic nature of the CsSrF<sub>3</sub>. The formation of solid solution in the Cs<sub>1-x</sub>Rb<sub>x</sub>CaF<sub>3</sub> and CsCa<sub>1-x</sub>Sr<sub>x</sub>F<sub>3</sub> systems was investigated through the dependence of lattice parameters on nominal composition.</div></div>","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"649 ","pages":"Article 127919"},"PeriodicalIF":1.7,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142535700","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-16DOI: 10.1016/j.jcrysgro.2024.127917
Sajeena Beevi Sharafudheen , C. Vijayakumar , R. Rajakrishnan , Ahmed Alfarhan , Selvaraj Arokiyaraj , M.R. Bindhu
This study explores the biogenic synthesis of CuO nanoparticles functionalized with Solanum nigrum, using Acalypha indica leaf extract as a reducing agent. The biogenically synthesized CuO nanoparticles were comprehensively characterized by various analytical techniques, involves X-ray diffraction analysis (XRD), BET surface area analysis (BET), energy-dispersive X-ray spectroscopy (EDAX), X-ray photoelectron spectroscopy (XPS), UV–Visible spectral analysis (UV), Fourier transform infrared spectroscopy (FTIR), fluorescence spectroscopy, electrochemical analysis, and linear sweep voltammetry studies. The XRD analysis revealed end centered monoclinic phase with a 10 nm average crystalline size. BET analysis showed a mesoporous structure with a surface area of 11.54 m2/g. XPS and EDAX confirmed the presence of Cu2+ and O2− ions. SEM and TEM images indicated spherical, and porous nanostructures. UV–Visible spectroscopy identified an active optical range of 508–518 nm (2.40–2.45 eV), suggesting potential photocatalytic activity. The photocatalytic degradation efficiencies of Methylene blue (98.8 %) and Rhodamine B (95 %) were achieved after 100 min of irradiation. Antimicrobial tests demonstrated effectiveness against Staphylococcus aureus, E. coli, Shigella flexneri, and Candida tropicalis. The nanoparticles exhibited notable cytotoxicity against colorectal cancer cells with IC50 values of 58.66 μg/ml. Additionally, a symmetric supercapacitor electrode using these nanoparticles achieved a specific capacitance of 375 Fg−1 at the current density of 1 Ag−1. This research underscores the versatile applications of biogenic CuO nanoparticles in photocatalysis, antimicrobial treatments, cancer therapy, and energy storage.
{"title":"Biogenic synthesis of porous CuO nanoparticles: Synergistic effects in photocatalytic dye degradation and electrochemical energy storage applications","authors":"Sajeena Beevi Sharafudheen , C. Vijayakumar , R. Rajakrishnan , Ahmed Alfarhan , Selvaraj Arokiyaraj , M.R. Bindhu","doi":"10.1016/j.jcrysgro.2024.127917","DOIUrl":"10.1016/j.jcrysgro.2024.127917","url":null,"abstract":"<div><div>This study explores the biogenic synthesis of CuO nanoparticles functionalized with <em>Solanum nigrum</em>, using <em>Acalypha indica</em> leaf extract as a reducing agent. The biogenically synthesized CuO nanoparticles were comprehensively characterized by various analytical techniques, involves X-ray diffraction analysis (XRD), BET surface area analysis (BET), energy-dispersive X-ray spectroscopy (EDAX), X-ray photoelectron spectroscopy (XPS), UV–Visible spectral analysis (UV), Fourier transform infrared spectroscopy (FTIR), fluorescence spectroscopy, electrochemical analysis, and linear sweep voltammetry studies. The XRD analysis revealed end centered monoclinic phase with a 10 nm average crystalline size. BET analysis showed a mesoporous structure with a surface area of 11.54 m<sup>2</sup>/g. XPS and EDAX confirmed the presence of Cu<sup>2+</sup> and O<sup>2−</sup> ions. SEM and TEM images indicated spherical, and porous nanostructures. UV–Visible spectroscopy identified an active optical range of 508–518 nm (2.40–2.45 eV), suggesting potential photocatalytic activity. The photocatalytic degradation efficiencies of Methylene blue (98.8 %) and Rhodamine B (95 %) were achieved after 100 min of irradiation. Antimicrobial tests demonstrated effectiveness against <em>Staphylococcus aureus</em>, <em>E. coli</em>, <em>Shigella flexneri</em>, and <em>Candida tropicalis</em>. The nanoparticles exhibited notable cytotoxicity against colorectal cancer cells with IC<sub>50</sub> values of 58.66 μg/ml. Additionally, a symmetric supercapacitor electrode using these nanoparticles achieved a specific capacitance of 375 Fg<sup>−1</sup> at the current density of 1 Ag<sup>−1</sup>. This research underscores the versatile applications of biogenic CuO nanoparticles in photocatalysis, antimicrobial treatments, cancer therapy, and energy storage.</div></div>","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"649 ","pages":"Article 127917"},"PeriodicalIF":1.7,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142535566","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-16DOI: 10.1016/j.jcrysgro.2024.127951
G. Maity , Geetika Patel , S. Ojha , S. Dubey , Shiv P. Patel , D. Kanjilal
The development of nano-porous gold (NPG) via room temperature ion irradiation has been presented in detail. The bilayer thin films of a-Ge/c-Au have been irradiated by 100 MeV Ni ions with the fluence of 5 × 1013 ions cm−2 at room temperature. NPG is obtained by selectively etching Ge off from the Au matrix by dipping the Ge/Au thin film into 10 % H2O2 solution. Diffusion of Ge and Au across the interface under irradiation was confirmed by TRIM simulation and RBS spectra. The SEM image and EDX spectra confirms the formation of NPG with high purity. In addition, the statistical and fractal analysis of AFM image also confirms the formation of NPG. NPG system has been observed to show very good optical properties (low reflectance and high transmittance). The high quality NPG prepared by this method can be useful in the fields like optical sensors, transparent conductive electrodes, anti-reflective coatings, and photo-detector technology.
本文详细介绍了通过室温离子辐照开发纳米多孔金（NPG）的过程。100 MeV Ni 离子在室温下以 5 × 1013 离子 cm-2 的通量对 a-Ge/c-Au 双层薄膜进行了辐照。将 Ge/Au 薄膜浸入 10% H2O2 溶液中，选择性地蚀刻掉金基体上的 Ge，从而获得 NPG。通过 TRIM 模拟和 RBS 光谱证实了在辐照下 Ge 和 Au 在界面上的扩散。SEM 图像和 EDX 光谱证实了高纯度 NPG 的形成。此外，原子力显微镜图像的统计和分形分析也证实了 NPG 的形成。据观察，NPG 系统显示出非常好的光学特性（低反射率和高透射率）。用这种方法制备的高质量 NPG 可用于光学传感器、透明导电电极、抗反射涂层和光电探测器技术等领域。
{"title":"Development of nano-porous Au thin film at room temperature via ion irradiation in a-Ge/Au bilayer system followed by chemical etching of Ge","authors":"G. Maity , Geetika Patel , S. Ojha , S. Dubey , Shiv P. Patel , D. Kanjilal","doi":"10.1016/j.jcrysgro.2024.127951","DOIUrl":"10.1016/j.jcrysgro.2024.127951","url":null,"abstract":"<div><div>The development of nano-porous gold (NPG) via room temperature ion irradiation has been presented in detail. The bilayer thin films of <em>a</em>-Ge/<em>c</em>-Au have been irradiated by 100 MeV Ni ions with the fluence of 5 × 10<sup>13</sup> ions cm<sup>−2</sup> at room temperature. NPG is obtained by selectively etching Ge off from the Au matrix by dipping the Ge/Au thin film into 10 % H<sub>2</sub>O<sub>2</sub> solution. Diffusion of Ge and Au across the interface under irradiation was confirmed by TRIM simulation and RBS spectra. The SEM image and EDX spectra confirms the formation of NPG with high purity. In addition, the statistical and fractal analysis of AFM image also confirms the formation of NPG. NPG system has been observed to show very good optical properties (low reflectance and high transmittance). The high quality NPG prepared by this method can be useful in the fields like optical sensors, transparent conductive electrodes, anti-reflective coatings, and photo-detector technology.</div></div>","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"649 ","pages":"Article 127951"},"PeriodicalIF":1.7,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142535702","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-16DOI: 10.1016/j.jcrysgro.2024.127941
Hyeon-Cheol Kim, V. Janardhanam, Sameer Pokhrel, Chel-Jong Choi
The current–voltage and breakdown characteristics of Au/Ni/β-Ga2O3 Schottky barrier diodes were investigated as a function of β-Ga2O3 epilayer thickness in the range of 6–19 μm. The X-ray rocking curves indicated that the full-width half-maximum is reduced with increasing epilayer thickness, implying an improvement in the crystallinity of β-Ga2O3 epilayer. The barrier heights of the field-plated β-Ga2O3 Schottky barrier diode with epitaxial layer thickness of 6, 12, and 19 μm were obtained as 1.01, 1.03, and 1.04 eV, with the ideality factor values being 1.21, 1.19, and 1.46, respectively. The higher ideality factors could be associated with the existence of inhomogeneity at the metal–semiconductor interface. The series resistance of the Schottky diode obtained increased with increasing epilayer thickness. The Schottky diode fabricated on 19 μm thick epitaxial layer exhibited a higher breakdown voltage of 490 V. The increase in epilayer thickness led to the widening of depletion region, resulting in lower electric field over a larger distance. This could be a main cause of the enhancement of the breakdown voltage characteristics of β-Ga2O3 Schottky barrier diode.
{"title":"Epilayer thickness effect on the electrical and breakdown characteristics of vertical β-Ga2O3 Schottky barrier diode","authors":"Hyeon-Cheol Kim, V. Janardhanam, Sameer Pokhrel, Chel-Jong Choi","doi":"10.1016/j.jcrysgro.2024.127941","DOIUrl":"10.1016/j.jcrysgro.2024.127941","url":null,"abstract":"<div><div>The current–voltage and breakdown characteristics of Au/Ni/<em>β</em>-Ga<sub>2</sub>O<sub>3</sub> Schottky barrier diodes were investigated as a function of <em>β</em>-Ga<sub>2</sub>O<sub>3</sub> epilayer thickness in the range of 6–19 μm. The X-ray rocking curves indicated that the full-width half-maximum is reduced with increasing epilayer thickness, implying an improvement in the crystallinity of <em>β</em>-Ga<sub>2</sub>O<sub>3</sub> epilayer. The barrier heights of the field-plated <em>β</em>-Ga<sub>2</sub>O<sub>3</sub> Schottky barrier diode with epitaxial layer thickness of 6, 12, and 19 μm were obtained as 1.01, 1.03, and 1.04 eV, with the ideality factor values being 1.21, 1.19, and 1.46, respectively. The higher ideality factors could be associated with the existence of inhomogeneity at the metal–semiconductor interface. The series resistance of the Schottky diode obtained increased with increasing epilayer thickness. The Schottky diode fabricated on 19 μm thick epitaxial layer exhibited a higher breakdown voltage of 490 V. The increase in epilayer thickness led to the widening of depletion region, resulting in lower electric field over a larger distance. This could be a main cause of the enhancement of the breakdown voltage characteristics of <em>β</em>-Ga<sub>2</sub>O<sub>3</sub> Schottky barrier diode.</div></div>","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"649 ","pages":"Article 127941"},"PeriodicalIF":1.7,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142535698","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The effects of nitrogen (N) distribution on the electrical properties of GaAsN films were evaluated by intentionally changing the N distribution using atomic layer epitaxy (ALE) and post-annealing. The N distribution was controlled in the growth direction by growing superlattice (SL) thin films repeatedly growing 1 GaAsN layer and 0, 3, and 5 layers of GaAs by ALE. These films were referred to as (1:0), (1:3), and (1:5), respectively. To change the N distribution in the same thin film, N atoms were diffused by post-annealing. Changes in N distribution were evaluated by X-ray diffraction as changes in GaAsN superstructure. N atoms diffused from GaAsN layers to the adjacent layers in (1:3) films annealed above 750 °C, while they remained stable in those of (1:5) films annealed at temperatures up to 850 °C. The carrier mobility of both films increased monotonically with the annealing temperature. The concentration of ionized scattering centers decreased significantly in films annealed at 650 °C (independent of their N distributions) owing to the elimination of donor-type defects by annealing. Contrarily, the concentrations of N-induced scattering centers in (1:5) films annealed below 900 °C were similar, while those in (1:3) films annealed above 750 °C decreased significantly, in agreement with the N-atom diffusion behavior of GaAsN layers. Thus, N-distribution homogenization can be related to the reduction of N-induced scattering centers.
通过使用原子层外延（ALE）和后退火有意改变氮（N）分布，评估了氮（N）分布对氮化镓薄膜电性能的影响。通过原子层外延技术重复生长 1 层 GaAsN 和 0、3 和 5 层 GaAs，从而在生长方向上控制氮的分布。这些薄膜分别称为 (1:0)、(1:3) 和 (1:5)。为了改变同一薄膜中的 N 分布，通过后退火扩散 N 原子。N 分布的变化通过 X 射线衍射评估为 GaAsN 上层结构的变化。在 750 ℃ 以上退火的 (1:3) 薄膜中，N 原子从 GaAsN 层扩散到相邻层，而在温度高达 850 ℃ 的 (1:5) 薄膜中，N 原子保持稳定。两种薄膜的载流子迁移率都随退火温度的升高而单调增加。由于退火消除了供体型缺陷，在 650 ℃ 退火的薄膜中电离散射中心的浓度显著下降（与 N 分布无关）。相反，在低于 900 °C 退火的 (1:5) 薄膜中，N 诱导散射中心的浓度相似，而在高于 750 °C 退火的 (1:3) 薄膜中，N 诱导散射中心的浓度显著下降，这与 GaAsN 层的 N 原子扩散行为一致。因此，N 分布均匀化可能与 N 引起的散射中心减少有关。
{"title":"Electrical properties of GaAsN/GaAs-superlattice films with different N distributions fabricated by atomic layer epitaxy","authors":"Masahiro Kawano, Tomohiro Haraguchi, Hidetoshi Suzuki","doi":"10.1016/j.jcrysgro.2024.127915","DOIUrl":"10.1016/j.jcrysgro.2024.127915","url":null,"abstract":"<div><div>The effects of nitrogen (N) distribution on the electrical properties of GaAsN films were evaluated by intentionally changing the N distribution using atomic layer epitaxy (ALE) and post-annealing. The N distribution was controlled in the growth direction by growing superlattice (SL) thin films repeatedly growing 1 GaAsN layer and 0, 3, and 5 layers of GaAs by ALE. These films were referred to as (1:0), (1:3), and (1:5), respectively. To change the N distribution in the same thin film, N atoms were diffused by post-annealing. Changes in N distribution were evaluated by X-ray diffraction as changes in GaAsN superstructure. N atoms diffused from GaAsN layers to the adjacent layers in (1:3) films annealed above 750 °C, while they remained stable in those of (1:5) films annealed at temperatures up to 850 °C. The carrier mobility of both films increased monotonically with the annealing temperature. The concentration of ionized scattering centers decreased significantly in films annealed at 650 °C (independent of their N distributions) owing to the elimination of donor-type defects by annealing. Contrarily, the concentrations of N-induced scattering centers in (1:5) films annealed below 900 °C were similar, while those in (1:3) films annealed above 750 °C decreased significantly, in agreement with the N-atom diffusion behavior of GaAsN layers. Thus, N-distribution homogenization can be related to the reduction of N-induced scattering centers.</div></div>","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"649 ","pages":"Article 127915"},"PeriodicalIF":1.7,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142535705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Single-crystal anomalous X-ray scattering (AXS) experiments were conducted to investigate the cation distribution of calcium–niobium–gallium garnet (CNGG). AXS measurements suggested an ordered distribution of Nb at the octahedral site, and further structural refinement allowed us to obtain the structural formula Ca3Nb1.703(0) Ga3.162(2)O12. Ca was only located in the dodecahedral site, while Ga was distributed in the octa- and tetrahedral sites. The tetrahedral site had a significant number of vacancies at a ratio of one vacancy per unit cell, and the Nb/Ga occupation ratio at the octahedral site results in non-stoichiometric chemical composition of CNGG and its unique broad absorption wavelength.
The findings of this study can contribute to device fabrication, property optimization, and quality control processes related to CNGG.
为了研究钙铌镓石榴石（CNGG）的阳离子分布，我们进行了单晶反常 X 射线散射（AXS）实验。AXS 测量结果表明，铌有序地分布在八面体位置，进一步的结构细化使我们得到了 Ca3Nb1.703(0) Ga3.162(2)O12 的结构式。钙只位于十二面体位点，而镓则分布在八面体和四面体位点。四面体位点有大量空位，空位比为每单位晶胞一个，而八面体位点的铌/镓占据比导致了 CNGG 的非化学计量组成及其独特的宽吸收波长。
{"title":"Fine structural analysis of calcium–niobium–gallium garnet (CNGG) by single-crystal anomalous X-ray scattering","authors":"Ryo Yamane , Hiroaki Takeda , Takahiro Kuribayashi , Kazumasa Sugiyama , Tsuguo Fukuda","doi":"10.1016/j.jcrysgro.2024.127947","DOIUrl":"10.1016/j.jcrysgro.2024.127947","url":null,"abstract":"<div><div>Single-crystal anomalous X-ray scattering (AXS) experiments were conducted to investigate the cation distribution of calcium–niobium–gallium garnet (CNGG). AXS measurements suggested an ordered distribution of Nb at the octahedral site, and further structural refinement allowed us to obtain the structural formula Ca<sub>3</sub>Nb<sub>1.703(0)</sub> Ga<sub>3.162(2)</sub>O<sub>12</sub>. Ca was only located in the dodecahedral site, while Ga was distributed in the octa- and tetrahedral sites. The tetrahedral site had a significant number of vacancies at a ratio of one vacancy per unit cell, and the Nb/Ga occupation ratio at the octahedral site results in non-stoichiometric chemical composition of CNGG and its unique broad absorption wavelength.</div><div>The findings of this study can contribute to device fabrication, property optimization, and quality control processes related to CNGG.</div></div>","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"649 ","pages":"Article 127947"},"PeriodicalIF":1.7,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142535712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-14DOI: 10.1016/j.jcrysgro.2024.127940
Rukang Li
Several low-symmetry borate crystals, such as α-BiB3O6 (BiBO), YCa4O(BO3)3 (YCOB) and La2CaB10O19 (LCB) show not only promising nonlinear optical (NLO) properties but also other favorable physical properties like large electro-optic (EO) coefficients and exceptionally large piezoelectric constants. Those materials may serve as high temperature sensors and electro- or acoustic- modulators beyond their traditional applications in high power laser generations. The knowledge of their full property tensors are indispensable for their efficient and practical usages. Due to the low-symmetry nature, more none-zero matrix elements are present and those elements most likely are combined when measuring them. Therefore, experimental determinations of the full tensor elements are not always easy especially for those high rank tensors. In fact, though being discovered over several decades, some of the property tensor matrices are still missing. Recently it is shown that by applying a modified post-DFT LD (density functional theory + London dispersion) correction based on linear combination of atomic orbitals (LCAO) and B3LYP functional, many important material property tensors of BiBO crystal are calculated in unprecedented precisions. Among them, theoretical calculation of the refractive indices in the terahertz (THz) range was firstly achieved. The calculation also confirms that BiBO has an exceptional large piezoelectric constant d22 = 40 pC/N and largest free EO coefficients on the order of 10 pm/V among borate crystals. The same calculation has been extended to the other low-symmetry borate NLO crystals, including YCOB and LCB. With those calculated material constants, practical devices may be designed with preferable figure of merits over existing materials.
{"title":"Complete property tensors of some low-symmetry borate NLO crystals","authors":"Rukang Li","doi":"10.1016/j.jcrysgro.2024.127940","DOIUrl":"10.1016/j.jcrysgro.2024.127940","url":null,"abstract":"<div><div>Several low-symmetry borate crystals, such as α-BiB<sub>3</sub>O<sub>6</sub> (BiBO), YCa<sub>4</sub>O(BO<sub>3</sub>)<sub>3</sub> (YCOB) and La<sub>2</sub>CaB<sub>10</sub>O<sub>19</sub> (LCB) show not only promising nonlinear optical (NLO) properties but also other favorable physical properties like large electro-optic (EO) coefficients and exceptionally large piezoelectric constants. Those materials may serve as high temperature sensors and electro- or acoustic- modulators beyond their traditional applications in high power laser generations. The knowledge of their full property tensors are indispensable for their efficient and practical usages. Due to the low-symmetry nature, more none-zero matrix elements are present and those elements most likely are combined when measuring them. Therefore, experimental determinations of the full tensor elements are not always easy especially for those high rank tensors. In fact, though being discovered over several decades, some of the property tensor matrices are still missing. Recently it is shown that by applying a modified post-DFT LD (density functional theory + London dispersion) correction based on linear combination of atomic orbitals (LCAO) and B3LYP functional, many important material property tensors of BiBO crystal are calculated in unprecedented precisions. Among them, theoretical calculation of the refractive indices in the terahertz (THz) range was firstly achieved. The calculation also confirms that BiBO has an exceptional large piezoelectric constant <em>d</em><sub>22</sub> = 40 pC/N and largest free EO coefficients on the order of 10 pm/V among borate crystals. The same calculation has been extended to the other low-symmetry borate NLO crystals, including YCOB and LCB. With those calculated material constants, practical devices may be designed with preferable figure of merits over existing materials.</div></div>","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"649 ","pages":"Article 127940"},"PeriodicalIF":1.7,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142535704","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-13DOI: 10.1016/j.jcrysgro.2024.127911
D.V. Saparov
In recent years, to mitigate the effects of climate change, countries’ transition to the green economy has accelerated, and thereby, the demand of semiconductor industry for wide-gap semiconductors such as SiC and GaN has increased dramatically. These semiconductors are expensive. To reduce the price of the final product, industrial production of thin epitaxial films of sought-after semiconductors on accessible and cheap substrates, such as Si and sapphire, is being developed. When growing epitaxial films on foreign substrates, the resulting heterostructure bends, becomes concave or convex, due to a mismatch between the coefficients of thermal expansion (CTE) of the substrate and the epitaxial film. As a result, the quality of the epitaxial film deteriorates and further processing of the resulting heterostructures in production lines becomes difficult or even impossible. The essence of the proposed new method is that the epitaxial film is grown not on a flat, but on a pre-curved substrate with the expectation that after cooling the fabricated heterostructure to room temperature, the heterostructure will take a flat shape due to the difference in the CTE of the epitaxial film and the substrate. A round bimetallic plate, located under the substrate, bends the substrate in the required direction to the desired value at the growth temperature, and gradually reduces the bend of the fabricated heterostructure during cooling, in proportion to the thermal contraction of the epitaxial film. This allows obtaining qualitative and flat epitaxial films, regardless of the material of the substrate or epitaxial film and the diameter of the substrate or thickness of the epitaxial film, without any buffer layers or carrying out any additional operations and costs.
近年来，为减缓气候变化的影响，各国加快了向绿色经济转型的步伐，半导体行业对 SiC 和 GaN 等宽隙半导体的需求也因此大幅增加。这些半导体价格昂贵。为了降低最终产品的价格，正在开发在硅和蓝宝石等容易获得且廉价的基底上工业化生产所需的半导体外延薄膜。在国外基底上生长外延薄膜时，由于基底和外延薄膜的热膨胀系数（CTE）不匹配，产生的异质结构会弯曲、变凹或变凸。因此，外延薄膜的质量会下降，在生产线上进一步加工所产生的异质结构会变得困难甚至不可能。所建议的新方法的本质是，外延薄膜不是生长在平面上，而是生长在预弯曲的基底上，期望在将所制造的异质结构冷却到室温后，由于外延薄膜和基底的 CTE 不同，异质结构将呈现平面形状。位于基底下方的圆形双金属片可在生长温度下将基底向所需方向弯曲至所需值，并在冷却过程中根据外延薄膜的热收缩比例逐渐减小所制造异质结构的弯曲度。这样，无论基底或外延膜的材料如何，也无论基底的直径或外延膜的厚度如何，都能获得优质平整的外延膜，而无需任何缓冲层，也无需进行任何额外的操作和成本。
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Pub Date : 2024-10-12DOI: 10.1016/j.jcrysgro.2024.127937
Furqanul Hassan Naqvi, Syed Bilal Junaid, Jae-Hyeon Ko
Halide mixing effects on the elastic and vibrational properties were investigated for FAPbBr1.5Cl1.5 single crystals. The elastic and vibrational characteristics of the synthesized single crystal were examined using temperature-dependent Brillouin and Raman spectroscopies. Elastic constants C11 and C44 were derived from the longitudinal and transverse sound velocities, respectively. The softening and subsequent hardening of the elastic constants upon cooling was accompanied by substantial increase of the acoustic damping peaks indicating significant interaction between the acoustic waves and reorientational dynamics of the FA cations. Especially, FAPbBr1.5Cl1.5 exhibited extremely low shear rigidity compared to other MA-based perovskites. Raman spectroscopy was used to study the vibrational modes of the PbX6 octahedral lattice and the internal motions of FA cations. Raman modes did not reveal any drastic changes within the investigated temperature range. The combined elastic and vibrational properties showed that the structural phase transitions observed from pure compounds were suppressed in FAPbBr1.5Cl1.5 due to the local heterogeneous environment for the FA cations caused by random substitution of two halogen ions. These findings are expected to enhance the understanding of the material’s behavior under varying thermal conditions, which is crucial for optimizing the performance of perovskite-based devices.
研究了卤化物混合对 FAPbBr1.5Cl1.5 单晶的弹性和振动特性的影响。利用随温度变化的布里渊光谱和拉曼光谱研究了合成单晶的弹性和振动特性。弹性常数 C11 和 C44 分别来自纵向和横向声速。冷却时弹性常数的软化和随后的硬化伴随着声学阻尼峰的大幅增加，这表明声波与 FA 阳离子的重取向动力学之间存在显著的相互作用。特别是，与其他基于 MA 的包晶相比，FAPbBr1.5Cl1.5 表现出极低的剪切刚度。拉曼光谱被用来研究 PbX6 八面体晶格的振动模式和 FA 阳离子的内部运动。在所研究的温度范围内，拉曼模式没有发生任何剧烈变化。弹性和振动特性的综合结果表明，在 FAPbBr1.5Cl1.5 中，由于两个卤素离子的随机置换造成了 FA 阳离子的局部异质环境，从纯化合物中观察到的结构相变受到了抑制。这些发现有望加深人们对该材料在不同热条件下行为的理解，这对于优化基于包晶的器件性能至关重要。
{"title":"Elastic and vibrational properties of Formamidinium based mixed halide perovskites","authors":"Furqanul Hassan Naqvi, Syed Bilal Junaid, Jae-Hyeon Ko","doi":"10.1016/j.jcrysgro.2024.127937","DOIUrl":"10.1016/j.jcrysgro.2024.127937","url":null,"abstract":"<div><div>Halide mixing effects on the elastic and vibrational properties were investigated for FAPbBr<sub>1.5</sub>Cl<sub>1.5</sub> single crystals. The elastic and vibrational characteristics of the synthesized single crystal were examined using temperature-dependent Brillouin and Raman spectroscopies. Elastic constants <em>C</em><sub>11</sub> and <em>C</em><sub>44</sub> were derived from the longitudinal and transverse sound velocities, respectively. The softening and subsequent hardening of the elastic constants upon cooling was accompanied by substantial increase of the acoustic damping peaks indicating significant interaction between the acoustic waves and reorientational dynamics of the FA cations. Especially, FAPbBr<sub>1.5</sub>Cl<sub>1.5</sub> exhibited extremely low shear rigidity compared to other MA-based perovskites. Raman spectroscopy was used to study the vibrational modes of the PbX<sub>6</sub> octahedral lattice and the internal motions of FA cations. Raman modes did not reveal any drastic changes within the investigated temperature range. The combined elastic and vibrational properties showed that the structural phase transitions observed from pure compounds were suppressed in FAPbBr<sub>1.5</sub>Cl<sub>1.5</sub> due to the local heterogeneous environment for the FA cations caused by random substitution of two halogen ions. These findings are expected to enhance the understanding of the material’s behavior under varying thermal conditions, which is crucial for optimizing the performance of perovskite-based devices.</div></div>","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"649 ","pages":"Article 127937"},"PeriodicalIF":1.7,"publicationDate":"2024-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142446628","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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