Pub Date : 2024-10-09DOI: 10.1016/j.jcrysgro.2024.127924
Kimberly S. Pestovich , Luis Stand , Nicholas Anastasi , Megan A. Gillespie , Lakshmi S. Pandian , Charles L. Melcher , Edgar van Loef , Mariya Zhuravleva
Scintillators play crucial roles in homeland security applications like gamma ray spectroscopy and high energy X-ray radiography. For promising new scintillators, fine-tuning the luminescent dopant concentration is one avenue to further improve their performance and tailor their properties. In this work, the effects of europium dopant concentrations on the crystal growth, luminescence and scintillation properties of RbSr2Br5 and RbSr2I5 crystals was investigated. Nine transparent 7 mm diameter single crystals were grown via the Vertical Bridgman method. The optical band gap of RbSr2Br5 was 5.9 eV and that of RbSr2I5 was 4.7 eV. High scintillation performance was achieved with a relatively low europium concentration of 1 mol%. For both RbSr2Br5:Eu and RbSr2I5:Eu crystals, light yield of 60–90,000 ph/MeV, energy resolution 2.8–4.0 % at 662 keV, and X-ray afterglow 0.79–1.5 % at 2 ms were obtained.
{"title":"Intrinsic scintillation performance & europium concentration effects in RbSr2I5 and RbSr2Br5 scintillators","authors":"Kimberly S. Pestovich , Luis Stand , Nicholas Anastasi , Megan A. Gillespie , Lakshmi S. Pandian , Charles L. Melcher , Edgar van Loef , Mariya Zhuravleva","doi":"10.1016/j.jcrysgro.2024.127924","DOIUrl":"10.1016/j.jcrysgro.2024.127924","url":null,"abstract":"<div><div>Scintillators play crucial roles in homeland security applications like gamma ray spectroscopy and high energy X-ray radiography. For promising new scintillators, fine-tuning the luminescent dopant concentration is one avenue to further improve their performance and tailor their properties. In this work, the effects of europium dopant concentrations on the crystal growth, luminescence and scintillation properties of RbSr<sub>2</sub>Br<sub>5</sub> and RbSr<sub>2</sub>I<sub>5</sub> crystals was investigated. Nine transparent 7 mm diameter single crystals were grown via the Vertical Bridgman method. The optical band gap of RbSr<sub>2</sub>Br<sub>5</sub> was 5.9 eV and that of RbSr<sub>2</sub>I<sub>5</sub> was 4.7 eV. High scintillation performance was achieved with a relatively low europium concentration of 1 mol%. For both RbSr<sub>2</sub>Br<sub>5</sub>:Eu and RbSr<sub>2</sub>I<sub>5</sub>:Eu crystals, light yield of 60–90,000 ph/MeV, energy resolution 2.8–4.0 % at 662 keV, and X-ray afterglow 0.79–1.5 % at 2 ms were obtained.</div></div>","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"649 ","pages":"Article 127924"},"PeriodicalIF":1.7,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142433756","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}
Results of a thermodynamic study of Sn doping and fabrication of a Sn-doped GaN freestanding layer with high structural quality by halide vapor phase epitaxy (HVPE) are described in this paper. Thermodynamic analysis revealed that SnCl2 and/or SnCl act as Sn precursors through the reaction between Sn metal and HCl gas. The equilibrium partial pressures of SnCl2 and SnCl increase with the input HCl partial pressure. To generate Sn precursors effectively, it is desirable that the reaction between Sn metal and HCl gas occurs in the inert gas ambient. On the basis of results of the thermodynamic study, the Sn-doped GaN freestanding layer with a Sn concentration of 5.7 × 1019 cm−3 is fabricated by removing the GaN seed substrate after HVPE growth. The Sn-doped GaN freestanding layer has high crystal quality, and the lattice constants along the c- and a-axes of the Sn-doped GaN freestanding layer are larger than those of the GaN seed substrate because of the high electron density and the size effect of Sn atoms.
本文介绍了锡掺杂的热力学研究结果，以及通过卤化物气相外延（HVPE）制造出具有高结构质量的锡掺杂氮化镓独立层。热力学分析表明，SnCl2 和/或 SnCl 通过金属锡和 HCl 气体之间的反应充当了锡前驱体。SnCl2 和 SnCl 的平衡分压随输入 HCl 分压的增加而增加。为了有效地生成锡前驱体，金属锡和 HCl 气体之间的反应最好在惰性气体环境中进行。根据热力学研究的结果，在 HVPE 生长后移除 GaN 种子衬底，制备出 Sn 浓度为 5.7 × 1019 cm-3 的掺锡 GaN 独立层。掺Sn的独立GaN层具有很高的晶体质量，由于高电子密度和Sn原子的尺寸效应，掺Sn的独立GaN层沿c轴和a轴的晶格常数大于GaN种子衬底的晶格常数。
{"title":"Sn-doped n-type GaN freestanding layer: Thermodynamic study and fabrication by halide vapor phase epitaxy","authors":"Kazuki Ohnishi , Kansuke Hamasaki , Shugo Nitta , Naoki Fujimoto , Hirotaka Watanabe , Yoshio Honda , Hiroshi Amano","doi":"10.1016/j.jcrysgro.2024.127923","DOIUrl":"10.1016/j.jcrysgro.2024.127923","url":null,"abstract":"<div><div>Results of a thermodynamic study of Sn doping and fabrication of a Sn-doped GaN freestanding layer with high structural quality by halide vapor phase epitaxy (HVPE) are described in this paper. Thermodynamic analysis revealed that SnCl<sub>2</sub> and/or SnCl act as Sn precursors through the reaction between Sn metal and HCl gas. The equilibrium partial pressures of SnCl<sub>2</sub> and SnCl increase with the input HCl partial pressure. To generate Sn precursors effectively, it is desirable that the reaction between Sn metal and HCl gas occurs in the inert gas ambient. On the basis of results of the thermodynamic study, the Sn-doped GaN freestanding layer with a Sn concentration of 5.7 × 10<sup>19</sup> cm<sup>−3</sup> is fabricated by removing the GaN seed substrate after HVPE growth. The Sn-doped GaN freestanding layer has high crystal quality, and the lattice constants along the <em>c</em>- and <em>a</em>-axes of the Sn-doped GaN freestanding layer are larger than those of the GaN seed substrate because of the high electron density and the size effect of Sn atoms.</div></div>","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"648 ","pages":"Article 127923"},"PeriodicalIF":1.7,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419159","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 : 2024-10-09DOI: 10.1016/j.jcrysgro.2024.127928
Sembinova Aigul , Enkhtuvshin Enkhbayar , Ashish Gaur , HyukSu Han
Electrochemical water splitting is one of the most promising methods for sustainable production of green hydrogen. The oxygen evolution reaction (OER) is a crucial step in the process of water splitting. However, it exhibits sluggish kinetics and requires a significant overpotential for functioning at reasonable reaction rates. The efficiency of the reaction can be enhanced by reducing the overpotential, lowering the energy barrier, and using an effective electrocatalyst. Transition metal-based catalysts are well studied for this purpose. Specially, nickel–cobalt (Ni-Co) based catalysts have been regarded as the best OER electrocatalysts. Therefore, several studies have been carried out to enhance the electrocatalytic efficiency of Ni-Co catalysts. While mixing other transition metals with Ni-Co is a straightforward and reliable method to improve the OER activity of Ni-Co catalysts, there is still a need for a thorough examination of the design of Ni-Co catalysts with various additional elements. Seawater electrolysis, which utilizes abundant water resources that constitute over 97% of the world’s water, is highly appealing for sustainable energy production. To achieve commercial feasibility, scientists are striving to solve challenges, such as corrosion resistance, high overpotential, and the need for efficient and durable electrocatalysts.
In this study, we fabricated a transition metal-based trimetallic catalyst (CNF), consisting of cobalt (Co), nickel (Ni), and iron (Fe). Furthermore, CNF was doped with chromium (Cr-doped CNF) and tested for the OER in alkaline freshwater and alkaline seawater. Our Cr-doped trimetallic CNF catalyst demonstrates exceptional performance in both seawater and freshwater, with overpotential of 320 mV and 280 mV at 10 mA cm−2 current density, making it a promising candidate for large-scale, sustainable hydrogen production.
电化学水分离是可持续生产绿色氢气的最有前途的方法之一。氧进化反应（OER）是水分离过程中的关键步骤。然而，它表现出迟缓的动力学特性，需要很大的过电位才能以合理的反应速率运行。通过降低过电位、降低能垒和使用有效的电催化剂，可以提高反应的效率。为此，人们对过渡金属催化剂进行了深入研究。特别是以镍-钴（Ni-Co）为基础的催化剂被认为是最好的 OER 电催化剂。因此，为了提高镍钴催化剂的电催化效率，已经开展了多项研究。虽然将其他过渡金属与镍-钴混合是提高镍-钴催化剂 OER 活性的一种直接而可靠的方法，但仍有必要对含有各种附加元素的镍-钴催化剂的设计进行深入研究。海水电解利用了占世界总水量 97% 以上的丰富水资源，对可持续能源生产具有极大的吸引力。为了实现商业可行性，科学家们正在努力解决各种挑战，例如耐腐蚀性、高过电位以及对高效耐用电催化剂的需求。此外，CNF 还掺杂了铬（掺铬 CNF），并在碱性淡水和碱性海水中进行了 OER 测试。我们掺杂铬的三金属 CNF 催化剂在海水和淡水中均表现出卓越的性能，在 10 mA cm-2 电流密度下的过电位分别为 320 mV 和 280 mV，因此有望成为大规模、可持续制氢的候选催化剂。
{"title":"Cr-doped tri-metallic nano prism catalyst for efficient alkaline and seawater splitting","authors":"Sembinova Aigul , Enkhtuvshin Enkhbayar , Ashish Gaur , HyukSu Han","doi":"10.1016/j.jcrysgro.2024.127928","DOIUrl":"10.1016/j.jcrysgro.2024.127928","url":null,"abstract":"<div><div>Electrochemical water splitting is one of the most promising methods for sustainable production of green hydrogen. The oxygen evolution reaction (OER) is a crucial step in the process of water splitting. However, it exhibits sluggish kinetics and requires a significant overpotential for functioning at reasonable reaction<!--> <!-->rates. The efficiency of the reaction can be enhanced by reducing the overpotential, lowering the energy barrier, and using an effective electrocatalyst. Transition metal-based<!--> <!-->catalysts are well studied for this purpose. Specially, nickel–cobalt (Ni-Co) based catalysts have been regarded as the best OER electrocatalysts. Therefore, several studies have been carried out to enhance the electrocatalytic efficiency of Ni-Co catalysts. While mixing other transition metals with Ni-Co is a straightforward and reliable method to improve the OER activity of Ni-Co catalysts, there is still a need for a thorough examination of the design of Ni-Co catalysts with various additional elements. Seawater electrolysis, which utilizes abundant water resources that constitute over 97% of the world’s water, is highly appealing for sustainable energy production. To achieve commercial feasibility, scientists are striving to solve challenges, such as corrosion resistance, high<!--> <!-->overpotential, and the need for efficient and durable electrocatalysts.</div><div>In this study, we fabricated a transition metal-based trimetallic catalyst (CNF), consisting of cobalt (Co), nickel (Ni), and iron (Fe). Furthermore, CNF was doped with chromium (Cr-doped CNF) and tested for the OER in alkaline freshwater and alkaline seawater. Our Cr-doped trimetallic CNF catalyst demonstrates exceptional performance in both seawater and freshwater, with overpotential of 320 mV and 280 mV at 10 mA cm<sup>−2</sup> current density, making it a promising candidate for large-scale, sustainable hydrogen production.</div></div>","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"649 ","pages":"Article 127928"},"PeriodicalIF":1.7,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142433638","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 : 2024-10-09DOI: 10.1016/j.jcrysgro.2024.127929
Bohui Xu , Pifu Gong , Zheshuai Lin
SO3NH3 (Sulfamic acid, or SA) is known for its excellent piezoelectric and optical properties, making it valuable for various optical applications. However, it usually takes weeks to months to grow the SA single crystals with centimeter-scale size by traditional growth method from solution. In this study, we use (CH3)3SBr (Me3SBr) as an additive to enhance the growth rate of SA single crystals, and the growth time was reduced to just 48 h. The mechanism of accelerated crystallization process is attributed to the variations of electrostatic potential and binding energy on SA crystal modified by the additive. In addition, structural analysis and basic characterization on the newly grown SA are performed, and first-principles calculations provide insights into the energy band structure and phonon spectrum.
SO3NH3（氨基磺酸，简称 SA）以其优异的压电和光学特性而闻名，因此在各种光学应用中具有重要价值。然而，采用传统的溶液生长法通常需要数周至数月的时间才能生长出厘米级大小的氨基磺酸单晶。本研究中，我们使用 (CH3)3SBr (Me3SBr) 作为添加剂来提高 SA 单晶的生长速度，并将生长时间缩短至 48 小时。加速结晶过程的机理是由于添加剂改变了 SA 晶体上的静电势和结合能。此外，还对新生长的 SA 进行了结构分析和基本表征，并通过第一原理计算深入了解了其能带结构和声子谱。
{"title":"SO3NH3 crystal growth in (CH3)3SBr solution","authors":"Bohui Xu , Pifu Gong , Zheshuai Lin","doi":"10.1016/j.jcrysgro.2024.127929","DOIUrl":"10.1016/j.jcrysgro.2024.127929","url":null,"abstract":"<div><div>SO<sub>3</sub>NH<sub>3</sub> (Sulfamic acid, or SA) is known for its excellent piezoelectric and optical properties, making it valuable for various optical applications. However, it usually takes weeks to months to grow the SA single crystals with centimeter-scale size by traditional growth method from solution. In this study, we use (CH<sub>3</sub>)<sub>3</sub>SBr (Me<sub>3</sub>SBr) as an additive to enhance the growth rate of SA single crystals, and the growth time was reduced to just 48 h. The mechanism of accelerated crystallization process is attributed to the variations of electrostatic potential and binding energy on SA crystal modified by the additive. In addition, structural analysis and basic characterization on the newly grown SA are performed, and first-principles calculations provide insights into the energy band structure and phonon spectrum.</div></div>","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"648 ","pages":"Article 127929"},"PeriodicalIF":1.7,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419158","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}
{"title":"Preparation of SiC coatings on graphite substrates via CVD using polysilaethylene","authors":"Hiroki Sato , Takashi Goto , Atsushi Okuno , Akira Yoshikawa","doi":"10.1016/j.jcrysgro.2024.127931","DOIUrl":"10.1016/j.jcrysgro.2024.127931","url":null,"abstract":"","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"649 ","pages":"Article 127931"},"PeriodicalIF":1.7,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142433755","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 : 2024-10-09DOI: 10.1016/j.jcrysgro.2024.127920
Amir Reza Ansari Dezfoli
As the semiconductor industry shifts towards larger wafer sizes, such as 300 mm and 450 mm, controlling defects is crucial to ensure device performance and yield. Conversely, a high cooling rate is essential for achieving higher production rates. Therefore, finding the optimal cooling strategy is critical to maintaining high production rates while ensuring high-quality wafer production. This paper employs a simulation model to investigate the impact of various cooling strategies on point defect formation during the CZ process for 450 mm diameter silicon ingots. Using the 3D energy equation coupled with the Navier-Stokes equation and moving mesh theory, the transient CZ process is simulated, incorporating defect evaluation equations. Beside original CZ puller configuration, two cooling strategies are examined: one with a small gap and long cooling jacket (Case II) and another with a large gap and short cooling jacket (Case III), compared against a baseline setup (Case I). The simulations reveal that Case II, while enhancing the crystallization rate, increases non-uniformity. Conversely, Case III produces a flatter solid-liquid interface and lower defect concentrations, achieving a maximum Cv-Ci of 0.4 × 1014 cm−3, compared to 1.1 × 1014 cm−3 and -2.5 × 1014 cm−3 in Case I and II. These findings suggest that adjusting cooling strategies can significantly impact the quality and uniformity of large- diameter silicon ingots.
随着半导体行业向 300 毫米和 450 毫米等更大晶圆尺寸转变，控制缺陷对于确保设备性能和产量至关重要。相反，高冷却率对于实现更高的生产率至关重要。因此，找到最佳冷却策略对于保持高生产率同时确保高质量晶圆生产至关重要。本文采用仿真模型来研究 450 毫米直径硅锭 CZ 工艺过程中各种冷却策略对点缺陷形成的影响。利用三维能量方程、纳维-斯托克斯方程和移动网格理论，模拟了瞬态 CZ 过程，并纳入了缺陷评估方程。除了原始的 CZ 拉拔器配置外，还研究了两种冷却策略：一种是小间隙和长冷却套（情况 II），另一种是大间隙和短冷却套（情况 III），并与基准设置（情况 I）进行了比较。模拟结果表明，情况 II 在提高结晶速率的同时，也增加了不均匀性。相反，情况 III 产生了更平坦的固液界面和更低的缺陷浓度，最大 Cv-Ci 为 0.4 × 1014 cm-3，而情况 I 和情况 II 分别为 1.1 × 1014 cm-3 和 -2.5 × 1014 cm-3。这些研究结果表明，调整冷却策略可显著影响大直径硅锭的质量和均匀性。
{"title":"Optimizing cooling strategies in the Czochralski process for large-diameter silicon ingots","authors":"Amir Reza Ansari Dezfoli","doi":"10.1016/j.jcrysgro.2024.127920","DOIUrl":"10.1016/j.jcrysgro.2024.127920","url":null,"abstract":"<div><div>As the semiconductor industry shifts towards larger wafer sizes, such as 300 mm and 450 mm, controlling defects is crucial to ensure device performance and yield. Conversely, a high cooling rate is essential for achieving higher production rates. Therefore, finding the optimal cooling strategy is critical to maintaining high production rates while ensuring high-quality wafer production. This paper employs a simulation model to investigate the impact of various cooling strategies on point defect formation during the CZ process for 450 mm diameter silicon ingots. Using the 3D energy equation coupled with the Navier-Stokes equation and moving mesh theory, the transient CZ process is simulated, incorporating defect evaluation equations. Beside original CZ puller configuration, two cooling strategies are examined: one with a small gap and long cooling jacket (Case II) and another with a large gap and short cooling jacket (Case III), compared against a baseline setup (Case I). The simulations reveal that Case II, while enhancing the crystallization rate, increases non-uniformity. Conversely, Case III produces a flatter solid-liquid interface and lower defect concentrations, achieving a maximum Cv-Ci of 0.4 × 10<sup>14</sup> cm<sup>−3</sup>, compared to 1.1 × 10<sup>14</sup> cm<sup>−3</sup> and -2.5 × 10<sup>14</sup> cm<sup>−3</sup> in Case I and II. These findings suggest that adjusting cooling strategies can significantly impact the quality and uniformity of large- diameter silicon ingots.</div></div>","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"649 ","pages":"Article 127920"},"PeriodicalIF":1.7,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142434035","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 : 2024-10-09DOI: 10.1016/j.jcrysgro.2024.127921
Amir Reza Ansari Dezfoli
{"title":"Review of simulation and modeling techniques for silicon Czochralski crystal growth","authors":"Amir Reza Ansari Dezfoli","doi":"10.1016/j.jcrysgro.2024.127921","DOIUrl":"10.1016/j.jcrysgro.2024.127921","url":null,"abstract":"","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"648 ","pages":"Article 127921"},"PeriodicalIF":1.7,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419157","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 exploration of ultraviolet (UV) nonlinear optical (NLO) crystals is of great significance in various fields, such as optical communication, medical diagnosis, deep space exploration and optical digital signal processing. Accordingly, cyanurates attracted widespread attention due to their strong second-harmonic-generation (SHG) effects, large birefringence for phase-matching, short UV cutoffs, high solar blind transmittances and easy crystal preparations. This article reviews the optical properties of so far reported cyanurate NLO crystals, describes the preparation approaches of cyanurates, compares their structures to further analyze the source of their large SHG effect, and provides some insights for designing and synthesizing new UV cyanurates in the future.
{"title":"Nonlinear optical cyanurate crystals","authors":"Xianghe Meng , Haotian Tian , Qian Wu , Mingjun Xia","doi":"10.1016/j.jcrysgro.2024.127930","DOIUrl":"10.1016/j.jcrysgro.2024.127930","url":null,"abstract":"<div><div>The exploration of ultraviolet (UV) nonlinear optical (NLO) crystals is of great significance in various fields, such as optical communication, medical diagnosis, deep space exploration and optical digital signal processing. Accordingly, cyanurates attracted widespread attention due to their strong second-harmonic-generation (SHG) effects, large birefringence for phase-matching, short UV cutoffs, high solar blind transmittances and easy crystal preparations. This article reviews the optical properties of so far reported cyanurate NLO crystals, describes the preparation approaches of cyanurates, compares their structures to further analyze the source of their large SHG effect, and provides some insights for designing and synthesizing new UV cyanurates in the future.</div></div>","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"648 ","pages":"Article 127930"},"PeriodicalIF":1.7,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419161","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 : 2024-10-09DOI: 10.1016/j.jcrysgro.2024.127926
Jeong Hun Park, Il Won Kim
Nanocrystal formation is an effective method to increase the dissolution of drug compounds with limited solubilities. Niclosamide is a sparingly soluble compound, and it also tends to become an even less soluble monohydrate upon contact with dissolution media. We utilized freeze drying to successfully generate niclosamide nanocrystals, which displayed rapid initial dissolution but also suffered from the expedited formation of the monohydrate. Therefore, we explored some pharmaceutically acceptable polymers to overcome the unfavorable anhydrate-to-monohydrate transformation. Poly(vinylpyrrolidone-co-vinyl acetate) (Mw 45000–70000) effectively retarded the monohydrate formation in a concentration-dependent manner, and 3–5% in the drug-polymer mixture was enough to sustain the enhanced initial dissolution of niclosamide nanocrystals. The area under the dissolution curve tripled due to the combined effect of the nanocrystal formation and the monohydrate inhibition. This study demonstrates an example of the one-pot freeze-drying process to form an optimized drug-additive mixture to realize the full potential of drug nanocrystals.
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This research explores the complex influence of nitrogen concentration and substrate temperature on the resultant properties of polycrystalline diamond (PCD) films grown by microwave plasma chemical vapor deposition (CVD). In particular, we investigated the growth parameters to find the exact conditions for changing the morphology of the resulting film from microcrystalline (MCD) to nanocrystalline (NCD). A series of 2 µm-thick polycrystalline diamond films was grown on Si substrates in methane-hydrogen–nitrogen gas mixtures with varied: (i) nitrogen concentration (0–2 %) and (ii) substrate temperature (700–1050 °C). Comprehensive characterization techniques, including scanning electron microscopy (SEM), micro-Raman spectroscopy, and X-ray diffraction, were employed to assess the morphological, structural, and spectroscopic properties of the films. The study reveals that even minor additions of nitrogen significantly modulate secondary nucleation, impacting both film morphology and phase composition. Furthermore, substrate temperature emerges as another critical parameter, influencing the growth kinetics and crystallite size. The comparison of the characteristics of grown PCD films allowed us to find conditions for the formation of NCD films with minimal surface roughness and maximal growth rate: nitrogen concentration [N2] ≈ 0.2–0.5 % and temperature T ≈ 850–900 °C. These findings can be used to optimize the CVD synthesis parameters of PCD films for applications as protective or friction-reducing layers, as well as for superhard cutting tools and optical devices.
{"title":"Microcrystalline and nanocrystalline structure of diamond films grown by MPCVD with nitrogen additions: Study of transitional synthesis conditions","authors":"Artem Martyanov , Ivan Tiazhelov , Sergey Savin , Valery Voronov , Alexey Popovich , Vadim Sedov","doi":"10.1016/j.jcrysgro.2024.127916","DOIUrl":"10.1016/j.jcrysgro.2024.127916","url":null,"abstract":"<div><div>This research explores the complex influence of nitrogen concentration and substrate temperature on the resultant properties of polycrystalline diamond (PCD) films grown by microwave plasma chemical vapor deposition (CVD). In particular, we investigated the growth parameters to find the exact conditions for changing the morphology of the resulting film from microcrystalline (MCD) to nanocrystalline (NCD). A series of 2 µm-thick polycrystalline diamond films was grown on Si substrates in methane-hydrogen–nitrogen gas mixtures with varied: (i) nitrogen concentration (0–2 %) and (ii) substrate temperature (700–1050 °C). Comprehensive characterization techniques, including scanning electron microscopy (SEM), micro-Raman spectroscopy, and X-ray diffraction, were employed to assess the morphological, structural, and spectroscopic properties of the films. The study reveals that even minor additions of nitrogen significantly modulate secondary nucleation, impacting both film morphology and phase composition. Furthermore, substrate temperature emerges as another critical parameter, influencing the growth kinetics and crystallite size. The comparison of the characteristics of grown PCD films allowed us to find conditions for the formation of NCD films with minimal surface roughness and maximal growth rate: nitrogen concentration [N<sub>2</sub>] ≈ 0.2–0.5 % and temperature T ≈ 850–900 °C. These findings can be used to optimize the CVD synthesis parameters of PCD films for applications as protective or friction-reducing layers, as well as for superhard cutting tools and optical devices.</div></div>","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"648 ","pages":"Article 127916"},"PeriodicalIF":1.7,"publicationDate":"2024-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419074","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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