Pub Date : 2024-11-29DOI: 10.1016/j.jcrysgro.2024.128026
Elona Khan , Valery Ryabov , Maria Samoilova , Ekaterina Simonova , Konstantin Kokh
The present study concerns the Li2O-B2O3-MoO3-LiF system. LiB3O5 and Li3B7O12 crystals were obtained by spontaneous crystallisation and TSSG. The addition of LiF to the molybdate flux represents a promising avenue for the growth of lithium borate crystals.
{"title":"Modification of molybdate flux with LiF for LiB3O5 crystal growth","authors":"Elona Khan , Valery Ryabov , Maria Samoilova , Ekaterina Simonova , Konstantin Kokh","doi":"10.1016/j.jcrysgro.2024.128026","DOIUrl":"10.1016/j.jcrysgro.2024.128026","url":null,"abstract":"<div><div>The present study concerns the Li<sub>2</sub>O-B<sub>2</sub>O<sub>3</sub>-MoO<sub>3</sub>-LiF system. LiB<sub>3</sub>O<sub>5</sub> and Li<sub>3</sub>B<sub>7</sub>O<sub>12</sub> crystals were obtained by spontaneous crystallisation and TSSG. The addition of LiF to the molybdate flux represents a promising avenue for the growth of lithium borate crystals.</div></div>","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"652 ","pages":"Article 128026"},"PeriodicalIF":1.7,"publicationDate":"2024-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142745752","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 : 2024-11-26DOI: 10.1016/j.jcrysgro.2024.128017
Sana Islam , Imran Aslam , Tariq Mahmood , M. Hassan Farooq
WO3·H2O nanostructures have fascinated momentous consideration due to their distinctive properties such as small bandgaps as compared to WO3, tunable morphology, and distinct photocatalytic properties. These nanostructures were successfully fabricated by the hydrothermal method (by varying solvent volume) and characterized by X-ray diffraction (XRD), EDX, and FESEM to analyze the crystallinity, chemical composition, and morphology which indicated the average size of 140–190 nm. The presence of O-W-O and O = W chemical bonds, and O–H stretching vibrations in FTIR spectrum demonstrate the fabrication of WO3·H2O nanostructures. The UV–Visible spectroscopy and PL study were conducted which presented that the optical bandgaps lies in the range (2.16–2.5 eV) which were beneficial for photocatalytic activity. To assess the photocatalytic response, rhodamine B, methyl orange, reactive orange 16 dyes and additionally industrial wastewater were used. It was noted that the photodegradation efficiency of sample 1 was higher than other samples for all dyes. The percentage degradation for RhB (99.5 %), MO (97.5 %), RO16 (88.7 %), and IW (99.5 %) and the reaction rate constants are RhB (0.0768 min−1), MO (0.03991 min−1), RO16 (0.02363 min−1), and IW (0.0744 min−1). The sample 1 have 1.5 times higher photocatalytic properties than all other samples, attributed to its lowest bandgap 2.16 eV, and lower charge carriers recombination rate. Moreover, the electrochemical properties of WO3·H2O nanostructures were also evaluated presenting a specific capacitance of 1209F g−1. This analysis highlights their potential in environmental remediation and supercapacitor applications.
{"title":"Facile synthesis of WO3.H2O nanostructures for efficient photocatalytic and electrochemical properties","authors":"Sana Islam , Imran Aslam , Tariq Mahmood , M. Hassan Farooq","doi":"10.1016/j.jcrysgro.2024.128017","DOIUrl":"10.1016/j.jcrysgro.2024.128017","url":null,"abstract":"<div><div>WO<sub>3</sub>·H<sub>2</sub>O nanostructures have fascinated momentous consideration due to their distinctive properties such as small bandgaps as compared to WO<sub>3</sub>, tunable morphology, and distinct photocatalytic properties. These nanostructures were successfully fabricated by the hydrothermal method (by varying solvent volume) and characterized by X-ray diffraction (XRD), EDX, and FESEM to analyze the crystallinity, chemical composition, and morphology which indicated the average size of 140–190 nm. The presence of O-W-O and O = W chemical bonds, and O–H stretching vibrations in FTIR spectrum demonstrate the fabrication of WO<sub>3</sub>·H<sub>2</sub>O nanostructures. The UV–Visible spectroscopy and PL study were conducted which presented that the optical bandgaps lies in the range (2.16–2.5 eV) which were beneficial for photocatalytic activity. To assess the photocatalytic response, rhodamine B, methyl orange, reactive orange 16 dyes and additionally industrial wastewater were used. It was noted that the photodegradation efficiency of sample 1 was higher than other samples for all dyes. The percentage degradation for RhB (99.5 %), MO (97.5 %), RO16 (88.7 %), and IW (99.5 %) and the reaction rate constants are RhB (0.0768 min<sup>−1</sup>), MO (0.03991 min<sup>−1</sup>), RO16 (0.02363 min<sup>−1</sup>), and IW (0.0744 min<sup>−1</sup>). The sample 1 have 1.5 times higher photocatalytic properties than all other samples, attributed to its lowest bandgap 2.16 eV, and lower charge carriers recombination rate. Moreover, the electrochemical properties of WO<sub>3</sub>·H<sub>2</sub>O nanostructures were also evaluated presenting a specific capacitance of 1209F g<sup>−1</sup>. This analysis highlights their potential in environmental remediation and supercapacitor applications.</div></div>","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"652 ","pages":"Article 128017"},"PeriodicalIF":1.7,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142745750","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 : 2024-11-24DOI: 10.1016/j.jcrysgro.2024.128016
Jingyi Yu , Hao Sun , Cong Zheng , Weiwei Jiang , Nan Wang , Zhiqiang Li , Sumei Wu , Hualong Tao , Tingting Yao , Hualin Wang , Shimin Liu , Chaoqian Liu , Wanyu Ding , Zhihua Zhang
Pure TiO2, Sn/Cl co-doped TiO2 and Sn/Cl co-doped TiO2-ZnO were fabricated and compared by a novel one-pot method to improve the photocatalytic performance of pure TiO2, which accomplishes the construction of heterojunctions simultaneously with doping by volatile solid solution. TG-DSC, XRD, FTIR, XPS, SEM, EDS, TEM, SAED, UV–Vis, PL and EIS were characterized to investigate the influence mechanism of Sn/Cl co-doping and ZnO content (0, 25, 50, 75, and 100 mol.%) on the thermal effect, crystal structure, morphology, composition, charge transfer behavior and photocatalytic performance of samples. Results indicate that ZnO appears and SnO2 disappears simultaneously with anatase TiO2 as the main phase by increasing ZnO content, and the morphology is changed from irregular sphere to sphere-sheet and sphere-plate correspondingly. The photocatalytic degradation efficiency first increases and then decreases, and achieves the maximum value of 73 % by SCT/Z50 which has sphere-sheet heterostructure containing more hydroxyl radicals, under 15 W weak-UV light irradiations for 3 h using methyl orange (MO) as pollutant. The excellent photocatalytic performance is attributed to the structural and morphological effects of Sn/Cl co-doping and ZnO introduction, which can increase the electron-hole separation efficiency. The optimized composition also has great potential in practical photocatalytic application due to the commercial advantage that ZnO is much cheaper than TiO2.
{"title":"One-pot synthesis and improved photocatalytic performance of Sn/Cl co-doped TiO2-ZnO nano-heterojunctions","authors":"Jingyi Yu , Hao Sun , Cong Zheng , Weiwei Jiang , Nan Wang , Zhiqiang Li , Sumei Wu , Hualong Tao , Tingting Yao , Hualin Wang , Shimin Liu , Chaoqian Liu , Wanyu Ding , Zhihua Zhang","doi":"10.1016/j.jcrysgro.2024.128016","DOIUrl":"10.1016/j.jcrysgro.2024.128016","url":null,"abstract":"<div><div>Pure TiO<sub>2</sub>, Sn/Cl co-doped TiO2 and Sn/Cl co-doped TiO<sub>2</sub>-ZnO were fabricated and compared by a novel one-pot method to improve the photocatalytic performance of pure TiO2, which accomplishes the construction of heterojunctions simultaneously with doping by volatile solid solution. TG-DSC, XRD, FTIR, XPS, SEM, EDS, TEM, SAED, UV–Vis, PL and EIS were characterized to investigate the influence mechanism of Sn/Cl co-doping and ZnO content (0, 25, 50, 75, and 100 mol.%) on the thermal effect, crystal structure, morphology, composition, charge transfer behavior and photocatalytic performance of samples. Results indicate that ZnO appears and SnO2 disappears simultaneously with anatase TiO2 as the main phase by increasing ZnO content, and the morphology is changed from irregular sphere to sphere-sheet and sphere-plate correspondingly. The photocatalytic degradation efficiency first increases and then decreases, and achieves the maximum value of 73 % by SCT/Z50 which has sphere-sheet heterostructure containing more hydroxyl radicals, under 15 W weak-UV light irradiations for 3 h using methyl orange (MO) as pollutant. The excellent photocatalytic performance is attributed to the structural and morphological effects of Sn/Cl co-doping and ZnO introduction, which can increase the electron-hole separation efficiency. The optimized composition also has great potential in practical photocatalytic application due to the commercial advantage that ZnO is much cheaper than TiO2.</div></div>","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"651 ","pages":"Article 128016"},"PeriodicalIF":1.7,"publicationDate":"2024-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142719613","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 : 2024-11-22DOI: 10.1016/j.jcrysgro.2024.128009
H.C. Sathisha , Anitha , G. Krishnamurthy , G. Nagaraju
In the field of nanoscience, using plant materials to create nanoparticles (NPs) is becoming growing in popularity and offers a number of benefits over physicochemical techniques. The green combustion approach effectively synthesized ZnO/ZrO2 nanocomposite (NCs) using powdered Butea monosperma (BM) leaf as the green fuel. The nature of NCs was confirmed through (X-ray Diffraction) XRD revealed that presence of hexagonal ZnO and cubic of ZrO2 phase. The morphology of NCs as seen by (Scanning Electron Microscopy) SEM and (Transmission Electron Microscopy) TEM reveals a fair distribution and non-uniform spherical shape. (Energy Dispersive X-Ray Analysis) EDAX pattern indicates the presence of zinc, zirconium and oxygen components. (Fourier Transform Infrared Spectroscopy) FT-IR spectrum obtained the metal–oxygen bonding in NCs. By applying the Tauc relation to calculate the optical energy band gap value of the sample is 3.34 eV. UV light is used to conduct the investigation of photocatalytic degradation of methylene blue (MB) dye. The NCs have superior degradation efficiency up to 99 % dye degradation is performed in 150 min. Furthermore, NCs exhibit a hazardous chromium (VI) decrease of up to 62 %. The collected results demonstrated that ZnO/ZrO2 NCs are the best photocatalyst for MB degradation and chromium reduction.
{"title":"Facile green synthesis of ZnO/ZrO2 nanocomposite for photocatalytic degradation and chromium (VI) reduction","authors":"H.C. Sathisha , Anitha , G. Krishnamurthy , G. Nagaraju","doi":"10.1016/j.jcrysgro.2024.128009","DOIUrl":"10.1016/j.jcrysgro.2024.128009","url":null,"abstract":"<div><div>In the field of nanoscience, using plant materials to create nanoparticles (NPs) is becoming growing in popularity and offers a number of benefits over physicochemical techniques. The green combustion approach effectively synthesized ZnO/ZrO<sub>2</sub> nanocomposite (NCs) using powdered Butea monosperma (BM) leaf as the green fuel. The nature of NCs was confirmed through (X-ray Diffraction) XRD revealed that presence of hexagonal ZnO and cubic of ZrO<sub>2</sub> phase. The morphology of NCs as seen by (Scanning Electron Microscopy) SEM and (Transmission Electron Microscopy) TEM reveals a fair distribution and non-uniform spherical shape. (Energy Dispersive X-Ray Analysis) EDAX pattern indicates the presence of zinc, zirconium and oxygen components. (Fourier Transform Infrared Spectroscopy) FT-IR spectrum obtained the metal–oxygen bonding in NCs. By applying the Tauc relation to calculate the optical energy band gap value of the sample is<!--> <!-->3.34 eV. UV light is used to conduct the<!--> <!-->investigation of<!--> <!-->photocatalytic<!--> <!-->degradation of methylene blue (MB) dye. The NCs have superior degradation efficiency up to 99 % dye degradation is performed in 150 min. Furthermore, NCs exhibit a hazardous chromium (VI) decrease of up to 62 %. The collected results demonstrated that ZnO/ZrO<sub>2</sub> NCs are the best photocatalyst for MB degradation and chromium reduction.</div></div>","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"651 ","pages":"Article 128009"},"PeriodicalIF":1.7,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142719614","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}
Langasite-type Ca3Ta(Ga,Al)3Si2O14 (CTGAS) piezoelectric bulk single crystals with a 2-inch diameter were continuously grown by the Czochralski (Cz) method using the residual melt after crystal growth and recharging. The first and second bulk single crystals without cracks were grown using a continuous crystal growth process. However, the third bulk single crystal included many cracks, suggesting that the cracks were generated because of the change in melt composition by the recharging process originating from the difference between the stoichiometric and congruent compositions. By evaluating the velocity distribution using ultrasonic waves, an area with low leaky surface acoustic wave (LSAW) velocity was observed at the center of the bulk single crystal.
{"title":"Continuous crystal growth and homogeneity of 2-inch Ca3Ta(Ga,Al)3Si2O14 bulk single crystals","authors":"Yuui Yokota , Yuji Ohashi , Yasuhiro Shoji , Akira Yoshikawa","doi":"10.1016/j.jcrysgro.2024.128013","DOIUrl":"10.1016/j.jcrysgro.2024.128013","url":null,"abstract":"<div><div>Langasite-type Ca<sub>3</sub>Ta(Ga,Al)<sub>3</sub>Si<sub>2</sub>O<sub>14</sub> (CTGAS) piezoelectric bulk single crystals with a 2-inch diameter were continuously grown by the Czochralski (Cz) method using the residual melt after crystal growth and recharging. The first and second bulk single crystals without cracks were grown using a continuous crystal growth process. However, the third bulk single crystal included many cracks, suggesting that the cracks were generated because of the change in melt composition by the recharging process originating from the difference between the stoichiometric and congruent compositions. By evaluating the velocity distribution using ultrasonic waves, an area with low leaky surface acoustic wave (LSAW) velocity was observed at the center of the bulk single crystal.</div></div>","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"652 ","pages":"Article 128013"},"PeriodicalIF":1.7,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142745751","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 : 2024-11-21DOI: 10.1016/j.jcrysgro.2024.128012
Gaoxiang Fan, Jiling Li, Yuhua Yang
Three kinds of ZnO microstructures are controlled synthesized on silicon substrates including microcolumns, microfences and hollow microcolumns. The morphological evolution of the prepared ZnO microstructures are systematically analyzed. It is found that the growth parameters play crucial roles on it, such as the growth temperature and the concentration of gaseous source atoms on the growth surface. Moreover, the optical characterizations suggest the structural advantages of ZnO microfence, that is, its excitation density has been enhanced due to its special symmetric hexagonal array, which has also switched on the p-band emission.
在硅衬底上控制合成了三种氧化锌微结构，包括微柱、微栅和空心微柱。系统分析了所制备的氧化锌微结构的形态演变。研究发现，生长温度和生长表面的气态源原子浓度等生长参数对其起着至关重要的作用。此外，光学特性分析表明了氧化锌微栅栏的结构优势，即其特殊的对称六边形阵列提高了激发密度，同时也开启了 p 波段发射。
{"title":"Morphological evolution and optical properties of ZnO microstructures","authors":"Gaoxiang Fan, Jiling Li, Yuhua Yang","doi":"10.1016/j.jcrysgro.2024.128012","DOIUrl":"10.1016/j.jcrysgro.2024.128012","url":null,"abstract":"<div><div>Three kinds of ZnO microstructures are controlled synthesized on silicon substrates including microcolumns, microfences and hollow microcolumns. The morphological evolution of the prepared ZnO microstructures are systematically analyzed. It is found that the growth parameters play crucial roles on it, such as the growth temperature and the concentration of gaseous source atoms on the growth surface. Moreover, the optical characterizations suggest the structural advantages of ZnO microfence, that is, its excitation density has been enhanced due to its special symmetric hexagonal array, which has also switched on the p-band emission.</div></div>","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"651 ","pages":"Article 128012"},"PeriodicalIF":1.7,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142719612","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 : 2024-11-20DOI: 10.1016/j.jcrysgro.2024.128011
Md. Parvej Mosaraf Sohel, Abdullah Al Moyeen, Ainul Islam Safi, Md. Sadrul Rahman Dipto, Shaadnan Bin Syed
Barium calcium strontium titanate (BCST) ceramics are promising materials for energy storage and dielectric applications, but their performance is often limited by high leakage currents and structural instability. To address these, Zr-doped BCST (Ba0.7Ca0.15Sr0.15ZrxTi(1-x)O3; x = 0.0, 0.1, 0.15, 0.2) ceramics were synthesized via the solid-state reaction method with the objective of reducing leakage currents in BCST ceramics. X-ray diffraction (XRD) analysis confirmed a single-phase-pseudocubic ABO3 structure with space group Pm-3mn all samples and a secondary ZrO2 phase in Zr-doped samples. Rietveld refinement revealed an increase in lattice parameters and unit cell volumes with higher doping, ranging from 62.483 to 63.363 Å3. The SEM images showed cubic and rod-shaped morphologies with agglomerates and pores, with grain sizes ranging between 0.543 μm and 0.727 μm. EDS analysis confirmed the presence of all constituent elements. Current density–voltage (J–V) analysis showed that the leakage current density increased non-linearly with voltage for all samples, with Zr doping significantly reducing leakage currents by enhancing chemical stability and suppressing electron jumps between Ti4+ and Ti3+. Among the samples, undoped BCST exhibited the highest leakage current, while Zr-doped samples showed improved resistivity and lower leakage currents. These properties make Zr-doped BCST ceramics promising candidates for energy storage devices and dielectric applications requiring high resistivity and low leakage currents.
{"title":"Study of the structural, morphological, and J–V characteristics of Zr-doped barium calcium strontium titanate","authors":"Md. Parvej Mosaraf Sohel, Abdullah Al Moyeen, Ainul Islam Safi, Md. Sadrul Rahman Dipto, Shaadnan Bin Syed","doi":"10.1016/j.jcrysgro.2024.128011","DOIUrl":"10.1016/j.jcrysgro.2024.128011","url":null,"abstract":"<div><div>Barium calcium strontium titanate (BCST) ceramics are promising materials for energy storage and dielectric applications, but their performance is often limited by high leakage currents and structural instability. To address these, Zr-doped BCST (Ba<sub>0.7</sub>Ca<sub>0.15</sub>Sr<sub>0.15</sub>Zr<sub>x</sub>Ti<sub>(1-x)</sub>O<sub>3</sub>; x = 0.0, 0.1, 0.15, 0.2) ceramics were synthesized via the solid-state reaction method with the objective of reducing leakage currents in BCST ceramics. X-ray diffraction (XRD) analysis confirmed a single-phase-pseudocubic ABO3 structure with space group <em>Pm-3m</em>n all samples and a secondary ZrO2 phase in Zr-doped samples. Rietveld refinement revealed an increase in lattice parameters and unit cell volumes with higher doping, ranging from 62.483 to 63.363 Å<sup>3</sup>. The SEM images showed cubic and rod-shaped morphologies with agglomerates and pores, with grain sizes ranging between 0.543 μm and 0.727 μm. EDS analysis confirmed the presence of all constituent elements. Current density–voltage (J–V) analysis showed that the leakage current density increased non-linearly with voltage for all samples, with Zr doping significantly reducing leakage currents by enhancing chemical stability and suppressing electron jumps between Ti<sup>4+</sup> and Ti<sup>3+</sup>. Among the samples, undoped BCST exhibited the highest leakage current, while Zr-doped samples showed improved resistivity and lower leakage currents. These properties make Zr-doped BCST ceramics promising candidates for energy storage devices and dielectric applications requiring high resistivity and low leakage currents.</div></div>","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"651 ","pages":"Article 128011"},"PeriodicalIF":1.7,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142719610","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 substrate misorientation angle direction and degree on the structural properties of N-polar GaN grown by a novel multi-step temperature epitaxial approach using hot-wall metal–organic chemical vapor deposition (MOCVD) on 4H-SiC (000) substrates is investigated. The surface morphology and X-ray diffraction (XRD) rocking curves (RCs) for both symmetric and asymmetric Bragg peaks of the multi-step temperature N-polar GaN are compared to a material obtained in a two-step temperature process. In the latter the temperature in the second step was varied so that it corresponds to the growth temperatures in each of the steps of the multi-step process. Different step-flow patterns are obtained on the substrates with a misorientation angle of 4° depending on whether its direction is towards the a-plane or the m-plane. In contrast, for a misorientation angle of 1° towards the m-plane, the surface morphology of N-polar GaN is dominated by hexagonal hillocks when using the 2-step temperature process and a step meandering growth mode is observed when employing the multi-step temperature process. These results are discussed and explained in terms of kinetic and thermodynamic considerations. As the growth temperature of the GaN layer in the 2-step temperature process increases from 950 °C to 1100 °C, the surface roughness and RCs widths decrease for the three types of substrates indicating improved crystal quality at higher temperature. The multi-step epitaxial approach is shown to be beneficial for achieving smooth surface morphology and low defect density of N-polar GaN layers grown on C-face SiC substrates with a misorientation angle of 4° and an RMS value of 1.5 nm over an area of 20 m 20 m is attained when the substrate mis-cut is towards the m-plane.
研究了在 4H-SiC (0001̄) 基底上使用热壁金属有机化学气相沉积 (MOCVD) 的新型多步温度外延方法生长的 N 极 GaN 的基底错向角方向和程度对其结构特性的影响。将多级温度 N 极 GaN 的对称和非对称布拉格峰的表面形貌和 X 射线衍射（XRD）摇摆曲线（RC）与通过两级温度工艺获得的材料进行了比较。在后者中，第二步的温度是变化的，以便与多步工艺中每一步的生长温度相对应。在错位角为 4° 的基底上，根据其方向是朝向 a 平面还是 m 平面，可以获得不同的阶梯流图案。与此相反，在朝向 m 平面的方向错位角为 1° 时，采用两步温度制程时，N 极 GaN 的表面形态以六角丘为主，而采用多步温度制程时，则出现了阶梯蜿蜒生长模式。我们从动力学和热力学的角度对这些结果进行了讨论和解释。随着两步温度工艺中 GaN 层的生长温度从 950 ℃ 升高到 1100 ℃，三种衬底的表面粗糙度和 RCs 宽度都有所下降，这表明在较高温度下晶体质量有所改善。多步外延方法有利于在 C 面碳化硅衬底上生长的 N 极 GaN 层获得平滑的表面形貌和较低的缺陷密度，当衬底错切朝向 m 平面时，在 20 μm × 20 μm 的区域内错位角为 4°，均方根值为 1.5 nm。
{"title":"Effect of substrate misorientation angle on the structural properties of N-polar GaN grown by hot-wall MOCVD on 4H-SiC(0001̄)","authors":"Hengfang Zhang , Jr.-Tai Chen , Alexis Papamichail , Ingemar Persson , Dat Q. Tran , Plamen P. Paskov , Vanya Darakchieva","doi":"10.1016/j.jcrysgro.2024.127971","DOIUrl":"10.1016/j.jcrysgro.2024.127971","url":null,"abstract":"<div><div>The effects of substrate misorientation angle direction and degree on the structural properties of N-polar GaN grown by a novel multi-step temperature epitaxial approach using hot-wall metal–organic chemical vapor deposition (MOCVD) on 4H-SiC (000<span><math><mover><mrow><mn>1</mn></mrow><mrow><mo>̄</mo></mrow></mover></math></span>) substrates is investigated. The surface morphology and X-ray diffraction (XRD) rocking curves (RCs) for both symmetric and asymmetric Bragg peaks of the multi-step temperature N-polar GaN are compared to a material obtained in a two-step temperature process. In the latter the temperature in the second step was varied so that it corresponds to the growth temperatures in each of the steps of the multi-step process. Different step-flow patterns are obtained on the substrates with a misorientation angle of 4° depending on whether its direction is towards the <em>a</em>-plane or the <em>m</em>-plane. In contrast, for a misorientation angle of 1° towards the <em>m</em>-plane, the surface morphology of N-polar GaN is dominated by hexagonal hillocks when using the 2-step temperature process and a step meandering growth mode is observed when employing the multi-step temperature process. These results are discussed and explained in terms of kinetic and thermodynamic considerations. As the growth temperature of the GaN layer in the 2-step temperature process increases from 950 °C to 1100 °C, the surface roughness and RCs widths decrease for the three types of substrates indicating improved crystal quality at higher temperature. The multi-step epitaxial approach is shown to be beneficial for achieving smooth surface morphology and low defect density of N-polar GaN layers grown on C-face SiC substrates with a misorientation angle of 4° and an RMS value of 1.5 nm over an area of 20 <span><math><mi>μ</mi></math></span>m <span><math><mo>×</mo></math></span> 20 <span><math><mi>μ</mi></math></span>m is attained when the substrate mis-cut is towards the <em>m</em>-plane.</div></div>","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"651 ","pages":"Article 127971"},"PeriodicalIF":1.7,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142719615","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 : 2024-11-19DOI: 10.1016/j.jcrysgro.2024.128008
Xiaobin Hao , Yicun Li , Xia Kong , Jilei Lyu , Kunlong Zhao , Jiwen Zhao , Sen Zhang , Dongyue Wen , Kang Liu , V.G. Ralchenko , Benjian Liu , Bing Dai , Jiaqi Zhu
Diamond, renowned for its exceptional properties, stands as the ultimate semiconductor material. Microwave plasma chemical vapor deposition (MPCVD) is pivotal in advancing diamond’s functional applications. The effectiveness of the MPCVD system hinges on the efficient transmission of microwave energy to the resonant cavity. Additionally, the system must form a large-area, high-intensity hemispherical standing-wave electric field in the deposition area. Thus, a well-conceived optimization design for the microwave transmission and resonance systems is imperative. This paper introduces a design methodology for MPCVD systems, aligning plasma requirements for diamond growth with the transmission and distribution characteristics of the microwave electromagnetic field, which means that system optimization can be achieved without the need for complex multiple physical fields simulations. The average electric field intensity up to 3.24 × 105 V/m is obtained by using the dual-objective optimization function as the comprehensive optimization objective of the metal boundaries of the reactor. Based on simulation findings, an MPCVD system operating at 2450 MHz was designed, resulting in a single-crystal diamond with a high average growth rate of 11.5 μm/h. Further reduction of the microwave frequency to 915 MHz enabled the preparation of a 4-inch polycrystalline diamond film, achieving an average growth rate close to 3.5 μm/h.
{"title":"Optimizing MPCVD systems for diamond growth through advanced microwave transmission theory","authors":"Xiaobin Hao , Yicun Li , Xia Kong , Jilei Lyu , Kunlong Zhao , Jiwen Zhao , Sen Zhang , Dongyue Wen , Kang Liu , V.G. Ralchenko , Benjian Liu , Bing Dai , Jiaqi Zhu","doi":"10.1016/j.jcrysgro.2024.128008","DOIUrl":"10.1016/j.jcrysgro.2024.128008","url":null,"abstract":"<div><div>Diamond, renowned for its exceptional properties, stands as the ultimate semiconductor material. Microwave plasma chemical vapor deposition (MPCVD) is pivotal in advancing diamond’s functional applications. The effectiveness of the MPCVD system hinges on the efficient transmission of microwave energy to the resonant cavity. Additionally, the system must form a large-area, high-intensity hemispherical standing-wave electric field in the deposition area. Thus, a well-conceived optimization design for the microwave transmission and resonance systems is imperative. This paper introduces a design methodology for MPCVD systems, aligning plasma requirements for diamond growth with the transmission and distribution characteristics of the microwave electromagnetic field, which means that system optimization can be achieved without the need for complex multiple physical fields simulations. The average electric field intensity up to 3.24 × 10<sup>5</sup> V/m is obtained by using the dual-objective optimization function as the comprehensive optimization objective of the metal boundaries of the reactor. Based on simulation findings, an MPCVD system operating at 2450 MHz was designed, resulting in a single-crystal diamond with a high average growth rate of 11.5 μm/h. Further reduction of the microwave frequency to 915 MHz enabled the preparation of a 4-inch polycrystalline diamond film, achieving an average growth rate close to 3.5 μm/h.</div></div>","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"651 ","pages":"Article 128008"},"PeriodicalIF":1.7,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142719611","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 : 2024-11-16DOI: 10.1016/j.jcrysgro.2024.128007
Shun Ukita, Takeyoshi Tajiri, Kazuo Uchida
In this study, n-type Ga2O3 thin films were grown on c-plane sapphire substrates by atmospheric pressure metalorganic vapor phase epitaxy using tetraethoxysilane (TEOS) as the silicon (Si) precursor. X-ray diffraction measurements confirmed that the deposited films were polycrystalline, predominantly consisting of the stable β-phase and the metastable κ-phase. Surface and optical characterizations indicated that lower growth temperature and appropriate Si doping reduce the grain size of three-dimensional Ga2O3 islands, thereby enhancing optical transmittance by mitigating surface scattering. Hall effect measurements demonstrated a maximum electron carrier concentration of approximately 1 × 1017 /cm3 at room temperature, while secondary ion mass spectrometry (SIMS) revealed that Si atomic concentrations were exceeding 1 × 1020 /cm3 in all n-type samples indicating low doping efficiency of Si. Carbon (C) impurities were also measured by SIMS with concentrations as the same order or higher than that of Si, implying they may be one of the reasons for the degraded electrical conductivity and originated from incomplete decomposition of the precursors during low temperature growth. From these results, it is crucial to reduce C impurities and enhance surface flatness to improve electrical and optical properties.
本研究使用四乙氧基硅烷（TEOS）作为硅（Si）前驱体，通过常压金属有机气相外延法在 c 平面蓝宝石衬底上生长了 n 型 Ga2O3 薄膜。X 射线衍射测量证实，沉积的薄膜是多晶体，主要由稳定的 β 相和易变的 κ 相组成。表面和光学特性分析表明，较低的生长温度和适当的硅掺杂可减小三维 Ga2O3 岛的晶粒尺寸，从而通过减少表面散射提高透光率。霍尔效应测量表明，室温下的最大电子载流子浓度约为 1 × 1017 /cm3，而二次离子质谱（SIMS）显示，所有 n 型样品中的硅原子浓度均超过 1 × 1020 /cm3，表明硅的掺杂效率较低。SIMS 还测出碳（C）杂质的浓度与硅的浓度相同或更高，这意味着碳（C）杂质可能是导电性降低的原因之一，源于低温生长过程中前驱体的不完全分解。从这些结果来看，减少 C 杂质和提高表面平整度对于改善电气和光学性能至关重要。
{"title":"Growth and characterization of n-type Ga2O3 films on sapphire substrates by APMOVPE","authors":"Shun Ukita, Takeyoshi Tajiri, Kazuo Uchida","doi":"10.1016/j.jcrysgro.2024.128007","DOIUrl":"10.1016/j.jcrysgro.2024.128007","url":null,"abstract":"<div><div>In this study, n-type Ga<sub>2</sub>O<sub>3</sub> thin films were grown on c-plane sapphire substrates by atmospheric pressure metalorganic vapor phase epitaxy using tetraethoxysilane (TEOS) as the silicon (Si) precursor. X-ray diffraction measurements confirmed that the deposited films were polycrystalline, predominantly consisting of the stable β-phase and the metastable κ-phase. Surface and optical characterizations indicated that lower growth temperature and appropriate Si doping reduce the grain size of three-dimensional Ga<sub>2</sub>O<sub>3</sub> islands, thereby enhancing optical transmittance by mitigating surface scattering. Hall effect measurements demonstrated a maximum electron carrier concentration of approximately 1 × 10<sup>17</sup> /cm<sup>3</sup> at room temperature, while secondary ion mass spectrometry (SIMS) revealed that Si atomic concentrations were exceeding 1 × 10<sup>20</sup> /cm<sup>3</sup> in all n-type samples indicating low doping efficiency of Si. Carbon (C) impurities were also measured by SIMS with concentrations as the same order or higher than that of Si, implying they may be one of the reasons for the degraded electrical conductivity and originated from incomplete decomposition of the precursors during low temperature growth. From these results, it is crucial to reduce C impurities and enhance surface flatness to improve electrical and optical properties.</div></div>","PeriodicalId":353,"journal":{"name":"Journal of Crystal Growth","volume":"650 ","pages":"Article 128007"},"PeriodicalIF":1.7,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142703247","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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