High-k gate dielectrics have attracted a great deal of attention in the investigation of transistors due to their unique properties such as superior gate controllability. However, their integration into graphene field-effect transistors (GFETs) remains problematic and the physical mechanisms governing the performance of these devices are still not fully understood. In this study, the effects of post-annealing on GFETs utilizing the high-k HfLaO ternary oxide as the gate dielectric were comprehensively investigated. The HfLaO film was deposited on top of graphene by magnetron sputtering, and the device performance with various post-annealing temperatures was conducted. It was found that post-annealing temperature can effectively increase the dielectric constant through balancing the oxygen-vacancy defects and moisture absorption. Both the surface morphology of HfLaO and performance of GFETs were investigated, and the fabricated GFETs exhibit notable electrical performance enhancements. Specifically, GFETs with a 200 °C post-annealed HfLaO gate dielectric demonstrate the optimal device performance, featuring a minimal Dirac point voltage (VDirac) of 1.1 V and a minimal hysteresis (ΔVDirac) of 0.5 V. The extracted hole and electron mobilities are 4012 and 1366 cm2/V · s, respectively, nearly one order of magnitude higher than that of GFETs with as-deposited HfLaO. This work outperforms other existing GFETs utilizing high-k gate dielectric and chemical vapor deposition grown graphene in terms of both carrier mobility and on–off ratio. It is also noted that the excessive post-annealing temperature can negatively impact the GFET performance through introducing oxygen vacancies, increasing the surface roughness, lowering the breakdown voltage, and inducing recrystallization.
{"title":"Enhanced electrical performance in graphene field-effect transistors through post-annealing of high-k HfLaO gate dielectrics","authors":"Chunlin Liu, Xuesong Li, Ling-Xuan Qian, Jing Tian, Xiping Zhang","doi":"10.1063/5.0207559","DOIUrl":"https://doi.org/10.1063/5.0207559","url":null,"abstract":"High-k gate dielectrics have attracted a great deal of attention in the investigation of transistors due to their unique properties such as superior gate controllability. However, their integration into graphene field-effect transistors (GFETs) remains problematic and the physical mechanisms governing the performance of these devices are still not fully understood. In this study, the effects of post-annealing on GFETs utilizing the high-k HfLaO ternary oxide as the gate dielectric were comprehensively investigated. The HfLaO film was deposited on top of graphene by magnetron sputtering, and the device performance with various post-annealing temperatures was conducted. It was found that post-annealing temperature can effectively increase the dielectric constant through balancing the oxygen-vacancy defects and moisture absorption. Both the surface morphology of HfLaO and performance of GFETs were investigated, and the fabricated GFETs exhibit notable electrical performance enhancements. Specifically, GFETs with a 200 °C post-annealed HfLaO gate dielectric demonstrate the optimal device performance, featuring a minimal Dirac point voltage (VDirac) of 1.1 V and a minimal hysteresis (ΔVDirac) of 0.5 V. The extracted hole and electron mobilities are 4012 and 1366 cm2/V · s, respectively, nearly one order of magnitude higher than that of GFETs with as-deposited HfLaO. This work outperforms other existing GFETs utilizing high-k gate dielectric and chemical vapor deposition grown graphene in terms of both carrier mobility and on–off ratio. It is also noted that the excessive post-annealing temperature can negatively impact the GFET performance through introducing oxygen vacancies, increasing the surface roughness, lowering the breakdown voltage, and inducing recrystallization.","PeriodicalId":7985,"journal":{"name":"APL Materials","volume":"171 1","pages":""},"PeriodicalIF":6.1,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142197834","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rubén Corcuera, Pilar Jiménez-Cavero, Rafael Pérez del Real, Francisco Rivadulla, Rafael Ramos, José Ignacio Morales-Aragonés, Soraya Sangiao, César Magén, Luis Morellón, Irene Lucas
The use of magnetic garnets in new technologies such as spintronic devices requires fine-structured thin films. Classical fabrication techniques for these materials, typically physical vapor deposition methods, lead to excellent magnetic behavior. However, availability and scalability for potential applications are well restricted. In this study, we propose an innovative approach to fabricating Yttrium Iron Garnet thin films with precise thickness control achieved through iterative layer deposition via a chemical synthesis route. Remarkably, the iterative deposition process results in films exhibiting exceptional crystallinity. Magnetic characterization provides saturation magnetization and coercivity values on par with those reported in literature, summed to narrow ferromagnetic resonance lines. Therefore, in this work we demonstrate the viability of polymer assisted deposition as a promising alternative thinking about scalability to conventional deposition techniques for this material. Notably, our findings reveal energy conversion efficiencies comparable to those achieved with materials synthesized via physical vapor deposition methods.
{"title":"Polymer assisted deposition of YIG thin films with thickness control for spintronics applications","authors":"Rubén Corcuera, Pilar Jiménez-Cavero, Rafael Pérez del Real, Francisco Rivadulla, Rafael Ramos, José Ignacio Morales-Aragonés, Soraya Sangiao, César Magén, Luis Morellón, Irene Lucas","doi":"10.1063/5.0223260","DOIUrl":"https://doi.org/10.1063/5.0223260","url":null,"abstract":"The use of magnetic garnets in new technologies such as spintronic devices requires fine-structured thin films. Classical fabrication techniques for these materials, typically physical vapor deposition methods, lead to excellent magnetic behavior. However, availability and scalability for potential applications are well restricted. In this study, we propose an innovative approach to fabricating Yttrium Iron Garnet thin films with precise thickness control achieved through iterative layer deposition via a chemical synthesis route. Remarkably, the iterative deposition process results in films exhibiting exceptional crystallinity. Magnetic characterization provides saturation magnetization and coercivity values on par with those reported in literature, summed to narrow ferromagnetic resonance lines. Therefore, in this work we demonstrate the viability of polymer assisted deposition as a promising alternative thinking about scalability to conventional deposition techniques for this material. Notably, our findings reveal energy conversion efficiencies comparable to those achieved with materials synthesized via physical vapor deposition methods.","PeriodicalId":7985,"journal":{"name":"APL Materials","volume":"210 1","pages":""},"PeriodicalIF":6.1,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142197835","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Myoung-Woo Yoo, Virginia O. Lorenz, Axel Hoffmann, David G. Cahill
In information technology devices, current-driven state switching is crucial in various disciplines including spintronics, where the contribution of heating to the switching mechanism plays an inevitable role. Recently, current-driven antiferromagnetic order switching has attracted considerable attention due to its implications for next-generation spintronic devices. Although the switching mechanisms can be explained by spin dynamics induced by spin torques, some reports have claimed that demagnetization above the Néel temperature due to Joule heating is critical for switching. Here, we present a systematic method and an analytical model to quantify the thermal contribution due to Joule heating in micro-electronic devices, focusing on current-driven octupole switching in the non-collinear antiferromagnet, Mn3Sn. The results consistently show that the critical temperature for switching remains relatively constant above the Néel temperature, while the threshold current density depends on the choice of substrate and the base temperature. In addition, we provide an analytical model to calculate the Joule-heating temperature, which quantitatively explains our experimental results. From numerical calculations, we illustrate the reconfiguration of magnetic order during cooling from a demagnetized state of polycrystalline Mn3Sn. This work provides not only deeper insights into magnetization switching in antiferromagnets, but also a general guideline for evaluating the Joule-heating temperature excursions in micro-electronic devices.
{"title":"Thermal contribution to current-driven antiferromagnetic-order switching","authors":"Myoung-Woo Yoo, Virginia O. Lorenz, Axel Hoffmann, David G. Cahill","doi":"10.1063/5.0219729","DOIUrl":"https://doi.org/10.1063/5.0219729","url":null,"abstract":"In information technology devices, current-driven state switching is crucial in various disciplines including spintronics, where the contribution of heating to the switching mechanism plays an inevitable role. Recently, current-driven antiferromagnetic order switching has attracted considerable attention due to its implications for next-generation spintronic devices. Although the switching mechanisms can be explained by spin dynamics induced by spin torques, some reports have claimed that demagnetization above the Néel temperature due to Joule heating is critical for switching. Here, we present a systematic method and an analytical model to quantify the thermal contribution due to Joule heating in micro-electronic devices, focusing on current-driven octupole switching in the non-collinear antiferromagnet, Mn3Sn. The results consistently show that the critical temperature for switching remains relatively constant above the Néel temperature, while the threshold current density depends on the choice of substrate and the base temperature. In addition, we provide an analytical model to calculate the Joule-heating temperature, which quantitatively explains our experimental results. From numerical calculations, we illustrate the reconfiguration of magnetic order during cooling from a demagnetized state of polycrystalline Mn3Sn. This work provides not only deeper insights into magnetization switching in antiferromagnets, but also a general guideline for evaluating the Joule-heating temperature excursions in micro-electronic devices.","PeriodicalId":7985,"journal":{"name":"APL Materials","volume":"97 1","pages":""},"PeriodicalIF":6.1,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142197829","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Azat Abdullaev, Kairolla Sekerbayev, Alexander Azarov, Vishnukanthan Venkatachalapathy, Vinay S. Chauhan, Zhandos Utegulov, Andrej Kuznetsov
Recently discovered double gamma/beta (γ/β) polymorph Ga2O3 structures constitute a class of novel materials providing an option to modulate functional properties across interfaces without changing the chemical compositions of materials, in contrast to that in conventional heterostructures. In this work, for the first time, we investigate thermal transport in such homo-interface structures as an example of their physical properties. In particular, the cross-plane thermal conductivity (k) was measured by femtosecond laser-based time-domain thermoreflectance with MHz modulation rates, effectively obtaining depth profiles of the thermal conductivity across the γ-/β-Ga2O3 structures. In this way, the thermal conductivity of γ-Ga2O3 ranging from 1.84 to 2.11 W m−1 K−1 was found to be independent of the initial β-substrates orientations, in accordance with the cubic spinel structure of the γ-phase and consistently with the molecular dynamics simulation data. In turn, the thermal conductivity of monoclinic β-Ga2O3 showed a distinct anisotropy, with values ranging from 10 W m−1 K−1 for [−201] to 20 Wm−1 K−1 for [010] orientations. Thus, for double γ-/β-Ga2O3 polymorph structures formed on [010] β-substrates, there is an order of magnitude difference in thermal conductivity across the γ/β interface, which can potentially be exploited in thermal energy conversion applications.
最近发现的双γ/β（γ/β）多晶Ga2O3结构是一类新型材料，与传统的异质结构相比，它提供了一种在不改变材料化学成分的情况下调节跨界面功能特性的选择。在这项研究中，我们首次研究了这类同界面结构中的热传输，作为其物理性质的一个实例。特别是，我们采用基于飞秒激光的时域热反射法测量了跨面热导率（k），其调制速率为 MHz，从而有效地获得了整个 γ-/β-Ga2O3 结构的热导率深度剖面图。这样，γ-Ga2O3 的热导率从 1.84 W m-1 K-1 到 2.11 W m-1 K-1 不等，这与γ-相的立方尖晶石结构相符，也与分子动力学模拟数据一致。反过来，单斜β-Ga2O3 的热导率表现出明显的各向异性，其值从 [-201] 取向的 10 W m-1 K-1 到 [010] 取向的 20 Wm-1 K-1。因此，对于在[010] β基底上形成的双γ-/β-Ga2O3多晶体结构，在γ/β界面上的热导率存在数量级的差异，这有可能在热能转换应用中得到利用。
{"title":"Thermal conductivity of double polymorph Ga2O3 structures","authors":"Azat Abdullaev, Kairolla Sekerbayev, Alexander Azarov, Vishnukanthan Venkatachalapathy, Vinay S. Chauhan, Zhandos Utegulov, Andrej Kuznetsov","doi":"10.1063/5.0213985","DOIUrl":"https://doi.org/10.1063/5.0213985","url":null,"abstract":"Recently discovered double gamma/beta (γ/β) polymorph Ga2O3 structures constitute a class of novel materials providing an option to modulate functional properties across interfaces without changing the chemical compositions of materials, in contrast to that in conventional heterostructures. In this work, for the first time, we investigate thermal transport in such homo-interface structures as an example of their physical properties. In particular, the cross-plane thermal conductivity (k) was measured by femtosecond laser-based time-domain thermoreflectance with MHz modulation rates, effectively obtaining depth profiles of the thermal conductivity across the γ-/β-Ga2O3 structures. In this way, the thermal conductivity of γ-Ga2O3 ranging from 1.84 to 2.11 W m−1 K−1 was found to be independent of the initial β-substrates orientations, in accordance with the cubic spinel structure of the γ-phase and consistently with the molecular dynamics simulation data. In turn, the thermal conductivity of monoclinic β-Ga2O3 showed a distinct anisotropy, with values ranging from 10 W m−1 K−1 for [−201] to 20 Wm−1 K−1 for [010] orientations. Thus, for double γ-/β-Ga2O3 polymorph structures formed on [010] β-substrates, there is an order of magnitude difference in thermal conductivity across the γ/β interface, which can potentially be exploited in thermal energy conversion applications.","PeriodicalId":7985,"journal":{"name":"APL Materials","volume":"17 1","pages":""},"PeriodicalIF":6.1,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142197830","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pei Gen Li, Sheung Mei Ng, Xin Yuan, Fu Xiang Zhang, Hon Fai Wong, Zhi Qin Chu, Peng Cao, Chi Wah Leung
The intrinsic magnetization compensation behaviors of rare-earth iron garnets (REIGs) make the material promising for applications in ultrafast spin storage devices. REIG/heavy metal heterostructures such as TbIG/Pt often display two sign crossovers of anomalous Hall effect resistance with varying temperatures. One of these crossovers is attributed to the magnetization compensation of REIG, and the other to the competition between the magnetic proximity effect and the spin Hall effect. Here, we design trilayer REIG heterostructures based on two rare-earth species (Tb and Eu). We modulate the layer stacking of the TbIG/EuIG/TbIG sandwich with a fixed total thickness and explore the contributions of REIG bulk and REIG/Pt interfaces on these two crossover points. As TbIG gradually moves away from Pt, the compensation temperature shows some fluctuations. However, when TbIG is entirely out of contact with Pt, the second crossover point undergoes a change that shows REIG/Pt interface dependency. The results highlight the dominance of REIG bulk on the compensation behavior and the interface sensitivity of the second crossover point. This study provides a reference for designing controllable spintronics devices, such as magnon valve applications.
{"title":"Spin magnetotransport in rare-earth iron garnet (REIG)/Pt: Effects of modulated bulk and REIG/Pt interfaces","authors":"Pei Gen Li, Sheung Mei Ng, Xin Yuan, Fu Xiang Zhang, Hon Fai Wong, Zhi Qin Chu, Peng Cao, Chi Wah Leung","doi":"10.1063/5.0215071","DOIUrl":"https://doi.org/10.1063/5.0215071","url":null,"abstract":"The intrinsic magnetization compensation behaviors of rare-earth iron garnets (REIGs) make the material promising for applications in ultrafast spin storage devices. REIG/heavy metal heterostructures such as TbIG/Pt often display two sign crossovers of anomalous Hall effect resistance with varying temperatures. One of these crossovers is attributed to the magnetization compensation of REIG, and the other to the competition between the magnetic proximity effect and the spin Hall effect. Here, we design trilayer REIG heterostructures based on two rare-earth species (Tb and Eu). We modulate the layer stacking of the TbIG/EuIG/TbIG sandwich with a fixed total thickness and explore the contributions of REIG bulk and REIG/Pt interfaces on these two crossover points. As TbIG gradually moves away from Pt, the compensation temperature shows some fluctuations. However, when TbIG is entirely out of contact with Pt, the second crossover point undergoes a change that shows REIG/Pt interface dependency. The results highlight the dominance of REIG bulk on the compensation behavior and the interface sensitivity of the second crossover point. This study provides a reference for designing controllable spintronics devices, such as magnon valve applications.","PeriodicalId":7985,"journal":{"name":"APL Materials","volume":"27 1","pages":""},"PeriodicalIF":6.1,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142197832","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The photo rechargeable device (PRD) has been continuously drawing attention because it combines energy conversion and storage in one device. As for the photoelectrode of PRD, the construction of heterojunction is of crucial importance to enhance the photo performance. In this work, a two-electrode photo rechargeable capacitor based on the p–n heterojunction of ZnO/ZIF-67 is fabricated. ZIF-67 not only serves as the energy storage material but also forms the p–n heterojunction together with ZnO. A fast volatilization method was adopted for the in situ growth of ZIF-67 on ZnO nanorods to ensure sufficient mass loading and fewer interface defects. The results show a photovoltage of 0.36 V (0.2 V higher than single ZnO), a specific capacitance of 759.0 mF/g, and an overall energy conversion efficiency of 0.49%. The enhanced photovoltage is attributed to the p–n heterojunction. Moreover, a practical button cell was also fabricated, with 91% Coulombic efficiency remaining after 3000 cycles in the dark.
{"title":"A photo rechargeable capacitor based on the p–n heterojunction of ZnO/ZIF-67 showing enhanced photovoltage","authors":"Yanlong Lv, Xin Sun, Changhua Mi, Jianan Gu, Yanhong Wang, Meicheng Li","doi":"10.1063/5.0219883","DOIUrl":"https://doi.org/10.1063/5.0219883","url":null,"abstract":"The photo rechargeable device (PRD) has been continuously drawing attention because it combines energy conversion and storage in one device. As for the photoelectrode of PRD, the construction of heterojunction is of crucial importance to enhance the photo performance. In this work, a two-electrode photo rechargeable capacitor based on the p–n heterojunction of ZnO/ZIF-67 is fabricated. ZIF-67 not only serves as the energy storage material but also forms the p–n heterojunction together with ZnO. A fast volatilization method was adopted for the in situ growth of ZIF-67 on ZnO nanorods to ensure sufficient mass loading and fewer interface defects. The results show a photovoltage of 0.36 V (0.2 V higher than single ZnO), a specific capacitance of 759.0 mF/g, and an overall energy conversion efficiency of 0.49%. The enhanced photovoltage is attributed to the p–n heterojunction. Moreover, a practical button cell was also fabricated, with 91% Coulombic efficiency remaining after 3000 cycles in the dark.","PeriodicalId":7985,"journal":{"name":"APL Materials","volume":"116 1","pages":""},"PeriodicalIF":6.1,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142225269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shun-Li Shang, Shuang Lin, Michael C. Gao, Darrell G. Schlom, Zi-Kui Liu
Controlling the oxidation state of constituents by tuning the oxidizing environment and materials chemistry is vital to the successful synthesis of targeted binary or multicomponent oxides. We have conducted a comprehensive thermodynamic analysis of 137 binary oxides to calculate their Ellingham diagrams. It is found that the “reactive” elements that oxidize easily are the f-block elements (lanthanides and actinides), elements in groups II, III, and IV (alkaline earth, Sc, Y, Ti, Zr, and Hf), and Al and Li. In contrast, the “noble” elements are easily reduced. These are coinage metals (Cu, Ag, and especially Au), Pt-group elements, and Hg and Se. Machine learning-based sequential feature selection indicates that the ease of oxidation can be represented by the electronic structures of pure elements, for example, their d- and s-valence electrons, Mendeleev numbers, and groups, making the Periodic Table a useful tool for qualitatively assessing the ease of oxidation. The other elemental features that weakly correlate with the ease of oxidation are thermochemical properties such as melting points and the standard entropy at 298 K of pure elements. Applying Ellingham diagrams enables the oxidation of multicomponent materials to be predicted, such as the Fe–20Cr–20Ni alloy (in wt. %) and the equimolar high entropy alloy of AlCoCrFeNi. These Ellingham diagram-based predictions are in accordance with thermodynamic calculations using the CALPHAD approach and experimental observations in the literature.
通过调整氧化环境和材料化学来控制成分的氧化态，对于成功合成目标二元或多组分氧化物至关重要。我们对 137 种二元氧化物进行了全面的热力学分析，以计算它们的埃林厄姆图。结果发现，容易氧化的 "活性 "元素是 f 族元素（镧系元素和锕系元素）、第二、第三和第四族元素（碱土、Sc、Y、Ti、Zr 和 Hf）以及 Al 和 Li。相比之下，"惰性 "元素很容易被还原。它们是贵金属（铜、银，尤其是金）、铂族元素以及汞和硒。基于机器学习的序列特征选择表明，氧化的难易程度可以用纯元素的电子结构来表示，例如它们的 d 和 s 价电子、门捷列夫数和基团，这使得元素周期表成为定性评估氧化难易程度的有用工具。与氧化难易程度相关性较弱的其他元素特征是热化学性质，如纯元素的熔点和 298 K 时的标准熵。应用埃林厄姆图可以预测多组分材料的氧化情况，例如铁-20Cr-20Ni 合金（以重量百分比计）和 AlCoCrFeNi 等摩尔高熵合金。这些基于埃林厄姆图的预测与使用 CALPHAD 方法进行的热力学计算和文献中的实验观察结果一致。
{"title":"Ellingham diagrams of binary oxides","authors":"Shun-Li Shang, Shuang Lin, Michael C. Gao, Darrell G. Schlom, Zi-Kui Liu","doi":"10.1063/5.0216426","DOIUrl":"https://doi.org/10.1063/5.0216426","url":null,"abstract":"Controlling the oxidation state of constituents by tuning the oxidizing environment and materials chemistry is vital to the successful synthesis of targeted binary or multicomponent oxides. We have conducted a comprehensive thermodynamic analysis of 137 binary oxides to calculate their Ellingham diagrams. It is found that the “reactive” elements that oxidize easily are the f-block elements (lanthanides and actinides), elements in groups II, III, and IV (alkaline earth, Sc, Y, Ti, Zr, and Hf), and Al and Li. In contrast, the “noble” elements are easily reduced. These are coinage metals (Cu, Ag, and especially Au), Pt-group elements, and Hg and Se. Machine learning-based sequential feature selection indicates that the ease of oxidation can be represented by the electronic structures of pure elements, for example, their d- and s-valence electrons, Mendeleev numbers, and groups, making the Periodic Table a useful tool for qualitatively assessing the ease of oxidation. The other elemental features that weakly correlate with the ease of oxidation are thermochemical properties such as melting points and the standard entropy at 298 K of pure elements. Applying Ellingham diagrams enables the oxidation of multicomponent materials to be predicted, such as the Fe–20Cr–20Ni alloy (in wt. %) and the equimolar high entropy alloy of AlCoCrFeNi. These Ellingham diagram-based predictions are in accordance with thermodynamic calculations using the CALPHAD approach and experimental observations in the literature.","PeriodicalId":7985,"journal":{"name":"APL Materials","volume":"43 1","pages":""},"PeriodicalIF":6.1,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142197827","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xueqing Chen, Nan Li, Zerong Xing, Jiasheng Zu, Xianwei Meng, Zhuquan Zhou, Qian Li, Lifeng Tian, Yuntao Cui, Jing Liu
GaN, a third-generation semiconductor, has gained widespread attention owing to its high temperature resistance, wide bandgap, and high critical breakdown electric fields. Magnetron sputtering has a broad potential in the field of low-cost growth of GaN on account of high efficiency, superior quality, and convenient operation. However, challenges caused from the pure Ga targets with a huge refrigeration system need to be resolved for wide practices. Here, a new and cost-effective Ga target for magnetron sputtering was fabricated by utilizing the wetting properties of CuGa2 and Ga. Mixed microcrystalline and amorphous GaN films were obtained via reactive magnetron sputtering employing the Ga target. The average deposition rate is about 1.68 nm/min, and the average roughness is ∼7.45 ± 0.26 nm under 100 W of sputtering power. In addition, the sputtered GaN films were found to be wide-bandgap and p-type semiconductors with high transmittance, as revealed by x-ray photoelectron spectroscopy and absorption spectra. The GaN films display a bandgap of ∼3.60 eV and a transmittance exceeding 88.5% in the visible range. Furthermore, field-effect transistors and metal–semiconductor–metal photodetectors have been fabricated using the obtained GaN films, demonstrating favorable response characteristics. The prospects of microcrystalline/amorphous GaN films in sensing, power devices, and flexible electronics were forecasted. Overall, a low-cost and pervasive route of target fabrication process expands the possibilities of using low melting point metals in magnetron sputtering.
氮化镓是第三代半导体，因其耐高温、宽带隙和高临界击穿电场而受到广泛关注。磁控溅射具有效率高、质量好、操作方便等优点，在低成本生长氮化镓领域具有广阔的发展前景。然而，为了广泛应用，需要解决纯镓靶材与庞大的制冷系统所带来的挑战。在此，我们利用 CuGa2 和 Ga 的润湿特性，制造了一种新型且经济高效的磁控溅射 Ga 靶件。利用这种镓靶，通过反应磁控溅射获得了微晶和非晶氮化镓混合薄膜。在 100 W 溅射功率下，平均沉积速率约为 1.68 nm/min，平均粗糙度为 ∼7.45 ± 0.26 nm。此外，X 射线光电子能谱和吸收光谱显示，溅射出的氮化镓薄膜是具有高透过率的宽带隙 p 型半导体。氮化镓薄膜的带隙为∼3.60 eV，在可见光范围内的透过率超过 88.5%。此外，利用所获得的氮化镓薄膜制作的场效应晶体管和金属-半导体-金属光电探测器也显示出良好的响应特性。研究人员还预测了微晶/非晶氮化镓薄膜在传感、功率器件和柔性电子器件中的应用前景。总之，低成本和普遍的靶材制造工艺路线拓展了在磁控溅射中使用低熔点金属的可能性。
{"title":"A low-cost and convenient route of fabricating GaN films with P-type mixed microcrystalline and amorphous structure deposited via Ga target of magnetron sputtering","authors":"Xueqing Chen, Nan Li, Zerong Xing, Jiasheng Zu, Xianwei Meng, Zhuquan Zhou, Qian Li, Lifeng Tian, Yuntao Cui, Jing Liu","doi":"10.1063/5.0217625","DOIUrl":"https://doi.org/10.1063/5.0217625","url":null,"abstract":"GaN, a third-generation semiconductor, has gained widespread attention owing to its high temperature resistance, wide bandgap, and high critical breakdown electric fields. Magnetron sputtering has a broad potential in the field of low-cost growth of GaN on account of high efficiency, superior quality, and convenient operation. However, challenges caused from the pure Ga targets with a huge refrigeration system need to be resolved for wide practices. Here, a new and cost-effective Ga target for magnetron sputtering was fabricated by utilizing the wetting properties of CuGa2 and Ga. Mixed microcrystalline and amorphous GaN films were obtained via reactive magnetron sputtering employing the Ga target. The average deposition rate is about 1.68 nm/min, and the average roughness is ∼7.45 ± 0.26 nm under 100 W of sputtering power. In addition, the sputtered GaN films were found to be wide-bandgap and p-type semiconductors with high transmittance, as revealed by x-ray photoelectron spectroscopy and absorption spectra. The GaN films display a bandgap of ∼3.60 eV and a transmittance exceeding 88.5% in the visible range. Furthermore, field-effect transistors and metal–semiconductor–metal photodetectors have been fabricated using the obtained GaN films, demonstrating favorable response characteristics. The prospects of microcrystalline/amorphous GaN films in sensing, power devices, and flexible electronics were forecasted. Overall, a low-cost and pervasive route of target fabrication process expands the possibilities of using low melting point metals in magnetron sputtering.","PeriodicalId":7985,"journal":{"name":"APL Materials","volume":"43 1","pages":""},"PeriodicalIF":6.1,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142197833","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
MXenes, a novel class of two-dimensional (2D) materials, have attracted considerable attention in various fields, especially in drug delivery, wound healing, bone tissue engineering, biosensing, and cancer treatment. Thanks to their remarkable physicochemical properties, MXenes hold great promise for biomedical applications. Concurrently, hydrogels composed of polymers have been extensively utilized in biomedical contexts. The unique properties of MXenes facilitate their integration into various bioactive hydrogels with enhanced functions and properties, thereby endowing the composites with multifunctional capabilities. MXene-reinforced polymer hydrogels (MRPHs) synergistically combine the advantageous characteristics of both MXenes and hydrogels, making them highly adaptable for integration with other theranostic strategies in medical applications. In this comprehensive review, we demonstrate recent advances in the design and synthesis of MRPHs for biomedical applications. Specifically, we introduce the unique functions and properties of MRPHs and analyze the methods for tailoring the functions of MRPHs by incorporating them with other active components, including functional molecules, 2D materials, metal ions, natural polymers, and drugs/genes. We then discuss the biomedical applications of the designed bioactive MRPHs in wound healing, tissue engineering, biosensors, and cancer therapy. We hope that this work provides valuable guidance and inspiration for readers to develop novel MRPHs for advanced applications.
{"title":"MXene-reinforced bioactive polymer hydrogels for biomedical applications","authors":"Guanghui Gu, Xue Chen, Gang Wei, Mingjin Xu","doi":"10.1063/5.0226665","DOIUrl":"https://doi.org/10.1063/5.0226665","url":null,"abstract":"MXenes, a novel class of two-dimensional (2D) materials, have attracted considerable attention in various fields, especially in drug delivery, wound healing, bone tissue engineering, biosensing, and cancer treatment. Thanks to their remarkable physicochemical properties, MXenes hold great promise for biomedical applications. Concurrently, hydrogels composed of polymers have been extensively utilized in biomedical contexts. The unique properties of MXenes facilitate their integration into various bioactive hydrogels with enhanced functions and properties, thereby endowing the composites with multifunctional capabilities. MXene-reinforced polymer hydrogels (MRPHs) synergistically combine the advantageous characteristics of both MXenes and hydrogels, making them highly adaptable for integration with other theranostic strategies in medical applications. In this comprehensive review, we demonstrate recent advances in the design and synthesis of MRPHs for biomedical applications. Specifically, we introduce the unique functions and properties of MRPHs and analyze the methods for tailoring the functions of MRPHs by incorporating them with other active components, including functional molecules, 2D materials, metal ions, natural polymers, and drugs/genes. We then discuss the biomedical applications of the designed bioactive MRPHs in wound healing, tissue engineering, biosensors, and cancer therapy. We hope that this work provides valuable guidance and inspiration for readers to develop novel MRPHs for advanced applications.","PeriodicalId":7985,"journal":{"name":"APL Materials","volume":"41 1","pages":""},"PeriodicalIF":6.1,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141934529","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Cost-effective, versatile, and rapid deposition of single-crystal metal films is crucial to a wide spectrum of applications ranging from catalysis, plasmonics, electrochemistry, and optoelectronics to templating, epitaxial substrates, and integrated nanomanufacturing. High crystal quality typically implies low growth rates, which makes it challenging to achieve thicknesses in excess of 1 µm with conventional approaches. We show facile close-space sublimation of epitaxial single-crystal Au, Ag, and Cu films on MgO substrates. We demonstrate 10 μm thickness in less than 1 h while maintaining sub-5 nm rms surface roughness for a range of low- and high-index crystal film orientations. We show that the results can be captured by a simple model based on “line-of-sight” sublimation, which serves as a predictive tool and provides a basis to discuss broader potential as well as the limitations of this approach.
{"title":"Close-space sublimation of single-crystal metal films","authors":"Oliver J. Burton, Stephan Hofmann","doi":"10.1063/5.0216953","DOIUrl":"https://doi.org/10.1063/5.0216953","url":null,"abstract":"Cost-effective, versatile, and rapid deposition of single-crystal metal films is crucial to a wide spectrum of applications ranging from catalysis, plasmonics, electrochemistry, and optoelectronics to templating, epitaxial substrates, and integrated nanomanufacturing. High crystal quality typically implies low growth rates, which makes it challenging to achieve thicknesses in excess of 1 µm with conventional approaches. We show facile close-space sublimation of epitaxial single-crystal Au, Ag, and Cu films on MgO substrates. We demonstrate 10 μm thickness in less than 1 h while maintaining sub-5 nm rms surface roughness for a range of low- and high-index crystal film orientations. We show that the results can be captured by a simple model based on “line-of-sight” sublimation, which serves as a predictive tool and provides a basis to discuss broader potential as well as the limitations of this approach.","PeriodicalId":7985,"journal":{"name":"APL Materials","volume":"120 1","pages":""},"PeriodicalIF":6.1,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141968831","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：