Pierre Ducluzaux, Delia Ristoiu, Gilles Cunge, E. Despiau-Pujo
A two-dimensional hybrid model is used to simulate an industrial dual-frequency capacitively coupled plasma reactor working at closely spaced frequencies (13.56–40.68 MHz) in pure CF4 chemistry. The goal is to understand how plasma operating conditions (pressure, low-frequency and high-frequency RF powers, and chamber wall conditions) influence critical etching parameters such as the ion energy and angular distribution (IEAD) and the ion flux at the wafer. In base case conditions, the ionic and radical composition at the center of the plasma is analyzed, revealing CF3+ and F− as the primary ions, and F, CF, CF3, CF2, and F2 as the predominant radicals (by decreasing density). The impact of the surface recombination coefficient of F radicals into F2 at the reactor walls, γ(rec,F > F2), is then explored; it is found that increasing γ(rec,F > F2) has a strong impact on the final plasma composition, decreasing CF and F densities while increasing CF3, CF2, and F densities, which highlights the importance of properly considering wall conditions in CF-based plasmas simulation. The IEAD at the wafer is then characterized, showing that the total IEAD shape is affected by the plasma ion composition: heavy ions such as CF3+ (69 amu) form the core of the distribution while lighter species such as F+ (19 amu) form the wing of the distribution due to their lower mass. The low frequency (LF) power (100–900 W) is shown to substantially modify the ion energy distribution function (IEDF) owing to sheath voltage changes, but to also marginally increase the ion flux at the wafer. Conversely, the high-frequency (HF) power (100–1500 W) strongly impacts the ion flux at the wafer due to HF voltage fluctuations, while the IEDF remains mostly unaffected. This study also reveals some coupling between the effects of the LF (13.56 MHz) and HF (40.68 MHz) power, a phenomenon attributable to their proximity in frequency which should not be neglected. Finally, increasing the pressure from 30 to 200 mTorr is found to increase the electronegativity by a factor 4 and to strongly impact the plasma structure, primarily due to variations in ion mobility; it also widens the ion angular spread, potentially influencing etch uniformity. Notably, higher pressures exceeding 100 mTorr result in a decrease in the average ion density and the emergence of a low-energy peak in the ion energy distribution, attributed to charge exchange collisions.
{"title":"Impact of plasma operating conditions on the ion energy and angular distributions in dual-frequency capacitively coupled plasma reactors using CF4 chemistry","authors":"Pierre Ducluzaux, Delia Ristoiu, Gilles Cunge, E. Despiau-Pujo","doi":"10.1116/6.0003291","DOIUrl":"https://doi.org/10.1116/6.0003291","url":null,"abstract":"A two-dimensional hybrid model is used to simulate an industrial dual-frequency capacitively coupled plasma reactor working at closely spaced frequencies (13.56–40.68 MHz) in pure CF4 chemistry. The goal is to understand how plasma operating conditions (pressure, low-frequency and high-frequency RF powers, and chamber wall conditions) influence critical etching parameters such as the ion energy and angular distribution (IEAD) and the ion flux at the wafer. In base case conditions, the ionic and radical composition at the center of the plasma is analyzed, revealing CF3+ and F− as the primary ions, and F, CF, CF3, CF2, and F2 as the predominant radicals (by decreasing density). The impact of the surface recombination coefficient of F radicals into F2 at the reactor walls, γ(rec,F > F2), is then explored; it is found that increasing γ(rec,F > F2) has a strong impact on the final plasma composition, decreasing CF and F densities while increasing CF3, CF2, and F densities, which highlights the importance of properly considering wall conditions in CF-based plasmas simulation. The IEAD at the wafer is then characterized, showing that the total IEAD shape is affected by the plasma ion composition: heavy ions such as CF3+ (69 amu) form the core of the distribution while lighter species such as F+ (19 amu) form the wing of the distribution due to their lower mass. The low frequency (LF) power (100–900 W) is shown to substantially modify the ion energy distribution function (IEDF) owing to sheath voltage changes, but to also marginally increase the ion flux at the wafer. Conversely, the high-frequency (HF) power (100–1500 W) strongly impacts the ion flux at the wafer due to HF voltage fluctuations, while the IEDF remains mostly unaffected. This study also reveals some coupling between the effects of the LF (13.56 MHz) and HF (40.68 MHz) power, a phenomenon attributable to their proximity in frequency which should not be neglected. Finally, increasing the pressure from 30 to 200 mTorr is found to increase the electronegativity by a factor 4 and to strongly impact the plasma structure, primarily due to variations in ion mobility; it also widens the ion angular spread, potentially influencing etch uniformity. Notably, higher pressures exceeding 100 mTorr result in a decrease in the average ion density and the emergence of a low-energy peak in the ion energy distribution, attributed to charge exchange collisions.","PeriodicalId":509398,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139395023","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Adnan Mohammad, K. D. Joshi, Dhan Rana, S. Ilhom, Barrett Wells, Boris Sinkovic, A. Okyay, N. Biyikli
Due to its different polymorphs, including vanadium pentoxide (V2O5) and vanadium dioxide (VO2), the vanadium oxide (VOX) compound is an immensely interesting material with many important applications. While atomic layer deposition (ALD) is among the possible VOX film synthesis methods, literature reports have majorly utilized thermal-ALD, which reveals as-grown amorphous VOX films. Further post-deposition annealing process is needed to crystallize these films. High-temperature crystallization indeed limits the use of low-temperature compatible materials, processes, and substrates. In this work, we report on the low-temperature crystalline VOX film growth in a hollow-cathode plasma-enhanced atomic layer deposition reactor using two different vanadium precursors, tetrakis(ethylmethylamino)vanadium and vanadium(V) oxytriisopropoxide. Oxygen plasmas were used as co-reactants at a substrate temperature of 150 °C. Along with the purpose of investing in the impact of metal precursors on VOX film growth, we also studied Ar-plasma in situ and thermal ex situ annealing to investigate possible structural enhancement and phase transformation. In situ Ar-plasma annealing was performed with 20 s, 20 SCCM Ar-plasma, while post-deposition ex situ annealing was carried out at 500 °C and 0.5 mTorr O2 pressure. In situ ellipsometry was performed to record instant film thickness variation and several ex situ characterizations were performed to extract the optical, structural, and electrical properties of the films. The outcomes of the study confirm that both metal precursors result in as-grown crystalline V2O5 films at 150 °C. On the other hand, post-deposition annealing converted the as-grown crystalline V2O5 film to VO2 film. Finally, we have also successfully confirmed the metal-to-insulator transition property of the annealed VO2 films via temperature-dependent structural and electrical measurements.
{"title":"Hollow-cathode plasma deposited vanadium oxide films: Metal precursor influence on growth and material properties","authors":"Adnan Mohammad, K. D. Joshi, Dhan Rana, S. Ilhom, Barrett Wells, Boris Sinkovic, A. Okyay, N. Biyikli","doi":"10.1116/6.0002988","DOIUrl":"https://doi.org/10.1116/6.0002988","url":null,"abstract":"Due to its different polymorphs, including vanadium pentoxide (V2O5) and vanadium dioxide (VO2), the vanadium oxide (VOX) compound is an immensely interesting material with many important applications. While atomic layer deposition (ALD) is among the possible VOX film synthesis methods, literature reports have majorly utilized thermal-ALD, which reveals as-grown amorphous VOX films. Further post-deposition annealing process is needed to crystallize these films. High-temperature crystallization indeed limits the use of low-temperature compatible materials, processes, and substrates. In this work, we report on the low-temperature crystalline VOX film growth in a hollow-cathode plasma-enhanced atomic layer deposition reactor using two different vanadium precursors, tetrakis(ethylmethylamino)vanadium and vanadium(V) oxytriisopropoxide. Oxygen plasmas were used as co-reactants at a substrate temperature of 150 °C. Along with the purpose of investing in the impact of metal precursors on VOX film growth, we also studied Ar-plasma in situ and thermal ex situ annealing to investigate possible structural enhancement and phase transformation. In situ Ar-plasma annealing was performed with 20 s, 20 SCCM Ar-plasma, while post-deposition ex situ annealing was carried out at 500 °C and 0.5 mTorr O2 pressure. In situ ellipsometry was performed to record instant film thickness variation and several ex situ characterizations were performed to extract the optical, structural, and electrical properties of the films. The outcomes of the study confirm that both metal precursors result in as-grown crystalline V2O5 films at 150 °C. On the other hand, post-deposition annealing converted the as-grown crystalline V2O5 film to VO2 film. Finally, we have also successfully confirmed the metal-to-insulator transition property of the annealed VO2 films via temperature-dependent structural and electrical measurements.","PeriodicalId":509398,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139395668","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study demonstrates the formation of ZnWO4/WO3 composite that are engendered by cosputtering deposition followed by calcination. The concentrations of the tungsten dopant are found to have a profound effect on crystal formation, composition, and photoluminescence. The quantum efficiency measurements investigating different excitation light directions indicate that WO3 can form an underlayer of ZnWO4 at high dopant concentrations. The formation of bilayerlike films is caused by segregation, resulting from time evolution of sputtering yield due to temperature changes at the surface of the sputtering target.
{"title":"Formation of ZnWO4/WO3 composite film by RF magnetron sputtering and calcination","authors":"Sho Kakuta, Takeru Okada","doi":"10.1116/6.0003180","DOIUrl":"https://doi.org/10.1116/6.0003180","url":null,"abstract":"This study demonstrates the formation of ZnWO4/WO3 composite that are engendered by cosputtering deposition followed by calcination. The concentrations of the tungsten dopant are found to have a profound effect on crystal formation, composition, and photoluminescence. The quantum efficiency measurements investigating different excitation light directions indicate that WO3 can form an underlayer of ZnWO4 at high dopant concentrations. The formation of bilayerlike films is caused by segregation, resulting from time evolution of sputtering yield due to temperature changes at the surface of the sputtering target.","PeriodicalId":509398,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139392219","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Anuj Singhal, R. Divan, Anandvinod Dalmiya, Liliana Stan, Arian Ghiacy, Patrick T. Lynch, Igor Paprotny
Photonic crystals (PhCs) are spatially organized structures with lattice parameters equivalent to the operational wavelength of light. PhCs have been subject to extensive research efforts in the last two decades and are known for controlling light propagation with applications in sensing and time-delayed communication due to the slow-light phenomenon. Despite their exceptional properties, PhCs are difficult to fabricate using planar micromachining techniques due to their periodic structures. Techniques like two-photon stereolithography have been discussed for PhC fabrication in the literature, but the inherent disadvantage of poor refractive index (RI) contrast results in limited application. In this work, we present sequential infiltration synthesis performed on two-photon stereolithographically printed 3D PhCs for infiltration with zinc oxide to increase the RI of 3D PhCs. Finite element analysis was performed over a range of RI contrast values to study the change in photonic bandgap (PBG) with RI contrast. The transmission spectra were recorded on 3D PhCs before and after infiltration to demonstrate the change experimentally. An increase in the PBG width and absorbance is seen postinfiltration due to enhanced RI. This work presents the first, to our knowledge, sequentially infiltrated enhanced 3D PhC fabricated with two-photon stereolithography.
光子晶体（PhCs）是一种空间组织结构，其晶格参数相当于光的工作波长。过去二十年来，人们对光子晶体进行了广泛的研究，由于慢光现象，光子晶体可控制光的传播，并可应用于传感和延时通信。尽管 PhC 具有卓越的性能，但由于其周期性结构，很难使用平面微加工技术制造。文献中已经讨论了用于制造 PhC 的双光子立体光刻等技术，但其固有的缺点是折射率（RI）对比度差，因此应用有限。在这项工作中，我们介绍了在双光子立体光刻打印的三维 PhC 上进行顺序浸润合成，以浸润氧化锌，从而提高三维 PhC 的 RI。在 RI 对比度值范围内进行了有限元分析，以研究光子带隙（PBG）随 RI 对比度的变化。在三维 PhC 上记录了渗入前后的透射光谱，以实验证明这种变化。由于 RI 增强，渗透后的 PBG 宽度和吸光度都有所增加。据我们所知，这项工作首次展示了利用双光子立体光刻技术制造的顺序浸润增强型三维 PhC。
{"title":"Sequential infiltration of two-photon polymerized 3D photonic crystals for mid-IR spectroscopic applications","authors":"Anuj Singhal, R. Divan, Anandvinod Dalmiya, Liliana Stan, Arian Ghiacy, Patrick T. Lynch, Igor Paprotny","doi":"10.1116/6.0003271","DOIUrl":"https://doi.org/10.1116/6.0003271","url":null,"abstract":"Photonic crystals (PhCs) are spatially organized structures with lattice parameters equivalent to the operational wavelength of light. PhCs have been subject to extensive research efforts in the last two decades and are known for controlling light propagation with applications in sensing and time-delayed communication due to the slow-light phenomenon. Despite their exceptional properties, PhCs are difficult to fabricate using planar micromachining techniques due to their periodic structures. Techniques like two-photon stereolithography have been discussed for PhC fabrication in the literature, but the inherent disadvantage of poor refractive index (RI) contrast results in limited application. In this work, we present sequential infiltration synthesis performed on two-photon stereolithographically printed 3D PhCs for infiltration with zinc oxide to increase the RI of 3D PhCs. Finite element analysis was performed over a range of RI contrast values to study the change in photonic bandgap (PBG) with RI contrast. The transmission spectra were recorded on 3D PhCs before and after infiltration to demonstrate the change experimentally. An increase in the PBG width and absorbance is seen postinfiltration due to enhanced RI. This work presents the first, to our knowledge, sequentially infiltrated enhanced 3D PhC fabricated with two-photon stereolithography.","PeriodicalId":509398,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139391852","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Dain Shin, Inkyu Sohn, Donghyun Kim, Jaehyeok Kim, Taewook Nam, Youngjun Kim, Jusang Park, Tatsuya Nakazawa, Seung-min Chung, Hyungjun Kim
2D transition metal dichalcogenides (2D TMDCs) have thin and flexible structures and can be widely applied to nanoelectronics technology as a representative of 2D materials. Research studies on the surface functionalization of 2D TMDCs with nanoparticles have been actively conducted for fabrication of high-performance devices. Specifically, platinum (Pt) has attracted significant attention as a surface functionalization material in various applications, including photosensors, biosensors, and gas sensors due to its effective catalytic effect and excellent corrosion resistance. However, solution-based methods and PVD technologies, widely used for Pt nanoparticle synthesis, have difficulties forming fine particles dispersed on nanomaterials. Atomic layer deposition (ALD) is emerging as an advantageous method for forming nanoparticles, and dimethyl (N,N-dimethyl-3-buten-1-amine-N) platinum (DDAP) can overcome disadvantages of conventional ALD Pt precursors. In this study, we successfully synthesized Pt films using hydrogen as a new reactant in the DDAP-based ALD Pt process and evaluated formation of nanoparticles on SiO2/Si substrates. Subsequently, the ALD Pt-functionalized photodetector was fabricated with 2D WS2, a representative visible-light photodetector material, and improvement of photocurrent was confirmed by providing additional carriers via the localized surface plasmon resonance phenomenon. Furthermore, preferentially growing at high surface energy points, such as defects on WS2 nanosheets, can suppress the capture of photoexcited electrons by defects, consequently extending the carrier lifetime and preventing surface oxidation of the device. In the wavelength range of 500–1200 nm, the photoresponsivity of the ALD Pt-functionalized WS2 photodetector was improved more than 10–20 times compared to pristine WS2, and the response time was also noticeably improved. This study presents a novel approach to Pt functionalization using ALD, opening new possibilities for advanced nanodevice applications.
{"title":"Atomic layer deposition of Pt nanoparticles using dimethyl (N, N–dimethyl-3-butene-1-amine−N) platinum and H2 reactant and its application to 2D WS2 photodetectors","authors":"Dain Shin, Inkyu Sohn, Donghyun Kim, Jaehyeok Kim, Taewook Nam, Youngjun Kim, Jusang Park, Tatsuya Nakazawa, Seung-min Chung, Hyungjun Kim","doi":"10.1116/6.0003194","DOIUrl":"https://doi.org/10.1116/6.0003194","url":null,"abstract":"2D transition metal dichalcogenides (2D TMDCs) have thin and flexible structures and can be widely applied to nanoelectronics technology as a representative of 2D materials. Research studies on the surface functionalization of 2D TMDCs with nanoparticles have been actively conducted for fabrication of high-performance devices. Specifically, platinum (Pt) has attracted significant attention as a surface functionalization material in various applications, including photosensors, biosensors, and gas sensors due to its effective catalytic effect and excellent corrosion resistance. However, solution-based methods and PVD technologies, widely used for Pt nanoparticle synthesis, have difficulties forming fine particles dispersed on nanomaterials. Atomic layer deposition (ALD) is emerging as an advantageous method for forming nanoparticles, and dimethyl (N,N-dimethyl-3-buten-1-amine-N) platinum (DDAP) can overcome disadvantages of conventional ALD Pt precursors. In this study, we successfully synthesized Pt films using hydrogen as a new reactant in the DDAP-based ALD Pt process and evaluated formation of nanoparticles on SiO2/Si substrates. Subsequently, the ALD Pt-functionalized photodetector was fabricated with 2D WS2, a representative visible-light photodetector material, and improvement of photocurrent was confirmed by providing additional carriers via the localized surface plasmon resonance phenomenon. Furthermore, preferentially growing at high surface energy points, such as defects on WS2 nanosheets, can suppress the capture of photoexcited electrons by defects, consequently extending the carrier lifetime and preventing surface oxidation of the device. In the wavelength range of 500–1200 nm, the photoresponsivity of the ALD Pt-functionalized WS2 photodetector was improved more than 10–20 times compared to pristine WS2, and the response time was also noticeably improved. This study presents a novel approach to Pt functionalization using ALD, opening new possibilities for advanced nanodevice applications.","PeriodicalId":509398,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139393868","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jiqiang Jia, Jingran Li, Chen Liu, Fuxue Yan, Tao Zhang, Li Lei
Due to the great differences in electron pairing characteristics between the hole-type (p-type) high-temperature superconductor (HTS) and the electron-type (n-type) HTS, when the Cooper pairs enter from a p-type to an n-type HTS or an n-type to a p-type HTS, pairing adjustment or even the recombination of them will inevitably occur at the interface, and the superconducting current dominated by them will be bound to change. Therefore, it is possible to better understand the electron pairing mechanism of the HTS and develop new HTS junction devices by studying these changes. In this paper, p-/n-type YBa2Cu3O7−δ/Nd1.85Ce0.15CuO4 (YBCO/NCCO) heterostructures were prepared via pulsed laser deposition on (00l)-oriented single-crystal SrTiO3 substrates. X-ray diffraction measurements indicate that the NCCO films prepared on YBCO do not exhibit good c-axis epitaxial growth, while excellent c-axis epitaxial growth is obtained for YBCO/NCCO heterostructures with NCCO at the bottom. Due to the high-temperature oxygen atmosphere and the deoxygenation process, the superconducting electrical properties of the bilayer structure are seriously degraded, and it is not possible to obtain good superconducting electrical properties for both the upper and lower layers using the traditional preparation process based on an oxygen atmosphere. Subsequently, the effects of different growth atmospheres on the electrical properties of the YBCO superconductors were studied, and high-quality YBCO superconducting films could be grown in oxygen, nitrous oxide, and nitrogen atmospheres. However, the oxygen and nitrous oxide atmospheres degrade the superconducting electrical properties of the underlying NCCO layer, while the nitrogen atmosphere does not seem to affect it significantly. YBCO/NCCO superconducting bilayers with critical transition temperatures of 85 and 8 K for YBCO and NCCO, respectively, were finally prepared by growing NCCO in an oxygen atmosphere and YBCO in a nitrogen atmosphere using a low-temperature oxygenation process. The successful preparation of the p-/n-type HTS heterostructure will help further study on the HTS.
由于空穴型（p 型）高温超导体（HTS）和电子型（n 型）高温超导体（HTS）的电子配对特性存在很大差异，当库珀对从 p 型进入 n 型高温超导体或从 n 型进入 p 型高温超导体时，在界面上不可避免地会发生配对调整甚至重组，由它们主导的超导电流必然会发生变化。因此，通过研究这些变化，可以更好地理解 HTS 的电子配对机制，并开发出新的 HTS 结器件。本文通过脉冲激光沉积法在（00l）取向单晶 SrTiO3 衬底上制备了 p/n 型 YBa2Cu3O7-δ/Nd1.85Ce0.15CuO4 （YBCO/NCCO）异质结构。X 射线衍射测量结果表明，在 YBCO 上制备的 NCCO 薄膜并没有表现出良好的 c 轴外延生长，而底部含有 NCCO 的 YBCO/NCCO 异质结构则获得了良好的 c 轴外延生长。由于高温氧气氛和脱氧过程的影响，双层结构的超导电学性能严重下降，使用传统的基于氧气氛的制备工艺无法获得上下层良好的超导电学性能。随后，研究人员研究了不同生长气氛对 YBCO 超导电学特性的影响，发现在氧气、氧化亚氮和氮气气氛中都能生长出高质量的 YBCO 超导薄膜。然而，氧气和一氧化二氮气氛会降低底层 NCCO 层的超导电特性，而氮气气氛似乎对其影响不大。通过低温充氧工艺，NCCO 在氧气环境中生长，YBCO 在氮气环境中生长，最终制备出了 YBCO/NCCO 超导双层层，YBCO 和 NCCO 的临界转变温度分别为 85 K 和 8 K。p/n 型 HTS 异质结构的成功制备将有助于对 HTS 的进一步研究。
{"title":"Preparation of p/n-type YBa2Cu3O7−δ/Nd1.85Ce0.15CuO4 superconducting heterostructures","authors":"Jiqiang Jia, Jingran Li, Chen Liu, Fuxue Yan, Tao Zhang, Li Lei","doi":"10.1116/6.0003200","DOIUrl":"https://doi.org/10.1116/6.0003200","url":null,"abstract":"Due to the great differences in electron pairing characteristics between the hole-type (p-type) high-temperature superconductor (HTS) and the electron-type (n-type) HTS, when the Cooper pairs enter from a p-type to an n-type HTS or an n-type to a p-type HTS, pairing adjustment or even the recombination of them will inevitably occur at the interface, and the superconducting current dominated by them will be bound to change. Therefore, it is possible to better understand the electron pairing mechanism of the HTS and develop new HTS junction devices by studying these changes. In this paper, p-/n-type YBa2Cu3O7−δ/Nd1.85Ce0.15CuO4 (YBCO/NCCO) heterostructures were prepared via pulsed laser deposition on (00l)-oriented single-crystal SrTiO3 substrates. X-ray diffraction measurements indicate that the NCCO films prepared on YBCO do not exhibit good c-axis epitaxial growth, while excellent c-axis epitaxial growth is obtained for YBCO/NCCO heterostructures with NCCO at the bottom. Due to the high-temperature oxygen atmosphere and the deoxygenation process, the superconducting electrical properties of the bilayer structure are seriously degraded, and it is not possible to obtain good superconducting electrical properties for both the upper and lower layers using the traditional preparation process based on an oxygen atmosphere. Subsequently, the effects of different growth atmospheres on the electrical properties of the YBCO superconductors were studied, and high-quality YBCO superconducting films could be grown in oxygen, nitrous oxide, and nitrogen atmospheres. However, the oxygen and nitrous oxide atmospheres degrade the superconducting electrical properties of the underlying NCCO layer, while the nitrogen atmosphere does not seem to affect it significantly. YBCO/NCCO superconducting bilayers with critical transition temperatures of 85 and 8 K for YBCO and NCCO, respectively, were finally prepared by growing NCCO in an oxygen atmosphere and YBCO in a nitrogen atmosphere using a low-temperature oxygenation process. The successful preparation of the p-/n-type HTS heterostructure will help further study on the HTS.","PeriodicalId":509398,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139392942","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Transition metal nitride alloys possess exceptional properties, making them suitable for cutting applications due to their inherent hardness or as protective coatings due to corrosion resistance. However, the computational demands associated with predicting these properties using ab initio methods can often be prohibitively high at the conditions of their operation at cutting tools, that is, at high temperatures and stresses. Machine learning approaches have been introduced into the field of materials modeling to address the challenge. In this paper, we present an active learning workflow to model the properties of our benchmark alloy system cubic B1 Ti0.5Al0.5N at temperatures up to 1500 K. With a minimal requirement of prior knowledge about the alloy system for our workflow, we train a moment tensor potential (MTP) to accurately model the material’s behavior over the entire temperature range and extract elastic and vibrational properties. The outstanding accuracy of MTPs with relatively little training data demonstrates that the presented approach is highly efficient and requires about two orders of magnitude less computational resources than state-of-the-art ab initio molecular dynamics.
过渡金属氮化物合金具有优异的性能，因其固有的硬度而适用于切削应用，或因其耐腐蚀性而用作保护涂层。然而，在切削工具的工作条件下，即在高温和应力条件下，使用ab initio方法预测这些特性所需的计算量往往过高，令人望而却步。为应对这一挑战，机器学习方法已被引入材料建模领域。在本文中，我们介绍了一种主动学习工作流程，用于对温度高达 1500 K 的基准合金系统立方体 B1 Ti0.5Al0.5N 的特性进行建模。我们的工作流程对合金系统的先验知识要求极低，通过训练力矩张量势（MTP）来精确建模材料在整个温度范围内的行为，并提取弹性和振动特性。在训练数据相对较少的情况下，MTP 的精确度非常高，这表明所提出的方法非常高效，所需的计算资源比最先进的原子分子动力学少两个数量级。
{"title":"Active learning with moment tensor potentials to predict material properties: Ti0.5Al0.5N at elevated temperature","authors":"F. Bock, F. Tasnádi, I. A. Abrikosov","doi":"10.1116/6.0003260","DOIUrl":"https://doi.org/10.1116/6.0003260","url":null,"abstract":"Transition metal nitride alloys possess exceptional properties, making them suitable for cutting applications due to their inherent hardness or as protective coatings due to corrosion resistance. However, the computational demands associated with predicting these properties using ab initio methods can often be prohibitively high at the conditions of their operation at cutting tools, that is, at high temperatures and stresses. Machine learning approaches have been introduced into the field of materials modeling to address the challenge. In this paper, we present an active learning workflow to model the properties of our benchmark alloy system cubic B1 Ti0.5Al0.5N at temperatures up to 1500 K. With a minimal requirement of prior knowledge about the alloy system for our workflow, we train a moment tensor potential (MTP) to accurately model the material’s behavior over the entire temperature range and extract elastic and vibrational properties. The outstanding accuracy of MTPs with relatively little training data demonstrates that the presented approach is highly efficient and requires about two orders of magnitude less computational resources than state-of-the-art ab initio molecular dynamics.","PeriodicalId":509398,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139393803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Saha, R. Knut, A. Gupta, F. Radu, C. Luo, O. Karis, D. Arena
We report on the x-ray absorption spectra (XAS) and x-ray magnetic circular dichroism (XMCD) of a series of NiFe2O4 (Ni ferrite) films grown on symmetry matched substrates and measured in two geometries: out-of-plane and near in-plane. The Ni ferrite films, grown by pulsed laser deposition, are epitaxial and the substrates used (ZnGa2O4, CoGa2O4, MgGa2O4, and MgAl2O4) introduce a systematic variation in the lattice mismatch between the substrate and the film. Modeling of the XAS and XMCD spectra, both measured with the surface sensitive total electron yield mode, indicates that the Ni2+ cations reside on the octahedrally coordinated lattice sites in the spinel structure. Analyses of the Fe XAS and XMCD spectra are consistent with Fe3+ cations occupying a subset of the octahedral and tetrahedral sites in the spinel oxide lattice with the addition of a small amount of Fe2+ located on octahedral sites. The Ni2+ orbital to spin moment ratio (μℓ/μs), derived from the application of XMCD sum rules, is enhanced for the substrates with a small lattice mismatch relative to NiFe2O4. The results suggest a path for increasing the orbital moment in NiFe2O4 by applying thin film growth techniques that can maintain a highly strained lattice for the NiFe2O4 film.
我们报告了在对称匹配基底上生长的一系列 NiFe2O4（镍铁氧体）薄膜的 X 射线吸收光谱 (XAS) 和 X 射线磁性圆二色性 (XMCD)，并在两种几何形状下进行了测量：面外和近面内。通过脉冲激光沉积法生长的镍铁氧体薄膜是外延型的，所使用的基底（ZnGa2O4、CoGa2O4、MgGa2O4 和 MgAl2O4）会导致基底和薄膜之间的晶格失配发生系统性变化。XAS 和 XMCD 光谱（均采用表面敏感的总电子产率模式测量）的建模表明，Ni2+ 阳离子位于尖晶石结构中的八面体配位晶格位点上。对 Fe XAS 和 XMCD 光谱的分析表明，Fe3+ 阳离子占据了尖晶石氧化物晶格中八面体和四面体位点的一部分，另外还有少量位于八面体位点上的 Fe2+。应用 XMCD 和规则推导出的 Ni2+ 轨道与自旋矩比率（μℓ/μs），在相对于 NiFe2O4 具有较小晶格失配的基质中得到增强。研究结果表明，通过应用薄膜生长技术，可以保持 NiFe2O4 薄膜的高应变晶格，从而提高 NiFe2O4 的轨道力矩。
{"title":"Near-surface electronic structure in strained Ni-ferrite films: An x-ray absorption spectroscopy study","authors":"S. Saha, R. Knut, A. Gupta, F. Radu, C. Luo, O. Karis, D. Arena","doi":"10.1116/6.0003095","DOIUrl":"https://doi.org/10.1116/6.0003095","url":null,"abstract":"We report on the x-ray absorption spectra (XAS) and x-ray magnetic circular dichroism (XMCD) of a series of NiFe2O4 (Ni ferrite) films grown on symmetry matched substrates and measured in two geometries: out-of-plane and near in-plane. The Ni ferrite films, grown by pulsed laser deposition, are epitaxial and the substrates used (ZnGa2O4, CoGa2O4, MgGa2O4, and MgAl2O4) introduce a systematic variation in the lattice mismatch between the substrate and the film. Modeling of the XAS and XMCD spectra, both measured with the surface sensitive total electron yield mode, indicates that the Ni2+ cations reside on the octahedrally coordinated lattice sites in the spinel structure. Analyses of the Fe XAS and XMCD spectra are consistent with Fe3+ cations occupying a subset of the octahedral and tetrahedral sites in the spinel oxide lattice with the addition of a small amount of Fe2+ located on octahedral sites. The Ni2+ orbital to spin moment ratio (μℓ/μs), derived from the application of XMCD sum rules, is enhanced for the substrates with a small lattice mismatch relative to NiFe2O4. The results suggest a path for increasing the orbital moment in NiFe2O4 by applying thin film growth techniques that can maintain a highly strained lattice for the NiFe2O4 film.","PeriodicalId":509398,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139393973","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rachel A. Nye, Nicholas M. Carroll, Sarah E. Morgan, Gregory N. Parsons
The use of metal-organic frameworks (MOFs) in practical applications is often hindered by synthesis related challenges. Conventional solution-based approaches rely on hazardous solvents and often form powders that are difficult to integrate into practical devices. On the other hand, vapor-phase approaches generally result in MOF films on silicon substrates that make it difficult to characterize the MOF surface area, which is an important quality indicator. We address these challenges by introducing a solvent-free synthesis method to form MOF–fiber composites, which can be more easily integrated into devices. Additionally, these vapor-phase-formed MOF–fiber composites are compatible with Brunauer–Emmett–Teller surface area analysis to characterize MOF quality. Atomic layer deposition is used to form a ZnO film on polypropylene, polyester, and nylon fibrous substrates, which is subsequently converted to zeolitic imidazolate framework-8 (ZIF-8) using 2-methylimidazole vapor. We describe the effects of the ZnO film thickness and MOF conversion conditions on MOF crystallinity and surface area. We report a ZIF-8 surface area of ∼1300 m2/gMOF, which is comparable to reported surface areas of ∼1250–1600 m2/gMOF from conventional synthesis techniques, demonstrating good quality of the solvent-free MOF–fiber composites. We expect these results to extend vapor-phase MOF formation to new, practical substrates for advanced sensing and catalytic applications.
{"title":"Vapor-phase zeolitic imidazolate framework-8 growth on fibrous polymer substrates","authors":"Rachel A. Nye, Nicholas M. Carroll, Sarah E. Morgan, Gregory N. Parsons","doi":"10.1116/6.0003183","DOIUrl":"https://doi.org/10.1116/6.0003183","url":null,"abstract":"The use of metal-organic frameworks (MOFs) in practical applications is often hindered by synthesis related challenges. Conventional solution-based approaches rely on hazardous solvents and often form powders that are difficult to integrate into practical devices. On the other hand, vapor-phase approaches generally result in MOF films on silicon substrates that make it difficult to characterize the MOF surface area, which is an important quality indicator. We address these challenges by introducing a solvent-free synthesis method to form MOF–fiber composites, which can be more easily integrated into devices. Additionally, these vapor-phase-formed MOF–fiber composites are compatible with Brunauer–Emmett–Teller surface area analysis to characterize MOF quality. Atomic layer deposition is used to form a ZnO film on polypropylene, polyester, and nylon fibrous substrates, which is subsequently converted to zeolitic imidazolate framework-8 (ZIF-8) using 2-methylimidazole vapor. We describe the effects of the ZnO film thickness and MOF conversion conditions on MOF crystallinity and surface area. We report a ZIF-8 surface area of ∼1300 m2/gMOF, which is comparable to reported surface areas of ∼1250–1600 m2/gMOF from conventional synthesis techniques, demonstrating good quality of the solvent-free MOF–fiber composites. We expect these results to extend vapor-phase MOF formation to new, practical substrates for advanced sensing and catalytic applications.","PeriodicalId":509398,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139394439","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
B. Beake, Vladimir M. Vishnyakov, S. R. Goodes, Azadeh Taher Rahmati
For studying the damage tolerance of thin films, a novel randomly distributed nano-scratch test method was introduced and demonstrated as a promising characterization method. It is capable of more closely simulating the damage progression in abrasion, where material removal can be influenced by the interaction between damage produced by previous scratches in close proximity. In addition to studying how localized failure events affect subsequent damage progression, it is possible to monitor the evolution of the film degradation cycle-by-cycle using the mean depth and friction over the scratch. Randomly distributed nano-scratch tests were performed on the high entropy alloy AlFeMnNb, AlFeMnNi, and nanocomposite (nc-) TiN/Si3N4 thin films on silicon. Brittle fracture and film removal with extensive chipping of the Si substrate were observed over the entire scratched region on AlFeMnNi and nc-TiN/Si3N4 in distributed scratch tests at applied loads that were only ∼0.2–0.3 of the load needed to produce the chipping in ramped load nano-scratch tests due to film and substrate fatigue. In contrast, the softer AlFeMnNb deformed predominantly by ductile ploughing with significantly improved damage tolerance and crack resistance in the distributed scratch tests. The new method can be used to evaluate the performance of thin films in applications where they can be exposed to abrasive/sliding wear. It can provide a more direct measure of abrasion resistance than assuming high resistance to abrasive wear from coating hardness. In the thin film systems studied, higher hardness was associated with greater fracture and delamination in the distributed scratch tests.
{"title":"Statistically distributed nano-scratch testing of AlFeMnNb, AlFeMnNi, and TiN/Si3N4 thin films on silicon","authors":"B. Beake, Vladimir M. Vishnyakov, S. R. Goodes, Azadeh Taher Rahmati","doi":"10.1116/6.0003189","DOIUrl":"https://doi.org/10.1116/6.0003189","url":null,"abstract":"For studying the damage tolerance of thin films, a novel randomly distributed nano-scratch test method was introduced and demonstrated as a promising characterization method. It is capable of more closely simulating the damage progression in abrasion, where material removal can be influenced by the interaction between damage produced by previous scratches in close proximity. In addition to studying how localized failure events affect subsequent damage progression, it is possible to monitor the evolution of the film degradation cycle-by-cycle using the mean depth and friction over the scratch. Randomly distributed nano-scratch tests were performed on the high entropy alloy AlFeMnNb, AlFeMnNi, and nanocomposite (nc-) TiN/Si3N4 thin films on silicon. Brittle fracture and film removal with extensive chipping of the Si substrate were observed over the entire scratched region on AlFeMnNi and nc-TiN/Si3N4 in distributed scratch tests at applied loads that were only ∼0.2–0.3 of the load needed to produce the chipping in ramped load nano-scratch tests due to film and substrate fatigue. In contrast, the softer AlFeMnNb deformed predominantly by ductile ploughing with significantly improved damage tolerance and crack resistance in the distributed scratch tests. The new method can be used to evaluate the performance of thin films in applications where they can be exposed to abrasive/sliding wear. It can provide a more direct measure of abrasion resistance than assuming high resistance to abrasive wear from coating hardness. In the thin film systems studied, higher hardness was associated with greater fracture and delamination in the distributed scratch tests.","PeriodicalId":509398,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139392235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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