Oxide semiconductor is one of the most promising candidates for photocatalysts due to its light absorption ability, electronic properties, and stability. It is used in various applications such as solar-energy conversion, CO2 reduction, and water splitting. In this research, ZnO, TiO2, and ZnO/TiO2 heterostructured thin films are fabricated via atomic layer deposition (ALD), and their photocatalytic performances are evaluated. The film thickness can be controlled using ALD, and surface reactions can easily occur in thin films owing to the short distances between the active sites and charge carriers. In addition, unlike a powder catalyst, the bilayer photocatalyst is fixed in the solution; therefore, it does not make the solution turbid or disturb the light penetration. Diethylzinc and titanium tetraisopropoxide are used as precursors for Zn and Ti, and the thin films are deposited on soda-lime glass substrates at 150 °C using H2O as the reactant gas. The photocatalytic activity and stability are evaluated through photodegradation tests using methylene blue aqueous solution. The ZnO single-substance thin film exhibits a high degradation rate, but its performance significantly decreases after three consecutive experiments. The TiO2 single-substance thin film exhibits a relatively low degradation rate, but high reusability, exhibiting characteristics opposite to that of ZnO. Therefore, a TiO2 thin film is coated on ZnO to leverage both these advantages. The thin films are heat-treated at 400 °C for 10 min after deposition in a vacuum atmosphere. The surface morphology, crystal structure, and electrical characteristics of the photocatalyst specimens are analyzed through high-resolution scanning electron microscopy, Cs-corrected scanning transmission electron microscopy, and x-ray diffraction analysis. Their photocatalytic performances under ultraviolet (UV) irradiation are measured through UV–visible spectroscopy. The heat-treated ZnO/TiO2 heterostructured thin film exhibits a photodegradation rate exceeding 80%, with little degeneration after three cycles, indicating enhanced photodegradation performance and stability.
氧化物半导体具有光吸收能力、电子特性和稳定性，是最有前途的光催化剂候选材料之一。它被广泛应用于太阳能转换、二氧化碳还原和水分离等领域。本研究通过原子层沉积（ALD）技术制备了 ZnO、TiO2 和 ZnO/TiO2 异质结构薄膜，并评估了它们的光催化性能。利用原子层沉积可以控制薄膜的厚度，由于活性位点与电荷载流子之间的距离很短，薄膜中很容易发生表面反应。此外，与粉末催化剂不同，双层光催化剂固定在溶液中，因此不会使溶液浑浊，也不会干扰光的穿透。二乙基锌和四异丙醇钛被用作锌和钛的前驱体，薄膜在 150 °C 下沉积在钠钙玻璃基底上，以 H2O 作为反应气体。通过使用亚甲基蓝水溶液进行光降解试验，评估了光催化活性和稳定性。ZnO 单质薄膜表现出较高的降解率，但连续三次实验后其性能明显下降。二氧化钛单质薄膜的降解率相对较低，但可重复使用性较高，表现出与氧化锌相反的特性。因此，在 ZnO 上镀一层 TiO2 薄膜，以充分利用这两个优点。薄膜在真空环境中沉积后，在 400 °C 下热处理 10 分钟。通过高分辨率扫描电子显微镜、铯校正扫描透射电子显微镜和 X 射线衍射分析，对光催化剂试样的表面形貌、晶体结构和电学特性进行了分析。它们在紫外线（UV）照射下的光催化性能是通过紫外可见光谱测量的。经过热处理的 ZnO/TiO2 异质结构薄膜的光降解率超过了 80%，并且在三个周期后几乎没有退化，这表明其光降解性能和稳定性得到了增强。
{"title":"High-performance of ZnO/TiO2 heterostructured thin-film photocatalyst fabricated via atomic layer deposition","authors":"Ji Young Park, Jeong Hwan Han, Byung Joon Choi","doi":"10.1116/6.0003348","DOIUrl":"https://doi.org/10.1116/6.0003348","url":null,"abstract":"Oxide semiconductor is one of the most promising candidates for photocatalysts due to its light absorption ability, electronic properties, and stability. It is used in various applications such as solar-energy conversion, CO2 reduction, and water splitting. In this research, ZnO, TiO2, and ZnO/TiO2 heterostructured thin films are fabricated via atomic layer deposition (ALD), and their photocatalytic performances are evaluated. The film thickness can be controlled using ALD, and surface reactions can easily occur in thin films owing to the short distances between the active sites and charge carriers. In addition, unlike a powder catalyst, the bilayer photocatalyst is fixed in the solution; therefore, it does not make the solution turbid or disturb the light penetration. Diethylzinc and titanium tetraisopropoxide are used as precursors for Zn and Ti, and the thin films are deposited on soda-lime glass substrates at 150 °C using H2O as the reactant gas. The photocatalytic activity and stability are evaluated through photodegradation tests using methylene blue aqueous solution. The ZnO single-substance thin film exhibits a high degradation rate, but its performance significantly decreases after three consecutive experiments. The TiO2 single-substance thin film exhibits a relatively low degradation rate, but high reusability, exhibiting characteristics opposite to that of ZnO. Therefore, a TiO2 thin film is coated on ZnO to leverage both these advantages. The thin films are heat-treated at 400 °C for 10 min after deposition in a vacuum atmosphere. The surface morphology, crystal structure, and electrical characteristics of the photocatalyst specimens are analyzed through high-resolution scanning electron microscopy, Cs-corrected scanning transmission electron microscopy, and x-ray diffraction analysis. Their photocatalytic performances under ultraviolet (UV) irradiation are measured through UV–visible spectroscopy. The heat-treated ZnO/TiO2 heterostructured thin film exhibits a photodegradation rate exceeding 80%, with little degeneration after three cycles, indicating enhanced photodegradation performance and stability.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"71 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140234467","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}
Difei Xue, Peiwen Lv, Kai Peng, Qiang Hu, Chen Chen
Solar-blind photodetectors (SBPDs) based on the ultrawide-bandgap semiconductor Ga2O3 have gained attention due to their potential applications in both military and civilian domains. As technology advances, photodetectors are being improved to achieve better energy efficiency, smaller size, and better performance. Solar-blind photodetectors based on a metal-semiconductor-metal structure of amorphous gallium oxide (a-Ga2O3) films were fabricated by pulsed magnetron sputtering deposition (PSD). The photodetector based on amorphous gallium oxide has a responsivity of 71.52 A/W, a fast rising and falling response time of less than 200 ms, a photo-to-dark current ratio (PDCR) of 6.52 × 104, and an external quantum efficiency of 34 526.62%. PSD-prepared gallium oxide SBPDs demonstrate a cost-effective room temperature method for growing gallium oxide and show the advantages of growing gallium oxide.
{"title":"High-performance a-Ga2O3 solar-blind photodetectors by pulsed magnetron sputtering deposition","authors":"Difei Xue, Peiwen Lv, Kai Peng, Qiang Hu, Chen Chen","doi":"10.1116/6.0003442","DOIUrl":"https://doi.org/10.1116/6.0003442","url":null,"abstract":"Solar-blind photodetectors (SBPDs) based on the ultrawide-bandgap semiconductor Ga2O3 have gained attention due to their potential applications in both military and civilian domains. As technology advances, photodetectors are being improved to achieve better energy efficiency, smaller size, and better performance. Solar-blind photodetectors based on a metal-semiconductor-metal structure of amorphous gallium oxide (a-Ga2O3) films were fabricated by pulsed magnetron sputtering deposition (PSD). The photodetector based on amorphous gallium oxide has a responsivity of 71.52 A/W, a fast rising and falling response time of less than 200 ms, a photo-to-dark current ratio (PDCR) of 6.52 × 104, and an external quantum efficiency of 34 526.62%. PSD-prepared gallium oxide SBPDs demonstrate a cost-effective room temperature method for growing gallium oxide and show the advantages of growing gallium oxide.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"7 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140242962","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}
Xiaoning Zhang, Xi Liang, Xing Li, Yuan Li, Jia-yue Yang, Linhua Liu
β-Ga2O3 with an ultra-wide bandgap demonstrates great promise in applications of space missions as power electronics and solar-blind photodetector. Unraveling the radiation damage effects on its material properties is of crucial importance, especially for improving the radiation tolerance of Ga2O3-based devices. Herein, we evaluate the formation energy of gallium and oxygen vacancy defects and comprehensively investigate their influence on the electronic and optical properties of β-Ga2O3 using first-principles calculations. Ga vacancies act as deep acceptors and produce p-type defects in β-Ga2O3, while the defective Ga2O3 with O vacancies exhibits the n-type characteristics. A semimetal characteristic is observed in the defective Ga2O3 with Ga vacancies, and an apparent optical absorption peak in the infrared spectral range emerges. Moreover, the self-compensation effect emerges when β-Ga2O3 contains both Ga vacancies and O vacancies, leading to the reduced absorption peak. The doping effect on the defect formation energy of β-Ga2O3 is also investigated, and Ga vacancies are found to be easily formed in the case of In doped β-Ga2O3 (InGa2O3) compared to the undoped β-Ga2O3, while O vacancies are much harder to form. This work provides insights into how gallium and oxygen vacancy defects alter electronic and optical properties of β-Ga2O3, seeking to strengthen its radiation tolerance.
具有超宽带隙的β-Ga2O3 在作为电力电子器件和日盲光电探测器的太空任务应用中大有可为。揭示辐射损伤对其材料特性的影响至关重要，尤其是对于提高基于 Ga2O3 的器件的辐射耐受性。在此，我们利用第一原理计算评估了镓和氧空位缺陷的形成能，并全面研究了它们对 β-Ga2O3 电子和光学特性的影响。镓空位作为深受体在 β-Ga2O3 中产生 p 型缺陷，而含有 O 空位的 Ga2O3 缺陷则表现出 n 型特性。在含有 Ga 空位的缺陷 Ga2O3 中观察到了半金属特性，并在红外光谱范围内出现了明显的光吸收峰。此外，当 β-Ga2O3 同时含有 Ga 空位和 O 空位时，会出现自我补偿效应，导致吸收峰值降低。研究还探讨了掺杂对 β-Ga2O3 缺陷形成能的影响，发现与未掺杂的 β-Ga2O3 相比，掺 In 的 β-Ga2O3 （InGa2O3）很容易形成 Ga 空位，而 O 空位则更难形成。这项研究深入探讨了镓和氧空位缺陷如何改变 β-Ga2O3 的电子和光学特性，从而寻求增强其辐射耐受性。
{"title":"Radiation damage effects on electronic and optical properties of β-Ga2O3 from first-principles","authors":"Xiaoning Zhang, Xi Liang, Xing Li, Yuan Li, Jia-yue Yang, Linhua Liu","doi":"10.1116/6.0003430","DOIUrl":"https://doi.org/10.1116/6.0003430","url":null,"abstract":"β-Ga2O3 with an ultra-wide bandgap demonstrates great promise in applications of space missions as power electronics and solar-blind photodetector. Unraveling the radiation damage effects on its material properties is of crucial importance, especially for improving the radiation tolerance of Ga2O3-based devices. Herein, we evaluate the formation energy of gallium and oxygen vacancy defects and comprehensively investigate their influence on the electronic and optical properties of β-Ga2O3 using first-principles calculations. Ga vacancies act as deep acceptors and produce p-type defects in β-Ga2O3, while the defective Ga2O3 with O vacancies exhibits the n-type characteristics. A semimetal characteristic is observed in the defective Ga2O3 with Ga vacancies, and an apparent optical absorption peak in the infrared spectral range emerges. Moreover, the self-compensation effect emerges when β-Ga2O3 contains both Ga vacancies and O vacancies, leading to the reduced absorption peak. The doping effect on the defect formation energy of β-Ga2O3 is also investigated, and Ga vacancies are found to be easily formed in the case of In doped β-Ga2O3 (InGa2O3) compared to the undoped β-Ga2O3, while O vacancies are much harder to form. This work provides insights into how gallium and oxygen vacancy defects alter electronic and optical properties of β-Ga2O3, seeking to strengthen its radiation tolerance.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"86 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140250805","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}
Henry Dempwolf, S. Malz, Alexander Schacht, Christian Fabry, Axel Baumann, Olaf Kessler
Titanium-based physical vapor deposition (PVD) coatings, such as titanium nitride (TiN) and titanium niobium nitride (TiNbN), are common solutions for surface modifications in medical applications. Ex vivo studies of retrieved knee implants indicate the demand for increased scratch and abrasion resistance of PVD coatings in clinical applications. Based on the promising mechanical performance of titanium aluminum nitride (TiAlN) as a coating for tools, the aim of this study was to evaluate the impact of the chemical composition of titanium-based nitride coatings with aluminum (Al) and niobium (Nb). Nine titanium aluminum niobium nitride (Ti1−x−yAlxNbyN) coatings with 0.4 ≤ x < 0.7 and 0 ≤ y ≤ 0.18, as well as commercial TiN and TiNbN, were coated in an industrial scale arc PVD process, following a randomized, multifactorial response surface design. The deposition rate, the scratch resistance, and the hardness were measured following standardized protocols. The microstructure of the coating was analyzed by SEM and XRD. In addition, the surface roughness was determined by laser scanning microscopy. A quadratic regression was performed to determine the impact of the chemical composition on coating properties. Experimental results and regression analyses revealed the significant impact of the chemical composition of Ti1−x−yAlxNbyN on the coating microstructure, mechanics, and morphology. Scratch resistance for initial crack formation and cohesive failure could be increased decisively, compared to TiN.
钛基物理气相沉积（PVD）涂层，如氮化钛（TiN）和氮化铌钛（TiNbN），是医疗应用中常见的表面改性解决方案。对取回的膝关节植入物进行的体内外研究表明，临床应用中需要提高 PVD 涂层的抗划伤和耐磨性。鉴于氮化钛铝（TiAlN）作为工具涂层具有良好的机械性能，本研究旨在评估铝（Al）和铌（Nb）化学成分对钛基氮化涂层的影响。采用随机多因素响应面设计，在工业规模的电弧 PVD 过程中涂覆了九种 0.4 ≤ x < 0.7 和 0 ≤ y ≤ 0.18 的钛铝铌氮化物（Ti1-x-yAlxNbyN）涂层，以及商用 TiN 和 TiNbN。涂层的沉积率、抗划伤性和硬度都是按照标准化规程测量的。涂层的微观结构通过 SEM 和 XRD 进行了分析。此外，还利用激光扫描显微镜测定了表面粗糙度。为确定化学成分对涂层性能的影响，进行了二次回归。实验结果和回归分析表明，Ti1-x-yAlxNbyN 的化学成分对涂层的微观结构、力学和形态有显著影响。与 TiN 相比，最初裂纹形成和内聚失效的抗划伤性得到了决定性的提高。
{"title":"Impact of Nb and Al content in arc evaporation targets on Ti1−x−yAlxNbyN coating properties","authors":"Henry Dempwolf, S. Malz, Alexander Schacht, Christian Fabry, Axel Baumann, Olaf Kessler","doi":"10.1116/6.0003409","DOIUrl":"https://doi.org/10.1116/6.0003409","url":null,"abstract":"Titanium-based physical vapor deposition (PVD) coatings, such as titanium nitride (TiN) and titanium niobium nitride (TiNbN), are common solutions for surface modifications in medical applications. Ex vivo studies of retrieved knee implants indicate the demand for increased scratch and abrasion resistance of PVD coatings in clinical applications. Based on the promising mechanical performance of titanium aluminum nitride (TiAlN) as a coating for tools, the aim of this study was to evaluate the impact of the chemical composition of titanium-based nitride coatings with aluminum (Al) and niobium (Nb). Nine titanium aluminum niobium nitride (Ti1−x−yAlxNbyN) coatings with 0.4 ≤ x < 0.7 and 0 ≤ y ≤ 0.18, as well as commercial TiN and TiNbN, were coated in an industrial scale arc PVD process, following a randomized, multifactorial response surface design. The deposition rate, the scratch resistance, and the hardness were measured following standardized protocols. The microstructure of the coating was analyzed by SEM and XRD. In addition, the surface roughness was determined by laser scanning microscopy. A quadratic regression was performed to determine the impact of the chemical composition on coating properties. Experimental results and regression analyses revealed the significant impact of the chemical composition of Ti1−x−yAlxNbyN on the coating microstructure, mechanics, and morphology. Scratch resistance for initial crack formation and cohesive failure could be increased decisively, compared to TiN.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"38 S24","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140250883","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}
A broadband absorber composed of a TiAlC/SiO2 film stack prepared by atomic layer deposition was presented, which could be uniformly coated on magnesium alloys with large curvature, achieving an average absorption as high as 99.4% within the wavelength range from 400 to 1000 nm. An Al2O3/TiO2 interlayer was deposited on magnesium alloys prior to the deposition of ultrablack films, which effectively prevented corrosion of magnesium caused by Al3+ and Cl− by-products in the TiAlC film. With the presence of this interlayer, the ultrablack film on the surface of the magnesium alloy exhibited good adhesion and abrasion resistance. Furthermore, after undergoing damp heat and thermal cycling tests, the absorptions of the ultrablack film-coated magnesium alloys remained at 99.1% and 99.0%, respectively, which indicated that the film is promising for application in precision optics under harsh environmental conditions.
{"title":"Robust ultrablack film deposited on large-curvature magnesium alloy by atomic layer deposition","authors":"Jianfei Jin, Lin Lv, Lu Yan, Ying Li, Yunzhen Cao","doi":"10.1116/6.0003305","DOIUrl":"https://doi.org/10.1116/6.0003305","url":null,"abstract":"A broadband absorber composed of a TiAlC/SiO2 film stack prepared by atomic layer deposition was presented, which could be uniformly coated on magnesium alloys with large curvature, achieving an average absorption as high as 99.4% within the wavelength range from 400 to 1000 nm. An Al2O3/TiO2 interlayer was deposited on magnesium alloys prior to the deposition of ultrablack films, which effectively prevented corrosion of magnesium caused by Al3+ and Cl− by-products in the TiAlC film. With the presence of this interlayer, the ultrablack film on the surface of the magnesium alloy exhibited good adhesion and abrasion resistance. Furthermore, after undergoing damp heat and thermal cycling tests, the absorptions of the ultrablack film-coated magnesium alloys remained at 99.1% and 99.0%, respectively, which indicated that the film is promising for application in precision optics under harsh environmental conditions.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"34 S15","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140251047","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}
D. Silva-Quinones, John R. Mason, Robert Norden, A. Teplyakov
As the size of the components in electronic devices decreases, new approaches and chemical modification schemes are needed to produce nanometer-size features with bottom-up manufacturing. Organic monolayers can be used as effective resists to block the growth of materials on non-growth substrates in area-selective deposition methods. However, choosing the appropriate surface modification requires knowledge of the corresponding chemistry and also a detailed investigation of the behavior of the functionalized surface in realistic deposition schemes. This study aims to investigate the chemistry of boronic acids that can be used to prepare such non-growth areas on elemental semiconductors. 4-Fluorophenylboronic acid is used as a model to investigate the possibility to utilize the Si(100) surface functionalized with this compound as a non-growth substrate in a titanium dioxide (TiO2) deposition scheme based on sequential doses of tetrakis(dimethylamido)titanium and water. A combination of X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry allows for a better understanding of the process. The resulting surface is shown to be an effective non-growth area to TiO2 deposition when compared to currently used H-terminated silicon surfaces but to exhibit much higher stability in ambient conditions.
随着电子设备中元件尺寸的减小，需要采用新的方法和化学修饰方案，以自下而上的制造方式生产纳米尺寸的特征。在区域选择性沉积方法中，有机单层可以作为有效的抗蚀剂，阻止材料在非生长基底上生长。然而，选择合适的表面修饰需要了解相应的化学知识，还需要详细研究功能化表面在实际沉积方案中的行为。本研究旨在研究硼酸的化学性质，以便在元素半导体上制备这种非生长区域。本研究以 4-氟苯基硼酸为模型，探讨了在基于四（二甲基氨基）钛和水的连续剂量沉积方案中，利用该化合物功能化的 Si（100）表面作为非生长基底的可能性。结合使用 X 射线光电子能谱和飞行时间二次离子质谱法，可以更好地了解这一过程。结果表明，与目前使用的 H 端硅表面相比，TiO2 沉积表面是一个有效的非生长区，但在环境条件下却表现出更高的稳定性。
{"title":"Inhibition of atomic layer deposition of TiO2 by functionalizing silicon surface with 4-fluorophenylboronic acid","authors":"D. Silva-Quinones, John R. Mason, Robert Norden, A. Teplyakov","doi":"10.1116/6.0003316","DOIUrl":"https://doi.org/10.1116/6.0003316","url":null,"abstract":"As the size of the components in electronic devices decreases, new approaches and chemical modification schemes are needed to produce nanometer-size features with bottom-up manufacturing. Organic monolayers can be used as effective resists to block the growth of materials on non-growth substrates in area-selective deposition methods. However, choosing the appropriate surface modification requires knowledge of the corresponding chemistry and also a detailed investigation of the behavior of the functionalized surface in realistic deposition schemes. This study aims to investigate the chemistry of boronic acids that can be used to prepare such non-growth areas on elemental semiconductors. 4-Fluorophenylboronic acid is used as a model to investigate the possibility to utilize the Si(100) surface functionalized with this compound as a non-growth substrate in a titanium dioxide (TiO2) deposition scheme based on sequential doses of tetrakis(dimethylamido)titanium and water. A combination of X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry allows for a better understanding of the process. The resulting surface is shown to be an effective non-growth area to TiO2 deposition when compared to currently used H-terminated silicon surfaces but to exhibit much higher stability in ambient conditions.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"20 12","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140254261","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}
Niobium oxide films find various applications, such as antireflective optical layers, gas sensors, and solar cells. They also show promise for emerging applications such as electrochromic and photocatalytic devices. In order to optimize the deposition of niobium oxide films by RF reactive sputtering, a detailed investigation of the plasma parameters was performed. A pure metallic target and a mixture of Ar and O2 in different proportions were used in the experiments. The deposition power was varied between 120 and 260 W, while the total pressure was kept at 0.67 Pa throughout. Deposition rates, discharge self-bias voltage, and plasma optical emissions were monitored and analyzed. Additionally, computer simulations of the process utilizing existing models were conducted and a comparative analysis with the experimental results was performed. The main findings include mapping the deposition conditions as functions of oxygen flow rate. The flow ranges in which the deposition regime changes from metallic to oxygen contaminated target conditions were identified. The narrow O2 flow range associated with the regime changes was characterized by significant changes in the self-bias voltages and plasma emissions from oxygen, argon, and niobium. The observations evidence the importance of the detailed analysis of the deposition process to get the desired stoichiometry and optimized film properties.
氧化铌薄膜有多种应用，如抗反射光学层、气体传感器和太阳能电池。它们在电致变色和光催化设备等新兴应用领域也大有可为。为了优化通过射频反应溅射沉积氧化铌薄膜，我们对等离子体参数进行了详细研究。实验中使用了纯金属靶以及不同比例的氩气和氧气混合物。沉积功率在 120 到 260 W 之间变化，总压力始终保持在 0.67 Pa。对沉积速率、放电自偏压和等离子体光学发射进行了监测和分析。此外，还利用现有模型对过程进行了计算机模拟，并与实验结果进行了对比分析。主要发现包括绘制了沉积条件与氧气流速的函数关系图。确定了沉积机制从金属到氧气污染目标条件变化的流量范围。在与制度变化相关的狭窄氧气流量范围内，氧、氩和铌的自偏置电压和等离子体发射发生了显著变化。这些观察结果证明了对沉积过程进行详细分析以获得理想的化学计量和优化的薄膜特性的重要性。
{"title":"Deposition rate and optical emissions in niobium oxide processes by reactive sputtering","authors":"João Saccoman, N. F. A. Neto, José H. D. da Silva","doi":"10.1116/6.0003255","DOIUrl":"https://doi.org/10.1116/6.0003255","url":null,"abstract":"Niobium oxide films find various applications, such as antireflective optical layers, gas sensors, and solar cells. They also show promise for emerging applications such as electrochromic and photocatalytic devices. In order to optimize the deposition of niobium oxide films by RF reactive sputtering, a detailed investigation of the plasma parameters was performed. A pure metallic target and a mixture of Ar and O2 in different proportions were used in the experiments. The deposition power was varied between 120 and 260 W, while the total pressure was kept at 0.67 Pa throughout. Deposition rates, discharge self-bias voltage, and plasma optical emissions were monitored and analyzed. Additionally, computer simulations of the process utilizing existing models were conducted and a comparative analysis with the experimental results was performed. The main findings include mapping the deposition conditions as functions of oxygen flow rate. The flow ranges in which the deposition regime changes from metallic to oxygen contaminated target conditions were identified. The narrow O2 flow range associated with the regime changes was characterized by significant changes in the self-bias voltages and plasma emissions from oxygen, argon, and niobium. The observations evidence the importance of the detailed analysis of the deposition process to get the desired stoichiometry and optimized film properties.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"110 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140251751","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. Likith, Geoff L. Brennecka, Cristian V. Ciobanu
Transition metal dichalcogenides (TMDC) are currently drawing significant interest from the scientific community as 2D materials that have intrinsically semiconducting bandgaps. One additional advantage of TMDCs for discovering and developing materials with novel electronic, electromechanical, or optoelectronic properties is that both layer composition and registry can be readily tailored. To understand how such tailoring can expand the range of properties, here we used density functional theory calculations to determine the electronic structure and piezoelectric properties of bilayer TMDC heterostructures based on MoX2 and WX2, where X can be S, Se, or Te. For identical layers with no misorientation with respect to one another, we find that the registry of the two layers can change the bandgap type (direct vs indirect), as well as its value (by ≈0.25 eV). We report similar conclusions for bilayer heterostructures in which the composition of the two layers is different. Interlayer registry also has a pronounced effect on piezoelectric properties as the piezoelectric coefficients of the two layers either nearly cancel each other or add up to yield enhanced values for the associated TMDC bilayer heterostructures. These results may serve as a guide for enhancing electronic and piezoelectric properties by stacking TMDC layers.
{"title":"Interlayer registry effects on the electronic and piezoelectric properties of transition metal dichalcogenide bilayers","authors":"S. Likith, Geoff L. Brennecka, Cristian V. Ciobanu","doi":"10.1116/6.0003264","DOIUrl":"https://doi.org/10.1116/6.0003264","url":null,"abstract":"Transition metal dichalcogenides (TMDC) are currently drawing significant interest from the scientific community as 2D materials that have intrinsically semiconducting bandgaps. One additional advantage of TMDCs for discovering and developing materials with novel electronic, electromechanical, or optoelectronic properties is that both layer composition and registry can be readily tailored. To understand how such tailoring can expand the range of properties, here we used density functional theory calculations to determine the electronic structure and piezoelectric properties of bilayer TMDC heterostructures based on MoX2 and WX2, where X can be S, Se, or Te. For identical layers with no misorientation with respect to one another, we find that the registry of the two layers can change the bandgap type (direct vs indirect), as well as its value (by ≈0.25 eV). We report similar conclusions for bilayer heterostructures in which the composition of the two layers is different. Interlayer registry also has a pronounced effect on piezoelectric properties as the piezoelectric coefficients of the two layers either nearly cancel each other or add up to yield enhanced values for the associated TMDC bilayer heterostructures. These results may serve as a guide for enhancing electronic and piezoelectric properties by stacking TMDC layers.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"37 14","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140259501","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 explores the electrochemical anodization of tantalum surfaces to create nanostructured substrates for the deposition of Zn-ZnO nanoparticles (NPs) through magnetron sputtering. The anodization process, conducted at different potentials (25 V and 50 V), resulted in tantalum surfaces with distinct dimple structures. The formation of these nano-level dimples is attributed to the dynamic equilibrium between the continuous formation and dissolution of the anodic TaOx layer. The dimple diameter is observed to increase with applied potential, correlating with the dissolution rate of the anodic oxide. The NP deposition parameters were studied in two steps. First, the effect of the deposition conditions on the nanoparticle size and distribution was evaluated and optimized on silicon substrates. Second, the conditions that resulted in the optimum size and distribution of the nanoparticles were utilized in tantalum substrates and evaluated to which extent these conditions were reproduced onto the anodized Ta substrate. Comparisons of Zn-ZnO nanoparticle depositions on silicon and tantalum substrates reveal similar island growth trends, with differences in nanoparticle size and distribution attributed to substrate properties. Further investigation involves anodized tantalum substrates with varying dimple sizes, and deposition conditions are adjusted with bias voltage, pressure, and deposition time to control nanoparticle characteristics. Characterization of the Zn-ZnO nanoparticles deposited on anodized tantalum surfaces is performed using scanning electron microscopy, high-angle annular dark-field scanning transmission electron microscopy, and energy-dispersive x-ray spectroscopy. The resulting core-shell structures are confirmed through structural analysis, revealing a core of hexagonal close-packed Zn and a shell of ZnO. The study demonstrates the influence of substrate properties and deposition conditions on the morphology and composition of Zn-ZnO nanoparticles, providing insights for applications in nanoelectronics and catalysis.
本研究探讨了对钽表面进行电化学阳极氧化处理，以创建纳米结构基底，从而通过磁控溅射沉积 Zn-ZnO 纳米粒子 (NPs)。在不同的电位（25 V 和 50 V）下进行的阳极氧化过程使钽表面形成了明显的凹陷结构。这些纳米级凹陷的形成归因于阳极 TaOx 层的持续形成和溶解之间的动态平衡。据观察，酒窝直径随施加电位的增加而增大，这与阳极氧化物的溶解速率有关。对 NP 沉积参数的研究分为两个步骤。首先，在硅基底上评估并优化了沉积条件对纳米粒子尺寸和分布的影响。其次，在钽基底上使用了能使纳米粒子达到最佳尺寸和分布的条件，并评估了这些条件在阳极氧化钽基底上的再现程度。对硅基底和钽基底上的氧化锌纳米粒子沉积进行比较后发现，纳米岛的生长趋势相似，纳米粒子尺寸和分布的差异归因于基底特性。进一步的研究涉及具有不同凹痕尺寸的阳极氧化钽基底，并通过调整偏置电压、压力和沉积时间来控制纳米粒子的特性。使用扫描电子显微镜、高角度环形暗场扫描透射电子显微镜和能量色散 X 射线光谱对沉积在阳极氧化钽表面的 Zn-ZnO 纳米粒子进行了表征。通过结构分析确认了由此产生的核壳结构，揭示了六方紧密堆积的锌核和氧化锌壳。该研究证明了基底特性和沉积条件对 Zn-ZnO 纳米粒子形态和组成的影响，为纳米电子学和催化应用提供了启示。
{"title":"Electrochemically structured tantalum surfaces via anodization for core-shell nanostructures: Optimization and characterization of Zn-ZnO nanoparticle deposition using magnetron sputtering","authors":"Levent Kara, S. Calderon, S. Carvalho","doi":"10.1116/6.0003266","DOIUrl":"https://doi.org/10.1116/6.0003266","url":null,"abstract":"This study explores the electrochemical anodization of tantalum surfaces to create nanostructured substrates for the deposition of Zn-ZnO nanoparticles (NPs) through magnetron sputtering. The anodization process, conducted at different potentials (25 V and 50 V), resulted in tantalum surfaces with distinct dimple structures. The formation of these nano-level dimples is attributed to the dynamic equilibrium between the continuous formation and dissolution of the anodic TaOx layer. The dimple diameter is observed to increase with applied potential, correlating with the dissolution rate of the anodic oxide. The NP deposition parameters were studied in two steps. First, the effect of the deposition conditions on the nanoparticle size and distribution was evaluated and optimized on silicon substrates. Second, the conditions that resulted in the optimum size and distribution of the nanoparticles were utilized in tantalum substrates and evaluated to which extent these conditions were reproduced onto the anodized Ta substrate. Comparisons of Zn-ZnO nanoparticle depositions on silicon and tantalum substrates reveal similar island growth trends, with differences in nanoparticle size and distribution attributed to substrate properties. Further investigation involves anodized tantalum substrates with varying dimple sizes, and deposition conditions are adjusted with bias voltage, pressure, and deposition time to control nanoparticle characteristics. Characterization of the Zn-ZnO nanoparticles deposited on anodized tantalum surfaces is performed using scanning electron microscopy, high-angle annular dark-field scanning transmission electron microscopy, and energy-dispersive x-ray spectroscopy. The resulting core-shell structures are confirmed through structural analysis, revealing a core of hexagonal close-packed Zn and a shell of ZnO. The study demonstrates the influence of substrate properties and deposition conditions on the morphology and composition of Zn-ZnO nanoparticles, providing insights for applications in nanoelectronics and catalysis.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"80 9","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140077326","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}
Partha Mukhopadhyay, Ivan Fletcher, Zuriel Caribe Couvertier, Brent Schwab, John Gumpher, W. Schoenfeld, Jon Kretzschmar, Anton deVilliers, Jim Fulford
A highly uniform aluminum nitride thin film has been developed by thermal atomic layer deposition (ALD), which is designed to handle high volume of 200 mm wafers. A three-sigma thickness variation of <0.5 Å resulted from repeatable batch depositions of over 500 Å, while wafer-within-wafer (WinW) and wafer-to-wafer (WtoW) remained <5% by the optimized recipe in a 100+ wafer reactor. Various ALD deposition temperatures, film thicknesses, and substrate types of Si, quartz, and GaN/Si(111) templates have been examined for material and optical properties of an AlN film. A narrow temperature window of 300–350 °C was identified as the most suitable for the deposition process with 350 °C as the optimized one. Substrate-inhibited growth and nonlinearity in deposition rate have been observed for AlN which is possibly related to the available reaction sites at the time of nucleation on foreign substrate surfaces. A special set of experiments with a thorough exploration of XPS individual peaks such as Al2p, N1s, C1s, and O1s reveals negligible carbon and oxygen contamination with cent-percent Al–N bonding. An amorphous AlN film is evident on Si by cross-sectional TEM while a trace of polycrystalline film on GaN templates with smooth heterointerfaces to AlGaN/GaN structures. The optical bandgap is estimated to be 5.8 eV from the transmittance experiment. An in-depth refractive-index investigation shows high-density AlN by TEL Alpha-8SEiTM batch ALD which also exhibits excellent uniformity over composition and thickness with run-to-run (RtoR), WtoW, and WinW uniformity under 0.5%, highlighting the reliability and precision of the process while having high throughput.
{"title":"Nucleation of highly uniform AlN thin films by high volume batch ALD on 200 mm platform","authors":"Partha Mukhopadhyay, Ivan Fletcher, Zuriel Caribe Couvertier, Brent Schwab, John Gumpher, W. Schoenfeld, Jon Kretzschmar, Anton deVilliers, Jim Fulford","doi":"10.1116/6.0003405","DOIUrl":"https://doi.org/10.1116/6.0003405","url":null,"abstract":"A highly uniform aluminum nitride thin film has been developed by thermal atomic layer deposition (ALD), which is designed to handle high volume of 200 mm wafers. A three-sigma thickness variation of <0.5 Å resulted from repeatable batch depositions of over 500 Å, while wafer-within-wafer (WinW) and wafer-to-wafer (WtoW) remained <5% by the optimized recipe in a 100+ wafer reactor. Various ALD deposition temperatures, film thicknesses, and substrate types of Si, quartz, and GaN/Si(111) templates have been examined for material and optical properties of an AlN film. A narrow temperature window of 300–350 °C was identified as the most suitable for the deposition process with 350 °C as the optimized one. Substrate-inhibited growth and nonlinearity in deposition rate have been observed for AlN which is possibly related to the available reaction sites at the time of nucleation on foreign substrate surfaces. A special set of experiments with a thorough exploration of XPS individual peaks such as Al2p, N1s, C1s, and O1s reveals negligible carbon and oxygen contamination with cent-percent Al–N bonding. An amorphous AlN film is evident on Si by cross-sectional TEM while a trace of polycrystalline film on GaN templates with smooth heterointerfaces to AlGaN/GaN structures. The optical bandgap is estimated to be 5.8 eV from the transmittance experiment. An in-depth refractive-index investigation shows high-density AlN by TEL Alpha-8SEiTM batch ALD which also exhibits excellent uniformity over composition and thickness with run-to-run (RtoR), WtoW, and WinW uniformity under 0.5%, highlighting the reliability and precision of the process while having high throughput.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"142 34","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140078280","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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