Hyunik Park, Y. Choi, S. Yang, Jinho Bae, Jihyun Kim
β-Ga2O3, an emerging ultrawide bandgap (UWBG) semiconductor, offers promising properties for next-generation power electronics, chemical sensors, and solar-blind optoelectronics. Scaling down of β-Ga2O3 to the atomic level affords the advantages of two-dimensional (2D) materials, while maintaining the inherent properties of the parent bulk counterpart. Here, we demonstrate a simple approach to synthesize ultrathin millimeter-size β-Ga2O3 sheets using a liquid gallium squeezing technique. The GaOx nanolayer produced by stamping liquid gallium under the Cabrera–Mott oxidation was converted into few-atom-thick β-Ga2O3 via thermal annealing under atmospheric conditions. This approach was also applied to various substrates such as SiO2, Si, graphene, quartz, and sapphire to heteroepitaxially synthesize 2D β-Ga2O3 on a target substrate. Finally, we propose a patterning strategy combining the squeezing technique with conventional lithography to obtain a β-Ga2O3 layer with a controllable thickness and shape. Our synthetic method has the potential to overcome the limitations of conventional β-Ga2O3 growth methods, paving a path for applications in UWBG-based (opto-)electronics with a high throughput in a cost-effective manner.
{"title":"Large-scale synthesis of atomically thin ultrawide bandgap β-Ga2O3 using a liquid gallium squeezing technique","authors":"Hyunik Park, Y. Choi, S. Yang, Jinho Bae, Jihyun Kim","doi":"10.1116/6.0000927","DOIUrl":"https://doi.org/10.1116/6.0000927","url":null,"abstract":"β-Ga2O3, an emerging ultrawide bandgap (UWBG) semiconductor, offers promising properties for next-generation power electronics, chemical sensors, and solar-blind optoelectronics. Scaling down of β-Ga2O3 to the atomic level affords the advantages of two-dimensional (2D) materials, while maintaining the inherent properties of the parent bulk counterpart. Here, we demonstrate a simple approach to synthesize ultrathin millimeter-size β-Ga2O3 sheets using a liquid gallium squeezing technique. The GaOx nanolayer produced by stamping liquid gallium under the Cabrera–Mott oxidation was converted into few-atom-thick β-Ga2O3 via thermal annealing under atmospheric conditions. This approach was also applied to various substrates such as SiO2, Si, graphene, quartz, and sapphire to heteroepitaxially synthesize 2D β-Ga2O3 on a target substrate. Finally, we propose a patterning strategy combining the squeezing technique with conventional lithography to obtain a β-Ga2O3 layer with a controllable thickness and shape. Our synthetic method has the potential to overcome the limitations of conventional β-Ga2O3 growth methods, paving a path for applications in UWBG-based (opto-)electronics with a high throughput in a cost-effective manner.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":"94 1","pages":"033409"},"PeriodicalIF":0.0,"publicationDate":"2021-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85598174","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. Nikolskaya, E. Okulich, D. Korolev, A. Stepanov, D. Nikolichev, A. Mikhaylov, D. Tetelbaum, A. Almaev, C. A. Bolzan, A. Buaczik, R. Giulian, P. L. Grande, Ashok Kumar, Mahesh Kumar, D. Gogova
Gallium oxide, and in particular its thermodynamically stable β-Ga2O3 phase, is within the most exciting materials in research and technology nowadays due to its unique properties. The very high breakdown electric field and the figure of merit rivaled only by diamond have tremendous potential for the next generation “green” electronics enabling efficient distribution, use, and conversion of electrical energy. Ion implantation is a traditional technological method used in these fields, and its well-known advantages can contribute greatly to the rapid development of physics and technology of Ga2O3-based materials and devices. Here, the status of ion implantation in β-Ga2O3 nowadays is reviewed. Attention is mainly paid to the results of experimental study of damage under ion irradiation and the properties of Ga2O3 layers doped by ion implantation. The results of ab initio theoretical calculations of the impurities and defect parameters are briefly presented, and the physical principles of a number of analytical methods used to study implanted gallium oxide layers are highlighted. The use of ion implantation in the development of Ga2O3-based devices, such as metal oxide field-effect transistors, Schottky barrier diodes, and solar-blind UV detectors, is described together with systematical analysis of the achieved values of their characteristics. Finally, the most important challenges to be overcome in this field of science and technology are discussed.
{"title":"Ion implantation in β-Ga2O3: Physics and technology","authors":"A. Nikolskaya, E. Okulich, D. Korolev, A. Stepanov, D. Nikolichev, A. Mikhaylov, D. Tetelbaum, A. Almaev, C. A. Bolzan, A. Buaczik, R. Giulian, P. L. Grande, Ashok Kumar, Mahesh Kumar, D. Gogova","doi":"10.1116/6.0000928","DOIUrl":"https://doi.org/10.1116/6.0000928","url":null,"abstract":"Gallium oxide, and in particular its thermodynamically stable β-Ga2O3 phase, is within the most exciting materials in research and technology nowadays due to its unique properties. The very high breakdown electric field and the figure of merit rivaled only by diamond have tremendous potential for the next generation “green” electronics enabling efficient distribution, use, and conversion of electrical energy. Ion implantation is a traditional technological method used in these fields, and its well-known advantages can contribute greatly to the rapid development of physics and technology of Ga2O3-based materials and devices. Here, the status of ion implantation in β-Ga2O3 nowadays is reviewed. Attention is mainly paid to the results of experimental study of damage under ion irradiation and the properties of Ga2O3 layers doped by ion implantation. The results of ab initio theoretical calculations of the impurities and defect parameters are briefly presented, and the physical principles of a number of analytical methods used to study implanted gallium oxide layers are highlighted. The use of ion implantation in the development of Ga2O3-based devices, such as metal oxide field-effect transistors, Schottky barrier diodes, and solar-blind UV detectors, is described together with systematical analysis of the achieved values of their characteristics. Finally, the most important challenges to be overcome in this field of science and technology are discussed.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":"40 3 1","pages":"030802"},"PeriodicalIF":0.0,"publicationDate":"2021-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91350908","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}
Moustapha Jaffal, Taguhi Yeghoyan, G. Lefévre, R. Gassilloud, N. Possémé, C. Vallée, M. Bonvalot
In this work, we focus on the development of topographically selective deposition (TSD) leading to local deposition on the vertical sidewalls of 3D structures. A proof of concept is provided for the TSD of Ta2O5. The TSD process relies on plasma-enhanced atomic layer deposition (PEALD) alternating with quasi-atomic layer etching (ALE). Quasi-ALE involves a fluorination treatment followed by a directional Ar+ sputtering step. We show that the fluorination treatment allows a significant decrease in the incident kinetic energy of the subsequent directional Ar+ sputtering step. Conversely, when no fluorination step is carried out, TSD requires high incident kinetic energies during the directional Ar+ sputtering step, which, in turn, leads to detrimental plasma-induced damage on horizontal surfaces, such as roughness, also promoting by-product redeposition. The benefits and shortcomings of these two TSD approaches—PEALD/quasi-ALE and PEALD/energetic Ar+ sputtering—are compared in light of potential bottom-up technological developments.
{"title":"Topographical selective deposition: A comparison between plasma-enhanced atomic layer deposition/sputtering and plasma-enhanced atomic layer deposition/quasi-atomic layer etching approaches","authors":"Moustapha Jaffal, Taguhi Yeghoyan, G. Lefévre, R. Gassilloud, N. Possémé, C. Vallée, M. Bonvalot","doi":"10.1116/6.0000969","DOIUrl":"https://doi.org/10.1116/6.0000969","url":null,"abstract":"In this work, we focus on the development of topographically selective deposition (TSD) leading to local deposition on the vertical sidewalls of 3D structures. A proof of concept is provided for the TSD of Ta2O5. The TSD process relies on plasma-enhanced atomic layer deposition (PEALD) alternating with quasi-atomic layer etching (ALE). Quasi-ALE involves a fluorination treatment followed by a directional Ar+ sputtering step. We show that the fluorination treatment allows a significant decrease in the incident kinetic energy of the subsequent directional Ar+ sputtering step. Conversely, when no fluorination step is carried out, TSD requires high incident kinetic energies during the directional Ar+ sputtering step, which, in turn, leads to detrimental plasma-induced damage on horizontal surfaces, such as roughness, also promoting by-product redeposition. The benefits and shortcomings of these two TSD approaches—PEALD/quasi-ALE and PEALD/energetic Ar+ sputtering—are compared in light of potential bottom-up technological developments.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":"25 1","pages":"030402"},"PeriodicalIF":0.0,"publicationDate":"2021-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90441701","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}
Sapphire and gallium oxide have been used as substrates for most of the reported results on β-Ga2O3 devices. However, silicon (Si) is an abundant material on the Earth, leading to easier and low-cost availability of this substrate, along with higher thermal conductivity, which makes Si a promising and potential substrate candidate for rapid commercialization. Therefore, in order to strengthen the feasibility of Ga2O3 on Si integration technology, we have deposited β-Ga2O3 on (100) and (111) oriented p-Si substrates using a pulsed laser deposition technique. A single-phase (β) and polycrystalline nature of the β-Ga2O3 film is observed for both samples using x-ray diffraction. A low root mean square roughness of 3.62 nm has been measured for Ga2O3/Si(100), as compared to 5.43 nm of Ga2O3/Si(111) using atomic force microscope. Moreover, Ga2O3/Si(100) shows a smoother and uniform surface of the Ga2O3 film, whereas Ga2O3/Si(111) seems to have a rougher surface with pitlike defects. This might be due to the hexagonal projection of Si (111) that is not suitable for obtaining a good tilted cuboid or monoclinic Ga2O3 crystal unlike the rectangle projection of Si (100). The electrical parameters of the fabricated Schottky barrier diodes were extracted using current–voltage (I–V) and capacitance–voltage (C–V) characteristics. The polycrystalline Ga2O3 film on Si(100) leads to fewer defects emerging from the Ga2O3/Si heterointerface due to the close symmetry of Ga2O3 and the Si(100) crystal with rectangle projections unlike Ga2O3 on Si(111). These fewer defects eventually lead to a better diode performance of Ga2O3/Si(100) where we have observed typical thermionic dominating carrier transport, whereas defect-assisted thermionic field emission has been the primary carrier transport mechanism in Ga2O3/Si(111). Hence, the Si (100) substrate is demonstrated to be a better and potential platform for Ga2O3 devices than Si (111).
{"title":"Substrate orientation dependent current transport mechanisms in β-Ga2O3/Si based Schottky barrier diodes","authors":"M. Yadav, A. Mondal, S. Sharma, A. Bag","doi":"10.1116/6.0000858","DOIUrl":"https://doi.org/10.1116/6.0000858","url":null,"abstract":"Sapphire and gallium oxide have been used as substrates for most of the reported results on β-Ga2O3 devices. However, silicon (Si) is an abundant material on the Earth, leading to easier and low-cost availability of this substrate, along with higher thermal conductivity, which makes Si a promising and potential substrate candidate for rapid commercialization. Therefore, in order to strengthen the feasibility of Ga2O3 on Si integration technology, we have deposited β-Ga2O3 on (100) and (111) oriented p-Si substrates using a pulsed laser deposition technique. A single-phase (β) and polycrystalline nature of the β-Ga2O3 film is observed for both samples using x-ray diffraction. A low root mean square roughness of 3.62 nm has been measured for Ga2O3/Si(100), as compared to 5.43 nm of Ga2O3/Si(111) using atomic force microscope. Moreover, Ga2O3/Si(100) shows a smoother and uniform surface of the Ga2O3 film, whereas Ga2O3/Si(111) seems to have a rougher surface with pitlike defects. This might be due to the hexagonal projection of Si (111) that is not suitable for obtaining a good tilted cuboid or monoclinic Ga2O3 crystal unlike the rectangle projection of Si (100). The electrical parameters of the fabricated Schottky barrier diodes were extracted using current–voltage (I–V) and capacitance–voltage (C–V) characteristics. The polycrystalline Ga2O3 film on Si(100) leads to fewer defects emerging from the Ga2O3/Si heterointerface due to the close symmetry of Ga2O3 and the Si(100) crystal with rectangle projections unlike Ga2O3 on Si(111). These fewer defects eventually lead to a better diode performance of Ga2O3/Si(100) where we have observed typical thermionic dominating carrier transport, whereas defect-assisted thermionic field emission has been the primary carrier transport mechanism in Ga2O3/Si(111). Hence, the Si (100) substrate is demonstrated to be a better and potential platform for Ga2O3 devices than Si (111).","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":"33 1","pages":"033203"},"PeriodicalIF":0.0,"publicationDate":"2021-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82713689","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}
The epitaxial growth of tin in an alpha phase (α-Sn) is desired for its topological properties. In this study, we have successfully grown a series of α-Sn films on CdTe (001) substrates by molecular beam epitaxy with different thicknesses. A (2 × 1) surface reconstruction of CdTe is obtained due to efficient cleaning by atomic hydrogen, which favors the α-Sn growth. The high quality of the α-Sn films has been confirmed by x-ray diffraction, atomic force microscopy, etc. Thickness and temperature-dependent electrical transport properties have been studied. All the samples show a p-type transport at room temperature, but transitions in transport type are observed at lower temperatures. These transport behaviors can be well explained by a three-band model, and a phase diagram illustrating the transport behaviors in α-Sn is presented.
{"title":"Multiple carrier transport in high-quality α-Sn films grown on CdTe (001) by molecular beam epitaxy","authors":"Yuanfeng Ding, Jinshan Yao, Ziyuan Yuan, Chen Li, Ming-Hui Lu, Hong Lu, Yan-Feng Chen","doi":"10.1116/6.0000756","DOIUrl":"https://doi.org/10.1116/6.0000756","url":null,"abstract":"The epitaxial growth of tin in an alpha phase (α-Sn) is desired for its topological properties. In this study, we have successfully grown a series of α-Sn films on CdTe (001) substrates by molecular beam epitaxy with different thicknesses. A (2 × 1) surface reconstruction of CdTe is obtained due to efficient cleaning by atomic hydrogen, which favors the α-Sn growth. The high quality of the α-Sn films has been confirmed by x-ray diffraction, atomic force microscopy, etc. Thickness and temperature-dependent electrical transport properties have been studied. All the samples show a p-type transport at room temperature, but transitions in transport type are observed at lower temperatures. These transport behaviors can be well explained by a three-band model, and a phase diagram illustrating the transport behaviors in α-Sn is presented.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":"48 2","pages":"033408"},"PeriodicalIF":0.0,"publicationDate":"2021-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91481176","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}
Romel Hidayat, Hye-Lee Kim, Hohoon Kim, Y. Byun, Jongsoo Lee, Won-Jun Lee
We studied heteroleptic Hf precursors with a linked amido-cyclopentadienyl ligand by density functional theory (DFT) calculation to enable high-temperature atomic layer deposition processes. The thermolysis and hydrolysis of Hf precursors were simulated to expect thermal stability and reactivity with hydroxyl groups. The effects of alkyl groups in the precursors were also investigated. We constructed the hydroxylated HfO2 surface and then simulated the surface reactions of the precursors. The precursors with the linked ligand showed higher activation energies for thermolysis and lower activation energies for hydrolysis as compared with CpHf(NMe2)3. The precursors with the linked ligand also showed low activation energies for the serial ligand exchange reactions on the HfO2 surface, significantly lower than those of CpHf(NMe2)3. Therefore, the DFT calculation suggests that the Hf precursors with the linked ligand are promising due to their thermal stability and reactivity better than CpHf(NMe2)3.
{"title":"Surface reaction of the hafnium precursor with a linked amido-cyclopentadienyl ligand: A density functional theory study","authors":"Romel Hidayat, Hye-Lee Kim, Hohoon Kim, Y. Byun, Jongsoo Lee, Won-Jun Lee","doi":"10.1116/6.0000796","DOIUrl":"https://doi.org/10.1116/6.0000796","url":null,"abstract":"We studied heteroleptic Hf precursors with a linked amido-cyclopentadienyl ligand by density functional theory (DFT) calculation to enable high-temperature atomic layer deposition processes. The thermolysis and hydrolysis of Hf precursors were simulated to expect thermal stability and reactivity with hydroxyl groups. The effects of alkyl groups in the precursors were also investigated. We constructed the hydroxylated HfO2 surface and then simulated the surface reactions of the precursors. The precursors with the linked ligand showed higher activation energies for thermolysis and lower activation energies for hydrolysis as compared with CpHf(NMe2)3. The precursors with the linked ligand also showed low activation energies for the serial ligand exchange reactions on the HfO2 surface, significantly lower than those of CpHf(NMe2)3. Therefore, the DFT calculation suggests that the Hf precursors with the linked ligand are promising due to their thermal stability and reactivity better than CpHf(NMe2)3.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":"51 1","pages":"032410"},"PeriodicalIF":0.0,"publicationDate":"2021-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86681119","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}
Matthew B. E. Griffiths, D. Zanders, Michael A. Land, Jason D. Masuda, A. Devi, S. Barry
Eight new atomic layer deposition (ALD) precursors were synthesized using a ligand that is new to the field of ALD: (tBuNH)SiMe2NMe2. Complexes containing Mg, V, Mn, Fe, Co, Ni, and Zn were found to be tetrahedral, and Li complexes form more complex structures. These compounds performed exceptionally well by thermogravimetric analysis (TGA). All compounds except for one Li species and the Fe complex left residual masses below 5%, similar or better than the analogous amidinate complexes. In particular, the Co(II) complex is very thermally robust and performs very well during a TGA stress test, surpassing temperatures above 200 °C. These compounds are the first of a family of precursors containing this type of monoanionic N–Si–N ligand and are prime candidates for ALD process development.
{"title":"(tBuN)SiMe2NMe2—A new N,N′-κ2-monoanionic ligand for atomic layer deposition precursors","authors":"Matthew B. E. Griffiths, D. Zanders, Michael A. Land, Jason D. Masuda, A. Devi, S. Barry","doi":"10.1116/6.0000795","DOIUrl":"https://doi.org/10.1116/6.0000795","url":null,"abstract":"Eight new atomic layer deposition (ALD) precursors were synthesized using a ligand that is new to the field of ALD: (tBuNH)SiMe2NMe2. Complexes containing Mg, V, Mn, Fe, Co, Ni, and Zn were found to be tetrahedral, and Li complexes form more complex structures. These compounds performed exceptionally well by thermogravimetric analysis (TGA). All compounds except for one Li species and the Fe complex left residual masses below 5%, similar or better than the analogous amidinate complexes. In particular, the Co(II) complex is very thermally robust and performs very well during a TGA stress test, surpassing temperatures above 200 °C. These compounds are the first of a family of precursors containing this type of monoanionic N–Si–N ligand and are prime candidates for ALD process development.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":"55 1","pages":"032409"},"PeriodicalIF":0.0,"publicationDate":"2021-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76487135","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}
C. Bundesmann, J. Bauer, A. Finzel, J. Gerlach, W. Knolle, A. Hellmich, R. Synowicki
Indium tin oxide (ITO) thin films were grown by Ar ion beam sputter deposition under systematic variation of ion energy, geometrical parameters, and O 2 background pressure and characterized with regard to the film thickness, growth rate, crystalline structure, surface roughness, mass density, composition, electrical, and optical properties. The growth rate shows an over-cosine, forward-tilted angular distribution with a maximum, which increases with increasing ion energy, increasing ion incidence angle, and decreasing O 2 background pressure. ITO films were found to be amorphous with a surface roughness of less than 1 nm. Mass density and composition show only small changes with increasing scattering angle. The electrical resistivity behavior in dependence on the process parameters is complex. It is not only driven by the O 2 background pressure but also very much by the scattering angle. The observed behavior can be understood only if competing processes are considered: (i) reduction of the number of oxygen vacancies due to the presence of O 2 background gas and (ii) defect generation and preferential sputtering of oxygen at the surface of the growing films due to the impact of high-energy scattered particles. Even though absolute numbers differ, optical characterization suggests a similar systematics.
{"title":"Properties of indium tin oxide thin films grown by Ar ion beam sputter deposition","authors":"C. Bundesmann, J. Bauer, A. Finzel, J. Gerlach, W. Knolle, A. Hellmich, R. Synowicki","doi":"10.1116/6.0000917","DOIUrl":"https://doi.org/10.1116/6.0000917","url":null,"abstract":"Indium tin oxide (ITO) thin films were grown by Ar ion beam sputter deposition under systematic variation of ion energy, geometrical parameters, and O 2 background pressure and characterized with regard to the film thickness, growth rate, crystalline structure, surface roughness, mass density, composition, electrical, and optical properties. The growth rate shows an over-cosine, forward-tilted angular distribution with a maximum, which increases with increasing ion energy, increasing ion incidence angle, and decreasing O 2 background pressure. ITO films were found to be amorphous with a surface roughness of less than 1 nm. Mass density and composition show only small changes with increasing scattering angle. The electrical resistivity behavior in dependence on the process parameters is complex. It is not only driven by the O 2 background pressure but also very much by the scattering angle. The observed behavior can be understood only if competing processes are considered: (i) reduction of the number of oxygen vacancies due to the presence of O 2 background gas and (ii) defect generation and preferential sputtering of oxygen at the surface of the growing films due to the impact of high-energy scattered particles. Even though absolute numbers differ, optical characterization suggests a similar systematics.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":"07 1","pages":"033406"},"PeriodicalIF":0.0,"publicationDate":"2021-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86115819","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}
Due to their unique mechanical, tribological, thermal, and anticorrosion properties, nickel-tungsten (Ni-W) alloy films have become indispensable for many industrial applications. The present study investigates the impact of W content on the microstructure and mechanical properties of Ni-W thin films. By co-sputtering of Ni and W on silicon wafers coated with a thin buffer layer (∼20 nm) of titanium (Ti), six Ni-W coatings were fabricated, ranging from pure Ni to pure W. The samples were characterized using energy dispersive spectroscopy, x-ray diffraction, scanning electron microscopy, atomic force microscopy, and microindentation. The results show that hardness of the Ni-W films is primarily a function of the W content, which changes the microstructure and surface morphology of the samples. When W concentration is smaller than 40 at. %, the Ni-rich samples have a face-centered cubic structure and the hardness increases with the W content. For the samples having 40 < W < 55 at. %, the sensitivity of the hardness to the W content becomes markedly low, which could be due to the presence of an amorphous phase. Finally, the impact of W addition on the hardness of the samples containing 55–80 at. % W is two times greater than that of W < 40 at. %. The extra hardening effect could be attributed to the dominancy of a solid solution hardened body-centered cubic W phase and electronic interaction between two transition metals. This sharp increase in the hardness leads to obtaining a high hardness of 21.9 ± 2.0 GPa for the Ni-79 at. % W film. The findings of this study show that solid solution strengthening could be considered the main hardening mechanism of these films.
{"title":"Influence of W content on microstructure and surface morphology of hard Ni-W films fabricated by magnetron co-sputtering","authors":"Amir R. Esmaeili, N. Mir, R. Mohammadi","doi":"10.1116/6.0000915","DOIUrl":"https://doi.org/10.1116/6.0000915","url":null,"abstract":"Due to their unique mechanical, tribological, thermal, and anticorrosion properties, nickel-tungsten (Ni-W) alloy films have become indispensable for many industrial applications. The present study investigates the impact of W content on the microstructure and mechanical properties of Ni-W thin films. By co-sputtering of Ni and W on silicon wafers coated with a thin buffer layer (∼20 nm) of titanium (Ti), six Ni-W coatings were fabricated, ranging from pure Ni to pure W. The samples were characterized using energy dispersive spectroscopy, x-ray diffraction, scanning electron microscopy, atomic force microscopy, and microindentation. The results show that hardness of the Ni-W films is primarily a function of the W content, which changes the microstructure and surface morphology of the samples. When W concentration is smaller than 40 at. %, the Ni-rich samples have a face-centered cubic structure and the hardness increases with the W content. For the samples having 40 < W < 55 at. %, the sensitivity of the hardness to the W content becomes markedly low, which could be due to the presence of an amorphous phase. Finally, the impact of W addition on the hardness of the samples containing 55–80 at. % W is two times greater than that of W < 40 at. %. The extra hardening effect could be attributed to the dominancy of a solid solution hardened body-centered cubic W phase and electronic interaction between two transition metals. This sharp increase in the hardness leads to obtaining a high hardness of 21.9 ± 2.0 GPa for the Ni-79 at. % W film. The findings of this study show that solid solution strengthening could be considered the main hardening mechanism of these films.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":"32 3 1","pages":"033405"},"PeriodicalIF":0.0,"publicationDate":"2021-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90611587","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}
Among Professor Arthur Gossard’s many contributions to crystal growth are those resulting in important improvements in the quality and performance of quantum-well and quantum-dot semiconductor lasers. In celebration of his 85th birthday, we review the development of a semiconductor laser theory that is motivated and guided, in part, by those advances. This theory combines condensed matter theory and laser physics to provide understanding at a microscopic level, i.e., in terms of electrons and holes, and their interaction with the radiation field while influenced by the lattice.
{"title":"Influence of quantum-confined device fabrication on semiconductor-laser theory","authors":"W. Chow, F. Jahnke","doi":"10.1116/6.0000767","DOIUrl":"https://doi.org/10.1116/6.0000767","url":null,"abstract":"Among Professor Arthur Gossard’s many contributions to crystal growth are those resulting in important improvements in the quality and performance of quantum-well and quantum-dot semiconductor lasers. In celebration of his 85th birthday, we review the development of a semiconductor laser theory that is motivated and guided, in part, by those advances. This theory combines condensed matter theory and laser physics to provide understanding at a microscopic level, i.e., in terms of electrons and holes, and their interaction with the radiation field while influenced by the lattice.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":"32 1","pages":"032408"},"PeriodicalIF":0.0,"publicationDate":"2021-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81014828","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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