Michael Hayes, M. Jenkins, J. Woodruff, D. Moser, C. Dezelah, J. F. ConleyJr.
The resistivity, morphology, and effective work function of thin film ruthenium deposited by thermal atomic layer deposition (ALD) using η4-2,3-dimethylbutadiene ruthenium tricarbonyl [Ru(DMBD)(CO)3] and O2 are investigated before and after annealing at temperatures up to 500 °C. Annealing at 500 °C in either N2 or H2/N2 reduces the average resistivity of as-deposited 30 nm thick Ru films from 16.2 to as low as 13.7 or 9.1 μΩ cm, respectively, approaching the bulk value of Ru. X-ray diffraction shows that as-deposited films are polycrystalline hexagonal Ru. Annealing at 500 °C in either N2 or H2/N2 results in crystallite growth accompanied by a roughening of the surface from approximately 0.7 to 2.2 nm RMS, as shown by atomic force microscopy. Secondary ion mass spectroscopy shows low residual carbon and oxygen in as-deposited films. Annealing in N2 at 500 °C reduces only the carbon content, whereas annealing in H2/N2 at 500 °C results in a further reduction of carbon combined with reduction in oxygen as well. Using series of metal/oxide/silicon capacitors with varying oxide thickness, the effective work function of 500 °C H2/N2 annealed Ru films on ALD Al2O3 and HfO2 was determined to be approximately 4.9 and 5.3 eV, respectively. Using internal photoemission spectroscopy, the Ru/Al2O3 and Ru/HfO2 electron energy barrier heights were determined to be 3.4 ± 0.1 and 3.8 ± 0.1 eV, respectively.
{"title":"Improved properties of atomic layer deposited ruthenium via postdeposition annealing","authors":"Michael Hayes, M. Jenkins, J. Woodruff, D. Moser, C. Dezelah, J. F. ConleyJr.","doi":"10.1116/6.0001078","DOIUrl":"https://doi.org/10.1116/6.0001078","url":null,"abstract":"The resistivity, morphology, and effective work function of thin film ruthenium deposited by thermal atomic layer deposition (ALD) using η4-2,3-dimethylbutadiene ruthenium tricarbonyl [Ru(DMBD)(CO)3] and O2 are investigated before and after annealing at temperatures up to 500 °C. Annealing at 500 °C in either N2 or H2/N2 reduces the average resistivity of as-deposited 30 nm thick Ru films from 16.2 to as low as 13.7 or 9.1 μΩ cm, respectively, approaching the bulk value of Ru. X-ray diffraction shows that as-deposited films are polycrystalline hexagonal Ru. Annealing at 500 °C in either N2 or H2/N2 results in crystallite growth accompanied by a roughening of the surface from approximately 0.7 to 2.2 nm RMS, as shown by atomic force microscopy. Secondary ion mass spectroscopy shows low residual carbon and oxygen in as-deposited films. Annealing in N2 at 500 °C reduces only the carbon content, whereas annealing in H2/N2 at 500 °C results in a further reduction of carbon combined with reduction in oxygen as well. Using series of metal/oxide/silicon capacitors with varying oxide thickness, the effective work function of 500 °C H2/N2 annealed Ru films on ALD Al2O3 and HfO2 was determined to be approximately 4.9 and 5.3 eV, respectively. Using internal photoemission spectroscopy, the Ru/Al2O3 and Ru/HfO2 electron energy barrier heights were determined to be 3.4 ± 0.1 and 3.8 ± 0.1 eV, respectively.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81422408","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}
Ryan J. Gasvoda, Xue Wang, Prabhat Kumar, E. Hudson, S. Agarwal
Selective functionalization of SiO2 and SiNx surfaces is challenging after atmospheric exposure or after exposure to an etching plasma chemistry as both surfaces tend to have similar functional groups. Here, we show that a SiNx surface can be selectively functionalized over SiO2 with benzaldehyde after the first atomic layer etching (ALE) cycle. Similar to our previous work on pristine plasma-deposited SiO2 and SiNx surfaces [R. J. Gasvoda, Z. Zhang, E. A. Hudson, and S. Agarwal, J. Vac. Sci Technol. A 39, 040401 (2021)], this selective functionalization can be used to increase the overall SiO2 to SiNx etch selectivity during ALE. The surface reactions, composition, and film thickness during ALE were monitored using in situ surface infrared spectroscopy and in situ four-wavelength ellipsometry. Our ALE process consisted of alternating cycles of CFx deposition from a C4F6/Ar plasma and an Ar activation plasma with an average ion energy of ∼210 eV. The first ALE cycle removed the surface SiOxNy layer on the SiNx surface and created reactive sites for selective benzaldehyde attachment.
{"title":"Selective functionalization of partially etched SiNx to enhance SiO2 to SiNx etch selectivity","authors":"Ryan J. Gasvoda, Xue Wang, Prabhat Kumar, E. Hudson, S. Agarwal","doi":"10.1116/6.0001110","DOIUrl":"https://doi.org/10.1116/6.0001110","url":null,"abstract":"Selective functionalization of SiO2 and SiNx surfaces is challenging after atmospheric exposure or after exposure to an etching plasma chemistry as both surfaces tend to have similar functional groups. Here, we show that a SiNx surface can be selectively functionalized over SiO2 with benzaldehyde after the first atomic layer etching (ALE) cycle. Similar to our previous work on pristine plasma-deposited SiO2 and SiNx surfaces [R. J. Gasvoda, Z. Zhang, E. A. Hudson, and S. Agarwal, J. Vac. Sci Technol. A 39, 040401 (2021)], this selective functionalization can be used to increase the overall SiO2 to SiNx etch selectivity during ALE. The surface reactions, composition, and film thickness during ALE were monitored using in situ surface infrared spectroscopy and in situ four-wavelength ellipsometry. Our ALE process consisted of alternating cycles of CFx deposition from a C4F6/Ar plasma and an Ar activation plasma with an average ion energy of ∼210 eV. The first ALE cycle removed the surface SiOxNy layer on the SiNx surface and created reactive sites for selective benzaldehyde attachment.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77606039","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}
Understanding energy distributions and kinetic processes in low temperature plasmas is vital to increase their utility for a range of applications, in particular pollution remediation. Optical emission spectroscopy (OES) was employed to elucidate energetic and kinetic trends for several diatomic species in CH4/N2 and CH4/H2O plasma systems. Vast differences in rotational and vibrational temperatures between dissimilar plasma species were observed, indicating the internal temperatures of excited state species are not equilibrated with each other. In combination with energy partitioning results, species formation and destruction rates within the plasma were derived from time-resolved OES data. The results provide insight into molecule formation pathways, including that the formation of CN may be related to excited nitrogen species available in CH4/N2 plasmas.
{"title":"Elucidating energetics and kinetics in environmentally relevant mixed gas plasmas","authors":"Tara L. Van Surksum, E. R. Fisher","doi":"10.1116/6.0001080","DOIUrl":"https://doi.org/10.1116/6.0001080","url":null,"abstract":"Understanding energy distributions and kinetic processes in low temperature plasmas is vital to increase their utility for a range of applications, in particular pollution remediation. Optical emission spectroscopy (OES) was employed to elucidate energetic and kinetic trends for several diatomic species in CH4/N2 and CH4/H2O plasma systems. Vast differences in rotational and vibrational temperatures between dissimilar plasma species were observed, indicating the internal temperatures of excited state species are not equilibrated with each other. In combination with energy partitioning results, species formation and destruction rates within the plasma were derived from time-resolved OES data. The results provide insight into molecule formation pathways, including that the formation of CN may be related to excited nitrogen species available in CH4/N2 plasmas.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81399039","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}
In this work, a stacked heterostructure made up of single-layer WSe2 and graphene was created through a scalable and efficient way. Graphene was grown on a Ni (111) single crystal, producing an ordered and well-defined carbon overlayer that is strongly hybridized with the support, disrupting its peculiar conductive properties. A monolayer WSe2 was deposited on top of graphene by the simultaneous evaporation of metal W and elemental Se. We demonstrate here that the chalcogen can efficiently intercalate between graphene and the Ni surface, decoupling the two materials and forming a buffering NiSex layer. The concurrent selenization of both W and Ni effectively eliminates the need for an additional decoupling step in the synthesis of a free-standing graphene/Ni heterostructure. The formation process of the complex WSe2/Graphene/NiSex/Ni(111) heterostructure was studied by means of low-energy electron diffraction, x-ray photoelectron spectroscopy, angle-resolved ultraviolet photoelectron spectroscopy, and ex situ Raman spectroscopy. These analyses confirm the presence of single-layer WSe2 on top of a free-standing graphene.
{"title":"Preparation and electronic structure of the WSe2/graphene/NiSex/Ni(111) heterostructure","authors":"Roberto Sant, M. Cattelan, S. Agnoli, G. Granozzi","doi":"10.1116/6.0001134","DOIUrl":"https://doi.org/10.1116/6.0001134","url":null,"abstract":"In this work, a stacked heterostructure made up of single-layer WSe2 and graphene was created through a scalable and efficient way. Graphene was grown on a Ni (111) single crystal, producing an ordered and well-defined carbon overlayer that is strongly hybridized with the support, disrupting its peculiar conductive properties. A monolayer WSe2 was deposited on top of graphene by the simultaneous evaporation of metal W and elemental Se. We demonstrate here that the chalcogen can efficiently intercalate between graphene and the Ni surface, decoupling the two materials and forming a buffering NiSex layer. The concurrent selenization of both W and Ni effectively eliminates the need for an additional decoupling step in the synthesis of a free-standing graphene/Ni heterostructure. The formation process of the complex WSe2/Graphene/NiSex/Ni(111) heterostructure was studied by means of low-energy electron diffraction, x-ray photoelectron spectroscopy, angle-resolved ultraviolet photoelectron spectroscopy, and ex situ Raman spectroscopy. These analyses confirm the presence of single-layer WSe2 on top of a free-standing graphene.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74923519","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}
Thin films of materials are critical components for most areas of sustainable technologies, making thin film techniques, such as chemical vapor deposition (CVD), instrumental for a sustainable future. It is, therefore, of great importance to critically consider the sustainability aspects of CVD processes themselves used to make thin films for sustainable technologies. Here, we point to several common practices in CVD that are not sustainable. From these, we offer a perspective on several principles for a sustainable, “Green CVD” philosophy, which we hope will spur research on how to make CVD more sustainable without affecting the properties of the deposited film. We hope that these principles can be developed by the research community over time and be used to establish research on how to make CVD more sustainable and that a Green CVD philosophy can develop new research directions for both precursor and reactor design to reduce the precursor and energy consumption in CVD processes.
{"title":"Green CVD—Toward a sustainable philosophy for thin film deposition by chemical vapor deposition","authors":"H. Pedersen, S. Barry, J. Sundqvist","doi":"10.1116/6.0001125","DOIUrl":"https://doi.org/10.1116/6.0001125","url":null,"abstract":"Thin films of materials are critical components for most areas of sustainable technologies, making thin film techniques, such as chemical vapor deposition (CVD), instrumental for a sustainable future. It is, therefore, of great importance to critically consider the sustainability aspects of CVD processes themselves used to make thin films for sustainable technologies. Here, we point to several common practices in CVD that are not sustainable. From these, we offer a perspective on several principles for a sustainable, “Green CVD” philosophy, which we hope will spur research on how to make CVD more sustainable without affecting the properties of the deposited film. We hope that these principles can be developed by the research community over time and be used to establish research on how to make CVD more sustainable and that a Green CVD philosophy can develop new research directions for both precursor and reactor design to reduce the precursor and energy consumption in CVD processes.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81888531","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. V. Bulyarskiy, D. Koiva, V. S. Belov, E. Zenova, G. Rudakov, G. Gusarov
This work is devoted to the problem of the formation of titanium monoxide and dioxide by magnetron sputtering. Sputtering titanium in constant flows of oxygen and argon and constant magnetron power leads to the creation of equilibrium partial pressures of oxygen and titanium vapors. The conditions for the synthesis of nanocrystalline titanium monoxide at low temperatures were determined experimentally and substantiated by the thermodynamic method. An analysis is made by the method of minimizing the Gibbs free energy. We have obtained an expression for the ratio of the oxygen flow and the gas discharge power, the analysis of which makes it possible to determine the conditions for the formation of titanium oxide with a certain stoichiometric composition. The developed method for the analysis of equilibrium in the deposition chamber can be used to identify the conditions for the synthesis of other compounds that are important for practice, including oxides and chalcogenides, and the horizons of their use in nanoelectronics are constantly growing at the present time.
{"title":"Titanium monoxide and titanium dioxide thin film formation by magnetron sputtering and its thermodynamic model","authors":"S. V. Bulyarskiy, D. Koiva, V. S. Belov, E. Zenova, G. Rudakov, G. Gusarov","doi":"10.1116/6.0001065","DOIUrl":"https://doi.org/10.1116/6.0001065","url":null,"abstract":"This work is devoted to the problem of the formation of titanium monoxide and dioxide by magnetron sputtering. Sputtering titanium in constant flows of oxygen and argon and constant magnetron power leads to the creation of equilibrium partial pressures of oxygen and titanium vapors. The conditions for the synthesis of nanocrystalline titanium monoxide at low temperatures were determined experimentally and substantiated by the thermodynamic method. An analysis is made by the method of minimizing the Gibbs free energy. We have obtained an expression for the ratio of the oxygen flow and the gas discharge power, the analysis of which makes it possible to determine the conditions for the formation of titanium oxide with a certain stoichiometric composition. The developed method for the analysis of equilibrium in the deposition chamber can be used to identify the conditions for the synthesis of other compounds that are important for practice, including oxides and chalcogenides, and the horizons of their use in nanoelectronics are constantly growing at the present time.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86711218","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. P. Lorona, J. Diulus, Jo E. Bergevin, R. Addou, G. Herman
Controlling the grown oxide composition, the oxide/semiconductor interface properties, and the semiconductor surface composition is of interest for SiGe devices. We have used ambient-pressure x-ray photoelectron spectroscopy (AP-XPS) to study the initial stages of dry thermal oxidation of an epitaxial Si0.60Ge0.40(001) film on Si(001). Si 2p and Ge 3d chemical-state resolved AP-XPS was performed at 300 °C and O2 pressures ( P O 2 ) of 10−4, 10−2, and 1 mbar during oxide growth. The National Institute of Standards simulated electron spectra for surface analysis (SESSA) was used to analyze both the oxide composition and the thickness versus time for each pressure. At all three P O 2, the SESSA analysis indicated that oxidation proceeds via three oxide growth rate regimes: an initial rapid regime, an intermediate transitionary regime, and finally a quasisaturation slow regime. The Si and Ge oxidation rates were found to be pressure dependent during the rapid regime with both rates decreasing monotonically with decreasing pressure. Results indicated that Ge was much more sensitive to changes in P O 2 compared to Si. As a result, a decrease in P O 2 resulted in significant suppression of GeO2 formation compared to SiO2. Using SESSA, we were able to quantify the grown oxide composition and the thickness, both of which were strongly dependent on O2 pressure. The Ge composition, in Si1−xGexO2, was found to decrease monotonically with decreasing P O 2.
{"title":"Operando study of the preferential growth of SiO2 during the dry thermal oxidation of Si0.60Ge0.40(001) by ambient pressure x-ray photoelectron spectroscopy","authors":"S. P. Lorona, J. Diulus, Jo E. Bergevin, R. Addou, G. Herman","doi":"10.1116/6.0001174","DOIUrl":"https://doi.org/10.1116/6.0001174","url":null,"abstract":"Controlling the grown oxide composition, the oxide/semiconductor interface properties, and the semiconductor surface composition is of interest for SiGe devices. We have used ambient-pressure x-ray photoelectron spectroscopy (AP-XPS) to study the initial stages of dry thermal oxidation of an epitaxial Si0.60Ge0.40(001) film on Si(001). Si 2p and Ge 3d chemical-state resolved AP-XPS was performed at 300 °C and O2 pressures ( P O 2 ) of 10−4, 10−2, and 1 mbar during oxide growth. The National Institute of Standards simulated electron spectra for surface analysis (SESSA) was used to analyze both the oxide composition and the thickness versus time for each pressure. At all three P O 2, the SESSA analysis indicated that oxidation proceeds via three oxide growth rate regimes: an initial rapid regime, an intermediate transitionary regime, and finally a quasisaturation slow regime. The Si and Ge oxidation rates were found to be pressure dependent during the rapid regime with both rates decreasing monotonically with decreasing pressure. Results indicated that Ge was much more sensitive to changes in P O 2 compared to Si. As a result, a decrease in P O 2 resulted in significant suppression of GeO2 formation compared to SiO2. Using SESSA, we were able to quantify the grown oxide composition and the thickness, both of which were strongly dependent on O2 pressure. The Ge composition, in Si1−xGexO2, was found to decrease monotonically with decreasing P O 2.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91000887","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}
Functional hydroxylapatite (HAp) coatings deposited by atmospheric plasma spraying on parts of hip and knee endoprosthetic implants, artificial dental roots, spinal implants, and other medical devices serve to aid in osseointegration by providing a biocompatible and osseoconductive/osseoinductive template for bone growth-supporting actions of cytokines and noncollagenous proteins and proteoglycans, mediated by transmembrane proteins such as integrins. To be successful in this task, HAp coatings need to be carefully designed and optimized by closely controlling key properties such as phase composition, degree of crystallinity, crystallographic texture, thickness, adhesion strength to the implant surface, porosity, pore size distribution, surface nanostructure and roughness, residual coating stresses, and dissolution kinetics during in vivo contact with extracellular fluid. As this contribution discusses salient aspects of design, properties, and application of HAp coatings, it attempts to chart ways toward improving their in vivo performance and, thus, may be considered a helping hand and guiding manual of instruction for their successful deposition. In this review, much contextual recourse has been taken to the work of the present author and his research group during the last two and a half decades.
{"title":"Functional plasma-sprayed hydroxylapatite coatings for medical application: Clinical performance requirements and key property enhancement","authors":"R. Heimann","doi":"10.1116/6.0001132","DOIUrl":"https://doi.org/10.1116/6.0001132","url":null,"abstract":"Functional hydroxylapatite (HAp) coatings deposited by atmospheric plasma spraying on parts of hip and knee endoprosthetic implants, artificial dental roots, spinal implants, and other medical devices serve to aid in osseointegration by providing a biocompatible and osseoconductive/osseoinductive template for bone growth-supporting actions of cytokines and noncollagenous proteins and proteoglycans, mediated by transmembrane proteins such as integrins. To be successful in this task, HAp coatings need to be carefully designed and optimized by closely controlling key properties such as phase composition, degree of crystallinity, crystallographic texture, thickness, adhesion strength to the implant surface, porosity, pore size distribution, surface nanostructure and roughness, residual coating stresses, and dissolution kinetics during in vivo contact with extracellular fluid. As this contribution discusses salient aspects of design, properties, and application of HAp coatings, it attempts to chart ways toward improving their in vivo performance and, thus, may be considered a helping hand and guiding manual of instruction for their successful deposition. In this review, much contextual recourse has been taken to the work of the present author and his research group during the last two and a half decades.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89351671","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}
Syeed E. Ahmed, Violet M. Poole, John D. Igo, Y. Gu, M. McCluskey
The ability to define the crystal phase of oxide semiconductors could benefit transparent electronics and catalysis. In this paper, laser-induced localized phase transitions of titanium dioxide (TiO2) thin films are reported. Irradiation was performed with a 532 nm continuous wave laser. Raman spectroscopy and micro-Raman mapping were used to identify the phase transformations. A Raman map of the anatase Eg mode (144 cm−1) and rutile Ag mode (608 cm−1) revealed the formation of crystalline microstructures due to the laser treatment. Laser irradiation under vacuum results in an anatase-to-rutile phase transition. Irradiating the rutile region in air changes the crystal structure back to anatase, despite the thermodynamic stability of rutile. The results suggest that irradiated photons are absorbed by defects, resulting in localized electronic excitation that leads to a mixture of amorphous and crystalline regions. The phase of the crystalline regions depends strongly on the ambient conditions (vacuum versus air).
{"title":"Localized phase transition of TiO2 thin films induced by sub-bandgap laser irradiation","authors":"Syeed E. Ahmed, Violet M. Poole, John D. Igo, Y. Gu, M. McCluskey","doi":"10.1116/6.0001088","DOIUrl":"https://doi.org/10.1116/6.0001088","url":null,"abstract":"The ability to define the crystal phase of oxide semiconductors could benefit transparent electronics and catalysis. In this paper, laser-induced localized phase transitions of titanium dioxide (TiO2) thin films are reported. Irradiation was performed with a 532 nm continuous wave laser. Raman spectroscopy and micro-Raman mapping were used to identify the phase transformations. A Raman map of the anatase Eg mode (144 cm−1) and rutile Ag mode (608 cm−1) revealed the formation of crystalline microstructures due to the laser treatment. Laser irradiation under vacuum results in an anatase-to-rutile phase transition. Irradiating the rutile region in air changes the crystal structure back to anatase, despite the thermodynamic stability of rutile. The results suggest that irradiated photons are absorbed by defects, resulting in localized electronic excitation that leads to a mixture of amorphous and crystalline regions. The phase of the crystalline regions depends strongly on the ambient conditions (vacuum versus air).","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90893810","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}
E. Knehr, M. Ziegler, S. Linzen, K. Ilin, P. Schanz, J. Plentz, M. Diegel, H. Schmidt, E. Il'ichev, M. Siegel
Superconducting niobium nitride thin films are used for a variety of photon detectors, quantum devices, and superconducting electronics. Most of these applications require highly uniform films, for instance, when moving from single-pixel detectors to arrays with a large active area. Plasma-enhanced atomic layer deposition (ALD) of superconducting niobium nitride is a feasible option to produce high-quality, conformal thin films and has been demonstrated as a film deposition method to fabricate superconducting nanowire single-photon detectors before. Here, we explore the property spread of ALD-NbN across a 6-in. wafer area. Over the equivalent area of a 2-in. wafer, we measure a maximum deviation of 1% in critical temperature and 12% in switching current. Toward larger areas, structural characterizations indicate that changes in the crystal structure seem to be the limiting factor rather than film composition or impurities. The results show that ALD is suited to fabricate NbN thin films as a material for large-area detector arrays and for new detector designs and devices requiring uniform superconducting thin films with precise thickness control.
{"title":"Wafer-level uniformity of atomic-layer-deposited niobium nitride thin films for quantum devices","authors":"E. Knehr, M. Ziegler, S. Linzen, K. Ilin, P. Schanz, J. Plentz, M. Diegel, H. Schmidt, E. Il'ichev, M. Siegel","doi":"10.1116/6.0001126","DOIUrl":"https://doi.org/10.1116/6.0001126","url":null,"abstract":"Superconducting niobium nitride thin films are used for a variety of photon detectors, quantum devices, and superconducting electronics. Most of these applications require highly uniform films, for instance, when moving from single-pixel detectors to arrays with a large active area. Plasma-enhanced atomic layer deposition (ALD) of superconducting niobium nitride is a feasible option to produce high-quality, conformal thin films and has been demonstrated as a film deposition method to fabricate superconducting nanowire single-photon detectors before. Here, we explore the property spread of ALD-NbN across a 6-in. wafer area. Over the equivalent area of a 2-in. wafer, we measure a maximum deviation of 1% in critical temperature and 12% in switching current. Toward larger areas, structural characterizations indicate that changes in the crystal structure seem to be the limiting factor rather than film composition or impurities. The results show that ALD is suited to fabricate NbN thin films as a material for large-area detector arrays and for new detector designs and devices requiring uniform superconducting thin films with precise thickness control.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76295038","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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