Gallium (III) sulfide is a frontrunner for many energy storage and optoelectronic applications, which demand a deposition technique that offers a high level of control over thickness, composition, and conformality. Atomic layer deposition (ALD) is a potential technique in this regard. However, the state-of-the-art ALD processes for depositing Ga2S3 often lead to films that are amorphous and nonstoichiometric, and contain significant contaminations. Herein, we present a new plasma-enhanced atomic layer deposition (PE-ALD) process using the hexakis(dimethylamido)digallium precursor and H2S plasma coreactant to deposit high-quality Ga2S3 sulfide thin films and compare it to the thermal ALD process using the same reactants. While both cases exhibit typical ALD characteristics, substantial disparity is observed in the material properties. The PE-ALD process deposits crystalline Ga2S3 sulfide thin films at a temperature as low as 125 °C with a growth per cycle of 1.71 Å/cycle. Additionally, the PE-ALD process results in smooth and stoichiometric Ga2S3 films without any detectable carbon and oxygen contamination. Grazing incidence wide-angle x-ray scattering analysis indicates that the as-deposited Ga2S3 film crystallizes in a cubic structure with a preferred orientation along the [111] direction. The Ga2S3 film exhibits a transmittance of 70% and a bandgap of 3.2 eV with a direct transition.
{"title":"Plasma-enhanced atomic layer deposition of crystalline Ga2S3 thin films","authors":"Femi Mathew, Nithin Poonkottil, Eduardo Solano, Dirk Poelman, Zeger Hens, Christophe Detavernier, Jolien Dendooven","doi":"10.1116/6.0002993","DOIUrl":"https://doi.org/10.1116/6.0002993","url":null,"abstract":"Gallium (III) sulfide is a frontrunner for many energy storage and optoelectronic applications, which demand a deposition technique that offers a high level of control over thickness, composition, and conformality. Atomic layer deposition (ALD) is a potential technique in this regard. However, the state-of-the-art ALD processes for depositing Ga2S3 often lead to films that are amorphous and nonstoichiometric, and contain significant contaminations. Herein, we present a new plasma-enhanced atomic layer deposition (PE-ALD) process using the hexakis(dimethylamido)digallium precursor and H2S plasma coreactant to deposit high-quality Ga2S3 sulfide thin films and compare it to the thermal ALD process using the same reactants. While both cases exhibit typical ALD characteristics, substantial disparity is observed in the material properties. The PE-ALD process deposits crystalline Ga2S3 sulfide thin films at a temperature as low as 125 °C with a growth per cycle of 1.71 Å/cycle. Additionally, the PE-ALD process results in smooth and stoichiometric Ga2S3 films without any detectable carbon and oxygen contamination. Grazing incidence wide-angle x-ray scattering analysis indicates that the as-deposited Ga2S3 film crystallizes in a cubic structure with a preferred orientation along the [111] direction. The Ga2S3 film exhibits a transmittance of 70% and a bandgap of 3.2 eV with a direct transition.","PeriodicalId":17490,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"92 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135695632","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Taleb Alwadi, Christian Notthoff, Shankar Dutt, Jessica Wierbik, Nahid Afrin, Alexander Kiy, Patrick Kluth
Ion track formation, irradiation-induced damage (amorphization), and the formation of porosity in InSb after 185 MeV 197Au swift heavy ion irradiation are studied as a function of ion fluence and irradiation angle. Rutherford backscattering spectrometry in channeling geometry reveals an ion track radius of about 16 nm for irradiation normal to the surface and 21 nm for off-normal irradiation at 30° and 60°. Cross-sectional scanning electron microscopy shows significant porosity that increases when irradiation was performed off-normal to the surface. Off-normal irradiation shows a preferential orientation of the pores at about 45° relative to the surface normal. Moreover, when subjected to identical conditions, InSb samples demonstrate notably higher swelling compared to GaSb bulk samples.
{"title":"Ion track formation and porosity in InSb induced by swift heavy ion irradiation","authors":"Taleb Alwadi, Christian Notthoff, Shankar Dutt, Jessica Wierbik, Nahid Afrin, Alexander Kiy, Patrick Kluth","doi":"10.1116/6.0003007","DOIUrl":"https://doi.org/10.1116/6.0003007","url":null,"abstract":"Ion track formation, irradiation-induced damage (amorphization), and the formation of porosity in InSb after 185 MeV 197Au swift heavy ion irradiation are studied as a function of ion fluence and irradiation angle. Rutherford backscattering spectrometry in channeling geometry reveals an ion track radius of about 16 nm for irradiation normal to the surface and 21 nm for off-normal irradiation at 30° and 60°. Cross-sectional scanning electron microscopy shows significant porosity that increases when irradiation was performed off-normal to the surface. Off-normal irradiation shows a preferential orientation of the pores at about 45° relative to the surface normal. Moreover, when subjected to identical conditions, InSb samples demonstrate notably higher swelling compared to GaSb bulk samples.","PeriodicalId":17490,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135695963","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In order to explain all of the spectral features observed in the U O4,5 x-ray absorption spectrum of uranium dioxide (UO2), it is necessary to include both multielectron effects and multiatomic effects. The 5d (core hole)-5f (electron) angular momentum coupling that gives rise to the giant resonance has been treated within ligand field density functional theory, and the electron scattering that generates the extended x-ray absorption fine structure has been included via the spectral simulation program FEFF: both within a UO8 fluorite cluster picture. An atomic model is insufficient to explain all of the observed spectral features.
{"title":"Multielectronic and multiatomic effects in the U O4,5 x-ray absorption spectroscopy of uranium dioxide","authors":"J. G. Tobin, H. Ramanantoanina, C. Daul, S.-W. Yu","doi":"10.1116/6.0002969","DOIUrl":"https://doi.org/10.1116/6.0002969","url":null,"abstract":"In order to explain all of the spectral features observed in the U O4,5 x-ray absorption spectrum of uranium dioxide (UO2), it is necessary to include both multielectron effects and multiatomic effects. The 5d (core hole)-5f (electron) angular momentum coupling that gives rise to the giant resonance has been treated within ligand field density functional theory, and the electron scattering that generates the extended x-ray absorption fine structure has been included via the spectral simulation program FEFF: both within a UO8 fluorite cluster picture. An atomic model is insufficient to explain all of the observed spectral features.","PeriodicalId":17490,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"101 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135739395","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tomoyuki Nonaka, Kazuo Takahashi, Akimi Uchida, Stefan Lundgaard, Osamu Tsuji
The Bosch process is a deep etching method for silicon that uses C4F8 plasma-deposited polymerized films as passivation films to protect the silicon sidewalls. This study measured the deposition rate of the passivation films and the etch rate with F-radical exposure and analyzed the chemical composition of the films. Additionally, we observed the deformation of the passivation films during the Bosch process and assessed its influence on the etch profiles. As the C4F8 flow rates increased, the deposition rates attained a local maximum, subsequently decreased to a local minimum and then increased again. The deposition rates were extremely low when the pressure exceeded 10 Pa. With the increasing C4F8 flow rates, inductively coupled plasma power, and pressure, the respective bond content varied up to 10%, and C—CFX and C—C bond contents were replaced with CF2 and CF contents, respectively. The results indicated that the chemical composition of the films did not affect the etch rates of the films, and upon exposure to F radicals, the chemical composition of all films transformed into an identical chemical composition with a higher CF2 bond content. Polymerized films with low CF2-bond content deformed with F-radical exposure, enabled the passage of F radicals, and did not serve as passivation films. In addition to high deposition rates and high F-radical resistance, the Bosch process requires passivation films with high CF2 bond content. The present findings will aid in tuning the parameters of the Bosch process and increase the productivity of silicon deep reactive-ion etching.
{"title":"Effects of C4F8 plasma polymerization film on etching profiles in the Bosch process","authors":"Tomoyuki Nonaka, Kazuo Takahashi, Akimi Uchida, Stefan Lundgaard, Osamu Tsuji","doi":"10.1116/5.0158954","DOIUrl":"https://doi.org/10.1116/5.0158954","url":null,"abstract":"The Bosch process is a deep etching method for silicon that uses C4F8 plasma-deposited polymerized films as passivation films to protect the silicon sidewalls. This study measured the deposition rate of the passivation films and the etch rate with F-radical exposure and analyzed the chemical composition of the films. Additionally, we observed the deformation of the passivation films during the Bosch process and assessed its influence on the etch profiles. As the C4F8 flow rates increased, the deposition rates attained a local maximum, subsequently decreased to a local minimum and then increased again. The deposition rates were extremely low when the pressure exceeded 10 Pa. With the increasing C4F8 flow rates, inductively coupled plasma power, and pressure, the respective bond content varied up to 10%, and C—CFX and C—C bond contents were replaced with CF2 and CF contents, respectively. The results indicated that the chemical composition of the films did not affect the etch rates of the films, and upon exposure to F radicals, the chemical composition of all films transformed into an identical chemical composition with a higher CF2 bond content. Polymerized films with low CF2-bond content deformed with F-radical exposure, enabled the passage of F radicals, and did not serve as passivation films. In addition to high deposition rates and high F-radical resistance, the Bosch process requires passivation films with high CF2 bond content. The present findings will aid in tuning the parameters of the Bosch process and increase the productivity of silicon deep reactive-ion etching.","PeriodicalId":17490,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135831051","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Písaříková, J. Olejníček, I. Venkrbcová, L. Nožka, S. Cichoň, A. Azinfar, R. Hippler, C. A. Helm, M. Mašláň, L. Machala, Z. Hubička
In this study, thin films of CuFeO2 were prepared using radio frequency reactive sputtering (RF) and reactive high-power impulse magnetron sputtering combined with electron cyclotron wave resonance plasma (HiPIMS-ECWR). The plasma was characterized using an RF ion probe. Plasma density, tail electron energy, and electron temperature were extracted from the measured data. The films were deposited on fluorine-doped tin oxide-coated glass and quartz glass, with the substrates being heated during the deposition process. The final delafossite CuFeO2 structure was formed after annealing in an argon gas flow at 550–600 °C. The ideal deposition conditions were found to be with a stoichiometric ratio of Cu:Fe = 1:1, which was the optimal condition for creating the delafossite CuFeO2 structure. The measured optical bandgap of CuFeO2 was 1.4 eV. The deposited CuFeO2 films were subjected to photoelectrochemical measurements in the cathodic region to investigate their potential application in solar photocatalytic water splitting. The films showed photocatalytic activity, with a photocurrent density of around 70 μA/cm2 (under an incident light irradiation of 62 mW/cm2, AM 1.5 G). The electrochemical properties of the layers were studied using open circuit potential, linear voltammetry, and chronoamperometry. The surface morphology and chemical composition of the layers were analyzed by atomic force microscopy and energy-dispersive x-ray spectroscopy, respectively. The crystalline structure was determined using XRD and Raman spectroscopy. The results of these methods are presented and discussed in this article.
{"title":"CuFeO2 prepared by electron cyclotron wave resonance-assisted reactive HiPIMS with two magnetrons and radio frequency magnetron sputtering","authors":"A. Písaříková, J. Olejníček, I. Venkrbcová, L. Nožka, S. Cichoň, A. Azinfar, R. Hippler, C. A. Helm, M. Mašláň, L. Machala, Z. Hubička","doi":"10.1116/6.0002902","DOIUrl":"https://doi.org/10.1116/6.0002902","url":null,"abstract":"In this study, thin films of CuFeO2 were prepared using radio frequency reactive sputtering (RF) and reactive high-power impulse magnetron sputtering combined with electron cyclotron wave resonance plasma (HiPIMS-ECWR). The plasma was characterized using an RF ion probe. Plasma density, tail electron energy, and electron temperature were extracted from the measured data. The films were deposited on fluorine-doped tin oxide-coated glass and quartz glass, with the substrates being heated during the deposition process. The final delafossite CuFeO2 structure was formed after annealing in an argon gas flow at 550–600 °C. The ideal deposition conditions were found to be with a stoichiometric ratio of Cu:Fe = 1:1, which was the optimal condition for creating the delafossite CuFeO2 structure. The measured optical bandgap of CuFeO2 was 1.4 eV. The deposited CuFeO2 films were subjected to photoelectrochemical measurements in the cathodic region to investigate their potential application in solar photocatalytic water splitting. The films showed photocatalytic activity, with a photocurrent density of around 70 μA/cm2 (under an incident light irradiation of 62 mW/cm2, AM 1.5 G). The electrochemical properties of the layers were studied using open circuit potential, linear voltammetry, and chronoamperometry. The surface morphology and chemical composition of the layers were analyzed by atomic force microscopy and energy-dispersive x-ray spectroscopy, respectively. The crystalline structure was determined using XRD and Raman spectroscopy. The results of these methods are presented and discussed in this article.","PeriodicalId":17490,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135831336","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yeliz Unutulmazsoy, Dmitry Kalanov, Kyunghwan Oh, Soheil Karimi Aghda, Jürgen W. Gerlach, Nils Braun, Frans Munnik, Andriy Lotnyk, Jochen M. Schneider, André Anders
Pulsed filtered cathodic arc deposition involves formation of energetic multiply charged metal ions, which help to form dense, adherent, and macroparticle-free thin films. Ions possess not only significant kinetic energy, but also potential energy primarily due to their charge, which for cathodic arc plasmas is usually greater than one. While the effects of kinetic ion energy on the growing film are well investigated, the effects of the ions’ potential energy are less known. In the present work, we make a step toward decoupling the contributions of kinetic and potential energies of ions on thin film formation. The potential energy is changed by enhancing the ion charge states via using an external magnetic field at the plasma source. The kinetic energy is adjusted by biasing the arc source (“plasma bias”), which allows us to approximately compensate the differences in kinetic energy, while the substrate and ion energy detector remain at ground. However, application of an external magnetic field also leads to an enhancement of the ion flux and hence the desired complete decoupling of the potential and kinetic energy effects will require further steps. Charge-state-resolved energy distribution functions of ions are measured at the substrate position for different arc source configurations, and thin films are deposited using exactly those configurations. Detailed characterization of the deposited thin films is performed to reveal the correlations of changes in structure with kinetic and potential energies of multiply charged ions. It is observed that the cathode composition (Al:V ratio) strongly affects the formation of the thermodynamically stable wurtzite or the metastable cubic phase. The external magnetic field applied at the arc source is found to greatly alter the plasma and, therefore, to be the primary, easily accessible “tuning knob” to enhance film crystallinity. The effect of “atomic scale heating” provided by the ions’ kinetic and potential energies on the film crystallinity is investigated, and the possibility to deposit crystalline (V,Al)N films without substrate heating is demonstrated. This study shows an approach toward distinguishing the contributions stemming from kinetic and potential energies of ions on the film growth, however, further research is needed to assess and distinguish the additional effect of ion flux intensity (current).
{"title":"Toward decoupling the effects of kinetic and potential ion energies: Ion flux dependent structural properties of thin (V,Al)N films deposited by pulsed filtered cathodic arc","authors":"Yeliz Unutulmazsoy, Dmitry Kalanov, Kyunghwan Oh, Soheil Karimi Aghda, Jürgen W. Gerlach, Nils Braun, Frans Munnik, Andriy Lotnyk, Jochen M. Schneider, André Anders","doi":"10.1116/6.0002927","DOIUrl":"https://doi.org/10.1116/6.0002927","url":null,"abstract":"Pulsed filtered cathodic arc deposition involves formation of energetic multiply charged metal ions, which help to form dense, adherent, and macroparticle-free thin films. Ions possess not only significant kinetic energy, but also potential energy primarily due to their charge, which for cathodic arc plasmas is usually greater than one. While the effects of kinetic ion energy on the growing film are well investigated, the effects of the ions’ potential energy are less known. In the present work, we make a step toward decoupling the contributions of kinetic and potential energies of ions on thin film formation. The potential energy is changed by enhancing the ion charge states via using an external magnetic field at the plasma source. The kinetic energy is adjusted by biasing the arc source (“plasma bias”), which allows us to approximately compensate the differences in kinetic energy, while the substrate and ion energy detector remain at ground. However, application of an external magnetic field also leads to an enhancement of the ion flux and hence the desired complete decoupling of the potential and kinetic energy effects will require further steps. Charge-state-resolved energy distribution functions of ions are measured at the substrate position for different arc source configurations, and thin films are deposited using exactly those configurations. Detailed characterization of the deposited thin films is performed to reveal the correlations of changes in structure with kinetic and potential energies of multiply charged ions. It is observed that the cathode composition (Al:V ratio) strongly affects the formation of the thermodynamically stable wurtzite or the metastable cubic phase. The external magnetic field applied at the arc source is found to greatly alter the plasma and, therefore, to be the primary, easily accessible “tuning knob” to enhance film crystallinity. The effect of “atomic scale heating” provided by the ions’ kinetic and potential energies on the film crystallinity is investigated, and the possibility to deposit crystalline (V,Al)N films without substrate heating is demonstrated. This study shows an approach toward distinguishing the contributions stemming from kinetic and potential energies of ions on the film growth, however, further research is needed to assess and distinguish the additional effect of ion flux intensity (current).","PeriodicalId":17490,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"188 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135895623","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kunyao Jiang, Jingyu Tang, Chengchao Xu, Kelly Xiao, Robert F. Davis, Lisa M. Porter
Atomic resolution scanning/transmission electron microscopy (S/TEM) and energy-dispersive x-ray (EDX) analysis were used to determine the effects of annealing at 800–1000 °C in air on Ga2O3 films grown on (100) MgAl2O4 at 650 °C via metal-organic chemical vapor deposition. Annealing resulted in the diffusion of Mg and Al into the films concomitantly with the transformation of β-Ga2O3 to γ-Ga2O3 solid solutions. The minimum atomic percent of Al + Mg that corresponded with the transformation was ∼4.6 at. %. Analyses of atomic-scale STEM images and EDX profiles revealed that the Al and Mg atoms in the γ-Ga2O3 solid solutions occupied octahedral sites; whereas the Ga atoms occupied tetrahedral sites. These site preferences may account for the stabilization of the γ-Ga2O3 solid solutions.
{"title":"Evolution of <i>β</i>-Ga2O3 to <i> <i>γ</i> </i>-Ga2O3 solid-solution epitaxial films after high-temperature annealing","authors":"Kunyao Jiang, Jingyu Tang, Chengchao Xu, Kelly Xiao, Robert F. Davis, Lisa M. Porter","doi":"10.1116/6.0002962","DOIUrl":"https://doi.org/10.1116/6.0002962","url":null,"abstract":"Atomic resolution scanning/transmission electron microscopy (S/TEM) and energy-dispersive x-ray (EDX) analysis were used to determine the effects of annealing at 800–1000 °C in air on Ga2O3 films grown on (100) MgAl2O4 at 650 °C via metal-organic chemical vapor deposition. Annealing resulted in the diffusion of Mg and Al into the films concomitantly with the transformation of β-Ga2O3 to γ-Ga2O3 solid solutions. The minimum atomic percent of Al + Mg that corresponded with the transformation was ∼4.6 at. %. Analyses of atomic-scale STEM images and EDX profiles revealed that the Al and Mg atoms in the γ-Ga2O3 solid solutions occupied octahedral sites; whereas the Ga atoms occupied tetrahedral sites. These site preferences may account for the stabilization of the γ-Ga2O3 solid solutions.","PeriodicalId":17490,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135831334","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sreejith Nair, Kyle Noordhoek, Dooyong Lee, Christopher J. Bartel, Bharat Jalan
Thin films of elemental metals play a very important role in modern electronic nano-devices as conduction pathways, spacer layers, spin-current generators/detectors, and many other important functionalities. In this work, by exploiting the chemistry of solid metal-organic source precursors, we demonstrate the molecular beam epitaxy synthesis of elemental Ir and Ru metal thin films. The synthesis of these metals is enabled by thermodynamic and kinetic selection of the metal phase as the metal-organic precursor decomposes on the substrate surface. Film growth under different conditions was studied using a combination of in situ and ex situ structural and compositional characterization techniques. The critical role of substrate temperature, oxygen reactivity, and precursor flux in tuning film composition and quality is discussed in the context of precursor adsorption, decomposition, and crystal growth. Computed thermodynamics quantifies the driving force for metal or oxide formation as a function of synthesis conditions and changes in chemical potential. These results indicate that bulk thermodynamics are a plausible origin for the formation of Ir metal at low temperatures, while Ru metal formation is likely mediated by kinetics.
{"title":"Solid-source metal-organic MBE for elemental Ir and Ru films","authors":"Sreejith Nair, Kyle Noordhoek, Dooyong Lee, Christopher J. Bartel, Bharat Jalan","doi":"10.1116/6.0002955","DOIUrl":"https://doi.org/10.1116/6.0002955","url":null,"abstract":"Thin films of elemental metals play a very important role in modern electronic nano-devices as conduction pathways, spacer layers, spin-current generators/detectors, and many other important functionalities. In this work, by exploiting the chemistry of solid metal-organic source precursors, we demonstrate the molecular beam epitaxy synthesis of elemental Ir and Ru metal thin films. The synthesis of these metals is enabled by thermodynamic and kinetic selection of the metal phase as the metal-organic precursor decomposes on the substrate surface. Film growth under different conditions was studied using a combination of in situ and ex situ structural and compositional characterization techniques. The critical role of substrate temperature, oxygen reactivity, and precursor flux in tuning film composition and quality is discussed in the context of precursor adsorption, decomposition, and crystal growth. Computed thermodynamics quantifies the driving force for metal or oxide formation as a function of synthesis conditions and changes in chemical potential. These results indicate that bulk thermodynamics are a plausible origin for the formation of Ir metal at low temperatures, while Ru metal formation is likely mediated by kinetics.","PeriodicalId":17490,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135243702","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Azmain A. Hossain, Haozhe Wang, David S. Catherall, Martin Leung, Harm C. M. Knoops, James R. Renzas, Austin J. Minnich
Microwave loss in superconducting TiN films is attributed to two-level systems in various interfaces arising in part from oxidation and microfabrication-induced damage. Atomic layer etching (ALE) is an emerging subtractive fabrication method which is capable of etching with angstrom-scale etch depth control and potentially less damage. However, while ALE processes for TiN have been reported, they either employ HF vapor, incurring practical complications, or the etch rate lacks the desired control. Furthermore, the superconducting characteristics of the etched films have not been characterized. Here, we report an isotropic plasma-thermal TiN ALE process consisting of sequential exposures to molecular oxygen and an SF6/H2 plasma. For certain ratios of SF6:H2 flow rates, we observe selective etching of TiO2 over TiN, enabling self-limiting etching within a cycle. Etch rates were measured to vary from 1.1 Å/cycle at 150°C to 3.2 Å/cycle at 350°C using ex situ ellipsometry. We demonstrate that the superconducting critical temperature of the etched film does not decrease beyond that expected from the decrease in film thickness, highlighting the low-damage nature of the process. These findings have relevance for applications of TiN in microwave kinetic inductance detectors and superconducting qubits.
{"title":"Isotropic plasma-thermal atomic layer etching of superconducting titanium nitride films using sequential exposures of molecular oxygen and SF6/H2 plasma","authors":"Azmain A. Hossain, Haozhe Wang, David S. Catherall, Martin Leung, Harm C. M. Knoops, James R. Renzas, Austin J. Minnich","doi":"10.1116/6.0002965","DOIUrl":"https://doi.org/10.1116/6.0002965","url":null,"abstract":"Microwave loss in superconducting TiN films is attributed to two-level systems in various interfaces arising in part from oxidation and microfabrication-induced damage. Atomic layer etching (ALE) is an emerging subtractive fabrication method which is capable of etching with angstrom-scale etch depth control and potentially less damage. However, while ALE processes for TiN have been reported, they either employ HF vapor, incurring practical complications, or the etch rate lacks the desired control. Furthermore, the superconducting characteristics of the etched films have not been characterized. Here, we report an isotropic plasma-thermal TiN ALE process consisting of sequential exposures to molecular oxygen and an SF6/H2 plasma. For certain ratios of SF6:H2 flow rates, we observe selective etching of TiO2 over TiN, enabling self-limiting etching within a cycle. Etch rates were measured to vary from 1.1 Å/cycle at 150°C to 3.2 Å/cycle at 350°C using ex situ ellipsometry. We demonstrate that the superconducting critical temperature of the etched film does not decrease beyond that expected from the decrease in film thickness, highlighting the low-damage nature of the process. These findings have relevance for applications of TiN in microwave kinetic inductance detectors and superconducting qubits.","PeriodicalId":17490,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135718546","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Zgheib, L. Berthelot, J. Tranchant, N. Ginot, M.-P. Besland, A. Caillard, T. Minea, A. Rhallabi, P.-Y. Jouan
A high-power impulse magnetron sputtering (HiPIMS) power supply, called e-HiPIMS, has been developed and used to deposit chromium thin films within an argon discharge. This power supply comprises three stages; each can deliver a voltage pulse up to 300 V. The advantage of this power supply is the possibility of tailoring a pulse waveform on the cathode with several voltage levels. This e-HiPIMS can operate in the standard HiPIMS mode (s-HiPIMS) and multipulse HiPIMS mode. Each voltage sequence is independently managed regarding the width, delay, and voltage level. They can all be synchronized, giving the s-HiPIMS, or shifted in time and added to each other. Hence, the idea is to favor a specific ion population compared to others, according to the process needs and the targeted application. A beneficial example used a three-pulse sequence with different voltage levels. The influence of the temporal behavior on the plasma parameters, namely, currents and electron energy, has been studied for each pulse sequence. The results show that the discharge current stays within the same order of magnitude as in the standard HiPIMS. The reference current level can be obtained quickly, adding a short over-pulse, even if its voltage level is relatively low. Furthermore, measurements by the Langmuir probe reveal that a maximum electron density is obtained at 0.2 and 0.6 Pa of argon for a configuration that adds two distinguished voltage-pulse sequences, one between 5 and 15 μs and the other between 20 and 40 μs. It comes out that this e-HiPIMS sequence significantly increases the electron density.
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