Youngsang Kim, Charles H. Ang, Kwissy Ang, S. Chang
Electromigration—a critical failure mode of metal interconnects in integrated circuits—has been exploited for constructing nanometer-sized gaps (or nanogaps, less than a few nanometers) on metallic nanowires. Electromigrated nanogaps have been utilized extensively in the field of nanotechnology and have demonstrated to be an effective platform for electrically accessing small things such as molecules in a device fashion, establishing metal-molecule-metal junctions. These devices allow the study of the electronic transport phenomena through molecules and DNA. Furthermore, electromigrated nanogaps can read out incident electromagnetic fields as an antenna due to the plasmonic excitation on the surface, which is usually maximized in nanogaps. Moreover, structural changes caused by electromigration on metallic nanowires have been leveraged to create single-component resistive switching memories. In this review, we discuss the recent progress and challenges of electromigration methods for a nanogap creation as well as their applications for electronic devices (molecular/DNA devices and resistive switches), thermoelectric energy conversion devices, and photonic devices (nanoantennas).
{"title":"Electromigrated nanogaps: A review on the fabrications and applications","authors":"Youngsang Kim, Charles H. Ang, Kwissy Ang, S. Chang","doi":"10.1116/6.0000866","DOIUrl":"https://doi.org/10.1116/6.0000866","url":null,"abstract":"Electromigration—a critical failure mode of metal interconnects in integrated circuits—has been exploited for constructing nanometer-sized gaps (or nanogaps, less than a few nanometers) on metallic nanowires. Electromigrated nanogaps have been utilized extensively in the field of nanotechnology and have demonstrated to be an effective platform for electrically accessing small things such as molecules in a device fashion, establishing metal-molecule-metal junctions. These devices allow the study of the electronic transport phenomena through molecules and DNA. Furthermore, electromigrated nanogaps can read out incident electromagnetic fields as an antenna due to the plasmonic excitation on the surface, which is usually maximized in nanogaps. Moreover, structural changes caused by electromigration on metallic nanowires have been leveraged to create single-component resistive switching memories. In this review, we discuss the recent progress and challenges of electromigration methods for a nanogap creation as well as their applications for electronic devices (molecular/DNA devices and resistive switches), thermoelectric energy conversion devices, and photonic devices (nanoantennas).","PeriodicalId":17652,"journal":{"name":"Journal of Vacuum Science & Technology. B. Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79376386","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. Edler, A. Schels, J. Biba, W. Hansch, M. Bachmann, F. Düsberg, Marinus Werber, C. Langer, M. Meyer, David von Bergen, A. Pahlke
Silicon field emitter arrays (FEAs) with different tip sizes and quantities were fabricated by saw dicing and anisotropic wet chemical etching by tetramethylammonium hydroxide. The tip is formed by the different etching rates of the crystal facets leading to a sharp pyramid based on {103} planes on the top and a hexadecagon based on {331} and {221} planes on the bottom. Electrical measurements at 10−5 mbar up to 10 μA show good reproducibility for FEAs with the same process parameters and higher uniformity and stability with an increasing number of tips. Constant current measurements at the same conditions and 10 μA show a mean electric field increase of about 0.06(3) V/(μm h) for p-type FEAs with a tip quantity of 3600. The shift increases with lower tip quantity and is higher for n-type FEAs compared to p-type. The degradation during the constant current measurement of n-type samples is found to be partly reversible by heating to 200 °C during emission. In contrast, heating of p-type FEAs induced further degradation instead of a regeneration effect.
{"title":"Silicon field emitters fabricated by dicing-saw and wet-chemical-etching","authors":"S. Edler, A. Schels, J. Biba, W. Hansch, M. Bachmann, F. Düsberg, Marinus Werber, C. Langer, M. Meyer, David von Bergen, A. Pahlke","doi":"10.1116/6.0000466","DOIUrl":"https://doi.org/10.1116/6.0000466","url":null,"abstract":"Silicon field emitter arrays (FEAs) with different tip sizes and quantities were fabricated by saw dicing and anisotropic wet chemical etching by tetramethylammonium hydroxide. The tip is formed by the different etching rates of the crystal facets leading to a sharp pyramid based on {103} planes on the top and a hexadecagon based on {331} and {221} planes on the bottom. Electrical measurements at 10−5 mbar up to 10 μA show good reproducibility for FEAs with the same process parameters and higher uniformity and stability with an increasing number of tips. Constant current measurements at the same conditions and 10 μA show a mean electric field increase of about 0.06(3) V/(μm h) for p-type FEAs with a tip quantity of 3600. The shift increases with lower tip quantity and is higher for n-type FEAs compared to p-type. The degradation during the constant current measurement of n-type samples is found to be partly reversible by heating to 200 °C during emission. In contrast, heating of p-type FEAs induced further degradation instead of a regeneration effect.","PeriodicalId":17652,"journal":{"name":"Journal of Vacuum Science & Technology. B. Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90630015","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}
Dehua Li, Soo-Young Lee, Jin Choi, Seom-Beom Kim, Chan-uk Jeon
Computational lithography is typically based on a model representing the lithographic process where a typical model consists of three components, i.e., line spread function, conversion formula (exposure-to-developing rate conversion), and noise process (exposure fluctuation). In our previous study, a practical approach to modeling the e-beam lithographic process by deriving the three components directly from SEM images was proposed. However, a 2D model of a substrate system was employed; i.e., the exposure variation along the resist-depth dimension was not considered. In this study, the possibility of improving the accuracy of modeling using a 3D model is investigated. The 3D model is iteratively determined by modeling the critical dimension estimated based on the model to those measured in SEM images. This paper describes the 3D modeling approach and new optimization procedures and discusses in detail the results from an extensive simulation for an accuracy analysis of the 3D modeling approach.
{"title":"3D modeling of electron-beam lithographic process from scanning electron microscope images","authors":"Dehua Li, Soo-Young Lee, Jin Choi, Seom-Beom Kim, Chan-uk Jeon","doi":"10.1116/6.0000694","DOIUrl":"https://doi.org/10.1116/6.0000694","url":null,"abstract":"Computational lithography is typically based on a model representing the lithographic process where a typical model consists of three components, i.e., line spread function, conversion formula (exposure-to-developing rate conversion), and noise process (exposure fluctuation). In our previous study, a practical approach to modeling the e-beam lithographic process by deriving the three components directly from SEM images was proposed. However, a 2D model of a substrate system was employed; i.e., the exposure variation along the resist-depth dimension was not considered. In this study, the possibility of improving the accuracy of modeling using a 3D model is investigated. The 3D model is iteratively determined by modeling the critical dimension estimated based on the model to those measured in SEM images. This paper describes the 3D modeling approach and new optimization procedures and discusses in detail the results from an extensive simulation for an accuracy analysis of the 3D modeling approach.","PeriodicalId":17652,"journal":{"name":"Journal of Vacuum Science & Technology. B. Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78719713","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}
We report observation of the piezoresistive effect of β-Ga2O3 Schottky diodes and investigate its application for strain gauge sensors. The Schottky diode-based strain gauge exhibits resistance on the order of 107 Ω, which allows low power applications. A large gauge factor of −201 ± 43 is measured from a Pt/( 2 ¯01) β-Ga2O3 Schottky diode at room temperature, enabling the strain-induced resistance change to be measurable without a Wheatstone bridge. Mechanical exfoliation in the (100) surface produces β-Ga2O3 single crystal thin films, which are more suitable for strain gauge applications than bulk substrates. Owing to the wide bandgap nature, we demonstrate high-temperature operation of strain sensing based on β-Ga2O3 Schottky diodes up to 800 K. The β-Ga2O3 Schottky diodes simultaneously function as temperature sensors, which may enable temperature compensation of strain gauge output.
{"title":"β-Ga2O3 Schottky diodes based strain gauges with high resistance, large gauge factor, and high operating temperature","authors":"Bo-You Liu, Jian V. Li","doi":"10.1116/6.0000776","DOIUrl":"https://doi.org/10.1116/6.0000776","url":null,"abstract":"We report observation of the piezoresistive effect of β-Ga2O3 Schottky diodes and investigate its application for strain gauge sensors. The Schottky diode-based strain gauge exhibits resistance on the order of 107 Ω, which allows low power applications. A large gauge factor of −201 ± 43 is measured from a Pt/( 2 ¯01) β-Ga2O3 Schottky diode at room temperature, enabling the strain-induced resistance change to be measurable without a Wheatstone bridge. Mechanical exfoliation in the (100) surface produces β-Ga2O3 single crystal thin films, which are more suitable for strain gauge applications than bulk substrates. Owing to the wide bandgap nature, we demonstrate high-temperature operation of strain sensing based on β-Ga2O3 Schottky diodes up to 800 K. The β-Ga2O3 Schottky diodes simultaneously function as temperature sensors, which may enable temperature compensation of strain gauge output.","PeriodicalId":17652,"journal":{"name":"Journal of Vacuum Science & Technology. B. Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82573744","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}
Mandy Grube, Benjamin Schille, M. Schirmer, M. Gerngroß, U. Hübner, P. Voigt, S. Brose
The high suitability of hydrogen silsesquioxane (HSQ) as e-beam resist has long been known. Despite its undoubtedly good and reliable properties, HSQ nevertheless proves to be problematic in certain aspects due to its relatively short shelf-life and the small processing window between coating preparation and exposure. We thus intended to optimize the silsesquioxane with respect to a prolonged shelf-life and larger processing window while retaining all advantages like the high silicon content for high etch resistance and high pattern resolution. Our combined knowledge resulted in the development of the hydrogen silsesquioxane-based e-beam resist Medusa 82 with improved characteristics. Medusa 82 can be processed with HSQ standard procedures but allows for a delay of several weeks between layer preparation and exposure under standard conditions. Medusa 82 resist compositions tolerate storage periods of several weeks at room temperature. In addition, we generated and investigated variants of Medusa 82, which offer the possibility for exposure with less energy to cross-link the resist. Furthermore, weaker alkaline developers can be applied. A postexposure bake of these new Medusa 82 variants provides a significant enhancement of sensitivity and contrast. In this context, applications of Medusa 82 in deep to extreme ultraviolet and grayscale lithography are described. The use of glasslike resists with moderate electron beam sensitivity has the potential to reduce the effort and to simplify the manufacturing process of micro-optical devices that traditionally have to be structured in glass surfaces. The transformation process of Medusa 82 into a glasslike material involves an e-beam exposure, a thermal treatment, or a combination of both. Moreover, the adjustable contrast and sensitivity enable grayscale lithography. Different e-beam exposures trigger a different cross-linking degree within the layer, resulting in height variations after development. A postexposure bake step induces further cross-linking and a complete conversion into silicon oxide.
{"title":"Medusa 82—Hydrogen silsesquioxane based high sensitivity negative-tone resist with long shelf-life and grayscale lithography capability","authors":"Mandy Grube, Benjamin Schille, M. Schirmer, M. Gerngroß, U. Hübner, P. Voigt, S. Brose","doi":"10.1116/6.0000542","DOIUrl":"https://doi.org/10.1116/6.0000542","url":null,"abstract":"The high suitability of hydrogen silsesquioxane (HSQ) as e-beam resist has long been known. Despite its undoubtedly good and reliable properties, HSQ nevertheless proves to be problematic in certain aspects due to its relatively short shelf-life and the small processing window between coating preparation and exposure. We thus intended to optimize the silsesquioxane with respect to a prolonged shelf-life and larger processing window while retaining all advantages like the high silicon content for high etch resistance and high pattern resolution. Our combined knowledge resulted in the development of the hydrogen silsesquioxane-based e-beam resist Medusa 82 with improved characteristics. Medusa 82 can be processed with HSQ standard procedures but allows for a delay of several weeks between layer preparation and exposure under standard conditions. Medusa 82 resist compositions tolerate storage periods of several weeks at room temperature. In addition, we generated and investigated variants of Medusa 82, which offer the possibility for exposure with less energy to cross-link the resist. Furthermore, weaker alkaline developers can be applied. A postexposure bake of these new Medusa 82 variants provides a significant enhancement of sensitivity and contrast. In this context, applications of Medusa 82 in deep to extreme ultraviolet and grayscale lithography are described. The use of glasslike resists with moderate electron beam sensitivity has the potential to reduce the effort and to simplify the manufacturing process of micro-optical devices that traditionally have to be structured in glass surfaces. The transformation process of Medusa 82 into a glasslike material involves an e-beam exposure, a thermal treatment, or a combination of both. Moreover, the adjustable contrast and sensitivity enable grayscale lithography. Different e-beam exposures trigger a different cross-linking degree within the layer, resulting in height variations after development. A postexposure bake step induces further cross-linking and a complete conversion into silicon oxide.","PeriodicalId":17652,"journal":{"name":"Journal of Vacuum Science & Technology. B. Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90386898","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}
Michael Titze, D. Perry, Elizabeth Auden, J. Pacheco, John B. S. Abraham, E. Bielejec
We present a new Li source for focused ion beam applications. Based on an AuSi eutectic alloy, Li is added as an impurity to minimize effects from degradation when exposed to air. We show the source is stable over the course of an hour and spot sizes ≲ 10 nm can be achieved. The Li beam can achieve hundreds of nanometer ranges in semiconductors with minimal damage being generated along the path length. The source performance is evaluated through a high-resolution ion beam induced charge collection experiment on an Si-based detector. Further application of the source for ion beam analysis is numerically explored; the example investigated is based on probing a semiconductor heterostructure through a Rutherford backscattering experiment, where the Li beam can reveal information that is inaccessible with either low energy or high energy He projectiles used as probes.
{"title":"Lithium source for focused ion beam implantation and analysis","authors":"Michael Titze, D. Perry, Elizabeth Auden, J. Pacheco, John B. S. Abraham, E. Bielejec","doi":"10.1116/6.0000645","DOIUrl":"https://doi.org/10.1116/6.0000645","url":null,"abstract":"We present a new Li source for focused ion beam applications. Based on an AuSi eutectic alloy, Li is added as an impurity to minimize effects from degradation when exposed to air. We show the source is stable over the course of an hour and spot sizes ≲ 10 nm can be achieved. The Li beam can achieve hundreds of nanometer ranges in semiconductors with minimal damage being generated along the path length. The source performance is evaluated through a high-resolution ion beam induced charge collection experiment on an Si-based detector. Further application of the source for ion beam analysis is numerically explored; the example investigated is based on probing a semiconductor heterostructure through a Rutherford backscattering experiment, where the Li beam can reveal information that is inaccessible with either low energy or high energy He projectiles used as probes.","PeriodicalId":17652,"journal":{"name":"Journal of Vacuum Science & Technology. B. Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76859309","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. Kimura, H. Yoshida, H. Miyazaki, Takuya Fujimoto, A. Ogino
We observed the polarity-dependent thermionic emission (TE) and conversion characteristics of n-type GaN-based cathodes with Cs adsorbed on their surfaces. TE current from the surface of an n-GaN sample with N-polarity was 0.18 mA at an applied anode voltage of 30 V at 500 °C. This TE current was markedly higher than that of a sample with Ga-polarity, which had a corresponding TE current of 0.063 mA. We consider the N-polarity with spontaneous polarization to be the cause of the increase in electron density at the Cs/n-GaN interface. TE current was also detected from both samples with Ga- and N-polarity even when the applied anode voltage was 0 V or lower, indicating the presence of thermionic conversion characteristics. From the viewpoint of a thermionic converter, the electromotive force for TE was 0.12 V higher when using the N-polarity n-GaN cathode compared with the Ga-polarity cathode. The short-circuit currents at 500 °C were 4.8 and 0.97 μA for the sample with N-polarity and the one with Ga-polarity, respectively.
{"title":"Surface polarity dependence of thermionic emission and conversion characteristics of n-type GaN cathodes","authors":"S. Kimura, H. Yoshida, H. Miyazaki, Takuya Fujimoto, A. Ogino","doi":"10.1116/6.0000710","DOIUrl":"https://doi.org/10.1116/6.0000710","url":null,"abstract":"We observed the polarity-dependent thermionic emission (TE) and conversion characteristics of n-type GaN-based cathodes with Cs adsorbed on their surfaces. TE current from the surface of an n-GaN sample with N-polarity was 0.18 mA at an applied anode voltage of 30 V at 500 °C. This TE current was markedly higher than that of a sample with Ga-polarity, which had a corresponding TE current of 0.063 mA. We consider the N-polarity with spontaneous polarization to be the cause of the increase in electron density at the Cs/n-GaN interface. TE current was also detected from both samples with Ga- and N-polarity even when the applied anode voltage was 0 V or lower, indicating the presence of thermionic conversion characteristics. From the viewpoint of a thermionic converter, the electromotive force for TE was 0.12 V higher when using the N-polarity n-GaN cathode compared with the Ga-polarity cathode. The short-circuit currents at 500 °C were 4.8 and 0.97 μA for the sample with N-polarity and the one with Ga-polarity, respectively.","PeriodicalId":17652,"journal":{"name":"Journal of Vacuum Science & Technology. B. Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89739566","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}
Hong‐cheng Li, Yu-Rong Liu, Geng Kuiwei, Weijing Wu, R. Yao, P. Lai
ZnO thin film transistor with high-k NbLaO/SiO2 bilayer gate dielectric was fabricated by sputtering, and the temperature dependence of the electrical properties of the device was investigated in the temperature range of 293–353 K for clarifying thermally activated carrier generation and carrier transport mechanisms in the conducting channel. With the increase in the temperature, the transfer curve shifts toward the negative gate voltage direction with a negative shift of the threshold voltage, an increase in the off-state current and the subthreshold slope, and a significant increase in carrier mobility. The decrease in the threshold voltage is originated from the formation of oxygen vacancy and the release of free electrons in the ZnO channel, and the formation energy can be estimated to be approximately 0.3 eV. In both subthreshold and above-threshold regimes, the temperature dependence of the drain current shows Arrhenius-type dependence, and the activation energy is around 0.94 eV for a gate voltage of 2 V, reducing with the increase in the gate voltage. The temperature dependence of the ZnO film resistance also exhibits an Arrhenius-type behavior, indicating that the thermal activation conduction process is the dominant conduction mechanism in the ZnO film. Two types of thermal activation conduction processes are observed in the 303–373 K temperature range. This is explained in terms of the existence of two types of deep donors that are consecutively excited to the conduction band as the temperature increases.
{"title":"Temperature dependence of the electrical characteristics of ZnO thin film transistor with high-k NbLaO gate dielectric","authors":"Hong‐cheng Li, Yu-Rong Liu, Geng Kuiwei, Weijing Wu, R. Yao, P. Lai","doi":"10.1116/6.0000522","DOIUrl":"https://doi.org/10.1116/6.0000522","url":null,"abstract":"ZnO thin film transistor with high-k NbLaO/SiO2 bilayer gate dielectric was fabricated by sputtering, and the temperature dependence of the electrical properties of the device was investigated in the temperature range of 293–353 K for clarifying thermally activated carrier generation and carrier transport mechanisms in the conducting channel. With the increase in the temperature, the transfer curve shifts toward the negative gate voltage direction with a negative shift of the threshold voltage, an increase in the off-state current and the subthreshold slope, and a significant increase in carrier mobility. The decrease in the threshold voltage is originated from the formation of oxygen vacancy and the release of free electrons in the ZnO channel, and the formation energy can be estimated to be approximately 0.3 eV. In both subthreshold and above-threshold regimes, the temperature dependence of the drain current shows Arrhenius-type dependence, and the activation energy is around 0.94 eV for a gate voltage of 2 V, reducing with the increase in the gate voltage. The temperature dependence of the ZnO film resistance also exhibits an Arrhenius-type behavior, indicating that the thermal activation conduction process is the dominant conduction mechanism in the ZnO film. Two types of thermal activation conduction processes are observed in the 303–373 K temperature range. This is explained in terms of the existence of two types of deep donors that are consecutively excited to the conduction band as the temperature increases.","PeriodicalId":17652,"journal":{"name":"Journal of Vacuum Science & Technology. B. Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78287805","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}
Our study refers to the highly stretchable elastomer PDMS (polydimethylsiloxane), a material used with a wide range of applications. Its basic mechanical properties can be tuned, e.g., by varying the curing conditions; moreover, its surface properties can be tuned by modification techniques. We modified our PDMS by irradiating the samples with an excimer lamp at 172 nm. Such a treatment hardens the elastomer at the surface, and it becomes silicalike; the sample changes to a “quasi” two-layer system with a graded interface. When such samples are stretched, surface cracks occur beyond a critical strain. The increase of crack length with increasing strain is evaluated by means of video screenshots. The impact of the curing conditions is addressed by analyzing samples prepared at different cross-linking temperatures, resulting in differing bulk properties but similar surface properties. Crack length and crack velocity are evaluated with each sample based on single randomly chosen cracks. The results are discussed on the basis of theoretical concepts for channeling cracks in multilayer systems with polymeric substrates. Typically, with applications, random cracks should develop at high strain only and, if present, should propagate slowly along the surface but not into the depth of the sample. Our investigation shows that the mechanical material properties of the substrate are vital with respect to such stable cracking, rather than the surface properties. In particular, the curing conditions chosen for the substrate are essential to reduce cracking, a fact less regarded with applications so far.
{"title":"Insights from evaluation of surface cracks in surface-hardened polydimethylsiloxane by means of video analysis","authors":"Miriam Schröer, H. Scheer","doi":"10.1116/6.0000550","DOIUrl":"https://doi.org/10.1116/6.0000550","url":null,"abstract":"Our study refers to the highly stretchable elastomer PDMS (polydimethylsiloxane), a material used with a wide range of applications. Its basic mechanical properties can be tuned, e.g., by varying the curing conditions; moreover, its surface properties can be tuned by modification techniques. We modified our PDMS by irradiating the samples with an excimer lamp at 172 nm. Such a treatment hardens the elastomer at the surface, and it becomes silicalike; the sample changes to a “quasi” two-layer system with a graded interface. When such samples are stretched, surface cracks occur beyond a critical strain. The increase of crack length with increasing strain is evaluated by means of video screenshots. The impact of the curing conditions is addressed by analyzing samples prepared at different cross-linking temperatures, resulting in differing bulk properties but similar surface properties. Crack length and crack velocity are evaluated with each sample based on single randomly chosen cracks. The results are discussed on the basis of theoretical concepts for channeling cracks in multilayer systems with polymeric substrates. Typically, with applications, random cracks should develop at high strain only and, if present, should propagate slowly along the surface but not into the depth of the sample. Our investigation shows that the mechanical material properties of the substrate are vital with respect to such stable cracking, rather than the surface properties. In particular, the curing conditions chosen for the substrate are essential to reduce cracking, a fact less regarded with applications so far.","PeriodicalId":17652,"journal":{"name":"Journal of Vacuum Science & Technology. B. Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85254354","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}
Planar metal-insulator-semiconductor capacitors are fabricated on native gallium nitride substrates with different gate dielectrics, namely, silicon dioxide, silicon nitride, and aluminum oxide. The leakage current was measured to determine their robustness regarding electrical breakdown. Hysteresis effects were evaluated for the different gate dielectrics and for the substrate and the epitaxial surface. A gate-first process with a gate contact made from poly-crystalline silicon was compared to a gate-last process with a sputtered aluminum gate. The former showed superior robustness against electrical breakdown with a dielectric breakdown field strength of ≈ 9 MV/cm, which was found to be mostly independent of temperature in the range of 250–450 K. Furthermore, gate oxide traps were estimated by means of stress/recovery gate current transient measurements to confirm field strength limits for high lifetime requirements. Based on the various measurements, silicon dioxide emerged as the best choice regarding breakdown robustness and hysteresis effects. A limit for the dielectric field strength of 3–4 MV/cm is proposed to avoid short- and long-term damage of the dielectric layer.
{"title":"Gate engineering in metal insulator semiconductor capacitors on native gallium nitride substrates for applications with high lifetime requirements","authors":"Kevin Dannecker, J. Baringhaus","doi":"10.1116/6.0000440","DOIUrl":"https://doi.org/10.1116/6.0000440","url":null,"abstract":"Planar metal-insulator-semiconductor capacitors are fabricated on native gallium nitride substrates with different gate dielectrics, namely, silicon dioxide, silicon nitride, and aluminum oxide. The leakage current was measured to determine their robustness regarding electrical breakdown. Hysteresis effects were evaluated for the different gate dielectrics and for the substrate and the epitaxial surface. A gate-first process with a gate contact made from poly-crystalline silicon was compared to a gate-last process with a sputtered aluminum gate. The former showed superior robustness against electrical breakdown with a dielectric breakdown field strength of ≈ 9 MV/cm, which was found to be mostly independent of temperature in the range of 250–450 K. Furthermore, gate oxide traps were estimated by means of stress/recovery gate current transient measurements to confirm field strength limits for high lifetime requirements. Based on the various measurements, silicon dioxide emerged as the best choice regarding breakdown robustness and hysteresis effects. A limit for the dielectric field strength of 3–4 MV/cm is proposed to avoid short- and long-term damage of the dielectric layer.","PeriodicalId":17652,"journal":{"name":"Journal of Vacuum Science & Technology. B. Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91515456","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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