Chengwu Zhang, Tuo Gao, Donal Sheets, J. Hancock, J. Tresback, B. Willis
Nanogaps in metallic nanostructures produce local field enhancements with potential applications in surface enhanced spectroscopy, solar energy conversion, and photocatalysis. Atomic layer deposition is applied as a conformal coating to modify nanogap sizes and tune the optical properties of plasmonic dimer arrays with sub-10 nm nanogaps. Nanostructures are fabricated using layers of gold and palladium to combine features of plasmonics and area-selective atomic layer deposition, where copper metal is deposited on palladium-covered surfaces. Direct measurements of optical extinction for successive smaller nanogaps and thicker copper coatings show that spectral features become broadened at first due to heating-induced shape changes but subsequently sharpen as copper coatings form on palladium structures. Furthermore, longitudinal resonances of plasmonic dimers blue shift for thin coatings due to heating and decreasing aspect ratio, but thicker coatings lead to red shifts due to narrowing nanogaps. Together, these results show that area-selective atomic layer deposition is a promising tool for achieving large area arrays of plasmonic dimers with sub-10 nm nanogaps.
{"title":"Tunable and scalable fabrication of plasmonic dimer arrays with sub-10 nm nanogaps by area-selective atomic layer deposition","authors":"Chengwu Zhang, Tuo Gao, Donal Sheets, J. Hancock, J. Tresback, B. Willis","doi":"10.1116/6.0001205","DOIUrl":"https://doi.org/10.1116/6.0001205","url":null,"abstract":"Nanogaps in metallic nanostructures produce local field enhancements with potential applications in surface enhanced spectroscopy, solar energy conversion, and photocatalysis. Atomic layer deposition is applied as a conformal coating to modify nanogap sizes and tune the optical properties of plasmonic dimer arrays with sub-10 nm nanogaps. Nanostructures are fabricated using layers of gold and palladium to combine features of plasmonics and area-selective atomic layer deposition, where copper metal is deposited on palladium-covered surfaces. Direct measurements of optical extinction for successive smaller nanogaps and thicker copper coatings show that spectral features become broadened at first due to heating-induced shape changes but subsequently sharpen as copper coatings form on palladium structures. Furthermore, longitudinal resonances of plasmonic dimers blue shift for thin coatings due to heating and decreasing aspect ratio, but thicker coatings lead to red shifts due to narrowing nanogaps. Together, these results show that area-selective atomic layer deposition is a promising tool for achieving large area arrays of plasmonic dimers with sub-10 nm nanogaps.","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":"2021-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72742308","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}
Pavani Vamsi Krishna Nittala, Karthika Haridas, Shivam Nigam, Saba Tasneem, P. Sen
This paper presents the process flow optimizations for the 3D stacking of thin silicon dies. This process is developed for the postfabrication 3D integration technique, which can be used by 3D packaging and heterogenous or hybrid integration fabs. Bonding of the thin silicon layers is optimized by reducing the epoxy thickness. Further, a detailed of set experiments were used to characterize the stress in the thin silicon films. Finally, a hybrid process flow is demonstrated for achieving finer interconnect linewidths of 10 μm. The 3D stacking approach is based on the bonding of thin dies followed by SU-8 planarization. Vias are opened in the planarization layer using lithography. The interconnection methodology fills the SU-8 polymer vias with inkjet-printed silver. Printing the interconnect lines using the standard inkjet printer limits the linewidth to ∼100 μm. To address this, a hybrid process is developed to scale the interconnect line widths. Along with interconnects in the multilayer stack, we demonstrate a minimum line width and spacing of 10 μm and a via diameter of 10 μm.
{"title":"Characterization and optimization of bonding and interconnect technology for 3D stacking thin dies","authors":"Pavani Vamsi Krishna Nittala, Karthika Haridas, Shivam Nigam, Saba Tasneem, P. Sen","doi":"10.1116/6.0001160","DOIUrl":"https://doi.org/10.1116/6.0001160","url":null,"abstract":"This paper presents the process flow optimizations for the 3D stacking of thin silicon dies. This process is developed for the postfabrication 3D integration technique, which can be used by 3D packaging and heterogenous or hybrid integration fabs. Bonding of the thin silicon layers is optimized by reducing the epoxy thickness. Further, a detailed of set experiments were used to characterize the stress in the thin silicon films. Finally, a hybrid process flow is demonstrated for achieving finer interconnect linewidths of 10 μm. The 3D stacking approach is based on the bonding of thin dies followed by SU-8 planarization. Vias are opened in the planarization layer using lithography. The interconnection methodology fills the SU-8 polymer vias with inkjet-printed silver. Printing the interconnect lines using the standard inkjet printer limits the linewidth to ∼100 μm. To address this, a hybrid process is developed to scale the interconnect line widths. Along with interconnects in the multilayer stack, we demonstrate a minimum line width and spacing of 10 μm and a via diameter of 10 μm.","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":"2021-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74944209","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}
Refractive axicons are conically shaped optical devices that are capable of generating nondiffracting Bessel-like beams over extended depths-of-focus (DOFs). In addition to the substantially longer DOF compared to those produced by parabolic focusing lenses, the axicons can generate beams with better resolution for the same form-factor of the optical element, e.g., its diameter and sag height. These properties make the axicons useful in numerous applications in imaging, particle trapping, and many others. Miniaturized refractive axicons or microaxicons are challenging to realize in hard substrates due to the lack of sufficiently precise and rapid fabrication technologies. Here, we report on the rapid fabrication of ultradeep microaxicons in lithium niobate using high-current focused Xe ion beam milling. Microaxicons with 230- μm diameter with ultradeep sag heights between 21 and 48 μm were milled using 200 nA of beam current. Furthermore, the microaxicons were milled in single-crystal lithium niobate—a material with a high refractive index of >2.2 but which inertness makes it a challenging material in microfabrication. The performance of the lenses was characterized by mapping the transmitted intensity at different positions. The measured spot sizes of the produced beams are in excellent agreement with the theoretical expectations and range from 750 down to 250 nm ( ∼λ/2) beam spot size for the shallowest and the deepest microaxicons in this study, respectively. The corresponding DOFs are from 500 down to ∼50 μm for the ultradeep microaxicon. The results verify the applicability of high-current milling with a focused Xe ion beam for the fabrication of high-performance optical elements.
{"title":"Ultradeep microaxicons in lithium niobate by focused Xe ion beam milling","authors":"S. Gorelick, A. Marco","doi":"10.1116/6.0001232","DOIUrl":"https://doi.org/10.1116/6.0001232","url":null,"abstract":"Refractive axicons are conically shaped optical devices that are capable of generating nondiffracting Bessel-like beams over extended depths-of-focus (DOFs). In addition to the substantially longer DOF compared to those produced by parabolic focusing lenses, the axicons can generate beams with better resolution for the same form-factor of the optical element, e.g., its diameter and sag height. These properties make the axicons useful in numerous applications in imaging, particle trapping, and many others. Miniaturized refractive axicons or microaxicons are challenging to realize in hard substrates due to the lack of sufficiently precise and rapid fabrication technologies. Here, we report on the rapid fabrication of ultradeep microaxicons in lithium niobate using high-current focused Xe ion beam milling. Microaxicons with 230- μm diameter with ultradeep sag heights between 21 and 48 μm were milled using 200 nA of beam current. Furthermore, the microaxicons were milled in single-crystal lithium niobate—a material with a high refractive index of >2.2 but which inertness makes it a challenging material in microfabrication. The performance of the lenses was characterized by mapping the transmitted intensity at different positions. The measured spot sizes of the produced beams are in excellent agreement with the theoretical expectations and range from 750 down to 250 nm ( ∼λ/2) beam spot size for the shallowest and the deepest microaxicons in this study, respectively. The corresponding DOFs are from 500 down to ∼50 μm for the ultradeep microaxicon. The results verify the applicability of high-current milling with a focused Xe ion beam for the fabrication of high-performance optical elements.","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":"2021-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81145647","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. Mukhopadhyay, Hridibrata Pal, Sameer Narang, Chenyu Guo, Jichun Ye, Wei Guo, B. Sarkar
In this work, we report on a self-powered ultraviolet photodiode realized using lateral polarity structure (LPS) GaN films. The opposite nature of the polarization charge yields different barrier heights at the standard Ni/Au Schottky contact interface of N-polar and III-polar GaN films. As a result, a natural nonzero built-in potential is obtained in the LPS GaN photodiode, which showed photoresponsivity even at 0 V applied bias. The self-powered mechanism inside such an LPS GaN photodiode is discussed in detail by a combination of simulation prediction and experimental validation. Furthermore, a variation in the doping concentration of the adjacent III- and N-polar GaN domain is shown to improve the photoresponsivity compared to the conventional III-polar photodiode. Thus, this work validates that the LPS GaN photodiode is a promising candidate to realize self-powered operation and a general design rule for the photodiode with in-plane built-in potential.
{"title":"Self-powered ultraviolet photodiode based on lateral polarity structure GaN films","authors":"S. Mukhopadhyay, Hridibrata Pal, Sameer Narang, Chenyu Guo, Jichun Ye, Wei Guo, B. Sarkar","doi":"10.1116/6.0001196","DOIUrl":"https://doi.org/10.1116/6.0001196","url":null,"abstract":"In this work, we report on a self-powered ultraviolet photodiode realized using lateral polarity structure (LPS) GaN films. The opposite nature of the polarization charge yields different barrier heights at the standard Ni/Au Schottky contact interface of N-polar and III-polar GaN films. As a result, a natural nonzero built-in potential is obtained in the LPS GaN photodiode, which showed photoresponsivity even at 0 V applied bias. The self-powered mechanism inside such an LPS GaN photodiode is discussed in detail by a combination of simulation prediction and experimental validation. Furthermore, a variation in the doping concentration of the adjacent III- and N-polar GaN domain is shown to improve the photoresponsivity compared to the conventional III-polar photodiode. Thus, this work validates that the LPS GaN photodiode is a promising candidate to realize self-powered operation and a general design rule for the photodiode with in-plane built-in potential.","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":"2021-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78324817","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}
B. Dodson, Guohai Chen, Robert C. Davis, R. Vanfleet
Several electrical devices are formed by growing vertically aligned carbon nanotube (CNT) structures directly on a substrate. In order to attain high aspect ratio CNT forest growths, a support layer for the CNT catalyst, usually alumina, is generally required. In many cases, it has been found that current can pass from a conductive substrate, across the alumina support layer, and through the CNTs with minimal resistance. This is surprising in the cases where alumina is used because alumina has a resistivity of ρ>1014 Ω cm. This paper explores the mechanism responsible for current being able to cross the alumina support layer with minimal resistance following CNT growth by using scanning transmission electron microscopy imaging, energy dispersive x-ray spectroscopy, secondary ion mass spectroscopy, and two-point current-voltage (I-V) measurements. Through these methods, it is determined that exposure to the carbonaceous gas used during the CNT growth process is primarily responsible for this phenomenon.
{"title":"Electrical conductivity across the alumina support layer following carbon nanotube growth","authors":"B. Dodson, Guohai Chen, Robert C. Davis, R. Vanfleet","doi":"10.1116/6.0001115","DOIUrl":"https://doi.org/10.1116/6.0001115","url":null,"abstract":"Several electrical devices are formed by growing vertically aligned carbon nanotube (CNT) structures directly on a substrate. In order to attain high aspect ratio CNT forest growths, a support layer for the CNT catalyst, usually alumina, is generally required. In many cases, it has been found that current can pass from a conductive substrate, across the alumina support layer, and through the CNTs with minimal resistance. This is surprising in the cases where alumina is used because alumina has a resistivity of ρ>1014 Ω cm. This paper explores the mechanism responsible for current being able to cross the alumina support layer with minimal resistance following CNT growth by using scanning transmission electron microscopy imaging, energy dispersive x-ray spectroscopy, secondary ion mass spectroscopy, and two-point current-voltage (I-V) measurements. Through these methods, it is determined that exposure to the carbonaceous gas used during the CNT growth process is primarily responsible for this phenomenon.","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":"2021-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73442434","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. Bessouet, S. Lemettre, Charlotte Kutyla, A. Bosseboeuf, P. Coste, T. Sauvage, H. Lecoq, Olivier Wendling, A. Bellamy, Piyush Jagtap, S. Escoubas, C. Guichet, O. Thomas, J. Moulin
Yttrium, titanium, and yttrium-titanium getter thin films were elaborated on silicon by coevaporation in ultrahigh vacuum. Y-Ti films exhibit nanometric crystallites size (18–35 nm) leading to a very high grain boundary density, which is a favorable microstructure for activation at low temperature. The yttrium content in Y-Ti alloys influences grain size, resistance against room temperature oxidation, and gettering performance for oxygen. Y-Ti films with an yttrium content higher than 30% show strong oxygen sorption during annealing at low temperature (<300 °C). After 1 h of annealing at 250 °C, it was estimated that the yttrium-based getter films can trap between 0.2 and 0.5 μmol of oxygen per cm2, while no oxygen sorption was detected for a single metal titanium film. This makes Y-Ti getter alloys attractive candidates for the packaging of MEMS under vacuum with a low bonding temperature.
{"title":"Electrical and ion beam analyses of yttrium and yttrium-titanium getter thin films oxidation","authors":"C. Bessouet, S. Lemettre, Charlotte Kutyla, A. Bosseboeuf, P. Coste, T. Sauvage, H. Lecoq, Olivier Wendling, A. Bellamy, Piyush Jagtap, S. Escoubas, C. Guichet, O. Thomas, J. Moulin","doi":"10.1116/6.0001084","DOIUrl":"https://doi.org/10.1116/6.0001084","url":null,"abstract":"Yttrium, titanium, and yttrium-titanium getter thin films were elaborated on silicon by coevaporation in ultrahigh vacuum. Y-Ti films exhibit nanometric crystallites size (18–35 nm) leading to a very high grain boundary density, which is a favorable microstructure for activation at low temperature. The yttrium content in Y-Ti alloys influences grain size, resistance against room temperature oxidation, and gettering performance for oxygen. Y-Ti films with an yttrium content higher than 30% show strong oxygen sorption during annealing at low temperature (<300 °C). After 1 h of annealing at 250 °C, it was estimated that the yttrium-based getter films can trap between 0.2 and 0.5 μmol of oxygen per cm2, while no oxygen sorption was detected for a single metal titanium film. This makes Y-Ti getter alloys attractive candidates for the packaging of MEMS under vacuum with a low bonding temperature.","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":"2021-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79478072","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}
Hantian Gao, S. Muralidharan, R. Karim, Lei R. Cao, K. Leedy, Hongping Zhao, S. Rajan, D. Look, L. Brillson
The gallium vacancy is one of the dominant native point defects in β-Ga2O3, one that, together with its complexes, can have a major effect on free carrier densities and transport in this wide bandgap semiconductor. We used a combination of depth-resolved cathodoluminescence spectroscopy and surface photovoltage spectroscopy to identify the optical and energy-level properties of these defects as well as how their defect densities and spatial distributions vary with neutron irradiation and temperature-dependent-forming gas anneals. These studies reveal optical signatures that align closely with theoretical energy-level predictions. Likewise, our optical techniques reveal variations in these defect densities that are consistent with hydrogen passivation of gallium vacancies as a function of temperature and depth from the free Ga2O3 surface. These techniques can help guide the understanding and control of dominant native point defects in Ga2O3.
{"title":"Depth-resolved cathodoluminescence and surface photovoltage spectroscopies of gallium vacancies in β-Ga2O3 with neutron irradiation and forming gas anneals","authors":"Hantian Gao, S. Muralidharan, R. Karim, Lei R. Cao, K. Leedy, Hongping Zhao, S. Rajan, D. Look, L. Brillson","doi":"10.1116/6.0001240","DOIUrl":"https://doi.org/10.1116/6.0001240","url":null,"abstract":"The gallium vacancy is one of the dominant native point defects in β-Ga2O3, one that, together with its complexes, can have a major effect on free carrier densities and transport in this wide bandgap semiconductor. We used a combination of depth-resolved cathodoluminescence spectroscopy and surface photovoltage spectroscopy to identify the optical and energy-level properties of these defects as well as how their defect densities and spatial distributions vary with neutron irradiation and temperature-dependent-forming gas anneals. These studies reveal optical signatures that align closely with theoretical energy-level predictions. Likewise, our optical techniques reveal variations in these defect densities that are consistent with hydrogen passivation of gallium vacancies as a function of temperature and depth from the free Ga2O3 surface. These techniques can help guide the understanding and control of dominant native point defects in Ga2O3.","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":"2021-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88000210","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The research of photoelectric memristors has been gaining momentum in recent years. Although resistive memory synaptic devices are usually electrically controlled, an opto-electronic one would certainly be advantageous. A light-responsive structure can extend the functionality of such devices and allow for coupling of light and electrical signals in the implementation of neuromorphic systems. This paper presents a detailed analysis of a transparent, bilayer synaptic device, capable of hybrid photonic and electronic response with multideck, erase functionality. Such steplike operation may allow for more degrees of freedom in the implementation of artificial vision systems based on these incremental conductance changes. Multilevel operation is demonstrated under different illumination intensities and functional methodologies (i.e., irradiation schemes). Statistical data are also presented to give a better foundation for this suggested functionality. Finally, the underlying physical mechanisms are discussed, supported by ultrahigh-vacuum conductive atomic force microscope measurements over a dedicated lateral test structure.
{"title":"Multideck light-induced reset in a transparent bilayer synaptic device","authors":"D. Berco, D. Ang","doi":"10.1116/6.0001186","DOIUrl":"https://doi.org/10.1116/6.0001186","url":null,"abstract":"The research of photoelectric memristors has been gaining momentum in recent years. Although resistive memory synaptic devices are usually electrically controlled, an opto-electronic one would certainly be advantageous. A light-responsive structure can extend the functionality of such devices and allow for coupling of light and electrical signals in the implementation of neuromorphic systems. This paper presents a detailed analysis of a transparent, bilayer synaptic device, capable of hybrid photonic and electronic response with multideck, erase functionality. Such steplike operation may allow for more degrees of freedom in the implementation of artificial vision systems based on these incremental conductance changes. Multilevel operation is demonstrated under different illumination intensities and functional methodologies (i.e., irradiation schemes). Statistical data are also presented to give a better foundation for this suggested functionality. Finally, the underlying physical mechanisms are discussed, supported by ultrahigh-vacuum conductive atomic force microscope measurements over a dedicated lateral test structure.","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":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88921369","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 atomic layer deposition (ALD), thin layers of materials are deposited on a substrate with atomic layer precision in the vertical direction. The ability to control layer growth in the lateral direction as well is expected to greatly increase the potential of ALD as a path to the bottom-up additive fabrication of electronic devices like solar panels and organic light-emitting diode displays. We explore the possibility of controlling the lateral growth by modifying the temperature profile on the substrate using, for instance, pulsed lasers. This maskless technique keeps the majority of the substrate at a low temperature suppressing one of the chemical half-reactions, while in a small, localized area, the substrate is heated, which allows the reaction to proceed at a higher rate. We test this idea with course-grained computational models that model the control of the temperature by various illumination protocols and simulate the nucleation and growth of the initial monolayer within this inhomogeneous temperature distribution. Our results suggest that the location and the extent of deposition can, in principle, be localized and controlled and address operational regimes in which a thin conducting line may be obtained.
{"title":"Modeling the initial monolayer formation in thermally localized surface deposition","authors":"Bart de Braaf, C. Rops, C. Storm","doi":"10.1116/6.0001098","DOIUrl":"https://doi.org/10.1116/6.0001098","url":null,"abstract":"In atomic layer deposition (ALD), thin layers of materials are deposited on a substrate with atomic layer precision in the vertical direction. The ability to control layer growth in the lateral direction as well is expected to greatly increase the potential of ALD as a path to the bottom-up additive fabrication of electronic devices like solar panels and organic light-emitting diode displays. We explore the possibility of controlling the lateral growth by modifying the temperature profile on the substrate using, for instance, pulsed lasers. This maskless technique keeps the majority of the substrate at a low temperature suppressing one of the chemical half-reactions, while in a small, localized area, the substrate is heated, which allows the reaction to proceed at a higher rate. We test this idea with course-grained computational models that model the control of the temperature by various illumination protocols and simulate the nucleation and growth of the initial monolayer within this inhomogeneous temperature distribution. Our results suggest that the location and the extent of deposition can, in principle, be localized and controlled and address operational regimes in which a thin conducting line may be obtained.","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":"2021-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74871417","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}
Runming Tao, Tingting Tan, Hua Zhang, Meng Qingdai, G. Zha
Antimony selenide (Sb2Se3) is regarded as an excellent photovoltaic absorber material due to its suitable bandgap, large light absorption coefficient, abundant raw material reserves, and environmental friendliness. However, the commonly used rapid thermal evaporation strategy for deposition of Sb2Se3 films results in low film quality, which is undesirable from the perspective of photovoltaic performance. Herein, we fabricate highly efficient and stable Sb2Se3 solar cells via a close-space sublimation (CSS) process, which allows separate control of the source and substrate temperatures, leading to high-quality thin films and better solar cell performance. Four growth patterns of Sb2Se3 thin films are optimized by controlling the source temperature of CSS. It is found that the Sb2Se3 thin film prepared at 475 °C has the best crystallinity, smoothest surface, and best density. Moreover, solar cells based on ZnO/Sb2Se3 thin films can achieve maximum efficiency with VOC of 0.312 V, JSC of 27.91 mA/cm2, fill fact of 41.35%, and power conversion efficiency of 3.61%. The performance of the devices was not adversely affected by the air environment, and thus, they were shown to exhibit appropriate stability.
{"title":"Sb2Se3 solar cells fabricated via close-space sublimation","authors":"Runming Tao, Tingting Tan, Hua Zhang, Meng Qingdai, G. Zha","doi":"10.1116/6.0001034","DOIUrl":"https://doi.org/10.1116/6.0001034","url":null,"abstract":"Antimony selenide (Sb2Se3) is regarded as an excellent photovoltaic absorber material due to its suitable bandgap, large light absorption coefficient, abundant raw material reserves, and environmental friendliness. However, the commonly used rapid thermal evaporation strategy for deposition of Sb2Se3 films results in low film quality, which is undesirable from the perspective of photovoltaic performance. Herein, we fabricate highly efficient and stable Sb2Se3 solar cells via a close-space sublimation (CSS) process, which allows separate control of the source and substrate temperatures, leading to high-quality thin films and better solar cell performance. Four growth patterns of Sb2Se3 thin films are optimized by controlling the source temperature of CSS. It is found that the Sb2Se3 thin film prepared at 475 °C has the best crystallinity, smoothest surface, and best density. Moreover, solar cells based on ZnO/Sb2Se3 thin films can achieve maximum efficiency with VOC of 0.312 V, JSC of 27.91 mA/cm2, fill fact of 41.35%, and power conversion efficiency of 3.61%. The performance of the devices was not adversely affected by the air environment, and thus, they were shown to exhibit appropriate stability.","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":"2021-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85298695","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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