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  • American Vacuum Society  (10)
  • Physics  (10)
  • 1
    Online Resource
    Online Resource
    Differences between Li, Na, and K migration in thin SiO2 films during ToF-SIMS O2+ depth profiling
    American Vacuum Society ; 2018
    In:  Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena Vol. 36, No. 3 ( 2018-05-01)
    Details
    In: Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena, American Vacuum Society, Vol. 36, No. 3 ( 2018-05-01)
    Abstract: Distribution of alkali metals within thin insulating films as recorded by time of flight secondary ion mass spectrometry (ToF-SIMS) dual beam depth profiling using O2+ as the sputter projectile is usually exhibiting artifacts. Positive charges appear on the sample surface upon impact of sputter ions. This leads to large electric fields within the insulator, causing alkali metal ions to migrate toward the interface with an adjacent conductive layer. Additionally, the sample temperature is a main contributor to migration processes. By varying the temperature during measurements, the mobility of alkali metal ions can be regulated. This report addresses the difference between Li, Na, and K migration during ToF-SIMS depth profiling. It is shown that there is no significant difference between Li and Na migration within a thermally grown SiO2 layer on Si. K migration, however, is reduced, leading to less distorted depth profiles. At elevated temperatures above T = 200 °C, there is the onset to a second artifact, resulting in surface segregation of K and superposing the migration artifact in ToF-SIMS depth profiles. It is shown that the use of low energy electron flooding has an important role in the occurrence of alkali metal ion surface segregation.
    Type of Medium: Online Resource
    ISSN: 2166-2746 , 2166-2754
    URL: Article
    DOI: 10.1116/1.5019659
    RVK:
    UA 4922
    Language: English
    Publisher: American Vacuum Society
    Publication Date: 2018
    detail.hit.zdb_id: 3117331-7
    detail.hit.zdb_id: 1475429-0
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  • 2
    Online Resource
    Online Resource
    Normally-off operating GaN-based pseudovertical MOSFETs with MBE grown source region
    American Vacuum Society ; 2018
    In:  Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena Vol. 36, No. 2 ( 2018-03-01)
    Details
    In: Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena, American Vacuum Society, Vol. 36, No. 2 ( 2018-03-01)
    Abstract: In this report, the operation of a normally-off vertical gallium nitride (GaN) metal-oxide field effect transistor with a threshold voltage of 5 V is demonstrated. A crucial step during device fabrication is the formation of the highly n-doped source layer. The authors infer that the use of molecular beam epitaxy (MBE) is highly beneficial for suppressing diffusion of the magnesium (Mg) p-type dopants from the body layer grown by metal-organic vapor phase epitaxy into the source cap. Repassivation of the previously activated Mg acceptors by a hydrogen out-diffusion treatment is suppressed in the ultrahigh vacuum growth environment. Structural and electrical data indicate that the defect density of the GaN substrate is currently limiting device performance much more compared to other effects like varying surface morphology resulting from fluctuations in III/N stoichiometry during the MBE growth.
    Type of Medium: Online Resource
    ISSN: 2166-2746 , 2166-2754
    URL: Article
    DOI: 10.1116/1.5017291
    RVK:
    UA 4922
    Language: English
    Publisher: American Vacuum Society
    Publication Date: 2018
    detail.hit.zdb_id: 3117331-7
    detail.hit.zdb_id: 1475429-0
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  • 3
    Online Resource
    Online Resource
    Ultraviolet transmittance of SU-8 photoresist and its importance in multi-wavelength photolithography
    American Vacuum Society ; 2018
    In:  Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena Vol. 36, No. 5 ( 2018-09-01)
    Details
    In: Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena, American Vacuum Society, Vol. 36, No. 5 ( 2018-09-01)
    Abstract: The transmission properties of SU-8 photoresist in the ultraviolet (UV) range are reported for resist thicknesses between 1 and 150 μm in the soft-baked state prior to lithographic exposure. Multiple transmission wavelengths in the UV region between 200 and 400 nm are found to be suitable candidates for self-limiting exposure and thus polymerization depth. This enables a novel method to realize microarchitectures via standard photolithographic techniques. Examples of three dimensional hollow polymer microarchitectures are presented to demonstrate the advantages of this method. The coefficient of attenuation is calculated using Beer–Lambert’s principle for different resist thicknesses.
    Type of Medium: Online Resource
    ISSN: 2166-2746 , 2166-2754
    URL: Article
    DOI: 10.1116/1.5033996
    RVK:
    UA 4922
    Language: English
    Publisher: American Vacuum Society
    Publication Date: 2018
    detail.hit.zdb_id: 3117331-7
    detail.hit.zdb_id: 1475429-0
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  • 4
    Online Resource
    Online Resource
    Correlating elemental compositions and charge carrier profiles in ultra-pure GaN/AlGaN stacks grown by molecular beam epitaxy
    American Vacuum Society ; 2023
    In:  Journal of Vacuum Science & Technology A Vol. 41, No. 4 ( 2023-07-01)
    Details
    In: Journal of Vacuum Science & Technology A, American Vacuum Society, Vol. 41, No. 4 ( 2023-07-01)
    Abstract: Inconsistencies in the concentrations of unintentional donor impurities and free charge carriers in GaN/AlGaN layer stacks hosting a two-dimensional electron gas (2DEG) can be attributed to the measurement procedure and solely depend on the way in which the free charge carrier concentration is extracted. Particularly, when the 2DEG acts as the bottom electrode in capacitance versus voltage measurements, unphysically low concentrations of free charges are calculated. This originates from the depletion of the 2DEG and the accompanying disappearance of the bottom electrode. It is shown that, for the case of a defined (non-vanishing) bottom electrode, the levels of donor impurities and resulting free charges consistently match.
    Type of Medium: Online Resource
    ISSN: 0734-2101 , 1520-8559
    URL: Article
    DOI: 10.1116/6.0002652
    RVK:
    UA 4921
    Language: English
    Publisher: American Vacuum Society
    Publication Date: 2023
    detail.hit.zdb_id: 1475424-1
    detail.hit.zdb_id: 797704-9
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  • 5
    Online Resource
    Online Resource
    Control of unintentional oxygen incorporation in GaN
    American Vacuum Society ; 2017
    In:  Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena Vol. 35, No. 2 ( 2017-03-01)
    Details
    In: Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena, American Vacuum Society, Vol. 35, No. 2 ( 2017-03-01)
    Abstract: The impact of growth temperature on the unintentional oxygen incorporation in GaN and AlGaN grown by molecular beam epitaxy and the consequences for electrical and optical properties are investigated. In particular, transistor switching characteristics, magneto-transport traces, and photoluminescence spectra of samples grown around 600 and 665 °C are compared. It is found that the incorporation of unintentional oxygen in GaN and Al0.1Ga0.9N is reduced by 1 order of magnitude upon increasing the growth temperature by ∼60 °C. A growth temperature of 665 °C results in an oxygen background concentration of 1 × 1017 cm−3 and simultaneously in electrically insulating GaN material.
    Type of Medium: Online Resource
    ISSN: 2166-2746 , 2166-2754
    URL: Article
    DOI: 10.1116/1.4975925
    RVK:
    UA 4922
    Language: English
    Publisher: American Vacuum Society
    Publication Date: 2017
    detail.hit.zdb_id: 3117331-7
    detail.hit.zdb_id: 1475429-0
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  • 6
    Online Resource
    Online Resource
    Detailed simulation study of embedded SiGe and Si:C source/drain stressors in nanoscaled silicon on insulator metal oxide semiconductor field effect transistors
    American Vacuum Society ; 2010
    In:  Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena Vol. 28, No. 1 ( 2010-01-01), p. C1G12-C1G17
    Details
    In: Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena, American Vacuum Society, Vol. 28, No. 1 ( 2010-01-01), p. C1G12-C1G17
    Abstract: Strained silicon techniques have become an indispensable technology feature, enabling the momentum of semiconductor scaling. Embedded silicon-germanium (eSiGe) is already widely adopted in the industry and delivers outstanding p-metal oxide semiconductor field effect transistor (MOSFET) performance improvements. The counterpart for n-MOSFET is embedded silicon-carbon (eSi:C). However, n-MOSFET performance improvement is much more difficult to achieve with eSi:C due to the challenging process integration. In this study, detailed TCAD simulations are employed to compare the efficiency of eSiGe and eSi:C stressors and to estimate their potential for performance enhancements in future nanoscaled devices with gate lengths down to 20nm. It is found that eSiGe as a stressor is superior to eSi:C in deeply scaled and highly strained devices due to its easier process integration, reduced parasitic resistance, and nonlinear effects in the silicon band structure, favoring hole mobility enhancement at high strain levels.
    Type of Medium: Online Resource
    ISSN: 2166-2746 , 2166-2754
    URL: Article
    DOI: 10.1116/1.3258631
    RVK:
    UA 4922
    Language: English
    Publisher: American Vacuum Society
    Publication Date: 2010
    detail.hit.zdb_id: 3117331-7
    detail.hit.zdb_id: 1475429-0
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  • 7
    Online Resource
    Online Resource
    Intrinsic defects at TiO2(110) surfaces studied with scanning tunneling microscopy
    American Vacuum Society ; 1996
    In:  Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena Vol. 14, No. 2 ( 1996-03-01), p. 961-965
    Details
    In: Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena, American Vacuum Society, Vol. 14, No. 2 ( 1996-03-01), p. 961-965
    Abstract: Intrinsic defects of the nearly stoichiometric (110) surface of TiO2 have been studied by means of scanning tunneling microscopy. Temperature treatment at 870≤T≤1070 K in ultrahigh vacuum induces changes of the orientation of single steps. Line defects along [001] and oxygen vacancies are formed simultaneously as predominant surface defects under these conditions. Atomically resolved scanning tunneling microscopy images make it possible to determine their geometric structures. Simple structural models are derived to explain the high stability of electrostatically neutral [001] single steps and [001] line defects at TiO2(110).
    Type of Medium: Online Resource
    ISSN: 1071-1023 , 1520-8567
    URL: Article
    DOI: 10.1116/1.589184
    RVK:
    UA 4922
    Language: English
    Publisher: American Vacuum Society
    Publication Date: 1996
    detail.hit.zdb_id: 3117331-7
    detail.hit.zdb_id: 3117333-0
    detail.hit.zdb_id: 1475429-0
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  • 8
    Online Resource
    Online Resource
    Atomic layer deposition onto fabrics of carbon and silicon carbide fibers: Preparation of multilayers comprising alumina, titania-furfuryl alcohol hybrid, and titanium phosphate
    American Vacuum Society ; 2021
    In:  Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films Vol. 39, No. 5 ( 2021-09-01)
    Details
    In: Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, American Vacuum Society, Vol. 39, No. 5 ( 2021-09-01)
    Abstract: High temperature-resistant fabrics can be used as a reinforcement structure in ceramic matrix composites. They often need a coating for oxidation protection and mechanical decoupling from the matrix. Atomic layer deposition (ALD) provides very thin conformal coatings even deep down into complex or porous structures and thus might be a suitable technique for this purpose. Carbon fiber fabrics (size 300 mm × 80 mm) and SiC fiber fabrics (size 400 mm × 80 mm) were coated using ALD with a multilayer system: a first layer made of 320 cycles of alumina (Al2O3) deposition, a second layer made of 142 cycles of titania-furfuryl alcohol hybrid (TiO2-FFA), and a third layer made of 360 cycles of titanium phosphate (TixPOy). Scanning electron microscopy reveals that the coatings are uniform and that the thickness of each layer is almost independent of the place in the reactor while coating. Appearance and thickness do not show any dependence on the type of fiber used as a substrate. Energy dispersive x-ray spectroscopy confirmed the expected elemental composition of each layer. Thermogravimetric analysis under oxidizing environment revealed that the first layer increases the onset temperature of fiber oxidation significantly, while the following two layers improve the oxidative protection only to a much smaller degree. Varying the geometry and size of the sample holder and especially the stacking of several fabric specimens on top of each other allowed increasing the total area of coated fabric up to 560 cm2 per batch. It was demonstrated that four-layered fiber coatings could be obtained with high uniformity even on these much more complicated geometries.
    Type of Medium: Online Resource
    ISSN: 0734-2101 , 1520-8559
    URL: Article
    DOI: 10.1116/6.0001193
    RVK:
    UA 4921
    Language: English
    Publisher: American Vacuum Society
    Publication Date: 2021
    detail.hit.zdb_id: 1475424-1
    detail.hit.zdb_id: 797704-9
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  • 9
    Online Resource
    Online Resource
    Magneto-optical confirmation of Landau level splitting in a GaN/AlGaN 2DEG grown on bulk GaN
    American Vacuum Society ; 2019
    In:  Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena Vol. 37, No. 2 ( 2019-03-01)
    Details
    In: Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena, American Vacuum Society, Vol. 37, No. 2 ( 2019-03-01)
    Abstract: Landau level splitting in a two-dimensional electron gas (2DEG) confined in an ultrapure GaN/AlGaN heterostructure grown by molecular beam epitaxy on bulk GaN is verified spectroscopically. The Landau level fan reconstructed from magneto-photoluminescence (PL) data yields an effective mass of 0.24m0 for the 2D electrons. Narrow excitonic PL line widths  & lt; 100 μeV, an atomically flat surface of the layer stack, as well as the absence of the 2DEG in the dark environment, are important ancillary experimental findings while focusing on magneto-PL investigations of the heterostructure. Simultaneously recorded Shubnikov-de Haas and magneto-PL intensity oscillations under steady UV illumination exhibit an identical frequency and allow for two independent ways of determining the 2D density.
    Type of Medium: Online Resource
    ISSN: 2166-2746 , 2166-2754
    URL: Article
    DOI: 10.1116/1.5088927
    RVK:
    UA 4922
    Language: English
    Publisher: American Vacuum Society
    Publication Date: 2019
    detail.hit.zdb_id: 3117331-7
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  • 10
    Online Resource
    Online Resource
    Quantum and transport lifetimes in optically induced GaN/AlGaN 2DEGs grown on bulk GaN
    American Vacuum Society ; 2020
    In:  Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena Vol. 38, No. 4 ( 2020-07-01)
    Details
    In: Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena, American Vacuum Society, Vol. 38, No. 4 ( 2020-07-01)
    Abstract: A two-dimensional electron gas (2DEG) is absent in ultrapure GaN/Al0.06Ga0.94N heterostructures grown by molecular beam epitaxy on bulk GaN at 300 K and in the dark. However, such a 2DEG can be generated by UV illumination and persists at low temperature after blanking the light. Under steady UV illumination as well as under persistence conditions, pronounced quantum transport with Shubnikov–de Haas oscillations commencing below 2 T is observed. The low temperature 2DEG mobility amounts to only ∼20 000 cm2/V s, which is much lower than predicted for the dominant scattering mechanisms in GaN/AlGaN heterostructures grown on GaN with low threading dislocation density. A rather small ratio of the transport and quantum lifetimes τt/τq of ∼10 points at elastic scattering events limiting both the transport and quantum lifetimes.
    Type of Medium: Online Resource
    ISSN: 2166-2746 , 2166-2754
    URL: Article
    DOI: 10.1116/1.5145198
    RVK:
    UA 4922
    Language: English
    Publisher: American Vacuum Society
    Publication Date: 2020
    detail.hit.zdb_id: 3117331-7
    detail.hit.zdb_id: 1475429-0
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