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Academic literature on the topic 'Superlattices'

Author: Grafiati

Published: 4 June 2021

Last updated: 1 June 2024

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Journal articles on the topic "Superlattices"

1

Fullerton, Eric E., Ivan K. Schuller, and Y. Bruynseraede. "Quantitative X-Ray Diffraction From Superlattices." MRS Bulletin 17, no. 12 (December 1992): 33–38. http://dx.doi.org/10.1557/s0883769400046935.

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The physical properties of superlattices have been the subject of considerable interest because a wide range of phenomena associated with very thin films, interfaces, and coupling effects can be studied. Recent areas of activity in metallic superlattices include antiferromagnetic coupling of ferromagnetic layers across nonmagnetic spacer layers, giant magnetoresistance, magnetic surface anisotropy, low-dimensional superconductivity, and anomalous mechanical properties. All of these phenomena are strongly affected by the chemical and physical properties of the individual layers and by the superlattice structure. Therefore, a detailed understanding of the properties of superlattices requires a nondestructive, quantitative determination of the superlattice structure.Because superlattices are not in thermodynamic equilibrium, their structure is sensitive to preparation methods and growth conditions. A dramatic example of superlattice structural dependence on growth conditions is shown in Figure 1, for sputtered Nb/Si superlattices. Increasing the Ar pressure during sputtering decreases the kinetic energy of the deposited atoms, thereby changing their surface mobility, and thus altering growth dynamics. Figure 1 shows the low-angle x-ray diffraction and cross-sectional transmission electron microscopy (TEM) images of [Nb(35 Å)/Si(25 Å)]40, superlattices sputtered in, respectively, 3 and 15 mTorr of Ar. The TEM image of the 3 mTorr superlattice clearly shows the smooth and continuous layering across the entire cross section of the image (≈5 μm). This is characteristic of sputtered metal/semiconductor superlattices used for x-ray optics.

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2

Hansen, Monica, Amber C. Abare, Peter Kozodoy, Thomas M. Katona, Michael D. Craven, Jim S. Speck, Umesh K. Mishra, Larry A. Coldren, and Steven P. DenBaars. "Effect Of AlGaN/GaN Strained Layer Superlattice Period On InGaN MQW Laser Diodes." MRS Internet Journal of Nitride Semiconductor Research 5, S1 (2000): 14–19. http://dx.doi.org/10.1557/s1092578300004026.

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AlGaN/GaN strained layer superlattices have been employed in the cladding layers of InGaN multi-quantum well laser diodes grown by metalorganic chemical vapor deposition (MOCVD). Superlattices have been investigated for strain relief of the cladding layer, as well as an enhanced hole concentration, which is more than ten times the value obtained for bulk AlGaN films. Laser diodes with strained layer superlattices as cladding layers were shown to have superior structural and electrical properties compared to laser diodes with bulk AlGaN cladding layers. As the period of the strained layer superlattices is decreased, the threshold voltage, as well as the threshold current density, is decreased. The resistance to vertical conduction through p-type superlattices with increasing superlattice period is not offset by the increase in hole concentration for increasing superlattice spacing, resulting in higher voltages.

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3

Weng, Hsu Kai, Akira Nagakubo, Hideyuki Watanabe, and Hirotsugu Ogi. "Lattice thermal conductivity in isotope diamond asymmetric superlattices." Japanese Journal of Applied Physics 61, SG (March 10, 2022): SG1004. http://dx.doi.org/10.35848/1347-4065/ac4304.

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Abstract We study the lattice thermal conductivity of isotope diamond superlattices consisting of 12C and 13C diamond layers at various superlattice periods. It is found that the thermal conductivity of a superlattice is significantly deduced from that of pure diamond because of the reduction of the phonon group velocity near the folded Brillouin zone. The results show that asymmetric superlattices with a different number of layers of 12C and 13C diamonds exhibit higher thermal conductivity than symmetric superlattices even with the same superlattice period, and we find that this can be explained by the trade-off between the effects of phonon specific heat and phonon group velocity. Furthermore, impurities and imperfect superlattice structures are also found to significantly reduce the thermal conductivity, suggesting that these effects can be exploited to control the thermal conductivity over a wide range.

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Antropov, N. О., and Е. А. Kravtsov. "Neutron Reflectometry in Superlattices with Strongly Absorbing Rare-Earth Metals (Gd, Dy)." Поверхность. Рентгеновские, синхротронные и нейтронные исследования, no. 8 (August 1, 2023): 11–15. http://dx.doi.org/10.31857/s1028096023070038.

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Polarized neutron reflectometry was used to study Dy/Gd superlattices with different ratios of Dy and Gd layer thicknesses: 1 : 1, 2 : 1, 3 : 1. It has been experimentally shown that the formation of helical magnetic ordering in Dy layers with a period incommensurate with the period of the superlattice appears as a magnetic superlattice reflection, which is forbidden for structural reasons at a ratio of the thicknesses of the Dy and Gd layers 1 : 1. Otherwise, the formation of helical magnetic ordering has little effect on the shape of the neutron reflectometry curves. Thus, the optimization of the structure of rare-earth superlattices for the neutron reflectometry experiment makes it possible to detect helical magnetic ordering in superlattices with a period incommensurate with the structural superlattice ordering.

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Yu, Yixuan, Avni Jain, Adrien Guillaussier, Vikas Reddy Voggu, Thomas M. Truskett, Detlef-M. Smilgies, and Brian A. Korgel. "Nanocrystal superlattices that exhibit improved order on heating: an example of inverse melting?" Faraday Discussions 181 (2015): 181–92. http://dx.doi.org/10.1039/c5fd00006h.

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Grazing incidence small angle X-ray scattering (GISAXS) measurements reveal that superlattices of 1.7 nm diameter, gold (Au) nanocrystals capped with octadecanethiol become significantly more ordered when heated to moderate temperatures (50–60 °C). This enhancement in order is reversible and the superlattice returns to its initially disordered structure when cooled back to room temperature. Disorder–order transition temperatures were estimated from the GISAXS data using the Hansen–Verlet criterion. Differential scanning calorimetry (DSC) measurements of the superlattices exhibited exotherms (associated with disordering during cooling) and endotherms (associated with ordering during heating) near the transition temperatures. The superlattice transition temperatures also correspond approximately to the melting and solidification points of octadecanethiol. Therefore, it appears that a change in capping ligand packing that occurs upon ligand melting underlies the structural transition of the superlattices. We liken the heat-induced ordering of the superlattices to an inverse melting transition.

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Kabalan, Amal A., and Pritpal Singh. "CdTe/PbTe Superlattice Modeling and Fabrication for Solar Cells Applications." Journal of Nano Research 48 (July 2017): 125–37. http://dx.doi.org/10.4028/www.scientific.net/jnanor.48.125.

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Tuning the bandgap of superlattice structures creates devices with unique optical, electronic and mechanical properties. Designing solar cells with superlattice structures increases the range of light energy absorbed from the solar spectrum in the device. A superlattice is a nanostructure composed of alternating thin layers of two materials. The thickness of the constituent materials alters the optical bandgap of the superlattice. This paper discusses a mathematical model which computes the effective bandgap of a CdTe/PbTe superlattice based on a given thickness of the CdTe and PbTe films. The output of this model is verified by fabricating superlattices with different thickness and measuring their effective bandgaps. The electrochemical atomic layer deposition method is used to fabricate the superlattice structures. The advantage of this method over other vacuum techniques is that it is inexpensive and operates at room temperature. This paper also discusses a method to mitigate the lattice mismatch between the substrate and the superlattice. The optical bandgaps, crystallinity, grain size and chemical composition of the structures are measured using a spectrometer, diffractometer, transmission electron microscope and scanning electron microscope, respectively. The bandgaps of the fabricated superlattices were in agreement with the simulated values. This model can be used for designing the bandgaps of superlattices which can be incorporated in solar cells.

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7

Islam, Md Tanvirul, Xinkang Chen, Tedi Kujofsa, and John E. Ayers. "Chirped Superlattices as Adjustable Strain Platforms for Metamorphic Semiconductor Devices." International Journal of High Speed Electronics and Systems 27, no. 01n02 (March 2018): 1840009. http://dx.doi.org/10.1142/s0129156418400098.

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Chirped superlattices are of interest as buffer layers in metamorphic semiconductor device structures, because they can combine the mismatch accommodating properties of compositionally-graded layers with the dislocation filtering properties of superlattices. Important practical aspects of the chirped superlattice as a buffer layer are the surface strain and surface in-plane lattice constant. In this work two basic types of InGaAs/GaAs chirped superlattice buffers have been studied. In design I (composition modulated), the average composition is varied by modulating the composition of one of the two layers in the superlattice period, but the individual layer thicknesses were fixed. In design II (thickness modulated), the individual layer thicknesses were modulated, but the compositions were fixed. In this paper the surface strain and surface in-plane lattice constant for these chirped superlattices are presented as functions of the top composition and period for each of these basic designs.

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Zhao, Lu, Lijuan Zhang, Houfu Song, Hongda Du, Junqiao Wu, Feiyu Kang, and Bo Sun. "Incoherent phonon transport dominates heat conduction across van der Waals superlattices." Applied Physics Letters 121, no. 2 (July 11, 2022): 022201. http://dx.doi.org/10.1063/5.0096861.

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Heat conduction mechanisms in superlattices could be different across different types of interfaces. Van der Waals superlattices are structures physically assembled through weak van der Waals interactions by design and may host properties beyond the traditional superlattices limited by lattice matching and processing compatibility, offering a different type of interface. In this work, natural van der Waals (SnS)1.17(NbS2)n superlattices are synthesized, and their thermal conductivities are measured by time-domain thermoreflectance as a function of interface density. Our results show that heat conduction of (SnS)1.17(NbS2)n superlattices is dominated by interface scattering when the coherent length of phonons is larger than the superlattice period, indicating that incoherent phonon transport dominates through-plane heat conduction in van der Waals superlattices even when the period is atomically thin and abrupt, in contrast to conventional superlattices. Our findings provide valuable insights into the understanding of the thermal behavior of van der Waals superlattices and devise approaches for effective thermal management of superlattices depending on the distinct types of interfaces.

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Kim, Jin O., Jan D. Achenbach, Meenam Shinn, and Scott A. Barnett. "Effective Elastic Constants of Superlattice Films Measured by Line-Focus Acoustic Microscopy." Journal of Engineering Materials and Technology 117, no. 4 (October 1, 1995): 395–401. http://dx.doi.org/10.1115/1.2804732.

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The effective elastic constants of single-crystal nitride superlattice films have been determined by calculation and by measurement methods. The calculation method uses formulas to calculate the effective elastic constants of superlattices from the measured elastic constants of the constituent layers. The calculated effective elastic constants are tested by comparing the corresponding surface acoustic wave (SAW) velocities calculated for thin-film/substrate systems with the corresponding SAW velocities measured by line-focus acoustic microscopy (LFAM). The measurement method determines the effective elastic constants of the superlattices directly from the SAW velocity dispersion data measured by LFAM. Two kinds of superlattice films are considered: one has relatively flat and sharp interfaces between layers, and the other has rough interfaces with interdiffusion. The calculation method has yielded very good results for the superlattices with flat and sharp interfaces but not for the superlattices with rough interfaces. The measurement method yields results for both kinds, with the restriction that the constituent layers have similar crystal symmetries.

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Sidorkin, Alexander, Lolita Nesterenko, Yaovi Gagou, Pierre Saint-Gregoire, Eugeniy Vorotnikov, and Nadezhda Popravko. "Dielectric Properties and Switching Processes of Barium Titanate–Barium Zirconate Ferroelectric Superlattices." Materials 11, no. 8 (August 14, 2018): 1436. http://dx.doi.org/10.3390/ma11081436.

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This article is devoted to the investigation of the dielectric and repolarization properties of barium zirconate and barium titanate BaZrO3/BaTiO3 superlattices with a period of 13.322 nm on a monocrystal magnesium oxide (MgO) substrate. Synthesized superlattices demonstrated a ferroelectric phase transition at a temperature of approximately 393 °C, which is far higher than the Curie temperature of BaTiO3 thin films and bulk samples. The dielectric permittivity of the superlattice reached more than 104 at maximum. As the electric field frequency increased, the dielectric constant of the studied superlattice decreased over the entire study temperature range, but position of the maximum dielectric constant remained the same with changing frequency. The temperature dependence of the inverse dielectric permittivity 1/ε(T) for the studied samples shows that, in the investigated superlattice, both Curie–Weiss law and the law of “two” were followed. Additionally, the ε(T) dependences showed practically no temperature hysteresis with heating and cooling. Samples of synthesized superlattices had a relatively small internal bias field, which was directed from the superlattice towards the substrate.

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Dissertations / Theses on the topic "Superlattices"

1

Deans, Mark Edward. "Phonons in superlattices." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254406.

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Hadizad, M. Reza. "Lattice dynamics of superlattices." Thesis, University of Essex, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292758.

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Rajakarunanayake, Yasantha Nirmal McGill T. C. McGill T. C. "Optical properties of Si-Ge superlattices and wide band gap II-VI superlattices /." Diss., Pasadena, Calif. : California Institute of Technology, 1991. http://resolver.caltech.edu/CaltechETD:etd-07122007-074702.

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Müggenburg, Jan. "Ion beam analysis of metallic vanadium superlattices : Ion beam analysis of metallic vanadium superlattices." Thesis, Uppsala universitet, Tillämpad kärnfysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-328067.

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Evans, S. D. "Langmuir-Blodgett superlattices incorporating porphyrins." Thesis, Lancaster University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235169.

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Pulsford, Nicolas J. "Optical studies of semicondutor superlattices." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257905.

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7

Chen, Peixuan. "Thermal transport through SiGe superlattices." Doctoral thesis, Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-159170.

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Understanding thermal transport in nanoscale is important for developing nanostructured thermolelectric materials and for heat management in nanoelectronic devices. This dissertation is devoted to understand thermal transport through SiGe based superlattices. First, we systematically studied the cross-plane thermal conductivity of SiGe superlattices by varying the thickness of Si(Ge) spacers thickness. The observed additive character of thermal resistance of the SiGe nanodot/planar layers allows us to engineer the thermal conductivity by varying the interface distance down to ~1.5 nm. Si-Ge intermixing driven by Ge surface segregation is crucial for achieving highly diffusive phonon scattering at the interfaces. By comparing the thermal conductivity of nanodot Ge/Si superlattices with variable nanodot density and superlattices with only wetting layers, we find that the effect of nanodots is comparable with that produced by planar wetting layers. This is attributed to the shallow morphology and further flattening of SiGe nanodots during overgrowth with Si. Finally, the experiments show that the interface effect on phonon transport can be weakened and even eliminated by reducing the interface distance or by enhancing Si-Ge intermixing around the interfaces by post-growth annealing. The results presented in this dissertation are expected to be relevant to applications requiring optimization of thermal transport for heat management and for the development of thermoelectric materials and devices based on superlattice structures
Verständnis des thermischen Transport auf Nanoskala ist sowohl grundlegend für die Entwicklung nanostrukturierter Materialien, als auch für Temperaturkontrolle in nanoelektronischen Bauteilen. Diese Dissertation widmet sich der Erforschung des thermischen Transports durch SiGe basierenden Übergittern. Variationen, der Si(Ge) Schichtdicken, wurden zur systematischen Untersuchung der Normalkomponente zur Wachstumsrichtung der Wärmeleitfähigkeit, von SiGe Übergittern, genutzt. Die Beobachtung des additiven Charakters, des thermischen Widerstands, der SiGe Schichten, mit oder ohne Inselwachstum, ermöglicht die Erstellung von Strukturen mit bestimmter Wärmeleitfähigkeiten durch die Variation der Schichtdicken bis zu einer Minimaldistanz zweier Schichtübergänge von ~1.5nm. Die Ge Segregation führt zu einer Vermischung, von Si und Ge, welche eine essentielle Rolle zur diffusen Phononenstreuung spielt. Unsere Untersuchungen, von planaren Übergittern und Übergittern mit variabler Inseldichte, zeigen, dass Inseln und planare Schichten zu einer vergleichbaren Reduktion, der Wärmeleitfähigkeit, führen. Diese Beobachtung lässt sich, sowohl auf die flache Morphologie als auch die Abplattung der SiGe Inseln, aufgrund der Überwachsung mit Si, zurückführen. Die Experimente zeigen außerdem, dass sich der Barriereneffekt, der Schichtgrenzen, durch Reduktion der Schichtabstände und durch verstärkte Vermischung im Bereich der Schichtgrenzen, durch Erhitzung, eliminieren lässt. Die präsentierten Messungen sind sowohl, für die Entwicklung jener Bauteile, die eine Optimierung des thermischen Transports oder Temperaturmanagment erfordern, als auch von thermoelektrischen Matieralien und Bauteilen, basierend auf Übergittern, relevant

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8

Chen, Peixuan. "Thermal transport through SiGe superlattices." Doctoral thesis, Universitätsverlag der Technischen Universität Chemnitz, 2014. https://monarch.qucosa.de/id/qucosa%3A20177.

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Understanding thermal transport in nanoscale is important for developing nanostructured thermolelectric materials and for heat management in nanoelectronic devices. This dissertation is devoted to understand thermal transport through SiGe based superlattices. First, we systematically studied the cross-plane thermal conductivity of SiGe superlattices by varying the thickness of Si(Ge) spacers thickness. The observed additive character of thermal resistance of the SiGe nanodot/planar layers allows us to engineer the thermal conductivity by varying the interface distance down to ~1.5 nm. Si-Ge intermixing driven by Ge surface segregation is crucial for achieving highly diffusive phonon scattering at the interfaces. By comparing the thermal conductivity of nanodot Ge/Si superlattices with variable nanodot density and superlattices with only wetting layers, we find that the effect of nanodots is comparable with that produced by planar wetting layers. This is attributed to the shallow morphology and further flattening of SiGe nanodots during overgrowth with Si. Finally, the experiments show that the interface effect on phonon transport can be weakened and even eliminated by reducing the interface distance or by enhancing Si-Ge intermixing around the interfaces by post-growth annealing. The results presented in this dissertation are expected to be relevant to applications requiring optimization of thermal transport for heat management and for the development of thermoelectric materials and devices based on superlattice structures.
Verständnis des thermischen Transport auf Nanoskala ist sowohl grundlegend für die Entwicklung nanostrukturierter Materialien, als auch für Temperaturkontrolle in nanoelektronischen Bauteilen. Diese Dissertation widmet sich der Erforschung des thermischen Transports durch SiGe basierenden Übergittern. Variationen, der Si(Ge) Schichtdicken, wurden zur systematischen Untersuchung der Normalkomponente zur Wachstumsrichtung der Wärmeleitfähigkeit, von SiGe Übergittern, genutzt. Die Beobachtung des additiven Charakters, des thermischen Widerstands, der SiGe Schichten, mit oder ohne Inselwachstum, ermöglicht die Erstellung von Strukturen mit bestimmter Wärmeleitfähigkeiten durch die Variation der Schichtdicken bis zu einer Minimaldistanz zweier Schichtübergänge von ~1.5nm. Die Ge Segregation führt zu einer Vermischung, von Si und Ge, welche eine essentielle Rolle zur diffusen Phononenstreuung spielt. Unsere Untersuchungen, von planaren Übergittern und Übergittern mit variabler Inseldichte, zeigen, dass Inseln und planare Schichten zu einer vergleichbaren Reduktion, der Wärmeleitfähigkeit, führen. Diese Beobachtung lässt sich, sowohl auf die flache Morphologie als auch die Abplattung der SiGe Inseln, aufgrund der Überwachsung mit Si, zurückführen. Die Experimente zeigen außerdem, dass sich der Barriereneffekt, der Schichtgrenzen, durch Reduktion der Schichtabstände und durch verstärkte Vermischung im Bereich der Schichtgrenzen, durch Erhitzung, eliminieren lässt. Die präsentierten Messungen sind sowohl, für die Entwicklung jener Bauteile, die eine Optimierung des thermischen Transports oder Temperaturmanagment erfordern, als auch von thermoelektrischen Matieralien und Bauteilen, basierend auf Übergittern, relevant.

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9

BELL, JOHN A. "BRILLOUIN SCATTERING FROM METAL SUPERLATTICES." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184045.

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Acoustic modes guided by thin-film metal superlattices have been investigated using Brillouin spectroscopy. Samples were grown on both single-crystal sapphire and fused silica substrates by alternately sputtering two different metals to yield a total thickness in the range 0.3 - 0.5 μm. Structural and chemical characterization of the polycrystalline films was performed using x-ray diffraction. Rutherford backscattering and optical interferometry. Thermally excited acoustic waves in the metal film create a surface ripple which weakly interacts with light incident from a single mode argon laser. A tandem Fabry-Perot consisting of two synchronized 3-pass cavities is used to measure the frequency shift of light which is inelastically scattered from acoustic waves. The contrast ratio of this interferometer exceeds 10¹⁰ and provides sufficient stray light rejection to detect the surface Rayleigh wave and as many as 13 higher order acoustic modes. The elastic stiffness constants of the anisotropic superlattices were estimated by fitting the measured acoustic mode velocities to a parameterized acoustic model. A comparison is made between these elastic constants and those predicted from the properties of the separate bulk constituents. The dependence of bilayer wavelength on the elastic properties of both Cu/Nb and Mo/Ta superlattices over the range of roughly 10 to 200 Å was determined. The unexpected softening of Cu/Nb superlattices within a range of bilayer wavelengths near 20 Å which was reported previously is qualitatively similar to the measurements reported here. It is shown that the elastic stiffness coefficient with the largest variation is c₄₄. The stiffness variations determined for the Mo/Ta samples are much smaller than for Cu/Nb. It is suggested that this is due to either structural differences (Cu/Nb is fcc-bcc and Mo/Ta is bcc-bcc) or the smaller interfacial lattice mismatch for Mo/Ta. Interfacial strain is found to be strongly correlated with the stiffness variations of the Mo/Ta samples. However, the underlying cause of these variations in stiffness remains anomalous. This dissertation also reports the first observations of Love waves and Stoneley waves by Brillouin scattering. The purely transverse Love waves guided by Cu/Nb films were detected by elasto-optic scattering from the evanescent acoustic strain in the sapphire substrate. The stiffness coefficient c₁₂ of the hexagonally symmetric metal film cannot be determined by the other guided acoustic waves which ripple the surface. Molybdenum in contact with fused silica is predicted to support a Stoneley wave which is guided by the interface. The lowest order Sezawa made guided by a molybdenum film was found to evolve to the Stoneley wave as the film becomes thicker. These measurements together with measurements of the surface Rayleigh wave show that the stiffness of the sputtered metal films is quite homogeneous and independent of film thickness.

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Boufelfel, Ahmed. "Iron-based magnetic metallic superlattices." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184340.

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For the first time we prepared and investigated the structural, magnetic, and electrical transport properties of Fe/W, Fe/Mo, and Fe/Pd metallic superlattices. We made a theoretical attempt to explain the induced increase or decrease of the magnetization at the magnetic superlattice interfaces. We used several x-ray diffraction techniques to determine the structural properties of our superlattices. Mossbauer spectroscopy and neutron scattering were used to determine the induced microscopic magnetic effects due to the superlattice structure. Brillouin scattering spectroscopy was used to determine the elastic and magnetic properties of our samples. We investigated the electrical transport properties over a wide range of temperatures of Fe/Pd and Fe/W superlattices.

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Books on the topic "Superlattices"

1

Allan, Guy, Michel Lannoo, Gérald Bastard, Michel Voos, and Nino Boccara, eds. Heterojunctions and Semiconductor Superlattices. Berlin, Heidelberg: Springer Berlin Heidelberg, 1986. http://dx.doi.org/10.1007/978-3-642-71010-0.

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Ivchenko, Eougenious L., and Grigory Pikus. Superlattices and Other Heterostructures. Berlin, Heidelberg: Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-642-97589-9.

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Ivchenko, Eougenious L., and Grigory E. Pikus. Superlattices and Other Heterostructures. Berlin, Heidelberg: Springer Berlin Heidelberg, 1997. http://dx.doi.org/10.1007/978-3-642-60650-2.

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NATO, Advanced Study Institute on Interfaces Quantum Wells and Superlattices (1987 Banff Alta ). Interfaces, quantum wells, and superlattices. New York: Plenum Press, 1988.

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Leavens, C. Richard, and Roger Taylor, eds. Interfaces, Quantum Wells, and Superlattices. Boston, MA: Springer US, 1988. http://dx.doi.org/10.1007/978-1-4613-1045-7.

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6

M, Biefeld Robert, ed. Compound semiconductor strained-layer superlattices. Brookfield VT: Trans Tech Publications, 1989.

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Roger, Taylor, ed. Interfaces, Quantum Wells, and Superlattices. Boston, MA: Springer US, 1988.

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1938-, Shinjo Teruya, and Takada Toshio 1922-, eds. Metallic superlattices: Artificially structured materials. Amsterdam: Elsevier, 1987.

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Leo, Karl. High-Field Transport in Semiconductor Superlattices. Berlin, Heidelberg: Springer Berlin Heidelberg, 2003. http://dx.doi.org/10.1007/b13579.

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T, Grahn H., ed. Semiconductor superlattices: Growth and electronic properties. Singapore: World Scientific, 1995.

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Book chapters on the topic "Superlattices"

1

Fewster, Paul F. "Superlattices." In X-Ray and Neutron Dynamical Diffraction, 289–99. Boston, MA: Springer US, 1996. http://dx.doi.org/10.1007/978-1-4615-5879-8_20.

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Hess, Karl. "Superlattices." In The Physics of Submicron Semiconductor Devices, 361–72. Boston, MA: Springer US, 1988. http://dx.doi.org/10.1007/978-1-4899-2382-0_10.

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Ploog, Klaus. "Doping Superlattices." In Molecular Beam Epitaxy and Heterostructures, 533–74. Dordrecht: Springer Netherlands, 1985. http://dx.doi.org/10.1007/978-94-009-5073-3_15.

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Esaki, Leo. "Compositional Superlattices." In The Technology and Physics of Molecular Beam Epitaxy, 143–84. Boston, MA: Springer US, 1985. http://dx.doi.org/10.1007/978-1-4899-5364-3_6.

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Döhler, Gottfried H. "Doping Superlattices." In The Technology and Physics of Molecular Beam Epitaxy, 233–74. Boston, MA: Springer US, 1985. http://dx.doi.org/10.1007/978-1-4899-5364-3_8.

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Kerkmann, D., and D. Pescia. "Metallic Superlattices." In Physics of Low-Dimensional Semiconductor Structures, 407–39. Boston, MA: Springer US, 1993. http://dx.doi.org/10.1007/978-1-4899-2415-5_11.

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Leo, Karl. "Semiconductor Superlattices." In Springer Tracts in Modern Physics, 9–26. Berlin, Heidelberg: Springer Berlin Heidelberg, 2003. http://dx.doi.org/10.1007/978-3-540-36471-9_2.

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Maan, J. C. "Doping Superlattices." In Heterojunctions and Semiconductor Superlattices, 146–51. Berlin, Heidelberg: Springer Berlin Heidelberg, 1986. http://dx.doi.org/10.1007/978-3-642-71010-0_11.

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Marzin, J. Y. "Strained Superlattices." In Heterojunctions and Semiconductor Superlattices, 161–76. Berlin, Heidelberg: Springer Berlin Heidelberg, 1986. http://dx.doi.org/10.1007/978-3-642-71010-0_13.

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Sasaki, Akio. "Disordered Superlattices." In Frontiers in Nanoscale Science of Micron/Submicron Devices, 507–18. Dordrecht: Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-009-1778-1_36.

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Conference papers on the topic "Superlattices"

1

Zavada, J. M., H. A. Jenkinson, and G. K. Hubler. "Optical index of gallium arsenide-aluminum arsenide superlattices in the near infrared." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1986. http://dx.doi.org/10.1364/oam.1986.ws2.

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The synthesis of high quality gallium arsenide–aluminum arsenide (GaAs–AlAs) superlattices has initiated a new class of optical materials with important consequences in the area of optoelectronics. For many applications it will be necessary to accurately characterize the optical properties of these materials in frequency regions of interest. In the present investigation, infrared reflectance spectroscopy is used to determine the optical indices of several GaAs–AlAs superlattice films in the near-infrared region (4000–10,000 cm−1). Each of the superlattices under study had an average aluminum mole fraction equal to 0.523. The reflectivity measurements indicate that the optical index of a particular superlattice can be higher or lower than that of the equivalent AlGaAs alloy depending on the layer periodicity of the superlattice. These results are compared with theoretical treatments of GaAs–AlAs superlattices1 and with prior experimental studies at energies above 1.2 eV.2

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Simpson, T. B., R. P. Leavitt, G. J. Simonis, J. J. Winter, J. E. Anthony, and T. R. AuCoin. "Laser-modulated transmission in GaAs doping superlattices." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1985. http://dx.doi.org/10.1364/oam.1985.fr1.

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The doping superlattice1 consists of thin alternating layers of n- and p-doped semiconducting material. The electric field induced by carrier migration leads to band bending and to an indirect band gap in real space. The energy of this indirect band gap can be tuned by creating electron–hole pairs by means of laser excitation, thus changing the transmission, reflection, and photoluminescent properties of the superlattice. GaAs doping superlattices having various layer thicknesses and dopant levels were grown by means of molecular beam epitaxy. Optical properties of the samples were measured at temperatures ~300, 80, and 5 K. Modulation of the optical properties by an exciting Ar laser was strongest at 5 K and too small to be observed at 300 K. At 5 K, under appropriate laser excitation, photoluminescent peaks were shifted toward longer wavelengths, as far as 9300 Å. Laser-modulated absorption was observed from 8250 Å, corresponding to an energy slightly less than the GaAs direct band gap, to 8900 Å. The experimental results are compared with theoretical calculations of properties of doping superlattices.

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Choquette, Kent D., and Leon Mccaughan. "Nonresonant optical nonlinearity in short-period GaAs doping superlattices." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1989. http://dx.doi.org/10.1364/oam.1989.tuy2.

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In a semiconductor doping or n-i-p-i superlattice, the periodic variation of impurities introduces a space-charge-induced superlattice potential which modifies the bulk electronic band structure and allows tailoring of the optical properties. We propose that short-period doping superlattices are suitable for the enhancement of a third- order optical susceptibility arising from electrons in nonparabolic conduction subbands. The advantages of doping superlattices are the ability to simply engineer the superlattice potential profile, thus giving control of miniband dispersion, and to provide free carriers to occupy these subbands. Room temperature electronic and nonlinear optical properties are calculated and optimized for uniformly doped and planar doped superlattice geometries. Compensated calculations are used to determine the superlattice potential profile which gives an optimally nonparabolic first conduction subband. We then self-consistently calculate the resulting optical nonlinearity for noncompensated n-type superlattices possessing this same potential shape. We show that small modulations of the superlattice potential lead to small minigaps and large subband nonparabolicities; a twentyfold improvement in the third-order optical susceptibility over bulk GaAs is predicted. Optical characterization and preliminary measurements for uniformly doped GaAs doping superlattices are discussed.

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Borca-Tasciuc, Theodorian, Jianlin Liu, Taofang Zeng, Weili Liu, David W. Song, Caroline D. Moore, Gang Chen, et al. "Temperature Dependent Thermal Conductivity of Symmetrically Strained Si/Ge Superlattices." In ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-1069.

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Abstract Experimental evidence for a significant thermal conductivity reduction has been reported in recent years for GaAs/AlAs, Si/Ge, and Bi2Te3/Sb2Te3 superlattices. Previously reported experimental studies on Si/Ge superlattices are based on samples grown by metal oxide chemical vapor deposition (MOCVD) on GaAs substrates with Ge buffers. In this work, we present experimental results on the temperature dependent thermal conductivity of symmetrically strained Si/Ge superlattices grown by molecular beam epitaxy (MBE) as a function of the superlattice period and the growth temperature. Thermal conductivity measurements are performed using a differential 3ω method. In this technique, the temperature drop across the superlattice film is experimentally determined and used to estimate the thermal conductivity of the film. Transmission electron microscopy (TEM) is employed to study the quality of the superlattice and the influence of the growth temperature on the superlattice structure. For all the superlattices studied, the measured thermal conductivity values are lower than that of the Si0.5Ge0.5 alloy. Furthermore, the measured thermal conductivity of a 40Å period Si/Ge superlattice with high dislocation density is comparable to the calculated minimum thermal conductivity of the constituent bulk materials.

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Choquette, Kent D., Leon McCaughan, J. E. Potts, D. K. Misemer, G. Haugen, and G. D. Vernstrom. "Tunable photoluminescence of uniformly doped short-period GaAs doping superlattices." In Integrated Photonics Research. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/ipr.1990.mb4.

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Doping or n-i-p-i superlattices are promising materials for tunable light sources. Long-period GaAs doping superlattices have exhibited wide tunability in the photoluminescence (PL) peak energy versus excitation intensity,1 but photopumped lasing has been observed only at high excitation, where excess carriers completely screen the superlattice space-charge potential.2 By contrast, short-period superlattices possess a smaller degree of luminescence tunability yet exhibit larger oscillator strengths because of the greater overlap between electron and hole wave functions in the n- and p-type layers, respectively. A desirable goal is to achieve lasing at carrier densities below the value that completely screens the superlattice potential, thereby permitting tunability of the radiation. We have investigated the limits of tunability in uniformly doped short-period GaAs doping superlattices and present results of low-temperature photoluminescence.

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McGill, T. C. "HgTe-CdTe superlattice infrared detectors." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1986. http://dx.doi.org/10.1364/oam.1986.tub1.

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A great deal of interest has developed in the use of superlattices as infrared materials. The infrared superlattice to be discussed is the one formed by laying down repeatedly a layer of Hg x 1Cd1- x 1 Te followed by a layer of Hg x 2Cd1- x 2 Te with x1 ≠ x2. To date, most of the research has been for the case when x1 = 1 and x2 = 0. The theoretical studies have indicated that superlattices could provide an interesting solution to a number of problems that exist with the alloy materials. For example, the band gap of the superlattice is adjusted by adjusting the thickness of the HgTe and CdTe layers, in contrast to the alloy, where the relative concentration of the Hg and Cd are used to control the gap. Particularly in the case of narrow band gap systems, this form of control seems easier to accomplish. In the superlattice, the direct relationship between the effective mass and the band gap is broken making possible the suppression of tunneling, leakage currents even in very narrow band gap materials. These superlattices have been successfully fabricated. Current research is emphasizing the near band gap properties and structural characterization of these superlattices. In this presentation, we make a critical examination of what we know about these properties and the degree to which there is agreement between theory and experiment.

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Huxtable, Scott T., Alexis R. Abramson, Arun Majumdar, Chang-Lin Tien, Chris LaBounty, Xiaofeng Fan, Gehong Zeng, John E. Bowers, Ali Shakouri, and Edward T. Croke. "Thermal Conductivity of Si/SiGe Superlattices." In ASME 2001 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/imece2001/htd-24397.

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Abstract The cross-plane and in-plane thermal conductivity of four Si/Si0.7Ge0.3 superlattice structures with periods from 45 Å to 300 Å are experimentally investigated using the 3-ω measurement technique. The experiment is conducted over a temperature range from 70 to 340 K. Results indicate that the cross-plane thermal conductivity decreases with decreasing period thickness (i.e. increasing number of interfaces per unit length). The superlattice with the shortest period exhibits a cross-plane thermal conductivity similar to that of a SiGe alloy. The in-plane thermal conductivity follows a similar decreasing trend with period thickness for the three larger period superlattices, but jumps to higher values for the shortest period superlattice. Additionally, the in-plane conductivity can be 3–4 times higher than the cross-plane value.

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Wu, Shih-Kuo, and Ya-Wen Chou. "Modeling of Heat Transfer in Nanoscale Multilayer Solid-State Structures." In ASME 2008 First International Conference on Micro/Nanoscale Heat Transfer. ASMEDC, 2008. http://dx.doi.org/10.1115/mnht2008-52224.

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Modeling of heat transfer in nanoscale multilayer solid-state structures is presented in this article to seek a potential design of thermoelectric materials. The phonon radiative heat conduction equation is used to describe the heat transport behavior in nanoscale multilayer solid-state structures and the diffuse mismatch model is utilized to simulate the interface condition between two dissimilar materials. In this paper, the thermal conductivity of thin film superlattices, nano wire superlattices and nano tube superlattices were calculated. Then, size effects on the performance of thermoelectric micro coolers were examined in detail. The results show that the effective thermal conductivity of thermoelectric materials in superlattice structures decreases as the layer thickness decreases. In addition, the thermal conductivities of nano wire and nano tube superlattices are less than that of thin film superlattices when they have the same layer thickness. It is noted that the restriction on the radial direction not only decreases the thermal conductivity in radial direction but also in axial direction. Thus, nano wire and nano tube superlattices are potential materials for high performance thermoelectric devices.

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Song, J. J., P. S. Jung, Y. S. Yoon, C. W. Tu, T. Vreeland, and S. Nieh. "Excitons in GaAs/(Al,Ga)As superlattices with coupled wells." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1988. http://dx.doi.org/10.1364/oam.1988.fr4.

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Various new electrooptic device concepts have recently been proposed which utilize the electronic energy band structures in semiconductor superlattices. The energy bands and excitons in superlattices have not received as much attention as those in quantum wells. A series of high-quality GaAs/(Al, Ga)As superlattice samples have been fabricated to have varying barrier widths using MBE. These samples have been analyzed by transmission electron microscopy to determine the layer thicknesses. Excitation spectroscopy at 5 K was employed to study the energy subband and exciton structures in superlattices. In thin barrier superlattices, well-to-well coupling significantly affects the miniband structures and excitonic states. We report here our observations of the spectral changes associated with coupling of the wells in superlattices. Minor peaks and bumps appeared in addition to the major heavy-hole and light-hole exciton peaks. Striking changes in these exciton spectra were detected with a small change (20 Å) in the barrier widths. From these structures, exciton binding energies in superlattices were derived and found to depend on the barrier layer width. Some of the minor peaks are attributed to the excitons formed at the Brillouin zone edge.

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da Silva, Carlos, Fernan Saiz, David A. Romero, and Cristina H. Amon. "Predicting Phonon Thermal Transport in Two-Dimensional Graphene-Boron Nitride Superlattices at the Short-Period Limit." In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-50675.

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Two-dimensional superlattices are promising alternatives to traditional semiconductors for manufacturing power-dissipating devices with enhanced thermal and electronic properties. The goal of this work is to investigate the influence of the superlattice secondary periodicity and atomic interface orientation on the phonon properties and thermal conductivity of two-dimensional superlattices of graphene and boron nitride. We have employed harmonic lattice dynamics to predict the phonon group velocities and specific heats, and molecular dynamics to extract the relaxation times from normal mode analysis in the frequency domain. Density functional perturbation theory is applied to validate the phonon dispersion curves. The Boltzmann transport equation under single relaxation time approximation is then used to predict the thermal conductivities of the superlattices in the zigzag and armchair orientations with periodicities between one and five. Our results showed that the thermal conductivities increased by 15.68% when reducing the superlattice period from two to one. In addition, thermal conductivities parallel to the interface increase by 20.15% when switching the orientation from armchair to zigzag.

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Reports on the topic "Superlattices"

1

Camley, R. E. Magnetic Superlattices. Fort Belvoir, VA: Defense Technical Information Center, January 1988. http://dx.doi.org/10.21236/ada191450.

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Tsui, D. C. Electron Transport in Heterojunction Superlattices. Fort Belvoir, VA: Defense Technical Information Center, August 1989. http://dx.doi.org/10.21236/ada212366.

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Thomas, John E. Fermi Gases in Bichromatic Superlattices. Office of Scientific and Technical Information (OSTI), November 2019. http://dx.doi.org/10.2172/1573239.

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Li, S., J. A. Eastman, J. Vetrone, R. E. Newnham, and L. E. Cross. Coherent coupling in ferroelectric superlattices. Office of Scientific and Technical Information (OSTI), July 1996. http://dx.doi.org/10.2172/286271.

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Schuller, I. K. Preparation and characterization of superlattices. Office of Scientific and Technical Information (OSTI), January 1992. http://dx.doi.org/10.2172/5430644.

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Rochansky, A. Highly-Polarized Electron Emission from Strain-Compensated Superlattices and Superlattices with High-Valence-Band Splitting. Office of Scientific and Technical Information (OSTI), March 2004. http://dx.doi.org/10.2172/826800.

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te Velthuis, S. G. E., A. Hoffmann, and J. Santamaria. Magnetic profiles in ferromagnetic/superconducting superlattices. Office of Scientific and Technical Information (OSTI), February 2007. http://dx.doi.org/10.2172/947081.

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Razeghi, Manijeh. GaAs-GaInP Superlattices for Intersubband Photodetection. Fort Belvoir, VA: Defense Technical Information Center, September 1998. http://dx.doi.org/10.21236/ada353981.

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Fullerton, E. E., J. E. Matson, C. H. Sowers, and S. D. Bader. Antiferromagnetic interlayer coupling of Ni/Mo superlattices. Office of Scientific and Technical Information (OSTI), June 1993. http://dx.doi.org/10.2172/10194947.

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CA Wand, CJ Vineis, and DR Calawa. Self-Organized Vertical Superlattices in Epitaxial GaInAsSb. Office of Scientific and Technical Information (OSTI), February 2004. http://dx.doi.org/10.2172/824866.

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