Structural characterization is essential for the understanding of the magnetic properties of thin films and multilayers. In this thesis, both crystalline and amorphous thin films and multilayers were analyzed utilizing transmission electron microscopy (TEM). High resolution TEM and electron diffraction studies emphasize on the growth of amorphous Fe91Zr9 and Co68Fe24Zr8 on both Al2O3 and Al70Zr30 in multilayer structures by magnetron sputtering. The properties of the growth surfaces were found to strongly influence the formation of nano-crystallites of the magnetic material at interfaces. Field induced uniaxial magnetic anisotropy was found to be possible to imprint into both fully amorphous and partially crystallized Co68Fe24Zr8 layers, yielding similar magnetic characteristics regardless of the structure. These findings are important for the understanding of both growth and magnetic properties of these amorphous thin films. As magnetic systems become smaller, new analysis techniques need to be developed. One such important step was the realization of electron energy-loss magnetic circular dichroism (EMCD) in the TEM, where information about the ratio of the orbital to spin magnetic moment (mL/mS) of a sample can be obtained. EMCD makes use of angular dependent inelastic scattering, which is characterized using electron energy-loss spectroscopy. The work of this thesis contributes to the development of EMCD by performing quantitative measurements of the mL/mS ratio. Especially, methods for obtaining energy filtered diffraction patterns in the TEM together with analysis tools of the data were developed. It was found that plural inelastic scattering events modify the determination of the mL/mS ratio, wherefore a procedure to compensate for it was derived. Additionally, utilizing special settings of the electron gun it was shown that EMCD measurements becomes feasible on the nanometer level through real space maps of the EMCD signal.

This thesis examines second-order optical nonlinear wave mixing processes in domain-disordered quasi-phase matching waveguides and evaluates their potential use in compact, monolithically integrated wavelength conversion devices. The devices are based on a GaAs/AlGaAs superlattice-core waveguide structure with an improved design over previous generations. Quantum-well intermixing by ion-implantation is used to create the quasi-phase matching gratings in which the nonlinear susceptibility is periodically suppressed. Photoluminescence experiments showed a large band gap energy blue shift around 70 nm after intermixing. Measured two-photon absorption coefficients showed a significant polarization dependence and suppression of up to 80% after intermixing. Similar polarization dependencies and suppression were observed in three-photon absorption and nonlinear refraction. Advanced modeling of second-harmonic generation showed reductions of over 50% in efficiency due to linear losses alone. Self-phase modulation was found to be the dominant parasitic nonlinear effect on the conversion efficiency, with reductions of over 60%. Simulations of group velocity mismatch showed modest reductions in efficiency of less than 10%. Experiments on second-harmonic generation showed improvements in efficiency over previous generations due to low linear loss and improved intermixing. The improvements permitted demonstration of continuous wave second-harmonic generation for the first time in such structures with output power exceeding 1 µW. Also, Type-II phase matching was demonstrated for the first time. Saturation was observed as the power was increased, which, as predicted, was the result of self-phase modulation when using 2 ps pulses. By using 20 ps pulses instead, saturation effects were avoided. Thermo-optically induced bistability was observed in continuous wave experiments. Difference frequency generation was demonstrated with wavelengths from the optical C-band being converted to the L- and U-bands with continuous waves. Conversion for Type-I phase matching was demonstrated over 20 nm with signal and idler wavelengths being separated by over 100 nm. Type-II phase matched conversion was also observed. Using the experimental data for analysis, self-pumped conversion devices were found to require external amplification to reach practical output powers. Threshold pump powers for optical parametric oscillators were calculated to be impractically large. Proposed improvements to the device design are predicted to allow more practical operation of integrated conversion devices based on quasi-phase matching superlattice waveguides.

In the first part of this work, the influence of hydrogen on the structural and magnetic properties of Fe/V(001) superlattices was studied. The local structure of the vanadium-hydride layers was determined by extended x-ray absorption fine structure (EXAFS) measurements. The magnetic ordering in a weakly coupled Fe/V(001) superlattice was investigated using the magneto-optical Kerr effect (MOKE). The interlayer exchange coupling is weakened upon alloying with hydrogen and a phase with short-range magnetic order was observed. The second part is concerned with first-principles calculations of magnetic materials, with a focus on magnetic recording applications. The uniaxial magnetic anisotropy energy (MAE) of Fe, Co, and Ni was calculated for tetragonal and trigonal structures. Based on an analysis of the electronic states of tetragonal Fe and Co at the center of the Brillouin zone, tetragonal Fe-Co alloys were proposed as a material that combines a large uniaxial MAE with a large saturation magnetization. This was confirmed by experimental studies on (Fe,Co)/Pt superlattices. The large uniaxial MAE of L10 FePt is caused by the large spin-orbit interaction on the Pt sites in connection with a strong hybridization between Fe and Pt. Furthermore, it was shown that the uniaxial MAE can be increased by alloying the Fe sublattice with Mn. The combination of the high-moment rare-earth (RE) metals with the high-TC 3d transition metals in RE/Cr/Fe multilayers (RE = Gd, Tb, Dy) gives rise to a strong ferromagnetic effective exchange interaction between the Fe layers and the RE layer. The MAE of hcp Gd was found to have two principal contributions, namely the dipole interaction of the large localized 4f spins and the band electron magnetic anisotropy due to the spin-orbit interaction. The peculiar temperature dependence of the easy axis of magnetization was reproduced on a qualitative level.

In order to understand the properties of thin film devices, knowledge of the material's structure is essential. The work presented here combines magnetic and structural characterization of the systems studied to gain a deeper physical understanding. The magnetic properties have been studied with a combination of x-ray magnetic circular dichroism, SQUID magnetometry and magneto-optical Kerr effect. For the structural characterization, x-ray reflectivity and diffraction have been used, complemented by neutron diffraction and transmission electron microscopy. One structural property that affects the magnetic moment in metal-on-metal superlattices is interdiffusion between the layers. This is discussed for bcc Fe/Co(001) and bcc Fe81Ni19/Co(001) superlattices. The effect of interdiffusion was seen as a large region of enhanced magnetic moments as compared to theoretical calculations, which assume perfectly sharp interfaces. For the Fe81Ni19/Co(001) superlattices the chemical interface region, as revealed by neutron diffraction, was in good agreement with the region of magnetic enhancement. Another structural property that has been investigated is the strain in the magnetic layers. This does not affect the spin magnetic moment to a large extent. However the magnetocrystalline anisotropy and the orbital moment are affected by the presence of strain. The effects on the orbital moment from strain and interfaces for Fe in Fe/V superlattices was studied, and it was found that the two contributions were separable. In this context the effect of strain on the out-of-plane magnetocrystalline anisotropy in FeCo/Pt has also been studied. The latter system is interesting from a technological perspective since tetragonally distorted FeCo alloys have the potential to be suitable new materials in computer hard drives. Finally, a computer program, based on the Differential Evolution algorithm, to refine primarily x-ray reflectivity data, is presented.

Transition metal carbides have great industrial importance with a wide area of applications. Unlike many ceramic materials which can be produced from raw materials found in nature, the refractory carbides generally do not exist in the natural state. Synthesis of these carbides is costly and exacting. Sputtered coatings of the refractory metal carbides are of great interest for applications where hard wear-resistant materials are desired. Understanding how the experimental conditions affect the microstructure and properties in reactive sputtering deposition process is still an area of intense research activity. Reactively sputtered zirconium carbide thin films were grown on (100) silicon substrate and the influence of substrate temperature on the properties of the films were investigated. The substrate temperature was varied from ambient to 500°C and partial pressures of the sputter gas and reactive gas (argon and methane) were optimised to obtain crystalline films. Structural characteristics showed that the films exhibit nanocomposite structure consisting of ZrC nanocrystallites embedded in amorphous carbon typically at lower growth temperature (TS < 300°C), and at higher growth temperatures film were highly textured. In addition, Films deposited at 325 °C showed a distinct increase in FWHM which had considerable effect on the mechanical properties of the film. Maximum hardness of 24.8 GPa was seen at 325ºC. The changes in atomic bonding structures, their relative fractions with respect to substrate temperature were discussed. We also report superhard nanocrystalline nanocomposite NbC thin film deposited on Si (100) under 500˚C growth temperature via reactive magnetron sputtering. The pronounced nano hardness and modulus value of 42 GPa and 267 GPa at 40/60 C/Nb ratio were found to be strongly dependent on the grain size and higher percentage of carbide content. HRTEM studies further confirm the formation of nanocomposite structure with nanocrystalline grains embedded in amorphous matrix. The influence of vapour incidence angle (α= 0˚ to 75˚) on optimized ZrC and NbC thin films were investigated by depositing films in Oblique angle deposition geometry (OAD). The anisotropic growth rate of crystallographic planes and the mechanism of development of micro structural features in OAD of carbide films have been investigated. XRD and pole figure measurements indicated that the films grown at higher growth temperatures (800°C) exhibited higher degree of preferred orientation coupled with larger crystallite size whereas the films deposited at room temperature displayed random polycrystalline nature. The strong increase in porosity with increase in deposition angle with distinctly separated nanometer sized columns resulted in lowering of hardness and reduced modulus value. The film with zero incidence angle exhibited a maximum hardness and reduced modulus of 28 GPa and 223 GPa respectively. On the other hand, NbC films deposited with OAD, remained to be polycrystalline in nature with less intense peaks and also exhibited loss of preferential orientation indicating lower crystal quality with increase in vapor deposition angle. It is apparent that variation in crystallographic texture coupled with sculptured nanostructures are solely material dependent properties. Nano metric modulated ZrC/NbC superlattice multilayer structure performance has been evaluated for structural stability and hardness enhancement. Multilayers present superlattice effect in XRD patterns, which are attributed to the precise periodical stacking of crystalline monolayers also confirmed by cross section FESEM. X-ray photoelectron spectroscopy depth profile analysis was performed to get information on chemical composition of modulated layers and also to get an insight on the interface region. Hardness and modulus value of 43.2 GPa and 272 GPa was observed which is higher than individual monolayers response to mechanical loading. The enhanced hardness is possibly due to the inhibition of dislocation motion along the interface and also due to strain effects at the interface.

La thèse est axée sur l'examen de l'effet de la contrainte sur la conductivité thermique des matériaux piézoélectriques. Les matériaux piézoélectriques sont des cristaux qui présentent une déformation mécanique lors de l'application d'un champ électrique. Des exemples de tels systèmes sont ZnO, AlN, et SiO2. En utilisant des simulations de dynamique moléculaire, nous avons calculé la conductivité thermique de cristaux de ZnO et AlN sous contrainte. Nous avons aussi calculé la résistance thermique des interfaces SiO/C et ZnO/C soumis à un champ électrique.Nous commençons par le calcul des propriétés piézoélectriques et élastiques de ZnO. Celles-ci serviront à valider les potentiels interatomiques utilisés, et à montrer l'ampleur de la contrainte qu’il est possible d'appliquer. En utilisant la dynamique moléculaire d'équilibre, nous avons estimé le coefficient élastique c33 de ZnO, qui se trouve être en accord avec les valeurs expérimentales. Il a aussi été déterminé que la limite élastique d'un cristal de ZnO est de 6 GPa, ce qui correspond à une déformation de 6%. Nous avons ensuite établi les coefficients piézoélectriques de ZnO en utilisant la dynamique moléculaire de non-équilibre, et il a été constaté que les coefficients piézoélectriques dij sont en accord avec les valeurs de la littérature.Deuxièmement, nous avons examiné l'effet de la pression sur la conductivité thermique intrinsèque de ZnO et d’AlN. La dynamique moléculaire de non-équilibre inverse a été mise en œuvre pour calculer la conductivité parce que les coûts de calcul sont nettement inférieurs à ceux de la méthode d'équilibre, d’autant plus pour ZnO dont le potentiel inter-atomique contient les interactions Coulombiennes. L'effet de taille sur la conductivité thermique de ZnO et AlN a ensuite été étudié. Nous avons montré que la formule de Schelling peut en effet être mise en œuvre pour les deux cristaux pour différentes valeurs de la contrainte. La conductivité thermique pour un cristal de ZnO de taille infinie est extraite de la formule de Schelling, et elle se révèle être de 410 W/mK. La conductivité thermique de cristaux de ZnO sous contrainte a ensuite été analysée. Nous avons montré que, après correction de l'effet de taille, la conductivité thermique suit une dépendance en loi de puissance à la contrainte uniaxiale. De plus, la conductivité thermique de ZnO est affectée par un champ statique externe en raison de la contrainte induite. La conductivité thermique d'AlN est estimée à 3000 W/mK, l'effet de la contrainte ne modifie pas cette valeur du fait du potentiel inter-atomique utlisé. Par conséquent, AlN n’est pas un matériau pertinent pour faire office de switch thermique.Troisièmement, nous avons exploré l'effet d’un déplacement piézoélectrique sur la conductance thermique d’interface de Si2O/graphène et ZnO/graphène. Utilisant la dynamique moléculaire d’équilibre, la conductivité thermique d'un super-réseau dont la période est composée de silice et de graphène polyfeuillet. Le super-réseau a été évalué pour différentes valeurs du champ électrique externe. Nous avons constaté que l'application d'un champ électrique de 20 MV/m positif parallèle à la direction hors-plan du super-réseau conduit à la réduction de la conductivité thermique d'un facteur deux. D'autre part, aucun changement dans la conductance thermique n’est noté pour le super-réseau ZnO/graphène. Cette différence est due aux différences de déformations induites au niveau des interfaces dans le super-réseau. L'effet est recréé dans un super-réseau Si/Ge en appliquant une déformation pour former les interfaces. Cette approche crée une déformation non uniforme qui est susceptible de diffuser les phonons. / The thesis is focused on investigating the effect of strain on the thermal conductivity of piezoelectric materials. Piezoelectric materials are crystals which display a mechanical deformation upon application of an electric field. Examples of such material are ZnO, AlN, and SiO2. Using Molecular Dynamics simulations, we calculate the thermal conductivity of unstrained and strained ZnO and AlN crystals. We also calculate the thermal resistance of SiO/graphene interfaces under strain.We calculate the piezoelectric and elastic properties of ZnO. These will serve as confirmation of the correctness of the inter-atomic potential used, and will serve to show the magnitude of strain that is possible to apply. Using non-equilibrium molecular dynamics, we determine the elastic coefficient of ZnO c33, and we see that it agrees with experimental values. We also determine that the elastic limit of a perfect ZnO crystal is 6 GPa which corresponds to a 6% strain. We also determine the piezoelectric coefficient of ZnO using NEMD, and we find that the piezoelectric coefficient d33 also agrees with literature values.Second, we look at the effect of strain on the intrinsic thermal conductivity of ZnO and AlN. We use reverse non-equilibrium molecular dynamics to calculate the conductivity because the computational costs are significantly lower than those for the equilibrium method; especially for ZnO whose inter-atomic potential contains Coulomb interaction. We also study the size-effect on the thermal conductivity of ZnO and AlN. We show that the Schelling formula can indeed be implemented to both crystals for different values of strain. The infinite length thermal conductivity for ZnO is extracted from the formula, and it is found to be 410 W/mK. We then calculate the thermal conductivity of strained ZnO crystals. We show that after correcting for the size effect the thermal conductivity follows power-law dependence to uniaxial strain. Also, we demonstrate that the thermal conductivity of ZnO can be affected by a static external field due to the induced strain. The infinite length thermal conductivity of AlN is found to be 3000 W/mK. We show that for the case of AlN the effect of strain does not affect the thermal conductivity due to the different inter-atomic bonding. Hence, AlN might not be a useful material for piezothermal application.Third, we explore the effect of piezoelectric strain on the thermal conductance of SiO2/graphene and ZnO/graphene superlattices. Using EMD we calculate the thermal conductivity of a superlattice composed of silica and graphene monolayers. The thermal conductance of the superlattice was evaluated under different values of external electric field. We find that applying a positive electric field parallel to the Z-direction leads to reduction of the thermal conductance by a factor of 2 for an electric field of 20 MV/m. On the other hand, no change in the thermal conductance is noted for ZnO/graphene superlattice. The effect is due to the non-uniform strain induced at the superlattice junctions. The effect is recreated in Si/Ge superlattice by mechanically applying a non-uniform strain at the interface. This approach might be responsible for the scattering of phonons.

In dieser Arbeit wurden die komplexen Mechanismen für den Einbau von Mg und In in (Ga,In)N/GaN(0001)-Heterostrukturen, die mittels PA-MBE hergestellt wurden, mit morphologischen, optischen und elektrischen Charakterisierungsmethoden untersucht. Darüber hinaus wurde die Verwendung von (Ga,In)N/GaN SPSLs als HIL oder als aktiver Bereich in herkömmlichen LED-Strukturen untersucht. In-situ-Messungen zeigten, dass die Desorption von In in Gegenwart von N und Mg auf der GaN(0001)-Oberfläche zunimmt. Ferner wurden Mg-dotierte (Ga,In)N/GaN-SLs mittels PAMBE gezüchtet und mittels QMS, XRD und SIMS charakterisiert. Die (Ga,In)N/GaN-SLs zeigten eine bessere Oberflächenmorphologie als die (Ga,In)N-Schichten, die homogen mit Mg dotiert wurden. Jedoch wurde eine deutliche Abnahme des In-Gehalts in der (Ga,In)N ML festgestellt, wenn Mg gleichzeitig mit In zugeführt wurde. Gleichzeitig nahm die Mg-Konzentration in Gegenwart von In zu, was möglicherweise auf eine Wirkung als oberflächenaktive Substanz zurückzuführen ist. Für das SL, bei dem nur die (Ga,In)N-QWs mit Mg dotiert waren, wurde vom Messergebnis von SIMS eine maximale Mg-Konzentration von 2,6 × 1022 cm-3 für eine 1 ML dicke (Ga,In)N:Mg-Schicht deduziert. Zusätzlich haben andere Experimente ähnliche Ergebnisse aufgezeigt. Thermoleistung-Studien zeigten, dass das Delta-dotierte SL und die SL-Strukturen mit Mg-Dotierung in 20% der QB p-leitfähig sind. Zusätzlich wurde ein Gleichrichterverhalten der (Ga,In)N/GaN SL-Strukturen mit einem Idealitätsfaktor von weniger als 10 für die QW-dotierten SLs demonstriert. Ausgehend von der elektrischen Charakterisierung wurden drei verschiedene LED-Strukturen, die auf den vielver-sprechendsten Mg-dotierten (Ga,In)N SL-Strukturen (Delta-dotiertes SL und 20% QB-dotiertes SL) basierten, hergestellt und charakterisiert. / In this thesis, the complex mechanisms for the incorporation of Mg and In in (Ga,In)N/GaN(0001) heterostructures prepared by PA-MBE were investigated by morphological, optical, and electrical characterization methods. Furthermore, the implementation of (Ga,In)N/GaN SPSLs as a HIL or as the active region in conventional LED structures have been studied. In-situ measurements demonstrate that the desorption of In increases in the presence of both, N and Mg on the GaN(0001) surface. Further, (Ga,In)N/GaN SLs with Mg-doping grown by PAMBE and their characterization was carried out by QMS, XRD, and SIMS. A better surface morphology was obtained for the (Ga,In)N/GaN SLs in comparison to a (Ga,In)N layer homogeneously doped with Mg. Although, a notable decrease of the In content in the (Ga,In)N ML was revealed when Mg was supplied simultaneously to In. At the same time, the Mg concentration increased in the presence of In, which can possibly be attributed to a surfactant effect. For the SL that had only its (Ga,In)N QWs doped with Mg, a maximum Mg concentration of 2.6 × 1022 cm 3 for a 1 ML thick (Ga,In)N:Mg layer was deduced from SIMS measurements. Additionally, similar results have achieved later by another set of experiments. Thermopower studies revealed the p-type conductivity of the delta doped SL and of the SL structures with 20% of the QB doped by Mg. Additionally, a rectifying behavior with an ideality factor lower than 10 was demonstrated for the (Ga,In)N/GaN SL structures with QW fully doped. Based on the electrical characterization, three different LED structures were fabricated based on the most promising Mg-doped (Ga,In)N SL structures (delta doped SL, and 20% QB doped SL) and characterized.

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.

<p>   </p> <p>Colloidal cesium lead bromide (CsPbBr₃) quantum dots (QDs) have emerged as an exciting class of quantum emitters due to their near-unity quantum yields, large oscillator strengths, and long coherence time. Ordered superlattices (SLs) grown from these QDs exhibit emergent properties resulting from their assembly. In this work, we explore the self-assembly, disorder, and superradiant properties of 3D superlattices of CsPbBr₃ to understand how structural heterogeneity influences optical properties.</p> <p>A thorough understanding of the competition between coherence and dephasing from phonon scattering and energetic disorder is currently lacking in the literature. Here, we present an investigation of exciton coherence in perovskite QD solids using temperature-dependent photoluminescence linewidth and lifetime measurements. The properties of perovskite QDS described above should also enable them to overcome hurdles experienced by other materials that limit solid-state superradiance, such as fast dephasing processes from inherent disorder and thermal fluctuations. Our results demonstrate that excitons can coherently delocalize in highly ordered CsPbBr₃ superlattices leading to superradiant emission. We observe loss of coherence and exciton localization to a single QD at higher temperatures, resulting from scattering by optical phonons. At low temperatures, static disorder and defects limit exciton coherence, and a wide range of coherence numbers are observed across a self-assembled sample of SLs. These results highlight the promise and challenge in achieving long-range coherence in perovskite QD solids.</p> <p>A thorough understanding of structural heterogeneity in CsPbBr₃ quantum dot superlattices is necessary for the realization of robust exciton coherence in these systems. 3D SLs self-assemble from a colloidal solution of cubic QDs as the solvent evaporates, leading to SLs ranging widely in macroscopic size, shape, and aspect ratio. Scanning transmission electron microscopy (STEM) coupled to fast-Fourier transform (FFT) analysis is utilized to characterize the structural properties of individual SLs, such as the average constituent quantum dot size, size dispersity, and number of crystalline domains. Analysis reveals that SLs are structurally heterogeneous but tend to have a narrower size distribution than the precursor solution due to size selection that occurs during evaporative self-assembly. We directly correlate STEM-FFT structural properties to low-temperature photoluminescence spectra for individual SLs, demonstrating that substructure in the photoluminescence peak arises from multiple, locally-ordered domains within the SL. In addition, we show that long-range structural disorder in a SL does not necessarily impact short-range phenomena such as exciton delocalization.</p> <p>  </p>

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