Scholarly Work - Physics
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Item Anisotropic 2D excitons unveiled in organic–inorganic quantum wells(Royal Society of Chemistry, 2020-11) Maserati, Lorenzo; Refaely-Abramson, Sivan; Kastl, Christoph; Chen, Christopher T.; Borys, Nicholas J.; Eisler, Carissa N.; Collins, Mary S.; Smidt, Tess E.; Barnard, Edward S.; Strasbourg, Matthew; Schriber, Elyse A.; Shevitski, Brian; Yao, Kaiyuan; Hohman, J. Nathan; Schuck, P. James; Aloni, Shaul; Neaton, Jeffrey B.; Schwartzberg, Adam M.Hybrid layered metal chalcogenide crystalline polymer hosts strongly anisotropic two-dimensional excitons with large binding energies.Item Electrically driven photon emission from individual atomic defects in monolayer WS2(2020-09) Schuler, Bruno; Cochrane, Katherine A.; Kastl, Christoph; Barnard, Edward S.; Wong, Edward; Borys, Nicholas J.; Schwartzberg, Adam M.; Ogletree, D. Frank; Garcia de Abajo, F. Javier; Weber-Bargioni, AlexanderQuantum dot–like single-photon sources in transition metal dichalcogenides (TMDs) exhibit appealing quantum optical properties but lack a well-defined atomic structure and are subject to large spectral variability. Here, we demonstrate electrically stimulated photon emission from individual atomic defects in monolayer WS2 and directly correlate the emission with the local atomic and electronic structure. Radiative transitions are locally excited by sequential inelastic electron tunneling from a metallic tip into selected discrete defect states in the WS2 bandgap. Coupling to the optical far field is mediated by tip plasmons, which transduce the excess energy into a single photon. The applied tip-sample voltage determines the transition energy. Atomically resolved emission maps of individual point defects closely resemble electronic defect orbitals, the final states of the optical transitions. Inelastic charge carrier injection into localized defect states of two-dimensional materials provides a powerful platform for electrically driven, broadly tunable, atomic-scale single-photon sources.Item Light-Driven Permanent Charge Separation across a Hybrid Zero-Dimensional/Two-Dimensional Interface(2020-04) Kriegel, Ilka; Ghini, Michele; Bellani, Sepastiano; Zhang, Kehao; Jansons, Adam W.; Crockett, Brandon M.; Koskela, Kristopher M.; Barnard, Edward S.; Penzo, Erika; Hutchison, James E.; Robinson, Joshua A.; Manna, Liberato; Borys, Nicholas J.; Schuck, P. JamesWe report the first demonstration of light-driven permanent charge separation across an ultrathin solid-state zero-dimensional (0D)/2D hybrid interface by coupling photoactive Sn-doped In2O3 nanocrystals with monolayer MoS2, the latter serving as a hole collector. We demonstrate that the nanocrystals in this device-ready architecture act as local light-controlled charge sources by quasi-permanently donating ∼5 holes per nanocrystal to the monolayer MoS2. The amount of photoinduced contactless charge transfer to the monolayer MoS2 competes with what is reached in electrostatically gated devices. Thus, we have constructed a hybrid bilayer structure in which the electrons and holes are separated into two different solid-state materials. The temporal evolution of the local doping levels of the monolayer MoS2 follows a capacitive charging model with effective total capacitances in the femtofarad regime and areal capacitances in the μF cm–2 range. This analysis indicates that the 0D/2D hybrid system may be able to store light energy at densities of at least μJ cm–2, presenting new potential foundational building blocks for next-generation nanodevices that can remotely control local charge density, power miniaturized circuitry, and harvest and store optical energy.Item Long-Range Exciton Diffusion in Two-Dimensional Assemblies of Cesium Lead Bromide Perovskite Nanocrystals(2020-05) Penzo, Erika; Loiudice, Anna; Barnard, Edward S.; Borys, Nicholas J.; Jurow, Matthew J.; Lorenzon, Monica; Rajzbaum, Igor; Wong, Edward K.; Liu, Yi; Schwartzberg, Adam M.; Cabrini, Stefano; Whitelam, Stephen; Buonsanti, Raffaella; Weber-Bargioni, AlexanderFörster resonant energy transfer (FRET)-mediated exciton diffusion through artificial nanoscale building block assemblies could be used as an optoelectronic design element to transport energy. However, so far, nanocrystal (NC) systems supported only diffusion lengths of 30 nm, which are too small to be useful in devices. Here, we demonstrate a FRET-mediated exciton diffusion length of 200 nm with 0.5 cm2/s diffusivity through an ordered, two-dimensional assembly of cesium lead bromide perovskite nanocrystals (CsPbBr3 PNCs). Exciton diffusion was directly measured via steady-state and time-resolved photoluminescence (PL) microscopy, with physical modeling providing deeper insight into the transport process. This exceptionally efficient exciton transport is facilitated by PNCs’ high PL quantum yield, large absorption cross section, and high polarizability, together with minimal energetic and geometric disorder of the assembly. This FRET-mediated exciton diffusion length matches perovskites’ optical absorption depth, thus enabling the design of device architectures with improved performances and providing insight into the high conversion efficiencies of PNC-based optoelectronic devices.Item Light-Driven Permanent Charge Separation across a Hybrid Zero-Dimensional/Two-Dimensional Interface(2020-03) Kriegel, Ilka; Ghini, Michele; Bellani, Sebastiano; Zhang, Kehao; Jansons, Adam W.; Crockett, Brandon M.; Koskela, Kristopher M.; Barnard, Edward S.; Penzo, Erika; Hutchison, James E.; Robinson, Joshua A.; Manna, Liberato; Borys, Nicholas J.; Schuck, P. JamesWe report the first demonstration of light-driven permanent charge separation across an ultrathin solid-state zero-dimensional (0D)/2D hybrid interface by coupling photoactive Sn-doped In2O3 nanocrystals with monolayer MoS2, the latter serving as a hole collector. We demonstrate that the nanocrystals in this device-ready architecture act as local light-controlled charge sources by quasi-permanently donating ∼5 holes per nanocrystal to the monolayer MoS2. The amount of photoinduced contactless charge transfer to the monolayer MoS2 competes with what is reached in electrostatically gated devices. Thus, we have constructed a hybrid bilayer structure in which the electrons and holes are separated into two different solid-state materials. The temporal evolution of the local doping levels of the monolayer MoS2 follows a capacitive charging model with effective total capacitances in the femtofarad regime and areal capacitances in the μF cm–2 range. This analysis indicates that the 0D/2D hybrid system may be able to store light energy at densities of at least μJ cm–2, presenting new potential foundational building blocks for next-generation nanodevices that can remotely control local charge density, power miniaturized circuitry, and harvest and store optical energy.