The variegated family of two-dimensional (2D) crystals has developed rapidly since the isolation its forerunner: Graphene. Their plane-confined nature is typically associated with exceptional and peculiar electronic, optical, magnetic, mechanical properties, heightening interest fundamental science showing promise for applications. Methods tuning their properties on demand have been pursued, among which application stresses, allowed by incredible robustness flexibility these atomically thin...

The photoluminescence properties of ${\mathrm{I}\mathrm{n}\mathrm{A}\mathrm{s}/\mathrm{A}\mathrm{l}}_{y}{\mathrm{Ga}}_{1\ensuremath{-}y}\mathrm{As}$ self-assembled quantum dots are studied as a function temperature from 10 to 290 K. By varying the Al content dot luminescence can be tuned over wavelength range 0.8 1.1 \ensuremath{\mu}m, and made thermally stable up room temperature. dependence carrier hopping between is discussed in terms depth confinement potential dispersion size composition.

This paper reports the effects of high strains on optoelectronic properties 2D crystals. By realizing micro- and nano-domes made single layer transition-metal dichalcogenides, authors demonstrate possibility to induce a clear-cut crossover from direct indirect bandgap in strained monolayers. The excitons can be harvested potentially stored for long times, which is relevant flexible photovoltaics devices inducing bosonic condensation.

Abstract At the few‐atom‐thick limit, transition‐metal dichalcogenides (TMDs) exhibit strongly interconnected structural and optoelectronic properties. The possibility to tailor latter by controlling former is expected have a great impact on applied fundamental research. As shown here, proton irradiation deeply affects surface morphology of bulk TMD crystals. Protons penetrate top layer, resulting in production progressive accumulation molecular hydrogen first interlayer region. This leads...

The formation of gas-filled bubbles on the surface van der Waals crystals provides an ideal platform whereby interplay elastic parameters and interlayer forces can be suitably investigated. Here, we combine experimental numerical efforts to study morphology at equilibrium highlight unexpected behaviors that contrast with common assumptions. We exploit such observations develop accurate analytical model describe shape strain it measure adhesion energy between a variety crystals, showing...

Abstract 2D materials, such as graphene, hexagonal boron nitride (hBN), and transition‐metal dichalcogenides (TMDs), are intrinsically flexible, can withstand very large strains (>10% lattice deformations), their optoelectronic properties display a clear distinctive response to an applied stress. As such, they uniquely positioned both for the investigation of effects mechanical deformations on solid‐state systems exploitation these in innovative devices. For example, materials be easily...

Hexagonal boron nitride (hBN) is widely used as a protective layer for few-atom-thick crystals and heterostructures (HSs), it hosts quantum emitters working up to room temperature. In both instances, strain expected play an important role, either unavoidable presence in the HS fabrication or tool tune emitter electronic properties. Addressing role of exploiting its tuning potentiality require development efficient methods control reliable tools quantify it. Here we present technique based on...

The band-anticrossing (BAC) model has been widely applied to analyse the electronic structure of dilute nitride III-V-N alloys such as GaNxAs1−x. BAC describes strong band gap bowing observed at low N composition in GaNxAs1−x terms an interaction between GaAs host matrix conduction edge and a higher lying localized resonant states. In practice, replacing As by introduces range N-related defect levels, associated with isolated atoms, N–N pairs larger clusters atoms. We show that effect levels...

Abstract The realization of ordered strain fields in 2D crystals is an intriguing perspective many respects, including the instauration novel transport regimes and enhanced device performances. However, current straining techniques hardly allow to reach strains higher than ≈3% most cases there no control over distribution. In this work, a method demonstrated subject micrometric regions atomically thin molybdenum disulfide (MoS 2 ) giant with desired ordering. Selective hydrogen‐irradiation...

Abstract Monolayers (MLs) of transition‐metal dichalcogenides host efficient single‐photon emitters (SPEs) usually associated to the presence nanoscale mechanical deformations or strain. Large‐scale spatial control strain would enhance scalability such SPEs and allow for their incorporation into photonic structures. Here, formation regular arrays strained hydrogen‐filled one‐layer‐thick micro‐domes obtained by H‐ion irradiation lithography‐based approaches is reported. Typically, H 2...

In x Ga 1−x As 1−y N y / GaAs single quantum wells emitting at room temperature in the wavelength range λ=(1.3–1.55) μm have been studied by photoluminescence (PL). By increasing temperature, we find that samples containing nitrogen a luminescence thermal stability and emission efficiency higher than of corresponding N-free heterostructures. The dependence PL line shape shows progressive carrier detrapping from localized to extended states as T is increased. Finally, extent shift free...

The electron effective mass, ${m}_{\mathrm{e}}$, has been determined by magnetophotoluminescence in as-grown and hydrogenated $\mathrm{Ga}{\mathrm{As}}_{1\ensuremath{-}x}{\mathrm{N}}_{x}$ samples for a wide range of nitrogen concentrations (from $x<0.01%$ to $x=1.78%$). A modified $\mathbf{k}\mathbf{∙}\mathbf{p}$ model, which takes into account hybridization effects between N cluster states the conduction band edge, reproduces quantitatively experimental ${m}_{\mathrm{e}}$ values up...

We investigate the electronic properties of GaAs1−xBix by photoluminescence at variable temperature (T=10–430K) and high magnetic field (B=0–30T). In GaAs0.981Bi0.019, localized state contribution to PL is dominant up 150K. At T=180K diamagnetic shift free-exciton states reveals a sizable increase in carrier effective mass with respect GaAs. Such an cannot be accounted for enhanced character valence band states, solely. Instead, it suggests that also Bloch conduction are heavily affected...

The effect of the order-disorder transition on band gap kesterite Cu2ZnSnS4, an interesting material for solar cells, has been investigated by optical spectroscopy. energy (Eg) decreases continuously with increasing annealing temperature, Ta, and reaches its minimum at Ta ∼ 273 °C. Eg is about 200 meV higher in most ordered state, than fully disordered state. Its value kinetic depend sample stoichiometry. A simplified model able to explain order degree stoichiometry effects developed....

Semiconductor nanowires (NWs) formed by non-nitride III–V compounds grow preferentially with wurtzite (WZ) lattice. This is contrary to bulk and two-dimensional layers of the same compounds, where only zincblende (ZB) observed. The absorption spectrum WZ materials differs largely from their ZB counterparts shows three transitions, referred as A, B, C in order increasing energy, involving minimum conduction band different critical points valence band. In this work, we determine temperature...

Heat management mechanisms play a pivotal role in driving the design of nanowire (NW)-based devices. In particular, rate at which charge carriers cool down after an external excitation is crucial for efficiency solar cells, lasers, and high-speed transistors. Here, we investigate thermalization properties photogenerated by continuous-wave (cw) photoluminescence (PL) InP GaAs NWs. A quantitative analysis PL spectra recorded up to 310 K shows that can thermalize temperature much higher than...

InAs nanowires (NWs) have been grown on semi-insulating (111)B substrates by metal-organic chemical vapor deposition catalyzed 50, 100, and 150 nm-sized Au particles. The pure wurtzite (WZ) phase of these NWs has attested high-resolution transmission electron microscopy selected area diffraction pattern measurements. Low temperature photoluminescence measurements provided unambiguous robust evidence a well resolved, isolated peak at 0.477 eV, namely 59 meV higher than the band gap ZB InAs....

Mechanical deformations and ensuing strain are routinely exploited to tune the band gap energy enhance functionalities of two-dimensional crystals. In this Letter, we show that leads also a strong modification exciton magnetic moment in WS_{2} monolayers. Zeeman-splitting measurements under fields up 28.5 T were performed on single, one-layer-thick microbubbles. The bubbles causes hybridization k-space direct indirect excitons resulting sizable decrease modulus g factor ground-state exciton....

Atomic hydrogen irradiation leads to striking effects on the electronic properties of ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{As}}_{1\ensuremath{-}y}{\mathrm{N}}_{y}/\mathrm{GaAs}$ single quantum wells as measured by photoluminescence spectroscopy. The ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{As}}_{1\ensuremath{-}y}{\mathrm{N}}_{y}$ band-gap energy blueshifts with increasing dose and finally saturates at value a corresponding reference sample without...

Capacitance–voltage characteristics have been measured at various frequencies and temperatures for structures containing a sheet of self-assembled InAs quantum dots in both n-GaAs p-GaAs matrices. Analysis the capacitance–voltage shows that deposition 1.7 ML forms with electron levels 80 meV below bottom GaAs conduction band two heavy-hole 100 170 above top valence band. The carrier energy agree very well recombination energies obtained from photoluminescence spectra.

The effect of atomic hydrogen on the electronic properties (InGa)(AsN)/GaAs single quantum wells (QWs) has been investigated by photoluminescence (PL) spectroscopy. For increasing dose, band gap material increases until it reaches value corresponding to a N-free reference QW. variation is accompanied an increase line width PL spectra and decrease efficiency. Annealing at 500 °C fully recovers sample had before hydrogenation. These results are accounted for formation N–H complexes, which...

We investigate the absorption properties of ensembles wurtzite (WZ) InP nanowires (NWs) by high-resolution polarization-resolved photoluminescence excitation (PLE) spectroscopy at T = 10 K. The degree linear polarization absorbed light, ρ(abs), resulting from PLE spectra is governed a competition between dielectric mismatch effect and WZ selection rules acting differently on different optical transitions. These two contributions are deconvoluted with help finite-difference time-domain...

Conversion of free-standing graphene into pure graphane─where each C atom is sp3 bound to a hydrogen atom─has not been achieved so far, in spite numerous experimental attempts. Here, we obtain an unprecedented level hydrogenation (≈90% bonds) by exposing fully nanoporous samples─constituted single few veils smoothly rippled graphene─to atomic ultrahigh vacuum. Such controlled high-quality and high-specific-area samples converts the original conductive wide gap semiconductor, with valence...

The electronic properties of ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{As}}_{1\ensuremath{-}y}{\mathrm{N}}_{y}/\mathrm{GaAs}$ single quantum wells have been investigated by photoluminescence and photoreflectance spectroscopy as a function temperature. introduction nitrogen leads to sizable slow down in the redshift ground state recombination energy with We explain observed effects terms an anticrossing between states conduction band (CB) edge N-induced localized level...