Picosecond dynamics of internal exciton transitions in CdSe nanorods

Cooke, David G.; Jepsen, Peter Uhd; Lek, Jun Yan; Lam, Yeng Ming; Sy, Fredrik; Dignam, Marc M.

doi:10.1103/physrevb.88.241307

Cited by 7 publications

(5 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[109] A much narrower excitonic-like resonance of electrons trapped at Ti ion donor states superimposed onto the response of confined charges was observed in TiO 2 nanotubes. Several excitonic transitions were resolved for example in CdSe nanorods (diameter 7 nm, length 70 nm) using multi-THz spectroscopy.…”

Section: Wwwadvopticalmatdementioning

confidence: 97%

Terahertz Spectroscopy of Nanomaterials: a Close Look at Charge‐Carrier Transport

Kužel

Němec

2019

Advanced Optical Materials

View full text Add to dashboard Cite

Transport of charges is a fundamental process in many high-tech applications including photovoltaic or optoelectronic devices, but also in more ordinary components such as unsophisticated wires and other circuitry. The development of nanotechnologies resulted in the fabrication of highly complex materials consisting of a large variety of nanosized elements, which inevitably involve a multitude of charge transport processes occurring on various time-and length-scales. Figure 1 summarizes the most common nanoelements with high application potential.For example, the electrodes employed in Grätzel solar cells [1] are composed of percolated networks of a huge number of metal oxide nanoparticles (top-left panel in Figure 1). Colloidal nanocrystals form the basis for thin film electronics and flexible electronic devices. [2] The synthetic approaches control their composition, size and electronic structure (energy levels, density of states within the bands and in the bandgap) and the charge-carrier transport. [2,3] Nanowires and nanotubes made of conventional semiconductors are quasi 1D systems combining Terahertz spectroscopy has been used for almost two decades for investigations of nanomaterials, including nanocrystals, nanoparticles, nanowires, nanotubes or 2D crystals. Its great importance stems from the fact that it is a noncontact method and, owing to its high frequency and broadband character, it is capable of characterizing charge transport properties within individual nano-objects but also among them. In addition, probing of photoinitiated ultrafast charge dynamics is possible thanks to the sub-picosecond time resolution. Despite this unprecedented potential, the interpretation of the measured terahertz conductivity spectra in many materials is still intensively debated. Herein is presented a review of the experiments performed on nanostructures of conventional semiconductors and on carbon nanomaterials (graphene and carbon nanotubes) during the past decade. The state of the art of the theoretical formalism is provided and discussed, including the intrinsic response, as well as the role of inherent heterogeneity and of the experimental conditions.

show abstract

Section: Wwwadvopticalmatdementioning

confidence: 97%

Terahertz Spectroscopy of Nanomaterials: a Close Look at Charge‐Carrier Transport

Kužel

Němec

2019

Advanced Optical Materials

View full text Add to dashboard Cite

show abstract

“…where α is the ratio between the domain size and the mean free path mfp [75]. Hence, while equation ( 10) is a solid phenomenological basis for characterization of the conductivity of extended graphene films [26] as well as other nanostructured conductors [76] and semiconductors [77][78][79][80], the Drude-Smith model represents a highly simplistic picture of the complex interaction between Dirac fermions and line-defects, and its impact on the AC conductivity. Further investigations into the validity range of the Drude-Smith model as well as more specific models taking disorder explicitly into account are certainly needed for a detailed understanding of conductivity dynamics in the presence of disorder in graphene.…”

Section: Ac Conductivity For Pristine and Structured Graphenementioning

confidence: 99%

Mapping the electrical properties of large-area graphene

et al. 2017

View full text Add to dashboard Cite

The significant progress in terms of fabricating large-area graphene films for transparent electrodes, barriers, electronics, telecommunication and other applications has not yet been accompanied by efficient methods for characterizing the electrical properties of large-area graphene. While in the early prototyping as well as research and development phases, electrical test devices created by conventional lithography have provided adequate insights, this approach is becoming increasingly problematic due to complications such as irreversible damage to the original graphene film, contamination, and a high measurement effort per device. In this topical review, we provide a comprehensive overview of the issues that need to be addressed by any large-area characterisation method for electrical key performance indicators, with emphasis on electrical uniformity and on how this can be used to provide a more accurate analysis of the graphene film. We review and compare three different, but complementary approaches that rely either on fixed contacts (dry laser lithography), movable contacts (micro four point probes) and non-contact (terahertz timedomain spectroscopy) between the probe and the graphene film, all of which have been optimized for maximal throughput and accuracy, and minimal damage to the graphene film. Of these three, the main emphasis is on THz time-domain spectroscopy, which is non-destructive, highly accurate and allows both conductivity, carrier density and carrier mobility to be mapped across arbitrarily large areas at rates that by far exceed any other known method. We also detail how the THz conductivity spectra give insights on the scattering mechanisms, and through that, the microstructure of graphene films subject to different growth and transfer processes. The perspectives for upscaling to realistic production environments are discussed. TOPICAL REVIEWOriginal content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence.

show abstract

“…In our experiment we use a double-modulation approach [15][16][17][18]30] with a specific modulation pattern. The first modulation channel at the frequency of f /3 is provided by an optical chopper, designed to transmit only one every third pump pulse as shown in Fig.…”

Section: Self-referenced Thz Spectroscopy With Abcd Detectionmentioning

confidence: 99%

“…Many reports exist to-date on THz generation using dual-color laser induced air-plasma, and on THz detection using air-biased coherent-detection (ABCD) [4][5][6][7][8][9][10][11]. Yet, the implementation of THz air-photonics in accurate ultra-broadband THz spectroscopy of materials has remained challenging, and only very few reports exist on that matter [12][13][14][15][16][17][18][19]. The reason is that while THz air-photonics offers unparalleled possibilities such as the direct access to the entire THz spectral range in a single measurement and a very high (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Consequently, the reflection geometry becomes a natural choice, as it allows one to utilize the full bandwidth of the THz pulse in the spectroscopic experiment. Yet to date it has only been rarely employed in transient THz measurements [15][16][17][18][19][21][22][23], since such a configuration poses additional challenges as described below.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Self-referenced ultra-broadband transient terahertz spectroscopy using air-photonics

D’Angelo¹,

Němec²,

Parekh³

et al. 2016

Opt. Express

View full text Add to dashboard Cite

Terahertz (THz) air-photonics employs nonlinear interactions of ultrashort laser pulses in air to generate and detect THz pulses. As air is virtually non-dispersive, the optical-THz phase matching condition is automatically met, thus permitting the generation and detection of ultra-broadband THz pulses covering the entire THz spectral range without any gaps. Air-photonics naturally offers unique opportunities for ultra-broadband transient THz spectroscopy, yet many critical challenges inherent to this technique must first be resolved. Here, we present explicit guidelines for ultra-broadband transient THz spectroscopy with air-photonics, including a novel method for self-referenced signal acquisition minimizing the phase error, and the numerically-accurate approach to the transient reflectance data analysis.

show abstract

Picosecond dynamics of internal exciton transitions in CdSe nanorods

Cited by 7 publications

References 30 publications

Terahertz Spectroscopy of Nanomaterials: a Close Look at Charge‐Carrier Transport

Terahertz Spectroscopy of Nanomaterials: a Close Look at Charge‐Carrier Transport

Mapping the electrical properties of large-area graphene

Self-referenced ultra-broadband transient terahertz spectroscopy using air-photonics

Contact Info

Product

Resources

About