Ultraviolet to far-infrared dielectric function of 
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-doped cadmium oxide thin films

Nolen, J. Ryan; Runnerstrom, Evan L.; Kelley, Kyle P.; Luk, Ting S.; Folland, Thomas G.; Cleri, Angela; Maria, Jon Paul; Caldwell, Joshua D.

doi:10.1103/physrevmaterials.4.025202

Cited by 24 publications

(28 citation statements)

References 80 publications

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“…TMM-simulated electron or hole injection cannot explain the observed asymmetric red-shift in ENZ absorption, regardless of whether the charge is injected into the full CdO layer or a thin slab near the interface. These TMM simulations incorporate rigorous relationships between the optical parameters (plasma frequency, scattering rate, high-frequency dielectric constant) and electronic parameters (electron number density, mobility, and effective mass), consistent with previous observations 34,35 .…”

Section: Remote Modulation Of the Enz Modesupporting

confidence: 80%

“…As this heated layer is now outof-equilibrium relative to the remainder of the CdO, electrons from the bulk of the film diffuse towards the hot CdO layer, which temporarily forms an accumulation layer near the Au/CdO interface and slightly decreases n e throughout the remainder of the CdO film. This increase in the local number density leads to a corresponding decrease in the high frequency permittivity, ε ∞ 34,35 .…”

Section: Remote Modulation Of the Enz Modementioning

confidence: 99%

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Long-lived modulation of plasmonic absorption by ballistic thermal injection

Tomko,

Runnerstrom,

Wang

et al. 2020

Preprint

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Energy and charge transfer across metal-semiconductor interfaces are the fundamental driving forces for a broad range of applications, such as computing, energy harvesting, and photodetection. However, the exact roles and physical separation of these two phenomena remains unclear, particularly in plasmonically-excited systems or cases of strong nonequillibrium. We report on a series of ultrafast plasmonic measurements that provide a direct measure of electronic distributions, both spatially and temporally, following optical excitation of a metal-semiconductor heterostructure. For the first time, we explicitly show that in cases of strong non-equilibrium, a novel energy transduction mechanism arises at the metal/semiconductor interface. We find that hot electrons in the metal contact transfer their energy to pre-existing electrons in the semiconductor, without transfer of charge. These experimental results findings are well-supported by both rigorous multilayer optical modeling and first-principle, ab initio calculations.

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Section: Remote Modulation Of the Enz Modesupporting

confidence: 80%

Section: Remote Modulation Of the Enz Modementioning

confidence: 99%

Long-lived modulation of plasmonic absorption by ballistic thermal injection

Tomko,

Runnerstrom,

Wang

et al. 2020

Preprint

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“…1a). This technique has been widely employed to determine the polaritonic properties of various 2D crystals due to its ability for spectroscopic characterization over a broad spectral range, with a high collection efficiency, and over a large sample area (see Methods for details) 39,52,53 .…”

Section: Fabrication Of In-plane Hyperbolic Polariton Tuner and Far-f...mentioning

confidence: 99%

In-plane hyperbolic polariton tuners in terahertz and long-wave infrared regimes

Huang

Folland

Sun

et al. 2022

Preprint

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Development of terahertz (THz) and long-wave infrared (LWIR) technologies is mainly bottlenecked by the limited intrinsic response of traditional materials. Hyperbolic phonon polaritons (HPhPs) of van der Waals semiconductors couple strongly with THz and LWIR radiation. However, the mismatch of photon−polariton momentum makes far-field excitation of HPhPs challenging. Here, we propose an In-Plane Hyperbolic Polariton Tuner and demonstrate a first device responding to direct far-field excitation and giving rise to a unique set of characteristic functions at far-field. Such a device is based on patterned surface directly written on van der Waals semiconductors; here α-MoO3. The resonances are found to strongly rely on in-plane hyperbolic polariton of patterned α-MoO3, exhibiting high quality factors up to 300, and to determine the characteristics of resultant tunable polarization and selection of the wavelength of reflection and transmission and regulation of output intensity. This is important to development of THz and LWIR miniaturized devices.

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“…Our TPP-WS-EMs are comprised of aperiodic DBRs (here, Ge and AlO x alternating layers) on thin (~500 nm) CdO films grown on sapphire substrates. The individual layer thicknesses and carrier density (thus the dielectric function 20 ) of CdO are designable parameters, written as a vector ( ⃗ ). This work employs an SGD-based inverse design technique to determine ⃗ , so that the difference between the absorption spectrum of designed structure (DS) and the target spectrum (TS) is minimized.…”

Section: Inverse Design Protocolmentioning

confidence: 99%

Deterministic Inverse Design of Lithography-Free, Wavelength-Selective Tamm Plasmon Thermal Emitters

Nolen

Nordlander

et al. 2021

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Wavelength-selective thermal emitters (WS-EMs) are of high interest due to the lack of cost-effective, narrow-band light sources in the mid- to long-wave infrared. Cost-effective WS-EMs can be realized via Tamm plasmon polariton (TPP) structures supported by distributed Bragg reflectors (DBRs) on metal layers, however, optimizing TPP-WS-EMs is challenging because of the large number of parameters to optimize. To address this challenge, we use stochastic gradient descent (SGD) to optimize TPP-WS-EMs composed of an aperiodic DBR deposited on doped cadmium oxide (CdO) plasmonic films. While the SGD-optimized, aperiodic DBR offers extensive spectral control, the material choice, i.e., plasma-frequency-tunable doped CdO, enables the design capabilities not accessible with noble metals. Here, the individual layer thickness and carrier density of CdO are optimized by our SGD inverse design strategy. The resultant experimental designs demonstrate TPP-WS-EMs exhibiting isolated, high-Q (narrow bandwidth), and structures featuring multiple emission bands for applications such as free-space communications and gas sensing. Furthermore, we illustrate the deterministic design capability within the infrared, such as user-designated Q-factors (28 − 10,127) at a desired frequency, multi-band emitters with user-defined Q, and the ability to directly match arbitrary chemical absorption spectra. Thus, the combination of our SGD inverse design and the broadly tunable plasma frequency of CdO enables lithography-free, CMOS-compatible, and wafer-scale solutions for WS-EMs with unprecedented spectral control.

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Ultraviolet to far-infrared dielectric function of n -doped cadmium oxide thin films

Cited by 24 publications

References 80 publications

Long-lived modulation of plasmonic absorption by ballistic thermal injection

Long-lived modulation of plasmonic absorption by ballistic thermal injection

In-plane hyperbolic polariton tuners in terahertz and long-wave infrared regimes

Deterministic Inverse Design of Lithography-Free, Wavelength-Selective Tamm Plasmon Thermal Emitters

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