Transparent conducting oxides (TCOs) are widely used in applications from solar cells to light emitting diodes. Here, we show that the metal organic chemical vapor deposition (MOCVD)-grown, rock-salt CdZnO ternary, has excellent potential as a TCO. To assess this compound, we use a combination of infrared reflectance and ultraviolet-visible absorption spectroscopies, together with Hall effect, to determine its optical and electrical transport characteristics. It is found that the incorporation of Zn produces an increment of the electron concentration and mobility, yielding lower resistivities than those of CdO, with a minimum of 1.96×10−4 Ω·cm for a Zn content of 10%. Moreover, due to a combination of increasing bandgap energy and band filling, the absorption band-edge energy increases from 2.58 eV in CdO up to 2.89 eV for 15% Zn, yielding a largely enhanced transparency in the visible. The low required growth temperatures, together with the scalability of CVD deposition, provide an excellent ground for the integration of this TCO ternary alloy on foreign devices.
The development of new nanophotonic devices requires the understanding and modulation of the propagating surface plasmon and phonon modes arising in plasmonic and polar dielectric materials, respectively. Here we explore the CdZnO alloy as a plasmonic material, with a tunable plasma frequency and reduced losses compared to pure CdO. By means of attenuated total reflectance, we experimentally observe the hybridization of the surface plasmon polariton (SPP) with the surface phonon polariton (SPhP) in the air-CdZnO-sapphire three-layer system. We show how through the precise control of the CdZnO thickness, the resonance frequencies of the hybrid surface plasmonphonon polariton (SPPP) are tuned in the mid-infrared, and the nature of the hybrid mode turns from a plasmon-like behavior in the thicker films to a phonon-like behavior in the thinnest films. The presence of sapphire phonons not only allows the hybrid mode to be formed, but also improves its characteristics with respect to the bare SPP. The reduced damping of the phonon oscillators allows to reduce the losses of the hybrid mode, enhancing the propagation length above 500 m, one order of magnitude larger than that of typical SPPs, clearing the path for its application on emerging devices such as plasmonic waveguides.
HRXRD, SEM and TEM techniques were used to investigate crystallographic characteristics of Cd1−xZnxO films grown by MOCVD on r-plane sapphire in the transition process from the rock-salt to the wurtzite structure.
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