Synthesis and Characteristics of Zn-Doped CuCrO2 Transparent Conductive Thin Films

Abstract

The effects of doping a p-type CuCrO2 film with zinc on its structural and optoelectronic properties were investigated by experiments using CuCr1−xZnxO2 thin films (x = 0, 0.025, 0.065, 0.085). An increase in the amount of zinc dopant in the thin films affected the lattice constant and increased its Gibbs free energy of phase transformation. Cross-sectional images of the CuCrO2 thin film samples exhibited a dense polygonal microstructure and a surface morphology with protruding nanoscale granules. With the increase in the amount of Zn dopant, the surface roughness decreased, thereby increasing the amount of incident photons as well as the visible-light transmittance and ultraviolet-light absorption of the thin films. With the zinc doping in the CuCrO2 thin films, the band gap increased from 3.09 to 3.11 eV. The substitution of Cr3+ with Zn2+ forms hole carriers in the crystals, which was demonstrated by X-ray photoelectron spectroscopy and Hall effect measurements. The conductivities and carrier concentrations of the Zn-doped CuCrO2 thin films were greater than those of undoped CuCrO2. The CuCr1−xZnxO2 film (x = 0.065) exhibited the best optoelectronic properties; its carrier concentration and resistivity were 1.88 × 1017 cm−3 and 3.82 Ωcm, respectively.

Highly Conductive and Visibly Transparent p-Type CuCrO2 Films by Ultrasonic Spray Pyrolysis

“…(e) Digital photograph of the CuCrO 2 coatings on glass substrates. (f) Average visible transmittance vs conductivity for the CuCrO 2 films prepared in this work alongside the current top performing CuCrO 2 films reported in the literature (from refs − , , , , − , , , , , ). Some of the literature values in this plot have been obtained by estimating the average transmittance in cases whereit was not clearly reported (these data values are also presented in Table S1).…”

“…Among the delafossite materials, CuCrO 2 has demonstrated very interesting optoelectronic properties with an average visible transmittance between 40 and 60%, a band gap in the 2.9–3.1 eV range, a high carrier concentration (up to 10 22 cm –3 ), and an electrical conductivity spanning several orders of magnitude from 10 –4 to 10 2 S cm –1 . − CuCrO 2 films have been fabricated through a variety of deposition methods including sputtering, pulsed laser deposition (PLD), molecular beam epitaxy (MBE), chemical vapor deposition (CVD), atomic layer deposition (ALD), and some wet-chemical methods including spin-coating and spray pyrolysis, achieving promising optoelectronic performance. The electrical properties of CuCrO 2 have also been further improved with strategies including extrinsic doping and non-stoichiometric formulations (i.e., the relative ratio between Cu and Cr). − Extrinsic dopant elements such as Ni, Zn, Ga, and in particular Mg have all been investigated to improve the electrical conductivity of the CuCrO 2 films. ,− At present, the highest recorded conductivity for a delafossite oxide belongs to Mg-doped CuCrO 2 thin films fabricated by vacuum-based depositions, with a maximum value of 220 S cm –1 . , …”

A review on the p-type transparent Cu–Cr–O delafossite materials

“…Lowers the conductivity [246] Zn Delafossite phase is maintained up to 3% content of Zn. Electrical conductivity increases with the Zn content [182,247] Ti A dilution of spin is observed. Magnetic properties are reported [248] 20% copper deficit when using spray pyrolysis and acetylacetonate precursors for copper and chromium in methanol.…”

Structural, Electronic Band Transition and Optoelectronic Properties of p-Type Transparent Conductive CuCr1–xNixO2 Semiconductor Films

“…As a result, doping methods are employed to improve its performance. There have been massive reports about CuCr 1– x N x O 2 (N = Mg, Mn, Zn, Al, Fe, , Ni, − and so on). In this series of doping, Ni atoms become ideal doped atoms due to their similar ionic radius (0.069 nm) to Cr and common positive divalent states.…”