Abstract
Donor doped CdO thin films on c-plane sapphire are prepared by reactive co-sputtering from Cd-metal and Y-metal targets which are driven using pulsed-dc and RF power respectively. Intrinsic CdO exhibits a carrier density of 1.8 × 1019 cm−3 and a mobility of 330 cm2 V−1 s−1. By increasing the Y-flux, carrier density values can be increased smoothly and reproducibly to a maximum value of 3.3 × 1020 cm−3. Mobility increases with Y flux, and exhibits a broad plateau between approximately 5 × 1019 cm−3 and 2 × 1020 cm−3. Higher carrier concentrations produce a sharp drop in mobility. The increase in mobility is attributed to a reduction of intrinsic donors (i.e., oxygen vacancies) with increasing carrier density while the ultimate decrease in mobility results from a combination of factors including cadmium vacancies, reduced crystal quality, and smaller crystallite sizes, all of which accompany carrier density values greater than the mid 1020 cm−3 range. This work demonstrates that CdO thin films can be prepared by magnetron sputtering with transport properties and crystal quality that are comparable to those grown using molecular beam epitaxy.
Highlights
In recent years, conductive metal oxides have been increasingly investigated in the context of electronic, plasmonics, and optical technologies
Sachet et al demonstrated electron mobilities surpassing 500 cm[2] V 1 s 1 at carrier densities greater than 5 × 1019 cm 3 in Dy-doped CdO (CdO:Dy). These unique transport properties satisfy the criteria for mid-infrared spectrum plasmonics and overcome the optical losses seen in conventional conductors, such as noble metals.[5]
We demonstrate donor doped CdO films prepared by high-power impulse magnetron sputtering (HiPIMS) where it is possible to combine the material quality of MBE with the practicality and flexibility of a magnetron sputtering infrastructure
Summary
Conductive metal oxides have been increasingly investigated in the context of electronic, plasmonics, and optical technologies. The thin film community explored alternative process methods to manufacture doped cadmium oxide thin films, such as metalorganic vapor phase-epitaxy,[6] pulsed laser deposition,[7] colloidal nanocrystals,[8] and radio frequency sputtering.[9] there are no reports that duplicate the reported property trends of CdO:Dy in the low concentration regime (
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