Structural, electronic, and electrical properties of an Undoped n-Type CdO thin film with high electron concentration

Transparent conducting metal oxides (TCOs) combine the properties of optical transparency in the visible region with a high electrical conductivity. They are a critical component as the window electrode in liquid crystal and electroluminescent display devices, as well as in many designs of solar cells now under development. Sn-doped In2O3 is currently the most important TCO, but it suffers from some drawbacks. These include the high cost of indium, weak optical absorption in the blue-green region, as well as chemical instability that leads to corrosion phenomena in organic light-emitting devices. Indium tin oxide (ITO) films are also brittle and of relatively low durability. A number of other systems are therefore of interest as potential alternatives to Sn-doped In2O3. Recently, CdO has received considerable attention because of its high intrinsic dopability, which coupled with excellent Hall mobilities gives a high electrical conductivity. In the present study we have explored the structure, electronic, and electrical properties of CdO thin films prepared by a simple metalloorganic chemical vapor deposition route. The techniques employed include X-ray diffraction, atomic force microscopy, photoelectron spectroscopy, optical absorption spectroscopy, and luminescence measurements. Electrical properties were characterized by four-point probe and Hall effect measurements in the temperature range between 80 and 460 K. The electrical measurements demonstrated that the CdO thin films are degenerate semiconductors, with free-electron concentrations of around 7 x 10(20) cm(-3) provided by native donors.

Transparent conducting metal oxides (TCOs) combine the properties of optical transparency in the visible region with a high electrical conductivity. They are a critical component as the window electrode in liquid crystal and electroluminescent display devices, as well as in many designs of solar cells now under development. Sn-doped In2O3 is currently the most important TCO, but it suffers from some drawbacks. These include the high cost of indium, weak optical absorption in the blue-green region, as well as chemical instability that leads to corrosion phenomena in organic lightemitting devices. Indium tin oxide (ITO) films are also brittle and of relatively low durability. A number of other systems are therefore of interest as potential alternatives to Sn-doped In2O3. Recently, CdO has received considerable attention because of its high intrinsic dopability, which coupled with excellent Hall mobilities gives a high electrical conductivity. In the present study we have explored the structure, electronic, and electrical properties of CdO thin films prepared by a simple metalloorganic chemical vapor deposition route. The techniques employed include X-ray diffraction, atomic force microscopy, photoelectron spectroscopy, optical absorption spectroscopy, and luminescence measurements. Electrical properties were characterized by fourpoint probe and Hall effect measurements in the temperature range between 80 and 460 K. The electrical measurements demonstrated that the CdO thin films are degenerate semiconductors, with free-electron concentrations of around 7 × 1020 cm−3 provided by native donors.