Electrohydrodynamic processing is capable of synthesizing various materials in the form of porous/dense thin films, nanofibers, nanorods, nanobelts, and ribbons, which is highly favorable for functional oxides. The tailored microstructures and properties derived from electrohydrodynamic forming also give rise to new research interests on some classical oxides, such as transparent conducting oxides (TCOs). Here a case of feasible electrospray synthesis of classical ZnO is demonstrated with tailored p-type conductivity. Another p-type TCO, CuAlO2, was prepared by both electrospray and electrospinning methods and the processing-derived electrical and optical properties are demonstrated. The last part of the paper discusses some emerging applications especially for CuAlO2as potential nanobuilding blocks enabled by electrohydrodynamic processing.
AbstractWe propose and fabricate a heterojunction between Al-doped ZnO and (Mg, N)-doped CuCrO2 thin films using the sputtering deposition method. These materials possess wide bandgap that makes them transparent in the visible light but excellent UV-absorbers. On the other hand, the high conductivity of these materials, respectively as n-type and p-type transparent conducting oxides, facilitates the charge transport. We show that the p–n junction fabricated from these materials has the potential to act as a high-performance UV photovoltaic photodetector. The proposed structure, demonstrates fast responses in order of sub seconds, photosensitivity of ~ 41,000, responsivity of 1.645 mA/W, and a detectivity of 3.52 × 1012 Jones that are significantly improved in comparison with the Al-doped ZnO photoconductor. This excellent improvement is attributed to the capability of the photovoltaic configuration that creates a built-in voltage and facilitates the charge separation and collection rather than recombination in the photoconductor configuration.
ABSTRACTWe have developed the deposition, characterization and analysis tools necessary for a combinatorial approach to thin film metal oxides, with a special focus on transparent conducting oxides (TCOs). We are presently depositing compositionally graded libraries using mutli-target sputtering and CVD. The initial collection of characterization tools includes UV/VIS/NIR transmission/reflection, FTIR reflectance, Raman scattering, 4-point conductivity, thickness, xray diffraction and electron microprobe. In addition to allowing for a more complete empirical optimization of TCO properties, we expect to develop an improved basic understanding of TCOs, especially in the area of p-type TCOs. This paper provides an overview of our current combinatorial material science program as applied specifically to TCOs.
Epitaxial Bi_2Sr_2Co_2O_y thin films as a promising p-type transparent conducting oxides