Rapid Defrost Transparent Thin-Film Heater with Flexibility and Chemical Stability.

Zn-doped SnOx/Ag/Zn-doped SnOx(ZTO/Ag/ZTO) multilayer thin films fabricated on a polyethylene terephthalate (PET) substrate using an optimized N2-to-(Ar + O2) gas ratio are used for transparent thin-film heaters with high performance and chemical stability. The ZTO/Ag/ZTO-based multilayer thin film exhibits enhanced durability at high temperatures and humid environments by incorporating nitrogen. The bending test results-there was no significant change in the sheet resistance even after 10,000 bending cycles-highlight the mechanical flexibility of the ZTO/Ag/ZTO multilayer thin film. The ZTO/Ag/ZTO-based thin-film heater on PET, fabricated under optimized deposition gas conditions, exhibits a fast thermal response time of 30 s and a low driving voltage of 6 V to attain 100 °C. It also exhibits uniform heat distribution at saturated temperature and chemical stability after 100 heating-cooling cycles. Hence, the proposed ZTO/Ag/ZTO-based thin-film heater is applicable for use in front and rear window automobile and building applications.

Zn Vacancy Formation Energy and Diffusion Coefficient of CVT ZnO Crystals in the Sub-Surface Micron Region.

By using positron annihilation spectroscopy methods, we have experimentally demonstrated the creation of isolated zinc vacancy concentrations >1020 cm-3 in chemical vapor transport (CVT)-grown ZnO bulk single crystals. X-ray diffraction ω-rocking curve (XRC) shows the good quality of ZnO single crystal with (110) orientation. The depth analysis of Auger electron spectroscopy indicates the atomic concentrations of Zn and O are almost stoichiometric and constant throughout the measurement. Boltzmann statistics are applied to calculate the zinc vacancy formation energies (Ef) of ~1.3-1.52 eV in the sub-surface micron region. We have also applied Fick's 2nd law to calculate the zinc diffusion coefficient to be ~1.07 × 10-14 cm2/s at 1100 °C. The zinc vacancies began annealing out at 300 °C and, by heating in the air, were completely annealed out at 700 °C.

Critical increase in Na-doping facilitates acceptor band movements that yields ~180 meV shallow hole conduction in ZnO bulk crystals.

Stable p-type conduction in ZnO has been a long time obstacle in utilizing its full potential such as in opto-electronic devices. We designed a unique experimental set-up in the laboratory for high Na-doping by thermal diffusion in the bulk ZnO single crystals. SIMS measurement shows that Na concentration increases by 3 orders of magnitude, to ~3 × 1020 cm-3 as doping temperature increases to 1200 °C. Electronic infrared absorption was measured for Na-acceptors. Absorption bands were observed near (0.20-0.24) eV. Absorption bands blue shifted by 0.04 eV when doped at 1200 °C giving rise to shallow acceptor level. NaZn band movements as a function of doping temperature are also seen in Photoluminescence emission (PL), Photoluminescence excitation (PLE) and UV-Vis transmission measurements. Variable temperature Hall measurements show stable p-type conduction with hole binding energy ~0.18 eV in ZnO samples that were Na-doped at 1200 °C.