Comparison of ALD grown AZO and ZnO Thin Film Heater Performances


Tugrul D., Doganay D., Ünalan H. E. , Imer M. B.

Materials Research Society (MRS) Fall 2021, Massachusetts, United States Of America, 6 - 08 December 2021, pp.1

  • Publication Type: Conference Paper / Summary Text
  • City: Massachusetts
  • Country: United States Of America
  • Page Numbers: pp.1
  • Middle East Technical University Affiliated: Yes

Abstract

: Ideal properties for transparent thin film heaters (TTFHs) can be summarized as low sheet resistance, high transmittance in visible range and high thermal stability. Generally, the material of choice converts the electrical energy into heat by “Joule Heating Mechanism”. Therefore, achieved maximum temperature is related with applied voltage, sheet resistance and heat loss. Also, uniformity of such material is important due to heating consistency and stability of the entire film. Oxide films grown by atomic layer deposition (ALD) has advantages such as high uniformity, thickness control at angstrom level and excellent step coverage due to its self-limiting growth mechanisms . Aluminum doped zinc oxide (AZO) thin films growth by ALD expected to show ideal properties for a TTFH. The studies suggest that the AZO thin films are suitable to be used as heater on different substrates with different production methods, reason being chemical and thermal stability of AZO . In this work, Al doped and undoped ZnO thin films grown by ALD were demonstrated as TTFH. The growth of the thin films were done on quartz substrates. Growth temperature for AZO was varied between 175 and 225 °C, Al doping was kept between 2-4 atomic percent, and thickness was kept constant as 100 nm for all samples. The varying temperature and doping levels were utilized to establish relation between doping concentration of aluminum on the performance of the thin films. The variables for ZnO were pulse/purge variations, and growth temperatures. Growth temperature for ZnO was in between 125 and 150 °C, and DI water pulse and Diethylzinc (DEZ- Zn(C H ) ) pulse was selected as 15 ms and purge time was kept at 10s. Different growth temperatures were chosen to vary stoichiometry of ZnO. Different temperatures were utilized to establish relation between ZnO thin films. Also, one of the main purposes was comparing Al dopped and undoped ZnO thin films with similar sheet resistance to display Al effect to TTFH performance such as maximum temperature and overall responsiveness. The lowest resistivity values achieved with AZO sample with 3.5 Al atomic percent as 3.3 10 Ω.cm while the each produced thin films transparency were over 85% in spectral range. The expected maximum temperature values were over 70°C with applied fairly low voltage (≤10V) with heating rate of 20 °C/s