[19a-E307-1~10] 9.4 Thermoelectric conversion

▼ [19a-E307-9] Thermoelectric Transport in Atomic Layer Deposited Hf and Ti-doped ZnO Thin Films

〇(D)JenichiClairvaux Escubio Felizco¹, Taneli Juntunen², Mutsunori Uenuma¹, Jarkko Etula², Camilla Tossi², Yasuaki Ishikawa¹, Ilkka Tittonen², Yukiharu Uraoka¹ (1.NAIST, 2.Aalto Univ.)

Keywords:Doped ZnO, atomic layer deposition, thermoelectric

Atomic layer deposition (ALD) is an efficient technique to deposit doped ZnO thin films due to its precise layer by layer growth at a relatively low temperature. However, thermoelectric studies on doped ZnO thin films have been mostly related to the commonly used Al. Among possible alternative dopants, Ti is previously revealed to greatly increase the electron mobility of ZnO even at very small doping amounts, while Hf is less popular but potentially interesting due to its similar ionic radius with Zn. In this work, atomic layer deposited (ALD) Hf-doped and Ti-doped ZnO (HZO and TZO) thin films are investigated for the first time as novel thermoelectric materials. The TZO samples showed great improvement in σ compared to both pure ZnO and HZO samples throughout the temperature range. The maximum σ obtained was for 3% TZO at 298 S/cm, which was about a threefold increase from pure ZnO. This increase in σ, however, did not translate to a higher power factor (PF) due to generally lower S values. HZO samples, on the other hand, showed inferior σ but almost similar S with pure ZnO. This resulted to an almost similar behavior in PF for both dopants in all doping concentrations, wherein the maximum PFs for the both HZO and TZO samples were achieved at 3% doping concentration. Additionally, it is notable that the PF of 3% HZO exceeded that of pure ZnO at a measurement temperature of 180 ºC, reaching up to 157 uW/mK².